Bismuth based semiconductor photocatalysts are being generated as promising materials for photocatalysis. In this work, hydrothermal methods have been utilized to synthesize a bismuth oxyiodide semiconductor with deposited Bi nanodots (Bi-BiOI), which could create oxygen defects and accelerate photoinduced charge migration simultaneously. The resulting Bi-BiOI strongly demonstrates the high photocatalytic performance for bisphenol A and methylene blue degradation under visible light. 86% of BPA was degraded after an irradiation time of 4 hours. Electrospray ionization mass spectrometry was employed to detect the evolution of intermediates formed during the decomposition process of bisphenol A, and the following results suggested complete bisphenol A mineralization. Additionally, electron paramagnetic resonance results revealed the production of free radicals and the presence of oxygen vacancies. Furthermore, a distinctively increased photocurrent response and photoluminescence decay dynamics demonstrate that the interface between the Bi nanodots and BiOI semiconductor promotes the separation and migration of photoinduced electron–hole pairs. The lower valence band value (2.57 eV) of Bi-BiOI presented a higher oxidation potential, thus the production of hydroxyl radicals could be promoted considerably. Based on the experimental results, factors such as oxygen vacancies, effective charge migration, suppressed photoinduced electron–hole pair recombination and a high Bi-BiOI oxidation potential would result in advanced free radical production capacity, thereby enhancing the photocatalytic efficiency. The findings of our work will contribute to the fabrication of metal nanodot deposited semiconductor photocatalysts and pave the way for the utilization of advanced oxidation technology.

Correction for ‘Bismuth oxyiodide coupled with bismuth nanodots for enhanced photocatalytic bisphenol A degradation: synergistic effects and mechanistic insight’ by Shunqin Luo et al., Nanoscale, 2017, DOI: 10.1039/c7nr05320g.

•Low friction and anti-wear polyimide composites were developed by adding La2O3 microparticles.•La2O3 microparticles incorporated with polyimide resulting in rough surface, layer structure and low surface energy.•Friction force and coefficient of friction were found to show a 70% reduction on La2O3- polyimide composites comparing with neat polyimide.•La2O3 microparticles significantly improved the anti-wear performances of polyimide.Rare earth oxide La2O3 microparticles-reinforced polyimide (PI) composites (La-PI-Cs) were fabricated, aiming to improve the tribological property of PI. Surface roughness, surface composition, bulk structure, friction force (Ff) and coefficient of friction (COF) at macro/micro preload, and anti-wear performances of La-PI-Cs were studied and compared with neat PI. With La2O3 microparticles, La-PI-Cs showed larger surface roughness, lower surface energy, and higher hydrophobicity than neat PI, and displayed beneficial layered structure different from the compact structure of PI. Owing to these advantages, La-PI-Cs were found to show a 70% reduction in Ff and COF, and a 30% reduction in wear rate, indicating significantly lowered friction and enhanced anti-wear properties after adding La2O3 microparticles. Our research findings demonstrated an easy and low cost method to fabricate polymer composites with low friction and high wear resistance, and help meet the demanding of polymer composites with high tribological performances in broaden applications.Download high-res image (126KB)Download full-size image

In this paper, ZrO2-SiC-Al2O3 ceramic was fabricated by as-prepared ZrO2-SiC powders and commercial α-Al2O3 powders, sintered at 1450 °C for 1 h. ZrO2-SiC composite powders were synthesized through carbothermal reduction with zircon as raw material and carbon black as the reductant. Through ZrO2-SiC-Al2O3 ceramic mechanical properties measurements it was indicated that this ceramic had excellent properties in both bending strength and hardness. In addition, ZrO2-SiC-Al2O3 ceramic abrasive wear property was measured. ZrO2-SiC-Al2O3 ceramic mass loss increased along with the increase in both wheel rate and applied load. The type of wear particles had an important effect on abrasive wear resistance. ZrO2-SiC-Al2O3 ceramic displayed excellent abrasive wear resistance in bentonite and quartz slurries in comparison with SiC slurry.

The (Y,Ce)2BaAl4SiO12 phosphor, a garnet-structured blue-to-yellow color convertor for WLED, exhibits an interesting “microcrystal-glass powder” feature, which can be regarded as the 4th form for phosphor, in addition to the “ceramic powder phosphor”, the “single crystal phosphor” and the “glass-ceramic phosphor”. The structure exhibits luminescent microcrystals embedding in non-luminescent glass matrix: the spherical crystals are mainly arranged around the glass phase forming a “necklace” pattern, while the individual crystals show a “core-shell” architecture regarding the luminescence intensity variation. Further combining the phase evolution evidence evaluated by Rietveld refinement, we propose the formation mechanism for such unique morphology/structure as a two-stage process, including an initial nucleation by solid state reaction and following liquid-assisted crystal growth, instead of a precipitation-crystallization process.

•A novel apatite-type Ca9La(PO4)5(GeO4)F2:Dy3+ phosphor has been synthesized.•Ca9La(PO4)5(GeO4)F2:Dy3+ is a promising white-emitting phosphor for LED.•The Ca9La(PO4)5(GeO4)F2:Dy3+ phosphor shows excellent thermal stability.A novel apatite structure phosphor Ca9La(PO4)5(GeO4)F2:Dy3+ (CLPGF:Dy3+) with a hexagonal lattice in the P63/m space group was synthesized via a facile solid state technique. The crystal and fine local structure as well as their photoluminescence properties were investigated in detail. The CLPGF:Dy3+ phosphor can absorb in the UV-vis spectral region of 290–475 nm and exhibit two intense emission bands centered at 485 and 580 nm, which ascribes to 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2 transitions of Dy3+, respectively. The concentration quenching of Dy3+ emission occurs via the energy transfer among the nearest-neighbor ions and the corresponding quenching mechanism was verified to be the dipole-dipole interaction. The quantum efficiencies of the phosphors were examined to be 72.9% and its luminescence intensity at 150 °C decreases to 93.8% and 98.6% of the initial value at room temperature, which corresponds to 4F9/2 to 6H15/2 transition and 4F9/2 to 6H13/2 transition of Dy3+ ions, respectively. Their interesting photoluminescence properties indicate that the CLPGF:Dy3+ phosphor is a promising white-emitting candidate for w-LEDs applications.

Er3+ / Yb3+ doped BaIn2O4 up-conversion (UC) phosphors are synthesized and their UC luminescent properties are characterized. BaIn2O4 has P21/c space group but Rietveld refinement suggests it has twice smaller cell parameter (a = 10.3975 Å, b = 5.8295 Å, c = 14.4457 Å) and volume than previous reported structure. Refinement also reveals Er3+/Yb3+ replaces In3+ ions in lattice because of the existence of InO6 octahedra. In these BaIn2O4 phosphors, co-doping with Yb3+ ions changes the predominant UC emission from green ( 2H11/2, 4S3/2 → 4I15/2 of Er3+) to red (about 665 nm, 4F9/2 → 4I15/2 of Er3+). By controlling of Er3+/Yb3+ concentrations, the BaIn2O4 phosphors have the potential of generating various UC spectra and color tunability. The pumping powers study shows two-photon process in these phosphors.

Er3+ and/or Yb3+ doped Sr2ScF7 up-conversion (UC) phosphors were synthesized, and the optimum doping concentrations of Yb3+ and Er3+ in the Sr2ScF7 host were found to be 20% mol and 7% mol, respectively. Under excitation of 980 nm laser, the UC spectra of the samples is composed of three green emission bands from 510 to 570 nm centered at 525, 543 and 551 nm and two red emission band from 640 to 690 nm with two peaks at 657 and 671 nm, which is attributed to the 2H11/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions of Er3+, respectively. The UC emission color of Er3+ can be tuned by adjusting the intensity ratio of red to green emission through manipulating the population of red and green emitting states.Download high-res image (165KB)Download full-size image

A series of novel luminescent emission-tunable phosphors Mg2La8(SiO4)6O2:Ce3+,Tb3+ (MLS:Ce3+,Tb3+) have been prepared by a solid-state reaction. The phase formation was firstly confirmed through X-ray diffraction technique and refined by the Rietveld method. The MLS:Ce3+,Tb3+ phosphors, which crystallized in apatite-type hexagonal phase, exhibited a broad excitation band ranging from 200 to 400 nm and several emission bands centered at 426 nm and 551 nm. Energy transfer from Ce3+ to Tb3+ ions via a dipole-dipole mechanism occurred in the as-synthesized phosphors upon ultraviolet (UV) excitation. The energy transfer efficiency increases with increasing doping content of Tb3+ ions, which was confirmed by the luminescence spectra and fluorescence decay curves of corresponding ions simultaneously. The energy transfer critical distance was calculated and evaluated by both the concentration quenching and spectral overlap methods. The chromaticity of emission-tunable phosphors was also characterized by the Commission International de l'éclairage (CIE) chromaticity indexes, and the color tone can be tuned from blue (0.179, 0.122) to green (0.267, 0.408) by controlling the ratio of Ce3+/Tb3+.Download high-res image (365KB)Download full-size image

•The paper presents an experimental study on lightweight wall material (LWM).•EG/paraffin composite is added into LWM with energy storage property.•LWM possesses of certain enthalpy value and better thermal conductivity.•EG/paraffin composite content affects thermal and mechanical properties of LWM.•LWM has adequate stability on mechanical and thermal property.Lightweight wall material (LWM) composited with EG/paraffin composite was prepared by experimental procedures of foaming, slip casting and constant temperature curing. The EG/paraffin composites were synthesized via vacuum impregnation method. The scanning electron microscope (SEM) analysis indicated that paraffin was sufficiently absorbed into the EG porous network and depicted no leakage even in the molten state. The X-ray diffractometer (XRD) and Fourier transformation infrared spectroscope (FT-IR) results revealed that paraffin and EG in the composite didn’t undergo chemical reactions but only physical combination. The compressive strength value of the sample reached 2.853 MPa, while bulk density reduced to 0.445 kg/m3. The differential scanning calorimeter (DSC) results revealed that the sample melts at 47.78 °C with a latent heat of 16.26 J/g and solidifies at 43.81 °C with a latent heat of 15.98 J/g. The sample with 15% EG/paraffin composites had adequate stability by contrasting mechanical property and DSC profiles before and after 200 times thermal cycles. Furthermore, the thermal conductivity of the LWM increased to 0.76 W (m K) when 20% EG/paraffin was added into the composite. This indicates that the prepared sample has a good thermal property. Hence, the LWM containing EG/paraffin composite would be useful as thermal energy storage material.

•The expanded vermiculite/carbon (EVC) was prepared by in-situ starch carbonization.•The EVC was a satisfactory SA supporting matrix.•The thermal conductivity of the SA/EVC ss-CPCMs was 0.52 W/(m K).•The SA/EVC ss-CPCMs has high enthalpy of phase change, and good thermal stabilities.Stearic acid (SA) and modified expanded vermiculite (EV) shape-stabilized composite phase change materials (ss-CPCMs) with enhanced thermal conductivity were prepared. EV was impregnated with a starch solution, and then a composite of EV and carbon (EVC) was obtained by carbonizing starch in-situ in the EV layers. 63.12 wt % of SA was retained in the SA/EVC ss-CPCMs without leakage. Scanning electron microscopy (SEM) images showed that the EVC with highly porous micro-pores acted as a good support matrix for absorbing molten SA. The thermal conductivity of the SA/EVC ss-CPCMs was 0.52 W/(m K), and this was an increase of 52.9% compared with that of the SA/EV ss-CPCMs. The results from Fourier transform infrared spectroscopy (FT-IR), Differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), and thermal cycling tests indicated that the prepared SA/EVC ss-CPCMs are a promising material for energy efficient buildings because of their optimum phase-change temperature, a high enthalpy of phase change, ideal thermal conductivity, and good chemical and thermal stability.

In this study, the fatty acid eutectics (capric acid (CA) and lauric acid (LA) eutectics) were impregnated into the expanded perlite (EP) and expanded vermiculite (EVM) to form the two kinds of composite phase change material (PCM). The chemical structure, crystalloid phase were determined by the Fourier transformation infrared spectroscope, X-ray diffractometer. The results show that the eutectics with the EP and EVM do not undergo a chemical reaction and only undergo a physical combination. The SEM results proved that eutectics are well adsorbed in the porous structure of the EP and EVM. The thermal properties were determined by the differential scanning calorimeter (DSC). The DSC result shows that the melting temperatures and latent heat values of the PCMs are in the range of about 21–23 °C and 81–117 J/g. The maximum impregnation ratio of fatty acid eutectics into EP and EVM were 82.93% and 57.48%. The thermal cycling test proves that the composites have good thermal reliability. TG analysis revealed that the composite PCMs had high thermal durability property above their working temperature ranges. Besides, thermal conductivity of the CA-LA/EP and CA-LA/EVM was increased approximately as 89.14% and 87.41% by adding 5 wt.% expanded graphite (EG). It is envisioned that the prepared shape-stabilized PCMs have considerable potential for developing their roles in thermal energy storage system.

•The thermal conductivity of PA-CNTs/EP FS-CPCMs5.27 was 0.516 W m−1 K−1..•57.96 wt.% PA could be retained in PA-CNTs/EP FS-CPCMs5.27 without leakage.•Thermal conductivity and Latent heats of PA-CNTs/EP FS-CPCMs maintained reasonable.•CNTs can effectively enhance the thermal conductivity of PA-CNTs/EP FS-CPCMs.In this study, the effect of the introduction of carbon nanotubes (CNTs) as a filler for enhancing the thermal conductivity of paraffin-carbon nanotubes/expanded perlite form-stable composite phase change materials (PA-CNTs/EP FS-CPCMs) was experimentally investigated. Four samples of PA-CNTs/EP FS-CPCMs with different CNT mass fractions were prepared by vacuum impregnation. Scanning electron microscopy was employed to investigate the morphology and microstructure of CNTs, EP, and PA-CNTs/EP FS-CPCMs. Differential scanning calorimetry was employed to examine the thermal properties of PA-CNTs/EP FS-CPCMs, and results indicated that the latent heat and phase-change temperatures of the PA-CNTs/EP FS-CPCMs slightly change with the CNTs mass fractions. The thermal conductivity of PA-CNTs/EP FS-CPCMs5.27 (0.516 W m−1 K−1) was 4.82 times that of PA-CNTs/EP FS-CPCMs0. The thermal storage and release properties of PA-CNTs/EP FS-CPCMs were significantly improved as compared with those of PA-CNTs/EP FS-CPCMs0. Results obtained from Fourier transform infrared spectroscopy, thermogravimetric analysis, and thermal cycling tests showed that PA-CNTs/EP FS-CPCMs exhibit good chemical and thermal stabilities. The as-prepared PA-CNTs/EP FS-CPCMs demonstrate considerable potential as thermal energy storage materials.

This paper reports the development of new phosphors using the chemical unit cosubstituting solid solution design strategy. Starting from Lu3Al5O12, the Al3+–Al3+ couple in respective octahedral and tetrahedral coordination was simultaneously substituted by a Mg2+–Si4+ pair forming the Lu3(Al2−xMgx)(Al3−xSix)O12:Ce3+ (x = 0.5–2.0) series; as a result, the CeO8 polyhedrons were compressed and the emission got red-shifted from green to yellow together with the broadening. The evolution of, the unit cell, the local structural geometry as well as the optical properties of Ce3+ in these garnet creations, in response to the gradual Mg–Si substitution for Al–Al, were studied by combined techniques of structural refinement and luminescence measurements. The new composition Lu2.97Ce0.03Mg0.5Al4Si0.5O12 was comprehensively evaluated regarding its potential application in blue LED-driven solid state white lighting: the maximum emission is at 550 nm under λex = 450 nm; the internal and external quantum efficiencies can reach 85% and 49%, respectively; a 1-phosphor-converted wLED lamp fabricated using the as-prepared phosphor exhibits the luminous efficacy of 105 lm W−1, the correlated color temperature of 6164 K and the color rendering index (Ra) of 75.6. The new solid solution composition series is open for further optimization to enhance the competence for commercial consideration.

New garnet phosphors, Lu3−xYxMgAl3SiO12:Ce3+ (x = 0–3), which can be efficiently excited by blue light and emit the yellow-orange light, were developed using the solid solution design strategy combining the chemical unit substitution and the cation substitution. Crystal structures of the four compounds were reported for the first time via the Rietveld refinement of their powder XRD patterns. All phosphors show the general cubic garnet structure with the space group Iad. The specific occupancy of Lu/Y, Al/Mg, Al/Si and O atoms in different positions was identified. The evolution of cell parameters and Y/Lu/Ce–O bond lengths were identified. Photoluminescence properties were evaluated on aspects of emission/excitation spectra, internal/external quantum efficiency and thermal emission stability. Under the 450 nm blue light excitation, the phosphors exhibit bright yellow color emission, peaking in the 575–597 nm spectral range. The internal and external quantum efficiency can reach 83% and 58%, respectively. The emission red-shift in response to the Y/Lu ratio variation was discussed in relation to the local structure evolution. The phosphors are relatively promising to act as wavelength converter of blue light in white light emitting diodes.

In this paper, a series of novel luminescent Sr1−xAl12O19:xEu2+ phosphors were synthesized by a high temperature solid-state reaction. The phase structure, photoluminescence (PL) properties, as well as the decay curves were investigated. The quenching concentration of Eu2+ in SrAl12O19 was about 0.15 (mol). Upon excitation at 378 nm, the composition-optimized Sr0.85Al12O19:0.15Eu2+ exhibited strong broad-band green emission at 530 nm with the CIE chromaticity (0.2917, 0.5736). The results indicate that Sr1−xAl12O19:xEu2+ phosphors have potential applications as green-emitting phosphors for UV-pumped white-light LEDs.

•Novel Li2Mg2 (WO4)3:Eu3+ phosphor was synthesized by solid state reaction.•The phosphors show dominant emission peak at 620 nm upon excitation at 398 nm.•The phosphors behave a relatively good thermal quenching effect.•CIE coordinates of the phosphor was measured as (0.678, 0.322).A series of novel Eu3+ doped tungstate Li2Mg2 (WO4)3 red phosphors were successfully synthesized by a solid-state reaction method. The phase structure, photoluminescence properties and thermal stability of the phosphor were investigated in detail. The Li2Mg2 (WO4)3:Eu3+ phosphors show dominant emission peak at 620 nm (5D0→7F2 transition) upon the strongest excitation at 398 nm (7F0→5L6 transition). The optimal doping concentration of Eu3+ is determined to be 0.06 mol in order to obtain the maximum emission intensity. The dependence of the emission intensity on temperature denominates that Li2Mg2 (WO4)3:Eu3+ phosphor has a relatively good thermal quenching effect. The Commission Internationale del’Eclairage coordinates was measured as (0.678, 0.322) with high color purity, being close to the National Television Standard Committee system standard for red chromaticity (0.670, 0.330). The above studies indicate that Li2Mg2 (WO4)3:Eu3+ is a promising candidate as the red phosphor for near ultraviolet-based white LEDs application.

A shape-stabilized composite phase change material (ss-CPCM) comprising polyethylene glycol (PEG) and porous carbon was prepared by absorbing PEG into porous carbon, assisted by ultrasound. In the composite, PEG served as a phase change material for thermal energy storage, and the porous carbon, which was prepared from fresh potato via freeze drying followed by heat treatment, was used as an absorbent that also acted as the supporting material. Various analytical techniques were used to investigate the chemical composition, microstructure, and thermal properties of the prepared PEG/porous carbon ss-CPCMs. Scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopic results indicated that PEG was well absorbed and encapsulated in the porous structure of the carbon and that there was no chemical reaction between them during the phase change process. The shape and exudation stability test results indicated that the PEG/porous carbon ss-CPCMs have excellent shape stability, compared to pristine PEG. The contact angle test suggested that the melting PEG has good level of wettability on the carbon so that melting PEG could be well protected from exudation in the porous carbon by surface tension effects, even if the temperature is higher than the melting point of PEG. Differential scanning calorimetric results showed that the PEG/porous carbon ss-CPCMs have considerable phase change enthalpies and thermal storage capabilities. In addition to this, the latent heats of ss-CPCMs increased with increasing contents of PEG in the composites, and the highest value was achieved when the amount of PEG was 50%. Moreover, the thermogravimetric analysis results showed that the composites had excellent thermal stabilities. Based on the above analyses, the prepared ss-CPCM with 50% PEG content proved to be a promising candidate for thermal energy storage applications.

•Use the Rietveld refinement analysis to verified phase purity.•A red shift of the emission peak was observed with introduction of Sr2+.•Red shift was explained from crystal structure by raise a three layer model.A series of apatite-type phosphors Ba4.97−xSrx(PO4)3Cl:Eu2+(x = 0, 0.5, 1.0, 1.5, 2.0) were synthesized by the high temperature solid-state reaction method, and its luminescence properties were investigated in detail. It can be found that a red shift of the emission peak wavelength emerged from 439 to 462 nm with the continuous introduction of Sr2+ into the crystal lattice which has been simulated by a crystal-field model. The red shift is explained by the distortion in the crystal structure through X-ray diffraction and the Rietveld refinement analysis. According to a recently raised structural model, Eu2+ ions are surrounded by O atoms, PO4 tetrahedrons and Ba/Sr ions. After introducing Sr2+ into the lattice, the interatomic distance between Ba/Sr atoms and Eu2+ was expected to become shorter, resulting in a distortion of the inner EuOn polyhedrons. Then the crystal field strength surrounding Eu2+ was increased, finally resulting in the red shift.A series of apatite isostructural Ba4.97−xSrx(PO4)3Cl:Eu2+(x = 0, 0.5, 1.0, 1.5, 2.0) phosphor were synthesized by the high temperature solid-state reaction method. A red shift of the emission peak located in the blue region from 439 to 462 nm was observed with the continuous introduction of Sr2+ into the crystal lattice. A distortion of the inner EuOn polyhedrons was caused due to Ba/Sr ions substituting for Ba ions forming EuOn–Ba/Sr emitting blocks. The crystal field strength surrounding Eu2+ was thus increased, finally resulting in tunable PL properties.

•WCB was a perfect carrier matrix to form-stable composite PCMs.•The preparation time of FS-CPCMs was shortened by super ultrasonic method.•Mechanism of preparing FS-CPCMs was systematically discussed.•Stability, latent heat, and thermal properties of FS-CPCMs were excellent.In this study, novel polyethylene glycol (PEG)/White Carbon Black (WCB) form-stable composite phase changes materials (FS-CPCMs) were prepared by super- ultrasound-assisted, which obviously decreases the reaction time. Test results showed that PEG does not easily leak from the fluffy network structure of WCB during solid-liquid phase transition. Results obtained from XRD and FTIR demonstrated that no new chemical bond is formed between PEG4000 and WCB. Results obtained from DSC and TGA analyses showed that FS-CPCMs exhibit excellent thermal stability and good form-stable performance. The phase change enthalpy of FS-CPCMs reached up to 101.1J/g, and the melting and solidifying times of FS-CPCMs were 34.43% and 30.51% less than that of pure PEG, respectively. The thermal conductivity data showed that WCB acted as the support material is very effective for enhancing the thermal conductivity of the FS-CPCMs. The FS-CPCMs thus prepared were safe, environmentally friendly, and cost-effective; hence, they can be used as potential building materials for the applications of thermal energy storage.The novel polyethylene glycol/White Carbon Black form-stable composite phase change materials have an optimum phase change temperature, an excellently high enthalpy of phase change, a perfect thermal stability, and the excellent heat storage/release rate.

•TiO2/g-C3N4 nanofibers were prepared by electrospinning method.•TiO2/g-C3N4 nanofibers with diameter of 100–200 nm.•The composite nanofibers displayed the best photocatalytic degradation on RhB, when the g-C3N4 content was 0.8 wt.%.•The heterojunction formed between TiO2 and g-C3N4 contributed to the improved separation of electron-hole pairs.TiO2/g-C3N4 nanofibers with diameter of 100–200 nm were prepared by electrospinning method after calcination at high temperature, using polyvinylpyrrolidone (PVP), Melamine (C3H6N6), Ti(OC4H9)4 as raw materials. The composite nanofibers were characterized by XRD, FT-IR, SEM, UV–vis and PL respectively. The effects of different g-C3N4 contents on structure and photocatalytic degradation of the composite nanofibers were investigated. The results indicated that with increasing g-C3N4 content, the diameter of the composite fibers increased and the morphology changed from uniform structure to a nonuniform one, containing beads. The composite nanofibers displayed the best photocatalytic degradation on RhB, when the g-C3N4 content was 0.8 wt%. The degree of degradation was up to 99% at the optimal conditions of 40 min. The degradation activity of the composite nanofibers on RhB, MB and MO was found to be higher than that of the TiO2 nanofibers.TiO2 can be excited by UV light and produce photogenerated electron-hole pairs. The effect of g-C3N4 and TiO2 lead to an enhanced photocatalytic activity.

•Novel BaMg2V2O8:Eu3+ phosphors are synthesized by solid-state reaction.•The luminescent properties are well characterized and studied.•The thermal stability and CIE coordinates are investigated in detail.Eu3+ doped BaMg2V2O8 (BMVO) phosphor was synthesized via a high temperature solid-state reaction method. When λex = 318 nm and Eu3+ was doped, the VO43− peak at 545 nm decreased, and a characteristic Eu3+ peak occurred together with a maximum at 620 nm. In conjunction with the decay curve, this indicates that the energy transfer from VO43− to Eu3+. Upon doping with Eu3+, the phosphor becomes color-tunable. In addition, changing the temperature between 25 and 200 °C, BMVO:0.05Eu3+ phosphor also becomes color-tunable. All results indicate that Eu3+ doped BaMg2V2O8 phosphor has many promising commercial applications.Download high-res image (116KB)Download full-size image

•Chromium (VI) is reduced to Cr particles by aluminothermic reaction.•The conversion ratio of Na2CrO4 to metallic Cr attained 96.16%.•The Al2O3–Cr composites are used for metal-ceramics application.•This work is a potential approach to remove chromium (VI) pollutant.Reduction of chromium (VI) from Na2CrO4 through aluminothermic reaction and fabrication of metal-ceramic materials from the reduction products have been investigated in this study. Na2CrO4 could be successfully reduced into micrometer-sized Cr particles in a flowing Ar atmosphere in presence of Al powder. The conversion ratio of Na2CrO4 to metallic Cr attained 96.16% efficiency. Al2O3–Cr metal-ceramic with different Cr content (5 wt%, 10 wt%, 15 wt%, 20 wt%) were further prepared from the reduction product Al2O3–Cr composite powder, and aluminum oxide nanopowder via pressure-less sintering. The phase composition, microstructure and mechanical properties of metal-ceramic composites were characterized to ensure the potential of the Al2O3–Cr composite powder to form ceramic materials. The highest relative density and bending strength can reach 93.4% and 205 MP, respectively. The results indicated that aluminothermic reduction of chromium (VI) for metal-ceramics application is a potential approach to remove chromium (VI) pollutant from the environment.

•Ag/AgBr/Bi5O7I composites were synthesized via a co-precipitation method.•The Ag/AgBr/Bi5O7I exhibited excellent photodegradation efficiencies for RhB.•Ag0 plays an important role in transformations of photogenerated electrons and holes.An Ag/AgBr/Bi5O7I heterojunction was developed using a simple in situ co-precipitation method. Ag/AgBr nanoparticles were tightly bound to Bi5O7I, improving charge transfer at the heterojunction interface. The photocatalytic activities of the Ag/AgBr/Bi5O7I composites were studied by monitoring the photodegradation of Rhodamine B (RhB) and through the generation of a transient photocurrent under visible-light irradiation (λ > 420 nm). The Ag/AgBr/Bi5O7I composites displayed enhanced photocatalytic activities compared to either pure Ag/AgBr or Bi5O7I. Charge carrier behavior was investigated using electrochemical impedance spectroscopy (EIS) which indicated the enhanced separation and transfer of photogenerated electrons and holes, thus giving to the higher photocatalytic activity. The high-performance semiconductor heterojunction developed in this work is a good candidate for photocatalytic application.A series of Ag/AgBr/Bi5O7I composites with heterostructures were synthesized via a co-precipitation method. The Ag/AgBr/Bi5O7I composites exhibited excellent photodegradation efficiencies for RhB under visible-light irradiation, which were far superior to that of Bi5O7I alone. The formation of the appropriate overlapping band energy levels is crucial for creating an effective heterojunction structure and enabling the efficient separation and transfer of photogenerated electrons and holes.

In this study, the effect of the LaMgAl11O19 content on the mechanical properties of pressureless sintered Al2O3–LaMgAl11O19 composites, including room-temperature fracture toughness and flexural strength from room temperature to 1400 °C, was systematically investigated. Results indicated that Al2O3–LaMgAl11O19 ceramics exhibit enhanced mechanical properties as compared with those of monolithic Al2O3 ceramics both at room and elevated temperatures, with the maximum fracture toughness and flexural strength values of 4.88 MPa m1/2 and 472.8 MPa at room temperature, respectively. The flexural strength of Al2O3–LaMgAl11O19 ceramics gradually decreased with increasing test temperature below 1000 °C and sharply decreased thereafter. The improved mechanical properties of Al2O3–LaMgAl11O19 composites at ambient temperature were primarily attributed to the combination of crack deflection and bridging of LaMgAl11O19 platelets, while under elevated temperatures, the presence of LaMgAl11O19 platelets also played a crucial role in effectively hindering the grain boundaries sliding, thereby endowing superior bending strength to the composites.

In this study, the Ba3Eu(PO4)3 and Sr3Eu(PO4)3 compounds were synthesized and the crystal structures were determined for the first time by Rietveld refinement using powder X-ray diffraction (XRD) patterns. Ba3Eu(PO4)3 crystallizes in cubic space group I3d, with cell parameters of a = 10.47996(9) Å, V = 1151.01(3) Å3 and Z = 4; Ba2+ and Eu3+ occupy the same site with partial occupancies of 3/4 and 1/4, respectively. Besides, in this structure, there exists two distorted kinds of the PO4 polyhedra orientation. Sr3Eu(PO4)3 is isostructural to Ba3Eu(PO4)3 and has much smaller cell parameters of a = 10.1203(2) Å, V = 1036.52(5) Å3. The bandgaps of Ba3Eu(PO4)3 and Sr3Eu(PO4)3 are determined to be 4.091 eV and 3.987 eV, respectively, based on the UV–Vis diffuse reflectance spectra. The photoluminescence measurements reveal that, upon 396 nm n-UV light excitation, Ba3Eu(PO4)3 and Sr3Eu(PO4)3 exhibit orange-red emission with two main peaks at 596 nm and prevailing 613 nm, corresponding to the 5D0 → 7F1 and 5D0 → 7F2 transitions of Eu3+, respectively. The dynamic disordering in the crystal structures contributes to the broadening of the luminescence spectra. The electronic structure of the phosphates was calculated by the first-principles method. The analysis elucidats that the band structures are mainly governed by the orbits of phosphorus, oxygen and europium, and the sharp peaks of the europium f-orbit occur at the top of the valence bands.

Large scale β-sialon nanobelts/nanowires and ZrN–sialon composite powders were prepared via aluminothermic reduction nitridation under different conditions with flowing N2. The phase composition, morphology, and microstructure of the as-prepared products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM/HRTEM), Fourier-transform infrared spectroscopy (FT-IR) and energy dispersive X-ray spectroscopy (EDS). The experiment results show that the phase compositions and the ratio of nanostructures to powder can be tailored by the experimental conditions. The formation of β-sialon nanostructures was dominated by a vapor–solid (VS) mechanism. The photoluminescence spectrum of the β-sialon nanostructures exhibits a special emission peak located in the violet–blue spectral range, making possible potential applications in blue-light emitting diodes and display devices. This process also provided a feasible way to prepare reinforcing β-sialon nanostructures in situ within the ZrN–sialon composite powders.

A series of luminescent phosphate phosphors Cs1−xMgPO4:xEu2+ were synthesized via a high temperature solid-state reaction. The phase structure and photoluminescence (PL) properties, as well as the PL thermal stability of Cs0.96MgPO4:0.04Eu2+ were investigated to characterize the resulting sample. The crystal structure and chemical composition of the Cs0.96MgPO4:0.04Eu2+ phosphor were analyzed based on the Rietveld refinements and the crystal chemistry rules, respectively. The optimum concentration of Eu2+ in the CsMgPO4 phosphor was about 4 mol% and the concentration quenching effect can be attributed to the dipole–dipole interaction. This phosphor shows a broad red emission band ranging from 500 to 800 nm under the 410 nm light excitation. The above results indicate that Cs1−xMgPO4:xEu2+ phosphors have potential applications for near UV-excited w-LEDs.

Herein, we report a facile template- and surfactant-free strategy for the fabrication of 3D hierarchically mesoporous Co3O4 urchins and bundles, which involves a subsequent heat treatment of the corresponding novel precursors at 400 °C in air for 4 h. The morphology evolution mechanism of the precursor was revealed through systematic time- and temperature-dependent experiments. The as-synthesized mesoporous Co3O4 urchins and bundles deliver an enhanced lithium storage capacity, good cycling stability and excellent rate capabilities (e.g., 781 mA h g−1 for Co3O4 urchins and 660 mA h g−1 for Co3O4 bundles at 2 A g−1), indicating their potential applications in high power lithium ion batteries. The improved electrochemical performance is mainly attributed to the 3D structure and numerous mesopores within the nanofibers and nanosheets, which can effectively enhance structural stability, provide efficient diffusion length for lithium ions and electrons, and buffer volume expansion during the Li+ insertion/extraction processes.

The effect of elevated temperature on solid particle impact erosion wear behavior of 5 mol% Yttria Stabilized Zirconia ceramics (5YSZ) was studied using corundum sand as solid impact particles, an impact angle of 90°, and an impact speed of 50–60 m/s. Moreover, the erosion wear mechanism of 5YSZ ceramics at different temperatures was discussed. The solid particle impact erosion wear rate of 5YSZ ceramics was increased from 0.10 mm3/g to 0.81 mm3/g when the temperature rose from room temperature to 1200 °C, and then decreased to 0.64 mm3/g at 1400 °C. The plastic deformation erosion mechanism of 5YSZ ceramics was observed from room temperature to 1400 °C, and the erosion wear mechanism of cracking in irregular crisscross patterns lead to the stepwise heightened flaky exfoliation of the material from 600 °C to 1200 °C, which became the main erosion wear mechanism. These results provide the theoretical base for extension of service life of 5YSZ ceramics by avoiding the conditions that lead to erosion wear mechanisms.

Bi2WO6:Er3+ with hierarchical flower-like microstructures were synthesized by a one-step hydrothermal method. The photocatalysts thus obtained were characterized in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), X-ray photoelectron spectroscopy (XPS) as well as photoluminescence (PL) measurements. Results obtained by XPS confirmed the presence of Er3+ dopants in Bi2WO6. Moreover, the results obtained from SEM have shown that doping with Er ions results in hierarchical flower-like microstructures of Bi2WO6. Under visible light irradiation, with an appropriate doping content, the photocatalysts exhibit significant improvement in the photocatalytic activity as the separation efficiency of the photogenerated electron–hole pairs is enhanced. Notably, the photocatalytic activity of 1.5% Bi2WO6:Er3+ is 3.69 times that of undoped Bi2WO6. The results indicate that an appropriate doping content can improve photocatalytic activity, caused by wider band gap, hierarchical flower-like microstructures, and defects generated by doping with Er3+, which in turn increase the separation efficiency of the photogenerated electron–hole pairs.

•Novel BiBa2V3O11: Sm3+/Eu3+ phosphors are synthesized by solid-state reaction.•The luminescent properties are well characterized and studied.•The thermal stability and CIE coordinates are investigated in detail.Novel rare-earth ions (Sm3+ or Eu3+) doped BiBa2V3O11 phosphors were synthesized by solid-state reaction method. BiBa2V3O11: Sm3+ phosphors emitted orange-red light under near-UV irradiation, and the strongest excitation and emission peaks were observed at 345 and 607 nm. Under the excitation of 345 nm, BiBa2V3O11: Eu3+ phosphors show the strongest emission peaks located at 622 nm corresponding to the electric dipole 5D0 → 7F2 transition. The critical quenching concentrations of Sm3+/Eu3+ in the BiBa2V3O11 lattice were 5 mol% and 8 mol%. The thermal stability of Eu3+ doped BiBa2V3O11 and CIE coordinates of BiBa2V3O11: Sm3+/Eu3+ phosphors were also investigated. The results indicate that these phosphors could be potential candidates for application in white LEDs.

The cation substitution-dependent phase transition was used as a strategy to discover new solid solution phosphors and to efficiently tune the luminescence property of divalent europium (Eu2+) in the M3(PO4)2:Eu2+ (M = Ca/Sr/Ba) quasi-binary sets. Several new phosphors including the greenish-white SrCa2(PO4)2:Eu2+, the yellow Sr2Ca(PO4)2:Eu2+, and the cyan Ba2Ca(PO4)2:Eu2+ were reported, and the drastic red shift of the emission toward the phase transition point was discussed. Different behavior of luminescence evolution in response to structural variation was verified among the three M3(PO4)2:Eu2+ joins. Sr3(PO4)2 and Ba3(PO4)2 form a continuous isostructural solid solution set in which Eu2+ exhibits a similar symmetric narrow-band blue emission centered at 416 nm, whereas Sr2+ substituting Ca2+ in Ca3(PO4)2 induces a composition-dependent phase transition and the peaking emission gets red shifted to 527 nm approaching the phase transition point. In the Ca3–xBax(PO4)2:Eu2+ set, the validity of crystallochemical design of phosphor between the phase transition boundary was further verified. This cation substitution strategy may assist in developing new phosphors with controllably tuned optical properties based on the phase transition.

Core–shell SiC/SiOx nanochain heterojunctions have been successfully synthesized on silicon substrate via a simplified thermal evaporation method at 1500 °C without using catalyst, template or flowing gases (Ar, CH4, N2, etc.). X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy combined with energy-dispersive X-ray spectroscopy, scanning transmission electron microscopy and Fourier-transform infrared spectroscopy are used to characterize the phase composition, morphology, and microstructure of the as-synthesized nanostructures. A combined vapor–solid growth and modulation procedure is proposed for the growth mode of the as-grown SiC/SiOx nanochains. The formation of SiOx beads not only relates to the Rayleigh instability and the poor wettability between SiC and SiOx, but also to the existence of a high density of stacking faults within SiC-core nanowires. The photoluminescence spectrum of the nanochains exhibits a significant blue shift, which can be highly valuable for future potential applications in blue-green emitting devices.

Cation substitution dependent tunable bimodal photoluminescence behavior was observed in the Ca3–xSrx(PO4)2:Eu2+ (0 ≤ x ≤ 2) solid solution phosphors. The Rietveld refinements verified the phase purity and whitlockite type crystal structure of the solid solutions. The tunable photoluminescence evolution was studied as a function of strontium content, over the composition range 0.1 ≤ x ≤ 2. In addition to the emission band peak at 416 nm in Ca3(PO4)2:Eu2+, the substitution of Ca2+ by Sr2+ induced the emerging broad-band peak at 493–532 nm. A dramatic red shift of the emission peak located in the green-yellow region was observed on an increase of x in the samples with 0.75 ≤ x ≤ 2.00. The two emission bands could be related to the EuOn–Ca9 and EuOn–Ca9–xSrx emitting blocks, respectively. The values for the two kinds of emitting blocks in the solid solutions can be fitted well with the observed intensity evolution of the two emission peaks.

New compound discovery is of interest in the field of inorganic solid-state chemistry. In this work, a whitlockite-type structure Sr1.75Ca1.25(PO4)2 newly found by composition design in the Sr3(PO4)2–Ca3(PO4)2 join was reported. Crystal structure and luminescence properties of Sr1.75Ca1.25(PO4)2:Eu2+ were investigated, and the yellow-emitting phosphor was further employed in fabricating near-ultraviolet-pumped white light-emitting diodes (w-LEDs). The structure and crystallographic site occupancy of Eu2+ in the host were identified via X-ray powder diffraction refinement using Rietveld method. The Sr1.75Ca1.25(PO4)2:Eu2+ phosphors absorb in the UV–vis spectral region of 250–430 nm and exhibit an intense asymmetric broadband emission peaking at 518 nm under λex = 365 nm which is ascribed to the 5d–4f allowed transition of Eu2+. The luminescence properties and mechanism are also investigated as a function of Eu2+ concentration. A white LED device which is obtained by combining a 370 nm UV chip with commercial blue phosphor and the present yellow phosphor has been fabricated and exhibit good application properties.

•Si3N4 powder was synthesized from silica fume by carbothermal reduction nitridation.•Synthesis of Si3N4 was successfully achieved at temperatures as low as 1400 °C.•α/β-Si3N4 relative contents were tailored by adjusting temperature and carbon addition.Silicon nitride (Si3N4) powder with tunable α/β-Si3N4 relative contents was synthesized from waste silica fume using carbothermal reduction nitridation (CRN) at a relatively low temperature range of 1400–1500 °C. The effects of the carbon source, CRN temperature and raw materials ratio (Carbon-to-Silica fume) on phase assembly and micro-morphology of the products were investigated. Fabrication of α-Si3N4/β-Si3N4 from waste silica fume by CRN was achieved at temperatures as low as 1400 °C. Carbon black was found to be more suitable than coke and graphite for use as the reductant. Elevated temperature was beneficial for the formation of β-Si3N4, whilst excessive carbon black promoted the formation of α-Si3N4. Thus, the α-Si3N4/β-Si3N4 relative contents could be effectively tailored by adjusting the CRN temperature and carbon concentration of the initial mixtures. In addition, the bi-modal crystals of the whiskers and the short columns strongly influenced the morphologies of the product.

In this work, hierarchical peony-like FeCO3 structures of 3–5 μm diameter assembled from nanosheet layers were successfully prepared through a facile and well controlled hydrothermal method in the presence of an anionic surfactant sodium dodecyl sulfate (SDS). The factors influencing the morphology of the hierarchical FeCO3 structures were investigated. Hierarchical peony-like α-Fe2O3 structures assembled from nanoparticles were also fabricated by a thermal treatment of the as-obtained FeCO3 at 700 °C for 3 h in air. Tested as anode materials of Li-ion batteries, the hierarchical porous peony-like α-Fe2O3 structures exhibited an excellent reversible capacity of 1721 mA h g−1 at a current density of 50 mA g−1 and a high cyclic stability at 100 mA h g−1 over 30 cycles. These results demonstrate the hierarchical porous α-Fe2O3 is a promising anode candidate for lithium ion batteries.

JEM-phase Sialon (LnSi6−zAl1+zOzN10−z) was revealed to have limited z values. To keep the structure stability, substitution of the Si–N bond by the Al–O bond is very restricted and lanthanide-dependent (La → Sm). The z values of La-, Nd- and Sm-doped JEM-phase Sialons are ∼1.0, ∼0.6 and 0.4–0.2, respectively.

SiC@SiO2 nanowires were synthesized on a Si substrate by thermal evaporation method with an iron nitrate catalyst. The as-grown nanowires were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and photoluminescence spectroscopy at room temperature. Characterization indicated that the nanowires were composed of a crystalline SiC core with a thin amorphous SiO2 shell. The typical SiC core diameter was 50–100 nm, whereas the SiO2 shell thickness was 5–10 nm and they had a length of several hundreds of micrometers. A combined vapor–liquid–solid (VLS) base-growth and vapor–solid (VS) tip-growth mechanism is proposed for the growth mode of the as-grown SiC@SiO2 nanowires. The intensive blue-green emission properties of the core-shell SiC-SiO2 nanowires are of significant interest for their potential blue-green emitting device applications.

In this paper, a porous Sialon polytypoid material with multilayered structure was in situ synthesized at 1700 °C for 3 h in a nitrogen atmosphere via a nitriding process. The plate-like Sialon grains were observed using a scanning electron microscope (SEM), and the chemical composition, structure, chemical state and optical absorption of this material were characterized by energy dispersive X-ray spectroscopy (EDX), synchrotron X-ray diffraction (SXRD), X-ray photoelectron spectroscopy (XPS), and UV-vis diffuse reflectance spectroscopy (DRS). There are four layers with two ranges of grain sizes. The grains with sizes of 18–35 μm are in the inner layer (layer-4) and light-grey, while those grains with bigger sizes of 60–80 μm are present in the outer layers in green colour. These two types of grains have a slight difference in chemical composition, i.e. (La,Sm)0.1Si8Al14O5N21.1 and (La,Sm)0.33Si6Al12O1N21, respectively. They are polytypoids with different structures, which precipitated from the lanthanide-rich Sialon glass. The chemical states of the elements were different as indicated from XPS data. It is believed that the colour and size differences within layers resulted from the intrinsic differences of chemical composition, structure and chemical state of the two types of grains. This porous ceramic might be of potential applications in water treatment, building and automotive industries as a functionally gradient material (FGM) or ceramic filter.

α-Si3N4 nanobelts were grown on a graphitic carbon felt via an improved Ni-catalyzed chemical vapor deposition (CVD) process. The as-prepared nanobelts were up to several millimeters long and 300–1200 nm wide exhibiting a unimodal diameter distribution with peak range at 500–600 nm. Ni originally mixed with Si partially evaporated and then condensed on the carbon felt surface, forming catalytically active centers which absorbed gaseous Si and N and accelerated the growth of α-Si3N4 nanobelts. The formation process is considered to be co-dominated by a vapour–liquid–solid (VLS) base-growth mechanism and a vapour–solid (VS) tip-growth mechanism. The former was responsible for the initial nucleation and the proto-nanobelt formation and successive base-growth along the [101] direction of α-Si3N4, and the latter additionally contributed the growth at tips. The formation of α-Si3N4 nanobelts instead of nanowires is attributed to the anisotropic growth in the width and thickness directions, dictated by the liquid Ni catalyst droplets, in particular, in the initial proto-nanobelt formation stage. The room-temperature photoluminescence spectrum showed that the as-synthesized α-Si3N4 nanobelts had a strong emission with two maximum peaks at 416 nm (2.98 eV) and 436 nm (2.84 eV) located in the violet-blue spectral range, making it a potential material for applications in LED and optoelectronic nanodevices.

Ultralong single crystal Sialon nanobelts were prepared on a graphite cover coated with Ni(NO3)2 by facile thermal chemical vapor deposition reactions of Si, Al, and Al2O3 with flowing N2 at 1450 °C. The as-synthesized Sialon nanobelts were up to several millimeters long and several hundred nanometers wide, and they had width/thickness ratios of 5–15. Their growth process was codominated by a Ni-catalytic vapor–liquid–solid (VLS) base-growth mechanism and a vapor–solid (VS) tip-growth mechanism. The former was responsible for the initial nucleation and proto-nanobelt formation of Sialon and the subsequent growth along the [100] direction, and the latter additionally contributed the growth at tips. The room-temperature photoluminescence (PL) spectrum showed that the as-synthesized Sialon nanobelts had a special emission with two maximum peaks at 409 nm (3.03 eV) and 428 nm (2.90 eV) located in the violet-blue spectral range, making possible potential applications in LED and optoelectronic nanodevices.

•[SiO4] and [ZrO8] in zircon were separated by carbothermal reduction–nitridation.•[SiO4] was mutated to columnar β-Si3N4 and [ZrO8] was changed into granular ZrN.•Quartz was changed into columnar and acicular β-Si3N4.•Synthesis of ZrN–Si3N4 composite would lead to value-added use for zircon and quartz.ZrN–Si3N4 composite powders were synthesised from natural zircon and quartz via carbothermal reduction and nitridation reaction. The effects of various raw material compositions and heating temperatures on phase transformation and product morphologies under flowing nitrogen atmosphere were investigated by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The phase equilibrium relationships of the ZrO2–SiO2–C–N2 system at different heating temperatures were also investigated based on the thermodynamic analysis. Products with different phase compositions and morphologies were obtained at different conditions. The products were composed of ZrN, β-Si3N4 and a small amount of c-ZrO2 by carbothermal reduction and nitridation of zircon with less than 20 wt.% quartz. With 30 wt.% quartz, granular ZrN as well as columnar and acicular β-Si3N4 were detected in the products. With 40 wt.% or 50 wt.% quartz, the products consisted of ZrN, β-Si3N4, Si2N2O, c-ZrO2 and m-ZrO2. The optimum quartz content for synthesizing ZrN–Si3N4 composite powders was 30 wt.%. At heating temperatures below 1600 °C, the products were composed of ZrN, β-Si3N4, β-SiC, Si2N2O, m-ZrO2 and c-ZrO2.

Fe–Sialon ceramic matrix composite has been newly developed from ferro-silicon alloy and commercial-grade industrial alumina powders by reaction sintering under a nitrogen atmosphere. The phase composition, mechanical properties and impact erosion wear behavior were investigated. The solid particle erosion tests have been conducted at elevated temperatures ranging from 25 °C to 1200 °C. Sharp SiC particles between 325 and 830 μm in diameter were employed as impact abrasives. The results showed that Fe–Sialon ceramic consisted of β-Sialon and Fe3Si phases. The Z value of the as-formed β-Sialon varied from 0 to 3.2 with increasing the alumina content in the starting powders. The bending strength and Rockwell hardness gradually increased with raising the alumina addition. The erosion rate of Fe–Sialon ceramic is highly dependent on the testing temperature. The minor erosion took place at room temperature or 1200 °C, while the major erosion occurred at 600–1000 °C. Fe–Sialon composites showed better erosion wear resistance than the control material of alumina ceramic at 1200 °C, although having much lower density and slightly lower bending strength.

Dielectric constant discrepancy of parallel and vertical to Z axis of tourmaline (Yunnan, China) can be ascribed to chemical composition, space-charge polarization, and crystal structure. Cations at Y sites of the crystal structure contribute most to dielectric properties. The variations in dielectric properties might be attributed to crystal orientation.

Ultra-long single crystal α-Si3N4 nanobelts were prepared by thermal chemical vapour deposition (CVD) method. Silicon vapour from the original solid silicon raw material was allowed to react with flowing nitrogen at 1450 °C on the carbon felt deposited with Ni(NO3)2. The as-prepared α-Si3N4 nanobelts were 40–60 nm thick, 200–300 nm wide, and up to several millimetres long. Their growth process was governed by the VLS base-growth and the VS tip-growth mechanisms. The former was responsible for the initial nucleation and proto-nanobelt (template) formation of α-Si3N4 and the subsequent growth along the [101] or [100] direction, and the latter for the additional growth at the tips. The synergistic function from these two growth mechanisms resulted in the formation of a large quantity of ultra-long α-Si3N4 nanobelts. An intense violet–blue visible photoluminescence (PL) of the as-synthesized α-Si3N4 nanobelts was observed at room temperature, which could be highly valuable for the future potential applications in optoelectronic nanodevices.

Solid particle erosion tests have been conducted on three different alumina-based refractories at elevated temperatures up to 1400 °C, using sharp SiC particles between 325 and 830 μm in diameter. The impact speed is 50 m/s and the impact angle is varied between 30° and 90°. The objective of this study is to ascertain the effects of temperature and impact angle on the erosion resistance of alumina refractories. The experimental results reveal that the alumina-based refractories, in general, exhibit increasing erosion resistance with increasing temperature and decreasing impact angle, with the minimum erosion rate at 1200 °C and 30° impact angle. Chrome corundum refractory brick is the most resistant to vertical erosion, due to its highest alumina content, and associated hardness and density, as well as strongly bonded aggregate and binder phase. The primary material removal mechanisms are fracture and chipping of binder phase and aggregate, as well as aggregate pull-out.

Aluminium boron carbide (Al8B4C7) ceramic powder was synthesized via a solid state reaction method using Al, B4C and graphite powders as raw materials. The effects of synthesis temperature, carbon source (graphite and coke powder) and raw materials ratio on the phase transformation and micro-morphology of Al8B4C7 were investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that the optimized process for preparing the Al8B4C7 was 3 h sintering at 1600 °C in flowing argon atmosphere. Graphite was more appropriate than coke powder and carbon black as carbon source for synthesizing pure Al8B4C7, and 10 mol% excess of graphite resulted in higher purity of Al8B4C7. The stoichiometric amount of aluminium was essential for obtaining pure Al8B4C7, because second phase-Al4C3 would occur if excessive aluminium was used.In this study, the preparation method and the phase transformation behaviour of Al8B4C7 from Al/B4C/C starting mixtures were investigated. And the effects of extrinsic factor (synthesis temperature) and intrinsic factors (carbon source and raw materials ratio) on the formation of Al8B4C7 ceramic powders were also studied.Highlights► Al8B4C7 powders were synthesized through solid state reaction in argon atmosphere. ► Graphite is more suitable as carbon source than coke powder. ► Adding 10 mol% excess of graphite can prompt the synthesis of Al8B4C7 materials. ► The whole synthesis process is simple, convenient, fast and low-cost.

Zircon ore carbothermal reduction with yttria addition has been carried out. The influences of heating temperature and yttria addition on the phase transformations of zirconia from zircon ore by carbothermal reduction have been investigated in detail. The phase transformations of zirconia from zircon ore by carbothermal reduction were monitored by X-ray diffraction. The microstructure and micro-area chemical analysis of the products were characterized by scanning electron microscopy and energy dispersive spectrometer. The chemical states of Zr 3d, Y 3d and O 1s presented in the products of zircon carbothermal reduction with 10 wt% yttria addition were investigated by X-ray photoelectron spectroscopy. The results showed that the optimized heating temperature of zircon carbothermal reduction with no addition was 1600 °C, and the main phase of the products consists of m-ZrO2, c-ZrO2, ZrC and β-SiC. Yttria addition could be introduced into zirconia lattice and caused it to form Y2O3 stabilized zirconia. Zirconia in the products would be turned into partially stabilized zirconia with yttria addition from 1 wt% to 5 wt% while it would exist in the form of fully stabilized zirconia with over 8 wt% yttria addition.Graphical abstractHighlights► We discussed the phase transformations of zirconia which prepared from zircon ore. ► Yttria could be introduced into zirconia by zircon ore carbothermal reduction. ► YSZ, including PSZ and FSZ, could be prepared directly from natural zircon ore.

Single crystals of JEM-phase NdSi6−zAl1+zOzN10−z were successfully prepared from starting powders of Si3N4, AlN and Nd2O3 at 1700 °C for 3 h under nitrogen atmosphere. The z value of Nd-doped JEM-phase was determined to be 0.4 via determination of oxygen and nitrogen by elemental analysis. This result may be beneficial for overcoming the difficulty on preparation of single-phase JEM-phase Sialon materials and further characterization on their properties. The detailed crystal structure of Nd-Sialon was solved on the basis of single-crystal X-ray diffraction data for the first time. The space group is Pbcn (no. 60); a = 9.3060(6) Å, b = 9.7224(6) Å, c = 8.8777(5) Å; Z = 4; V = 803.22(8) Å3; Dc = 3.971 g cm−3; R1 = 0.0297 and wR2 = 0.0739 for all reflections refined against F2, with GooF value of 1.031.

A sol–gel route was developed to prepare pure ultrafine LiTaO3 powders using Ta2O5, Li2CO3, citric acid (CA) as chelating agent, ethylene glycol (EG) as esterification agent and polyethylene glycol (PEG) as dispersant. The effects of pH value and heat treatment temperature of powder precursor on the synthesis of LiTaO3 powders were investigated. The phase content and morphology of the final product were evaluated by XRD, SEM and TEM. A transparent gel was produced when heating a mixed-solution of CA, EG, Li and Ta ions with a molar ratio of [CA]:[EG]:[Li]:[Ta] = 3.0:6.0:1.0:1.0 and 2‰ PEG additions with a pH value of 7 at water bath temperature of 80 °C. The results showed that single phase LiTaO3 powders with average particle sizes of nanometers were produced after heat treatment of the powder precursor at 650, 700, 800, and 900 °C respectively for 2 h.

Nd-Sialon microcrystals with a novel orthogonal array morphology were developed by inducing catalysis of Fe for the first time, via a combination of vapor−liquid−solid (VLS) and vapor−solid (VS) growth mechanisms. The chemical composition of Nd-Sialon crystals was determined to be NdSi5.4Al1.6O0.6N9.4. The morphology of the tips strongly depended on the relative position of the liquid droplet to the crystal. Furthermore, the crystal growth process of Nd-Sialon microcrystals with the novel morphology was discussed. The Nd-Sialon single crystal shows UV-to-blue emission when it is excited by a wavelength of 325 nm. Nd-Sialon is envisioned to have potential in many functional applications, such as white LEDs, detector arrays, MEMS, and optical components. This work shines a light on the growth of Nd-Sialon single crystals for potential laser application.

Lauric acid(LA)/expanded vermiculite (EVM) form-stable phase change materials were synthesized via vacuum impregnation method. In the composites, lauric acid was utilized as a thermal energy storage material and the expanded vermiculite behaved as the supporting material. XRD and FT-IR results demonstrate that lauric acid and expanded vermiculite in the composite do not undergo a chemical reaction and only undergo a physical combination. Microstructural analysis indicates that lauric acid is sufficiently absorbed in the expanded vermiculite porous network, while displaying negligible leakage even under the molten state. According to DSC results, the 70 wt.% LA/EVM sample melts at 41.88 °C with a latent heat of 126.8 J/g and solidifies at 39.89 °C with a latent heat of 125.6 J/g. Thermal cycling measurements show that the form-stable composite PCM has adequate stability even after being subjected to 200 melting/freezing cycles. Furthermore, the thermal conductivity of the composite PCM increased by approximately 78% with the addition of 10 wt.% expanded graphite (EG). Thus, the form-stable composite PCM is a suitable option for thermal energy storage for building and solar heating system applications.

•We prepared β-SiC nanowires by a simplified CVD method without using catalyst and flowing gases.•The synthesis technique can be easily controlled and utilized.•The growth mechanism for the SiC nanowires is proposed.•This study can be helpful in designing and preparing SiC related nanostructures.β-SiC nanowires were synthesized by using an improved simple and low-cost thermal evaporation process at 1500 °C, without argon protect and catalyst assistant. The process simplifies the chemical vapor deposition method, which makes it easier to operate and industrialize. X-ray diffraction, Field emission scanning electron microscopy, high-resolution transmission electron microscopy and energy dispersive spectrum were employed to characterize the as-synthesized products. The β-SiC nanowires are about 50–100 nm in diameter, up to several micrometers long and usually grow along [111] direction with a thin oxide shell. A vapor–solid growth mechanism of the nanowires is proposed.

In this study, the Ba3Eu(PO4)3 and Sr3Eu(PO4)3 compounds were synthesized and the crystal structures were determined for the first time by Rietveld refinement using powder X-ray diffraction (XRD) patterns. Ba3Eu(PO4)3 crystallizes in cubic space group I3d, with cell parameters of a = 10.47996(9) Å, V = 1151.01(3) Å3 and Z = 4; Ba2+ and Eu3+ occupy the same site with partial occupancies of 3/4 and 1/4, respectively. Besides, in this structure, there exists two distorted kinds of the PO4 polyhedra orientation. Sr3Eu(PO4)3 is isostructural to Ba3Eu(PO4)3 and has much smaller cell parameters of a = 10.1203(2) Å, V = 1036.52(5) Å3. The bandgaps of Ba3Eu(PO4)3 and Sr3Eu(PO4)3 are determined to be 4.091 eV and 3.987 eV, respectively, based on the UV–Vis diffuse reflectance spectra. The photoluminescence measurements reveal that, upon 396 nm n-UV light excitation, Ba3Eu(PO4)3 and Sr3Eu(PO4)3 exhibit orange-red emission with two main peaks at 596 nm and prevailing 613 nm, corresponding to the 5D0 → 7F1 and 5D0 → 7F2 transitions of Eu3+, respectively. The dynamic disordering in the crystal structures contributes to the broadening of the luminescence spectra. The electronic structure of the phosphates was calculated by the first-principles method. The analysis elucidats that the band structures are mainly governed by the orbits of phosphorus, oxygen and europium, and the sharp peaks of the europium f-orbit occur at the top of the valence bands.

New garnet phosphors, Lu3−xYxMgAl3SiO12:Ce3+ (x = 0–3), which can be efficiently excited by blue light and emit the yellow-orange light, were developed using the solid solution design strategy combining the chemical unit substitution and the cation substitution. Crystal structures of the four compounds were reported for the first time via the Rietveld refinement of their powder XRD patterns. All phosphors show the general cubic garnet structure with the space group Iad. The specific occupancy of Lu/Y, Al/Mg, Al/Si and O atoms in different positions was identified. The evolution of cell parameters and Y/Lu/Ce–O bond lengths were identified. Photoluminescence properties were evaluated on aspects of emission/excitation spectra, internal/external quantum efficiency and thermal emission stability. Under the 450 nm blue light excitation, the phosphors exhibit bright yellow color emission, peaking in the 575–597 nm spectral range. The internal and external quantum efficiency can reach 83% and 58%, respectively. The emission red-shift in response to the Y/Lu ratio variation was discussed in relation to the local structure evolution. The phosphors are relatively promising to act as wavelength converter of blue light in white light emitting diodes.

This paper reports the development of new phosphors using the chemical unit cosubstituting solid solution design strategy. Starting from Lu3Al5O12, the Al3+–Al3+ couple in respective octahedral and tetrahedral coordination was simultaneously substituted by a Mg2+–Si4+ pair forming the Lu3(Al2−xMgx)(Al3−xSix)O12:Ce3+ (x = 0.5–2.0) series; as a result, the CeO8 polyhedrons were compressed and the emission got red-shifted from green to yellow together with the broadening. The evolution of, the unit cell, the local structural geometry as well as the optical properties of Ce3+ in these garnet creations, in response to the gradual Mg–Si substitution for Al–Al, were studied by combined techniques of structural refinement and luminescence measurements. The new composition Lu2.97Ce0.03Mg0.5Al4Si0.5O12 was comprehensively evaluated regarding its potential application in blue LED-driven solid state white lighting: the maximum emission is at 550 nm under λex = 450 nm; the internal and external quantum efficiencies can reach 85% and 49%, respectively; a 1-phosphor-converted wLED lamp fabricated using the as-prepared phosphor exhibits the luminous efficacy of 105 lm W−1, the correlated color temperature of 6164 K and the color rendering index (Ra) of 75.6. The new solid solution composition series is open for further optimization to enhance the competence for commercial consideration.

To decrease the rare earth element usage and synthesis cost of Y3Al5O12:Ce phosphor, the Y2BaAl4SiO12 compound is developed as a new host for Ce3+ employing the solid solution design strategy. The design uses polyhedron substitution where YO8/AlO4 are partially replaced by BaO8/SiO4, respectively. Structure analysis of Y2BaAl4SiO12 proves that it successfully preserves the garnet structure, crystallizing in the cubic Iad space group with a = b = c = 12.00680(5) Å. Barium (Ba) atoms occupy the Y site and silicon (Si) atoms occupy the Al site in the AlO4 tetrahedrons. An expanded study on Y2MAl4SiO12 (M = Ba, Ca, Mg, Sr) series shows a cation size (of M)-dependent phase formation behavior. The lattice stability can be related with the M type in the M–Si pair and substitution level of M–Si for Y–Al. Doping Ce3+ into Y2BaAl4SiO12 yields bright yellow photoluminescence peaking at around 537 nm upon excitation by 460 nm light. The emission intensity is quite stable against thermal quenching whereas the peak wavelength shows a slight red-shift as the ambient temperature increases. The crystallization behavior of Y2BaAl4SiO12 is suggested as melt-assisted precipitation/growth based on cathodoluminescence analysis. The highly crystalline nature of the microcrystals explains the stable emission against thermal quenching. This study may provide an inspiring insight into preparing phosphor with new morphology-structure of “microcrystal-glass powder phosphor”, which distinguishes it from conventional “ceramic powder phosphor” or “single-crystal phosphor”.

Single crystals of JEM-phase NdSi6−zAl1+zOzN10−z were successfully prepared from starting powders of Si3N4, AlN and Nd2O3 at 1700 °C for 3 h under nitrogen atmosphere. The z value of Nd-doped JEM-phase was determined to be 0.4 via determination of oxygen and nitrogen by elemental analysis. This result may be beneficial for overcoming the difficulty on preparation of single-phase JEM-phase Sialon materials and further characterization on their properties. The detailed crystal structure of Nd-Sialon was solved on the basis of single-crystal X-ray diffraction data for the first time. The space group is Pbcn (no. 60); a = 9.3060(6) Å, b = 9.7224(6) Å, c = 8.8777(5) Å; Z = 4; V = 803.22(8) Å3; Dc = 3.971 g cm−3; R1 = 0.0297 and wR2 = 0.0739 for all reflections refined against F2, with GooF value of 1.031.

Core–shell SiC/SiOx nanochain heterojunctions have been successfully synthesized on silicon substrate via a simplified thermal evaporation method at 1500 °C without using catalyst, template or flowing gases (Ar, CH4, N2, etc.). X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy combined with energy-dispersive X-ray spectroscopy, scanning transmission electron microscopy and Fourier-transform infrared spectroscopy are used to characterize the phase composition, morphology, and microstructure of the as-synthesized nanostructures. A combined vapor–solid growth and modulation procedure is proposed for the growth mode of the as-grown SiC/SiOx nanochains. The formation of SiOx beads not only relates to the Rayleigh instability and the poor wettability between SiC and SiOx, but also to the existence of a high density of stacking faults within SiC-core nanowires. The photoluminescence spectrum of the nanochains exhibits a significant blue shift, which can be highly valuable for future potential applications in blue-green emitting devices.