•We develop a one-step solution combustion synthesis method to prepare Fe3O4 nanoparticles.•The simple designed SCS device ensures an airless condition in the whole process.•Glycine effects on reaction, phase, morphology and magnetic property of product are studied.•Pure phase Fe3O4 nanoparticles are obtained when ϕ = 0.7.•They own high saturation magnetization of 89.17 emu g−1 and small grain size of 57.3 nm.Magnetite (Fe3O4) nanoparticles have been readily prepared via a one-step solution combustion synthesis (SCS) method by designing a simple airless device: a beaker with perforated rubber plug could not only separate the outside air but also release the gases generated during the combustion reaction, which could ensure an air free condition in the SCS process. The whole process did not involve any toxic or unavailable reagents, and could be finished in a few minutes by its self-generated energy derived from the redox reaction between glycine (fuel) and ferric nitrate (oxidizer). Innovatively, the combustion reaction mechanism, morphology and microstructure, phase composition and magnetic properties of SCS products in relation to the glycine have been systematically investigated. The results revealed that with the increasing molar ratio (ϕ) of glycine to ferric nitrate, the combustion mode varied from self-propagating combustion to smouldering combustion and the average grain size of SCS products increased in nanometer scale. On the contrary, the iron oxidation state of SCS products decreased with the increase of ϕ value, and the oxide phase changed from α-Fe2O3 to Fe3O4 and then to FeO sequentially. It was noteworthy that when ϕ = 0.7, we could easily obtain pure phase Fe3O4 nanoparticles with the highest saturation magnetization of 89.17 emu g−1 and small average grain size of 57.3 nm, which would have great potential for various applications, such as magnetic drug delivery, magnetic data storage and novel ferrofluids.Download high-res image (186KB)Download full-size image

•Bcc Fe50Co50 nanoalloys were synthesized via a combustion-based route.•The crystallite size of Fe50Co50 nanoalloys reduced at 500 °C are ∼50 nm.•Fe and Co elements are evenly distributed in a single nanoparticle.•Fe50Co50 nanoalloys exhibit high saturation magnetization.Solid solution Fe50Co50 nanoalloys (NAs) with body centered cubic (bcc) structure have been successfully synthesized via a facile combustion-based route with two simple steps. Firstly, the mixed oxides (CoFe2O4 and CoO) were prepared by solution combustion synthesis. Subsequently, the Fe50Co50 NAs were synthesized through hydrogen reduction of mixed oxides. The influence of the fuel-to-oxidizer ratio (φ) on the phase constituents, specific surface area and morphology of the combustion products were discussed. The phases, morphology and magnetic properties of reduction products at various temperatures were investigated. The product reduced at 500 °C exhibits the bcc Fe50Co50 NAs structure with crystallite size ∼50 nm and the two elements are evenly distributed in a single nanoparticle. The saturation magnetization of Fe50Co50 NAs reduced at 500 °C reaches 214.77 emu/g. Considering the simple and facile preparation process, the synthesized Fe50Co50 NAs with high saturation magnetization will present a wide range of potential applications in data storage, magnetic resonance imaging and biomedicine.

In this work, the carbothermal reduction-nitridation process of low-temperature combustion synthesis (LCS) (Al2O3+C) precursor was investigated in detail. Compared with conventional precursor, the LCS precursor possesses many advantages such as amorphous structure, nanosized particles, homogeneous mixing at molecular level. The experimental results indicate that the methods for preparing precursor exert great influence on phase transformation of Al2O3, onset temperature of nitridation and reaction activity. During the calcination, the phase transformation of Al2O3 is hindered by a large amount of surrounding C particles rendering Al2O3 maintains high reactivity. Accordingly, the nitridation reaction initiates at 1300 °C and completes at 1500 °C for 2 h. Furthermore, the reaction mechanism was also discussed on the basis of experiments. More significantly, it is established that the activation energy of carbothermal reduction-nitridation reaction using LCS precursor is Eα=336 KJ/mol.

•Perfect spherical powder with particle size from 6 μm to 11 μm has been fabricated.•The fabrication was achieved by a well-designed method with two simple steps.•Complete dispersion, effective grading and shape modification were achieved.•Monodisperse powder with narrow particle size distribution has been obtained.•Existing calculation and simulation were used to explain and optimize experiments.Fine-grained spherical tungsten powder with particle size from 6 μm to 11 μm has been fabricated by a well-designed method with two simple steps. A pretreatment of tungsten powder was carried out in the first step. Complete dispersion, effective classification and favorable shape modification have been achieved by jet milling process. Accordingly, monodisperse tungsten powders with narrow particle size distribution were obtained. On the basis of the existing calculation and simulation results, plasma spheroidization parameters have been optimized. Thus, fine-grained spherical tungsten powder with narrow particle size distribution has been prepared by subsequent radio frequency (RF) inductively coupled plasma spheroidization. Furthermore, the presented method can be useful in fabricating spherical tungsten powder of different particle size with narrow particle size distribution as well as for process control in large-scale continuous production.Download high-res image (282KB)Download full-size image

•Jet milling treatment resulted in effective dispersion of tungsten powders.•Precise classification of tungsten powders can be acquired.•High packing density was obtained by deagglomeration of tungsten powder.•Particles collision led to favorable particle shape modification.Fine grinding process of different particle size tungsten powders was carried out by fluidized bed jet milling. The results showed that the jet milling treatment caused deagglomeration of tungsten powders, which led to particles sufficient dispersion and narrow particle size distribution. Grinding gas pressure of 0.70 Mpa made the particles achieve high speed which promoted the particles collision contributing to particle dispersion and shape modification. For tungsten powder with particle size of 3 μm FSSS, a higher packing density with 5.54 g/cm3 was obtained, compared with the 3.71 g/cm3 of the original powder. For tungsten powder with particle size of 1 μm FSSS, the big agglomerates disappeared and the particle size distribution become narrower, while small aggregates about 2–3 μm still exist after the jet milling process. For tungsten powder with particle size of 5 μm and 10 μm FSSS, different medium diameter particle size and narrow particle size distribution of monodisperse tungsten powders can be produced by the optimized jet milling parameters. More important, the effective dispersion, favorable shape modification and precise classification have been achieved in the simple process.Download high-res image (174KB)Download full-size image

•Fe-4Si-0.8P soft magnetic alloy was prepared by metal injection molding.•The sample with nearly full density was obtained at 1300 °C for 4 h.•B6000 of 1.59 T, μm of 2467 and Hc of 130 A/m have been obtained.•Relative high resistivity of 81.2μΩ·cm was acquired.Fe-4Si-0.8P soft magnetic alloy was prepared by metal injection molding (MIM). Ferrophosphorus liquid phase sintering promoted densification and enhanced magnetic properties. The sample with nearly full density, the saturation induction of 1.59 T, maximum permeability of 2467, coercive force of 130 A/m and resistivity of 81.2 μΩ·cm was obtained at 1300 °C for 4 h. Competitive properties contributed toward achieving low magnetic losses. Therefore, MIM Fe-4Si-0.8P can be widely used in the field of magnetic materials.Download high-res image (61KB)Download full-size image

Foam-like MoO2 assembled from nanoparticles was fabricated by a solution combustion synthesis method using hexaammonium molybdate, ammonium nitrate (NH4NO3) and glycine as the precursors. The effect of the glycine/NH4NO3 ratio (Φ = 0.25, 0.50, 0.75, 1.0 and 1.25) on the physicochemical properties of the final products was systematically studied. The Φ value was found to display significant roles in the final phases and morphologies of the products. With a Φ value of 0.50, the foam-like product consisting of MoO2 nanoparticles with an average size of about 20–30 nm was synthesized. The photocatalytic activities of the foam-like MoO2 towards degradation of several contaminants, including methyl orange (MO), methylene blue (MB), rhodamine B (Rh B) and phenol, were investigated. The foam-like MoO2 offered excellent capability and stability toward photocatalytic degradation of the studied contaminants. The results reported here demonstrated that rational design of MoO2-based photocatalysts might be able to improve their properties in energy conversion and environmental preservation.

For the first time, bowl-like hollow carbon spheres (BHCSs) have been designed and fabricated by the combination of hydrothermal carbonization and soft templating. The obtained BHCSs exhibit well-defined shapes with the size ranging from 1 to 2 μm. As electrodes of electrochemical double layer capacitors they showed good performance.

•W nanopowder was prepared by solution combustion synthesis and hydrogen reduction.•The precursor can be completely reduced at as low as 700 °C for 2 h.•93.3% of relative density could be obtained at sintering temperature of 1200 °C.In this work, tungsten nanopowder was prepared by solution combustion synthesis (SCS) and hydrogen reduction. First, needle-like W18O49 as precursor was fabricated by SCS. Subsequently, hydrogen reduction of as-synthesized precursor was utilized to prepare tungsten nanopowder. The precursor synthesized by SCS exhibits high reduction reactivity and can be completely reduced to pure tungsten nanopowder at as low as 700 °C for 2 h. The tungsten particles reduced at 700 °C are spherical or elliptical and the particle size is 20–30 nm. The sintering behavior of the as-prepared tungsten nanopowder was investigated by analyzing the sintered compacts obtained at different sintering temperatures. 93.3% of relative density of the compact could be obtained at sintering temperature of 1200 °C. The microhardness of the compact sintered at 1500 °C reached the highest point of 587.14 Hv0.2.

Novel hollow porous VOx/C nanoscrolls are synthesized by an annealing process with the VOx/octadecylamine (ODA) nanoscrolls as both vanadium and carbon sources. In the preparation, the VOx/ODA nanoscrolls are first achieved by a two-phase solvothermal method using ammonium metavanadat as the precursor. Upon subsequent heating, the intercalated amines between the vanadate layers in the VOx/ODA nanoscrolls decompose into gases, which escape from inside the nanoscrolls and leave sufficient pores in the walls. As the anodes of lithium-ion batteries (LIBs), such hollow porous VOx/C nanoscrolls possess exceedingly high capacity and rate capability (904 mAh g–1 at 1 A g–1) and long cyclic stability (872 mAh g–1 after 210 cycles at 1 A g–1). The good performance is derived from the unique structural features of the hollow hierarchical porous nanoscrolls with low crystallinity, which could significantly suppress irreversible Li+ trapping as well as improve Li+ diffusion kinetics. This universal method of annealing amine-intercalated oxide could be widely applied to the fabrication of a variety of porous electrode materials for high-performance LIBs and supercapacitors.Keywords: anodes; hollow; lithium-ion batteries; low-crystalline; VOx/C nanoscrolls

A new class of mesoporous single crystalline (MSC) material, Co(OH)2 nanoplates, is synthesized by a soft template method, and it is topotactically converted to dual-pore MSC Co3O4. Most mesoporous materials derived from the soft template method are reported to be amorphous or polycrystallined; however, in our synthesis, Co(OH)2 seeds grow to form single crystals, with amphiphilic block copolymer F127 colloids as the pore producer. The single-crystalline nature of material can be kept during the conversion from Co(OH)2 to Co3O4, and special dual-pore MSC Co3O4 nanoplates can be obtained. As the anode of lithium-ion batteries, such dual-pore MSC Co3O4 nanoplates possess exceedingly high capacity as well as long cyclic performance (730 mAh g–1 at 1 A g–1 after the 350th cycle). The superior performance is because of the unique hierarchical mesoporous structure, which could significantly improve Li+ diffusion kinetics, and the exposed highly active (111) crystal planes are in favor of the conversion reaction in the charge/discharge cycles.

Orthorhombic single crystal V2O5 sheets with lateral dimensions of 4–6 μm were synthesized by a facile one-pot organics-assisted pyrolysis method. TG-MS measurements revealed the intrinsic reaction mechanism of the as-prepared V2O5 sheets. As cathode materials for the lithium ion batteries (LIBs), V2O5 sheets delivered high initial discharge capacity of 310 mA h g−1 and the coulombic efficiency remained close to 100% during the 50 charge-discharge cycles. Good electrochemical performance is attributed to the unique sheet structure, which increases the contact area between the active material and the electrolyte. Moreover, the structure greatly facilitates intercalation and deintercalation of Li+ ions and electron transport. Developed approach is simple, low cost and has excellent scalability for preparing V2O5 sheets as high-performance LIBs cathodes.

We report a new chemical reaction route to synthesizing CuO porous mesocrystal ellipsoids via decomposition of copper vanadium oxide under hydrothermal conditions. By finely tuning the oriented attachment growth mechanism of CuO, a porous mesocrystal structure was synthesized. Structural and morphological evolutions of the CuO product were investigated and the formation of CuO porous mesocrystal ellipsoids here was essentially determined by the amount of ammonium metavanadate. An oriented nanoparticle aggregation with tailoring of the structure, including compact mesocrystals and porous mesocrystals, could be achieved in different concentrations of reactants. The strategy of constructing the structure via an oriented attachment growth mechanism could be applied to the synthesis of other nanomaterials with complex structures.

•WCx/C composite was synthesized by combustion-carbothermal reduction method.•Systematic experiments generated to investigate the synthesis process.•The WCx/C composite exhibits good hydrogen evolution reaction catalytic activity.Tungsten carbide/carbon (WCx/C) composite was synthesized by combustion-carbothermal reduction method. Systematic experiments that vary the ratio of the carbon atom of glucose to the tungsten atom of ammonium tungstate (C/W ratio), temperature and holding time used generated to investigate the synthesis process. The morphology of the as-prepared powders is flake-like and the WCx nanoparticles are embedded in the carbon matrix. This method is facile and easy to scale up. Electrochemical measurements demonstrate that the WCx/C composite exhibits good hydrogen evolution reaction (HER) catalytic activity, giving a η10 (the overpotential for driving a current of 10 mA cm−2) of −264 mV and Tafel slope of 85 mV dec−1 in acid solution (0.5 M H2SO4).

In this paper, one-dimensional W18O49 nanopowders were fabricated by a one-step solution combustion method using glycine as the fuel and a metal acid radical ion as the metal source. The morphologies and non-stoichiometric single-crystal phase of W18O49 can be controlled by changing the amount of the fuel. The nanoneedles had a large amount of defects such as oxygen vacancies. This characteristic resulted in an excellent visible light-driven photocatalytic performance that took about 50 min to degrade methylene blue (100 mL; 40 mg L−1) under visible light. The interesting reaction mechanism of such needle-like W18O49 and the photocatalytic mechanism are studied in this paper.

Iron oxides were synthesized by solution combustion synthesis using glycine (fuel) and ferric nitrate (oxidizer) as raw materials. The effects of the fuel to oxidizer ratio, ϕ, on the combustion behavior, phase, morphology and surface area of the products were systematically studied. Pure hematite was synthesized directly by the combustion of the precursors under fuel-lean conditions in one step without further heat treatment, simply by selecting a proper fuel to oxidizer ratio, ϕ. The hematite has a highly mesoporous structure with specific surface area of 103 m2 g-1 and an average size of about 20 nm, which was obtained at ϕ=0.3. The hematite displays a continuous absorption band in the visible region. The photocatalytic activity of the hematite was evaluated by degrading the methylene blue pollutant in water at ambient temperature. The synthesized mesoporous hematite is a promising visible light photocatalysts for organics decomposition.

Fe-Ni-Y2O3 nanocomposites with uniform distribution of fine oxide particles in the gamma FeNi matrix were successfully fabricated via solution combustion followed by hydrogen reduction. The morphological characteristics and phase transformation of the combusted powder and the Fe-Ni-Y2O3 nanocomposites were characterized by XRD, FESEM and TEM. Porous Fe-Ni-Y2O3 nanocomposites with crystallite size below 100 nm were obtained after reduction. The morphology, phases and magnetic property of Fe-Ni-Y2O3 nanocomposites reduced at different temperatures were investigated. The Fe-Ni-Y2O3 nanocomposite reduced at 900 °C has the maximum saturation magnetization and the minimum coercivity values of 167.41 A/(m2·kg) and 3.11 kA/m, respectively.

Mesoporous Cr2O3 with a high specific surface area of 162 m2 g−1 is prepared by the solution combustion method. The mesoporous Cr2O3 has a sheet structure, which consists of nanoparticles with an average size of 20 nm. As an anode electrode material for rechargeable lithium-ion batteries, the mesoporous Cr2O3 nanoparticles display enhanced electrochemical performance. Stable and reversible capacity of 480 mA h g−1 after 55 cycles is demonstrated. The enhanced electrochemical performance of the Cr2O3 can be attributed to the high surface area and morphological characteristics of mesoporous materials.

•High-performance Fe–79%Ni–4%Mo alloy was produced by metal injection molding.•The magnetic properties were found to be closely related to density and grain size.•The sintering parameters of Fe–79%Ni–4%Mo alloy were optimized.Fe–79%Ni–4%Mo alloy is well known to be a soft magnetic material widely used for the magnetic head, magnetic shield, and instrumentation components because of high permeability and low coercivity. In order to realize economical mass production of minisize, complex shaped and high performance soft magnetic parts, Fe–79%Ni–4%Mo alloy was produced by metal injection molding, using carbonyl iron, carbonyl nickel and molybdenum powder as raw materials. The effects of sintering temperature and time on the microstructure and magnetic properties of the alloys were investigated. The results indicate that the magnetic properties are dependent on the microstructure. The densification and grain size of the alloys increase with increasing sintering temperature and time, facilitating the enhancement of permeability and saturation induction, as well as the decrease of the coercive force. In the case of the sintering temperature of 1320 °C for 10 h, the relative density of 97.2%, the maximum permeability of 116000, saturation induction of 0.8 T and coercive force of 1.126 A/m were achieved. Further elongation of sintering time did not bring about an increase of densification and grain size.The figure shows the effect of sintering time on the relative density and magnetic properties at 1320 °C. It can be seen that the relative density, saturation induction and maximum permeability increase while the coercive force decreases with the elongation of sintering time. Relative density increases significantly in the sintering time range of 2–8 h and maximum permeability increases quickly when the sintering time increases from 2 h to 10 h. It is noted that the density keeps almost the same after being sintered for more than 8 h, but the maximum permeability shows noticeable increase.

Copper vanadate oxides (CVOs) have a wide variety of crystalline phases such as CuV2O6, Cu3V2O8, Cu0.95V2O5, Cu0.4V2O5, Cu2V2O7 and so on, and CVOs have been used as catalysts and battery materials. Here, for the first time, we present a new hexylamine-assisted method to prepare hierarchical Cu4V2.15O9.38 superstructures assembled by single-crystalline rods. The results show that hexylamine was responsible for the generation of Cu4V2.15O9.38, and that the Cu4V2.15O9.38 superstructures were transformed from the intermediate Cu3(OH)2V2O7·2H2O. Then, we studied the electrochemical properties of Cu4V2.15O9.38 superstructures in electrocatalytic oxidation of glucose and a primary lithium-ion battery. The sensitivity of the modified electrode for detecting glucose was estimated to be 175.8 μA mM−1 cm−2, and the detection range was from 0 to 3 mM, and the detection limit was less than 0.1 mM. The superstructures showed a large discharge capacity of 301 mA h g−1 at 5 mA g−1, thus making it an interesting candidate for primary lithium-ion batteries.

Carbon spheres (CSs) immobilized with monodispersed Cu nanoparticles were synthesized by a non-surfactant-assisted method. In this protocol, the biomass (ascorbic acid) transformed into the spheres of hydrothermal carbon through hydrothermal carbonization, and copper chlorite was reduced to Cu nanoparticles, which were in situ deposited on the spheres. No excess surfactant or capping reagent was necessary, which made the surface of the as-prepared nanoparticles very clean. In the following annealing, the spheres of hydrothermal carbon converted into CSs and the size of Cu nanoparticles could be tuned from several nanometers to dozens of nanometers by changing the annealing temperature only. This hybrid composite exhibited excellent catalytic activity for oxidation of glucose and could be employed as a rapid and inexpensive glucose sensor.

AlN powders were prepared by combining sodium fluoride-assisted solution combustion with carbothermal reduction-nitridation. The effects of sodium fluoride on the nitridation reactivity, specific surface areas and morphology of the synthesized AlN powders were investigated in detail. The morphology of the AlN products changed from highly fluffy and porous networks into regular and hexagonal thin flakes, and the specific surface area decreased with the sodium fluoride content. No hard agglomeration could be found in decarburized AlN powders. The phase-pure AlN has been observed in all products calcined above 1300 °C, and no sodium was detected in the AlN powders by the X-ray fluorescence spectrometry.

•Nanocrystalline Fe–50%Ni powder was synthesized via solution combustion synthesis.•The morphology and phase constituents of the combusted powders were investigated.•The magnetic properties of the obtained Fe–50%Ni powders were investigated.Nanocrystalline Fe–50%Ni powder was synthesized via solution combustion process followed by hydrogen reduction. The influence of glycine to ferric nitrate ratio (G/Fe) on the combustion behavior and morphology evolution of the combusted powder was investigated. The effect of reduction temperature on the morphology and crystallite size of the obtained γ-Fe50%Ni powder was characterized. Porous γ-Fe–Ni powder with crystallite size below 100 nm was obtained after reduction. The Fe–50%Ni powder reduced at 700 °C has the maximum saturation magnetization and the minimum coercivity values of 156.33 emu/g and 37.2 Oe, respectively.Fe–50%Ni powder with crystallite size below 100 nm was synthesized via solution combustion process followed by hydrogen reduction. The Fe–50%Ni powder reduced at 700 °C has the maximum saturation magnetization and the minimum coercivity values of 156.33 emu/g and 37.2 Oe, respectively.

•High-performance pure iron was produced by metal injection molding.•The δ phase sintering improved the density and magnetic properties greatly.•The magnetic properties were found to be closely related to density and grain size.Using atomized iron powder as raw materials, pure iron soft magnetic material was prepared by metal injection molding and δ phase sintering. The δ phase sintering improved the density and magnetic properties greatly. The specimen with nearly full density and the maximum permeability of 17,400, magnetic induction (B6000) of 1.81 T and coercive force of 20.6 A/m was achieved after sintering at 1450 °C for 6 h. The magnetic properties were comparable to those of wrought pure iron.

•High-performance Fe-79%Ni-4%Mo alloy was produced by metal injection molding.•Maximum permeability was sensitive to stress and closely related to grain size.•The sintering parameters of Fe-79%Ni-4%Mo alloy were optimized.Metal injection molding (MIM) is a process that has the predominance in the economical mass production of minisize, complex shaped soft magnetic parts. However, not full dense materials could have their density dependent properties as magnetic induction decreases, and also generated microstructure can be affected, showing large pores, that could act as domain-wall barriers reducing soft magnetic performance. This study overcame this problem and obtained high magnetic property and full density Fe-79%Ni-4%Mo alloy by MIM, hot isostatic pressing and subsequent heat treatment. The maximum permeability, saturation induction and coercive force are 210,000, 0.862 T and 0.95 A/m, respectively. The relationships between processing parameters, density, stress, microstructure and magnetic properties were investigated. The results revealed that maximum permeability was more sensitive to stress and magnetic performance was strongly influenced by density and microstructure.

•A (SiO2 + C) precursor is prepared by low temperature combustion synthesis method.•The initial formative temperature of SiC in present work is about 1200 °C.•The transformation of SiO2 to SiC can be completed at 1500 °C for 2 h.•SiC powder synthesized at 1500 °C exhibits mostly near-spherical nanoparticles.•The present holes in precursor are responsible for the formation of whiskers.SiC nanopowder was synthesized by carbothermal reduction of a low-temperature combustion synthesized (LCS) precursor derived from silicic acid, polyacrylamide (PAM), nitric acid, urea, and glucose mixed solution. The results showed that the LCS precursor is a kind of porous blocky particles. The precursors were subsequently calcined under argon at 1100–1500 °C for 2 h. The transformation of SiO2 to SiC occurred at 1200 °C, and complete transformation of SiO2 to SiC was achieved at 1500 °C. The SiC powder synthesized at 1500 °C is mostly composed of near-spherical particles with the diameter of 50–100 nm. Moreover, the SiC powder also contains very rare amount of whiskers with a diameter of 80 nm and a length of up to several micrometers. It is proposed that the present holes in the precursor particles during calcination are responsible for the formation of whiskers. Furthermore, the formation of mainly SiC near-spherical nanoparticles is ascribed to coarse surface of precursor particles during calcination, intimate contact among SiO2 and C particles, uniformly formed free space during reduction reaction, and separation effect of unreacted carbon.

Novel hybrid hollow spheres (HSs) are easily prepared by a combination of hydrothermal carbonization (HTC) and emulsion template method for the first time. The HSs have an average diameter of 3.5 μm and a shell thickness of about 70 nm. The HSs consist of a matrix of hydrothermal carbon, in which Cu nanoparticles of several nanometers in size are imbedded, and exhibit a well-defined shape, a relatively uniform size and high flexibility. With regard to the formation mechanism, trioctylamine (TOA) droplet in the oil-in-water (W/O) emulsion plays the role of a template. Under hydrothermal conditions, TOA in the droplet and Cu2+ outside the droplet form the Cu–amine complex, which aggregates at the interface and is then reduced to form Cu nanoparticles by ascorbic acid (VC), and HTC of VC to hydrothermal carbon occurs at the interface. By changing the carbon source into glucose the size of HSs can be tuned down to 1 μm and the bowl-like hollow structure can be obtained by increasing reaction time, indicating the flexibility of this approach. Due to the special structure of these HSs, they can be used as a new ultrasound contrast agent or a template for porous CuO HSs.

•A uniform (TiO2 + C) precursor is prepared by combustion synthesis method.•The (U/Ti) molar ratio in solution governs the (C/Ti) molar ratio in precursor.•The initial transformation of TiO2 to TiN occurs at 900 °C.•The complete transformation of TiO2 to TiN is achieved at 1100 °C for 2 h.•TiN powder synthesized at 1100 °C is mainly comprised of particles of 80–100 nm.TiN nanopowder was synthesized by carbothermal reduction method by using a (TiO2 + C) precursor derived from titanyl nitrate, urea, glucose, ammonium nitrate, and citric acid mixed solution. The results revealed that the obtained precursor consisted of flake particles with a uniform dispersion of amorphous TiO2 and C. The precursor powders were subsequently calcined under nitrogen at 900–1300 °C for 2 h. The initial transformation of TiO2 to TiN, by adopting this route, occurred at 900 °C. Moreover, TiOxNy, TiO2, and carbon below 1200 °C, and TiCxNy, TiOxNy, TiO2, and carbon at (or above 1200 °C) were found to be as impurities with the calcined products. The lattice parameter of TiN synthesized at 1100 °C (α = 4.240 Å) agrees well with the theoretical value (α = 4.241 Å). TiN powder, synthesized at 1100 °C, exhibited well-distributed spherical particles ranging from 80 to 100 nm. The nitrogen, oxygen, and residual carbon contents of TiN powder synthesized at 1100 °C were found to be 20.37 wt.%, 1.91 wt.%, and 3.36 wt.%, respectively.

High magnetic property Fe-50%Ni alloy was obtained by metal injection molding (MIM), hot isostatic pressing and subsequent heat treatment. The maximum permeability, saturation induction and coercive force are 112 mH m−1, 1.58 T and 2.52 A m−1, respectively. The maximum permeability far exceeds the reported value (22.36–42.50 mH m−1) of Fe-50%Ni produced by MIM. The relationships between processing parameters and density, microstructure and magnetic properties were investigated. The results revealed that magnetic performance was strongly influenced by density and microstructure.Highlights► High-performance Fe-50%Ni alloy was produced by powder injection molding. ► The magnetic properties were found to be closely related to density and grain size. ► The sintering parameters of Fe-50%Ni alloy were optimized.

Si3N4 powders were synthesized by a carbothermal reduction method using a SiO2 + C combustion synthesis precursor derived from a mixed solution consisting of silicic acid (Si source), polyacrylamide (additive), nitric acid (oxidizer), urea (fuel), and glucose (C source). Scanning electron microscopy (SEM) micrographs showed that the obtained precursor exhibited a uniform mixture of SiO2 + C composed of porous blocky particles up to ∼20 μm. The precursor was subsequently calcined under nitrogen at 1200–1550°C for 2 h. X-ray diffraction (XRD) analysis revealed that the initial reduction reaction started at about 1300°C, and the complete transition of SiO2 into Si3N4 was found at 1550°C. The Si3N4 powders, synthesized at 1550°C, exhibit a mixture phase of α- and β-Si3N4 and consist of mainly agglomerates of fine particles of 100–300 nm, needle-like crystals and whiskers with a diameter of about 100 nm and a length up to several micrometers, and a minor amount of irregular-shaped growths.

ZrC powders were synthesized by carbothermal reduction of a combustion synthesized precursor derived from zirconium nitrate, urea, and glucose mixed solution. The results showed that the obtained precursor was comprised of polyporous blocky particles. The precursor powders were subsequently calcined under argon at 1200–1600 °C for 3 h. The transformation of ZrO2 to ZrC, by adopting this route, occurred at 1300 °C. The preparation of ZrC experienced an intermediate phase of ZrOxCy. ZrC powders synthesized at 1500 °C are characterized by the spherical shape, small particle size (120–180 nm in diameter), low oxygen content (1.4 wt.%) and non-aggregated particles.Highlights► A (ZrO2 + C) precursor is prepared by the LCS method. ► The (U/Zr) molar ratio in solution governs the (C/Zr) molar ratio in precursor. ► ZrC synthesized at 1500 °C exhibits well-distributed particles of 120–180 nm. ► A close control over carbon content in precursor yields the high purity ZrC.

•Jet milling process significantly changed the tungsten powder characteristics.•The high powder loading of the feedstock has been obtained.•Tungsten sample is easy to get sinter densification at relative low temperature.The greater demands on final product quality of powder metallurgy processing have led to an increased demand for metal powders with high quality. In this paper we report the successful preparation of tungsten powder with a near-spherical shape and surface morphology by jet milling process, with the disappearance of agglomeration and the improvement of dispersion, narrow particle size distribution of tungsten powder was achieved. The values of D10, D50 and D90 changed from 2.02 μm, 3.67 μm and 6.34 μm to the original tungsten powder to 1.36 μm, 2.13 μm and 3.19 μm for the treated tungsten powder, respectively. The process increases apparent density and tap density from 3.71 g/cm3, 5.54 g/cm3 to 5.71 g/cm3, 8.47 g/cm3. Due to the optimization of the powder characteristics, the powder loading of the feedstock was raised to 65 vol% for the treated powder. The sintered samples of 65 vol% powder loading is easy to get sinter densification with no cracks and has superior hardness and microstructure at a relative low temperature of 1900 °C.

•Ammonium vanadate square-nanosheet flowers are synthesised by a solvothermal method.•Using ammonium vanadate flowers as precursor, VO2(B) net-like nanosheets are prepared.•The flowers have a capacity ∼817 mhA g−1 (1 A g−1) as anode of Li-ion batteries.We report special square-nanosheet flowers with an ammonium vanadate phase, which are synthesised by choosing an appropriate solvent system (ethanol aqueous solution) and reductant (octadecylamine (ODA)) under solvothermal conditions. For the synthesis mechanism, a reduction reaction (phase transformation) takes place, where the raw material, NH4VO3, transforms to an intermediate, NH4V3O8, and then to the target ammonium vanadate phase. The ethanol aqueous solvent promotes the oriented growth of the two-dimensional crystal. ODA serves as the reductant and is responsible for the low vanadium valence in the product. By treating these new ammonium vanadate flowers during the hydrothermal reaction, the growth of VO2(B) net-like nanosheets can be realised. To the best of our knowledge, there is no information available on this ammonium vanadate nanostructure and its transformation into VO2(B). This new ammonium vanadate two-dimensional assembly material can be applied as an anode material for the Li-ion batteries and exhibits a reversible electrochemical capacity of 817 mhA g−1 after 130 cycles at 1 A g−1, as well as a good rate performance. The findings in this study have important implications for the synthesis and application of ammonium vanadate and vanadium oxide bronze nanostructures.

Mesoporous graphite encapsulated Fe3C/Fe nanosheet composites have been synthesized by a facile template free method using ferric nitrate, glycine and glucose as raw materials. X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and Raman spectrometer have been used to characterize the composites. The formation process and morphology of the products have been discussed in detail. Interestingly, this facile route can synthesize graphite encapsulated Fe3C, Fe3C/Fe and Fe composites with two dimensional nanosheet structure by tuning the reaction temperature and the Fe3C and Fe nanoparticles with size less than 30 nm are well dispersed on the carbon sheet. The mesoporous graphite encapsulated Fe3C/Fe nanosheet composites with a high specific surface area have application in non-noble metal electrocatalysis for hydrogen evolution reaction.Mesoporous graphite encapsulated Fe3C/Fe nanosheet composites have been synthesized by a facile template free method. The mesoporous graphite encapsulated Fe3C/Fe nanosheet composites with a high SSA have potential application in non-noble metal electrocatalysis for hydrogen evolution reaction and can be broadened to other prospective applications.Download high-res image (63KB)Download full-size image

For the first time, bowl-like hollow carbon spheres (BHCSs) have been designed and fabricated by the combination of hydrothermal carbonization and soft templating. The obtained BHCSs exhibit well-defined shapes with the size ranging from 1 to 2 μm. As electrodes of electrochemical double layer capacitors they showed good performance.