Co-reporter:Li Li, Jianbo Zhang and Qingshan Zhu
Dalton Transactions 2016 vol. 45(Issue 7) pp:2888-2896
Publication Date(Web):22 Dec 2015
DOI:10.1039/C5DT04091D
Meso/macroporous TiO2–Fe2O3 composite particles are prepared using naturally abundant ilmenite via a novel heat treatment induced fractional crystallization strategy in a fluidized bed. Fluid-bed roasting in oxidizing and reducing environments is carried out in order to realize the fractional crystallization of ilmenite. Subsequently, acid leaching is employed to remove most of the ferrous phase and form porous TiO2–Fe2O3 composites. The influences of the reaction parameters on the composition, structure and properties of the products are studied. It is found that the pore structure and composition of the porous TiO2–Fe2O3 composite particles can be controlled simply by controlling some parameters, such as the roasting time, temperature, precursor particle size, and post-roasting treatment. Photocatalytic and electrochemical cycling measurements show that the synergism of porous structures and the controlled doping of α-Fe2O3 endow the as-obtained products with excellent visible light photocatalytic activity and provide enhanced performance in lithium ion batteries. The composite porous particles thus obtained may have some promising applications in the fields of photocatalysts, electrode materials, absorbers, pigments etc. This work opens a new avenue for reasonable combination of cost-effective raw materials, a large scale fabricating process and fine control over the structure and composition in the design and preparation of functional materials.
Co-reporter:Chao Lei, Gengyu Zhang, Qingshan Zhu, Zhaohui Xie
Powder Technology 2016 Volume 296() pp:79-86
Publication Date(Web):August 2016
DOI:10.1016/j.powtec.2015.12.024
•Composition and structure variations of carbon-coated iron ore during reduction were investigated.•The Ccritical value of iron ore decreased with the increase of its metallization ratio.•The Ccritical value reduced to 3.0–3.5 wt.% by process optimization, much lower than the reported value in the literature.Coating carbon on the iron ore powder is a quite promising way to prevent defluidization during its high-temperature direct reduction in the fluidized bed reactor, but usually causes excessive carbon content of the DRI production, thus the present study focuses on decreasing the critical carbon content (Ccritical value) needed for defluidization prevention by the optimization of the pre-reduction process. It was for the first time found that increasing the metallization ratio of the pre-reduced iron ore significantly could reduce the Ccritical value, since it inhibited the carbon consumption and formation of metallic iron during the early stage of high temperature reduction. Based on this result, optimization principle to reduce the Ccritical value was further proposed, i.e. increasing the pre-reduction rate (Rpre-reduction) and reducing the carbon deposition rate (Rcarbon deposition) during the pre-reduction, such as by increasing the temperature and the H2 mole fraction in CO–H2 mixture gas. And such principle was verified by the experiment results, where for the iron ore pre-reduced in CO–H2 mixture gas with the xH2 ≥ 0.9 at 600 °C, its corresponding Ccritical value was less than 3.5 wt.%, much lower than that of other conditions or the reported value in the literature.
Co-reporter:Chao Lei, Shengyi He, Zhan Du, Feng Pan, Qingshan Zhu, Hongzhong Li
Powder Technology 2016 Volume 301() pp:608-614
Publication Date(Web):November 2016
DOI:10.1016/j.powtec.2016.06.048
•We investigated the fluidization/defluidization behavior of carbon-coated iron ore.•The Ccritical value increased with increasing the temperature.•The Ccritical value was little affected by the gas composition.•Gas composition showed obvious effects on the stability of the deposited carbon.•The carbon content in DRI was reduced to < 5 wt.% by process optimization.To reduce the carbon content in the direct reduction iron (DRI) obtained via the two-step fluidized bed reduction process, we investigated the fluidization/defluidization behavior of the carbon-coated iron ore under different gas compositions and temperatures. It was found that the critical carbon content value (Ccritical) needed to prevent defluidization increases obviously with increasing fluidization temperature, but is little affected by the gas composition, while the stability of the deposited carbon is highly dependent on the gas composition, i.e. when the H2 mole fraction is greater than a certain critical value, the deposited carbon is unstable and will be constantly consumed during reduction, leading to the defluidization. Through the process optimization, the carbon content in DRI decreases to < 5 wt.%, which is also much lower than those reported values of 16.5–22.3 wt.% in literature.
Co-reporter:Min Yang;Qing-shan Zhu;Chuan-lin Fan
International Journal of Minerals, Metallurgy, and Materials 2015 Volume 22( Issue 4) pp:346-352
Publication Date(Web):2015 April
DOI:10.1007/s12613-015-1079-x
In the present study, roasting-induced phase change and its influence on phosphorus removal via leaching has been investigated for high-phosphorus iron ore. The findings indicate that phosphorus in the ore is associated with goethite and exists mainly in amorphous Fe3PO7 phase. The phosphorus remains in the amorphous phase after being roasted below 300°C. Grattarolaite (Fe3PO7) is found in samples roasted at 600–700°C, revealing that phosphorus phase is transformed from the amorphous form to crystalline grattarolaite during roasting. Leaching tests on synthesized pure grattarolaite reveal a low rate of phosphorus removal by sulfuric acid leaching. When the roasting temperature is higher than 800°C, grattarolaite is found to react with alumina to form aluminum phosphate, and the reactivity of grattarolaite with alumina increases with increasing roasting temperature. Consequently, the rate of phosphorus removal also increases with increasing roasting temperature due to the formation of acid-soluble aluminum phosphate.
Co-reporter:Tao Zhang, Chao Lei, Qingshan Zhu
Powder Technology 2014 Volume 254() pp:1-11
Publication Date(Web):March 2014
DOI:10.1016/j.powtec.2014.01.004
•Boudouard reaction is coupled with the direct reduction to avoid defluidization.•The noncohesive DRIc particles are constructed and reduced at fluidized state.•The C/Fe ratio has significant influence on stickiness and fluidization behavior.•A two-step fluidized bed DR process is proposed and proved feasible.•The operating lines of the fluidization zones are indicated as maps.The industrial application of fluidized bed direct reduction (DR) process for fine iron ore is hampered by the sticking of direct reduction iron (DRI) particles. In the present study, the carbon precipitation reaction is coupled with the reduction reaction of fine iron ore to modify the cohesive force among DRI particles. The competition between the reduction reaction of fine iron ore and the carbon precipitation reaction leads to three types of fluidization behaviors: fluidization, unstable fluidization and defluidization. The carbon precipitation reaction is dominant at the temperature below 600–675 °C, and the presence of H2 could retard the growth of iron whiskers and promote carbon precipitation. A new type of DRI particle covered with carbon shell is therefore constructed and named as DRIc particle. The growth of iron and carbon gasification can destroy the carbon shell, and lead to the increase of stickiness; however, the presence of CO can retard or prevent the destroying. The C/Fe mass ratio on the surface has significant influence on the stickiness and also the fluidization behavior of DRIc particles. The lower limit of C/Fe mass ratio, below which defluidization occurs, increases sharply with increasing temperature. Based on these findings, a two-step fluidized bed DR process for fine iron ore is proposed and proved feasible, and the operating lines of the fluidization zones are indicated as maps.
Co-reporter:Qingshan Zhu, Jianbo Zhang, Hongzhong Li
Particuology 2014 Volume 14() pp:83-90
Publication Date(Web):June 2014
DOI:10.1016/j.partic.2013.08.002
•Phase and structure changes during high-temperature oxidation and reduction were investigated.•Influence of oxidation on leaching process is primarily attributed to the phase change.•Reduction of as-oxidized ilmenite speeds up iron leaching due to microcracks and holes formation.•The iron leaching rate is in the order of hematite > ilmenite ≫ pseudobrookite in hydrochloric acid.The present study investigated the influence of high temperature oxidation and reduction pretreatments on the leaching rate of Panzhihua ilmenite. The as-pretreated ilmenite was leached with 20% HCl at 105 °C. The leaching process was controlled by the phases and microstructures that evolved during the pretreatment processes. The leaching kinetics of pure hematite, ilmenite and pseudobrookite were characterized to clarify the phase effect on the iron-leaching rate; the rate of iron leaching occurs in the following order in the HCl solution: hematite (ferric iron) > ilmenite (ferrous iron) ≫ pseudobrookite (ferric iron). Therefore, the often-cited notion that ferrous iron dissolves faster in HCl solutions than ferric iron when explaining the pretreatment effects is inaccurate. Moreover, the oxidation pretreatment (at 600–1000 °C for 4 h) cannot destroy the dense structure of the Panzhihua ilmenite. Therefore, the influence exerted by the oxidation on the leaching process is primarily determined by the phase change; oxidation at 600 and 700 °C slightly increased the rate of iron leaching because the ilmenite was transformed into hematite, while the oxidation at 900–1000 °C significantly reduced the rate of iron leaching because a pseudobrookite phase formed. The reduction effect was subsequently investigated; the as-oxidized ilmenite was reduced under H2 at 750 °C for 30 min. The reduction significantly accelerated the rate of subsequent iron leaching such that nearly all of the iron had dissolved after leaching for 2 h in 20% HCl at 105 °C. This enhanced iron-leaching rate is mainly attributed to the cracks and holes that formed during the reduction process.
Co-reporter:Jianbo Zhang;Gengyu Zhang
Metallurgical and Materials Transactions B 2014 Volume 45( Issue 3) pp:914-922
Publication Date(Web):2014 June
DOI:10.1007/s11663-013-0018-3
Morphological changes and phase transition behaviors were investigated for the weak reduction (reduction of ferric iron-to-ferrous state) of preoxidized Panzhihua ilmenite by hydrogen at 873 K to 1073 K (600 °C to 800 °C). Ilmenite was preoxidized for 4 hours at 1023 K and 1173 K (750 °C and 900 °C), respectively, before the reduction. The results revealed that there were two competing reduction routes. At high reduction temperatures, e.g., 1023 K and 1073 K (750 °C and 800 °C), ferric irons from both hematite and pseudobrookite would combine with rutile grains as formed in the preoxidation to form homogeneous ilmenite phase with pores immingled. However, at lower reduction temperatures, e.g., 873 K (600 °C), hematite and pseudobrookite are reduced mainly through direct reduction without the participation of rutile. As a result, the as-reduced ilmenites show great differences in their phase components and microstructure, especially for the Ti species. For ilmenites preoxidized at 1023 K (750 °C), most of the Ti ions present in the needlelike rutile network, but for ilmenites preoxidized at 1173 K (900 °C), Ti distributed in both irregular rutile grains and ilmenite matrix.
Co-reporter:Pengcheng Li, Jun Li, Qingshan Zhu, Lijie Cui and Hongzhong Li
RSC Advances 2013 vol. 3(Issue 23) pp:8939-8946
Publication Date(Web):11 Apr 2013
DOI:10.1039/C3RA40511G
A Co–Al2O3 aerogel catalyst, which was prepared via a sol–gel process followed by supercritical drying, was granulated to improve the fluidization quality. This showed that the fluidization of the aerogel catalyst could be considerably improved by granulation. The effect of granulation on the activity and the stability of the aerogel catalyst was investigated in a fluidized-bed reactor in the CH4–CO2 reforming reaction. It was found that granulation can significantly improve the catalytic performance of the aerogel catalyst, e.g. the granulated aerogel catalyst showed a much better catalytic stability and greater conversion of methane as compared with the non-granulated aerogel catalyst. The improved catalytic performance of this granulated catalyst was attributed to the better fluidization quality in the fluidized-bed reactor.
Co-reporter:Jun Li, Li Zhou, Qingshan Zhu, and Hongzhong Li
Industrial & Engineering Chemistry Research 2013 Volume 52(Issue 20) pp:6647-6654
Publication Date(Web):April 25, 2013
DOI:10.1021/ie3030104
CO methanation reaction over a nanosized NiCo aerogel catalyst (NiCo) for synthetic natural gas production was investigated in a magnetic fluidized bed (MFB) reactor. The results indicated that the NiCo catalyst showed poor fluidization behavior, while the fluidization quality of the catalyst can be greatly improved by introducing an axial uniform magnetic field. The catalyst in the MFB reactor afforded higher conversion of CO and higher selectivity and yield of CH4 than those in the conventional fluidized bed, which was attributed to the MFB reactor improved gas–solid contract efficiency and inhibited axial back-mixing of the product gas. The catalytic performance in the MFB reactor was quite stable during a 100 h reaction. Such good stability is attributed to the superior property of the catalyst and the improved gas–solid contact efficiency in the MFB reactor. Furthermore, the particle agglomeration was inhibited when the catalyst was explored to a magnetic assisted fluidized bed. The combination of magnetic nanosized catalyst and MFB intensification as a promising route was developed for synthetic natural gas production.
Co-reporter:Jianbo Zhang;Zhaohui Xie
Metallurgical and Materials Transactions B 2013 Volume 44( Issue 4) pp:897-905
Publication Date(Web):2013 August
DOI:10.1007/s11663-013-9863-3
Morphological changes with the phase transitions were investigated in detail for the oxidation roasting of Panzhihua ilmenite in air from 873 K to 1173 K (600 °C to 900 °C). It was found that a thin hematite layer of 1 to 2 μm formed rapidly at the initial stage of the oxidation process, independent of the oxidation temperature, on the surface of ilmenite particles, and the thickness of the hematite layer kept nearly constant with increasing time of oxidation. The morphology inside an ilmenite particle, however, changed with the oxidation temperature. Needlelike rutile network enwrapped by hematite grains was observed after oxidation below 1073 K (800 °C), and the structure can be well preserved during the oxidation process, although grain growth of rutile and hematite did occur with the extension of the oxidation time. The morphological changes at 1073 K (800 °C) and higher showed two distinct stages, where in the first stage ilmenite was oxidized to form rutile and hematite with morphology similar to that of oxidation below 1073 K (800 °C). The as-formed rutile and hematite were not stable and recombined to form pseudobrookite in the second stage, which caused significant morphology change; i.e., the needlelike rutile network gradually “dissolved” to form the final morphology of irregular rutile grains dispersed in the pseudobrookite matrix with some isolated hematite grains. Moreover, the oxidation temperature also has a great effect on the rate of morphological changes, i.e., the increased evolution rate with increasing the oxidation temperature.
Co-reporter:Qingshan Zhu, Rongfang Wu, Hongzhong Li
Particuology 2013 Volume 11(Issue 3) pp:294-300
Publication Date(Web):June 2013
DOI:10.1016/j.partic.2012.10.001
Ultrafine hematite powder was reduced to produce ultrafine iron powder in a 50%Ar–50%H2 atmosphere at 450–550 °C in a fluidized bed reactor. The ultrafine hematite powder shows the typical agglomerating fluidization behavior with large agglomerates fluidized at the bottom of the bed and small agglomerates fluidized at the upper part of the bed. It was found that defluidization occurred even at the low temperature of 450 °C with low metallization rate. Defluidization was attributed mainly to the sintering of the newly formed iron particles. Granuation was employed to improve the fluidization quality and to tackle the defluidization problem, where granules fluidized like a Geldart's group A powder. Granulation was found to effectively reduce defluidization during reduction, without however sacrificing reduction speed. The as-reduced iron powders from both the ultrafine and the granulated hematite exhibited excellent sintering activity, that is, fast sintering at temperature of as low as ∼580 °C, which is much superior as compared to that of nano/ultrafine iron powders made by other processes.Graphical abstractHighlights► Defluidization with raw hematite powder was found to occur at temperature as low as 450 °C. ► Granulation reduces the tendency of defluidization, without sacrificing hematite reduction rate. ► The as-reduced iron powders exhibit excellent sintering activity.
Co-reporter:Yong Wang, Qingshan Zhu, Ling Tao and Xiaowen Su
Journal of Materials Chemistry A 2011 vol. 21(Issue 25) pp:9248-9254
Publication Date(Web):23 May 2011
DOI:10.1039/C1JM10271K
Hierarchical hollow microspheres with nickel sulfide (NiS) nanorods as the in situ formed building blocks have been fabricated via a novel precursor hydrothermal method in alkaline solution of Na2S. In addition, hierarchical hollow microspheres with NiS nanoparticles as the in situ formed building blocks have also been successfully controlled-synthesized through the adjustment of experimental parameters. The NiS powders have been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction and high-resolution transmission electron microscopy. The reported controlled experiments allow us to propose the formation mechanism of nanorod-based NiS hierarchical hollow spheres, which involves sulfuration of Ni(OH)2 precursors and their sequential Ostwald ripening process. When the two kinds of NiS hierarchical hollow spheres prepared herein are used as cathode materials for lithium-ion batteries, nanorod-based hierarchical hollow microspheres exhibit enhanced electrochemical properties as compared with nanoparticle-based hierarchical hollow microspheres. Electrochemical measurements have also shown that the initial discharge capacity of nanorod-based hierarchical hollow microspheres is 587.8 mAh·g−1, which is close to the theoretical capacity of NiS (590 mAh·g−1). The results described in the present work may open up another way for the design of novel nanostructured materials for various applications.
Co-reporter:Yong Wang, Qingshan Zhu and Ling Tao
CrystEngComm 2011 vol. 13(Issue 14) pp:4652-4657
Publication Date(Web):26 May 2011
DOI:10.1039/C1CE05119A
Hierarchical porous Fe3O4 hollow sub-microspheres with nanoparticles as the in situ formed building blocks were fabricated via a novel one-pot solvothermal method. The possible formation mechanism of these hierarchical porous Fe3O4 hollow sub-microspheres was explored. In this formation process, solid Fe2O3 sub-microspheres were first obtained, and then gradually reduced to Fe3O4 sub-microspheres with core/shell structure which finally developed into hierarchical Fe3O4 sub-microspheres with hollow interiors through the Ostwald ripening process. Interestingly, solid α-Fe2O3 sub-microspheres obtained in the initial stage might act as structure director in the formation of Fe3O4 hollow sub-microspheres. Moreover, preliminary results of magnetic properties of the hierarchical porous Fe3O4 hollow sub-microspheres were also reported. The hierarchical porous Fe3O4 hollow sub-microspheres exhibited enhanced saturation magnetization as compared with Fe3O4 single-crystal hollow sub-microspheres with similar sizes and Fe3O4 hollow nanospheres.
Co-reporter:Lin Chen, Qingshan Zhu, Rongfang Wu
International Journal of Hydrogen Energy 2011 Volume 36(Issue 3) pp:2128-2136
Publication Date(Web):February 2011
DOI:10.1016/j.ijhydene.2010.11.042
Co–Ni bimetallic aerogel catalysts with various Co/Ni ratios were synthesized by the sol–gel method followed by the supercritical drying process. The catalysts were characterized by XRD, H2-TPR, HRTEM, BET, TG and FESEM. It showed that the Co/Ni ratio influenced the micro-structure of the Co–Ni bimetallic aerogel catalysts. The formation of homogeneous metal alloy on the bimetallic catalysts was observed after the reduction. In addition, catalysts with higher Co/Ni ratios showed smaller active metal particle sizes. The activities of the aerogel catalysts in terms of CH4 conversion were found to be in the order of 5Co5Ni ≈ 3Co7Ni > 7Co3Ni > 10Ni >> 10Co. 5Co5Ni exhibited the highest CH4 conversion in methane Oxy-CO2 reforming, which is 16% and 55% greater than those of 10Ni and 10Co, respectively. The difference between the catalytic performances could mainly be attributed to the combined effect of the kinetics, the geometric and the SMSI effects.Research highlights► Co–Ni bimetallic aerogel catalysts with various Co/Ni ratios were synthesized. ► Their catalytic performances (in terms of activity and stability) were found to be varying with the change of the Co/Ni ratio. ► This could be attributed to the combined effect of the kinetics, the geometric and the SMSI effects.
Co-reporter:Lin Chen, Qingshan Zhu, Zhigang Hao, Tao Zhang, Zhaohui Xie
International Journal of Hydrogen Energy 2010 Volume 35(Issue 16) pp:8494-8502
Publication Date(Web):August 2010
DOI:10.1016/j.ijhydene.2010.06.003
A novel nano-sized Co–Ni bimetallic aerogel catalyst was synthesized via the sol–gel process followed by the supercritical drying method. The catalyst exhibited at least 28% higher activity and 15% higher H2 selectivity than those of a monometallic cobalt aerogel catalyst in methane oxidative CO2 (Oxy-CO2) reforming. Cold-model experiments revealed that channels were alleviated and the agglomerate size was reduced when the catalyst was applied in a magnetic assisted fluidized bed (MAFB). Owing to the improved fluidization quality of the catalyst in the MAFB reactor, CH4 conversion was raised by 12% and 7% as compared with those in the fixed bed reactor and the conventional fluidized bed reactor, respectively. Furthermore, the catalytic performance was quite stable during a 50 h reaction. This stable performance can be illustrated both by the superior catalytic property of the Co–Ni bimetallic aerogel catalyst and the intensified gas–solid interaction in the MAFB reactor.
Co-reporter:Yong Wang, Qingshan Zhu
Materials Research Bulletin 2010 45(12) pp: 1844-1849
Publication Date(Web):
DOI:10.1016/j.materresbull.2010.09.014
Co-reporter:Lian Peng, QingShan Zhu
Journal of Power Sources 2009 Volume 194(Issue 2) pp:880-885
Publication Date(Web):1 December 2009
DOI:10.1016/j.jpowsour.2009.06.018
Thermal cycle stability is very important for glass seals in planar solid oxide fuel cell (pSOFC) applications. In the present study, thermal cycle stability of a thermally stable sealing glass is investigated using a sealing fixture from 150 °C to 700 °C. SS410 alloy with the TEC (thermal expansion coefficient) of 12.2 × 10−6 K−1 (room temperature to 700 °C) is used to evaluate the effect of TEC mismatch on the thermal cycle stability. The leak rates increase with thermal cycles and appear to be two different stages. Microstructure examinations are performed to investigate the degradation mechanism of the thermal cycle stability. It is found that the sealing glass interacts chemically with the SS410 alloy and the formation of BaCrO4 new phase results in the rapid increase of the leak rates.
Co-reporter:Jinping Liang, Qingshan Zhu, Zhaohui Xie, Wenlai Huang, Chaoquan Hu
Journal of Power Sources 2009 Volume 194(Issue 2) pp:640-645
Publication Date(Web):1 December 2009
DOI:10.1016/j.jpowsour.2009.06.058
Nanocrystalline Ce0.8Gd0.2O1.9 (GDC20) powder was synthesized by ammonia co-precipitation combined with supercritical ethanol drying route, followed by characterizations with TG/DSC, XRD, BET, HR-TEM, and FESEM techniques. After calcination at 600 °C, the powder has a high specific surface area of 146.5 m2 g−1 and an average crystal size of ∼5 nm without hard-agglomeration. The nano-GDC powder showed excellent sinterability, where by pressureless sintering at 900 °C for 4 h, the relative density of more than 98% and average grain size of 84 nm have been attained, which is attributed to the powder's ultrafine nanocrystal size, weak agglomeration and high homogeneity. Investigations indicate that in the initial sintering stage, grain growth behavior is mainly controlled by volume diffusion mechanism with an activation energy of ∼5.4 eV.
Co-reporter:Zhigang Hao, Qingshan Zhu, Zheng Jiang, Baolin Hou, Hongzhong Li
Fuel Processing Technology 2009 Volume 90(Issue 1) pp:113-121
Publication Date(Web):January 2009
DOI:10.1016/j.fuproc.2008.08.004
The CH4-CO2 reforming was investigated in a fluidized bed reactor using nano-sized aerogel Ni/Al2O3 catalysts, which were prepared via a sol–gel method combined with a supercritical drying process. The catalysts were characterized with BET, XRD, H2-TPR and H2-TPD techniques. Compared with the impregnation catalyst, aerogel catalysts exhibited higher specific surface areas, lower bulk density, smaller Ni particle sizes, stronger metal-support interaction and higher Ni dispersion degrees. All tested aerogel catalysts showed better catalytic activities and stability than the impregnation catalyst. Their catalytic stability tested during 48 h reforming was dependent on their Ni loadings. Characterizations of spent catalysts indicated that only limited graphitic carbon formed on the aerogel catalyst, while massive graphitic carbon with filamentous morphology was observed for the impregnation catalyst, leading to significant catalytic activity degradation. An aerogel catalyst containing 10% Ni showed the best catalytic stability and the lowest rate of carbon deposition among the aerogel catalysts due to its small Ni particle size and strong metal-support interaction.
Co-reporter:Chaoquan Hu, Qingshan Zhu, Zheng Jiang
Powder Technology 2009 Volume 194(1–2) pp:109-114
Publication Date(Web):25 August 2009
DOI:10.1016/j.powtec.2009.03.035
Nanosized CuO–ZrxCe1 − xOy (0 ≤ x ≤ 0.5) solid solution oxide catalysts were prepared using a co-precipitation method followed with ethanol supercritical drying and calcination at 800 °C. The structural characteristics and redox behaviors were investigated by using X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, and temperature programmed reduction (H2-TPR). The results revealed that the as-prepared samples not only possessed large specific surface areas, small crystal sizes and high homogeneity of constituents, but also exhibited high catalytic activity for the complete oxidation of benzene. The structural properties and the catalytic performances of the aerogel catalysts strongly depended on the Ce/Zr molar ratio. The most highly active catalyst, CuO–Ce0.5Zr0.5Oy, could oxidize benzene at 300 °C and kept robust in a 50 h long-term duration test, implying it would be a good and cost-effective alternative to noble metal catalysts for the complete oxidation of VOCs at lower temperatures.Nanosized CuO–ZrxCe1 − xOy (0 ≤ x ≤ 0.5) solid solution oxide catalysts were prepared using a co-precipitation method followed with ethanol supercritical drying and calcination at 800 °C. The samples not only possessed large specific surface areas, small crystal sizes and high homogeneity of constituents, but also exhibited high catalytic activity for the complete oxidation of benzene.
Co-reporter:Tao Zhang, Qingshan Zhu, Wen Lai Huang, Zhaohui Xie, Xianshuang Xin
Journal of Power Sources 2008 Volume 182(Issue 2) pp:540-545
Publication Date(Web):1 August 2008
DOI:10.1016/j.jpowsour.2008.04.027
An analytical model is developed to predict the residual thermal stresses in a single cell of solid oxide fuel cells (SOFCs), which consists of a thick porous 8 mol% Y2O3 stabilized zirconia/nickel oxide (8YSZ/NiO) anode, a dense 8YSZ electrolyte and a porous lanthanum strontium manganite (LSM) cathode. The simulated stresses in the cell at room temperature, which are resulted from the contraction mismatch of its components, indicate that the major principal stress in the anode is tensile while the electrolyte and cathode are under compressive stresses. The stress in one component decreases with the increase of its thickness when the thicknesses of the other two components are fixed, and the decrease of the tensile stress in the anode will cause the increase of the compressive stresses in both the cathode and the electrolyte, and vice versa. The analysis also reveals that the anode is the part that is most susceptible to fracture since the tensile thermal stress is so high that it reaches to the fracture strength of the anode material. The Weibull statistic is employed to estimate the failure probability of the anode. The simulation results indicate that the anode failure probability decreases with the increase of the anode thickness and the decrease of the electrolyte thickness. To keep the anode failure probability less than 1E−06, the anode thickness should be greater than 0.7 mm for a cell with an electrolyte thickness of 10 μm and a cathode thickness of 20 μm.
Co-reporter:Chaoquan Hu, Qingshan Zhu, Zheng Jiang, Yayuan Zhang, Yong Wang
Microporous and Mesoporous Materials 2008 Volume 113(1–3) pp:427-434
Publication Date(Web):1 August 2008
DOI:10.1016/j.micromeso.2007.11.043
A simple route has been developed to synthesize mesoporous CuO–CeO2 mixed oxides. X-ray diffraction, N2 adsorption and desorption isotherms, and high-resolution transmission electron microscopy have been used to characterize the obtained mesoporous CuO–CeO2 mixed oxides. The results revealed that the as-prepared CuO–CeO2 mixed oxides possessed a high BET surface area and pores in the range of 1–10 nm after calcination at 600 °C for 4 h. In order to understand the formation mechanism of the mesoporous structure, the precursor before calcination was characterized by FTIR and TG-DSC. The results showed that the formation of the mesoporous structure with the high BET surface area was ascribed to the decomposition of ammonia nitrate. Further experimental investigations revealed that the amount of ammonia nitrate in the precursor greatly influenced the BET surface area and the pore size of the final product. Furthermore, the method could be extended to the synthesis of other mixed oxides with the mesoporous structures, such as ZrO2–CeO2 and ZrO2–Y2O3. The as-prepared mesoporous CuO–CeO2 sample with the high surface area exhibited highly reducible features as compared to the sample with a low surface area. The mesoporous CuO–CeO2 powder showed excellent catalytic activity for the complete oxidation of benzene.
Co-reporter:Zhigang Hao, Qingshan Zhu, Ze Lei, Hongzhong Li
Powder Technology 2008 Volume 182(Issue 3) pp:474-479
Publication Date(Web):10 March 2008
DOI:10.1016/j.powtec.2007.05.024
Ni/Al2O3 aerogel catalysts were synthesized by a sol–gel method combined with a supercritical drying route. The catalytic performances of the catalysts in methane reforming with CO2 were investigated in a quartz micro-reactor. The results indicated that the aerogel catalyst showed higher specific surface area and higher dispersivity of nickel species than those of impregnation catalyst. The excellent catalytic performances and stabilities were achieved over the aerogel catalysts in the fluidized bed reactor. Comprehensive characterization with TG, XRD and FESEM revealed that the aerogel catalyst in the fluidized bed had much lower carbon deposition than that in the fixed bed. The fluidization of the aerogel catalyst greatly improved the contact efficiency of gas–solid phase, which accelerated the gasification of the deposited carbon. In contrast, the deactivation of the aerogel catalyst was caused by the carbon deposition due to the catalyst without moving in the fixed bed. Moreover, decreasing activity of the impregnation catalyst in the fluidized bed resulted from the poor fluidization state of catalyst particles and low effective active sites on surface of catalyst.CO2–CH4 reforming over Ni/Al2O3 aerogel catalysts was investigated in a micro-fluidized bed reactor. The excellent catalytic performances of aerogel catalysts were achieved since only a limited amount of carbon deposited on the surface of catalysts. The fluidization of aerogel catalysts with porous agglomerates was effective to improve the contact efficiency of gas–solid phase, thus less carbon accumulated.
Co-reporter:Yulong Ding, Qingshan Zhu
Powder Technology 2008 Volume 183(Issue 1) pp:1
Publication Date(Web):18 March 2008
DOI:10.1016/j.powtec.2007.11.010
Co-reporter:Zhigang Hao, Qingshan Zhu, Zheng Jiang, Hongzhong Li
Powder Technology 2008 Volume 183(Issue 1) pp:46-52
Publication Date(Web):18 March 2008
DOI:10.1016/j.powtec.2007.11.015
The fluidization characteristics of a nanoparticle catalyst were investigated in a fluidized bed assisted with an axial magnetic field. It showed that slugging and channeling, commonly observed when processing nanoparticles via conventional fluidized bed reactors, could be effectively eliminated, and the size of the agglomerates and bubble diameter could also be reduced with the aid of the magnetic field, leading to much improved gas–solid contact efficiency. Due to the improved gas–solid contact efficiency, the performance of the CH4–CO2 catalytic reforming has been significantly enhanced, where the initial conversion of CH4 was 7.6% and 24.3% higher than those obtained in a conventional fluidized bed reactor and a fixed bed reactor. The catalytic deactivation, caused by carbon deposition on catalyst surfaces, is also slower in the magnetic fluidized bed operation, where the CH4 conversion is 11.7% and 42.6% greater as compared with those in the conventional fluidized bed operation and the fixed bed operation. The present investigations demonstrated that carbon deposition can be much suppressed through improving the gas–solid contact efficiency with the assistance of the magnetic field.The fluidization quality of aerogel Co/Al2O3 catalyst is improved in a fluidized bed assisted with an axial magnetic field. Due to the improved gas–solid contact efficiency, the performance of the CH4–-CO2 catalytic reforming has been significantly enhanced, and the carbon deposition is much suppressed in the magnetic fluidized bed compared with those in a conventional fluidized bed and a fixed bed.
Co-reporter:H. Zhang;Q. Zhu;Y. Zhang;Y. Wang;L. Zhao;B. Yu
Advanced Functional Materials 2007 Volume 17(Issue 15) pp:
Publication Date(Web):11 OCT 2007
DOI:10.1002/adfm.200790051
On p. 2766, Qinshan Zhu and co-workers report on multishell hollow Cu2O microspheres that are synthesized by a facile and one-pot solvothermal route. A two-step organization process, in which hollow microspheres of Cu2(OH)3NO3 are formed first followed by reduction to Cu2O by glutamic acid, leads to the special multishell and hollow microstructures. Interestingly, a Cu2O gas sensor fabricated with the multishell microspheres shows a much higher sensitivity to ethanol than solid Cu2O microspheres.
Hierarchical assembly of hollow microstructures is of great scientific and practical value and remains a great challenge. This paper presents a facile and one-pot synthesis of Cu2O microspheres with multilayered and porous shells, which were organized by nanocrystals. The time-dependent experiments revealed a two-step organization process, in which hollow microspheres of Cu2(OH)3NO3 were formed first due to the Ostwald ripening and then reduced by glutamic acid, the resultant Cu2O nanocrystals were deposited on the hollow intermediate microspheres and organized into finally multishell structures. The special microstructures actually recorded the evolution process of materials morphologies and microstructures in space and time scales, implying an intermediate-templating route, which is important for understanding and fabricating complex architectures. The Cu2O microspheres obtained were used to fabricate a gas sensor, which showed much higher sensitivity than solid Cu2O microspheres.
Co-reporter:H. Zhang;Q. Zhu;Y. Zhang;Y. Wang;L. Zhao;B. Yu
Advanced Functional Materials 2007 Volume 17(Issue 15) pp:
Publication Date(Web):17 AUG 2007
DOI:10.1002/adfm.200601146
Hierarchical assembly of hollow microstructures is of great scientific and practical value and remains a great challenge. This paper presents a facile and one-pot synthesis of Cu2O microspheres with multilayered and porous shells, which were organized by nanocrystals. The time-dependent experiments revealed a two-step organization process, in which hollow microspheres of Cu2(OH)3NO3 were formed first due to the Ostwald ripening and then reduced by glutamic acid, the resultant Cu2O nanocrystals were deposited on the hollow intermediate microspheres and organized into finally multishell structures. The special microstructures actually recorded the evolution process of materials morphologies and microstructures in space and time scales, implying an intermediate-templating route, which is important for understanding and fabricating complex architectures. The Cu2O microspheres obtained were used to fabricate a gas sensor, which showed much higher sensitivity than solid Cu2O microspheres.
Co-reporter:Ze Lei, Qingshan Zhu
Materials Letters 2007 Volume 61(Issue 6) pp:1311-1314
Publication Date(Web):March 2007
DOI:10.1016/j.matlet.2006.07.020
The powders of 89 mol% ZrO2–11 mol% Sc2O3 (11ScSZ) doped with various Mn2O3 contents were prepared by a co-precipitation method combined with a SCFD (supercritical fluid drying) route. Inhibition of the cubic–rhombohedral phase transformation in both oxidation and reduction atmospheres is achieved for 11ScSZ by the addition of 2.0 mol% Mn2O3. The Mn2O3 addition can lower the sintering temperature of 11ScSZ ceramics, and the 11ScSZ–2Mn2O3 compact can be sintered to nearly full density at 850 °C. 11ScSZ–2Mn2O3 ceramic with the cubic structure sintered at 900 °C possesses the conductivity of ∼ 0.10 S cm− 1 at 800 °C, which is very promising for intermediate temperature solid oxide fuel cell (SOFC) applications.
Co-reporter:Hui Gang Zhang, Qingshan Zhu, Yong Wang, Chao Ying Zhang, Ling Tao
Materials Letters 2007 Volume 61(23–24) pp:4508-4511
Publication Date(Web):September 2007
DOI:10.1016/j.matlet.2007.02.038
Inorganic materials with hollow and multilayer structures have attracted many interests because of their special applications. In this paper we reported a low-cost synthetic route for hollow cuprous oxide octahedra with more than one shell. Various characterizations identified the as-obtained powder as pure, uniform, and monodispersed Cu2O octahedra wrapped by the {111} faces. To determine the formation mechanism, the time-dependent experiments were conducted and the results showed that the intermediate phase, CuO, precipitated out first and its reduction by amino acids led to the formation of hollow Cu2O structures.
Co-reporter:Hui Gang Zhang
Journal of Materials Science: Materials in Medicine 2007 Volume 18( Issue 9) pp:1825-1829
Publication Date(Web):2007 September
DOI:10.1007/s10856-007-3036-3
Since pore connectivity has significant effects on the biological behaviors of biomedical porous hydroxyapatite (PHA), the preparation of PHA with interconnected pore architecture is of great practical significance. In the present study, PHA with highly interconnected architecture was prepared via a simple burnout route with rod-like urea as the porogen. Microscopy and porosimetry data showed that the as-prepared PHA had open and interconnected pore structure with the average fenestration size of about 120 μm. Open pores occupied up to 98% of the total porosity. The compressive strength and modulus of the as-prepared PHA were respectively 1.3–7.6 MPa and 4.0–10.4 GPa.
Co-reporter:Yong Wang, Qingshan Zhu and Huigang Zhang
Journal of Materials Chemistry A 2006 vol. 16(Issue 13) pp:1212-1214
Publication Date(Web):2006/02/28
DOI:10.1039/B517176H
Hierarchical porous hollow nickel microspheres with nickel nanoparticles as the in situ formed building units have been fabricated via a novel precursor hydrothermal redox method in alkaline solution of KBH4. The microspheres exhibit enhanced coercivity and remanent magnetization as compared with hollow nickel submicrometer spheres, hollow nickel nanospheres, bulk nickel, and free Ni nanoparticles. Investigations have demonstrated that the enhancement is attributed to the hierarchical porous hollow structure, while the hierarchical structure has little influence on saturation magnetization.
Co-reporter:Ze Lei, Qingshan Zhu, Li Zhao
Journal of Power Sources 2006 Volume 161(Issue 2) pp:1169-1175
Publication Date(Web):27 October 2006
DOI:10.1016/j.jpowsour.2006.06.016
Nanocrystalline La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) powder with a specific surface area of 22.9 m2 g−1 and an average particle size of 175 nm was prepared by a nitrate-glycine solution combustion method and subsequent ball-milling. The LSCF precalcined at 800 °C (LSCF-800) shows very good low-temperature sintering activity, and can well adhere to electrolyte after sintering at 700 °C and above. The single cell Ni–YSZ/YSZ/LSCF-800 with the cathode sintered at 750 °C demonstrates the lowest polarization resistance and good electrical generation performance, but poor cathode microstructure stability. The sintering activity of LSCF cathode can be tailored through the control of the precalcination temperature of the precursor powder. Precalcining of LSCF powder at 900 °C (LSCF-900) increases the optimum sintering temperature of the cathode to 850 °C and improves the microstructure stability. The cell Ni–YSZ/YSZ/LSCF-900 with this cathode demonstrates excellent generation performances with the maximum power density greater than 1.0 W cm−2 and the power density of above 0.80 W cm−2 at 0.7 V under operation at 700 °C. Low temperature processing of the interlayer-free LSCF cathode with good microstructure is beneficial to simplifying the cell structure and improving fuel cell performance.
Co-reporter:Qingshan Zhu, Tongan Jin, Yong Wang
Solid State Ionics 2006 Volume 177(13–14) pp:1199-1204
Publication Date(Web):May 2006
DOI:10.1016/j.ssi.2006.04.029
Perovskite oxides of the composition BaxSr1−xCo1−yFeyO3−δ(BSCF) were synthesized via a modified Pechini method and characterized by X-ray diffraction, dilatometry and thermogravimetry. Investigations revealed that single-phase perovskites with cubic structure can be obtained for x ≤ 0.6 and 0.2 ≤ y ≤ 1.0. The as-synthesized BSCF powders can be sintered in several hours to nearly full density at temperatures of over 1180 °C. Thermal expansion curves of dense BSCF samples show nonlinear behavior with sudden increase in thermal expansion rate between about 500 °C and 650 °C, due mainly to the loss of lattice oxygen caused by the reduction of Co4+ and Fe4+ to lower valence states. Thermal expansion coefficients (TECs) of BSCF were measured to be 19.2–22.9 × 10− 6 K− 1 between 25 °C and 850 °C. Investigations showed further that Ba0.5Sr0.5Co0.8Fe0.2O3−δ is chemically compatible with 8YSZ and 20GDC for temperatures up to 800 °C, above which severe reactions were detected. After being heat-treated with 8YSZ or 20GDC for 5 h above 1000 °C, Ba0.5Sr0.5Co0.8Fe0.2O3−δ was completely converted to phases like SrCoO3−δ, BaCeO3, BaZrO3, etc.
Co-reporter:Yong Wang, Qingshan Zhu and Huigang Zhang
Chemical Communications 2005 (Issue 41) pp:5231-5233
Publication Date(Web):20 Sep 2005
DOI:10.1039/B508807K
Ni(OH)2 hollow microspheres with β-Ni(OH)2 nanosheets as the in situ formed building units were fabricated via a novel template-free approach in a strong alkaline solution of glycine, and can be converted into NiO hollow microspheres by a thermal decomposition process.
Co-reporter:Hui Gang Zhang, Qingshan Zhu
Materials Letters 2005 Volume 59(24–25) pp:3054-3058
Publication Date(Web):October 2005
DOI:10.1016/j.matlet.2005.05.019
Fluoride-substituted hydroxyapatite (FHAp) nanorods have been successfully prepared by adding Tween80. As compared to the spheroidal morphology without any surfactant, the FHAp nanorods prepared with Tween80 were elongated along the c-axis. The reason was attributable to the enlarged difference between the growth rates of crystal surfaces due to the adsorption of Tween80. The effects of the pH value on the apatite formation were investigated by calculating the solubility isotherms of the Ca2+–PO43−–F−–H2O system in conjunction with experimental results, and it was found that acidic solutions were unfavorable to FHAp preparation and the proper pH should be controlled at about 9 when preparing the FHAp nanorods with the addition of Tween80.
Co-reporter:Ze Lei, Qingshan Zhu
Solid State Ionics 2005 Volume 176(37–38) pp:2791-2797
Publication Date(Web):30 November 2005
DOI:10.1016/j.ssi.2005.09.005
Nanocrystalline scandia-doped zirconia (ScSZ) ceramics with a relative density of above 96% and an average grain size of ∼80 nm were prepared via pressureless sintering at 900 °C for 4 h in air. The starting powder synthesized by co-precipitation combined with supercritical fluid drying route is highly homogeneous and weakly agglomerated with crystallite size about 3 nm and specific surface area of 378 m2/g, and can be uniaxially pressed into highly homogeneous compacts. The excellent sinterability achieved in this work is mainly attributed to the small crystallite size with high surface area and the weak agglomeration. The very low sintering temperature achieved in the present work is of practical significance for suppressing the cubic phase to β-phase transition to some degree, eliminating the discontinuity in electrical conductivity and facilitating co-firing the ZrO2-based electrolytes with other SOFCs (solid oxide fuel cells) components.
Co-reporter:Qingshan Zhu;Gijsbertus de With;Leonardus J. M. G. Dortmans;Frits Feenstra
Journal of Biomedical Materials Research Part B: Applied Biomaterials 2003 Volume 65B(Issue 2) pp:233-238
Publication Date(Web):2 APR 2003
DOI:10.1002/jbm.b.10007
The purpose of this study is to investigate the subcritical crack growth (SCG) behavior of alumina-glass dental composites. Alumina-glass composites were fabricated by infiltrating molten glass to porous alumina preforms. Rectangular bars of the composite were subject to dynamic loading in air, with stressing rates ranging from 0.01 MPa/s to 2 MPa/s. The SCG parameter n was determined to be 22.1 for the composite, which is substantially lower than those of high-purity dense alumina. Investigations showed that glass phases are responsible for the low n value as cracks propagate preferentially within glass phases or along the interface between glass phases and alumina phases, due to the fact that glasses are more vulnerable to chemical attacks by water molecules under stress corrosion conditions. The SCG behavior of the infiltration glass was also investigated and the SCG parameter n was determined to be 18.7. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 65B: 233–238, 2003
Co-reporter:Baolin HOU, Haiying ZHANG, Hongzhong LI, Qingshan ZHU
Chinese Journal of Chemical Engineering (February 2012) Volume 20(Issue 1) pp:10-17
Publication Date(Web):1 February 2012
DOI:10.1016/S1004-9541(12)60357-7
Kinetics parameters of iron oxide reduction by hydrogen were evaluated by the isothermal method in a differential micro-packed bed. Influence of external diffusion, internal diffusion and heat transfer on the intrinsic reaction rate was investigated and the conditions free of internal and external diffusion resistance have been determined. In the experiments, in order to correctly evaluate the intrinsic kinetics parameters for reducing Fe2O3 to Fe3O4, the reaction temperatures were set between 440 °C and 490 °C. However, in order to distinguish the reduction of Fe3O4 to FeO from that of FeO to Fe, the reaction temperature in the experiment was set to be greater than 570 °C. Intrinsic kinetics of iron oxide reduction by hydrogen was established and the newly established kinetic models were validated by the experimental data.
Co-reporter:Chaoquan Hu, Qingshan Zhu, Zheng Jiang, Lin Chen, Rongfang Wu
Chemical Engineering Journal (15 October 2009) Volume 152(Issues 2–3) pp:583-590
Publication Date(Web):15 October 2009
DOI:10.1016/j.cej.2009.05.033
CuxCe1−xOy (x = 0.06, 0.13, and 0.23) were prepared by a solution combustion route using glycine as the fuel and tested for the catalytic combustion of dilute acetone in air. The structural characteristics of the catalysts were investigated by specific surface area, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and temperature-programmed reduction (TPR) techniques. The results reveal that the state of the CuO depends on the Cu/Ce molar ratio in the catalyst, which strongly influences the redox behavior and the catalytic activity of the sample. Among the three catalysts, Cu0.13Ce0.87Oy was found to be the most active in the catalytic combustion of acetone. The pulse reaction of pure acetone in the absence of O2 over the Cu0.13Ce0.87Oy catalyst indicated the participation of lattice oxygen from the catalyst in the acetone combustion. Furthermore, the effect of the acetone concentration and the gas hourly space velocity (GHSV) on the catalytic behavior of the catalyst was examined. The stability of the Cu0.13Ce0.87Oy catalyst for acetone combustion was also investigated and an obvious deactivation was observed under the reactant stream for 35 h at 260 °C. XRD analysis of the deactivated catalyst showed that the formation of bulk CuO was responsible for the deactivation of the catalyst.
Co-reporter:Baolin Hou, Hailong Tang, Haiying Zhang, Guoqiang Shao, Hongzhong Li, Qingshan Zhu
Chemical Engineering Science (11 October 2013) Volume 102() pp:354-364
Publication Date(Web):11 October 2013
DOI:10.1016/j.ces.2013.06.050
•Cluster phase plays a key role in gas-solid transport phenomena in CFB.•Mass transfer in CFB is dominated by mass exchange between meso-scales.•The MSMT model can capture the effect of meso-scale cluster in CFB.Catalytic oxidation of carbon monoxide over a Pt catalyst was employed as a model reaction to investigate the effect of meso-scale structure on gas-solid mass transfer in a circulating fluidized bed (CFB). Both experimental and theoretical analyses were performed to determine the conditions under which the reaction process was dominated by mass transfer. The experimental works involved the measurements of the axial distribution of carbon monoxide concentration, whereas the theoretical analyses were on the use of an Multi-Scale Mass Transfer (MSMT) model with considering effects of clusters on gas-solid transport phenomena in the CFB. The results of MSMT model show a good agreement with experimental data, suggesting that the particle clusters play an important role in the gas-solid momentum transfer and mass transfer in CFBs.
Co-reporter:Tao Zhang, Qingshan Zhu, Zhaohui Xie
Journal of Power Sources (1 March 2009) Volume 188(Issue 1) pp:177-183
Publication Date(Web):1 March 2009
DOI:10.1016/j.jpowsour.2008.11.053
For planar SOFCs the seal is a critical component, potential fracture in the seal needs to be investigated in order to enhance the reliability of the seal. A model based on the classical beam bending theory and the fracture theory of ceramic materials has been developed for predicting the crack extension in the seal. The model reveals that the resistance of the seal to cracking on cooling is mainly affected by two factors: the seal thickness and the CTE mismatch. Furthermore, a cracking diagram is established to reveal the effects of the seal thickness and CTE mismatch on the crack extension behavior. It shows that the ‘no cracking’ area increases with decreasing seal thickness, and larger CTE mismatch requires a thinner seal to avoid cracking. The model and the cracking diagram are experimentally validated through monitoring the leakage rate of a glass-sealed chamber, and the crack extension deduced from the measured leakage rate shows good agreement with those predicted by the model. The proposed model can serve as a useful tool in sealing design of SOFC.
Co-reporter:Li Li, Jianbo Zhang and Qingshan Zhu
Dalton Transactions 2016 - vol. 45(Issue 7) pp:NaN2896-2896
Publication Date(Web):2015/12/22
DOI:10.1039/C5DT04091D
Meso/macroporous TiO2–Fe2O3 composite particles are prepared using naturally abundant ilmenite via a novel heat treatment induced fractional crystallization strategy in a fluidized bed. Fluid-bed roasting in oxidizing and reducing environments is carried out in order to realize the fractional crystallization of ilmenite. Subsequently, acid leaching is employed to remove most of the ferrous phase and form porous TiO2–Fe2O3 composites. The influences of the reaction parameters on the composition, structure and properties of the products are studied. It is found that the pore structure and composition of the porous TiO2–Fe2O3 composite particles can be controlled simply by controlling some parameters, such as the roasting time, temperature, precursor particle size, and post-roasting treatment. Photocatalytic and electrochemical cycling measurements show that the synergism of porous structures and the controlled doping of α-Fe2O3 endow the as-obtained products with excellent visible light photocatalytic activity and provide enhanced performance in lithium ion batteries. The composite porous particles thus obtained may have some promising applications in the fields of photocatalysts, electrode materials, absorbers, pigments etc. This work opens a new avenue for reasonable combination of cost-effective raw materials, a large scale fabricating process and fine control over the structure and composition in the design and preparation of functional materials.
Co-reporter:Yong Wang, Qingshan Zhu, Ling Tao and Xiaowen Su
Journal of Materials Chemistry A 2011 - vol. 21(Issue 25) pp:NaN9254-9254
Publication Date(Web):2011/05/23
DOI:10.1039/C1JM10271K
Hierarchical hollow microspheres with nickel sulfide (NiS) nanorods as the in situ formed building blocks have been fabricated via a novel precursor hydrothermal method in alkaline solution of Na2S. In addition, hierarchical hollow microspheres with NiS nanoparticles as the in situ formed building blocks have also been successfully controlled-synthesized through the adjustment of experimental parameters. The NiS powders have been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction and high-resolution transmission electron microscopy. The reported controlled experiments allow us to propose the formation mechanism of nanorod-based NiS hierarchical hollow spheres, which involves sulfuration of Ni(OH)2 precursors and their sequential Ostwald ripening process. When the two kinds of NiS hierarchical hollow spheres prepared herein are used as cathode materials for lithium-ion batteries, nanorod-based hierarchical hollow microspheres exhibit enhanced electrochemical properties as compared with nanoparticle-based hierarchical hollow microspheres. Electrochemical measurements have also shown that the initial discharge capacity of nanorod-based hierarchical hollow microspheres is 587.8 mAh·g−1, which is close to the theoretical capacity of NiS (590 mAh·g−1). The results described in the present work may open up another way for the design of novel nanostructured materials for various applications.
