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Relationship between surface area and crystal size of pure and doped cerium oxides

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Journal of Rare Earths 2010年第5期28卷 647-653页

作者： C. Bueno-Ferrer S. Parres-Esclapez D. Lozano-Castelló A. Bueno-López Analytical Chemistry Nutrition & Food Sciences Department Inorganic Chemistry Department University of Alicante Ap. 99 E-03080 Alicante Spain

Pure and Zr, La or Pr-doped cerium oxides were characterised by transmission electron microscopy (TEM), N2 adsorption-desorption at –196 oC and X-ray diffraction (XRD). For crystal sizes calculation, the Scherrer and Williamson-Hall equations were compared, and the relationship between surface area and crystal size was critically discussed. It was demonstrated that the Williamson-Hall equation must be used instead of the Scherrer equation to calculate crystal sizes, since the latter equation underestimated ...

关键词： ceria XRD N2 adsorption crystal size surface area rare earths

Effects of initial crystal size of diamond powder on surface residual stress and morphology in polycrystalline diamond (PCD) layer

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Science China(Physics,Mechanics & Astronomy) 2011年第1期54卷 98-101页

作者： JIA HongSheng JIA XiaoPeng XU Yue WAN LianRu JIE KaiKai MA HongAn State Key Laboratory of Superhard Materials Jilin University Changchun 130012 China Test Science Experiment Center Jilin University Changchun 130021 China

Polycrystalline diamond compacts (PDC) were synthesized using diamond powder of average crystal size 3-20 μm by the Ni 70 Mn 25 Co 5 alloy infiltration technique at high temperature and high pressure (HPHT).The surface residual stress of polycrystalline diamond (PCD) layer was measured using micro-Raman spectroscopy with hydrostatic stress model and X-ray diffraction (XRD).Measurements of the stress levels of PCDs show that the residual compressive stresses range from 0.12 to 0.22 GPa,which increase with the crystal size of *** electron microscopy (SEM) was used to observe the morphology of initial diamond grains and PCD *** results indicate that PCD has a dense and interlaced microstructure with diamond-diamond (D-D) direct *** the smaller the crystal size of diamond,the better the growth of diamond direct bonding and the smaller the binder metal between diamond boundaries will be.

关键词： HPHT polycrystalline diamond (PCD) crystal size residual stress morphology

Differences in Adsorption of Anionic Surfactant AOT by Calcium Oxalate： Effect of crystal size and crystalline Phase

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Chemical Research in Chinese Universities 2016年第4期32卷 682-688页

作者： SkIN Xinyuan DING Yiming WEN Xiaoling OUYANG Jianming Institute of Biomineralization and Lithiasis Research Jinan University Guangzhou 510632 P. R. China

The adsorption of anionic surfactant sodium diisooctyl sulfosuccinate（AOT） onto calcium oxalate mono- hydrate（COM） and dihydrate（COD） with sizes of 50, 100 nm, 1, 3 and 10 μm was comparatively studied to simulate the interaction between urinary crystallites and urine components. The adsorption quantity of different concentrations of AOT onto COD and COM with different sizes was detected using a UV-Vis spectrophotometer. The crystalline phase transition of COM and COD before and after adsorption was analyzed by X-ray powder diffraction and Fourier transform infrared spectrometry. The zeta potential of the crystal surface after adsorption of different concentrations of AOT was measured using a zeta potential analyzer. The adsorption quantity of AOT on COM and COD with different sizes was ranked in the following order： 50 nm〉100 nm〉1μm〉3 μm〉10 μm. The adsorption quantity of COM was greater than that of COD with the same size because the density of the positive charges on the COM surface was higher than that on COD surface. With the increase of AOT concentration, the adsorption curves of the large-sized COM and COD（3 and 10μm） were S-type, whereas the adsorption curves of the small-sized COM and COD（50 nm, 100 nm and 1μm） were linear. The adsorption capacities of small-sized COM and COD were much greater than those of the 3 and 10μm crystals. On the basis of the above results, we proposed a molecular model to summarize the absorption of AOT onto COM and COD crystals. Small crystals exhibit a large specific surface area and high surface energy. Thus, the adsorption capacities of them are stronger than those of large crystals. Overall, this study implies that small crystals can easily absorb anionic molecules in urine and may easily adhere to a negatively charged cell surface, thereby increasing the severity of cell injury.

关键词： crystal size Calcium oxalate Anionic surfactant Surface adsorption Adsorption model

Influence of crystal size of USY Zeolite on Performance of Hydro-upgrading Catalysts

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China Petroleum Processing & Petrochemical Technology 2012年第1期14卷 32-36页

作者： Wang Fucun Zhu Jinling Yan Zifeng State Key Laboratory of Heavy Oil Processing CNPC Key Laboratory of Catalysis China University of Petroleum Qingdao 266580 Daqing Petrochemical Research Center of PetroChina Daqing 163714

The effect of crystal size of USY zeolite on the performance of hydro-upgrading catalysts for treating catalytically cracked(FCC) LCO(light cycle oil) was *** W-Ni catalysts supported on USY zeolites with different crystal sizes and Al2O3 were prepared by impregnation *** catalysts were characterized by XRD and BET methods,and evaluated in a micro-reactor using tetralin as the model compound and in an 100-mL hydrogenation test unit using FCC LCO as the *** contrast,catalyst made from smaller crystal-size USY zeolite had higher external surface area and shorter pore length,having more hydrogenation activity sites and short contact time of reactant molecules with acidity *** evaluation results showed that the catalyst prepared on the basis of small crystal-size USY zeolite had higher tetralin conversion and better hydro-upgrading performance for treating FCC LCO.

关键词： crystal size USY hydro-upgrading catalyst

Correlation between H-ZSM-5 crystal size and catalytic performance in the methanol-to-aromatics reaction

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Chinese Journal of Catalysis 2017年第4期38卷 683-690页

作者： Lingzhi Yang Zhiyuan Liu Zhi Liu Wenyong Peng Yunqi Liu Chenguang Liu State Key Laboratory of Heavy Oil Processing College of Chemical Engineering China University of Petroleum (East China) Qingdao 266580 ShandongChina

The porosity of H‐ZSM‐5zeolite is known to facilitate the diffusion of molecules in the methanol‐to‐aromatics(MTA)*** activity and selectivity of the H‐ZSM‐5catalyst in the MTAreaction has been studied as a function of crystal ***‐5zeolites with different crystal sizeswere successfully synthesized by conventional hydrothermal *** ZSM‐5particle sizewas easily controlled by changes to the sol‐gel composition,and in particular,the deionized waterto tetrapropylammonium hydroxide ratio,and crystallization *** structure of the H‐ZSM‐5zeolites were characterized by X‐ray diffraction and the morphology of the zeolite particles wasdetermined by scanning electron microscopy.N2adsorption‐desorption measurements establishedchanges to the textural properties,and compositional properties were characterized by X‐ray *** measurements of the catalysts were measured by pyridine‐adsorbedFourier transform infrared spectroscopy and the temperature‐programmed desorption of *** subjecting the catalysts to the MTA reaction,the total amount of coke formed on the spentdeactivated catalysts was determined by thermal gravimetric *** results show that theSiO2/Al2O3molar ratios and acidic properties of the H‐ZSM‐5samples are similar,however,thenano‐sized hierarchical ZSM‐5zeolite with an additional level of auxiliary pores possesses a higher

关键词： Methanol Aromatics Nano‐sized H‐ZSM‐5 Hierarchical structure crystal size

Fabrication of a nano-sized ZSM-5 zeolite with intercrystalline mesopores for conversion of methanol to gasoline

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Journal of Energy Chemistry 2017年第1期26卷 139-146页

作者： Tingjun Fu Jiangwei Chang Juan Shao Zhong Li Key Laboratory of Coal Science and Technology Ministry of Education and Shanxi ProvinceTaiyuan University of TechnologyTaiyuan 030024ShanxiChina

Carbon deposition during methanol to hydrocarbons leads to the quick deactivation of ZSM-5 catalyst and it is one of the major problems for this technology. Decreasing the crystal size or introducing mesopores into ZSM-5 zeolites can improve its diffusion property and decrease the coke formation. In this paper, nano-sized ZSM-5 zeolite with intercrystalline mesopores combining the mesoporous and nano sized structure was fabricated. For comparison, the mesoporous ZSM-5 and nano-sized ZSM-5 were also prepared. These catalyst samples were characterized by XRD, BET, NH3-TPD, TEM, Py-IR and TG techniques and used on the conversion of methanol to gasoline in a fixed-bed reactor at T=405 degrees C, WHSV =4.74 h(-1) and P=1.0 MPa. It was found that the external surface area of the nano-sized ZSM-5 zeolite with intercrystalline mesopores reached 104 m(2)/g, larger than that of mesoporous ZSM-5 (66 m(2)/g) and nano sized ZSM-5 (76 m(2)/g). Catalytic lifetime of the nano-sized ZSM-5 zeolite with intercrystalline mesopores was 93 h, which was only longer than that of mesoporous ZSM-5 (86 h), but shorter than that of nano sized ZSM-5 (104 h). Strong acidity promoted the coke formation and thus decreased the catalytic lifetime of the nano-sized ZSM-5 zeolite with intercrystalline mesopores though it presented large external surface that could improve the diffusion property. The special zeolite catalyst was further dealuminated to decrease the strong acidity. After this, its coke formation rate was slowed and catalytic lifetime was prolonged to 106 h because of the large external surface area and decreased weak acidity. This special structural zeolite is a potential catalyst for methanol to gasoline reaction. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

关键词： ZSM-5 crystal size Mesopore Acidity Methanol to gasoline

Preparation of large In(OH)3 and In2O3 particles through a seed-mediated growth method in a microreactor

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Particuology 2020年第2期18卷 1-8页

作者： Jingchuo Wang Shaoqing Bai Yujun Wang Guangsheng Luo Tao Wang State Key Laboratory of Chemical Engineering Department of Chemical EngineeringTsinghua UniversityBeijing 100084China

Indium hydroxide(ln(OH)3)and indium oxide(ln2O3)particles are typically synthesized through chemical precipitation *** this study,we used a seed-mediated growth method and microreactor-based synthesis *** synthesized cubic In(OH)3 particles with a crystal size of 172 nm from an 5%(w/v)indium chloride *** In2O3 particles synthesized through the thermal decomposition of In(OH)3 particles featured crystals up to 90 nm in size with an average size of 73 nm,which were much larger than the 20-30 nm In2O3 particles synthesized by a traditional precipitation *** concentrations of the seed and growth solutions were varied from 1%to 7%(w/v).The crystal size of the particles increased with the concentration of the seed and growth solutions;this tendency was the opposite to that observed for the precipitation *** the use of a 5%(w/v)seed solution,the flow rate of the growth solution was varied from 1 to 10mL/min,and the resulting crystal size decreased as the flow rate was *** understand the reasons for this trend,the growth rate of the crystals was determined at different flow rates(i.e.,1,5,and 10 mL/min).A growth model consistent with the experimental results was established,which demonstrated that slow addition of the growth solution was beneficial for preparing large indium hydroxide particles.

关键词： Indium hydroxide Indium oxide Growth model crystal size Seed-mediated growth

Inhibition effect of phosphate on the crystal grain growth of nanosized titania

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Rare Metals 2009年第4期28卷 385-390页

作者： FENG Xiaohui LIU Jingze LI Ping ZHANG Yanfeng WEI Yu College of Chemistry and Material Science Hebei Normal University Shijiazhuang 050016 China College of Life Science Hebei Normal University Shijiazhuang 050016 China

The inhibitory effect of phosphate on the crystal grain growth of nanosized titania during high temperature calcination was investigated. Nanosized titanium dioxide powders prepared by hydrolysis of titanium tetrachloride were soaked in phosphate solutions with different concentrations. The obtained powders calcined at various temperatures were characterized by X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR）, and X-ray photoelectronic spectroscopy （XPS）. The grain size of the samples without phosphate treatment increased quickly when calcined at high temperatures, while the grain size of the samples with phosphate modification increased slowly when calcined at the same temperature. This phenomenon implies that phosphate treatment plays an important role in inhibiting the crystal grain growth of titania. The possible mechanism of the inhibition effect of phosphate on titania is discussed.

关键词： physical chemistry crystal size soaking method nanosized TiO2 phosphate

Investigation on Bioactivity of Titanium DioXide Thin Films Fabricated by Electron Cyclotron Resonance Plasma Aided Pulsed Laser Deposition

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Plasma Science and Technology 2009年第4期11卷 477-480页

作者：束奇伟钟晓霞吴嘉达孙剑 Kostya(Ken) OSTRIKOV Department of Physics Shanghai Jiao Tong University Department of Optical Science and Engineering Fudan University Plasma Nanoscience Center Australia(PNCA) CSIRO Materials Science and Engineering

Titanium dioxide thin films with a rutile crystallinite size around 20 nm were fabri- cated by pulsed laser deposition （PLD） aided with an electron cyclotron resonance （ECR） plasma. With annealing treatment, the crystal size of the rutile crystallinite increased to 100 nm. The apatite-forming ability of the films as deposited and after annealing was investigated in a kind of simulated body fluid with ion concentrations nearly equal to those of human blood plasma. The results indicate that ECR aided PLD is an effective way both to fabricate bioactive titanium dioxide thin films and to optimize the bioactivity of titanium dioxide, with both crystal size and defects of the film taken into account.

关键词： titanium dioxide PLD bioactivity surface defect crystal size