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Directionally solidified Al2O3/GAP eutectic ceramics by micro-pulling-down method

AIP Conference Proceedings 2016年第1期1783卷

作者： Xue Cao Haijun Su Fengwei Guo Xi Tan Lamei Cao 1Science and Technology on Advanced High Temperature Structural Materials Laboratory Beijing Institute of Aeronautical Materials Beijing 100095 China 2State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi’an 710072 China

We reported a novel route to prepare directionally solidified (DS) Al2O3/GAP eutectic ceramics by micro-pulling-down (μ-PD) method. The eutectic crystallizations, microstructure characters and evolutions, and their mechanical properties were investigated in detail. The results showed that the Al2O3/GAP eutectic composites can be successfully fabricated through μ-PD method, possessed smooth surface, full density and large crystal size (the maximal size: φ90 mm × 20 mm). At the process of Diameter, the as-solidified Al2O3/GAP eutectic presented a combination of “Chinese script” and elongated colony microstructure with complex regular structure. Inside the colonies, the rod-type or lamellar-type eutectic microstructures with ultra-fine GAP surrounded by the Al2O3 matrix were observed. At an appropriate solidificational rate, the binary eutectic exhibited a typical DS irregular eutectic structure of “chinese script” consisting of interpenetrating network of α-Al2O3 and GAP phases without any other phases. Therefore, the interphase spacing was refined to 1–2 µm and the irregular microstructure led to an outstanding vickers hardness of 17.04 GPa and fracture toughness of 6.3 MPa × m1/2 at room temperature.

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Oxidation Behaviors of C-ZrB_2-SiC Composite at 2100℃ in Air and O_2

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Journal of materials Science & technology 2014年第12期30卷 1223-1229页

作者： Zhongwei Zhang Cewen Nan Jingjun Xu Zenghua Gao Meishuan Li Junshan Wang State Key Laboratory of New Ceramics & Fine Processing Department of Materials Science and Engineering Tsinghua University Science and Technology on Advanced Functional Composites Laboratory Aerospace Research Institute of Materials and Processing Technology Institute of Metal Research Chinese Academy of Sciences

The oxidation behaviors of graphite and ZrB2-SiC modified graphite composite were investigated at 2100℃ in1X105 Pa air and 0.2X105 Pa O2. The oxidation tests were conducted in an induction heating furnace. The oxidation of these two materials followed the linear rate law. The determined radius loss rates of graphite and C-ZrB2-Si C at 2100℃ were 2.18X10-2and 1.05X10-2%/s in 1X105 Pa air, and 3.23X10 2 and 2.21X10 2%/s in 0.2X105 Pa O2, respectively. The incorporation of ZrB2 and SiC decreased remarkably the oxidation rate of graphite because the oxide scale formed on the sample surface during oxidation helps in reducing the exposed surface area of the underneath substrate. In two different atmospheres with the same oxygen partial pressure, both graphite and ZrB2-SiC experienced more severe oxidation at 2100℃ in0.2X105 Pa O2than in 1X105 Pa air. The oxidation rate-controlling step for graphite and ZrB2-SiC was proposed to be the inward diffusion of oxygen through the boundary layer and through the pores in the oxide scale, respectively. A model based on diffusion theory was established to discuss the effect of the total gas pressure on their oxidation behaviors.

关键词： Graphite-based composite Ceramic particles Ultra-high temperature oxidation Oxide scale Oxidation mechanism

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Chemical equilibrium controlled synthesis of polyoxymethylene dimethyl ethers over sulfated titania

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Journal of Energy Chemistry 2015年第2期24卷 239-244页

作者： Huaju Li Huanling Song Feng Zhao Liwei Chen Chungu Xia Laboratory for Nano-Catalytic Material & Technology Division of Advanced Nano?materials Suzhou Institute of Nano-Tech and Nano-BionicsChinese Academy of Sciences State Key Laboratory for Oxo Synthesis and Selective Oxidation Lanzhou Institute of Chemical Physics Chinese Academy of Sciences i-Lab Suzhou Institute of Nano-Tech and Nano-Bionics Chinese Academy of Sciences

The chemical equilibrium and reaction kinetic behavior in the synthesis of polyoxymethylene dimethyl ethers （DMMn） were investigated over sulfated titania in order to reveal the decisive factor controlling the reaction. The results showed that the molar ratio of adjacent DMMn products in equilibrium solution had the same value, which depended absolutely on the reaction temperature. Meanwhile, the reactions had the same DMMn products distributions under varied reaction conditions. The equilibrium constants of the related step-wise reactions for DMMn formation were equal, which were calculated based on the bulk compositions of the reaction solution. And thus, the selectivity to DMMn was mainly controlled by the chemical equilibrium, i.e., thermodynamic control. In brief, the present results provide some guidance for future synthesis of DMMn.

关键词： polyoxymethylene dimethyl ethers sulfated titania chemical equilibrium reaction kinetic molar ratio

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Novel 3DOM BiVO4/TiO2 nanocomposites for highly enhanced photocatalytic activity

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Journal of materials Chemistry A 2015年第42期3卷 21244-21256页

作者： Zalfani, Meryam Van Der Schueren, Benoit Hu, Zhi-Yi Rooke, Joanna C. Bourguiga, Ramzi Wu, Min Li, Yu Van Tendeloo, Gustaaf Su, Bao-Lian 61 rue de Bruxelles NamurB-5000 Belgium Laboratoire de Physique des Matériaux: Structure et Propriétés Groupe Physique des Composants et Dispositifs Nanométriques Faculté des Sciences de Bizerte University of Carthage Jarzouna-Bizerte7021 Tunisia University of Antwerp Groenenborgerlaan 171 AntwerpB-2020 Belgium State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Luoshi Road 122 WuhanHubei430070 China Department of Chemistry and Clare Hall College University of Cambridge Lensfield Road Cambridge United Kingdom

Novel 3DOM BiVO4/TiO2 nanocomposites with intimate contact were for the first time synthesized by a hydrothermal method in order to elucidate their visible-light-driven photocatalytic performances. BiVO4 nanoparticles and 3DOM TiO2 inverse opal were fabricated respectively. These materials were characterized by XRD, XPS, SEM, TEM, N2 adsorption-desorption and UV-vis diffuse (UV-vis) and photoluminescence spectroscopies. A references for comparison, a physical mixture of BiVO4 nanoparticles and 3DOM TiO2 inverse opal powder (0.08:1), and a BiVO4/P25 TiO2 (0.08:1) nanocomposite made also by the hydrothermal method were prepared. The photocatalytic performance of all the prepared materials was evaluated by the degradation of rhodamine B (RhB) as a model pollutant molecule under visible light irradiation. The highly ordered 3D macroporous inverse opal structure can provide more active surface areas and increased mass transfer because of its highly accessible 3D porosity. The results show that 3DOM BiVO4/TiO2 nanocomposites possess a highly prolonged lifetime and increased separation of visible light generated charges and extraordinarily high photocatalytic activity. Owing to the intimate contact between BiVO4 and large surface area 3DOM TiO2, the photogenerated high energy charges can be easily transferred from BiVO4 to the 3DOM TiO2 support. BiVO4 nanoparticles in the 3DOM TiO2 inverse opal structure act thus as a sensitizer to absorb visible light and to transfer efficiently high energy electrons to TiO2 to ensure long lifetime of the photogenerated charges and keep them well separated, owing to the direct bandgap of BiVO4 of 2.4 eV, favourably positioned band edges, very low recombination rate of electron-hole pairs and stability when coupled with photocatalysts, explaining the extraordinarily high photocatalytic performance of 3DOM BiVO4/TiO2 nanocomposites. It is found that larger the amount of BiVO4 in the nanocomposite, longer the duration of photogenerated charg

关键词： Bismuth compounds

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Interstitial Solution Carbon Concentration and Defects of Ti+Nb ULC-BH Steel by Internal Friction and Positron Annihilation Methods

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Journal of Iron and Steel Research International 2014年第1期21卷 91-97页

作者： Ji-ping CHEN Yong-lin KANG School of Metallurgical Engineering Key Laboratory of Metals and Processing of Anhui Province Anhui University of Technology School of Materials Science and Engineering State Key Laboratory for Advanced Metals and MaterialsUniversity of Science and Technology Beijing

The interstitial solution carbon concentration and defects in continuously annealed Ti＋Nb bearing ULC- BH （ultra-low carbon bake hardening） steel samples are investigated by multi-functional internal friction apparatus, positron annihilation lifetime spectroscopy （PALS） and coincidence Doppler broadening spectroscopy （CDBS）. The relationship of internal friction peaks, interstitial solution carbon concentrations and movable dislocations in the sam- ples under different conditions is analyzed. A correlation of lifetime component v~ values with interstitial solution car- bon concentrations in the samples for different continuous annealing processes is established, while a correlation of li- fetime component r2 values with multi-vacancies, vacancy clusters, microvoids and other types of defects for various continuous annealing processes is also demonstrated. Furthermore, the average lifetime results illustrate the overall defect densities for various continuous annealing processes. The CDBS analysis reflects the chemical surroundings of the defects at the annihilation sites and reveals that the peak heights of the ratio curves relate to the total number of defects such as interstitial carbon atoms, dislocations, vacancies and other types of defects. The results show that in- ternal friction, PALS and CDBS are effective techniques to identify and characterize the interstitial solution carbon concentration, multi-vacancies, vacancy clusters, microvoids and other types of microscopic defects in annealed Ti＋ Nb bearing ULC-BH steel.

关键词： ULC-BH steels internal frictions positron annihilation lifetimes coincidence Doppler broadening

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Preparation and electrical properties of the new lead-free (1 - X )Bi0.5Na0.5TiO3-xBa(Ni1/3Nb2/3)O3 piezoelectric ceramics

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Journal of the Ceramic Society of Japan 2015年第1443期123卷 1038-1042页

作者： Pan, Zhao An, Mingjie Chen, Jun Fan, Longlong Liu, Laijun Fang, Liang Xing, Xianran Department of Physical Chemistry University of Science and Technology Beijing Beijing100083 China State Key Laboratory for Advanced Metallurgy University of Science and Technology Beijing Beijing100083 China Key Laboratory of New Processing Technology for Nonferrous Metals and Materials Ministry of Education Guilin University of Technology Guilin541004 China

A new lead-free piezoelectric ceramics of (1 - x)Bi0.5Na0.5TiO3-xBa(Ni1/3Nb2/3)O3 (BNTBNN) (x = 0.00.07) have been prepared by a conventional solid reaction method. Their structures and electric properties have been investigated systematically. A pure perovskite phase can be formed in x ≤ 0.06. By the introduction of Ba(Ni1/3Nb2/3)O3, the ceramics exhibit a lower coercive field EC. Composition for x = 0.02 shows optimal piezoelectric properties, with the piezoelectric coefficient d33 = 121 pC/N. Temperature dependent P(E) loops and S(E) curves of 0.98BNT0.02BNN indicate that the phase transition from the ferroelectric to antiferroelectric takes place over a very wide temperature range from 75 to 150°C. © 2015 The Ceramic Society of Japan. All rights reserved.

关键词： Perovskite

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Microstructural evolution and mechanism of grain growth in magnesia ceramics prepared by high pressure and temperature with ultra-high heating rate

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Science China(Technological Sciences) 2014年第6期57卷 1085-1092页

作者： LIU JiangHao FU ZhengYi WANG WeiMin ZHANG JinYong WANG Hao WANG YuCheng LEE SooWohn NIIHARA Koichi State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Department of Environmental Engineering Sun Moon University Extreme Energy-Density Research Institute Nagaoka University of Technology1603-1 KamitomiokaNagaokaNiigata 940-2188Japan

The fast densification method of combustion reaction plus quick pressing was adopted to prepare nanocrystalline *** densification process of magnesia compact with a particle size of 100 nm was investigated,under the applied pressure of up to 170 MPa,and the temperature range of 1740–2080 K with ultra-high heating rate(above 1700 K/min).High-purity magnesia ceramics with a relative density of 98.8%and an average grain size of 120 nm was obtained at 1740 K,and the grain growth during the densification process was effectively *** characteristic morphology of evaporation-condensation was observed in the compact prepared at 2080 K,which revealed the actual process of mass transfer by gas ***,the investigation on the microstructure evolution and mechanism of grain growth was carried out,on the basis of as-preserved nanocrystalline *** result indicated that the grain growth of the nanocrystalline MgO was controlled by the mechanism of evaporation-condensation rather than surface ***,the pressure had an influence of restraining the grain growth based on solid diffusion and strengthening the effect of gas diffusion with the increasing *** the particular conditions,there existed an appropriate temperature for the densification of nanocrystalline magnesia,while the excessive temperature would exaggerate grain growth and impede densification.

关键词： grain growth densification heating rate evaporation-condensation surface diffusion nanocrystalline ceramics

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Mussel‐Directed synthesis of Nitrogen‐Doped Anatase TiO2

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Angewandte Chemie 2016年第9期128卷

作者： Jingjing Xie Hao Xie Bao‐Lian Su Yi‐bing Cheng Xiaodong Du Hui Zeng Menghu Wang Weimin Wang Hao Wang Zhengyi Fu State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology Wuhan 430070 P.R. China School of Chemistry Chemical Engineering and Life Science Wuhan University of Technology Wuhan 430070 P.R. China Laboratory of Inorganic Materials Chemistry University of Namur B-5000 Namur Belgium Department of Materials Engineering Monash University Victoria 3800 Australia Department of Pearl Research Guangdong Ocean University Zhanjiang 524025 P.R. China

Structure‐forming processes leading to biominerals are well worth learning in pursuit of new synthetic techniques. Strategies that attempt to mimic nature in vitro cannot replace an entire complex natural organism, requiring ingenuity beyond chemists′ hands. A “bioprocess‐inspired synthesis” is demonstrated for fabrication of N‐doped TiO 2 materials at ambient temperature by direct implantation of precursor into living mussels. The amorphous precursor transforms into N‐doped anatase TiO 2 with a hierarchical nanostructure. Synthetic TiO 2 exhibits high phase stability and enhanced visible‐light photocatalytic activity as a result of modifications to its band gap during in vivo mineralization. Intracellular proteins were found to be involved in TiO 2 mineralization. Our findings may inspire material production by new synthetic techniques, especially under environmentally benign conditions.

关键词： Raumtemperatur Biologisch inspirierte Synthesen Intrazelluläre Proteine Organismen Stickstoffdotiertes TiO2

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Carbon nanotubes suspended in ethylene glycol yield nanofluids with enhanced heat transfer properties 13

Carbon nanotubes suspended in ethylene glycol yield nanoflui...

引用

13th International Conference on Simulation and Experiments in Heat and Mass Transfer, HT 2014

作者： Cheng, H.B. Ma, W.T. Hu, W. Wu, J.F. Xiao, J. Chen, Z.B. Zhang, Q.J. Wereley, N.M. State Key Laboratory of Advanced technology for Materials Synthesis and Processing Wuhan University of Technology China Department of Aerospace Engineering University of Maryland United States

ISBN: (纸本)9781845647940

Nanofluids (NFs) consisting of carbon nanotubes (CNTs) suspended in ethylene glycol (EG) were synthesized, and their stability and thermal conductivity enhancement rate were investigated. Stability of the CNT/EG-based NFs was enhanced by adding gum Arabic (GA). The increase in suspension stability was experimentally characterized using static and centrifugal testing processes. The mechanisms of GA in enhancing the fluid stability were characterized and the optimal mass ratio of GA to CNT was found to be about 11% by weight. Thermal conductivity was measured for varying CNT volume fraction under different fluid temperatures, and a nearly linear relationship between the thermal conductivity and the CNT volume fraction and temperature was observed. © 2014 WIT Press.

关键词： Stability

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Highly porous TiO 2 hollow microspheres constructed by radially oriented nanorods chains for high capacity, high rate and long cycle capability lithium battery

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Nano Energy 2015年 16卷 339-349页

作者： Jun Jin Shao-Zhuan Huang Jie Shu Hong-En Wang Yu Li Yong Yu Li-Hua Chen Bin-Jie Wang Bao-Lian Su Laboratory of Living Materials at the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology 122 Luoshi Road 430070 Wuhan Hubei China Faculty of Materials Science and Chemical Engineering Ningbo University 818 Fenghua Road 315211 Ningbo Zhejiang China FEI Company Shanghai Nanoport 399 Shengxia Road 201210 Shanghai China Laboratory of Inorganic Materials Chemistry (CMI) University of Namur 61 rue de Bruxelles B-5000 Namur Belgium Department of Chemistry and Clare Hall College University of Cambridge UK

Hierarchical nanorods chains-constructed TiO 2 hollow microspheres (HNC-TiO 2 -HMSs) have been designed and prepared through a facile one-pot fluorine-free solvothermal alcoholysis route using TiCl 4 and isopropanol reaction system. Owing to the assembly of radially oriented nanorods chains leading to the formation of the shell of the hollow spheres, a large series of straight channels along nanorods chains are formed. Such highly porous hollow microspheres with hollow cavity, straight nanorods chains and straight nanochannels are highly desirable for Li ions batteries because such structure can easily store the electrolyte, facilitate the charge diffusion and Li + insertion and buffer the volume change during the Li + insertion/extraction process. One of the key innovation of the present work is the fine tuning of water amount released from the esterification of alcohol to induce in a well controlled hydrolysis of TiCl 4 and engineer precisely HNC-TiO 2 -HMSs formation. Most importantly, the released Cl − ions direct the nanorods growing along (001) crystal plane and self-assembling along the radial direction accompanying with nanorods size controlling to form HNC-TiO 2 -HMSs. The obtained TiO 2 anode material with such special structure demonstrates excellent Li + storage capacity with outstanding cycle performance and superior rate capability at different rates over 700 cycles: a reversible capacity of 216 mA h g −1 is obtained after 100 cycles at 1 C and a reversible capacity of 112 mA h g −1 is retained after 100 cycles at 10 C. The SEM, TEM, HRTEM and in-situ XRD techniques have been utilized to shed light on the Li + insertion process and the phase transformation. Most importantly, a self-improving phenomenon of cycle performance and storage capacity was observed owing to the formation of numerous ~5 nm Li 2 Ti 2 O 4 nanocrystals formed on the surface of the nanorods chains. The results reveal that the high performance of the as-prepared HNC

关键词： Highly porous hollow microspheres TiO 2 Nanorods chains Lithium ion batteries Self-improving phenomenon

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