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New Progress on Rectorite/Polymer Nanocomposites
WANG Xiao-Ying, LIU Bo, TANG Yu-Feng, SU Han-Jie, HAN Yang, SUN Run-Cang
2012 Vol. 27 (2): 113121
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3523 )
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Rectorite is a kind of layered silicate originated from Hubei province; it has unique structure characteristic albeit with the structure and characteristic much like those of montmorillonite. Rectorite is a regularly interstratified clay mineral with alternate pairs of dioctahedral mica-like layer (nonexpansible) and dioctahedral montmorillonite-like layer (expansible) in 1:1 ratio. In recent years, rectorite has been widely used in the preparation of polymer/layered silicate nanocomposite. This paper introduced the structure and surface modification of rectorite and the structure and preparation method of rectorite/polymer nanocomposite. In particular, the new results of chitosan- based rectorite nanocomposite were summarized. The researchers prepared a series of chitosan-based rectorite nanocomposites via simple solution intercalation, although the rectorite content in these studies was higher than that of other reports, rectorite still dispersed well in the chitosan matrix, there were hydrogen-bonding and electrostatic interactions between rectorite and chitosan. Moreover, the researchers studied antimicrobial activity and mechanism, adsorption capacity, drug-controlled release behavior, gene transfection capacity and structure-property relationship of chitosan-based rectorite nanocomposites. In addition, the films, microsphere and nanoparticles of chitosan-based rectorite nanocomposites were prepared and their properties such as mechanical property, barrier ability, antiultraviolet capacity, thermal stability were studied. At last, the future research of rectorite/polymer nanocomposite was expected.
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Preparation and Photophysical Properties of Materials Obtained by Co-intercalation of 4-MAA and 2-NSA into Mg-Al-LDH
LI Lei, ZHU Kai, ZHANG Li, CHEN Da-Zhou
2012 Vol. 27 (2): 122128
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2376 )
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A pair of chromophores with donor-acceptor properties, 4-methoxyphenylacetic acid (4-MAA) and 2-naphthalene sulfonic acid (2-NSA), were intercalated into the layered double hydroxide (LDH), [Mg0.66Al0.34(OH)2](CO3)0.17·0.67H2O by the method of ion-exchange procedures in ethylene glycol. The obtained co-intercalation compounds were characterized by X-ray diffraction, infrared and thermogravimetry techniques. The photochemical properties of the obtained compounds were studied by UV-Vis absorption and fluorescence spectroscopy. The guest molecular sizes and structures were investigated utilizing an ab initio (HF/6-31G) method by G03w. It was believed that the molecular axis of the interlayer 4-MAA molecule was tilted approximately 45°to the layers, and the molecular axis of the interlayer 2-NSA molecule was perpendicular to the plane of the host layer. Both of them were arranged in monolayer between the metal hydroxide layers. These results indicate that the confinement of the pair of chromophores, 4-MAA-2-NSA, within the interlayer region of hydrotalcites are in favor of guest-host interaction and guest-guest interaction, and that the pair of chromophores, 4-MAA-2-NSA can give rise to energy transfer processes because of the characteristics of their excited states.
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Microstructures and Properties of WC/Natural Zeolite Composites
ZHENG Yi-Fan, ZHAO Na, ZHANG Jie, YU Xiao-Ye, MO Wei-Min
2012 Vol. 27 (2): 129133
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2674 )
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WC/zeolite nanocomposites were prepared by ball-milling a mixture of ammonia metatungsten (AMT) and zeolite and then reducing the ball-milled precursor under mixed CH4/H2 atmosphere at 900℃. The effects of carbonization time on the microstructure, phase composition, and WC distribution of as-prepared nanocomposites were investigated by X-ray diffraction (XRD), high resolution transmission electron microscope (HRTEM), and scanning transmission electron microscope (STEM). The electrocatalytic activities in alkaline solutions of these nanocomposites were evaluated in a three-electrode system by a powder microelectrode method. Due to the porous structure and high surface area of zeolite, the ball-milled AMT/zeolite precursor could be rapidly reduced in a mixed CH4/H2 atmosphere and then formed WC/zeolite nanocomposites. It was found that the active formed phase mainly composed of W2C and WC which were highly dispersed and extremely small-sized. The results also showed that the WC/zeolite nanocomposite obtained by carbonizing the ball-milled precursor for 4 h exhibited the best electrocatalytic activity, because this sample had smallest-sized and highest relative concents of tungsten carbide.
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Preparation and Characterization of Cyano-functionalized Mesoporous Silica
GUO Feng, ZHU Gui-Ru, GAO Cong-Jie
2012 Vol. 27 (2): 134138
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2596 )
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Cyano-functionalized mesoporous silicas were synthesized by one-pot co-condensation of tetraethoxysilane (TEOS) and 2-cyanoethyltriethoxysilane (CTES), using Pluronic P123 triblock copolymer as the structure- directing agent under strongly acidic conditions. The physicochemical properties, such as structure, morphology, pore property and cyano content were characterized by XRD, SEM, N2 adsorption-desorption isotherm, FT-IR and elemental analysis, respectively. It was found that the order for adding the two silicon sources, namely CTES and TEOS has a profound influence on the content and distribution of cyano group. Within three mixture orders, the sample synthesized with pre-mixed TEOS and CTES as silica sources is best, with highest cyano content and uniform distribution. As cyano content increasing, surface morphology and pore properties are changed. The straight cylindrical pore structure is transformed into bottle-neck-like structure with up to 20mol% CTES loading in the synthesis mixture. Pore volume, surface area and pore size decrease from 0.70 cm3/g to 0.22 cm3/g, 666 m2/g to 312 m2/g, 4.2 nm to 2.7 nm, respectively when cyano content is increased, which maybe result from that cyano group occupies part of pore channel.
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Adsorption Equilibrium and Kinetics of CO2 and H2O on ActivatedCarbon
XU Dong, ZHANG Jun, LI Gang, XIAO Penny, WEBLEY Paul, ZHAI Yu-Chun
2012 Vol. 27 (2): 139145
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2759 )
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Activated carbon is well applied in pressure swing adsorption process for CO2 capture. The real flue gas contains saturated water vapor as well. In this study, single and binary components adsorption equilibrium and kinetics of H2O/CO2 were studied according to their adsorption isotherms and breakthrough curves. Results showed that activated carbon could adsorb high amount of CO2 and low amount of N2, that showed a good CO2/N2 selectivity. As activated carbon contains the functional groups, the activated carbon can adsorb large amount water at high water partial pressure. However, because of different CO2 adsorption mechanism, water adsorption has almost no impact on CO2 adsorption on activated carbon. The kinetics study showed that CO2 adsorption velocity on activated carbon is much faster than that of H2O.
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Synthesis of Nitrogen Doped Graphene through Microwave Irradiation
WANG Can, WANG Yan-Li, ZHAN Liang, HE Xing, YANG Jun-He, QIAO Wen-Ming, LING Li-Cheng
2012 Vol. 27 (2): 146150
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3739 )
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Graphite oxide was synthesized with Staudenmaier method using natural flake graphite as carbon source. After graphite oxide was impregnated into ammonium carbonate saturated solution, NH4+ intercalated graphite oxide was given. Rapid thermal exfoliation and reduction of NH4+ intercalated graphite oxide to graphene was achieved as well as the nitrogen-doping of graphene under the condition of microwave irradiation. SEM, TEM, EDS, XRD, XPS and Raman were performed to characterize the synthesized nitrogen-doping of graphene. The synthesized nitrogen-doped graphene was transparent and wrinkled with 2-5 graphite layers. The nitrogen content of as-prepared nitrogen-doped graphene was 1.56wt%, corresponding to pyridinc N, pyrrolic N and graphitic N incorporated into the graphitic network.
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Influences of Mild Oxidation Treatment on the Structure and Electrochemical Behavior of Spherical Graphite
JIAN Zhi-Min, LIU Hong-Bo, SHI Lei, HE Yue-De, XIAO Hai-He, KUANG Jia-Cai
2012 Vol. 27 (2): 151156
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3262 )
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The effects of mild oxidation treatment on the crystal structure, morphology and electrochemical behavior of spherical graphite were investigated. The structure and morphology of the samples were characterized by XRD, Raman spectra and SEM analysis, respectively. The electrochemical behavior of the samples was studied using galvanostatic charge/discharge test, powder cavity microelectrode technique and slow scan rate cyclic voltammograms. The results indicate that structural defects in graphite particles and disordered degree of near surface region of graphite increase after modification, while the average in-plane crystallite domain size La and content of rhombohedral phase decrease. The graphite particles present irregular flake shape and some graphene sheets show flexual and sculptural margin. Electrochemical measures show that reversible capacity of modified graphite increases from 345.5 mAh/g to 381.4 mAh/g, and cycling performance is improved. During deintercalation process of the modified graphite, stage transformation from stage 1 Li-GICs (lithium-graphite intercalation compounds) to stage 2 Li-GICs begins to happen at lower voltage, compared with that of the raw graphite.
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Ablation Capability of Flake Graphite Reinforced Barium-phenolic Resin Composite under Long Pulse Laser Irradiation
YU Qing-Chun, WAN Hong
2012 Vol. 27 (2): 157161
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2860 )
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The carbon fiber reinforced phenolic resin composite is widely used as a thermal protection material because of its excellent thermal ablation. A novel flake graphite reinforced barium-phenolic resin composite was made by roller coating technology and its thermal ablation capability under long pulse laser irradiation was studied. The results show that the thermal ablation rate of the flake graphite reinforced barium-resin composite is 32.8 μg/J at 1700 W/cm2 irradiation power density, which is much lower than that of the carbon fiber reinforced barium-resin composite or barium-phenolic resin obviously. The anti-ablative mechanism of the flake graphite reinforced barium- phenolic resin composite is investigated by the observation of its microstructure and the calculation of the laser energy coupling with the material. It is found that the flake graphite is arrayed homogeneous alignment as sandwich among the composite. When the laser radiation gets on the composite, the flake graphite plays as a mirror and reflects part of the laser, and then the laser radiation energy deposition on the composite is reduced. It is also found that the size of the flake graphite also affects the ablation capability. The composite with the flake graphite diameter of about 0.5 mm has the lowest thermal ablation rate.
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Effect of Composition and Structure on the Specific Resistivity of Continuous Silicon Carbide Fibers
WANG De-Yin, SONG Yong-Cai, JIAN Ke
2012 Vol. 27 (2): 162168
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2593 )
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Three kinds of continuous SiC fibers with different specific resistivity were prepared by the pyrolysis of cured polycarbosilane fiber, and the structure and composition of the three fibers were characterized. Results show that SiC fibers with different specific resistivity can be obtained by changing the curing and pyrolysis conditions. And the total free carbon content and the ability to crystallize will no longer affect the specific resistivity notably when the fiber is covered with an excess carbon layer, as a result the fiber will have a low electrical resistivity. The excess carbon layer in the circular outer part is originated form the re-pyrolysis and deposition of hydrocarbon volatiles. Removal of the carbon by oxidative treatment may affect the surface property and also promote the magnitude of specific resistivity. The influence of the surface property on the specific resistivity is considerable which should not be neglected.
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Combustion Synthesis of α-Si3N4 Powder Using AC as Additive
CHEN Yi-Xiang, YANG Jian-Hui, JIANG Zhi-Jun, LIN Zhi-Ming, LI Jiang-Tao
2012 Vol. 27 (2): 169173
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2669 )
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Combustion synthesis (CS) of high content of α-Si3N4 powders was carried out using Si and Si3N4 powders as reactants with the addition of diazenedicarboxamide (AC) at a relatively low N2 pressure of 3 MPa. The phase compositions and microstructure of products were characterized by XRD and SEM. Effects of AC contents on the phase compositions and Si3N4 particles morphology were studied. In addition, the reaction mechanisms were discussed. The results indicated that the additive AC promoted the nitridation of Si. The α-Si3N4 contents in the combustion-synthesized products showed great dependence on the contents of AC added in the reactants, which reached 85.2wt% adding with 24wt% AC. Meanwhile, impurities such as SiC, Si2N2O could be found in the final products when more than 12wt% AC agent was added. Poor dispersibility of Si3N4 particles would be more serious with increasing AC contents in the reactants. N2, CO and NH3 produced by decomposition of AC leaded to a change of compact porosity, thermal convection and mass transfer processes, which was responsible for the increasing contents of α-Si3N4 and the discrepancy morphology of the products.
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Effect of Polymerization Temperature on Polymerization Degree and Structure of Calcium Polyphosphate
WU Hang, ZHANG Li-Fang, BAI Wei, MA Chi, XIONG Cheng-Dong
2012 Vol. 27 (2): 174178
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2949 )
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The properties of calcium polyphosphate (CPP) were greatly affected by its polymerization degree. A series of CPP with different polymerization degree were prepared by polymerization of calcium phosphate monobasic monohydrate (MCP) at different temperatures. Polymerization degree was analyzed by liquid state 31P nuclear magnetic resonance (31P-NMR). The effect of different temperature on polymerization degree and structure of CPP was discussed. MCP was analyzed by differential scanning calorimetry-thermmogravimetry (DSC-TGA) and possible mechanism of the polymerization reaction was proposed. The results show that polymerization of MCP mainly produces CPP. When the elevation temperature is below 1000℃, polymerization degree increases; however the opposite is true when the polymerization temperature exceeds 1000℃. Additionally, the formation of a ring-structure phosphate, namely calcium metaphosphate (CMP), is also promoted with increasing polymerization temperature. The CMP content increases with increasing polymerization temperature and significantly increases when the polymerization temperature is above 1000℃.
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Effect of Interaction of Ni2+ and Green Tea Epigallocatechin Gallate on Tongue Carcinoma Cells
LUO Zhen-Lan, WANG Hai-Bo, SU Jian-Sheng
2012 Vol. 27 (2): 179184
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2199 )
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Ni2+ is the major ion release from nickel-based dental casting alloy and carcinogens. The major polyphenolic constituent present in green tea, (-)epigallocatechin-3-gallate (EGCG), shows chemoprevention on human cancer. The aim of this study was to determine the interaction between EGCG and Ni2+ and the biological effects on tongue squamous cell carcinoma. The interaction of EGCG and Ni2+ was analyzed by LC/MS. The cell viability was assessed by the MTT reduction assay. The results of LC/MS indicated that [EGCG-2Ni2+] and [EGCG-Ni2+] formed when EGCG and Ni2+ were added simultaneously. Ni2+ and EGCG both inhibited the proliferation of tongue carcinoma cells in a time- and dose-dependent manner. The cytotoxicity against tongue carcinoma cells was increased when EGCG and Ni2+ cotreated, and the inhibition effects were extremely dependent on the concentrations of EGCG and Ni2+, addition order and the ratio of [Ni2+] to [EGCG].
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Active Biocatalysts Based on Pepsin Immobilized in Short Channeled Zr-Ce-SBA-15
WANG Fang, LI Jian-Sheng, RAN Dong-Qin, DUAN Meng-Shan, SUN Xiu-Yun, WANG Lian-Jun
2012 Vol. 27 (2): 185190
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2981 )
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Short channeled Zr-Ce-SBA-15 (ZCS) mesoporous materials with hexagonal platelet morphologies were synthesized through a hydrothermal route without addition of mineral acids. Porcine pepsin was immobilized inside ZCS and conventional SBA-15 through physical adsorption. A grafting step with [1-(2-amino-ethyl)-3-aminopropryl] trimethoxysilane (AAPTS) was performed to reduce the pore openings of the host material in order to minimize the enzyme leaching. The hybrid materials were characterized by X-ray diffraction, scanning electron microscope, transmission microscope, N2 adsorption/desorption and Fourier-transform infrared spectroscope. The results confirmed that pepsin is located inside the channels of the mesoporous materials and the grafting process does not affect the mesoporous structure. The immobilization of pepsin into ZCS and SBA-15 were compared. The results demonstrate that the ZCS materials have higher adsorption rates and adsorption capacities (the maximum adsorption capacity is 257.9 mg/g) compared with SBA-15. The ZCS materials with short channels are superior to conventional SBA-15 facilitating molecular diffusion. The catalytic activity of the hybrid bioinorganic material was tested with hemoglobin. The immobilized pepsin has maintained the necessary degree of freedom to fulfill its catalytic activity.
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Influence of CaO and ZnO Content on the Crystallization and Foaming of CaO-Al2O3-SiO2 Glass-ceramics
XU Bo, CAO Jian-Wei, LIANG Kai-Ming
2012 Vol. 27 (2): 191194
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2602 )
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CaO-Al2O3-SiO2 system glass were used to produce foam glass-ceramics with high performance. Influence of ZnO and CaO contents on the crystallization and foaming behavior of CaO-Al2O3-SiO2 glass, were investigated using graphite as foaming agent. Addition of ZnO can suppress the crystallization of pseudowollastonite, improve the sintering of the mixture of glass powder and foaming agent, and reduce the combustion-loss of foaming agent at low temperature. Further addition of CaO leads to higher crystallinity, as well as higher glass-viscosity, which will hamper the foaming process and get poorer foaming ability. 18wt% CaO and 6wt% ZnO in CaO-Al2O3-SiO2 glass are helpful to produce foam glass ceramics with high porosity at the sintering temperature of 1000℃.
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Effects of Reactant Mixing Mode on Dispersibility and Particle Size Stability of Cuprous Oxide Particles
WANG Yue-Jun, ZHOU Kang-Gen, JIANG Zhi-Gang
2012 Vol. 27 (2): 195200
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2560 )
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Spherical Cu2O particles were prepared under high reaction concentration and without any additives using CuSO4, NaOH, and glucose as raw materials. The products were characterized by XRD, SEM and smileview software. The effects of reactant mixing modes on dispersibility and size stability of Cu2O particles were investigated. It is found that when Cu(OH)2 was prepared by slowly mixing NaOH and CuSO4 solutions at first step, and then reduced by adding glucose solution at second step, Cu2O particles were formed by so-called “rapid nucleation- slow growth” model, and well-dispersed spherical Cu2O particles with stable particle size were prepared. The good dispersibility of Cu2O particles can be explained by the slow growth of Cu2O particles, which allows the soft agglomeration of Cu2O particles to be broken by stirring and prevented from becoming hard agglomeration through chemical bond between crystal nuclei. The good particle size stability can be explained by good thermal stability of Cu(OH)2 which allows the precursor to keep oneness during heating up and prevents the renucleation in the reduction.
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Thermoelectric Properties of In4Se3 Synthesized by Combing Sonochemical and SPS Method
LIU Dan-Dan, WANG Shan-Yu, TANG Xin-Feng
2012 Vol. 27 (2): 201204
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2603 )
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Single-phase In4Se3 powders were synthesized by a sonochemical method combined with subsequent deoxidizing heat-treatment, and a bulk sample was prepared via a spark plasma sintering (SPS) method. The phase composition, microstructures and thermoelectric transport properties of the as-prepared bulk sample were studied. The bulk sample possesses refined crystalline and obvious anisotropy observed in the different directions, where a large number of fine layered structures exist along the SPS pressing direction. Therefore, the thermoelectric properties of the bulk sample also show significant anisotropy. Owing to higher Seebeck coefficient and lower thermal conductivity, a better ZT is achieved in direction of the SPS pressure compared with the perpendicular direction. As a result, the maximum ZT reaches 0.56 at 700 K, which is comparable with that of the samples synthesized by other physical techniques.
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Improvement of Adhesive Strength of Diamond Films by Plating Cr-diamond Composite Interlayer
QIU Wan-Qi, PAN Jian-Wei, LIU Zhong-Wu, YU Hong-Ya, ZHONG Xi-Chun, ZENG De-Chang
2012 Vol. 27 (2): 205208
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2335 )
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The diamond films were fabricated by using a two-step process on copper substrates. Firstly, chromium (Cr)-diamond composite interlayer was electroplated on copper substrates, then continuous diamond films were deposited by using hot-filament chemical vapor deposition (HFCVD) method. The interfacial characteristics were investigated by indentation test. The film surface morphology, phase structure and inner stress were analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD) and Raman spectrum. The results show that the diamond particles are deeply imbedded in chromium layer and the amorphous Cr in the composite interlayer is carborized to Cr3C2 in the CVD process. Low inner stress is detected in the diamond films and good adhesive strength between film and substrate is obtained due to the deep anchoring of the diamond particles in the Cr3C2 matrix. Concentric cracks but no delaminate area and radial cracks are observed on the periphery of the indentation in 294 N load indentation test.
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Thermophysical Properties of Y2O3 and Gd2O3 Co-doped SrZrO3 Thermal Barrier Coating Material
MA Wen, SONG Feng-Yu, DONG Hong-Ying, XU Ping, LUN Wen-Shan, ZHENG Xue-Bin
2012 Vol. 27 (2): 209213
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2502 )
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Y2O3 (5mol%) and Gd2O3 (5mol%) co-doped SrZrO3 (Sr(Zr0.9Y0.05Gd0.05)O2.95, SZYG) was synthesized by solid state reaction method. The phase stability of the SZYG powder synthesized at high temperature of 1450℃ for a long period and at temperature range of 200-1400℃ was characterized by XRD and DSC, respectively. The coefficients of thermal expansion (CTEs) of bulk SZYG recorded by a high-temperature dilatometer show that the phase transitions of SrZrO3 is suppressed remarkably by co-doping Y2O3 and Gd2O3. The thermal conductivity of bulk SZYG at 1000℃ is 1.36 W/(m·K), which is 35% lower than that of bulk SrZrO3 and 8YSZ. The good chemical compatibility of SZYG with 8YSZ and Al2O3, is detected after heat-treatment at 1250℃ for 24 h.
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Enhanced Ferroelectric and Piezoelectric Properties of Textured K0.45Na0.55NbO3 Ceramics Prepared by Screen-printing Technique
LI Ya-Li, HUI Chun, LI Yong-Xiang, WANG You-Liang
2012 Vol. 27 (2): 214218
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6658 )
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Grain oriented K0.45Na0.55NbO3 (KNN) lead-free piezoceramics with sintering aid K4CuNb8O23 (KCN) were fabricated by screen-printing technique, using plate-like NaNbO3 as templates. The plate-like NaNbO3 template particles were synthesized from bismuth layer-structured Bi2.5Na3.5Nb5O18 precursors by the topochemical micro-crystal conversion method. The textured KNN ceramics showed brick-wall-like grains which aligned parallel to the screen-printing direction. The screen-printed KNN ceramics possessed both a high grain orientation (Lotgering factor f=95%) and a relative high density (92% of theoretical density). The orientation degree and electrical properties of textured (K0.45Na0.55)NbO3 ceramics exhibited anisotropic feature in the parallel (sp//) and perpendicular (sp?) plane. Compared with the random oriented ceramics with same composition, the dielectric constant εr, piezoelectric constant d33, and electromechanical coupling coefficient kp were increased by about 75%, 44% and 42% in sp// plane, respectively, and about 35%, 30% and 35% in sp? plane, respectively. Screen-printing is a simple and effective method for the fabrication of grain oriented lead-free piezoelectric ceramics.
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Synthesis and Electrochemical Properties of Porous SnO2 Agglomerates
LI Fang, ZHU Ying-Chun
2012 Vol. 27 (2): 219224
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6415 )
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Porous SnO2 agglomerates with crystalline pore walls were obtained by employing CTAB and trimethyl phosphate (TMP) as molecular co-templates via hydrothermal method. Tin (IV) chloride dihydrate was used as the inorganic precursor at high molar ratio of surfactant/Sn4+. The resulting samples were characterized by SEM, (HR)TEM, XRD, thermal analysis and nitrogen adsorption-desorption to examine the structural and morphological characters. The results indicate that the addition of small co-template TMP can facilitate the assembling of tin ions near the CTAB micelles, which can increase the specific surface area and improve the thermal stability of the resulted sample. The electrochemical properties of porous SnO2 as the anode materials of lithium-ion battery (LIB) are further investigated by using galvanostatic method. The porous SnO2 calcined at 300℃ displays a much higher reversible capacity of 962.4 mAh/g, which can be ascribed to the incomplete combustion of the organic materials and the unique nanostructure itself. The addition of bigger counter ions with large electric negativity might give an alternative approach to improve the properties of porous metal oxides synthesized by soft template method.
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