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Formation of M_(n+1)AX_n phases in Ti–Cr–Al–C systems by self-propagating high-temperature synthesis

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Rare Metals 2014年第4期33卷 419-426页

作者： Guo-Bing Ying Xiao-Dong He Shan-Yi Du Chun-Cheng Zhu Yong-Ting Zheng Yu-Ping Wu Cheng Wang Institute of Metals and Protection College of Mechanics and MaterialsHohai University Center for Composite Materials and Structure Harbin Institute of Technology College of Chemistry and Chemical Engineering Harbin Normal University

In this paper, phase composition of the Mn＋l- AXn phases by self-propagating high-temperature synthesis （SHS） was determined using Ti, Cr, A1, and carbon black as raw materials. And, phase composition and micro- structures of the Mn＋1AXn phases-contained bulk by SHS with the pseudo-hot isostatic pressing （SHS/PHIP） were investigated in Ti-Cr-AI-C systems raw materials. Riet- veld XRD refinement was introduced to study the lattice parameters and phase composition of the resultant phases from the SHSed and SHS/PHIPed samples. Ti2A1Cx, Ti3A1C2, and Cr2A1Cx by SHS were detected in the Ti-Cr- A1-C systems, as well as the binary carbide of TiC and intermetallics. The mechanical properties of the synthe- sized bulk samples were determined, exhibiting a high strength and toughness compared with the typical mono- lithic Mn＋1AXn phase ceramics. It is indicated that the samples prepared by SHS/PHIP are identified to be a strategy for improving the mechanical properties of monolithic Mn＋1AXn phase.

关键词： SHS/PHIP Mn+lAXn phases phasecomposition Microstructure Mechanical properties

Phase composition and luminescent properties of strontium aluminate long persistence phosphor synthesized by combustion synthesis method with different Sr/Al ratios

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Rare Metals 2013年第4期32卷 414-419页

作者： Wen-Zhou Sun Yu-Hong Chen Lan-Er Wu Yong Jiang School of Materials Science and Engineering Beifang University of Nationalities

Strontium aluminate long persistence phos phors are synthesized by combustion method. By control- ling the raw material ratio （Sr/Al）, the effects of phase composition on subsequent spectroscopic properties of phosphors are studied. Results show that the phase com-position changes from strontium-rich phase to aluminum- rich phase with the decrease of Sr/AI： when the rate of Al/Sr changes from 3：1 to 1：1, the main crystal phase of samples is Sr3Al206, and it exhibits the characteristic fluorescence of Eu^3＋ in the lattice of Sr3Al206; when the rate of Al/Sr is between 1：2 and 2：7, phase composition is the mixture of SrAl204 and SrAl4OT, and it emits the characteristic fluorescence of Eu^2＋ in SrAl204 but not in SrAl4OT; when Al/Sr decreases to 1：4 or even 1：12, the main crystal phase of samples transform into SrAl12019, and the characteristic emission peak is about 470 nm, which corresponds to the characteristic emission of Eu2＋ in SrAl12019. At the end of the article, the influence laws of two different synthesis methods on phase composition of samples between high-temperature solid method and combustion method are compared. Compared with the high-temperature solid method, the rule of influence is similar, but the mole ratio of Al/Sr in products is always higher than the initial ratio of the raw material, and com-pounds like Sr4Al14025 are not obtained by combustion method.

关键词： Strontium aluminate long persistencephosphors Combustion synthesis Sr/Al ratio phasecomposition Emission wavelength

Effects of Additives on Phase Composition,Microstructure,and Properties of Zirconia Products Fired at Different Temperatures

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China's Refractories 2010年第4期19卷 25-29页

作者： TAN Qinghua WU Aijun SUN Honggang YAN Shuangzhi Henan Key Laboratory of Advanced Refractories Sinosteel Luoyang Institute of Refractories Research Co. Ltd. Luoyang 471039 China

The calcia-stabilized zirconia grains with different sizes and the calcia-stabilized zirconia powder were used as main starting materials,m-ZrO2 micropowder and Y2O3 powder as additives,and sulphite liquor as binder. The specimens with the dimension of 50 mm×50 mm were prepared under 150 MPa,dried at 110 ℃ for 24 h,then fired at 1 700 ℃ and 1 750 ℃ in air,respectively. The phase composition,microstructure and properties of specimens were analyzed with XRD,SEM,and other test methods. The results indicate that：（1） the appropriate amount of m-ZrO2 micropowder and Y2O3 powder can promote the sintering property of calcia-stabilized zirconia products,and the sintering property is better when m-ZrO2 micropowder addition in matrix is 5%-10% and Y2O3 powder addition in matrix is 1%; （2） the main phase compositions of zirconia products fired at 1 700 ℃ are c-ZrO2 and m-ZrO2,no t-ZrO2 is found; （3） the microstructure of the specimen containing additives is obviously different with the specimen without additives after firing at 1 700 ℃. The matrix grains rearrange and grow in the specimens containing additives forming permeable network gas pore,and the process of the grain growth helps the gas release during sintering. So the relative density is bigger in fired specimens containing an appropriate amount of additives.

关键词： Additive Zirconia Temperature phasecomposition Properties Microstructure