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Thermo-mechanical properties of mullite–zirconia composites derived from reaction sintering of zircon and sillimanite beach sand: Effect of CaO

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Transactions of Nonferrous Metals Society of China 2016年第9期26卷 2397-2403页

作者： P.KUMAR M.NATH A.GHOSH H.S.TRIPATHI Refractories Division CSIR–Central Glass and Ceramic Research Institute Academy of Scientific and Innovative Research (AcS IR) CSIR–Central Glass & Ceramic Research Institute

Mullite–zirconia composites containing 20% zirconia（mass fraction） were prepared by reaction sintering route utilizing Indian coastal zircon flour and sillimanite beach sand. 4%-12% of CaO（mole fraction） with respect to zirconia was used as additive. The effect of additive on densification, microstructure as well as various mechanical and thermo-mechanical properties was studied. Incorporation of CaO reduced the densification temperature of the composites to 1550 ℃ compared to 1600 ℃（for CaO free samples）. CaO formed small amount of liquid phase（calcium aluminosilicate）, which facilitated sintering. Average grain size of the composites decreased up to 4% CaO addition, afterwards grain size increased with further addition of CaO. Samples with 4% CaO exhibited ～225 MPa of flexural strength, ～6 MPa·m^1/2 of fracture toughness and significant improvement in thermal shock resistance. CaO stabilized the tetragonal zirconia phase and thus improved the mechanical properties.

关键词： reaction sintering mullite-zirconia composites flexural strength refractory

Synthesis of O’-SiAlON-BN Composite by reaction sintering

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China's Refractories 2006年第4期15卷 14-19页

作者： ZHEN Qiang YAN Kai ZHANG Dahai LI Wenchao Nano-Science and Nano-Technology Research Center School of Material Science and Engineering Shanghai University The 703 Institute of First Academe China Spaceflight Science and Technology Group Company Department of Physical Chemistry University of Science and Technology Beijing

By using micron α-SisN4, SiO2, Al2O3 and h-BN as starting materials, O＇ -SiAION-BN （ Si2-z AlzO1 ＋z N2-z, z= 0. 3） composite was synthesized by reaction sintering. According to theoretical proportion ratio： n（ SiO2）/n（ α-Si3N4） = 1, the effects of two sintering aid composites, Y2O3 ＋ B2O3 and Y2O3 ＋ TiO2 at 1700℃ for 2h, were studied. The results indicate that Y2 O3 ＋ TiO2 as sintering aid can accelerate reaction sintering of O＇ -SiAION-BN more effectively than Y2O3 ＋ B2O3, and the relative density of the composites declined with the increase of BN addition （10%, 20% and 30% respectively）; XRD analysis found that excessive β-Si3N4 existed in the O＇ -SiAION-BN composite. Therefore, in order to get more pure O＇ -SiAION and BN phases in the composites ore SiO2 is needed. When Y2O3 ＋ TiO2 was used as sintering aid and addition of BN was 10%, the result of cross experiment on condition of A- n（SiO2）/n（α-Si3N4） was 1.05, 1.1 and 1.2; B-- addition of sintering aid was 2%, 4% and 6% ; C-- firing temperature was 1600℃, 1650℃ and 1700℃ ; D--soaking time was 1h, 2h and 3h, shows that the sintering properties were influenced by factors of firing temperature, soaking time, addition of sintering aid and n（ SiO2 ）/n（α-SisN4） in order of importance. In addition, the technical parameter A s B 3 C s D3 can achieve the highest relative density. Besides, using Pattern Recognition method, the optimized parameter range to form pure O＇ -SiAION and BN without β-Si3N4 remained was determined as Y 〉 1024X^2 - 230. 400X ＋ 11.088 （ X = 0. 9999A -0. 0006C - 0. 0163D, Y = 0. 0163A ＋ 0. 009B -0. 0014C ＋0. 9999D）.

关键词： O'-SiAION-BN reaction sintering Pattern Recognition Synthesis

Reactive sintering of B4C-TaB2 ceramics via carbide boronizing:reaction process, microstructure and mechanical properties

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Journal of Materials Science & Technology 2019年第12期35卷 2840-2850页

作者： Junfeng Gu Ji Zou Peiyan Ma Hao Wang Jinyong Zhang Weimin Wang Zhengyi Fu State Key Laboratory of Advanced Technology for Materials Synthesis and Processing.Wuhan University of Technology Wuhan430070China School of Metallurgy and Materials University of BirminghamB152TTBirminghamUK School of Chemistry Chemical Engineering and Life ScienceWuhan University of TechnologyWuhan.430070China

Carbide boronizing is a promising approach to obtain fine grained boron carbide based ceramics with improved mechanical properties. In this work, reaction process, microstructural characteristics and mechanical properties of BxC-TaB2(x = 3.7, 4.9, 7.1) ceramics were comprehensively investigated via this method. Dense BxC-TaB2 ceramics with refined microstructure were obtained from submicro tantalum carbide and boron powder mixtures at 1800℃/50 MPa/5 min by spark plasma sintering. The stoichiometry of boron carbide was determined from lattice parameters and Raman shift. It was found that uniformly distributed TaB2 grains in the BxC matrix is favor of the densification process and restricting grain ***, planar defects with high density were observed from the as-formed B7.1 C grains and transient stress was considered to contribute to the densification involved with plastic deformation. Microstructural observations indicate the dissolution of oxygen in the TaB2 lattice and most of the B7.1 C/TaB2 phase boundaries were clean. Owing to the highly faulted structure and finer grain size, as-obtained BxC-TaB2 ceramics exhibit high Vickers hardness(33.3–34.4 GPa at 9.8 N) and relatively high flexural strength ranging from 440 to 502 MPa.

关键词： Boron carbide reaction sintering Densification Microstructure Mechanical properties

Effects of the original state of sodium-based additives on microstructure,surface characteristics and filtration performance of SiC membranes

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Chinese Journal of Chemical Engineering 2023年第11期63卷 1-11页

作者： Yuling Xie Qilin Gu Qian Jiang Zhaoxiang Zhong Weihong Xing National Engineering Research Center for Special Separation Membrane State Key Laboratory of Materials-Oriented Chemical EngineeringCollege of Chemical EngineeringNanjing Tech UniversityNanjing 210009China School of Environmental Science and Engineering Nanjing Tech UniversityNanjing 211816China

Sodium-contained compounds are promising sintering additives for the low-temperature preparation of reaction bonded SiC *** sodium-based sintering additives in various original states were attempted,their effects on microstructure and surface properties have rarely been *** this work,three types of sodium-based additives,including solid-state NaA zeolite residue(NaA)and liquidstate dodecylbenzene sulfonate(SDBS)and water glass(WG),were separately adopted to prepare SiC membranes,and the microstructure,surface characteristics and filtration performance of these SiC membranes were comparatively *** showed that the SiC membranes prepared with liquid-state SDBS and WG(S-SDBS and S-WG)showed lower open porosity yet higher bending strength compared to those prepared with solid-state NaA(S-NaA).The observed differences in bending strength were further interpreted by analyzing the reaction process of each sintering additive and the composition of the bonding phase in the reaction bonded SiC ***,the microstructural differentiation was correlated to the original state of the *** addition,their surface characteristics and filtration performance for oil-in-water emulsion were examined and correlated to the membrane *** S-NaA samples showed higher hydrophilicity,lower surface roughness(1.80μm)and higher rejection ratio(99.99%)in O/W emulsion separation than those of S-WG and *** can be attributed to the smaller mean pore size and higher open porosity,resulting from the originally solid-state NaA ***,this work revealed the comprehensive effects of original state of sintering additives on the prepared SiC membranes,which could be helpful for the application-oriented fabrication by choosing additives in suitable state.

关键词： SiC membrane sintering additive reaction sintering Microstructure Oil-in-water emulsions

Zero sintering-induced shrinkage of porous oxide ceramics

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Journal of Materials Science & Technology 2023年第28期159卷 184-193页

作者： Kai Miao Liangjie Liu Jiwei Cao Ran He Sai Li Lingling Wu Zhongliang Lu Dichen Li State Key Laboratory for Manufacturing Systems Engineering Xi’an Jiaotong UniversityXi’an 710049China KOCEL Intelligent Machinery Co. Ltd.Yinchuan 750021China School of Engineering University of LeicesterLeicester LE17RHUnited Kingdom

Porous oxide ceramics are widely used in extreme working conditions owing to their excellent resistance to high temperatures and ***,sintering is an inevitable process applied to ceramics,from the green body to the final *** highly complex structures exacerbate the shrinkage-induced ir-regular deformation and crack formation in the sintering process.A pioneering approach is developed in this study to achieve zero shrinkage for porous alumina ceramics during multistep sintering,using a combination of active fillers-ZrAl 3 and Al 75 Si *** response surface method is used to optimize the material compositions and sintering process,to achieve shrinkages of less than 0.05%for the entire *** sintering expansion mechanism is investigated by analyzing the pyrolysis and microstructures of samples at different *** combination of ZrAl 3 and Al 75 Si 25 can attain the continuous expansion of the matrix in a wide temperature range of 600-1400°***,typical alumina com-ponents are fabricated and used to verify the effectiveness of the proposed *** to shrinkage suppression,the profile deviation of the samples is less than 0.1 mm,and the proportion of microcracks is reduced by 97.8%.The suggested approach shows potential applications in near-net,low-defect fabrica-tion of complex fine ceramic components.

关键词： Porous oxide ceramics sintering-induced shrinkage Oxidation reaction reaction sintering

Microstructure and mechanical properties of reaction-bonded B_(4)C–SiC composites

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International Journal of Minerals,Metallurgy and Materials 2021年第11期28卷 1828-1835页

作者： Rong-zhen Liu Wen-wei Gu Yu Yang Yuan Lu Hong-bin Tan Jian-feng Yang State Key Laboratory of Materials Processing and Die&Mould Technology School of Material Science and EngineeringHuazhong University of Science and TechnologyWuhan 430074China State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi’an Jiaotong UniversityXi’an 710049China State Key Laboratory of Environment-Friendly Energy Materials School of Materials Science and EngineeringSouthwest University of Science and TechnologyMianyang 621010China

reaction-bonded B_(4)C–SiC composites are highly promising materials for numerous advanced technological ***,their microstructure evolution mechanism remains ***,B_(4)C–SiC composites were fabricated through the Si-melt infiltration *** influences of the sintering time and the B_(4)C content on the mechanical properties,microstructure,and phase evolution were investigated.X-ray diffraction results showed the presence of SiC,boron silicon,boron silicon carbide,and boron *** electron microscopy results showed that with the increase in the boron carbide content,the Si content decreased and the unreacted B_(4)C amount increased when the sintering temperature reached 1650°C and the sintering time reached 1 *** unreacted B_(4)C diminished with increasing sintering time and temperature when B_(4)C content was lower than 35wt%.Further microstructure analysis showed a transition area between B_(4)C and Si,with the C content marginally higher than in the Si *** indicates that after the silicon infiltration,the diffusion mechanism was the primary sintering mechanism of the *** the diffusion process progressed,the hardness *** maximum values of the Vickers hardness,flexural strength,and fracture toughness of the reaction-bonded B_(4)C–SiC ceramic composite with 12wt%B_(4)C content sintered at 1600°C for 0.5 h were about HV 2400,330 MPa,and 5.2 MPa·m^(0.5),respectively.

关键词： reaction sintering B_(4)C-SiC composites mechanical properties microstructural characterization microstructure evolution mechanism

Recycling of High Ferrous Bauxite Reducing Slag for Synthesis of CaAl_2Si_2O_8-Al_2O_3-CaAl_(12)O_(19) Composite

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Journal of Iron and Steel Research International 2016年第12期23卷 1255-1261页

作者： Ying-yi ZHANG Yuan-hong QI Zong-shu ZOU College of Materials Science and Engineering Chongqing University State Key Laboratory of Advanced Steel Processes and Products Central Iron and Steel Research Institute School of Metallurgy Northeastern University

CaAl2 Si2 O8- Al2 O3- CaAl12 O19）（CAS2- Al2 O3 -CA6 ） composite was synthesized through reaction sintering alumina and bauxite reducing slag. The CAS2-Al2 O3-CA5 composite was mainly composed of α-Al2O3 , CAS2 , and CA6. Gehlenite （Ca2 Al2 SiO7 , C2 AS） phase was effectively transformed to CASe and CA6 through high-temperature reaction sintering under weak oxidizing atmosphere at 1400 ℃for 4 h. SEM （scanning electron microscopy） and EDS （energy dispersive spectroscopy） analysis indicated that black and needle-shaped Al2O3, rhombic or irregular polygonal shaped FeAl2O4 , and glassy phase Ca2 Al2 SiO7 disappeared after the reaction sintering. The light gray and flaky hexagon crystals of CaAl12 O19 （10 μm） and the grainy particles of Al2O3 （2-7 μm） were observed in the CASe-Al2 O3-CA6 composite. The gray crystals of CASe act as the binding phase and are distributed around CA6 and Al2O3. CAS2-Al2O3-CA6 composite exhibits high refractoriness and service temperature, which are 1 650 ℃ and 1 450 ℃, respectively. reaction sintering of alumina and bauxite reducing slag is a feasible method for the synthesis of CAS2-Al2 O3-CA6 composite.

关键词： calcium hexaluminate composite reaction sintering bauxite reducing slag phase transformation

Microstructure and Temperature Distribution in ZnAl_2O_4 Sintered Body by Pulse Electric Current

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Journal of Materials Science & Technology 2003年第6期19卷 526-528页

作者： Dongming ZHANG, Zhengyi FU and Jingkun GUOState Key Lab. of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China Wuhan Univ Technol State Key Lab Adv Technol Mat Synth & Proc Wuhan 430070 Peoples R China

Microstructure of reaction sintering of ZnAl2O4 at 1500℃ by hot-pressing(HP) and pulse electric current was investigated. The results indicated that the existed cracks in sintered body were caused by structure mismatch. It is the evidence that periodical temperature field existed during pulse electric current sintering of nonconductive materials. The distance between high temperature areas was related to die diameter.

关键词： Pulse electric current sintering reaction sintering ZnAl2O4,Microstructure Temperature distribution.