M Reece Pengarang B Vaidhyanathan Pengarang

A simple recoating repair methodology to improve oxidation resistance of C/SiCs Hui Mei, Ding Zhang, Junchao Xia and Laifei Cheng Science and Technology on Thermostructural Composite Materials Laboratory, Northwestern Polytechnical University, Xi’ an, Shaanxi, People’ s Republic of China ABSTRACT Lots of through SiC coating micro-cracks appeared due to the mismatch of thermal expansion coefficient between fibres and matrix, and this could be the diffusion path for oxidising gases to reduce oxidation resistance of as-cracked C/SiCs. In this paper, a simple recoating repair methodology was achieved by grinding off original coating and depositing coating again. The experimental results pointed out that as-repaired specimens had excellent oxidation resistance with the whole temperature range of 500– 1500°C, and at sensitive point of 800°C, the weight loss rate of the as-repaired specimens was decreased by 22.1% compared to the as-cracked specimens. From 700 to 1100°C, the flexural strength of the as-repaired specimens has obviously improved compared to the as-cracked specimens. Microstructural analysis showed that the recoating repair methodology can seal and narrow through-coating micro-cracks, leading to oxidation resistance and mechanical properties improvement for the as-repaired specimens. KEYWORD S C/SiCs composites; recoating repair methodology; oxidation resistance; mechanical property Glass formation and properties of sodium zinc phosphate glasses doped with ferric oxide Shangjiu Niana, Yin Zhanga,b, Jun Lia, Nianying Zhoua and Wen Zoua aSchool of Materials Science and Engineering, Nanjing Tech University, Nanjing, People’s Republic of China; bNanjing Haoqi Advanced Materials Co., Ltd., Nanjing, People’s Republic of China ABSTRACT Approximate glass-forming region of a P2O5–ZnO–Na2O (PZN) ternary system was investigated and determined. The properties of the glasses with ZnO contents between 35 and 50 mol-% were further investigated. When ZnO of 40P2O5–40ZnO–20Na2O glasses is replaced by 1 – 5 mol-% Fe2O3, respectively, the density, Tg and Tf increase first and then decrease, and they showed the maximum value of about 4 mol-% Fe2O3 replacement, while CTE and weight loss vary in opposite ways and showed the minimum value at about 4 mol-% Fe2O3 replacement. Structural studies were carried out by X-ray diffraction, infrared spectroscopy and Raman spectroscopy. With the increase in Fe2O3, the reduction of P=O bond is the main reason for the increase in water resistance of PZNF glass. KEYWORD S Sealing glass; lead-free; chemical durability; fe2O3 In situ synthesis, mechanical and cyclic oxidation properties of Ti3AlC2/Al2O3 composites Weibing Zhoua, Kang Lia, Jiaoqun Zhua,b and Ruguang Lib aSchool of Materials Science and Engineering, Wuhan University of Technology, Wuhan, People’s Republic of China; bState Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan, People’s Republic of China ABSTRACT Ti3AlC2/Al2O3 composite materials were successfully fabricated from TiO2/TiC/Ti/Al powders by the in situ reactive hot pressed technique. The microstructure, mechanical and oxidation properties of the composites were investigated in the paper. Vickers hardness increased with the Al2O3 content. The relative density of Ti3AlC2/Al2O3 composites exhibits a declining tendency with Al2O3 content especially exceeds 10 vol. %. The Ti3AlC2/Al2O3 composites show excellent electrical conductivity. The flexural strength and fracture toughness of Ti3AlC2/10 vol. % Al2O3 are 461 ± 20 MPa and 6.2 ± 0.2 MPa m1/2, respectively. The cyclic oxidation behaviour of resistance of Ti3AlC2/10 vol. % Al2O3 composites at 800–1000°C generally obeys a parabolic law. The oxide scale of sample consists of a mass of α-Al2O3 and TiO2, forming a dense and adhesive protect layer. The result indicates that the Al2O3 can greatly improve the oxidation resistance of Ti3AlC2. KEYWORD S In situ synthesis; properties; Al2O3; Ti3AlC2 Nanovoids in dense hydroxyapatite ceramics after electric field assisted sintering Jondo Yuna,b, Wei Qinb, Klaus van Benthem b, Andrew M. Thronb, Sukyoung Kimc and Young-Hwan Hanc aDepartment of Nano Materials Engineering, Kyungnam University, Changwon, Korea; bDepartment of Materials Science and Engineering, University of California at Davis, Davis, CA, USA; cSchool of Materials Science and Engineering, Yeungnam University, Gyeongsan, Korea ABSTRACT Nanoporous hydroxyapatite (HA) ceramics were consolidated using conventional or free sintering, spark plasma sintering (SPS) and flash sintering (FS). Microstructures formed during electric field assisted sintering, which includes SPS and FS revealed that nanovoids were retained within HA grains during processing. After free sintering, however, no nanovoids were detected by transmission electron microscopy (TEM). The observed nanovoids were confirmed not induced by electron beam damaging, and showed either a round or faceted shape with diameters ranging between 5 and 10 nm. In-situ TEM heating experiments demonstrated that nanovoids remained stable up to 900°C but disappeared at a temperature as high as 1100°C. KEYWORD S Nanovoids; hydroxyapatite; spark plasma sintering; flash sintering; electric field assisted sintering; transmission electron microscopy; beam damage; thermal stability Plasma resistance of quartz with a glass coating layer by aerosol deposition Seunggon Choi, Dae-Yong Jeong and Hyungsun Kim Department of Materials Science & Engineering, Inha University, Incheon, Republic of Korea ABSTRACT To improve the plasma resistance behaviour, glass frits of SiO2–Al2O3–Y2O3 with various powder sizes were coated onto quartz substrates by the aerosol deposition (AD) method. The thickness and microstructure of the coating layers were observed using a surface profiler and scanning electron microscopy. Plasma resistance was measured via the quartz substrate, after exposure to an inductively coupled plasma etcher. The coating layers were densely formed on the quartz substrates without additional heat treatment, and the layer thickness changed for the glass frit size distribution and AD process conditions. The SiO2–Al2O3–Y2O3 glass coating layer showed a higher plasma resistance than quartz. Furthermore, the AD coating layer was evenly etched after plasma exposure. This study improves the lifetime of plasma chamber components in the semiconductor industry. KEYWORD S Glass; aerosol deposition; plasma resistance; quartz; coating Predicting grain size distributions in perovskite-structured Ba0.5Sr0.5Co0.8Fe0.2O3–δ oxygen transport membranes Li Wanga,b, Rui Doua, Gong Wanga, Yizhe Lib, Mingwen Bai b, David Hallb and Ying Chenb aKey Laboratory of Space Manufacturing Technology (SMT), Chinese Academy of Sciences, Beijing, People’s Republic of China; bSchool of Materials, University of Manchester, Manchester, UK ABSTRACT This study is conducted over a 3 × 3 time–temperature matrix on Ba0.5Sr0.5Co0.8Fe0.2O3 −δ (BSCF) ceramics, and sintered bodies above 93% dense are obtained. The electron backscatter diffraction band contrast micrographs of the polished sintered samples are analysed for characterising the grain size distributions (GSDs). This study develops an algorithm for predicting the GSDs of BSCF dependence of sintering condition (time and temperature). In addition, the GSDs predicted by the algorithm agree reasonably with those experimentally observed. When individual grain size is non-dimensionalised by the median grain size, the GSDs data of all BSCF samples reduce to a single self-similar GSD curve. The median grain size is predicted by the classical kinetics equation, Dn = tK0exp( −Q/RT). KEYWORD S BSCF; grain-growth kinetics; grain size distribution; microstructure Preparation of CaO granules using the granulation method Qi Zhanga, Yaowu Weia, Tao Zhanga, Bingqiang Hana, Kui Liub and Bo Chenb aState Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan, People’s Republic of China; bInstitute of Metal Research, Chinese Academy of Sciences, Shengyang, People’s Republic of China ABSTRACT Improving the hydration resistance of CaO particle in manufacturing and application of free CaO-containing materials has practical significance. In this study, CaO granules was made from Ca(OH)2 particles, which were fabricated by the granulation method. The results showed that the hydration resistance of the CaO granules which was prepared under 1700 r min −1 was the best, the CaO granules was sintered well in calcination process, the shell of CaO granules was relatively dense, which improves the hydration resistance of CaO granules, and the rate of hydration weight increment was 0.58% after placed in the air for 20 days under a temperature of 10–14°C and a relative humidity of 57–81%. KEYWORD S CaO granules; granulation method; rotational speed; hydration resistance Study on crosslinking of polymers and joining mechanism of SiC ceramic Bofang Zhoua,b, Keqin Fenga and Hongling Zhoua aSchool of Manufacturing Science and Engineering, Sichuan University, Chengdu, People’s Republic of China; bSichuan Engineering Technical College, Deyang, People’s Republic of China ABSTRACT Based on crosslinking of polymers with different vinyl contents at low temperature and pyrolysis of the polymer at high temperature, joining temperature and impregnation cycles of an SiC joint were discussed. Polyvinylphenylsiloxane as the polymer with active groups of Si–OH and CH=CH2 by crosslinking enhances ceramic yield and thermal stability. The microstructure of the polymer changes from amorphous ceramic into grains of SiO2 and SiC, grains can dispersion strengthening enhances strength of joint layer. Shear strength of SiC joint reaches the maximum at 1200°C. A relatively good interface between the SiC substrate and pyrolysis product of the polymer is formed, but there exist loose cracks or voids in the joint layer which affect the shear strength of the joint. The shear strength of the SiC joint reaches 69.2 MPa through seven times of vacuum impregnation/pyrolysis enhancement. According to the microstructure and properties of the SiC joint, the pyrolysis mechanism of the joining layer as part of the joint by using polyvinylphenylsiloxane is explained. KEYWORD S Joining; SiC ceramic; polyvinylphenylsiloxane; crosslinking; ceramic yield The preparation of LPVCS with high ceramic yield and low oxygen content Weicheng Bai, Ke Jian and Yunliang Shi Science and Technology on Advanced Ceramic Fibers and Composites Laboratory, National University of Defense Technology, Changsha, People’ s Republic of China ABSTRACT As by-products produced by the synthesis of polycarbosilane, RLPS and dimethyldivinylsilane (DVS) can synthesise vinyl-containing liquid polycarbosilane (LPVCS) via hydrosilylation reaction. The structure, thermal curing performance and pyrolysis performance of PVCS are characterised by means of the analysis means such as FT-IR, GPC and TG, etc. According to the result, the structure of PVCS is affected by the different synthesised temperatures and different proportions of introduced DVS. And LPVCS that contains Si– H and – CH=CH2 groups is synthesised under the control of reaction condition. Cross-linking solidity is available at 350°C in an inert atmosphere, and the total ceramic yield of LPVCS is 42.5%. The oxygen content of the pyrolysed product is just about 2.0% after heating in 1000°C, which is a suitable precursor polymer for SiC-based composite. KEYWORD S SiC precursor; selfcrosslinking; hydrosilation; ceramic matrix composites