Journal of Asian Ceramic Societies

Yang, Xiang; Zhao-hui, Chen; Feng, Cao

doi: 10.1016/j.jascer.2014.07.004pmid: N/A

AbstractCarbon fiber-reinforced silicon carbide (C/SiC) composites were well-established light weight materials combining high specific strength and damage tolerance. For high-temperature applications, protective coatings had to provide oxidation and corrosion resistance. The literature data introduced various technologies and materials, which were suitable for the application of coatings. Coating procedures and conditions, materials design limitations related to the reactivity of the components of C/SiC composites, new approaches and coating systems to the selection of protective coatings materials were examined. The focus of future work was on optimization by further multilayer coating systems and the anti-oxidation ability of C/SiC composites at temperatures up to 2073 K or higher in water vapor.

Sadik, Chaouki; Amrani, Iz-Eddine El; Albizane, Abderrahman

doi: 10.1016/j.jascer.2014.07.006pmid: N/A

AbstractProcessing of mullite and alumina based refractory ceramic by unidirectional dry pressing, from two mixtures that include silica sand, pure alumina (PA) and recycled alumina (RA) is described. The samples were sintered up to 1600 °C to study the refractory properties. The fired properties of materials (firing shrinkage, water absorption, density, flexural strength, refractoriness, and SEM microstructure) were evaluated. Promising refractories materials based on mullite and alumina were obtained.

Ma, Yan; Li, Shilin; Li, Qinggang; Wang, Zhi; Shi, Guopu; Wu, Chao; Li, Yuanyuan

doi: 10.1016/j.jascer.2014.07.002pmid: N/A

AbstractA ZrC–SiC matrix was fabricated by means of in situ reaction method, using zirconium salt, silicon powder and phenolic resin as raw materials. The performances of zirconium salt determined the possibility of ZrC–SiC matrix fabricated using them. The reactions were completed at a relatively low temperature (∼1500 °C). With this concept to produce a ZrC–SiC matrix costs can be reduced. Three-dimensional needle Cf/ZrC–SiC composites were successfully fabricated via the polymer infiltration and pyrolysis (PIP) process using zirconium salt, silicon powder and phenolic resin as raw materials.

Wu, Chao; Wang, Zhi; Li, Qinggang; Shi, Guopu

doi: 10.1016/j.jascer.2014.07.007pmid: N/A

AbstractLaminated Ti/Al2O3 composite was fabricated by tape casting and vacuum hot-pressing sintering with intent to research mechanical properties including the fracture strength and toughness. The results showed that the flexural strength and fracture toughness improved according to the amount of layers. When the amount of layers was 35, the flexural strength and fracture toughness reached 361 MPa and 9.72 MPa m1/2, respectively. Based on the observation of microstructures, it was concluded that the improvement of mechanical properties was attributed to various crack propagation (such as crack deflection, crack bifurcation, crack termination and interface dissociation). The characterization of EDX and XRD at interfaces indicated that the initiative diffusion of O2− from Al2O3 to Ti layer led to the passive diffusion of Al3+ (aggregating near the interface) and reacted with Ti to form Ti3Al, Ti[O] and AlTiO2 solid solution.

Miura, Akira; Takei, Takahiro; Kumada, Nobuhiro

doi: 10.1016/j.jascer.2014.08.007pmid: N/A

AbstractWe report on the low-temperature synthesis of submicron-sized Cu3N powder produced from CuO and NaNH2 powder mixture by heating at 150–190 °C in a Teflon-sealed autoclave. The structure was the anti-RuO3 type with a lattice parameter of 0.3814(1) nm, and strong optical absorption was observed below ∼1.9 eV. This synthesis method has the potential of facile control of the reaction with less use of ammonia sources.

Nagai, Tsukasa; Fujiwara, Naoko; Asahi, Masafumi; Yamazaki, Shin-ichi; Siroma, Zyun; Ioroi, Tsutomu

doi: 10.1016/j.jascer.2014.08.004pmid: N/A

AbstractA new easy-to-use process for obtaining fine powders of lanthanum-based perovskite-type oxides (La1−xAexMO3: Ae = Ca, Sr, M = Mn, Co, Fe) with a high specific surface area was successfully developed by the use of polyvinyl pyrrolidone (PVP) as a dispersant. This approach made it possible to prepare a single phase of perovskite by calcining at a lower temperature (600 °C) compared to conventional synthetic processes such as a solid state reaction and citrate process. SEM observations revealed that the oxide prepared with PVP was ca. 20–30 nm in size, while those prepared by the citrate process and solid state reaction were ca. 50 nm and 1 μm, respectively. Furthermore, the results of a thermal analysis in which we heated the precursors for the different reactions support the idea that PVP plays an important role in the formation of the perovskite phase at low temperature.

Minami, T.; Tokuda, Y.; Masai, H.; Ueda, Y.; Ono, Y.; Fujimura, S.; Yoko, T.

doi: 10.1016/j.jascer.2014.07.001pmid: N/A

AbstractWe report the structural analysis of Na+ and Cs+ in sodium cesium silicate glasses by using 23Na and 133Cs magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. In the NMR spectra of cesium silicate crystals, the peak position shifted to higher magnetic field for structures with larger Cs+ coordination numbers and to lower magnetic field for smaller Cs+ coordination numbers. The MAS NMR spectra of xNa2O-yCs2O-2SiO2 (x = 0, 0.2, 0.33, 0.5, 0.66, 0.8, 1.0; x + y = 1) glass reveal that the average coordination number of both the alkali cations decreases with increasing Cs+/(Na+ + Cs+) ratio. In addition, the coordination number of Na+ in xNa2O-yCs2O-2SiO2 glass is smaller than that of Cs+. This difference between the average coordination numbers of the alkali cations is considered to be one structural reason of the mixed alkali effect.

Park, Seung-Young; Na, Chan Woong; Ahn, Jee Hyun; Song, Rak-Hyun; Lee, Jong-Heun

doi: 10.1016/j.jascer.2014.07.005pmid: N/A

AbstractHighly porous NiO–gadolinium-doped ceria (GDC) nano-composite powders are synthesized by a one-pot glycine nitrate process and applied to the fabrication of Ni–YSZ (yttria-stabilized zirconia)-supported tubular solid oxide fuel cells (SOFCs) with a cell configuration of Ni–YSZ/Ni/Ni–GDC/GDC/LSCF (La0.6Sr0.4Co0.2Fe0.8O3−δ)–GDC/LSCF. The power density of the cell is as high as 413 mW cm−2 at 600 °C, which is 1.37 times higher than that of an identically configured cell fabricated using ball milling-derived NiO–GDC powders (301 mW cm−2). The high porosity of the powders and the good mixing between the NiO and GDC primary nanoparticles due to the abrupt combustion of the precursors effectively suppress the densification, coarsening, and agglomeration of NiO and GDC particles during sintering, resulting in a highly porous Ni–GDC anode layer with good dispersion of Ni and GDC particles and a cell with significantly enhanced power density.

Zhao, Qian; Mao, Yulin; Yan, Lu; Lu, Linhang; Jiang, Tingshun; Yin, Hengbo

doi: 10.1016/j.jascer.2014.07.003pmid: N/A

AbstractY/MCM-48 composite molecular sieve was hydrothermally synthesized at different crystallization temperatures and crystallization times using ethyl orthosilicate as Si source and cetyltrimethyl ammonium bromide as template with the aid of fluoride ions and was characterized by X-ray diffraction, N2 physical adsorption technique, scanning electron microscopy and transmission electron microscopy. The thermal, hydrothermal, acidic, and basic stabilities of the Y/MCM-48 composite were investigated. The results show that Y/MCM-48 composite molecular sieve with meso- and microporous structures was synthesized successfully at 120 °C for 36 h. The Y/MCM-48 composite has the surface area of 864 m2/g and the average pore size is ca. 2.48 nm. The bi-porous structure in composite molecular sieve still maintains its stability even after thermal treatment at 800 °C for 4 h or hydrothermal treatment at 100 °C for 48 h. After treatment in 1 mol/L hydrochloric acid solution or 1 mol/L sodium hydroxide solution for 48 h, the Y/MCM-48 composite exhibits good acidic stability. The acidic stability is superior to the basic stability at the same treatment time.

Raveendra, R.S.; Prashanth, P.A.; Hari Krishna, R.; Bhagya, N.P.; Nagabhushana, B.M.; Raja Naika, H.; Lingaraju, K.; Nagabhushana, H.; Daruka Prasad, B.

doi: 10.1016/j.jascer.2014.07.008pmid: N/A

AbstractNanocrystalline meta-zinc titanate (ZnTiO3) ceramic was prepared using a self-propagating solution combustion synthesis (SCS) for the first time using urea as fuel. The product was calcined at 800 °C for 2 h to improve the crystallinity. Powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDAX), high resolution transmission electron microscopy (HR-TEM) and UV–vis absorption spectroscopy were used to characterize the final product. PXRD results show that the ilmenite type rhombohedral structure was formed when the sample was calcined at 800 °C for 2 h. Adsorption experiments were performed with cationic malachite green (MG) dye. ∼96% dye was adsorbed onto nanocrystalline ZnTiO3 ceramic at pH 9 for 30 min of the contact time. The optimum adsorbent dose was found to be 0.45 g/L of dye. Langmuir–Hinshelwood model was used to study adsorption kinetics and first order kinetic model best describes the MG adsorption on ZnTiO3. Antibacterial activity was investigated against gram negative Klebsiella aerogenes, Pseudomonas desmolyticum, Escherichia coli, and gram positive Staphylococcus aureus bacteria by agar well diffusion method. Nanocrystalline ZnTiO3 ceramic showed significant effect on all the four bacterial strains at the concentration of 1000 and 1500 μg per well.