Journal of Asian Ceramic Societies

Tezuka, Keitaro; Kase, Saori; Shan, Yue Jin

doi: 10.1016/j.jascer.2014.07.009pmid: N/A

AbstractBismuth chalcogenides (Bi2X3, X = S, Se, Te) were synthesized from the elements under hydrothermal condition. Single phases of Bi2S3 and Bi2Se3 were produced at 240 °C. Bi2Te3 was obtained as an almost single phase with a small amount of Bi2TeO5. From the results of control experiments without water, the hydrothermal condition in the production of Bi2S3 was more effective than that of Bi2Se3. The particles of obtained Bi2S3 were spherical, with a diameter of ∼1 μm. The Bi2Se3 particles were in a plate-like form, with a width of ∼1 μm and a thickness of ∼0.2 μm.

Kumar, Pattem Hemanth; Srivastava, Abhinav; Kumar, Vijay; Singh, Vinay Kumar

doi: 10.1016/j.jascer.2014.08.001pmid: N/A

AbstractA new class of conventional and low-cement ferrochrome slag-based castables were prepared from 40 wt.% ferrochrome slag and 45 wt.% calcined bauxite. Rest fraction varied between high alumina cement (HAC) acting as hydraulic binder and calcined alumina as pore filling additive. Standard ASTM size briquettes were prepared for crushing and bending strengths evaluation, and the samples were then subjected to firing at 800, 1100 and 1300 °C for a soaking period of 3 h. The microstructure and refractory properties of the prepared castables have been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), cold crushing strength, modulus of rupture and permanent linear changes (PLCs) test. Castables show good volume stability (linear change <0.7%) at 1300 °C. The outcomes of these investigations were efficacious and in accordance with previously reported data of similar compositions. High thermo-mechanical and physico-chemical properties were attained pointing out an outstanding potential to increase the refractory lining working life of non-recovery coke oven and reheating furnaces.

Ghosh, Sourav; Dalapati, Rana; Naskar, Milan Kanti

doi: 10.1016/j.jascer.2014.08.002pmid: N/A

AbstractMesoporous alumina was synthesized by hydrothermal method at 150 °C for 6–24 h using tetramethyl urea followed by their calcination at 500–1100 °C. The samples were characterized by XRD, FTIR, N2 adsorption–desorption, FESEM and TEM. The γ-Al2O3 was found to be stable up to 1000 °C for the samples prepared at 150 °C/6 h, and up to 900 °C for the samples prepared at 150 °C/12–24 h. The BET surface area values of 500 °C treated samples were 428 m2 g−1, 393 m2 g−1, and 366 m2 g−1 for the reaction time of 6 h, 12 h and 24 h, respectively. FESEM and TEM showed the formation of alumina nanoparticles at 150 °C/6 h, which ripened to flake-shaped alumina comprising of alumina nanoflakes (70–100 nm) at 150 °C/12–24 h. To understand the role of tetramethyl urea, a tentative formation mechanism was illustrated.

Djobo, J.N.Y.; Tchadjié, L.N.; Tchakoute, H.K.; Kenne, B.B.D.; Elimbi, A.; Njopwouo, D.

doi: 10.1016/j.jascer.2014.08.003pmid: N/A

AbstractThe aim of this work is to valorize volcanic scoria by using them as starting material for geopolymers production. Nevertheless, volcanic scoria possesses low reactivity. Various amounts of metakaolin (5%, 10%, 15%, 20% and 25%) were added into two volcanic scoria (ZD and ZG) in order to improve their reactivity. Two alkaline solutions were used to activate the aluminosilicate materials. The starting materials were characterized by particle size distribution, specific surface area, chemical and mineralogical composition. The geopolymers were characterized by the setting time, XRD, FTIR, SEM and compressive strength. The results indicated that volcanic scoria have low specific surface area (2.3 m2/g for ZD, 15.7 m2/g for ZG), high average particle size (d50 = 13.08 μm and 10.68 μm for ZD and for ZG respectively) and low glass phase contents. Metakaolin have a smaller average particle size (d50 = 9.95 μm) and high specific surface (20.5 m2/g). The compressive strength of geopolymers increased in the ranges of 23–68 MPa and 39–64 MPa for geopolymers from ZD–MK and ZG–MK respectively. This study shows that despite the low reactivity of volcanic scoria it can still be used to synthesize geopolymers with good physical and mechanical properties.

Yang, Wei; Dong, Shijie; Luo, Ping; Yangli, Anzhuo; Liu, Qi; Xie, Zhixiong

doi: 10.1016/j.jascer.2014.08.005pmid: N/A

AbstractAl2O3–TiB2 composites were synthesized using high-energy ball milling from starting powders containing Al, TiO2, and B2O3. To explore the effect of the addition of another ductile metallic phase during milling, 15 wt.% Ni was added to a sample of the starting powders. The phase transformations and microstructure of the milled powder mixtures were investigated using X-ray diffraction and electron microscopy. The results showed that the Ni addition facilitated the mechanochemical reaction between the Al, TiO2, and B2O3. Before the appearance of the Al2O3–TiB2 composite, the intermediate product NiAl was formed by a gradual exothermic reaction. With continued milling, the final phases of Al2O3–TiB2 and Ni were obtained.

Thirumalaikumarasamy, D.; Shanmugam, K.; Balasubramanian, V.

doi: 10.1016/j.jascer.2014.08.006pmid: N/A

AbstractPlasma sprayed ceramic coatings are successfully used in many industrial applications, where high wear and corrosion resistance with thermal insulation are required. The alumina powders were plasma sprayed on AZ31B magnesium alloy with three different plasma spraying parameters. In the present work, the influence of plasma spray parameters on the corrosion behavior of the coatings was investigated. The corrosion behavior of the coated samples was evaluated by immersion corrosion test in 3.5 wt% NaCl solution. Empirical relationship was established to predict the corrosion rate of plasma sprayed alumina coatings by incorporating process parameters. The experiments were conducted based on a three factor, five-level, central composite rotatable design matrix. The developed relationship can be effectively used to predict the corrosion rate of alumina coatings at 95% confidence level. The results indicate that the input power has the greatest influence on corrosion rate, followed by stand-off distance and powder feed rate.

Godara, Sanjay; Sinha, Nidhi; Ray, Geeta; Kumar, Binay

doi: 10.1016/j.jascer.2014.09.001pmid: N/A

AbstractPhase-pure multiferroic bismuth ferrite (BFO) nanoparticles were synthesized by energy efficient, simple and low temperature sol–gel followed by auto-combustion route. Highly crystalline and well-shaped BFO nanoparticles of size about 50 nm were observed in TEM. Thermal analysis was used to optimize the calcination temperature as 500 °C. An endothermic peak at 834 °C has been detected in the DTA curve, representing the Curie temperature. The dielectric anomaly around Neel temperature (TN) was observed signifying the magnetoelectric coupling. The BFO nanoparticles were found to be highly resistive (ρ ∼ 3 × 109 Ω-cm) and had very low leakage current of the order of μA/cm2, which resulted from phase purity. A significantly enhanced weak ferromagnetism was observed due to smaller particles size and remnant magnetization and coercive field were 0.067 emu/g and 185 Oe, respectively. P–E loop confirmed the ferroelectric behavior of BFO nanoparticles. The direct band gap energy was calculated to be 2.2 eV from UV–vis studies.

Shimonosono, Taro; Ikeyama, Syota; Hirata, Yoshihiro; Sameshima, Soichiro

doi: 10.1016/j.jascer.2014.09.002pmid: N/A

AbstractPorous silicon carbide ceramics were fabricated by liquid phase sintering with 1 wt% Al2O3–1 wt% Y2O3 additives during hot-pressing at 1400–1900 °C. The longitudinal strain at compressive fracture increased at a higher porosity and was larger than the lateral strain. The compressive Young's modulus and the strain at fracture depended on the measured direction, and increased with the decreased specific surface area due to the formation of grain boundary. However, the compressive strength and the fracture energy were not sensitive to the measured direction. The compressive strength of a porous SiC compact increased with increasing grain boundary area. According to the theoretical modeling of the strength–grain boundary area relation, it is interpreted that the grain boundary of a porous SiC compact is fractured by shear deformation rather than by compressive deformation.

Hayashi, Koichiro; Wataru, Sakamoto; Yogo, Toshinobu

doi: 10.1016/j.jascer.2014.09.003pmid: N/A

AbstractSilica nanoparticles containing covalently linked iodine and a near-infrared (NIR) fluorescence dye, namely porphyrin, have been synthesized through a one-pot sol–gel reaction. These particles are called iodinated silica/porphyrin hybrid nanoparticles (ISP HNPs). The ISP HNPs have both high X-ray absorption coefficient and NIR fluorescence. The ISP HNPs modified with folic acid (FA) and polyethylene glycol (PEG), denoted as FA-PEG-ISP HNPs, enabled the successful visualization of tumors in mice by both X-ray computed tomography (CT) and fluorescence imaging (FI). Thus, the FA-PEG-ISP HNPs are useful as contrast agents or probes for CT/FI dual-modal imaging.