M Reece Pengarang B Vaidhyanathan Pengarang

A case study of the effect of Ni substitution on the sintering behaviours of Ba0.5Sr0.5Co0.8Fe0.2O3 −δ oxygen transport membranes Li Wanga,b, Ying Chenb, Gong Wanga, Yizhe Lib, Mingwen Baib, David Hallb and Rui Doua aTechnology and Engineering Centre for Space Utilisation, Chinese Academy of Science, Beijing, People’s Republic of China; bSchool of Materials, University of Manchester, Manchester, UK ABSTRACT The sintering behaviours of undoped and 8 mol% B-site Ni-doped Ba0.5Sr0.5Co0.8Fe0.2O3 –δ (BSCF) under various conditions are systematically investigated. Ni doping increases the lattice parameter of BSCF. The grain size of the undoped BSCF increases from 1.52 to 64.8μm with increasing sintering temperature from 900 at 1150 °C, while the grain size of the Nidoped counterpart increases from 3.06 to 34.1 μm as the sintering temperature increases from 1000 to 1200 °C. The grain growth kinetics is analysed using the expression Dn = tK0exp (-Q/RT). The grain growth exponent n is found to be 3 for the undoped BSCF and 4.7 for the Ni-doped BSCF. The grain growth activation energy (Q) is 650.7±30 kJ/mol for the undoped BSCF and 803.4±37 kJ/mol for the Ni-doped BSCF. This indicates that the Ni dopant has a negative influence on the densification and grain growth of BSCF. KEYWORD S BSCF; grain growth kinetics; sintering mechanism; Ni dop Effect of calcium carbonate on the preparation of glass ceramic foams from water-quenched titanium-bearing blast furnace slag and waste glass Haibo Wanga,b, Keqin Fenga and Qingzhu Sunb aSchool of Manufacturing Science and Engineering, Sichuan University, Chengdu, People’s Republic of China; bSchool of Materials Engineering, Panzhihua College, Panzhihua, People’s Republic of China ABSTRACT Glass ceramic foams were fabricated with powder sintering technology at a low temperature (900°C), using water-quenched titanium-bearing blast furnace slag (WTS) and waste glass as the primary raw materials. Additionally, calcium carbonate, sodium borate and sodium phosphate were chosen as sintering aids to form excellent performance products. The effects of calcium carbonate additions on foaming process, crystal content, morphology and properties of the prepared samples were systematically researched. The research indicates that increasing the calcium carbonate content made the foaming process harder and the pore size got more uniform. Consequently, the compressive strength and bulk density increased, while the porosity and water absorption decreased. The homogenous porous structures and optimal comprehensive properties were achieved with 5–7 wt-% CaCO3 addition, including a bulk density of 0.79–0.82 g cm–3, porosity of 73.13–75.28%, water absorption of 3.29–3.75% and compressive strength of 13.13–13.85 MPa. KEYWORD S Calcium carbonate; glass ceramic foams; blast furnace slag; sintering Effect of sintering temperature on the microstructures and mechanical properties of sodalite infiltrate all-ceramic material for dental restorations Ghassan Abdul-Hamid Najia,b, Ros Anita Omar a, Ali Dabbagh c and Rosiyah Yahya d aFaculty of Dentistry, Department of Restorative Dentistry, University of Malaya, Kuala Lumpur, Malaysia; bDepartment of Prosthetic Dentistry, College of Dentistry, University of Baghdad, Baghdad, Iraq; cWellness Research Cluster, Institute of Research Management & Monitoring, University of Malaya, Kuala Lumpur, Malaysia; dFaculty of Science, Department of Chemistry, University of Malaya, Kuala Lumpur, Malaysia ABSTRACT Potassium bromide sodalite (KBr-SOD) zeolite has been developed to enhance the mechanical properties of these restorations using a direct in situ hydrothermal condition followed by the sintering process. The purpose of this study was to determine the effects of sintering temperature on the microstructures and mechanical properties of porous alumina (A) and zirconia-toughened alumina (ZTA) discs infiltrated by KBr-SOD. Hundred and twenty discshaped samples were sintered at various temperatures and prepared for biaxial flexural strength and Vickers microhardness tests. The results showed that sintering temperatures from 1100 to 1600°C for both A-SOD and ZTA-SOD samples has resulted in a significant improvement in the density (2.8 and 1.1%, respectively), flexural strength (257 and 254%, respectively), Vickers hardness (109 and 112%, respectively), and Weibull modulus (7.5 and 3%, respectively). The present study concludes that infiltrated SOD material sintered at 1600°C is suitable for the fabrication of all-ceramic dental prostheses with adequate mechanical properties. KEYWORD S KBr-sodalite zeolite; alumina; zirconia-toughened alumina; all-ceramic dental prostheses; in situ hydrothermal process; mechanical properties Environmental blue CoAl2O4 pigment co-doped by Zn2+ and Mg2+: synthesis, structure and optical properties Xiaojin Penga,b,c, Jinshu Chenga,c, Jian Yuana,c, Na Jina, Junfeng Kanga,c, Yansheng Houa,c and Qi Zhangc,d,e aState Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan, People’s Republic of China; bCSIRO Manufacturing, Bayview Avenue, Clayton, VIC, Australia; cGlass and Technology Research Institute of Shahe, Shahe, People’s Republic of China; dState Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, People’s Republic of China; eSchool of Aerospace, Transportation and Manufacturing, Cranfield University, Cranfield, UK ABSTRACT Nano-sized blue solid solutions Zn xMg0.5 −xCo0.5Al2O4 (x = 0–0.5) have been synthesised by the Pechini method. Single-phase ZnxMg0.5 −xCo0.5Al2O4 with crystallite size of ∼40 nm was identified by XRD measurement. The TG-DSC results indicated that the phase formation temperature of ZnxMg0.5 −xCo0.5Al2O4 increased with the substitution of Zn2+/Mg2+ → Co2+ proceeding. The UV–vis spectra illustrated that the Zn0.3Mg0.2Co0.5Al2O4 pigment displayed the most intensive blue colour with the strongest absorbance appearing within the visible region. The FT-IR spectra suggested that the inversion degree of ZnxMg0.5 −xCo0.5Al2O4 pigment reduces with the increase of Zn2+ rather than Mg2+, enabling to control the pigment colour by tuning the Zn2+ content. The FE-SEM images showed an irregular shaped morphology of ZnxMg0.5 −xCo0.5Al2O4 crystal, different from the cubic-like morphology of CoAl2O4 crystal. The XPS results illustrated that the inversion of pure CoAl2O4 pigment is larger than that of Zn0.3Mg0.2Co0.5Al2O4. Both Zn0.2Mg0.3Co0.5Al2O4 and Zn0.3Mg0.2Co0.5Al2O4 show commercial potential in pigments application. KEYWORD S Absorbance spectroscopy; solid solutions; citrate sol–gel method; blue colour; inversion degree Effects of the Langatate crystal quality on the resonance frequency stability of bulk acoustic wave resonators M. Allania,b, N. Batisb, T. Larochec, A. Neharie, H. Cabaned, K. Lebboue, X. Vachereta and J. J. Boya aFEMTO-ST Institute, UFC, CNRS, ENSMM, UTBM, Besançon, France; bINSAT, Université de Carthage, Tunis cedex, Tunisia; cFreq|n|sys, TEMIS Innovation, Besançon, France; dCristal Innov, Sainte-Hélène du Lac, France; eILM Institute, UCBL, Lyon, France ABSTRACT In the time and frequency domain, we need ultrastable crystal resonators embedded in Ultra Stable Oscillators (USO), working at 10 MHz and exhibiting excellent short-term stabilities. Up to now, the quartz crystal fulfils its function. But, Langatate La3Ga5.5Ta0.5O14 (LGT) piezoelectric crystal seems to allow better performances with high quality material. The applications of this domain require high-quality material with reproducible properties. The LGT crystal is grown by the Czochralski method. Its physical and chemical properties and specificities of this growth process induce defects. They can react as ionic and electronic charge carriers and generate conductive losses. To assess the quality of the LGT crystal, we recorded the UV–VIS and IR transmission spectra and measured the electrical resistivity. At least, Y-cut resonators have been designed and manufactured to study the quality of the 10 MHz resonance, particularly its Q-factor, directly linked to the stability of the USO. We studied the effect of air annealing on the resonance frequency quality. KEYWORD S LGT crystal; bulk acoustic wave resonator; resonator quality factor; crystal quality Modelling and experimental measurements of the mechanical response of piezoelectric structures from millimetre to micrometre M. Bavencoffe a, N. Tembhurnikara, B. Negulescu b, J. Wolfmanb and G. Feuillard a aGREMAN, UMR CNRS 7347, INSA Centre Val de Loire, Blois, France; bGREMAN, UMR CNRS 7347, Faculté des Sciences et Techniques, Université François-Rabelais, Tours, France ABSTRACT Laser interferometry techniques have shown their ability to assess the mechanical response of a piezoelectric thin film. To support these investigations, a numerical study based on the finite element method is carried out: three-dimensional modelling of piezoelectric samples from bulk materials to thin films is examined. For each considered sample, a time-dependent analysis and a frequency domain study are performed. By performing time-dependent analysis, we obtain effective piezoelectric coefficient, d33, of the samples. The frequency domain study helps to calculate the frequency response of these samples. The calculated d33 values and the first frequency resonance values are then compared with the experimental data. KEYWORD S Piezoelectric material; laser interferometry; numerical modelling; finite element method; functional characterisation; impedancemetry Photoluminescence properties of Eu3+-doped stalk-like Al2O3 via a hydrothermal route followed by heat treatment Min Zhanga,b, Yibo Wuc, Lin Zhangd, Haoran Zhangc, Boyang Cuic and Zongxu Sunc aState Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai, People’s Republic of China; bState Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an, People’s Republic of China; cCollege of Materials Science and Engineering, Beijing Institute of Petrochemical Technology, Beijing, People’s Republic of China; dMaterials Research and Education Center, Auburn University, Auburn, AL, USA ABSTRACT Uniform Al2O3:Eu3+ samples were successfully fabricated via a hydrothermal method and subsequent thermal decomposition of Eu3+-doped precursors. The sample characterisations were carried out by means of X-ray diffraction (XRD), scanning electron microscope (SEM) and photoluminescence spectra. XRD results revealed Eu3+-doped samples were a pure γ-Al2O3 phase after being calcined at 1173 K. SEM results showed that these Eu3+-doped Al2O3 samples were stalk-like, with an average length of 1.5 μm. Upon excitation at 394 nm, the orange–red emission bands, having wavelengths longer than 580 nm, were to be from 5 D0→7FJ (J = 1, 2) transitions. The asymmetry ratio of (5D0→7F2)/(5D0→7F1) intensity is about 0.54, 2.76, 3.29, 2.86, 3.36, 3.13 for Eu3+ concentrations of 0.1, 0.4, 0.7, 1.0, 1.5 and 2.0 mol-%, respectively. The optimal doping concentration of Eu3+ ions in Al2O3 is 1.5 mol-%. According to Dexter’s theory, the critical distance between Eu3+ ions for energy transfer was determined to be 14 Å. KEYWORD S Hydrothermal route; phosphor; Al2O3:Eu3+; photoluminescence Structural and dielectric relaxor properties of Ba1-xMgxTiO3 ceramics prepared through a hydrothermal route Mamta Shandilyaa, Radheshyam Raia and Aurang Zebb,c aSchool of Physics and Materials Science, Shoolini University, Solan, India; bInstitute for Materials Research, University of Leeds, Leeds, UK; cDepartment of Physics, Islamia College Peshawar, KP, Pakistan ABSTRACT Polycrystalline samples of lead-free Ba1-xMgxTiO3 (where x = 0.05, 0.10, 0.15) have been fabricated by a hydrothermal method. Single-phase perovskite-type X-ray diffraction patterns were observed and samples have a phase with a tetragonal structure at room temperature for all compositions. The SEM image of the powder shows the agglomeration with increment of Mg concentrations. Small grains with average grain sizes of ∼20 ± 5 nm are uniformly distributed over the mesocrystals. TEM specimens show well-dispersed spherical barium magnesium titanate nanoparticles and diameter of these particles is around 270–300 nm. A dielectric study of Ba1-xMgxTiO3 ceramics as a function of temperature suggested that with increasing substitution concentration the dielectric constant decreased and the Curie temperature shifted towards the lower temperature side. The dielectric diffusivity (γ) was found to be maximum (1.86) for substitution of x = 0.10 in Ba1-xMgxTiO3 compounds. The activation energy (Ea) was found to increases with increasing substitution concentration in BMT compounds. KEYWORD S BMT; ferroelectric; X-ray diffraction; SEM; TEM; dielectric constant