In situ synthesis of low silica X zeolite on ceramic honeycombs for adsorption of heavy metals

In this study, a two-step method involving low-temperature aging and high-temperature crystallization was employed for the first time in the in situ hydrothermal synthesis of low silica X (LSX) zeolite on a ceramic honeycomb. The synthesized samples were characterized by X-ray diffraction, scanning electron microscopy and Fourier transform-infrared spectroscopy. The LSX-zeolite-ceramic composites exhibited uniform morphology and had a low silica-to–alumina (Si/Al) ratio of 1.05. The samples were crystallized twice in situ by hydrothermal treatment and the resulting composites exhibited excellent uptake of the heavy metal ion, Cd²⁺, from aqueous solution. Moreover, the composite material could be reused several times after regeneration, and after five cycles, the removal rate of heavy metal ions was still as high as 99 %.     

Enhanced thermoelectric performance of CoSbS_(0.85)Se_(0.15) by point defect

In this study, we report the effect of Zn doping on the thermoelectric properties of Co_(1-x)Zn_xSbS_(0.85)Se_(0.15)solid solutions(x = 0, 0.02, 0.05, 0.08). The results show the dimensionless figure of merit(zT) increases from 0.17 to 0.34 at 875 K for Co_(0.95)Zn_(0.05)SbS_(0.85)Se_(0.15) sample, due to the noticeable decrease in the lattice thermal conductivity by introducing point defect, which is further confirmed by an analysis based on the Debye-CallawayKlemens model. Meanwhile, the thermoelectric power factor is maintained at high temperatures. This work highlights the important role of point defect in improving the thermoelectric performance of CoSbS-based compounds.     

Enhanced thermoelectric properties in Ge-doped and single-filled skutterudites prepared by unique melt-spinning method

In this paper, we determined an effective substitution of Ge at Sb sites in Nd-filled p-type skutterudites, a series of Nd_.9Fe₂Co₂Sb_12-xGe_x compounds with compositions of x?=?0, 0.1, 0.2, 0.3 and 0.4 were synthesized by home-made induction melting, assembled inside the glove box and followed by spark plasma sintering process (SPS). The thermoelectric properties are investigated as a function of Ge doping content with fixed Nd-filler at 0.9 and the formation of skutterudite phase is characterized by X-ray diffraction. All samples possess positive Seebeck coefficients, representing effective p-type doping. It is observed that the electrical conductivity decreases with decreasing Ge doping concentrations while increased with temperature due to bipolar effect. The lightly doped samples (x?=?0.1 and 0.2) have lower lattice thermal conductivity over the entire temperature range, in which x?=?0.2 sample shows the highest ZT value of 0.82 at 700?K, which is 30% higher than that of the Ge-free sample. The improvement in ZT can be attributed to the optimized carrier concentration and reduced thermal conductivity. The enhancement of ZT through Ge doping, coupled with drastically reduced processing time, shows that these compounds may have great potential in application as p-type segments of the thermoelectric devices.     

A numerical model of an oscillating squeeze film between a rubber surface and a rigid surface

A numerical model for the hydrodynamic behavior of an oscillating squeeze film between a rubber surface and a rigid surface is presented. The effects of roughness of the rubber surface on the hydrodynamic force and the leakage flow rate in the squeeze film are analyzed. A modified Reynolds equation, Laplace equation and a three-parameter viscoelastic constitutive equation are solved simultaneously to obtain the pressure distribution in the squeeze film and the deformation of the rubber surface. Equations are discretized into finite difference equations and solved by Gauss-Siedel iteration method. It is found that increasing roughness of the surface profile significantly increases the hydrodynamic force accompanied by a small decrease in the leakage flow rate. Spatial distribution of the roughness of the rubber surface has no significant effect on the leakage flow rate or hydrodynamic force. The results obtained from the presented simple model are compared with the experimental results available in the literature and a very good agreement is found.     

Reinforcing Effects of Modified Nanodiamonds on the Physical Properties of Polymer-Based Nanocomposites: A Review

Exceptional mechanical and other physical properties of nanodiamond (ND) have recently attracted much attention. For thermosetting polymers, the reinforcing effects of as-received and amine-functionalized nanodiamonds on the mechanical and tribological properties have been examined and demonstrated the advantages of covalent incorporation of ND into epoxy structure resulting in strong nanofiller-matrix interface. In epoxy matrix composites, the ultimate mechanical reinforcement was achieved using high loadings level of ND powder along with improved thermal conductivity and reduced friction coefficients. In this regard, several complementary mechanical characterization techniques including pin-on-disk, nanoindentation, vickers, tensile, and compression were used to study the reinforcing mechanisms.     

Synchrotron crystal and local structures,microstructure, and electrical characterization of Cu-doped LiFePO4/C via dissolution method with ironstone as Fe source

Journal of Materials Science: Materials in Electronics - Powders of lithium iron phosphate (LFP) with Cu doping and carbon coating were prepared by a dissolution method using Fe sourced from...     

Ceramic/natural rubber composites: influence types of rubber and ceramic materials on curing,mechanical, morphological,and dielectric properties

Influence of different types of rubber and ceramic material on cure characteristics, mechanical, morphological, and dielectric properties of natural rubber (NR) vulcanizate was studied. Two types of ferroelectric ceramic materials: barium titanate (BaTiO₃) and lead titanate (PbTiO₃) were prepared by solid-state reaction with calcinations at 1100 °C for 2 h. The ceramic powders were then characterized by X-ray diffraction (XRD), particle size analyzer, and SEM techniques. Ceramic/rubber composites were then prepared by melt mixing of rubber and ceramic powders. Two different types of NR (i.e., epoxidized NR [ENR] and unmodified NR) and two types of ceramic powders (i.e., BaTiO₃ and PbTiO₃) were exploited. It was found that incorporation of ceramic powders in rubber matrix and the presence of epoxirane rings in ENR molecules caused faster curing reaction, and higher delta torque but lower elongation at break. This is attributed to lower mobility of molecular chains and higher interaction between ENR molecules. Furthermore, SEM results revealed that the BaTiO₃ composites showed finer and better distribution of the particles in the rubber matrix than that of the PbTiO₃ composite. This caused superior mechanical properties of the BaTiO₃ composites. Furthermore, higher dielectric constant and loss tangent was observed in the ENR/BaTiO₃ composites.     

Structure,thermal properties,dissolution behaviour and biomedical applications of phosphate glasses and fibres: a review

For the last few decades, there has been a growing interest in using glasses for biomedical applications. Bioactive glasses are a group of surface reactive glasses which can initiate a range of biological responses by releasing ions into the local environment. Silicate, borate and phosphate glasses are known to show good bioactive characteristics and could be potentially used as favourable templates for bone-tissue formation. Phosphate glasses are unique group of materials that offer great potential for hard and soft tissue engineering over other types of bioactive glasses due to their fully resorbable characteristics, with some formulations possessing chemical composition similar to the mineral phase of natural bone. Moreover, these phosphate glasses can be prepared as fibres which could be used for soft tissue engineering and as fibrous reinforcement for resorbable polymers such as poly-(lactic acid) for fracture fixation applications. This review details some of the properties of phosphate glasses, such as thermal, viscosity/temperature, dissolution and biocompatibility of and how different factors can effectively alter these properties. The effect of the addition of different modifier oxides on the structure in terms of chain length is included. This review also reports on the manufacturing process, mechanical properties and biomedical application of phosphate glass fibres. A brief comparison between three different types of bioactive glasses has also been presented in this review. The main aim of this review is to present the factors affecting the properties of phosphate glasses and glass fibres and how these may be exploited in the design of a biomaterial.     

Analysis of the optical absorption characteristics of CuInSe2 thin films

Thin films of compound CuInSe₂ have been developed onto glass substrates by in situ thermal annealing of the stack of successively evaporated elemental layers in vacuum. The atomic compositions and the optical properties of the films have been determined by proton-induced X-ray emission (PIXE) method and spectrophotometry in the photon wavelength range of 300–2500 nm, respectively. The typical optical absorption characteristic of the films has been critically analysed. The absorption coefficients vary from 10³ to 10⁵ cm⁻¹ in the measured wavelength range. The films have more than one type of fundamental electronic transitions. Direct allowed and direct forbidden transitions vary between 0.947 to 0.989 eV and 1.099 to 1.204 eV, respectively, depending on the composition of the films. The former transition varies inversely with the Cu/In ratio while the latter shows no such dependence. Valence band splittings due to spin–orbit coupling converge towards the single-crystal value for the near-stoichiometric (NS) and Cu-rich films.