Advanced Materials Research Vols. 239-242

Abstract: This review paper discusses the temperature behavior and thermal event of cesium dihydrogen phosphate (CsH₂PO₄) in both ambient and high pressure atmosphere. A complete transition from the room-temperature to a high-temperature of CsH₂PO₄ (monoclinic to cubic phase) occurs between 230 to 240 °C, even in the absence of humid conditions and the superprotonic transition precedes the onset of the dehydration/chemical decomposition of the title compound. Decomposition or dehydration can be avoided by either keeping the sample under a H₂O-saturated atmosphere, or subjecting the sample to a pressure of 1.0 ± 0.2 GPa.

Abstract: A new electrochemical biosensor based on the immobilization of horseradish peroxidase(HRP) on TiO₂ nanoneedles modified electrodes has been fabricated. The direct electrochemical response of HRP immobilized on the modified electrode was dramatically enhanced. The immobilized HRP displayed a couple of stable and well-defined redox peaks with a formal potential of -0.379 V (vs. SCE). The HRP/TiO₂ nanoneedles modified electrode exhibited a remarkable electrocatalytic activity toward the oxidation of H₂O₂. The amperometric response to H₂O₂ showed a linear range of 4–700μmol/L, with the calculated detection limit of 0.78 μmol/L at a signal-to-noise ratio of three. The modified electrode displayed an acceptable reproducibility and good stability. The new HRP/TiO₂ nanoneedles matrix is expected to have wide applications for enzymes and proteins immobilization and direct electron transfer study and opened a way for low conductivity electrode biosensors.

Abstract: The partially devulcanization of waste tire rubber vulcanizate was carried out with the newly developed mechanochemical pan mill, which can exert fairly strong compressing and shearing force on the milling materials and avoid the agglomeration phenomenon. The experimental results indicate that the particle size is greatly reduced and the surface is fluffier, crosslink density is reduced to one half without large degradation and heavy damage of rubber backbones. The study of mechanical properties of revulcanizate of SBR and waste tire rubber blends at 1:1 ratio indicates that elongation at break increased from 302% to 447.6%. But the properties of tensile strength, modulus and hardness are reduced. The mechanochemical pan milling process is a simple, low cost and environmental-benign process for waste tire rubber devulcanization at ambient temperature without any use of chemicals and can be used at commercial-scale.

Abstract: The accurate prediction of warpage of injection molded parts is important to achieve successful mold design with high precision. In this study, effects of polymer-filler properties, such as filler aspect ratio (L/D), filler modulus parallel to major axis (E1) and filler modulus perpendicular to major axis (E2), on warpage displacement of automobile door were studied quantitatively by experimental investigation and numerical simulation. The numerical results are in good agreement with the experimental measurements. It is also found that: (1) the thermal displacement decreases as E1 and E2 decrease, (2) the PVT displacement is not influenced by change of L/D, E1 and E2, (3) the orientation effect displacement is neglected small when L/D=1 and E1= E2, and it also increases as L/D and E1/E2 increase.

Abstract: This paper investigated solid freeform fabrication(SFF) and microwave sintering processes of high strength HA porous scaffold. A newly developed SFF method called motor assisted micro-syringe freeform fabrication system was introduced to construct HA scaffolds. Sintering conditions that influenced the phases, microstructure and mechanical strength of scaffolds were discussed. Study of microstructure images and strength test results showed that densification and grain size were found to play an important role in determining the mechanical properties of sintered porous scaffolds, and microwave sintering process could get a sintered scaffold with small grain size and uniform structure more rapidly at lower sintering temperature than that of the conventional sintering. The fabricated HA scaffolds with controlled architecture (interconnected macro pore of 200-400μm, micro pore of 1-10μm within the rods) and improved mechanical properties (45.2MPa, 56.2% porosity ) may find potential applications in bone tissue engineering.

Abstract: We have synthesized the magnetic NiFe₂O₄ nanosheets using a solution method in the presence of hexamethylenetetramine (HMTA). Morphologies, composition and structure of the as-synthesized samples are characterized by field emission scanning electron microscopy (FE-SEM), energy dispersive spectrum (EDS) and X-ray diffraction (XRD), respectively. Fourier transform infrared (FTIR) spectroscopy and vibrating sample magnetometer (VSM) are used to investigate the surface properties and magnetic properties of the NiFe₂O₄ nanosheets. FE-SEM results show that the NiFe₂O₄ nanosheet samples have irregular shape with thickness of about 30 nm. XRD result confirms that the samples belong to the cubic crystal system with an inverse-spinel structure. The NiFe₂O₄ nanosheets possess sub-ferromagnetism with a negligible coercivity and remanence at room temperature. It could become novel magnetic materials with the potential application in sensors, catalyst, and microwave devices.

Abstract: The relationship between the wettability and the roughness structure on silicon surface is studied. The unitary microscale square pillar arrays are fabricated by the way of inductively coupled plasma (ICP). The wettability of water droplets on the silicon surface is changed from hydrophilic to hydrophobic only by introducing microscale pillarlike structure. Furthermore, the scale effects of the unitary rough structure on hydrophobicity are investigated. For those silicon surfaces with a fixed pillar height, the relatively larger scale of grooves leads the droplets wettability state to unstable Cassie state and the contact angle will initially get larger and then decrease with the increase of groove width. The research could provide further insights into the design of functional surface with controllable roughness-induced hydrophobic.

Abstract: The effect of electrode tip shape on strength and microstructure of weld spot in resistance spot welding of AZ31B Mg alloy was studied by experimental investigations. The results show that electrode tip shape which leads to the difference of contact area,current density and temperature at the sheet/ sheet interface have dominant effect on tensile shear strength and microstructure of weld spot. It was found that weld spot had lower strength and smaller deformation by the spherical-flat electrodes compared to the double truncated cone electrodes, and better property of weld joints can be obtained by truncated cone electrodes. At the same time defects, fracture feature and formation causes were analyzed in order to improve the quality of magnesium alloy spot welding joints.

Abstract: This paper studied the impact of different additives and their amount on the performances of unfired magnesia-calcia brick by detecting cold crushing strength, volume concentration, after-firing linear change, slag resistance and microstructure. The results showed that samples with Zirconia or Zircon had relatively high cold crushing strength. The sample with 4% TiO₂ had the maximum volume concentration after firing. With the increase in the amount of additives, contraction occurred to all the samples, in which samples with Zircon had the smallest linear change and the most stable volume. Samples with 4% ZrO₂ and Zircon had better slag resistance.

Abstract: Alloy 600 was studied in NaCl solution for its pitting corrosion behavior in this paper. According to Tafel polarization, impedance analysis, specimen morphological analysis and metal dissolving analysis by AAS, there must be selective de-alloy corrosion happened in localized concentrated environment; corrosion velocity reaches maximum when Cl^- concentration was 100mmol/L.