Abstract: In this paper, a novel humidity sensor based on polymer-carbon nanotube composites was prepared and characterized. Two different methods were adopted to fabricate the humidity-sensing film for these sensors. The surface of the films was observed by a scanning electron microscope (SEM). The sensing material made up of poly(ethyleneimine) and multiwall carbon nanotube was sprayed on the interdigitated microelectrode pairs(IDTs). The resistance between the two electrodes was measured at different relative humidity levels at 19°C. The data shows that the resistance increases with the rise of the relative humidity over the range of 5-90% RH and that, the resistance increases almost linearly in the range of 5-71% RH. The response of the sensors to NO2 and NH3 were also examined, and the results reveal that the sensor is not sensitive to both of them.
Abstract: This paper reports the specimen preparation using an advanced dual beam focused ion beam (FIB) technique for bulk polycrystalline diamond (PCD) composites after dynamic friction polishing (DFP). The technique adapted allows for precisely processing diamond materials at the specific polishing track sites of PCD surface, from which large cross-sectional specimens for SEM/EDS/Raman microanalysis could be successfully created. In addition, an in-situ lift-out method was developed to prepare the site-specific HRTEM specimens which were thin enough for imaging the atomic lattice of diamond and for conducting EELS analysis.
Abstract: The recently developed “quenching and partitioning” heat treatment and “quenching-partitioning-tempering” heat treatment are novel processing technologies, which are designed for achieving advanced high strength steels (AHSS) with combination of high strength and adequate ductility. In present study, a medium carbon steel containing Nb was subjected to the Q-P-T process, and both the microstructure and mechanical properties was studied. The experimental results show that the Nb-microalloyed steel demonstrates high tensile strength and relatively high elongation. The microstructure of the steel was investigated in terms of scanning electron microscope and transmission electron microscope, and the results indicate that the Q-P-T steel consist of fine martensite laths with dispersive carbide precipitates and the film-like interlath retained austenite. The orientation relationships between martensite and retained austenite is as well-known Kurdjurmov-Sachs relationship and Nishiyama-Wasserman relationship.
Abstract: The specific recognization between galactose group and Ricinus Communis Agglutinin (RCA) was investigated by microcantilever. The gold side of the microcantilever was covalently bound with N-galactose, RCA and asialofetuin (ASF) via mixed self assembly monolayer of 11-mercaptoundecanoic acid and 6-mercaptohexanol, respectively. After adding RCA into the flowing cell, the deflection could be observed on the N-galactose or ASF modified microcantilever. Meanwhile, the deflection could also be observed after ASF bound to the RCA modified microcantilever. In order to prove that the deflection is caused by the specific interaction between the galactose group and RCA, bovine serum albumin (BSA) was introduced into the flowing cell as control experiment and no obvious deflection was observed. The specific interaction was also confirmed by the evidence that the bound protein layer can be mechanically removed with atomic force microscopy nanolithography technology.
Abstract: Poly (p-phenylene benzobisoxazole)/Nano-sized titanium dioxide (PBO/TiO2) composites with different TiO2 compositions were prepared through in situ polymerization and the fibers had been successfully spun via dry-jet wet spinning technique. PBO/TiO2 composite fibers were characterized by FTIR spectroscopy, Ubbelohde capillary viscometer, TG analyses and so on. Mechanical property of the fibers was investigated before and after UV accelerated aging which being exposed under ultraviolet radiation for up to 100 hours. Results showed that the molecular weight of PBO in the Nano composites was less declined with low content of TiO2; the thermal degradation temperature of PBO/TiO2 fibers were at less 10°C higher than that of pure PBO fiber in the atmosphere of N2; The pure PBO had a large deterioration in mechanical properties, and in the initial exposure time tensile strength of fibers dropped slowly after TiO2 adding in. From these results, the nano-TiO2 had good UV-aging shielding efficiency for PBO fiber.
Abstract: Montmorillonite (MMT) was applied as the modifying agent, polyethylene glycol bisglycidyl ether as crosslinking agent, Poly(γ-glutamic acid)/montmorillonite (γ-PGA/MMT) superabsorbent nanocomposite was prepared. The effects of crosslinking agent mass, MMT contents and reaction temperature on the saline water absorbency of the superabsorbent nanocomposites were studied. The experimental results demonstrated that the saline water absorbency of γ-PGA/MMT nanocomposites increased with the increasing of crosslinking agent mass firstly and decreased when the crosslinking agent mass was higher than 0.6g. The saline water absorbency of γ-PGA/MMT nanocomposites increased with the MMT contents up to 7% and decreased as the MMT contents further increased. Moreover, the saline water absorbency of γ-PGA/MMT nanocomposites increased with the reaction temperature firstly, and then decreased when the reaction temperature was higher than 50°C.
Abstract: Biphasic calcium phosphate powders doped with zinc (Zn-doped BCP) were synthesized via sol-gel technique. Different concentrations of Zn have been successfully incorporated into biphasic calcium (BCP) phases namely: 1%, 2%, 3%, 5%, 7%, 10% and 15%. The synthesized powders were calcined at temperatures of 700-900°C. The calcined Zn-doped BCP powders were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential and thermogravimetric analysis (TG/DTA) and field-emission scanning electron microscopy (FESEM). X-ray diffraction analysis revealed that the phases present in Zn-doped are hydroxyapatite, β- TCP and parascholzite. Moreover, FTIR analysis of the synthesized powders depicted that the bands of HPO4 increased meanwhile O-H decreased with an increase in the calcination temperature. Field emission scanning electron microscopy (FESEM) results showed the agglomeration of particles into microscale aggregates with size of the agglomerates tending to increase with an increase in the dopant concentration.
Abstract: Rapid solidified Au-Ag-Ge alloy was prepared by the melt spinning method，microstructure and melting behavior of the rapid solidified alloy was investigated by means of SEM, TEM and DSC. DSC results show that liquid temperature of the rapid solidified alloy is about 3～4°C lower than that of the alloy ingot, melting interval is also smaller. Minimum size of 40nm nanocrystalline has formed when the cooling rate is 1.293×106K/sec. Metastable supersaturated precipitated Ge-rich phases have been found at the grain boundaries, a structure mutation was found in the thickness direction of the rapid solidified alloy. Meanwhile, due to the stabilization transition of the supersaturated precipitated phase of the rapid solidified alloy, an exothermic peak has formed in the DSC curve, temperature of the exothermic peak becomes much lower when the cooling rate increases.
Abstract: Processes with severe plastic deformation (SPD) may be deﬁned as metal forming processes in which ultra-large plastic strain is introduced into a bulk metal in order to create ultra-ﬁne grained (UFG) metals. Accumulative roll bonding (ARB) is a SPD process that may be deﬁned as multisteps rolling process in order to create high strength metals with UFG structure. In this study, ARB process with inter-cycle annealing is carried out on the commercial purity aluminium (AA1050) sheet up to 13 cycles. The purpose of the present study is investigation of microhardness behavior and microstructural evolution in the ARB processed AA1050 sheet. Micro-Vickers hardness measurement is carried out throughout thickness of the ARB processed sheets. In addition, with increasing ARB cycles the grains size is reduced in nanometer level.
Abstract: Microhardness of nitrated and carbonitriding in electrolyte plasma steel Р6М5 surface layers are investigated in the research. It shows perspectiveness of the cutting tool electrolyte-plasma treatment technology. Operating conditions for the technology realization are defined. It was also indicated the desired content of components in saturating mixtures by nitriding and carbonitriding. Comparative research of structure, phase composition of fast-cutting P6M5 steel modified surface layers after electrolyte plasma treatment was carried out by scanning-electron and light microscopy, and X-ray structure analysis methods. The way of electrolytic plasma nitriding in cathodic mode, to provide fast-cutting steels which allows for modification the surface and high kinetic efficiency the process diffusion saturation. It was established that as a result of nitriding and nitrocarburizing in plasma electrolyte has been a significant increase in microhardness in the surface layers of steel Р6M5.