Advanced Materials Research Vols. 194-196

Abstract: A new idea for improving heat fade performance of organic based friction materials was invented; the method is to dope high specific heat material to the matrix for increasing the specific heat capacity of matrix. In this paper, selecting mullite as additive, organic based friction samples doping mullite were prepared by thermoforming methods, the specific heat of samples were analyzed by TG-DSC, and its friction and wear were tested by GB/T 5764-1998 in China. The results show that doping mullite to matrix can dramatically improve the heat fade performance of organic based friction materials, the friction coefficient of samples can keep steady among 0.3-0.4 when the test temperature is from room temperature to 350°C,while the friction coefficient of the reference samples without mullite decline from 0.38 to 0.19.

Abstract: FeNi alloy powders with and without 0.4 % CeO₂ were flame spray welded onto 1045 carbon steel substrate. Vickers microhardness profiles of the coatings were carried out. Sliding wear tests in dry conditions were carried out by means of weight-loss method for several applications in oil industries. For this purpose, Ni-based alloy and high chrome cast iron were used as compared materials. A scanning electron microscope(SEM) was used to analyze the wear phenomena of samples. The result showed that the hardness of the coatings can be improved by addition of 0. 4 % CeO₂, and the anti-adhesion, anti-scratching, and plastic deformation resistance abilities of coatings are increased with the addition of CeO₂.

Abstract: Three binary Fe-based alloys Fe-S, Fe-Si, and Fe-Mn has been designed and melted in order to investigate the effect of static magnetic field on the migration behavior and distribution of the three elements during the solidification process in this study, and microstructure and chemical composition on the samples have been inspected by optical microscopy and Original Position Analysis technologies. It has been found that the magnetic field can effectively change the distribution of S, Si and Mn, and the migration behaviors of the three elements are different.

Abstract: Pulsed electric field has been effectively used to control and modify the solidification process in castings. In this study, a pulsed electric field at 8 volts and 19 kHz has been applied to Fe-P, Fe-S, and Fe-Si binary alloys, and microstructure and elements distribution of the three alloy samples have been inspected. The results indicated that P migrated from cathode to anode while S and Si migrated from both electrodes to the center under the pulsed electric field during the solidification process.

Abstract: The effects of hot-rolling coiling time on texture of a new cold-rolled non-oriented electrical steel containing copper were investigated. The test results showed that the final product texture consists of γ-fibr textures, α-fibre textures and Goss. With adding coiling time ,the density of {111}<110> and {112}<110> decreased,the inverse Goss texture {001}<110> increased. The volume fraction of {100} raised with coiling time. As a certain coiling temperature, it can improve the intensity of textures {100},{110}at proper coiling time.

Abstract: Nano rice starch prepared by ultrasonic-assisted inverse suspension polymerization was investigated on its physicochemical, gel structure and morphology properties. Water solubility index (WSI) under different temperatures and water absorption index (WAI) of nano rice starch and native starch were studied in this paper. WAI of native starch was 8.67%, and that of nano starch increased 38.45%, compared with native starch. WSI of native starch was respectively 0.024%, 0.057%, 0.111%, 0.211% under 30°C, 40°C, 50°C, 60°C, however, that of nano starch respectively increased to 1.32%, 1.430%, 1.527%, 1.513%. Gel strength of nano starch was 3.20g, and native starch increased to 62.87g. The structure of native rice starch granules was polyhedron with pronounced edges, however, granule size of nano starch became small, and nano starch appeared significant agglomeration.

Abstract: Nanoporous SnO₂ with high photocatalytic activity has been successfully prepared by a photochemical method, using SnCl₂ aqueous solution as a precursor. The as-synthesized sample was characterized by XRD, N2 adsorption-desorption and UV-vis. The photocatalytic activity of the sample was evaluated by degrading methylene blue (MB) aqueous solution under the UV light source and was compared with that of the commercial titania (Degussa P25). The results showed that the produced SnO₂ can degrade MB solution quickly and has comparative photocatalytic performance with P25 for degrading MB. This facile method supplies an effective way to prepare SnO₂ photocatalyst.

Abstract: Polystyrene (PS) spheres encapsulated core-shell composites of SiO₂ or TiO₂ nanoparticles were prepared by the spray drying technique and hollow spheres of SiO₂ or TiO₂ nanoparticles were then derived by removing the PS cores with calcinations. The PS spheres were dispersed into the SiO₂ or TiO₂ colloids, forming a suspension and then the suspensions were sprayed to form micrometer-sized droplets, as the droplets rush through the drying chamber, the PS spheres were encapsulated into the core of SiO₂ or TiO₂ particles due to the high temperatures and the instant evaporation, obtaining PS@SiO₂, PS@TiO₂ or PS@SiO₂/TiO₂ core-shell composites. After removing the PS core by calcination at 550°C, SiO₂ or TiO₂ hollow spheres were then derived. The influence of drying temperature, the concentration of the SiO₂ or TiO₂ particles and the ratio of PS sphere to the particles on the structures and specific surface area of the hollow spheres were studied with scanning electron microscopy (SEM) and nitrogen adsorption-desorption measurements.

Abstract: In this work, a combined process for simultaneously manufacturing nanoporous silicon (NPS) and its metallization was present. The key point is the utilization of adjust electrolyte of silver nitrate and the electroplating timing after the NPS etching process. The current-control mode was used to prepare NPS membrane and the obtained pore-size and pillar-depth were about 0.5 μm and 140 μm, respectively. For clarify the metallization quality of studied process, the semiconductor analyzer was utilized to measured current-voltage (IV) characteristic. Compared to NPS with conventional electroplating process, the contact properties of fabricated sample would be effectively improved by the proposed method. The obtained IV characteristic of sample with combined process shows a larger turn-on current about 277 times than other samples.

Abstract: L-Tryptophan and 5-Hydroxy-Tryptophan were used to synthesis the plate-like gold particles. The morphology of gold plates can be tunable from several nanometers to dozens of micrometers by changing reaction conditions. High temperature was not only increased the reaction ratio, but also changed the morphology of gold products. The size of gold plate was determined by the molar ratio of tryptophan to HAuCl₄ . The pH value of HAuCl₄ also played an important role in the formation of gold plates. One more hydroxyl group in the tryptophan enhanced the reducing ability of tryptophan, which was not suitable for the anisotropic growth.