Advanced Materials Research Vol. 454

Abstract: In the present paper the Ti-6Al-4V alloy with α and β phases was deformed by hot rolling and solution heat treated at different temperature for 30 minutes to investigate the transformation of (α+β) to β. The results show that the deformed alloy possesses the typical (α+β) dual-phases microstructure, when the alloy is treated below the 950 °C. With the increase of the heat treatment temperature the volume of α phase decreases significantly. When the temperature is higher than the 970 °C, almost no α phase is left in the alloy.

Abstract: Mg-Al layered double hydroxide was synthesized by the method of mechanochemistry /crystallization at the dry milling time of 6 h, wet milling time of 2 h, milling speed of 250 r/min, and ball to powder weight ratio of 50 to 1 using brucite, Al(OH)₃ and Na₂CO₃ as the raw materials. Characterizations of the materials were achieved by XRD, TEM, FT-IR and TG-DSC. The results showed that well crystallized Mg-Al LDH with average partical size of 40 nm were synthesized under this condition. Mg-Al LDH was formed with CO₃^2- freely intercalated between the hydroxide host layers. The material generally decomposed via two distinct stages. The first stage at 229.5 °C was attributed to the loss of interlayer water, and the second stage at 407.8°C was due to the loss of hydroxyl groups from the brucite-like layer, as well as of the carbonate irons.

Abstract: Layered LiV₃O₈ cathode material was prepared by sol-gel method using ethylene diamine tetra-acetic acid (EDTA) as chelon, and LiV₃O₈/MWCNTs composite materials were fabricated by mixing multi-walled carbon nanotubes (MWCNTs) and LiV₃O₈ particles via ball milling technic. X-ray diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge-discharge experiments were employed to characterize the material structure, morphology and electrochemical properties respectively. The results show that the layer structure of LiV₃O₈ did not change after doping MWCNTs, and the LiV₃O₈/MWCNTs composite showed excellent electrochemical performance. The initial specific discharge capacity of the 2% MWCNTs （mass percent） composites can reach 217.5 mAh/g at 0.1C discharge rate in the potential region 1.8-4.0V, and maintains a stable capacity of 224.9 mAh/g within 30 cycles. Comparing to the LiV₃O₈/MWCNTs, the capacity of pure LiV₃O₈ samples can only remain 86% intetial specific capacity at the same test conditions.

Abstract: Co/ WC composite powders (with 10 wt% content of Co) were synthesized by direct mechanical grinding in a rotary-vibration mill. The powders with different mill time were evaluated. WC and WC/Co composite coatings were prepared by supersonic plasma spraying. The results showed that the milled powders consist of composite particles that were formed in the first 2h of milling. Longer milling times improve the distribution of phases inside the composite particles. The formation of the composite particles involves sequential steps of deformation, fragmentation, cold welding, work hardening and piercing of particles of the hard phase in the soft phase. X-ray spectra of the sprayed coating are shown that only very weak W2C and Co6W6C peaks are observed. Compared with WC coating, the Co/ WC coating is denser, and less large pores within composite coating.

Abstract: Here we reported that the Si-O-C nanoballs (SCONBs) were yielded from polyorganosiloxane, polydimethylsiloxane, by chemical vapor deposition (CVD) method. The composite nanoballs with a range of diameters from 50 to 200nm were composed of silicon, carbon and oxygen based on analysis of EDX. At the transmission electron microscope(TEM) and scan electronic microscope(SEM), two populations of nanoballs were found: around 200nm and 500nm. X-ray diffraction patterns demonstrated that the nanoballs were dominatingly amorphous. Temperature played an key role in size distribution of Si-O-C nanoballs, and the 850–900°C temperature range was typical for nanoparticles growth via CVD.

Abstract: In order to figure out whether Gallium works in the superalloy K444, its composition was modified by adding about 0.003 wt.% and 0.01 wt.% Ga, respectively. Microstructure of the modified superalloy K444 after standard heat treatment was investigated by using optical microscopy(OM),scanning electron microscopy(SEM) and energy dispersive spectroscopy (EDS). The primary dendritic distance of these alloys had no significant changes with the increasing of Ga content, and there were no significant changes for the grain size of the three alloys. The content of eutectic was most in the alloy containing 0.01wt.% Ga, and the morphology of eutectic was most irregular. The segregation of other elements was effected by Ga and the elements of Cr and Zr were segregated seriously in the alloy containing 0.01wt.% Ga.

Abstract: The magnesium oxysulfate whiskers/PP composites were prepared by melt-extrusion with modified whiskers as fillers. The mechanical performances including the tensile strength, elongation at break and elastic modulus were tested by electronic universal testing machine.The effect of surface modifier on the mechanical properties of the composites was studied. In general, the mechanical properties of the composites of the zinc stearate modified whiskers/PP were better than it modified by coupling agent KH550. when the contents of the whiskers modified were 20%, the mechanical properties of the composites got the best. There occurred different organic molecule membranes on the surface of the modified whiskers, which lowered the interfacial energy of whiskers. So modified whiskers had different strengthening with PP matrix.

Abstract: LY12 aluminum alloy samples were treated by micro-arc oxidation in sodium metasilicate electrolytes with graphite powder. The effects of graphite concentration on thickness, roughness, friction coefficient and phase composite of ceramic coating were investigated. The results indicated that the roughness and friction coefficient of ceramic coatings increased linearly. However, the thickness decreased adding graphite powder. XRD analyses indicated that the ceramic coatings fabricated on the surface of aluminum alloys by micro-arc oxidization were composed of graphite phase. SEM showed that the porosity of the ceramic coatings with distributing nonuniform micropore diameter were inceased with the increasing graphite concentration.

Abstract: In this paper, uses composite template, through the hydrothermal synthesis of mesoporous zeolite, and N2 adsorption specific surface area measurement instrument, scanning electron microscopy ( SEM ) on mesoporous zeolite pore size, morphology characterization, the crystallization pressure, crystallization temperature, crystallization time on mesoporous zeolite pore size, specific surface area, morphology of the impact. The results show that : the selection of P123 composite beer yeast as template agent, under the condition of high pressure crystallization ( control crystallization pressure 2.3MPa ), crystallization temperature of 110°C, the crystallization time is 72h, prepared by 10nm, specific surface area pore size of 400m2 / g mesoporous zeolite.

Abstract: The infrared absorption behaviors of nano-MgO with different sizes have been investigated based on XRD and IR data. The blue shifts of infrared absorption peaks with the decrease of the particles size have been analyzed by constructing one-dimensional vibration model. Adopting the quantum physics analyzed method, we provide the reasonable explanations for the red shifts of infrared absorption peaks as the average particle size of nano-MgO powder is down to less than 50 nm.