Materials Science Forum Vols. 544-545

Abstract: The oxidation behavior and electrical resistivity of reaction-bonded silicon carbide (RB-SiC) at high temperature (900 °C) had been studied in this paper. The results showed that the weight of RB-SiC would be increased when it was oxidized at 900
. The relationship between the weight-gain of RB-SiC and oxidation times followed the parabolic curve. The oxidation resistance of RB-SiC at 900
could increased by the increase of SiC particles sizes. But the electrical resistivity of RB-SiC had not affected by the oxidation at 900
. The oxidation mechanism of RB-SiC and the affecting factor on oxidation of RB-SiC were analyzed and discussed.

Abstract: Thermal conductivity of polyetheretherketone (PEEK) with fillers was investigated. By adding the hybrid fillers to polymer the thermal conductivity of composites was increased significantly. Thermal diffusivity of composites was measured using laser flash method. Synergistic filler effect between particulate SiC and carbon fiber (CF) was observed for thermal conductivity. In a PEEK based composite, thermal conductivity increased to 8.25 W/m-K for a 50 vol% hybrid filler (SiC+CF) system, whereas the thermal conductivity of 40 vol% CF was 3.1 W/m-K and 50 vol% of SiC was 2.4 W/m-K, respectively. The use of hybrid filler was found to be effective in increasing thermal conductivity of its composites due to formation of effective thermal conductive path. Experimental results of two-phase system were compared with Nielsen prediction.

Abstract: The effect of transformation temperature and phase transformation characteristics by alloying method of CuZnAl shape memory alloy with a small of misch metal and Zr contents were investigated. The addition of misch metal and Zr was very effective for reducing the grain size. After solution treatment, the specimens were post-quench aged or step quenched at 373K to 623K for variation of hardness value. It was found that the hardness value was very increased at 473K and 523K. The fracture mode has been changed from trans granular brittle fracture to ductile fracture with void formation and coalescence by the addition of misch metal and Zr. Ageing of the β-phase decreased the Ms temperature, but that of the martensite phase increases the As temperature. The change in As temperature with post-quench aging can be attributed to recovery of order in the β-phase.

Abstract: Carbon/carbon (C/C) composites with smooth laminar texture pyrocarbon (SL), rough laminar texture pyrocarbon (RL) and RL pyrocarbon adding particle resin carbon were prepared, respectively. The open porosities of the composites were measured by Archimedes principle, and their mechanical and thermophysical properties were tested. The friction properties of the braking disc prepared from the three types C/C composites were tested at stimulating airplane braking conditions. The friction coefficient of the SL C/C composites with is 0.26 under normal landing condition. For the RL C/C composites with open porosity of 13%, the friction coefficients are 0.35, 0.24, 0.29 under normal landing (NL), rejected take-off (RTO), damp landing (DL) conditions, respectively. The friction coefficients of C/C composites with RL pyrocarbon adding particle resin carbon (open porosity is 8%) are 0.36, 0.31, 0.36 under NL, RTO, DL conditions, respectively. The results show that the RL pyrocarbon increases the friction coefficients of the C/C. The addition of particle resin carbon in the C/C increases the braking efficiency of C/C composites under high energy landing. Low porosity C/C has better braking efficiency under DL condition.

Abstract: Ti-Ca-P films on commercial pure (cp) titanium plates were uniformly deposited using dual target RF magnetron sputtering apparatus with DC magnetron sputtering system under the conditions of 50 W DC power to a cp titanium target and 200 W RF power to a β-tricalcium phosphate (β-TCP) target for 60 min in 2.2×10-1 Pa Ar. Resulting samples had smooth surface like mirror. Crystal structure of the film was amorphous. The film had the chemical composition of about 3: 1.7: 1: 11 in Ti: Ca: P: O ratio under controlling the β-TCP target RF sputtering power and the titanium target DC sputtering power. The film and the method are expected to be useful for remodeling surfaces of various titanium implants.

Abstract: The influence of wheel speed and melt temperature on the surface characteristics of slag fibers were examined in mineral fibers synthesized from the steel-making slag, using a modified melt extraction method, i.e. melt spinning. The synthesized fibers were characterized by optical microscope and scanning electron microscopy. It was found that the wheel speed of 700 rpm generated better quality of mineral fibers in terms of diameter and length. This was attributed to the relative extent of contact width between the flowing melt and the rotating wheel. The thickness of the slag fibers were also decreased with increasing the slag melt temperature due mainly to significant decrease in the viscosity of the slag melt. In addition, the lower melt temperature caused an increase in number of shots plus the mineral fibers.

Abstract: The present study examined the effect of the activation properties of granulated blast furnace slag according to the type of alkaline activator, the specific surface area of blast furnace slag, and the amount of ordinary Portland cement substituted on the compressive strength of the cement containing blast furnace slag. For activators, Na2SiO3, Na2CO3, NaOH, and Na2SO4 were used. Na2SiO3, Na2CO3, and Na2SO4 were converted into Na2O, to which 1 wt.%, 3 wt.%, 5 wt.%, and 7 wt.% were added, and subjected to experimentation, with the W/S (water/solid) ratio = 0.5. The principal hydration products were C-S-H, C4AH13, Aft (ettringite), and Al(OH)3. Na2CO3 exhibited the largest slag hydration rate. Consequently, the present study used Na2CO3 as the alkaline activator. The compressive strength of blast furnace slag cement mortar was then measured according to the amount of Na2CO3 added (2.5 wt.% and 5.0 wt.%), the specific surface area of blast furnace slag (4,000 cm2/g, 6,000 cm2/g, and 8,000 cm2/g), and the substitution rate (30 wt.%, 50 wt.%, and 70 wt.%) of the blast furnace slag in terms of ordinary Portland cement. The results are as follows: at the ages of 1 day and 3 days, respectively, the early strength increased as the specific surface area of blast furnace slag and the amount of alkaline activator added increased; at the age of 7 or more days, the compressive strength increased as the amount of alkaline activator added decreased and as the specific surface area of blast furnace slag increased.

Abstract: Thermal stabilization is used to reduce the turbidity of spent foundry sands (SFSs). Effect of stabilized temperature and thermal stabilized time in thermal stabilization is estimated by turbidity of SFSs in thermal stabilization. The turbidity of furan sand is 984 FAU and almost 15 times as high as that of other sands such as CO2 sand and green sand. Furan sand contains furan resin, but CO2 sand and green sand do not use resin chemicals. The turbidity of furan sand can be reduced by stabilization of furan resin in thermal process. In the process of thermal stabilization, fixation of furan resin by heating occurs and resin can be in the state of insolubility. The turbidity of furan sand is sharply decreased within thermally stabilized time of 2 hrs and decreased with increasing stabilized temperature. Turbidity in thermal stabilized time of 2hrs and stabilized temperature of 600°C is almost 10 FAU. Hence, thermal stabilization can be applied to reduce the turbidity of SFSs generated from iron foundry industry.

Abstract: Carbon nanomaterials are among the best known and most promising products of the nanotechnology movement. Some early studies suggest that fullerenes and nanotubes may pose significant health risks, and this has given rise to an emerging literature on carbon nanotoxicology. This young field has now begun to yield insight into toxicity mechanisms and the specific material features involved in those mechanisms. This paper explores the potential to alter those material features through post-processing or reformulation with the goal of reducing or eliminating carbon nanomaterial health risks. The paper emphasizes the important roles of metal content and bioavailability, carbon surface chemistry, and nanomaterial aggregation state. The nanotechnology movement has been given a unique "window of opportunity" to systematically investigate the toxicity of nanotechnology products and to develop ways to manage health risks before large scale manufacturing becomes widespread.