Materials Science Forum Vols. 510-511

Abstract: A new iron-based wear resistance alloy was developed to replace the Co-containing Stellite 6 alloys in nuclear power industry. The effect of B addition on the wear resistance was investigated. Sliding wear tests of Fe-Cr-C-Si-xB (x = 0.0, 0.3, 0.6, 1.0 and 2.0 wt%) alloys were performed in air at the room temperature under a contact stress of 103 MPa. Low-boron alloys containing less than 0.6 wt% boron showed an excellent wear resistance than any other tested alloys. The improvement was associated with the matrix hardening by promotion of the γ→α′straininduced martensitic transformation occurring during the wear test. However, the alloys containing more than 1.0 wt% boron showed slightly increased wear loss compared to the low-boron alloys because of the absence of the strain-induced martensitic transformation and the presence of the brittle FeB particles, aiding crack initiation.

Abstract: Wear damage of steam generator tubes for nuclear power plants can cause the leakage of radioactive substances. Therefore, the evaluation of integrity and safety for tubes is very important from the viewpoint of nuclear ecocide. In the present study, to investigate the wear properties of Inconel 600 and 690 steam generator tube materials mated with 409 stainless steel commonly used as support plate, sliding wear tests were performed with increasing sliding distance in air and in elevated temperature water environment, respectively. The wear volume of tube materials was less than those of supports under all conditions. There were no significant differences in the wear behavior for the Inconel 600 and 690 tubes, independently of the testing environment.

Abstract: A new process, melts dispersion technique, was developed to fabricate the solder powder in oil surroundings by forming molten metal’s droplets. The main parameters of the technique on shape and size of powders were investigated in the present paper. It is shown that a cooling rate of the melts and viscosity of oil for isolation of droplets affect the shape and the size. The cooling rate is a very important parameter, and there is a critical cooling rate at given conditions. Although the melts were dispersed perfectly in oil, fine droplets were merged and coalesced during solidification without rapid cooling. The shape of powder has an influence mainly on oil viscosity and was altered into a sphere from an irregular shape with increasing oil viscosity.

Abstract: We present the preliminary results of our research on the behavior of lead free glasses in the acid etching process, which is used for the formation of barrier ribs in plasma display panel. The glasses (BaO-B2O3-ZnO system) were etched in HNO3 solution (0.1-1.0% HNO3) at 50°C. The structure and surface of the etched bulk glass were investigated by using inductively coupled plasma and X-ray photoelectron spectroscopy. As a result, Ba (3-35ppm/min) and Zn (2- 27ppm/min) ions as major components were leached in the solution. A decrease of the bridge oxygen and a relative increase of non bridge oxygen in the etched glass were found by X-ray photoelectron spectroscopy.

Abstract: Oxide glasses having lower glass transition temperature are widely used in electric devices. The oxide glasses usually contain lead oxide. Recently, lead oxide glasses have been replaced with lead-free oxide glasses because of the environmental pollution. We investigated the thermal properties and the glass formation region in the Bi2O3-B2O3-ZnO ternary system. The results showed that the ratio of Tg/Tl of the bismate glasses is around 0.55, which is lower than the value of ratio 0.67, the two-third rule (Tg/ Tl=2/3)

Abstract: We investigated the mechanism of chemical reaction between Bi2O3 glass and water solution during milling. As a result, the frit condition affected discoloration with crystallization. After milling, there was a deposited layer on the frit surface. The layer was composed of leached ions, contaminates of metal oxides, and hydroxides. Bismate glass frit is reacted to the milling solution so that the frit surface is formed with a gel layer. In milling, contaminates contained in milling solution is contributed to the formation of deposed layer on frit surface.

Abstract: The integrated system of microfiltration and electrodialysis was proposed for wastewater reclamation, and the treatment performances were experimentally investigated with a pilot-scale system. The filterability of membrane and the long-term operational performances of the system were focused with real municipal sewage. The suggested wastewater reclamation system shows stable water quality during operational period over 6 months. Therefore, it is believed to be a useful system for reuse of wastewater and security of water resources.

Abstract: The objective of this study is to prepare a pelletized adsorbent to remove volatile organic compounds (VOC) from the municipal solid waste incinerator (MSWI) fly ash in Korea. The fly ash sample was sieved to particle size of 75-150㎛, and then a hydrothermal processing was carried out. The pelletized adsorbent was prepared from hydrothermal treated fly ash by mixing it with coal tar pitch and K2CO3 as a carbon source and activating agent, and activating them. The optimum condition to derive maximum iodine adsorptivity and BET surface area was the mixing ratio of hydrothermal treated fly ash, coal tar pitch and K2CO3 of 40/40/20 wt.% at the activation temperature of 800°C. Under this condition, the iodine adsorptivity and BET surface area for prepared adsorbent were 455 mg/g and 325 m2/g, respectively.

Abstract: Waste sludges produced from the recycling of concretes contain a large amount of aggregate powders and pre-reacted cements so that they have no more cementing properties. However, since they contain unreacted Ca(OH)2, pozzolanics such as blast slag or meta kaoline can activate the waste concrete, and they can be reused as low-grade cement or pozzolanics. When meta kaoline was added with some other pozzolanic materials such as gypsum or blast slags, the density was increased so that the compressive strength, especially early stage of curing time, was enhanced. When meta kaolin was added, more densified C-S-H gel networks were formed at aggregates, and ettringites were produced between the C-S-H gel networks.