In this study, nano grain W is fabricated by Severe Plastic Deformation-Powder Metallurgy (SPD-PM) process. W powder and W-Re powder mixtures are processed by SPD-PM process, a Mechanical Milling (MM) process. As results, a nano grain structure, whose grain size is approximately 20nm, is obtained in W powder after MM for 360ks. A nano grain W compact, whose grain size 630nm, has excellent deformability above 1273K. A nano grain W-10Re compact is composed of equiaxed grain, a grain growth is restrained and has low dislocation density after the large deformation; therefore it is considered that W-Re compact shows superplasticity.

Growth behavior and kinetics of grains in a liquid matrix has been studied by computer simulation for various physical and processing conditions. The kinetics of growing and dissolving grains were considered to follow those of single crystals in a matrix. Depending on the shape of crystals, rounded or faceted, different kinetic equations were adopted for growing grains and an identical equation for dissolving grains. Effects of such critical parameters as step free energy, temperature, and liquid volume fraction were evaluated.

Both densification and grain growth are driven by the reduction of the interfacial area, kinetics of which depends strongly on the interface structure. Abnormal grain coarsening in the system of singular solid/liquid interface such as WC-Co alloys was explained by the growth mechanism of 2-dimensional nucleation. Based on this concept, the marked inhibition of coarsening of WC grains by VC addition can be approached by the increase in the step free energy, which increases the barrier of 2-dimensional nucleation. The activated sintering in tungsten powders can be approached by the interface structure change induced by the addition of a small amount of nickel.

The grain growth behavior of (NBT-5BT) has been investigated with respect to the grain shape. The powder compacts of NBT-5BT were sintered at 1200 for various times. The corresponding equilibrium shape was a round-edged cube with flat {100}-faces. Abnormal grains were not observed in the specimens sintered for 1 to 12 h but abnormal grains appeared when sintered for 24 h. Before the formation of abnormal grains, a valley was observed in the measured grain size distribution of NBT-5BT, showing that the grain size distribution was a combination of two unimodal distributions. The present result suggests that the grain growth in NBT-5BT was governed by the growth of facet planes which would occur via 2-dimansional nucleation and growth

Three point bending tests of single edge notched beam (SENB) specimens were carried out to evaluate the fracture behavior of the fine-grain isotropic nuclear grade graphite, IG-11. To measure the crack initiation point and the subsequent crack growth, the direct current potential drop (DCPD) method and a traveling microscope were used. The effects of test variables like initial crack length, specimen thickness, notch type and loading rate on the measured fracture toughness, KQ, were investigated. Based on the test results, the ranges of the test variables to measure the reliable fracture toughness value were proposed. During the crack growth, the rising R-curve behavior was observed in IG-11 graphite when the superficial crack length measured on the specimen surface was used. The increase of crack growth resistance was discussed in terms of crack bridging, crack meandering, crack branching, microcracking and crack deflection, which increase the surface energy and friction force.

Copper is able to work as a current collector under wide range of hydrocarbon fuels without coking in Solid oxide fuel cells (SOFCs). The application of copper in SOFC is limited due to its low melting point, which result in coarsening the copper particle. This work focuses on the sintering of copper powder with ceria coating layer. Ceria-coated powder was prepared by thermal decomposition of urea in solution, which containing CuO core particles. The ceria-coated powder was characterized by XRD, ICP, and SEM. The thermal stability of the ceria-coated copper in fuel atmosphere was observed by SEM. It was found that the ceria coating layer could effectively hinder the grain growth of the copper particles

The structural and magnetic properties of nanostructued alloy powders were investigated. Commercial alloy powders (Hoeganaes Co., USA) with purities were used to fabricate the nanostructure Fe-Si alloy powders through a high-energy ball milling process. The alloy powders were fabricated at 400 rpm for 50 h, resulting in an average grain size of 16 nm. The nanostructured powder was characterized by fcc and hcp phases and exhibited a minimum coercivity of approximately 50 Oe

본 시험은 국내에서 육성된 사료용 유채의 이용성을 증진시키기 위하여 질소 시비수준과 화본과 사료작물과의 혼파를 통하여 품질 및 생산성에 미치는 영향을 구명하기 위하여 수행되었다 포장시험은 농촌진흥청 작물과학원 호남농업연구소 목포시험장 시험포장에서 수행되었고 혼파된 화본과 사료작물은 호밀, 귀리, 보리 및 이탈리안 라이그라스이었으며 질소시비 수준은 100, 150 및 200kg/ha이었다. 남부지방 봄 이용시 혼파로 인한 건물 함량 증가는 로 큰 효과는