Three mixtures of elemental powders of Al-25at.%Ti, 48at.%Ti and 70at.%Ti were offered to ball milling process for the formation of intermetallic compounds of , AlTi and . Ballmilling or attrition process were carried out at the condition of rotaing speed of 110 or 350 rpm at torr vacuum or argon atmospheres. phases were fully obtained by heat treatment for 1 hors at with Al-25at.%Ti composition mixtures milled by 100 hours. The amorphous phase was completely formed at the composition of Al-48at.%Ti mixed powders by milling 100hours at the 50 to 1 weight ratio of ball to powder, and AlTi compounds were obtained by heat treament. In the case of Al-70at%Ti mixed powders milled for 100 hours, and intermetallic compounds were formed by heat treatment for 1 hour at . By attrition milling of 350rpm for 10 hours, phase was formed completley after heat treatment for 1 hour at .

본 연구는 티타늄과 활성탄소 원료분말을 반응밀링법에 의해 합성시, 밀링시간에 따른 Ti-TiC 복합재료의 미세조직과 기계적 성질에 미치는 TiC vol.% 및 열간압축성형온도의 영향에 관해 조사하였다. 티타늄과 활성 탄소 원료분말을 300시간 밀링 후 5μm이하의 미세한 구형의 Ti-TiC복합분말을 생성시킬 수 있었다. 반응밀링된 분말을 1000˚C이상에서 1시간동안 진공열간압축성형한 경우 이론밀도의 98%에 가까운 우수한 성형체를 얻었으며, TiC입자가 티타늄 기지 전반에 걸쳐 고르게 분산되어 Ti-TiC 복합재료의 기계적 특성을 향상시켰다. Ti-TiC복합재료의 고온안정성을 고찰하기 위해 600˚C등온열처리한 결과 80시간까지는 경도의 큰 변화없이 열적으로 안정하였다. Ti-20vol%TiC 복합재료를 700˚C에서 고온압축시험을 한 경우 330MPa의 높은 항복강도값을 나타내었다.

Milling media of steel and partially stabilized zirconia(PSZ) were used to produce Si by mechanical alloying(MA) of Mo-25.0at%Si elemental powder mixture. The effect of milling medium materials on MA of the powder mixture have been investigated by XRD and DTA. The reaction rate and the end-product noticeably depended upon the milling medium material. The formation of Si and phases by PSZ ball-milling took place after 15 hr of MA and was characterized by a slow reaction rate as Mo, Si, and Si coexisted for a long period of milling time. The formation of a new phase by steel ball-milling, however, did not take Place even after 96 hr of MA. DTA and annealing results showed that and Si were formed after heating the ball-milled powder specimens to different temperatures. At low temperatures, Mo and Si were transformed into . At high temperatures, the formation of Si can be partially attributed to the reaction, 7Mo+Si+-.4Si . The formation of Si and Mo5Si3 phases by mechanical alloying of the powder mixture and the relevant reaction rate appeared to depend upon the milling medium material as well as the thermodynamic properties of the end-products.

Milling media of steel and zirconia were used to produce by mechanical alloying (MA) of Mo and Si powders. The effect of milling media on MA of Mo-65.8at%Si powder mixture has been investigated by SEM, XRD, DTh and in-situ thermal analysis. The powders mechanically alloyed by milling medium of steel for 8 hours showed the structure of fine mixture of Mo and Si, and those mechanically alloyed by milling medium of zirconia for longer milling time showed the structure of fine mixture of Mo and Si. The tetragonal - Phase and the tetragonal phase appeared with small Mo peaks in the powders milled by milling medium of steel for 4 and 8 hours. The - phase and the hexagonal - phase were formed after longer milling time. The - phase appeared with large Mo peaks in the powders milled by milling medium of zirconia for 4 hours. The phases, - and -. were formed in the powders milled for longer milling time. DTA and annealing results showed that Mo and Si were transformed into - and , while - into -. In-situ thermal analysis results demonstrated that there were a sudden temperature rise at 212 min and a gradual increase in temperature in case of milling media of steel and zirconia, respectively. The results indicate that MA can be influenced by materials of milling medium which can give either impact energy on powders or thermal energy accumulated in vial.

은 튜브에 장입되기 전의 초기 분말의 입자 크기가 Ag/Bi-2223초전도 선재의 미세구조와 상전이, 임계 전류 밀도등에 미치는 영향에 대해 고찰하였다. 분말의 입자 크기는 하소 분말을 볼밀을 이용하여 0-48 시간 동안 분쇄하여 조절하였다. 열처리 후 최종 초전도 선재의 전기적 성질은 초기 분말의 입자 크기에 영향을 받는 것으로 나타났으며 분말의 분쇄에 의한 반응성의 증가에 의해 열처리시 2223 상으로의 상전이가 빠르게 일어났고 이차상의 크기와 분율이 감소된 미세구조를 얻을 수 있었다. 그러나 과다한 분쇄에 의한 반응성의 증가에 의해 열처리시 2223상으로의 상전이가 빠르게 일어났고 이차상의 크기와 분율이 감소된 미세구조를 얻을 수 있었다. 그러나 과다한 분쇄는 분말의 비정질화를 유발하여 2223 상으로의 전이를 방해함으로써 선재의 임계 전류 밀도를 감소시키는 결과를 나타내었다.

The main objectives of this studies are to present the most desirable rice processing complex model system in a given our situations by comparision and analyzing the major factors and, also recommend the future prospect of the rice processing complex in Korea. There are 3 different rice processing complex models in Korea. Those are concrete bin, flat type steel bin and square bin. These systems have a lot of differences and have their own characteristics such as capital requirement, efficiency, storage capacity and quality controls. The major problems of the existing rice processing centers in Korea are high fixed cost and the unbalnced systems. Following is summary to solve this problems: 1. Development of the large scale harvester and high speed continuous dryer. 2. Quality inspective system of bulk grain and large scale temporary storage facilities. 3. Large size readjustment of arable land. 4. Select the convenient location of rice processing center and formulation of well equipment facilities.

Cobalt and VC powders were ball milled with M2 grade high speed steel powders under various ball to powder ratios. The powders milled under higher ball to powder ratio become finer, more irregular and have a broader size distribution, and thus possess a lower compressibility and a better sinterability regarding densification. Increasing the ball to powder ratio lowered the sintering temperature to obtain the density level necessary to isolate all the pores. Lowering the sintering temperature is very critical to maintain fine microstructure since grain and carbide coarsening are accelerated by higher sintering temperature due to more liquid phase formation. The powders obtained by ball milling at 20 to 1 ratio has the lowest compressibility but has the best sinterability, almost compatible to unmilled pure M2 powders. A sintered body over 97% theoretical density with fine microstructures having average grain size of ~10 microns was obtained from the powder by sintering at 1260 for 1 hour in vacuum. XRD results indicate that two types of carbides are mainly present in the sintered structure, MC and type. The MC type carbides are more or less round shaped and mainly located at the grain boundaries whereas the type are angular shaped and mainly located inside the grains.

A series of test were undertaken in order to estabilish the effect of different milling variables on dimension and quality of aluminium flake powder. Milling conditions such as initial powder size, milling container rotation speed, milling time, and ball size were varied to produce aluminium flake powder. Flake powder could then be obtained with size range from 15 m to 40 m with a maximum specific surface area of 5 /g by controlling milling conditions. Diameter of milled powders with different milling container rotation speed and ball size were compared with that obtained from theoretical model. The best flake powder was obtained in milling condition of initial powder with average size of 19 m, mill container rotation speed of 80 rpm, balls of 9.5 mm diameter, and milling time of 40 hours.