We report the structural, morphological and magnetic properties of the Ni70Mn30 alloy prepared by Planetary Ball Mill method. Keeping the milling time constant for 30 h, the effect of different ball milling speeds on the synthesis and magnetic properties of the samples was thoroughly investigated. A remarkable variation in the morphology and average particle size was observed with the increase in milling speed. For the samples ball milled at 200 and 300 rpm, the average particle size and hence magnetization were decreased due to the increased lattice strain, distortion and surface effects which became prominent due to the increase in the thickness of the outer magnetically dead layer. For the samples ball milled at 400, 500 and 600 rpm however, the average particle size and hence magnetization were increased. This increased magnetization was attributed to the reduced surface area to volume ratio that ultimately led to the enhanced ferromagnetic interactions. The maximum saturation magnetization (75 emu/g at 1 T applied field) observed for the sample ball milled at 600 rpm and the low value of coercivity makes this material useful as soft magnetic material.

이 연구의 목적은 골프드라이버 샤프트의 가변성이 타구속도, 헤드스피드 및 비거리에 미치는 영향을 분석하고자 하였다. 이 연구에 참여한 피검자는 핸디캡이 0인 남자 프로골퍼 10명과 핸디캡이 18인 남자 아마추어 골퍼 10명으로 하였다. 클럽의 종류는 1번 드라이버로 한정하였고, 각기 다른 스팩의 24개 드라이버를 가지고 실시하였다. 종속변인으로는 타구속도, 비거리 및 헤드스피드로 하였다. 연구 결과 다음과 같은 결과를 얻었다. 첫째, CPM에 따라 유의한 차이가 나는 것으로 밝혀졌고, 사후검증 후 230< 이상일 때 타구속도, 비거리 및 헤드스피드에서 최적의 수행력을 보였다. 둘째, 샤프트길이에 따른 타구속도 및 비거리는 유의한 차이가 나는 것으로 나타났고, 사후검증 후 타구속도 및 헤드스피드는 46inch에서 비거리는 45inch에서 최적의 수행력을 보였다. 셋째, 샤프트 무게에 따른 변인 간 차이는 나지 않았고, 사후검증 후 샤프트 무게가 65g일 때 타구속도와 비거리에서 최적의 수행력을 보였고, 50g일 때 헤드스피드에서 최적을 보였다. 또한 프로와 아마추어 간에는 변인에서 유의한 차이가 나는 것으로 나타났다. 결론적으로 최적의 드라이버는 CPM이 230<, 샤프트길이 46inch, 샤프트 무게가 65g 샤프트 일 때 최고의 수행력을 발휘하는 것으로 판명되었다.

The study of grinding behavior characteristics on aluminum powders and carbon nano tubes (CNTs) has recently gained scientific interest due to their useful effect in enhancing advanced nano materials and components, which significantly improves the property of new mechatronics integrated materials and components. We performed a series of dry grinding experiments using a planetary ball mill to systematically investigate the grinding behavior during Al/CNTs nano composite fabrication. This study focused on a comparative study of the various experimental conditions at several variations of rotation speeds, grinding time and with and without CNTs. The results were monitored for the particle size distribution, median diameter, crystal structure from XRD pattern and particle morphology at a given grinding time. It was observed that pure aluminum powders agglomerated with low rotation speed and completely enhanced powder agglomeration. However, Al/CNTs composites were achieved at maximum experiment conditions (350 rpm, 60 min.) of this study by a mechanical alloy process for Al/CNTs mixed powders because the grinding behavior of Al/CNTs composite powder was affected by addition of CNTs. Indeed, the powder morphology and crystal size of the composite powders changed more by an increase of grinding time and rotation speed.

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.