NEW DIAMOND GRINDING WHEELS WITH ELECTRICALLY CONDUCTIVE CUTTING EDGES
The application of an electrically conductive diamond material to a new type of grinding wheel whose cutting edges possess electrical conductivity has been tried in this research work. Firstly, electrical discharge machining is applied on a solid surface of an electrically conductive CVD diamond film to create protrusions like cutting edges. Secondly, it is confirmed that the EDMed surface of the diamond material has an ability of stock removing when used in the form of a small lapping wheel. Thirdly, two different types of grinding wheels for micro grinding, i.e. i) a V-shaped profile wheel and ii) a micro mounted wheel, have been manufactured. And it is found that very fine V-shaped grooves can be made on a cemented carbide workpiece by using those wheels with very small wheel wear.
Fabrication and evaluation of monolayer diamond grinding tools by hot filament chemical vapor deposition method
Abstract Monolayer diamond grinding tools are commonly made by electroplating or brazing. However, electroplated tools involve weak grain/matrix adhesion due to a lack of chemical bonds, and brazed diamonds often suffer thermal damage resulting from the high-temperature brazing process. This paper reports a new method to fabricate monolayer diamond grinding tools by chemical vapor deposition (CVD) technique. First, diamond powders at the range of 7–180 μm are chosen as seeds of the abrasive grains. The seeds are randomly distributed on SiC substrates by spraying the suspension containing the seeds toward the substrates in a spin coater machine, or orderly positioned on the substrates by a patterned mask. Then CVD diamond growth is conducted on both the substrates and the seeds simultaneously. As-grown diamond films on the substrates are regarded as bonding layers of the grinding tools, and the original seeds with irregular and crushed morphologies can grow into blocky cube-octahedral grains with smooth surfaces, which are supposed to have enhanced mechanical strength. Raman spectra demonstrate that as-grown diamonds on both the substrates and the seeds are of high quality and low levels of graphitization. Besides, relatively low residual stresses are detected in the diamond grains, because both the bonding layers and the grains are made of diamond. Grinding tests are conducted using as-fabricated CVD diamond grinding tools and electroplated/brazed diamond grinding tools as comparisons. The results suggest that the CVD diamond grinding tools possess the best wear resistance in terms of the fracture of the diamond grains. This is attributed to the epitaxial grain structure that restrains the crack propagations. In addition, the wear of the CVD diamond grains can generate tiny pyramidal crystalline tips and sharp edges, indicating the unique shelf-sharpness during the grinding.
Recovering the frontier state : war, ethnicity, and state in Afghanistan
Chapter 1 Table of Contents Chapter 2 1 Introduction Chapter 3 2 Ethnicity, Political Power, and Fragmentation Chapter 4 3 Rise of the Taliban and Civil War Chapter 5 4 The United States and War on Terrorism Chapter 6 5 Restructuring the Afghan State Chapter 7 6 Political Economy of Drugs and Warlordism Chapter 8 7 Afghanistan and Neighboring States Chapter 9 8 Conclusion Chapter 10 Bibliography