Specific energy optimization in sawing of rocks using Taguchi approah简

This work aims at selecting optimal operating variables to obtain the minimum specific energy （SE） in sawing of rocks. A particular granite was sampled and sawn by a fully automated circular diamond sawblades. The peripheral speed, the traverse speed, the cut depth and the flow rate of cooling fluid were selected as the operating variables. Taguchi approach was adopted as a statistical design of experimental technique for optimization studies. The results were evaluated based on the analysis of variance and signal-to-noise ratio （S/N ratio）. Statistically significant operating variables and their percentage contribution to the process were also determined. Additionally, a statistical model was developed to demonstrate the relationship between SE and operating variables using regression analysis and the model was then verified. It was found that the optimal combination of operating variables for minimum SE is the peripheral speed of 25 m/s, the traverse speed of 70 cm/min, the cut depth of 2 cm and the flow rate of cooling fluid of 100 mL/s. The cut depth and traverse speed were statistically determined as the significant operating variables affecting the SE, respectively. Furthermore, the regression model results reveal that the predictive model has a high applicability for practical applications.     

Direct current bias applied to hot flame diamond deposition produces smooth low friction coatings

As-deposited diamond coatings generally have a high surface roughness which results in a high friction coefficient and extensive wear of the counter material in sliding contact. Therefore several methods for smoothening diamond coatings have been proposed, such as laser polishing, molten metal etching, thermochemical polishing and mechanical polishing. All these methods have some disadvantage e.g. long processing time or high processing temperature. Furthermore, they are all post-deposition treatments i.e. the manufacture of these coatings requires at least two processing steps, deposition and smoothening. With the present method which combines d.c. bias with hot flame diamond deposition, a smooth diamond surface is produced during the actual growth of the film. No post-deposition treatment is necessary. The surface roughness is not dependent on the coating thickness which means that thick coatings with smooth surface can be produced. In fact, the method has a smoothening effect, i.e. rough surfaces can be made smooth. The method is comparable to conventional hot flame deposition of diamond as to growth rate and cost of producing the coatings. The coatings have a nano-crystalline structure and a surface roughness of Ra = 25 nm, and result in a friction coefficient of 0.1 or less in dry sliding and about 0.05 in water-lubricated sliding against cemented carbide. Their wear resistance is virtually the same as that of conventional diamond films.     

圆柱谐振腔式MPCVD装置中氢、氩微波等离子体分布规律的数值模拟

在使用简化的等离子体放电模型的基础上,模拟了圆柱谐振腔式微波等离子体沉积室中,不同金刚石膜生长条件下微波等离子体的分布状态。在模拟中,针对纳米金刚石的生长环境,就纯氩气反应气体中,不同的输入功率、不同气体压力条件下,沉积室中形成的等离子体分布的变化规律进行了模拟,将其与一般氢气气氛下的相应模拟结果相对比。模拟所获得的结果,对微波等离子体方法沉积金刚石膜的操作环境的优化,有着一定的指导意义。     

Processing and properties of CVD diamond for thermal management

One of the many remarkable properties of diamond is its thermal conductivity, about five times that of copper and the highest of all known materials. The high thermal conductivity in combination with the relative ease of diamond film growth by chemical vapor deposition process makes the material suitable for many applications such as thermal management in high power electronic circuits. For thermal managements applications, various processing steps are needed for the diamond films, such as the metallization for reliable solder bonding, metallurgical processes for planarizing of the faceted growth surface and removal of fine-grained diamond regions with poor thermal conductivity. This paper will review the properties and processing of diamond films for thermal management applications.     

XeCl准分子激光精细刻蚀金刚石和玻璃的实验研究

研究了XeCl激光精细刻蚀玻璃、金刚石等材料的能流阈值和单脉冲能流密度、激光脉冲重复频率等激光参数对单脉冲刻蚀深度的影响，并与理论计算结果进行了比较，为XeCl激光在该加工领域的实际应用提供了实验数据和理论依据。     

金刚石薄膜的反应离子刻蚀

反应离子刻蚀是金刚石薄膜图形化的一种有效方法。研究了用Ｏ２及与Ａｒ的混合气体进行金刚石薄膜图形化刻蚀的主要工艺参数（射频功能、工作气压、气体流量、反应气体成分与比例等）对刻蚀速率和刻蚀界面形貌的影响，兼顾刻蚀速率和刻蚀平滑程度等关键因素，建立了金刚石薄膜刻蚀的优化工艺参数，达到了较满意的图形效果。     

Electrical property dependence on thickness and morphology of nanocrystalline diamond thin films

In this study, we investigate the influence of nanocrystalline diamond (NCD) thin film morphology and thickness on their electrical properties. NCD films are grown on p-type Si substrates with varied thicknesses from 250 to 788 nm. Electrical contacts are formed from combination of Ti/Au metal layers (100 nm thick each). The I-V and breakdown field measurements are used to analyze the electrical properties of metal/NCD/Si sandwich structure. In addition, NCD films are analyzed by scanning electron microscopy and Raman spectroscopy for better interpretation of the I-V measurements.     

一种改进的"钻石背"翼设计

针对目前滑翔弹射程短的缺点,提出一种改进的"钻石背"弹翼.通过增大后掠翼的后掠角、前掠翼的前掠角和展弦比来改进钻石背弹翼,分析计算在飞行攻角为0°～8°的使用条件下不同飞行马赫数时的气动特性.在逆风飞行条件下计算飞行弹道,结果表明在12000m高度,270m/s水平速度投弹的条件下,射程达到110km以上.通过对翼张机构的设计,在原理上说明了菱形弹翼张开机构的可行性.     

BGA基板切割过程中唇缘效应的产生及改进措施

采用两种不同结合剂硬度的金刚石刀片切割同一种BGA基板,通过对刀片刃口形貌的变化以及切割断面的分析,探讨了唇缘效应产生的原因.结果表明,在金刚石浓度、粒度及切割工艺等条件相同的情况下,刀片结合剂硬度是造成唇缘效应的最主要因素,并提出了避免唇缘效应产生的改进措施.