Quartz machining

V.K. Jain, S.K. Chak Electrochemical spark trepanning of alumina and quartz. Machining Science and Technology 4 (2000), pp. 277-290. 

Cleaning Supercritical fluids such as CO9 are being used to clean and degrease quartz rods used to produce optical fibers, produc ts used in the fabrication of printed circuit boards, oily chips from machining operations, and precision bearings in militaiy applications, and so on. Here, CO9 replaces convention chlorocarbon or chlorofluorocarbon solvents. 

Thacker [24] reported the design of a miniature flow fluorimeter for liquid chromatography. The body of the fluorimeter was machined from a block of aluminium and contained a low-pressure mercury lamp, an excitation filter, a quartz flow cell, an emission filter, a photomultiplier tube and a photoconducter in order to compensate for fluctuations in lamp intensity. Fluorescence was examined at a direction perpendicular to that of the excitation light. The cell was small enough for it to be attached directly to the end of the column with a minimum dead volume. 

However, great care must be taken in choosing an appropriate sample holder and a suitable sample geometry.9 Cylindrical capsules machined from high-purity PTFE, enclosed in long polyethylene straws, allow the measurement of compressed polycrystalline samples or even solutions. Polycrystalline samples need to be pulverized so that preferential orientation can be avoided. The sample should be placed into a cylindrically shaped sample holder. Air-sensitive compounds can be sealed in small tubes from synthetic quartz glass. The field- and temperature-dependent contribution of the sample holder must be known precisely. 

All the solutions which are necessary to form an equilateral triangular llxllxll, 61-element ternary phase diagram were prepared automatically by a liquid dispensing machine. Mixtures with compositions of each component ranged from 0 to 100% in 10% increments. On the 3 in quartz wafer used, 144 wells form a 12 x 12 square grid for the catalyst spots. Each of these elements has a diameter of 3 mm. The whole array is calcined at 500 °C for 12 h and subsequently for an additional 12 h at 800 °C under a 6% H2 in argon atmosphere [80],... 

Ultrasonic machining, also known as ultrasonic impact grinding, uses ultra-sonically induced vibration delivered to a tool to create accurate cavities and channels of many shapes [146]. It can be used to form deep cavities as small as 250 pm in diameter (with an accuracy of 50 pm) in both hard and brittle materials such as glass, quartz, polymers, ceramics and metals. This technique may be useful for fabrication of large masters. 

Bare et al. (2006) described two cell designs, one for transmission XAFS and one for fluorescence measurements, whereby all of the critical components could be purchased commercially, with little machining required. The designs are simple, robust, and relatively low in cost. The basis of the designs is a quartz tube with windows fabricated from an appropriate material. The tube is heated by a clamshell furnace. The catalyst powder (with or without diluent) is hand-pressed into a quartz sample holder that is inserted into the quartz tube. Thus, a spectroscopically uniform sample is obtained without the high pressure compaction that is necessary to obtain a self-supporting wafer. The cell has been operated at temperatures from 80 to 1373 K, but the maximum working pressure is only approximately 1 bar. 

Diffusers are made from machined quartz, Teflon, or opal. The type of material is chosen based on the wavelengths of interest. Other applications, like radiance and luminance, call for a narrow field of view so an occluding hood or lensed barrel is used on the photodetector to limit the spatial response to a small, well-defined area. 

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