X-ray diffraction instrumentation

Arii, T. Kishi, A. Kobayashi, Y. Coupled DSC and x-ray diffraction instrument. TTiennochim. Acta 1999, 325, 151-156, Rigaku Application Note Presented at the 48th Annual Denver X-ray Conference, 1999. 

XRD. X-Ray diffraction analyses were carried out on catalysts by a Philips X-ray diffraction instrument using a PW 1310/01/01 generator and Cu Ka radiation. 

In the laboratory you may be exposed to instruments that generate radiation (such as X-ray diffraction instruments) or may have sealed sources that contain hazardous levels of radioactive materials (such as Y irradiators or analytical detectors). You may also be exposed to unsealed, open sources of radiation. Both types require special training and education to learn proper procedures and handling precautions about these radiation hazards. We discuss first how to protect yourself from sources of radiation in laboratory instrumentation. 

Over the past 15 years, significant advances in X-ray diffraction instrumentation have completely transformed how chemists make use of this technique. This is particularly evident in the field of supramolecular chemistry, where characterizing the structural motifs of molecular crystals is crucial to the understanding of the weak intermolecu-lar forces that are responsible for crystal stability. This chapter will describe advances that are typical of instrumentation available in most chemistry departments as well as the advances in data treatment, structure solution, and refinement that have become possible. Other more specialized diffraction methods, for example, using synchrotron radiation and neutrons, will be mentioned, but detailed... 

Present day techniques for structure determination in carbohydrate chemistry are sub stantially the same as those for any other type of compound The full range of modern instrumental methods including mass spectrometry and infrared and nuclear magnetic resonance spectroscopy is brought to bear on the problem If the unknown substance is crystalline X ray diffraction can provide precise structural information that m the best cases IS equivalent to taking a three dimensional photograph of the molecule... 

Instrumental Methods for Bulk Samples. With bulk fiber samples, or samples of materials containing significant amounts of asbestos fibers, a number of other instmmental analytical methods can be used for the identification of asbestos fibers. In principle, any instmmental method that enables the elemental characterization of minerals can be used to identify a particular type of asbestos fiber. Among such methods, x-ray fluorescence (xrf) and x-ray photo-electron spectroscopy (xps) offer convenient identification methods, usually from the ratio of the various metal cations to the siUcon content. The x-ray diffraction technique (xrd) also offers a powerfiil means of identifying the various types of asbestos fibers, as well as the nature of other minerals associated with the fibers (9). 

Surface areas were determined from the adsorption isotherms of nitrogen at 77 K, using a Micromeritics ASAP 200 instrument. Powder X-ray diffraction patterns were obtained with a CGR theta 60 instrument using CuKa monochromated radiation. Reducibility and the amount of Cu species were determined by temperature programmed reduction (TPR) with H2 (H2/Ar 3/97, vol/vol). The experimental set up has been described previously [6]. 

Some properties of the rock used in this study were measured The cation exchange capacity (cec) was determined by the barium sulfate method as described by Mortland and Mellor (33). Surface area was measured by using a Digisorb Meter (Micromeritics Instrument Corporation) through nitrogen adsorption. Estimation of mineral composition and indentification of the rock were performed by X-ray diffraction. 

Nitrogen adsorption was performed at -196 °C in a Micromeritics ASAP 2010 volumetric instrument. The samples were outgassed at 80 °C prior to the adsorption measurement until a 3.10 3 Torr static vacuum was reached. The surface area was calculated by the Brunauer-Emmett-Teller (BET) method. Micropore volume and external surface area were evaluated by the alpha-S method using a standard isotherm measured on Aerosil 200 fumed silica [8]. Powder X-ray diffraction (XRD) patterns of samples dried at 80 °C were collected at room temperature on a Broker AXS D-8 diffractometer with Cu Ka radiation. Thermogravimetric analysis was carried out in air flow with heating rate 10 °C min"1 up to 900 °C in a Netzsch TG 209 C thermal balance. SEM micrographs were recorded on a Hitachi S4500 microscope. 

---