ΓΛΩΣΣΑΡΙΟ - ΕΥΡΕΤΗΡΙΟ ΑΚΡΩΝΥΜΙΩΝ & ΤΕΧΝΙΚΩΝ ΟΡΩΝ

X-ray crystallography

Ιt is a method used for determining the atomic and molecular structure of a crystal, in which the crystalline atoms cause a beam of X-rays to diffract into many specific directions. By measuring the angles and intensities of these diffracted beams, a crystallographer can produce a three-dimensional picture of the density of electrons within the crystal. From this electron density, the mean positions of the atoms in the crystal can be determined, as well as their chemical bonds, their disorder and various other information.

XRD: X-ray diffraction

A technique for the semi quantitative mineralogical analysis of a sample of rock by measuring the diffraction peaks in X-rays diffracted by the sample. The position of the diffraction peaks is a measure of the distance between discrete crystallographic diffracting planes within minerals, while their intensity indicates the quantity of the mineral. The technique is only semi quantitative because the size and shape of the diffraction peak are strongly influenced by the geometry of the measurement, for example orientation of the minerals, and sample preparation. Fine particles such as clays must be separated from larger particles and measured separately if they are to be detected properly. To reduce errors associated with preferred orientation of minerals, samples are most commonly ground to a powder before analysis, a technique known as powder X-ray diffraction.

XRF: X-ray fluorescence

X-ray fluorescence: Ιt is the emission of characteristic "secondary" (or fluorescent) X-rays from a material that has been excited by bombarding with high-energy X-rays or gamma rays. The phenomenon is widely used for elemental analysis and chemical analysis, particularly in the investigation of metals, glass, ceramics and building materials, and for research in geochemistry, forensic science and archaeology.

Xylene

An aromatic hydrocarbon molecule containing a benzene ring with two methyl side chains, formula C6H4(CH3)2. Xylene is an excellent solvent, especially for aromatic solids such as asphaltic materials. It is used as a solvent and emulsion breaker in workover operations to clean up reservoirs. In drilling mud testing, a 50/50 xylene/isopropanol (IPA) mixture had been used to break oil-mud emulsions prior to titrations to measure alkalinity, chloride and calcium. However, the xylene mixture has been replaced by a single material, propylene glycol normal propyl ether (PNP), to break oil mud emulsions.

 
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