Diamond-cell technique

Bassett WA (2001) Rev Sci Instrum 72(2) 1270. Workshop on Advances in Laser Heated Diamond Cell Techniques, Chicago, IL, 25-27 May 2000... 

In recent years it has been possible to increase the static pressure during material synthesis and investigations by more than a factor of 50. This means that it is possible to access pressures which were previously unthinkable. This breakthrough was made possible by the huge advances in the diamond-cell technique. The pressure at the centre of the earth corresponds to a value of approximately... 

Figure 3.7 Infrared spectrum of a three layer polymer laminate using the diamond cell technique. Source Author s own files)...

S.C. Palticini and T.J. Porro, Identification of Polymer Laminates Using the Diamond Cell Technique, Perkin Elmer Infrared Bulletin, No.IRP121, Perkin Elmer, Boston, MA, USA. 

The cubic y-modification has been recently observed under a pressure of 15 GPa and temperatures above 2000 K by the laser heating technique in a diamond cell [23] and in shock-wave compression experiments with pressures >33 GPa at 1800 K and >50 GPa at 2400 K [29]. This modification is often designated as the c-modification in the literature in analogy to the cubic boron nitride (c-BN). It has a spinel-type structure in which two silicon atoms are octahedrally coordinated by six nitrogen atoms, one silicon atom is coordinated tetrahedrally by four nitrogen atoms (Fig. 3c). The atomic coordinates for the cubic modification are given in Table 2. From calculations it is shown that this structure should have a high hardness similar to that of diamond and c-BN [23]. 

The melting temperature of a-Si3N4 up to a pressure of 37 GPa was determined by diamond-anvil cell technique [122]. The melting temperature varied from 2200 75 K at 3.5 GPa to 3600 200 K at 37 GPa. The authors did not refer to a phase transition a-Si3N4/c-Si3N4. 

In analytical studies of unknowns, Raman spectroscopy is very useful as a screening method for choosing the best further sophisticated techniques, and for control of the sufficiency and adequacy of received and synthesized information. This is especially important when there are very limited amounts of substances such as linked polymeric complex materials (paints, coatings, adhesives, sealants, etc.) when separation and isolation methods are hardly applicable. Combined investigations using FT-Raman followed by FT-IR diamond-cell microscopy frequently gives adequate results. 

Phase Transitions and Material Synthesis using the C02-Laser Heating Technique in a Diamond Cell... 

LIBS is strongly recommended for elemental analysis of cross-sections as the majority of encrustations and overpaint layers, as well as pigments, contain metals. One of the main advantages of this technique is that extremely small samples can be examined (0.1 nm) compared to traditional methods of analysis by Fourier transform infrared where a few milligrams are needed, even with a diamond cell instrument. No further sample preparation is required as... 

The synthesis of a novel 7-813X4 phase with a cubic spinel structure (see Figure 2.1c) was carried out under high pressure (15 G Pa) and at temperatures above 1920 ° C in a laser-heated diamond cell [22]. Today, many different processing techniques for y-813X4 synthesis are available, the most common being the diamond anvil cell (DAC) synthesis (G. 8erghiou, et al., unpublished results), the multianvil pressure apparatus (MAP) synthesis [23], and the shock synthesis [24]. 

Weingartner, H., Klante, D., and Schneider, G.M. (1999) High-pressure liquid-liquid immis-cibility in aqueous solutions of tetra-n-butylammonium bromide studied by a diamond anvil cell technique, J. Solut. Chem., in press. 

A new technique for the identification of components of polymer laminates is the diamond anvil cell technique supplied by Perkin Elmer [29]. A laminate is separated by cutting a small portion of the sample with a razor blade. The layers are then separated by sectioning each piece with the blade. All sample preparation is performed under a stereo microscope. The separated layers are then individually placed in the diamond cell and a spectrum is obtained. This work was performed using a Perkin Elmer model 1650 instrument (a DTGS detector) at 8 cm resolution and 16 scans. Figure 3.7 shows spectra identifying the components of a three-layer polymer laminate. 

A technique for the identification of components or polymer laminates is the diamond anvil cell technique supplied by Perkin Elmer [59]. A laminate is separated by cutting... 

Diamond cells are about 4 mm in aperture and depending on the area of the spot of the spread sample it is possible to utilize a beam condenser or a microscope. Despite the absorption of diamond in the mid infrared, the wavenumber reproducibility that FT-IR is able to achieve makes it possible to subtract the diamond spectrum and to obtain clean spectra of the sample. In forensic analysis this technique is applied to paints, varnishes, inks, fibres, crystals and particles in general, which can be put under pressure and suffer a deformation. To avoid excess of absorption, one of the cells can be removed. In the case of samples such as cork, tobacco and some polymers, which recover their original size after decompression of the cell, the alternative is to use two diamond windows with the sample in between, instead of removing one of them. 

When paint samples are very small, for example in the case of a valuable painting, or an archaeological sample or the paint which remains attached to a lead bullet once it has passed through the bodywork of a car, the most widely used technique is to put small particles on a diamond cell and to obtain the infrared spectrum by transmission. If the sample cannot be removed from the matrix, microscopy with an attenuated total reflectance objective can be used. 

With the advent of the commercial FT-IR instruments, and computer techniques, it is now possible to record the infrared spectrum of almost any material regardless of its shape or form. A number of different sampling accessories are available for recording the infrared spectra. Some of these accessories such as AIR and specular reflectance have been used successfully with dispersive instruments, but the FT-IR instruments allow these accessories to be used more rapidly and with greater sensitivity. Most of the sample handling techniques have been reviewed in detail in the series of volumes on "Fourier Transform Infrared Spectroscopy" edited by J.R. Ferraro and J.R. Basile (1). In this paper, some of these techniques will be reviewed with particular emphasis on reflectance techniques (ATR and diffuse) and photoacoustic spectroscopy. Further applications such as far-IR, diamond cell, the absorption subtraction methodology can be found in the article by Krishnan and Ferraro (2). 

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