Multiple film technique

The relative positions of the lines on the photographs were determined with use of a steel millimeter scale. The intensities of the lines on the NaZn13 photographs were determined visually, by the multiple-film technique, with the use of no external standards. 

Powder photographs were taken with a 57.3-mm radius Debye-Scherrer camera and nickel-filtered Cu Ka radiation (Xmean = 1.5418 A). For intensity work, the multiple-film technique was used. The lattice constant, derived from 23 reflections from 42.56° to 73.47° 20 and corrected for film shrinkage with a parallel film of a reference substance, was Oo = 15.02 A with an estimated standard deviation of 0.01 A. 

In the last few years rapid advances have been made in the field of computational crystallography, so that it is now possible to produce highly refined computer models of a wide variety of polymeric materials using X-ray diffraction data. Unfortunately, these achievements have been negated to some extent because the techniques used to collect the data for such refinement programs have not advanced at a comparable rate. In this contribution we describe a computer program which facilitates the reduction of intensity and d-spacing data obtained by the multiple film-pack method, and attempts to quantify the errors associated with such measurements. 

One quality control application of near-IR spectroscopy is the nondestructive determination of tablet hardness. Near-IR prediction of tablet hardness has been used and investigated by Drennen for a number of years. In 1991, the first publication of the near-IR technique for this application appeared [26]. Ciurczak and Drennen published similar results in 1992 [60] and Drennen and Lodder in 1993 [61]. Results of a study presented at the 1994 annual meeting of the American Association of Pharmaceutical Scientists were published in a 1995 paper [62]. In that paper, Kirsch and Drennen identified the utility of the technique in the determination of multiple film-coated tablet properties, including tablet hardness. In a review paper regarding the use of near-IR in the analysis of solid dosage forms, Kirsch and Drennen discussed the historical aspects of near-IR prediction of tablet hardness [27]. 

A cost reduction area that could have significant opportunities for chemicals companies is the interest in cheaper track generation systems such as screen printed conductive inks and the conductive pastes that are being used to replace plated through holes (PTH). Copper-based inks are already being used to form crossovers and simple circuits, and the use of thick film techniques of multiple layer printing is being evaluated to replace some multilayer circuits. 

Radoslovich tried to answer these problems using a crystal structure refinement technique involving X-ray diffraction intensity data collected by the multiple-film Weissenberg method. His refinement involved a modest use of an electronic computer with two-dimensional Fourier syntheses using intensity data transferred to perforated tape... 

Mirrors are also made using multiple dielectric layers of thickness A/4. The more layers that are added, the better the reflectivity that can be achieved in a certain wavelength region. In Fig.6.40 the effect of an increase in the number of layers is demonstrated. A reflectivity better than 0.999 can be obtained using 30 layers. Clearly, thin-film techniques of this kind are of great importance for the construction of laser cavities and for interferometers with sharp frequency discrimination characteristics. 

Alloy films may he deposited using multiple sources with individual deposition rate controllers. In this case the vapor flux distribution from each source must he taken into account. The multiple source technique can also be used to deposit layered composite films. Multiple sources with overlapping flux distributions can be used to form films having a range of compositions over the substrate surface. 

In conventional tenter orientation, the sequence of steps is as described above (MD—TD). In some cases it is advantageous to reverse the draw order (TD—MD) or to use multiple draw steps, eg, MD—TD—MD. These other techniques are used to produce "tensilized" films, where the MD tensile properties are enhanced by further stretching. The films are generally unbalanced in properties and in extreme cases may be fibrillated to give fiber-like elements for special textile appHcations. Tensilized poly(ethylene terephthalate) is a common substrate for audio and video magnetic tape and thermal transfer tape. 

Latexes of synthetic resins are identified by ir spectrometry. Selective extraction with organic solvents is used to obtain purified fractions of the polymers for spectrometric identification. Polymeric films can be identified by the multiple internal reflectance ir technique, if the film is smooth enough to permit intimate contact with the reflectance plate. TAPPI and ASTM procedures have not been written for these instmmental methods, because the interpretation of spectra is not amenable to standardization. 

The principle application of XRF thin-film analysis is in the simultaneous determination of composition and thickness. The technique has been used for the routine analysis of single-layer films since 1977 and multiple-layer films since 1986. Two main sources of publications in the fields are the annual volumes of Advances in X-Ray Analysis by Plenum Press, New York, and the Journal of X-Ray Spectrometry by Heyden and Sons, London. Typical examples on the analysis of single-layer films and multiple-layer films are used to illustrate the capabilities of the technique. 

If a sample of polycrystalline material is rotated during the sputtering process, the individual grains will be sputtered from multiple directions and nonuniform removal of material can be prevented. This technique has been successfully used in AES analysis to characterize several materials, including metal films. Figure 9 indicates the improvement in depth resolution obtained in an AES profile of five cycles of nickel and chromium layers on silicon. Each layer is about 50 nm thick, except for a thinner nickel layer at the surface, and the total structure thickness is about 0.5 pm. There can be a problem if the surface is rough and the analysis area is small (less than 0.1-pm diameter), as is typical for AES. In this case the area of interest can rotate on and off of a specific feature and the profile will be jagged. 

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