Optical analysis, thermal

Thermoptometry is defined as a family of thermoanalytical techniques in which an optical property of the sample is monitored against time or temperature, while the temperature of the sample, in a specified atmosphere, is programmed. Two established examples are thermomicroscopy (observation under a microscope) and thermoluminescence (1). Thermomicroscopy is also referred to as thermal microscopy, optical thermal analysis, hot-stage microscopy (HSM), or fusion methods. 

Polypropylene molecules repeatedly fold upon themselves to form lamellae, the sizes of which ate a function of the crystallisa tion conditions. Higher degrees of order are obtained upon formation of crystalline aggregates, or spheruHtes. The presence of a central crystallisation nucleus from which the lamellae radiate is clearly evident in these stmctures. Observations using cross-polarized light illustrates the characteristic Maltese cross model (Fig. 2b). The optical and mechanical properties ate a function of the size and number of spheruHtes and can be modified by nucleating agents. Crystallinity can also be inferred from thermal analysis (28) and density measurements (29). 

The hydrated alumina minerals usually occur in ooUtic stmctures (small spherical to eUipsoidal bodies the size of BB shot, about 2 mm in diameter) and also in larger and smaller stmctures. They impart harshness and resist fusion or fuse with difficulty in sodium carbonate, and may be suspected if the raw clay analyzes at more than 40% AI2O2. Optical properties are radically different from those of common clay minerals, and x-ray diffraction patterns and differential thermal analysis curves are distinctive. 

When solids react, we would like to know at what temperature the solid state reaction takes place. If the solid decomposes to a different composition, or phase, we would like to have this knowledge so that we can predict and use that knowledge In preparation of desired materials. Sometimes, intermediate compounds form before the final phase. In this chapter, we will detail some of the measurements used to characterize the solid state and methods used to foUow solid state reactions. This will consist of various types of thermal analysis (TA), including differentlEd thermal analysis (DTA), thermogravimetric analysis (TGA) and measurements of optical properties. 

An apparatus for measuring the dynamic modulus and hysteresis of elastomers. The stress-strain oscillogram is shown on a ground-glass screen by means of an optical system. Now superseded by modem computer controlled servo hydraulic and dynamic mechanical thermal analysis machines. Roll Bending... 

The use of solid state NMR for the investigation of polymorphism is easily understood based on the following model. If a compound exists in two, true polymorphic forms, labeled as A and B, each crystalline form is conformationally different. This means for instance, that a carbon nucleus in form A may be situated in a slightly different molecular geometry compared with the same carbon nucleus in form B. Although the connectivity of the carbon nucleus is the same in each form, the local environment may be different. Since the local environment may be different, this leads to a different chemical shift interaction for each carbon, and ultimately, a different isotropic chemical shift for the same carbon atom in the two different polymorphic forms. If one is able to obtain pure material for the two forms, analysis and spectral assignment of the solid state NMR spectra of the two forms can lead to the origin of the conformational differences in the two polymorphs. Solid state NMR is thus an important tool in conjunction with thermal analysis, optical microscopy, infrared (IR) spectroscopy, and powder... 

Luck, W.A.P. 1981. Structures of water in aqueous systems. In Water Activity Influences on Food Quality (L.B. Rockland and G.F. Stewart, eds), pp. 407 134. Academic Press, New York. Ludescher, R.D., Shah, N.K., McCaul, C.P., and Simon, K.V. 2001. Beyond Tg Optical luminescence measurements of molecular mobility in amorphous solid foods. Food Hydro colloids 15, 331-339. Ludwig, R. 2001. Water From cluster to the bulk. Angewandte Chem. Int. Ed. 40, 1808-1827. Maclnnes, W.M. 1993. Dynamic mechanical thermal analysis of sucrose solutions. In The Glassy State in Foods (J.M.V. Blanshard and PJ. Lillford, eds), pp. 223-248. Nottingham Univ. Press, Loughborough, Leicestershire. 

Infrared spectra, of fats and oils, 10 823 Infrared spectral region, 19 564 Infrared spectroscopy, 14 224-243 23 136-143. See also Chromatography-infrared spectroscopy Far- infrared spectroscopy ir-selective surfaces Ir (infrared) spectroscopy Near- infrared spectroscopy Thermal analysis-infrared spectroscopy applications of, 14 239-240 23 140-141 in composition measurements, 20 682 in fiber optic fabrication, 11 138 industrial applications of, 14 240 instrumentation in, 14 225-228 23 137-138... 

The analysis can be made in situ using an optical, thermal, electrical or other method. The average time, during which the reaction proceeds before an element of volume and reaches a distance d along the reaction tube, is d/v, where v is the linear velocity. From the measurements made at various... 

Plots of melting point against optical purity are commonly referred to as phase-composition diagrams. The direct proportionality of melting point with heat of fusion has also been employed to construct similar plots based on thermal analysis data. The classification of racemic modifications into three different types with regard to their crystal packing (32) can be made based on the overall shape of these plots as follows ... 

During investigations we were analyzing samples by methods of X-ray diffraction, electron scanning microscopy, microprobe analysis, atomic force microscopy, high-resolution transmission electron microscopy with preliminary attracting of the another methods including optical microscopy, Raman spectroscopy, thermal analysis and some of others. 

Since that discovery a major aspect of our research effort has been to develop a method to account for this unwanted pyrolytic conversion of organic to elemental carbon. This report describes a combined thermal-optical instrument in which the reflectance of the filter sample is continuously monitored during the thermal analysis. Dod (14) have also reported a combustion... 

Extraction and Thermal-Optical Carbon Analysis Methods Application to Diesel Vehicle Exhaust Aerosol, Environ. Sci. Tech-noi, 18, 231-234 (1984). 

The apparatus used are mostly stirred-tank-, tubular-, and differential recycle reactors. Also, optical cells are used for spectroscopic measurements, and differential thermal-analysis apparatus and stopped flow devices are applied at high pressures. 

I have lost no sleep in debating what is physical - if popular opinion treats tests as part of the physical spectrum (e.g. ageing tests) then they are physical. Not surprisingly, chemical analysis is excluded but it can be noted that the thermal analysis techniques straddle both camps and they have been included or excluded depending on their purpose. The intention has been to include every type of physical test and, hopefully, this has been, in the main, achieved. However, three areas immediately come to mind which do not have their own section, acoustic properties, optical properties and nondestructive testing. 

Preliminary investigations of the liquid crystal phase behavior of these gold nanoparticles initially revealed an enantiotropic nematic phase (based on polarized light optical microscopy and thermal analysis) as well as some pattern formation of the gold nanoparticles in TEM experiments [540, 541],... 

Physical characteristics of active API (aspect, thermal analysis, particle size distribution, optical activity, polymorphic forms, moisture content, loss on drying, microbial content, etc.)... 

Asbestos can be determined by several analytical techniques, including optical microscopy, electron microscopy, X-ray diffraction (XRD), light scattering, laser microprobe mass analysis, and thermal analysis. It can also be characterized by chemical analysis of metals by atomic absorption, X-ray fluorescence, or neutron activation techniques. Electron microscopy methods are, however, commonly applied for the analysis of asbestos in environmental matrices. 

Caslavsky, J. L. (1988). Principles of the optical differential thermal analysis (ODTA). Thermochim. Acta 134,371-376. 

Berger, R., Gerber, C., Gimzewski, J.K., Nanometers, picowatts, femtojoules thermal analysis and optical spectroscopy using micromechanics. Micro Total Analysis Systems 96, Proceedings of 2nd International Symposium on flTAS, Basel, 19-22 Nov. 1996, 74-77. 

Spectroscopy has become a powerful tool for the determination of polymer structures. The major part of the book is devoted to techniques that are the most frequently used for analysis of rubbery materials, i.e., various methods of nuclear magnetic resonance (NMR) and optical spectroscopy. One chapter is devoted to (multi) hyphenated thermograviometric analysis (TGA) techniques, i.e., TGA combined with Fourier transform infrared spectroscopy (FT-IR), mass spectroscopy, gas chromatography, differential scanning calorimetry and differential thermal analysis. There are already many excellent textbooks on the basic principles of these methods. Therefore, the main objective of the present book is to discuss a wide range of applications of the spectroscopic techniques for the analysis of rubbery materials. The contents of this book are of interest to chemists, physicists, material scientists and technologists who seek a better understanding of rubbery materials. 

J. L. Caslavsky, Principles of the Optical Differential Thermal Analysis , U.S. Army Laboratory Command, MTL TR 88-11, U.S. Army Materials Technology Laboratory, Watertown, MA (1988). 

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