Thermogravimetric analysis, procedure

In most of the studies discussed above, except for the meta-linked diamines, when the aromatic content (dianhydride and diamine chain extender), of the copolymers were increased above a certain level, the materials became insoluble and infusible 153, i79, lsi) solution to this problem with minimum sacrifice in the thermal properties of the products has been the synthesis of siloxane-amide-imides183). In this approach pyromellitic acid chloride has been utilized instead of PMDA or BTDA and the copolymers were synthesized in two steps. The first step, which involved the formation of (siloxane-amide-amic acid) intermediate was conducted at low temperatures (0-25 °C) in THF/DMAC solution. After purification of this intermediate thin films were cast on stainless steel or glass plates and imidization was obtained in high temperature ovens between 100 and 300 °C following a similar procedure that was discussed for siloxane-imide copolymers. Copolymers obtained showed good solubility in various polar solvents. DSC studies indicated the formation of two-phase morphologies. Thermogravimetric analysis showed that the thermal stability of these siloxane-amide-imide systems were comparable to those of siloxane-imide copolymers 183>. 

Among the procedures described in this chapter, reductive thermogravimetric analysis is the simplest, but not very accurate. For accurate analyses of slightly oxidized superconductors, the citrate-complexed copper titration is recommended. The difficult problem of assessing oxidation states of individual elements in Bi- and Tl-con-taining superconductors has not been addressed, and remains a significant challenge to analytical chemists. 

A saturated solution of C70 (190 mg) in benzene (150 mL) was prepared and hydrogenated following the same procedure detailed in the previous Section 7.2.2. Immediately after the hydrogenation the solution was distilled under reduced pressure in a water bath at 50°C. The cream-white residue was collected for the FT-IR and thermogravimetric analysis. 

Thermogravimetric analysis (TGA) of the co-crystals was carried out over the temperature range 25 °C to 200 °C by employing a Mettler Toledo instrument. These curves showed mass loss due to the removal of the aromatic guest molecules. The apo-hosts thus obtained did not dissolve in benzene and other aromatic solvents. The apo-hosts were immersed in the respective aromatic liquid for several hours. The crystals were then taken out, and the TGA repeated. This procedure was repeated more than once to find out whether the inclusion of the guest molecule was reversible and also whether there was any change in the temperature of decomposition or the proportion of the aromatic compound in the co-crystal, with such cycling. 

Preparation and Characterization of Lanthanide and Actinide Solids. Standard crystalline lanthanide and actinide phosphates were prepared by literature procedures (16-18) and characterized by X-ray powder diffraction, FTIR spectroscopy, and thermogravimetric analysis (TGA). Europium was used as an analogue of the trivalent actinides. Metal-phytate solids were generated by mixing Eu(III), U(VI), or Th(IV) nitrate solutions with 0.1 M phytic acid at pH 5 and metal.phytate ratios of 1 1 2 1, and 4 1. The metal phytates precipitated immediately. The resulting slurries were stirred at 85 °C for 30 days and sampled periodically for analysis of the solids by TGA, X-ray powder diffraction, and FTIR. The rate of phosphate release to the solution was monitored colorimetrically. 

The solids were characterized by X-ray diffraction using a Siemmens D-500 diffractometer equipped with a copper anode and a nickel filter. The deposition of carbon was studied by thermogravimetric analysis (TGA) using a Perkin-Elmer 1700 TGA analyzer. For the TGA runs the sample was heated at 10°C/min in air (2.0 1/h) from ambient temperature (20 C) to 850°C the procedure was repeated to eliminate Ae effect of adsorbed water. 

Determination of the optimal heat treatment temperature in the reactor is done by differential thermal analysis (DTA) and thermogravimetric analysis (TG) it appears (Fig. 2) that in our experimental procedure, for all the studied granulometries (<25 to 250 gm), a specimen fired at 398 K for 3 h contains no mote gypsum, and a specimen fired at 423 K still contains almost only hemihydrate. Above this temperature anhydrite III appears. The very small amount of anhydrite 111 contained in a specimen fired at 423 K is different from a gypsum variety, but quite stable and characteristic for a variety of gypsum (Fig. 6) fZ]. 

The catalysts were characterized by N2 adsorption-desorption isotherms, thermogravimetric analysis (TGA), temperature-programmed desorption of ammonia (NH3-TPD), X-ray diffraction (XRD), Raman spectroscopy, in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and X-ray photoelectron spectroscopy (XPS). The procedures and experimental conditions have been detailed elsewhere [9]. 

Other workers have prepared poly(V-methylpyrrole)/poly(biphenol-A-carbon-ate) (PC) using this approach.68 The electrodes were dip-coated with the PC and then electropolymerization was induced. Thermogravimetric analysis verified that a graft copolymer was produced. A similar procedure has been used to prepare PAn composites with the same host polymer.69 The in situ electrochemical polymerization process has also been used to prepare polyacrylonitrile/PPy composite films.70... 

The resistance dependence and thermogravimetric analysis (TGA) of Er-Ba Cu O has been measured in the temperature range 2/ C to 920 C. The heat treatments and oxygen flow rates simulated actual sintering and annealing processes used in sample preparation. Evidence of a phase transition in Er Ba Cu O near 680 C is discussed, as well as the implications of the maximum oxygen uptake near 400 C. The impact of sample preparation procedures on sample features is also discussed. 

In this paper we have measured the resistance dependence and oxygen content of Er Ba2Cu 0Q and Y.Ba Cu OQ - samples above room temperature under the conditions or a simulated sintering and annealing process. The results provide insight into the importance of specific sample preparation procedures. We will start with a detailed discussion of the two most common preparation procedures for copper oxide superconductors at this moment the solid state reaction method and the coprecipitation method. A discussion of the resistance and thermogravimetric analysis (TGA) data and how it correlates to the sample formation will follow. 

The purity of the compounds was characterized by elemental analysis, molecular analysis ( H NMR, mass spectrometry), thermodifferential and thermogravimetric analysis and separative techniques such as HPLC, GC and capillary zone electrophoresis [127]. This procedure provided highly pure products for use in the interlaboratory studies, e.g. arsenobetaine was shown to be more than 99.8% pure. 

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