Thermogravimetric system

He thank Professor J. Hightower for allowing the use of his thermogravimetric system Dr. F. S. S. Hwu for many helpful suggestions during the sorption measurements and Dr. J. Lester for assistance with IR data generation. Thanks are also due to Drs. H. E. Swift and J. V. Kennedy for critically reviewing this manuscript. 

Table I summarizes the characteristics of nickel catalysts prepared onto these supports. For brevity these catalysts will be referred to by a notation in the form aA-fi. For example, 7AAP-573 represents a 7 wt % Ni catalyst supported on A O 2A1P0 reduced at 573 K for 1 h. Incidentally, this sample did not reduce under these conditions and was excluded from further kinetic studies. Notations for the other catalysts are shown in the first column of Table I. All samples were reduced at the specified temperature for 1 h unless noted otherwise. The percent reduction was determined by measuring oxygen uptake at 673 K in a commercial thermogravimetric system (Cahn 113). The average particle size was determined by either X-ray diffraction line broadening or magnetic measurements (see below).

Charsley, E.L. Rooney, J.J. Hill, J.O. Parkes, G.M.P. Barnes, P.A. Dawson, E.A. Development and applications of a preparative scale sample controlled thermogravimetric system. J. Therm. Anal. Calorim. 2003, 72, 1091. 

A thermogravimetric system capable of operating at a wide range of temperatures was used to measure... 

A typical thermogravimetric system is illustrated in Figs. 7.2 and 73, based on the classical, high-precision instrument, the Mettler Thermoanalyzer, first described in detail by Wiedemann in 1964. The left top sketch in Fig. 72 shows a view of a basic thermoanalyzer installation. The center table provides space for the high temperature furnace, the balance, and the basic vacuum equipment. The cabinet on the right houses the control electronics and the recorder. On the left is the work bench and gas cleaning setup. 

Ber] Thermomechanical system (TMS), thermogravimetric system (TGS) studies Magnetization, electrical resistance, hardness... 

Phase relationships ia the system K O—B2O2—H2O have been described and a portion of the phase diagram is given ia Figure 8. The tetrahydrate, which can be dried at 65°C without loss of water of crystallisation, begias to dehydrate between 85 and 111°C, depending on the partial pressure of water vapor ia the atmosphere. This conversion is reversible and has a heat of dehydration of 86.6 kj/mol (20.7 kcal/mol) of H2O. Thermogravimetric curves iadicate that two moles of water are lost between 112 and 140°C, one more between 200 and 230°C and the last between 250 and 290°C (121). 

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>. 

Fig. 14 Schematic diagram of apparatus suitable for thermogravimetric analysis. The experimental observable is the percent weight loss of the sample, which will be plotted as a function of the system temperature.

The fluorine content, density, critical surface energy, glass transitions, thermal expansion coefficient above and below the glass transition, and 300°C isothermal thermogravimetric stabilities of the fluoromethylene cyanate ester resin system with n = 3, 4, 6, 8, 10 are summarized Table 2.2. Also included for the purpose of comparison are the corresponding data for the aromatic cyanate ester resin based on the dicyanate of 6F bisphenol A (AroCy F, Ciba Geigy). 

Dynamic mechanical anlaysis (DMA) measurements were done on a Rheometrics RDS-7700 rheometer in torsional rectangular geometry mode using 60 x 12 x 3 mm samples at 0.05% strain and 1 Hz. Differential scanning calorimetry (DSC), thermomechanical analysis (TMA), and thermogravimetric analysis (TGA) were performed on a Perkin-Elmer 7000 thermal analysis system. 

The XPS data were acquired on a Physical Electronics model 5400 XPS system using a Mg anode. For survey spectra, the pass energy was 44.75 eV with a step size of 0.5 eV. The time per step was 50 msec. High resolution spectra were acquired with a pass energy of 35.75 eV and step size of 0.1 eV, The time per step was 50 msec. Thermogravimetric data were obtained on a Perkin-Elmer, Diamond Thermogravimetric/ Differential Thermal Analyzer (TG/DTA) with Pyris software, version 7.0-0.0110. 

The thermal properties of benzoic acid were evaluated using simultaneous differential thermal analysis (DTA) and thermogravimetric analysis (TGA). This work was performed on a Shimadzu DT-30 Thermal Analyzer system, which was calibrated using indium standard. Using a heating rate of 10°C/min, the thermograms presented in Figure 3 were obtained. 

A plot of AGq versus In x would be linear, the slope giving n the value of n gives information about the types of defects involved. For doubly ionized metal vacancies, Vm , m = 6 for Vm, m = 4 and so on. Isothermal AGq — In x plots can be constructed from equilibrium thermogravimetric data or electrochemical measurements. A typical AGqj — log X plot for the Fe, 0 system is shown in Fig. 5.4, where n values corresponding to various regions are indicated. We see that n = 6 applies when X 0.09, while n = 5, corresponding to pairs, also applies close to this... 

Thermogravimetric analyzer unit, data acquisition system with a printer or plotter... 

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