Aluminas thermal analysis

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. 

Differential Thermal Analysis. High temperature differential thermal analyses were obtained with a Dupont Model 1200 instrument. Samples were heated from room temperature to 950° C at a rate of 20°C/min in a slow stream of hydrogen. Molybdenum cups were used to hold the sample and alumina reference. The instrument was calibrated with sodium chloride (mp 800° C). 

Furnaces for thermal analysis instruments are nearly always electric resistance heated. Wound furnaces consist of a refractory metal wire wrapped around or within4 an alumina or other refractory tube. Nichrome (nickel/chromium alloy) or Kanthal (a trade name for an iron/chromium alloy 72% Fe, 5% Al, 22% Cr,. 5% Co) windings may be used inexpensively for heating to a maximum temperature of 1300°C. More expensive plat-... 

Use a differential scanning colorimeter (DSC) or differential thermal analysis (DTA) apparatus 1 with aluminium oxide ( a - alumina) as the reference substance. 

Unlike divalent oxides, the solubility of alumina is low and hence some warm temperature treatment is required. In addition, rather than using lower solubility phosphate solutions such as ammonium and potassium phosphate solutions, phosphoric acid solution is directly used. Wagh et al. [ 17] employed a thermodynamic analysis to study the elfect of the temperature on the solubility of individual phases of alumina on the formation of its phosphate phases during heat treatment where solubility of hydrated aluminum oxide, viz., hydrargillite (A1203-3H20) is enhanced, and that contributes further to the formation of berlinite phase. They confirmed this by differential thermal analysis (DTA) and X-ray diffraction (XRD) analysis on samples heated beyond 118°C. 

Differential thermal analysis. The phenomena of adsorption and desorption of water and the loss of physically bound water have been investigated by differential thermal analysis (112,151a). In this method, a small amount of the sample to be examined and a sample of inert material (e.g., calcined alumina) are placed in separate wells in a nickel block. A thermocouple junction is placed in each of the samples and the thermocouple leads are connected in series but with opposing e.m.f. s. The nickel... 

To illustrate the feasibility of the proposed closed loop process, pure iron oxide FejOt was subjected to a producer gas from a 100 kW fluidised bed gasifier (reaction 1) and subsequently exposed to water vapour (reaction 2). For the reduction, Fej04 powder was placed in alumina cmcibles and heated in a tubular furnace at 900 °C and 1000 C, respectively while being exposed to a flow of producer gas for at least 25 minutes. The characterisation of the product by powder X-ray diffractometry and thermal analysis revealed that Fci. O indeed is the main product. Metallic iron and carbonaceous materials were identified as by- products. Generally, samples prepared at... 

Instrumental. The Mettler TA2000B thermal analysis system is equipped with an interface system, and Hewlett-Packard 9815 desk top calculator and 7225 plotter. Samples, weighing 5-10 mg, sealed in aluminum pans and under a nitrogen blanket, were heated in the calorimeter at a rate of 10 deg/min from -35 or 10 deg C to 180 deg C respectively, for specific heat and kinetic scans. Specific heat measurements were calibrated with alumina to an accuracy of 3%. Temperatures and enthalpies were calibrated with an Indium sample. The accuracies were .02 deg C and 2% (Indium 28.5 J/g), respectively. 

Thermal analysis results of chromia/alumina samples. 

Sintered deposits form at the furnace exit at lower gas temperatures and in zones subject to rapid changes in direction. The deposit is composed of spheroidal particles, <40p, bound together by a molten substance. In those cases where substantial quantities of coarse pyrites are liberated from the pulverized coal, the spheroids are nearly pure FeaOa, as shown in Figure 11. The matrix contained silica, alumina, iron, and potassium, and has an initial deformation temperature of 1832°C, as determined by differential thermal analysis. The heavier pure iron spheroids deposit as a result of inertial impact. The mineral source of the molten phase is most likely illite. 

The TG-DSC curves were measured on a Netzsch 409 EP Simultaneous Thermal Analysis device, using 20 mg of powdered sample. To analyse the effect of heat treatment of the samples, the experiments were carried out heating in air at a rate of 5 °C min, from ambient to lOOOT, using a-alumina as a reference. 

In this paper, two studies are presented. The first one concerns the system described by Yada et al. [15, 16]. The aim was to understand the unstability of the material upon calcination by thermal analysis and to elucidate the mechanism of formation of such a material by fluorescence techniques. The second part of the article describes an original method to prepare mesoporous alumina with high pore volume and surface area in the... 

In differential thermal analysis, the starch is intimately mixed with a thermally inert materiaP such as calcined kaolin or alumina the mixture is heated at a uniform rate, and the temperature of the mixture is compared with that of a sample of the pure, inert material heated in the identical manner. Any exothermic or endothermic reaction in the starch causes a positive or negative temperature-difference between the two samples this can be recorded, and appears as a positive or negative peak on the resultant thermogram. Differential thermal analysis can be conducted in different atmospheres, such as air, oxygen, or nitrogen, or under vacuum. 

Figure 6. Differential thermal analysis of an alumina used during 30 h. Conditions pressure, 30 atm Hs naphtha molar ratio, 8 temperature, 515°C and...

Thermal Analyses. Samples of Na/BaA were weighed into sample tubes and subjected to DTA up to 500°C. Great care was taken to ensure even packing of sample and reference material. Two series of experiments were carried out with alumina and NaA as reference material, respectively. Representative samples were also examined by TGA. Thermal analyses were performed using a DuPont 900 thermal analysis unit with a 950 TGA attachment. 

Figure 5 Thermal analysis curve for high alumina cement...

Filled PVC compounds can be flame-retarded by alumina trihydrate. Figure 5.9 shows the burning time of flame-retarded PVC plasticized by 50 phr. of di-isooctyl phthalate. Extinction time after the ignition of a horizontal rod specimen at environmental temperature of 100 or 120 °C is plotted against the additive content. In Figure 5.10, differential thermal analysis (DTA) curves of the same PVC compounds are presented. 

Thermal analysis curves of NH4 p-gallate are shown in Figs 13.2 and 13 314 weight loss below 180 °C in Fig. 13.3 is attributed to water accordingly, the stoichiometry of this specimen may be determined from the weight losses caused by de-ammoniation at c. 230 °C and dehydration at c. 480 °C. The fact that the crystal is stoichiometric, which is determined from the TG data, is fully consistent with structure analysis. The stoichiometry of P-alumina is also confirmed by a similar TG curve... 

Reference material sets which are certified by the International Confederation for Thermal Analysis and Calorimetry (ICTAC) are available through the US National Institute of Standards and Testing (NIST), and are listed in Appendix 2.2. High-purity metals and organic compounds including polymers have been certified. If the standard reference material must be dispensed with a syringe into the sample vessel (for example cyclohexane), care must be taken to ensure that only one droplet is formed in the sample vessel. Multiple transition peaks will be observed if there is more than one droplet present. The transition temperatures listed in Appendix 2.2 are the statistical mean values of measurements made in a number of laboratories and institutes. The ICTAC reference materials are certified for temperature calibration only and not for enthalpy calibration. The reference temperatures in Appendix 2.1 should be used if very accurate calibration of the instrument is required. In order to determine the heat capacity Cp ) of a sample, sapphire (a-alumina, AI2 O3) is used as a standard reference material. The Cp of... 

Thermal gravimetric analysis and differential thermal analysis (TGA/DTA) can be performed by using a SDT 2960 Simultaneous Differential Thermal Analyzer (TA Instruments, Inc., New Castle, DE). The instrument was calibrated with gold supplied by Perkin-Ehner. Samples (70 mg) of as-prepared powders were hand-pressed in a 3 mm dual action die and placed inside Pt sample cups and heated at the rates of 10 K/ min from ambient temperature to 1400°C. The reference material was used as a pellet of a-alumina. A flow of synthetic air at 50mL/min was maintained during the experiments. 

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