Differential thermal analysis alumina

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). 

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... 

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. 

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...

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 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. 

Differential thermal analysis (DTA) is based on heat transfer between the matter (absorption or liberation of heat) and the environment. The heat transfer is measured at a different temperature with respect to an inert material, for example, calcined alumina. The thermographs obtained are compared with model ones of known materials and processes such as dehydration, decarbonation, oxidation, crystalline transition, decomposition or lattice destruction. 

In conventional differential thermal analysis (DTA), the temperature at the center of the sample is compared with a reference material (often powdered alumina) as both are heated at a uniform rate. Any change in the sample s specific heat as at Tg, any structural change that is endothermic or exothermic as at T , or chemical reactions will show as changes in the temperature difference between sample and reference T. A primitive instrument consists of thermocouples inserted in the sample and the reference. The sample and the reference material are held in a heated metal block at a controlled temperature Tq. As Tq is raised (a rate of 10°C/min is common), Tj and follow perhaps by as little as 0.1°C. If an endothermic reaction takes place, Tj will lag behind temporarily. If an exothermic reaction takes place, will exceed Tj temporarily. Superficially, DTA resembles DSC in that temperatures of a sample and a reference material are increased at almost the same rate. However, in DTA the difference in temperature, AT, is the measured quantity rather than the difference in... 

Pask, j. a. Davis, B. 1954. Thermal arudysis of clays and acid extraction of alumina from clays. Differential Analysis, US Bureau of Mines, Denver. 

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