Thermoanalyzers

The camera is mounted directly above the thermoanalyzer, its furnace is connected to the heated system of the impact plates through the heated vacuum-tight link. The vacuum in the balance is maintained by means of a shut-off valve, only the camera has to be opened during the sample change and evacuated afterwards. 

The preparation of Ba02 was carried out by decomposition of BaC03 in high vacuum 10-6 mm on the thermobalance (METTLER Thermoanalyzer) at 800 °C to BaO and subsequent oxidation with dry oxygen (Fig. 55). The complete oxidation could be achieved only after cycling in the temperature region 500 to 600 °C. 

The adsorption isotherms of xenon were measured at 34°C using a classical volumetric apparatus. The 29xe-NMR measurements were performed at the same temperature on a Bruker CXP-200 spectrometer operating at 55.3 MHz. The n-hexane adsorptions were conducted at 90°C on a Stanton Redcroft STA-780 thermoanalyzer. The samples were submitted to a preliminary calcination under dry air up to 650°C with a heating rate of 10°C/min. 

TG-DTG-DTA-T-P, Mettler Instrument Corporation, Company Brochure 79) TA 2000 C, Thermoanalyzer for Simultaneous TG-DSC,... 

Thermographic investigations were carried out on synchronous thermoanalyzer STA-409 PC in a polythermal regime in an interval of temperatures of 293-1273 K with speed of heating of 10 degrees/min in a argon current of the high cleanliness. 

Thermal analysis was carried out on selected samples using a Netzsch STA thermoanalyzer mod. 409. 

Glass temperatures have been determined by the DTA method with two different instruments (a Mettler differential thermoanalyzer and a Perkin-Elmer differential scanning calorimeter DSC 1) (9) in two different laboratories. They are listed in the two last columns of Table I. Small differences of 0°—7°C. were observed. This order of agreement was sufficient. 

Catalyst Acidity bv Ammonia Chemisorption. Plant performances below expectations were reported by two units, in which the original alumina based catalysts were replaced. Surface area specifications were 150-200 m2/g for both catalysts. Acidity was measured by ammonia chemisorption using a recording vacuum thermoanalyzer with a TGA sample holder, and was correlated with BET surface area, as shown in Table V. 

The experimental device (Fig. 1), is based on a dynamic gravimetric method. It is composed of three main parts. The thermoanalyzer (TG-DSCl 11 Setaram, France) provides... 

Because of the suspected decomposition of anhydrite, CaSO4, in lithium-based tetraborate flux systems at elevated temperatures, it was decided to study their behavior by means of thennal analysis (TGA, DTA). Thermal scans were performed on the Mettler TA-2 thermoanalyzer equipped with a DTA-20 macroholder. Platinum crucibles were filled with 200 mg of specimen flux mixtures and balanced by equal portions of alumina as the reference material. All specimens were heated at a rate of 10 C/min in an oxidation atmosphere (stream of air). 

Calorimetry. The glass transition temperatures (Tg s) of the ionic polyesters were determined under nitrogen on a DuPont 990 thermoanalyzer. Heating and cooling rates were 10°C/min. 

The coke content of the catalysts was measured by combustion-volumetry after the run. The differential thermal analysis (DTA) of the used catalysts was performed with an Aminco Thermoanalyzer using oxygen as dynamic gas. The soluble fraction of coke from used catalysts was extracted with solvents and the solutions were analyzed by several techniques in order to determine their nature. 

The Mettler TA1 thermoanalyzer, as developed by Wiedemann (3, 60), was perhaps the most elaborate and versatile of any thermobalance ever constructed. It is no longer available commercially, having been superseded by the Mettler TA 2000 and TA 3000 systems. However, because of its uniqueness, the Mettler TAl is described here. 

The Mettler TA 2000 C chermoanalyzer system permits simultaneous TG-DSC measurements from 25-1200cC at pressures from atmospheric to 10 5 mbar. With a special furnace, a corrosive gas atmosphere can also be used. A schematic diagram of the thermoanalyzer is shown in Figure 3.24. 

Bart et al. (62) have described the enclosure of a Mettler TA-1 thermoanalyzer in a sealed system in order to permit the examination of samples containing alpha and beta/gamma emissions. Samples containing plutonium and uranium may be studied by TG with no radiation hazard to the operator. All balance components could be reached through glove ports. 

The Mettler TA 2000C thermoanalyzer is a simultaneous 1 G-DSC instrument that has been previously described in Chapter 3. The data reduction... 

The first combination of thermogravimetry (TG) and a mass spectrometer was by Zitomer (36) in 1968 who coupled a Du Pont thermobalance with a time-of-flight mass spectrometer. He applied the technique to the thermal decomposition of various polymers. Lastly, Wiedemann (37) described an elaborate TG-DTA-EGD-MS system in 1969. The system consisted of a Mettler thermoanalyzer couple to a Balzer quadrupole mass spectrometer that permitted the sample to be studied at low (10 6 Torr) or normal (I atm) pressures. 

Perhaps the most widely used TG-MS system, which includes DTG. DTA, and gas pressure measurements, is the Mettler thermoanalyzer. The system, which consists of a precision thermobalance, a high-vacuum system, a mass spectrometer, and a DTA measuring system, has been described in detail by numerous investigators (68-73). 

In almost every system, the Mettler Thermoanalyzer I was coupled to a quadrupole mass spectrometer, such as is illustrated in Figure 8.14 (37. 69i. The sample may be studied under vacuum 10"6 Tom or under higher pressures to 1 atm. The reaction chamber, R. is surrounded by the furnace and separated from the balance by a diffusion baffle. The evolved gases pass directly to the mass analyzer. F. which is connected to a recorder, J. through the mass spectrometer control panel. Total pressure is determined by an ionization gauge, S, which also permits the recording of the EGD curve (in this case, due to the pressure change in the system). The relation between measured total pressure and the ion current of the calibration gas permits calibration of the mass spectrometer in absolute partial pressure units or A/Torr. 

Separate pumping systems must be employed for the thermoanalyzer and mass spectrometer if kinetics measurements were to be made. For measurements at atmospheric pressure, the arrangement given in Figure 8.15h is used. 

Yuen et al. (5) have described an automatic data acquisition system for the simultaneous operation of two Mettler Model TA-I Thermoanalyzers. A... 

Enriched phillipsite and chabazite samples, practically free from other cation exchanger phases, were obtained from the parent rocks by enrichment processes (grinding and sieving, separation by heavy liquids or magnetic table, etc.), based on the greater friability and lower density of zeolite relative to other rock constituents [12]. Chemical analysis of the two zeolites in the enriched products was performed by electron microprobe analysis (CAMECA SX50). Water content was measured by thermogravimetry (Netzsch STA 409 thermoanalyzer). 

The measurements were carried out using a Stanton-Redcroft TG 750 thermobalance and a DuPont 990 Thermoanalyzer equipped with a pressure DSC cell. 

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