Horizontal tube furnace

Two commercial coal-tar-pitch-based carbon fibres, which were supplied by Osaka Gas Co., Ltd. (Osaka, Japan), have been used as starting materials. In the course of their synthesis, these CFs had been carbonised at different temperatures Tc = 1273 K (Donacarbo S-241) and Tc = 973 K (Donacarbo SL-242). The carbon fibres have been chemically activated with KOH and NaOH (Panreac Chemicals, Barcelona, Spain) at 1023 K under a N2 gas flow. More details concerning the activation conditions can be found elsewhere. Two different kinds of furnaces have been used for the activations. For laboratory synthesis a horizontal tube furnace is used which is capable of activating about 2 g of raw fibres per activation process. For the scale-up production approach an industrial chamber furnace is used. Thereby the amount of initial material could be increased by more than one order of magnitude up to 30 g per activation process. 

Experiments of this type (Figure 3.2) are usually carried out with the reactant solids in small boat placed in a tube in a horizontal tube furnace. The gas is passed over the reactants for a time to expel all the air from the apparatus, and then flows over the reactants during the heating and cooling cycles, exiting through a bubbler to maintain a positive pressure and prevent the ingress of air by back diffusion. 

Pyrolysis Equipment and Procedure. The decant oil samples were pyrolyzed using a horizontal tube furnace equipped with an electronic temperature controller. The samples (1-2 g) were weighed into stainless steel tubes (6 mm o.d., 200 mm long), which were then flushed with nitrogen and sealed with Swagelok end caps. It was important that the sample holder be capable of complete disassembly to facilitate the recovery of the products of pyrolysis, which were largely viscous tars and coke. It had been found previously with a more elaborate flowthrough reactor system, that not all the carbonaceous reaction products could be recovered readily. 

The test specimen is placed in a quartz boat and burnt in a horizontal tube furnace. Combustion gases travel directly into the animal exposure chamber which is a hemispherical PMMA vessel of 4.2 dm mounted on a base of 203 mm dia. A vent bubbler on the top of the chamber serves for discharging the overpressure without any ingress of fresh air. A sampling port permits the chemical analysis of the gas mixture (Fig. 4.25). 

In at5q)ical operation, about 100 mg of the powdered catalyst is placed in a ceramic boat, which is positioned in a quartz tube located in a horizontal tube furnace. The sample is initially reduced in a 10% hydrogen helium stream at 600 °C and then quickly brought to the desired reaction temperature. Following this step, a predetermined mixture of hydrocarbon, hydrogen, and inert gas is introduced into the system and the reaction allowed proceeding for periods of about 2 h [6]. 

Li et al. [80] synthesized the (Sr, Ca)2Si5Ng 5%Eu red phosphors by firing the powder mixtures of alkaline earth-metal nitrides, europium nitride, and silicon nitride in an alumina horizontal tube furnace at 1300-1400 °C for 12-16 h under a flowing 90%N2-10%H2 atmosphere. The reaction is shown as... 

Figure 1.Reduction Reaction Installation Figuer2.Reduction Swelling Installation 1—gas 2—flow meter 3— flow control cabinet 4—pellet 5—electronic balance 6—quartz tube 7— vertical tube furnace 8—horizontal tube furnace 9—infrared camera 10—computer...

Thermal shock resistance tests were completed on the coating in order to assess its compatibility to thermal cycling and to study the coatings coefficient of thermal expansion (CTE) property. Five coated coupons were placed within a horizontal tube furnace and heated in an air atmosphere. A sample was removed from the furnace after being exposed to a specific temperature, namely, 400,500,600,800 and 1000°C. The dwell time for each temperature was 30 min. The removed sample was quenched in water at room temperature. 

The VLS processes are usually carried out in a horizontal tube furnace, as shown in Figure 7.1. In this schematic, the carrier gas, Ar, is introduced from the left end of the alumina tube and is pumped out from the right end. The source material is loaded on an alumina boat and positioned at the center of the highest temperature zone in the alumina tube. The substrate temperature usually drops with the distance from the position of the source material(s). The local temperature where the substrate is situated (usually 500-700 °C) determines the type of product that will be obtained. To reduce the decomposition temperature, ZnO powder is usually mixed with graphite powder to form the source mixture. At temperatures 800-1100 °C, graphite reacts with ZnO to form Zn, CO, and CO2 vapors, which then react on the substrate to form ZnO nanostructures. 

Figure 7.1 A schematic diagram of the horizontal tube furnace for growth of ZnO nanostructures by the solid apor phase process.

In a study by Kong et al. [7], single-crystal nanorings of ZnO were grown by the solid-vapor process. The raw material was a mixture ofZnO, indium oxide, and lithium carbonate powders at a weight ratio of 20 1 1, and it was placed in the highest temperature (1400 °C) zone available in a horizontal tube furnace. At such a high temperature and low pressures ( 10 Torr), ZnO decomposes into Zn + and O. ... 

Zinc oxide films on silicon and silica substrates were prepared by ultrasonic nebulization of zinc acetate solutions and thermal conversion of the zinc acetate to zinc oxide films. The procedure has been described in Section B. Zinc oxide films as deposited were annealed in a mixture of hydrogen sulfide and argon (H2S Ar = 1 1) in a horizontal tube furnace. The flow rate of the gas mixture was 50cm /min. The temperature of the furnace was raised gradually from room temperature to 500 in 4 h. The furnace was maintained at 500° for another 3 h and then cooled down slowly in the HjS/Ar atmosphere. Completion of the conversion was verified by X-ray diffraction analysis and infrared spectroscopy of the films. 

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