Furnaces wire-wound

The design of a cell that is compatible with more than one technique was illustrated by Couves et al. (1991). They briefly presented a cell design that allowed the collection of both XAFS spectra (in a dispersive geometry) and X-ray diffractograms. The cell operated at atmospheric pressure and included a pressed wafer of the catalyst. Little detail was provided, but the authors stated that the cell consisted of a custom-built Kanthal heating element embedded in a pyrophyllite block with a recess for the pressed sample. The sample could be heated to 1073 K in a flow of gas. More detail of the design was published by Dent et al. (1995). In essence, there is an outer container fabricated from aluminum that has the necessary Kapton windows and water-cooled end caps. A pyrophyllite heat shield fits inside the outer container, and a wire-wound heater, into which the sample holder fits, is placed inside this heat shield. The furnace was capable of operation from 373 to 1473 K. 

Miller and Wood (92) described the calorimetric accuracy and performance of the Du Pont high-temperature (1200 0 DTA cell. This furnace and sample holder are shown in Figure 6.41. Samples are contained in platinum cups inserted over platinum-platinum, 10% rhodium thermocouples and are surrounded by an alumina tube which is heated with a Kanthal-wire-wound furnace. 

An apparatus for simultaneous electrothermal analysis (ETA) and dil-atometry has been described by Judd and Pope (1051. It consisted of a thermal aluminous porcelain 525 tube mounted horizontally in a Kanthal wire-wound tube furnace capable of operation up to a temperature of 1250°C. The tube is reduced to a narrow neck at one end to which a vacuum line is connected. Fixed to the other end of the lube is a metal bracket fitted with... 

Furnaces operating in air at temperatures up to 1300°C usually use wire-wound Cr alloys. 

A Kanthal wire-wound furnace enabled the temperature to be controlled to 5 °C at 700, 725, 750, 775 and 800 °C. The cell assembly consisted of a round-bottomed silica container with a ground fiat flange at the upper open end, tightly connected to a flanged Pyrex manifold, through which a thermocouple sheath and various... 

Nitrogen gas pyrolysis system was designed and set up to transform the PAN hollow fiber membrane into PAN-based carbon hollow fiber membrane. The instrument involved in this system is illustrated in Fig. 5.3. Caibolite (Model CTF 12/65/550) wire wound tube furnace with the Eurotherm 2416CC temperature control system is used for the pyrolysis of the PAN hollow fiber membrane. The furnace can be operated at a maximum temperature of 1200°C and has the abihty to control the heating rate and the thermal soak time during the pyrolysis process. 

A test rig (as shown in Fig.l) was developed for purpose of hot wear up to 900°C. The pin (4) and disc (5) specimens are placed at the center of a wire-wound tube furnace (3) which temperature range can be changed from room to 900°C by an instrument. The pin and disc are mounted in holders at the end of resistant hot steel tubes filled with insulating... 

The furnace and thermostatic mortar. For heating the tube packing, a small electric furnace N has been found to be more satisfactory than a row of gas burners. The type used consists of a silica tube (I s cm. in diameter and 25 cm. long) wound with nichrome wire and contained in an asbestos cylinder, the annular space being lagged the ends of the asbestos cylinder being closed by asbestos semi-circles built round the porcelain furnace tube. The furnace is controlled by a Simmerstat that has been calibrated at 680 against a bimetal pyrometer, and the furnace temperature is checked by this method from time to time. The furnace is equipped with a small steel bar attached to the asbestos and is thus mounted on an ordinary laboratory stand the Simmerstat may then be placed immediately underneath it on the baseplate of this stand, or alternatively the furnace may be built on to the top of the Simmerstat box. 

The checkers used a Hoskins tube furnace, type FD303A (Central Scientific Co.), 17 in. long. The heater for the sublimation vessel was wound in two sections with heating wire in such a way that a decreasing temperature gradient in the direction of the pyrolysis oven was maintained. The open end of the heater was closed by an asbestos end plate which could be heated independently by a small nichrome coil. 

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-... 

Furnaces. Electric furnaces are used for higher temperatures. These are obtainable commercially, but satisfactory ones can be made in the laboratory (see Fig. 24-1). A pregrooved Alundum core is wound with suitable heating wire (nichrome, Chromel A, Kanthal) of 12 to 20 gauge, and covered with a thick coating of Alundum cement. This is surrounded by several inches of powdered magnesia, for thermal insulation, in a large... 

Compton J. Opticod 80c. Amer., 1922, 6, 910) describes a furnace consisting of a tube of sheet tungsten wound with tungsten wire. 

At temperatures close to 20 20°, water is a suitable liquid for a thermostat. At higher temperatures it is more convenient to use a fluid such as silicone oil, or above 200°, molten metals. A typical furnace is shown in Fig. 5. A silica former is wound with nichrome wire such that the pitch decreases from one end to the centre and then increases again to the other end. Since heat losses are greatest at the ends this provides a rough correction. An inconel tube also evens out the tempera-... 

Mounted Thermocouples.—The question of properly mounting and protecting a thermocouple is of great importance. The type of protection necessary depends upon the particular industrial process for which a couple is employed. In the laboratory if it be desired to measure the temperature of a perfectly clean platinum-wound porcelain furnace containing no material such as iron, etc. which could contaminate platinum, a rare-metal couple may be used without any protection whatever. For most laboratory experiments, however, a rare-metal couple requires protection. The usual rare-metal couple consists of wires 0.5 mm. or preferably 0.6 mm. in diameter and from 50 to 125 cm. in length. Wires as small as 0.1 mm. and even less are frequently used for special research work. One or both of the wires are insulated by threading them through small porcelain or quartz tubes. 

Fig. 1. Apparatus for the preparation of CSe2. I. Dichloromethane vapor generator. 250-mL, three-neck flask with gas inlet, a funnel containing CH2Cl2 with a pressure-equalizing arm and a connecting tube (lb). Ia is a 250-mL heating mantle. II. 60X3 cm Pyrex tube. Section Ila (ca. 15 cm long) is wound with nichrome wire and is insulated by packing with asbestos pulp. The tube is mounted on a Mutiple Unit Furnace (lib). III. Vacuum connector adapter with one end extended as shown. IV. 250- or 500-mL round-bottom flask placed in a dry ice/acetone bath.

The furnace consisted of an alundum core, which was wound with platinum-20% rhodium resistance wire. A booster coil of Nichrome wire was also wound on the two ends of the core this was used only for the very high-temperature work. The differential temperatures were detected with platinum versus platinum-10% rhodium thermocouples, inserted in the indentations of the platinum sample and reference cups. To shield the thermocouple wires, platinum foil was wound around the ceramic insulating tubes used to bring them into the furnace hot zone. 

One of the first precise vacuum or inert-atmosphere instruments was designed and constructed by Whitehead and Breger (37). The furnace was constructed from an alundum core, 9 in. in length by 2 in. ID, wound with Chromel A resistance wire. The core was shielded by four sheet-nickel cylinders, mounted on three posts, and the entire assembly was placed inside a 12 x 24-in. Pyrex bell jar. All electrical connections were made through the bottom of the bell jar mounting base. The sample block was made in the dimensions shown from Type 446 or 309 stainless steel. The furnace heating rate was controlled by a Leeds and Northrup Micromax controller the differential temperatures were recorded on a Beckman Photocell recorder. 

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