Ceramic tubes

In both glass and metal-ceramic tubes, the insulating material serves not only as an insulator, but for other purposes as well ... 

The metal envelope of a metal-ceramic tube can be adapted to tbe shape desired. Production is standard technology. 

There is a trend in the last years to extend the application range of metal-ceramic tubes also to medium power portable equipment 160kV to 300kV portable systems are well known in the market. 

An advantage of the use of ceramics over the use of glass as an insulator in X-ray tubes is the larger freedom in design due to better stability and more reliable quality of the ceramics. Therefore, typical markets for metal-ceramic tubes are applications where only a relatively low amount of tubes, but in special designs, are used. 

Our company is dedicated solely to metal-ceramic X-ray tubes since 25 years over this time, we have made lots of different tube models especially for tyre inspection systems. The major reasons for the use of metal-ceramic tubes in this inspection technology are robustness, their small and individual shapes, and the frequent need for modifications of their design due to custom designed systems. 

Another type of membrane is the dynamic membrane, formed by dynamically coating a selective membrane layer on a finely porous support. Advantages for these membranes are high water flux, generation and regeneration in situ abiUty to withstand elevated temperatures and corrosive feeds, and relatively low capital and operating costs. Several membrane materials are available, but most of the work has been done with composites of hydrous zirconium oxide and poly(acryhc acid) on porous stainless steel or ceramic tubes. 

Temperature Measurement This is usually simple, and standard temperature-sensing elements are adequate for continuous use. Because of the high abrasion wear on horizontal protection tubes, vertical installations are frequently used. In highly corrosive atmospheres in which metallic protection tubes cannot be used, short, heavy ceramic tubes have been used successfully. 

Fig. 4.4. Stages in zone refining o bar of impure silicon (a) We start with a bar that has a uniform concentration of impurity, Q. (b) The left-hand end of the bar is melted by o small electric tube furnace, making a liquid zone. The bar is encapsulated in a ceramic tube to stop the liquid running away. ( ) The furnace is moved off to the right, pulling the zone with it. (d) As the zone moves, it takes in more impurity from the melted solid on the right than it leaves behind in the freshly frozen solid on the left. The surplus pushes up the concentration of impurity in the zone, which in turn pushes up the concentration of impurity in the next layer of solid frozen from it. (e) Eventually we reach steady state, (f) When the zone gets to the end of the bar the concentrations in both solid and liquid increase rapidly, (g) How we set up eqn. (4.1).

Ceramic candles, which are thimble-shaped, porous, acid-resistant ceramic tubes. Although efficiencies exceeding 98% have been reported, the candles have high maintenance requirements because they are very fragile. 

Conventional batteries consist of a liquid electrolyte separating two solid electrodes. In the Na/S battery this is inverted a solid electrolyte separates two liquid electrodes a ceramic tube made from the solid electrolyte sodium /5-alumina (p. 249) separates an inner pool of molten. sodium (mp 98°) from an outer bath of molten sulfur (mp 119°) and allows Na" " ions to pass through. The whole system is sealed and is encased in a stainless steel canister which also serves as the sulfur-electrode current collector. Within the battery, the current is passed by Na+ ions which pass through the solid electrolyte and react with the sulfur. The cell reaction can be written formally as... 

The/3" —alumina tube inserted in a steel cell case which forms the negative terminal. The space between the ceramic tube and the cell case is the sodium compartment. 

The cell is hermetically sealed. This is performed by a glass connection from the / "-alumina ceramic tube to a ring of a-alumina. Metal parts are connected to the a -alumina by thermocompression bonding and the metal parts are either con-... 

We wish to test a new type of ceramic tube to the AljOg tube normally used to fabricate high-pressure sodium lamps in order to eompare lamp qualities and life-time operation. Select a method which would produce the desired results and describe how this would be accomplished. Note that the ceramic tube requires both strength and a high melting point. 

Commercial porous ceramic tubes (SCT /US Filter Membralox Tl-70 [7]) were used in this study as support for the zeolite material. They are made (Figure 1) of three consecutive layers of tnacroporous a-Al203 with average pore sizes decreasing from the external to the internal layer. A thin toplayer made of mesoporous y-Al203 was also present in some samples. For gas permeability, gas separation and catalytic measurements the tubes were first sealed at both ends with an enamel layer before zeolite synthesis. Tubes with porous lengths up to 20 cm were used in this study. 

Controlled furnace-type pyrolyser a, heater b, A1 block c, variable transformer d, gas outlet to column e, Swagelok union f, column oven g, gas inlet h, cement i, glass wool plug j, insulating block k, pyrometer 1, stainless steel chamber m, sample n, heater thermocouple o, pyrolysis tube p, ceramic tube q, line voltage. 

Figure 6.16 Car exhaust sensor (schematic) fitted with a stabilized zirconia ceramic tube as electrolyte.

The copyrolysis of 1 wt% dibromotetrafluoro-p-xylylene with commercially available hexafluoro-p-xylene (Aldrich) with metals was examined and it was found that it was indeed possible to prepare films that were spectroscopically indistinguishable from those deposited from dimer. The PA-F films obtained are of excellent quality, having dielectric constants of2.2-2.3 at 1 MHz and dissociation temperatures up to 530°C in N2. A uniformity of better than 10% can be routinely achieved with a 0.5-gm-thick film on a 5-in. silicon wafer with no measurable impurities as determined by XPS. During a typical deposition, the precursor was maintained at 50°C, the reaction zone (a ceramic tube packed with Cu or Ni) was kept at 375-550°C, and the substrate was cooled to -10 to -20°C. The deposited film had an atomic composition, C F 0 = 66 33 1 3 as determined by XPS. Except for 0, no impurities were detected. Within instrumental error, the film is stoichiometric. Poly(tetrafluoro-p-xylylene) has a theoretical composition ofC F = 2 1. Figure 18.2 illustrates the XPS ofthe binding energy... 

As mentioned above, many variants of the Dohrmann total organic carbon analyser are available, ranging from low-cost non-automated analysers based on sample combustion in a platinum boat (DC8JA) or using persulphate oxidation/ultraviolet irradiation (DC 88) to top-of-range fully automated and computerized systems based on combustion in a ceramic tube (DC 90) or combined simultaneous persulphate-ultraviolet oxidation (DC 180). Only one of these systems, the DC 180, is discussed below in any detail. 

Fig. 15. Simplified diagram of scanning Fabry - Perot interferometer77 showing piezoelectric ceramic tube (P), multilayer dielectric mirrors (Mj, M2), micrometer adjustment for parallelism (X, Y). Mirror spacing (d) is adjustable...

Electric tube furnaces of appropriate dimensions are available from various manufacturers. A model RO 4/25 by Heraeus GmbH, Hanau, FRG is suitable. However, a very satisfactory furnace can be built by any well equipped laboratory workshop at little cost and effort. The material required consists of thin walled ceramic tubing, 3.5 cm i.d., nichrome resistance wire, heat resistant insulation, and ordinary hardware material. A technical drawing will be provided by the submitters upon request. The temperature of the furnace can be adjusted by an electronic temperature controller using a thermocouple sensor. A 1.5 kW-Variac transformer and any high temperature thermometer would do as well for the budget-minded chemist. 

Krause et al. (1973) carried out the last detailed U.S. experimental investigation of the smelt-water explosion phenomenon. A large number of experiments were conducted with variations in the smelt composition. The scale was quite small with 0.03-1 g quantities of water injected at high velocity (20-30 m/sec) onto the surface of the smelt. A few tests were also made with small drops (0.8-0.3 g) of water on the end of a ceramic tube that was dropped into the smelt. Some information concerning pres-... 

Ohya, H., Y. Tanaka, M. Niwa, R. Hongladaromp, Y. Negismi and K. Matsumoto. 1986. Preparation of composite microporous glass membrane on ceramic tubing. Maku 11 41-44. 

Atmospheric pressure chemical ionization (APCI) is a gas phase ionization process based on ion-molecule reactions between a neutral molecule and reactant ions [31]. The method is very similar to chemical ionization with the difference that ionization occurs at atmospheric pressure. APCI requires that the liquid sample is completely evaporated (Fig. 1.12). Typical flow rates are in the range 200-1000 xL min , but low flow APCI has also been described. First, an aerosol is formed with the help of a pneumatic nebulizer using nitrogen. The aerosol is directly formed in a heated quartz or ceramic tube (typical temperatures 200-500 °C) where the mobile phase and the analytes are evaporated. The temperature of the nebulized mobile phase itself remains in the range 120-150 °C due to evapo-... 

Figure 1 shows a schematic (elevation) of the Plastofrost apparatus as modified for the present study. The two main components are the heater and the coking attachment. The heater consists of a nickel-plated copper slab in which four 300 watt cartridge heaters are enclosed. A chromel/alumel thermocouple insulated with ceramic tubing placed 5 mm beneath the top surface of the slab measures the temperature (see Fig. 1). The bead of the TC is at the centre of the slab. Figure 2 is a photograph of the assembled apparatus.

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