Furnace heating elements

Sources emitting radiation characteristic of element of interest (hollow-cathode lamp). Flame or electrically heated furnace or carbon rod. Monochromator, photomultiplier, recorder. 

In general, the nitrides of most of the metals and many of the nonmetals may be prepared by heating the elements together. Owing to the inactivity of nitrogen at ordinary temperatures, it is usually necessary to heat to a very high temperature. Consequently, the formation of nitrides is often observed in electric furnace work. Magnesium nitride is one of the nitrides easiest to prepare. 

Preparation and uses of phosphorus. The preparation of elemental (white) phosphorus is carried out in an electrically heated furnace into which a mixture of phosphate rock, sand, and coke is fed continuously... 

For operation at low temperature, the furnace may be surrounded by a Dewar flask and precooled with liquid nitrogen. The furnace is then heated by the furnace element using a heating-mode program. Another method is to use a gas as a heat exchange medium, such as is illustrated in Figure 6.12 (31). Most temperature programmers do not function efficiently unless a... 

Vanadium Is a refractory element determined from the wall of the furnace but otherwise using STPF conditions (Manning and Slavin, 1985). Urine diluted in 2% HNO3 and Triton X-100 was analyzed for V by Paschal and Bailey (1990) using STPF methods with a detection limit of 2//g/L in the urine. Shuttler (1992) used the transversely heated furnace (the Perkin-Elmer 4100ZL) and, with only dilution of the urine, was able to obtain a detection limit better than 0.5//g/L. 

A cool down step before the atomization step is used for longitudinally heated furnaces. This has been shown to improve sensitivity and reduce peak tailing for some refractory elements. This improves the accuracy of the measurement for these elements. The cool down step is not used in transversely heated furnaces. 

Figure 9.8 illustrates a problem that can occur with any furnace element—sample contamination. The sample is a-SiC, which was heated in a tungsten furnace for 12 hours at 1300°C. The dark features are tungsten particles evaporated onto the surface during heat treatment. 

Better design of furnace" elements, sQch" as 3anTer nozzles, new materials for insulation, and better design of heat exchangers, may increase the saving of energy and improve the operability of the installations. 

Early work for producing high modulus fiber used a resistive heated furnace with a British Acheson grade CS graphite tube element, with power fed to each end through a... 

The most common types of sintering furnaces are electrical resistance furnaces in which a current carrying resistor, commonly called the furnace element or winding, provides the source of heat. In addition to size and cost, important considerations in the selection of a furnace are the maximum temperature capability and the atmosphere in which it can be operated for extended periods. Table 12.1 provides a selected list of common furnace elements. Several metal alloys (e.g., nichrome) can be used as furnace elements for temperatures up to 1200°C in both oxidizing and reducing atmospheres. For extended use in air, other furnace elements can deliver higher temperatures e.g., Pt (up to 1400°C) SiC (1450°C) ... 

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