Pressure apparatus

Niobium carbide is used as a component of hard metals, eg, mixtures of metal carbides that are cemented with cobalt, iron, and nickel. Along with tantalum carbide, niobium carbide is added to impart toughness and shock and erosion resistance. The spiraling rise in the price of tantalum has spurred the development of a hafnium carbide—niobium carbide substitute for tantalum carbide (68). These cemented carbides are used for tool bits, drill bits, shovel teeth, and other wear-resistant components turbine blades and as dies in high pressure apparatus (see Carbides). 

In the attempt at diamond synthesis (4), much unsuccesshil effort was devoted to processes that deposited carbon at low, graphite-stable pressures. Many chemical reactions Hberating free carbon were studied at pressures then available. New high pressure apparatus was painstakingly buHt, tested, analy2ed, rebuilt, and sometimes discarded. It was generally beheved that diamond would be more likely to form at thermodynamically stable pressures. 

Fig. 3. Cross section of belt high pressure apparatus.

Static Pressure Synthesis. Diamond can form direcdy from graphite at pressures of about 13 GPa (130 kbar) and higher at temperatures of about 3300—4300 K (7). No catalyst is needed. The transformation is carried out in a static high pressure apparatus in which the sample is heated by the discharge current from a capacitor. Diamond forms in a few milliseconds and is recovered in the form of polycrystalline lumps. From this work, and studies of graphite vaporization/melting, the triple point of diamond, graphite, and molten carbon is estimated to He at 13 GPa and 5000 K (Fig. 1)... 

The AHC Wilkinson catalyst (Rh(Ph3P)3/PTA/Al203) (AHC-Wilk) was prepared using the general procedure described previously (10,12). The catalyst contained 0.5% Rh which corresponds to a 1 1 Rh PTA ratio and about a 4.5% load of the anchored complex. The hydrogenations were ran using the low pressure apparatus previously described (19) under the conditions listed in the discussion. 

High performance sealants, 22 28 High phosphorus alloys, corrosion performance of, 9 710-711 High pinning Type II superconductors, 23 High pressure apparatus, 13 413 High pressure applications, 13 436-448 in commercial products, 13 436-438 in inorganic chemistry reactions, 13 440—448... 

Piston meters, reciprocating, 11 655 Piston seals, in high pressure apparatus, 13 415... 

Figure 5.15. Pressure apparatus for measuring the amount of water held in soil at different pressures the pressure gage is to the left and a pressure plate is on top of the vessel.

Even if the pressure apparatus can be pressurized in a very short time, the generated heat will introduce transients that may last for a minute, maybe two, depending on pressure. Such transients appear as humps on a recorded graph, and sometimes a few oscillations may also result. Altogether, steady state may be attained within 2 or 3 minutes after mixing. Further discussion of such temperature effects is found in the end of Section V,A. 

A medium-pressure apparatus is assembled from a stainless steel bomb, standard parts, valves, unions and copper or stainless steel tubing according to Fig. 4. 

Volume of pressure apparatus including all parts 179.3 liters... 

One hundred and twenty-five grams (1.06 moles) of ethyl lactate is placed in a suitable Pyrex container which is subsequently cooled in a solid carbon dioxide-acetone bath. When the ester has been cooled below the boiling point of ammonia (Note i), 125 cc. of liquid ammonia (Note 2) is added. The mixture is then placed in a specially constructed steel pressure apparatus (Note 3) and permitted to come to room temperature. After twenty-four hours (Note 4) the excess of ammonia is allowed to escape slowly through the gas outlet of the bomb. The last traces of ammonia are removed under reduced pressure. The reaction product is stirred with 200 cc. of absolute ether to dissolve. unchanged ester and alcohol. The residue is filtered, washed with ether, and air-dried. The yield of lactamide melting at 74-75° amounts to 65-70 g. (70-74 per cent of the theoretical amount) (Note 5). 

Special constructions use also ultrasonic signal devices to measure values for the height of fluids or solids in high-pressure apparatus. 

The basic elements of a prototype pressurization apparatus are a high-pressure steel cell for the sample to be treated, a high-pressure generating system, a temperature controller, and a loading system for the material to be treated [28]. 

Then, in the Fourth Chapter the design and construction of high pressure equipment is considered, with reference to research and pilot units, and production plants as well. This is a very important part of the book, as it clearly shows that running high pressure apparatus is neither difficult nor hazardous, provided some well established criteria are followed both during design and operation. 

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