Static high pressure scale

Shortly after this time, it was discovered that Bridgman s static high-pressure scale was in error due to calibration problems, and the shock-induced 13 GPa transition became the new calibration standard.  [c.1]

The period from 1955 to 1985 will certainly be viewed as the golden age of shock-compression science. During that period the field grew from first recognition as a distinct scientific field with contributions from only a few highly innovative scientists to a many-faceted, broadly based discipline with major contributions to scientific knowledge and industrial technology. Scientists worldwide responded with vigor to the opportunity to study the properties of matter at unprecedented pressures and at unprecedented speeds. The scientific base grew to a world-wide science. As a result, our knowledge of geophysics, planetary physics, and astrophysics has been substantially improved with high pressure equation of state and polymorphic phase transformation data. Shock processes have become standard industrial methods in materials synthesis and processing. Shock-compression data have become the standard for the static high pressure scale. Elastic, viscoelastic, and viscoplastic deformation of solids at the highest of strain rates has been substantially defined. Large deformation elastic, piezoelectric, and dielectric properties have been studied. Chemical synthesis has been routinely carried out at unusually high pressures. Physical properties of solids have been studied at unusually high defect concentrations. Time resolution of measurement has been improved by perhaps 3 orders of magnitude. The technology has moved from remote sites to university laboratories. Characterizations of shock-compressed matter have been broadened and enriched with involvements of the fields of physics, electrical engineering, solid mechanics, metallurgy, geophysics, and materials science.  [c.228]

The advantages of continuous pressure filtration are clear and Indisputable, particularly with slow-settHng slurries and fairly incompressible cakes. Such filters are expensive, both to install and to mn, and the most likely appHcations are either in large-scale processing of products that require thermal drying after the filtration stage, ie, fine coal or cement slurries in the dry process, or in small-scale processing of high value products such as in the pharmaceutical industry.  [c.405]

Scale-up is sometimes achieved by small multiples of reactors in standard chemical engineering. This is normal, and the multiples large, in the case of electrochemical cells. Because it gives reUable performance, this is an attractive form of scale-up however, it loses the cost advantage of the large reactor. Options in hydraulic and electrical connection accompany multiple cells and are shown in Eigures 5 and 6, respectively. The electrolyte may be mn in parallel from one manifold to another in a given stack of cells. Alternatively, electrolyte can flow in series. Parallel flow has the general advantages of small temperature rise, lower gas fraction problems, low pressure drop, and low conversion per pass (some reactions are optimum at a constant reactant concentration). Parallel flow has the possible disadvantages, however, of nonuniform flow distribution, large volumetric flows, low conversion per pass (keeping recycle of reactant to a minimum), and higher bypass currents. Electrical connection to the cell bank can be monopolar or bipolar. Bipolar cell connection has the advantages of fewer busbar connections, more uniform current in each cell, better matching to rectifier equipment, lower voltage losses because of fewer connections, and no problem of current distribution down a plate because of plate resistance. The bipolar arrangement has the disadvantages of hazard present with high d-c voltages, dismption of a whole bank of cells in a cell malfunction, and current losses from bypass currents in the manifolds.  [c.90]

Another major factor affecting the choice of equipment is the boiling range of the feed stock. Crude oil is made up of hydrocarbons varying in boiling point from methane to asphalt, a range of about 1500 "F. The hydrocarbons referred to as light ends (methane through butane) are so low boiling that they are gases at normal atmospheric temperature and pressure. When it is necessary to condense these materials, their boiling point is usually raised by operating the distillation unit under pressure so that available cooling water may be used. In most cases, it would be far more costly to run at lower pressures and condense the light product by means of refrigeration. At the high end of the temperature scale, there are desirable distillate fractions whose atmospheric boiling points are well above the temperature at which cracking starts (roughly 700 F). To distill these materials without cracking, their boiling points must be lowered by reducing the oil partial pressure. This is accomplished by inducing a vacuum on the system, by diluting the oil vapors with inert gas (usually steam), or by using both methods simultaneously. The stability of the stock with respect to heat determines the maximum temperature which can be employed in the distillation process. The complexity of the process is also affected by the product purity demanded by product specifications or by the  [c.213]

The effect of nucleating sources is important when attempting to scale studies with models tO full-size components. A common practice in model tests is to expose the fluid to a high static pressure prior to testing in order to drive free gas into solution. In contrast the seeding of water tunnels is considered to improve scaling particularly in high-speed propeller applications .  [c.1341]

The best known of these shock-induced transformations is the 13 GPa transition in iron. Historically, it provided perhaps the first quantitative example of the potential of the shock-compression method to study high pressure materials behavior. This transition was first discovered in shock-compression studies by Minshall and co-workers [55M03] at Los Alamos. Although the features were consistent with a phase transition, it was not observed in static high pressure work of Bridgman [56B01] in pressure measurements thought to be in the same range. The shock measurements led to reexamination of the static pressure calibration scale, which was discovered to be in error.  [c.37]

Dynamic experiments with conventional (chemical) explosives or projectiles accelerated m gas guns have achieved 1 TPa m favourable cases. Laser-driven shocks have produced higher shock pressures [34], and measurements to 75 TPa have been reported for shock waves generated during underground tests of nuclear explosives (for a recent discussion see [35])- Sample volumes in static experiments range from litres at pressures up to 10 GPa to 0.1 nl at 500 GPa. Samples for conuuercial dynamic high-pressure production of diamond powder was done on the 100 kl scale. Most samples for shock wave studies are smaller laser-driven shock wave experiments often use microlitre samples.  [c.1958]

Even though form amide was synthesized as early as 1863 by W. A. Hoffmann from ethyl formate [109-94-4] and ammonia, it only became accessible on a large scale, and thus iadustrially important, after development of high pressure production technology. In the 1990s, form amide is mainly manufactured either by direct synthesis from carbon monoxide and ammonia, or more importandy ia a two-stage process by reaction of methyl formate (from carbon monoxide and methanol) with ammonia.  [c.507]

All microorganisms require water, sources of carbon, energy, nitrogen, and minerals. Certain vitamins and growth factors are often required as well. Additionally, oxygen is necessary for all aerobic fermentations. Chemically defined or semidefined media are often used up to the seed stage of a fermentation to ensure rapid and reproducible growth. However, on a large scale, economics play a key role ia determining the components. The material cost and availabiUty, location of fermentation plant and commodity pricing are key variables. In the case of the ICI pressure cycle fermentor for single-cell proteias the whole fermentation process (4) was essentially designed around the avaHabiUty of a relatively iaexpensive and abundant raw material, ie, methanol derived from methane gas. Generally, the nutritional requirements for most conventional fermentations can be met by formulating a medium having, eg, molasses, cereal grains, starches, glucose, sucrose, and lactose as carbon sources. Com steep Hquor, soybean meal, cottonseed flour, slaughterhouse waste, fish meals, ammonia, ammonium salts, and fermentation residues often serve as the nitrogen base. Soya bean oil, lard, and cotton seed oil serve to control foam ia aerated fermentations as well as providing carbon for nutrition. Often, other more traditional defoamers such as siUcone oils and polypropylene glycol are necessary as well. Brewer s yeast is frequently used as a combination nitrogen, vitamin, and growth factor source. The overall contribution of the cost of the medium may be very high ia some commodity-type fermentations thus the producer microorganism is often selected or engiaeered to use components it traditionally would not, but which are available at a reasonable price.  [c.180]

Liquid Crystal Polyesters. These high performance, high added-value products are derived from aH-aromatic precursors and the raw materials are inevitably more expensive. 4-Hydroxybenzoic acid (HBA) and 6-hydroxy-2-naphthoic acid (HNA) are both made by the Kolbe-Schmitt carboxylation reaction (55). In this reaction the soHd potassium phenoxide is heated under pressure with carbon dioxide. A principal process improvement uses an inert hydrocarbon oil as a heat-transfer fluid (56). Using phenol and 2-naphthol, respectively, HBA and HNA are made, although reaction conditions differ. 2-Naphthol can give both the 2,3- and 2,6-isomers depending on the alkah metal and the reaction conditions (57). Other LCP comonomers are 4,4 -dihydroxybiphenyl [92-88-6] hydroquinone [123-31 -9] (HQ), terephthaUc acid, NDA, and 4-acetamidophenol [103-90-2]. The latter is used in minor amounts in certain Hquid crystal polyesteramides, eg, Vectra B [82538-13-4] (58). Hydroquinone is manufactured on a large scale, much of it for photographic chemicals and the synthesis of antioxidants (qv). There are several routes to hydroquinone (see Hydroquinone, resorcinol, and catechol). One is the alkylation of benzene or cumene with propene or 2-propanol in the Hquid phase with a zeoHte catalyst to a mixture of 1,3- and 1,4-diisopropylbenzenes (59). These are separated and air oxidized to the hydroperoxides and decomposed into acetone and either HQ or resorcinol. The acetone can be reduced to 2-propanol and recycled via the alkylation stage (60). The latest process for HQ uses the direct oxidation of phenol with hydrogen peroxide and a strongly acid catalyst, such as trifluoromethanesulfonic acid, to a mixture of HQ and catechol (61). Another process uses a special titanium zeoHte with hydrogen peroxide to achieve the same result (62).  [c.294]

Compression moulding powders based on silicone resins have been available on a small scale from manufacturers for a number of years. They consist of mixtures of a heat-resistant fibrous filler (e.g. glass fibre or asbestos) with a resin and catalyst. Non-fibrous inorganic fillers may also be included. They may be moulded, typically, at temperatures of about 160°C for 5-20 minutes using pressures of 5-2ton/in-(7-30MPa). Post-curing is necessary for several hours in order to develop the best properties. Materials currently available suffer from a short shelf life of the order of 3-6 months but have been used in the moulding of brush rings holders, switch parts and other electrical applications that need to withstand high temperatures. They are extremely expensive and are of even greater volume cost than PTFE.  [c.831]

The glycopeptide CSPs are multi-modal phases and can switch from one mobile phase to another without deleterious effects. The new polar organic mobile phase offers the advantages of broad selectivity, high efficiency, low back-pressure, short analysis time, high capacity and excellent prospects for preparative-scale separation. Whenever a racemic compound is targeted for separation, its structure can give a hint as to which mobile phase should be investigated. If the compound has two or more functional groups which are capable of interacting with the CSPs, and at least one of these functional groups is near or on the stereogenic center, the new polar organic phase is recommended to be tested first. In this context, functional groups include hydroxyl groups, halogens (I, Br, Cl, and F), nitrogen in any form (primary, secondary and tertiary), carbonyl and carboxyl groups as well as oxidized forms of sulfur and phosphorus.  [c.38]

See pages that mention the term Static high pressure scale : [c.2053]    [c.147]    [c.303]   
Solids under high-pressure shock compression - mechanics, physics, and chemistry (1992) -- [ c.37 ]