Melt replenishment

Similar to EFG, an afterheater construction around the crystallisation area is used to reduce thermal stress [29]. As for EFG material, the string ribbon technology uses a small silicon melt crucible in combination with continuous melt replenishment. To overcome the limited throughput of only one ribbon per furnace, compared to 8 or 12 ribbons for EFG, two ribbons [33] and even four with new crucible design [34] can be grown simultaneously in one furnace. The ribbon is cut into 8 x 15 cm2 wafers. 

In most cases, the activator impurity must be incorporated during crystal growth. An appropriate amount of impurity element is dissolved in the molten Ge and, as crystal growth proceeds, enters the crystal at a concentration that depends on the magnitude of the distribution coefficient. For volatile impurities, eg, Zn, Cd, and Hg, special precautions must be taken to maintain a constant impurity concentration in the melt. Growth occurs either in a sealed tube to prevent escape of the impurity vapor or in a flow system in which loss caused by vaporization from the melt is replenished from an upstream reservoir. 

Although the true waxes, such as beeswax, are esters of fatty acids with alcohols, the term is often applied to certain solid substances which melt at fairly low temperatures, e.g., paraffin wax. Paraffin waxes (crystalline and microcrystalline) are obtained from the refining of petroleum, and are used in rubber compounding as protective agents. They have the property of blooming to the surface of the product, forming a thin film which replenishes itself if removed in service. 

One of the separatory funnels is filled with 1 1. of sulfuric acid prepared by the careful addition of 392 g. (4 moles) (213 cc.) of concentrated sulfuric acid to 213 cc. of water. The other separatory funnel is filled with a solution of 203 g. of commercial sodium cyanide (about 96 per cent) (4 moles) dissolved in sufficient water to make 500 cc. of solution. Evolution of hydrogen cyanide takes place on the simultaneous addition of the two solutions. Practically all of the reaction occurs in the funnel, F, and the sodium bisulfate solution continuously drains into the flask so that fresh solutions are always present. The solution in the funnel remains clear as long as sufficient sulfuric acid is present. An excess of sodium cyanide colors the solution yellow and leads to the formation of a muddy brown precipitate. By adjusting the flow of solutions the rate of evolution is easily controlled, and the preparation requires no attention beyond that involved in the occasional replenishment of the solutions in the separatory funnels. The last part of the hydrogen cyanide can be driven from the apparatus by boiling the bisulfate solution for a few minutes. The yield of acid melting at — r5° to — r4.5° is roo-ro5 g. (93-97 per cent of the theoretical amount) (Notes 3 and 4). 

Results from a quasi steady-state model (QSSM) valid for long crystals and a constant melt level (if some form of automatic replenishment of melt to the crucible exists) verified the correlation (equation 39) for the dependence of the radius on the growth rate (144) and predicted changes in the radius, the shape of the melt-crystal interface (which is a measure of radial temperature gradients in the crystal), and the axial temperature field with important control parameters like the heater temperature and the level of melt in the crucible. Processing strategies for holding the radius and solid-... 

Operators conducted the chemical reaction in an aqueous solution at about 32° F (0° C) to minimize side reactions and maintain product quality. The operating team keep the reactor temperature controlled by adding an excess of crushed ice. As the exothermic reaction melted the ice, the operators replenished the crushed ice by adding it into the system via the manway. 

Melt or solution spinning of synthetic fibers is a marvel of modern technology. Fiber lubrication, which is of the utmost importance in this high-speed process, is achieved by the application of spin finish—a combination of oils and surfactants. A typical spin line for the production of polyester staple fiber is shown schematically in Figure 2. The number of filaments, which can vary from tens to thousands, come into contact with various parts of the machinery, some of which are heated for proper fiber modification. To replenish the lost finish and to ensure adequate lubrication,... 

Fluorine is manufactured electrochemically from a salt melt, which consists of a mixture of potassium fluoride and hydrofluoric acid in a molar ratio of 1 2.0 to 1 2.2. The temperature of the salt melt is ca. 70 to 130°C. Potassium fluoride provides the necessary melt conductivity, the hydrogen fluoride consumed being continuously replenished during the electrolysis. 

In the presence of a stream of hot air or high temperature and low pressure (e.g., during polymer melt processing) volatility becomes very important it is governed by the rate of diffusion of antioxidants, which, in turn, determines the rate at which the surface is replenished. " The influence of polymer sample shape and the structure and molar mass of antioxidants on volatility has received much attention. The rate of evaporation of antioxidants from rubber and polyethylene, for example, was found to be inversely proportional to the thickness of the sample and directly proportional to its surface area. Furthermore,... 

Most antistatic additives are polar waxes the alkane chain part of the molecule is attracted to the polymer, while the hydrophilic end attracts water. This moisture forms a thin conductive film on the surface of the plastic. A charge decay half time of 0.1 s or less provides adequate protection against static electrification. To achieve this, the surface resistivity must be less than 3 x 10 fl/square. Although surface films are worn away by abrasion, they are replenished by the additive slowly diffusing to the polymer surface. They will not function adequately when the relative humidity is less than 15% (not a problem in the UK ), and cannot be used for specialised polymers with melt processing temperatures exceeding 300 °C. The use of conducting fillers (see the next section) is a more permanent solution to static electrification. 

If, to explain this, the hypothesis is put forward that the available aluminium is sufficient and the replenishment to the top soil fast enough for leaching out not to be a significant factor, it is still the case that the concentrations of aliominium in the run-off (especially in snow melt/storm surges in pond input) are unlikely to have increased since 1974 [1]. 

The anodes are consumed as the carbon reacts with the oxygen liberated by the electrolysis. The alumina needs to be replenished from time to time in the melt. The applied voltage is about 4.5 volts, but it rises sharply if the alumina concentration is too low. The electrolysis cells are connected in series, and there may be several hundred cells in an aluminum plant. The consumption of electric power amounts to about 15,000 kilowatt-hours per ton of aluminum. (A family in a home might consume 150 kilowatt-hours of power in a month.) Much of the power goes for heating and melting... 

OF2 is produced by electrochemical conversion of O2 in the electrolysis of an essentially anhydrous HF electrolyte (<0.1 wt% H2O) with added NH4F or alkali metal fluorides at 60 to 105°C. The anode had pores through which O2 was introduced [10]. Electrolysis of a melt consisting of -60% KF, -39% HF, and -1% LiF, to which was added up to 1% H2O, yields OF2. The water may be replenished by a stream of moist air [11]. In almost all cases of fluorination of oxygen-containing inorganic compounds by electrolysis in liquid HF, the initially generated gas contains OF2 (38 to 64 vol%). However, the OF2 concentration drops to zero in the course of the electrolysis [12]. 

Upon heating, the salts melt and generate carbonate (carbon trioxide) ions. These ions flow away from the cathode and towards the anode where they combine with hydrogen. This produces water, carbon dioxide and electrons. The electrons are passed through an external circuit, generating electricity and eventually returning to the cathode. At the cathode, oxygen and carbon dioxide (which has been recycled from the anode) react with the electrons to form carbonate ions that replenish the electrolyte. 

Groundwater is replenished by rainfall or after snow melt ... 

To semi-quantitatively understand the above tendency, a hydrodynamics description of the velocity of the melt film on the rotating disk anode was tried as follows. The molten electrolyte film on the rotating disk is transferred radially outward by centrifugal force. The fluid at the disk surface is replenished by continuously supplying the melt. Because of the symmetry of the system, it is convenient to write the hydrodynamic equations in terms of the cylindrical coordinates r, cp, and z, as shown in Figure 2.3.5. 

---