Cementation process

In ancient India, a steel called wootz was made by placing very pure kon ore and wood or other carbonaceous material in a tightly sealed pot or cmcible heated to high temperature for a considerable time. Some of the carbon in the cmcible reduced the kon ore to metallic kon, which absorbed any excess carbon. The resulting kon—carbon alloy was an excellent grade of steel. In a similar way, pieces of low carbon wrought kon were placed in a pot along with a form of carbon and melted to make a fine steel. A variation of this method, in which bars that had been carburized by the cementation process were melted in a sealed pot to make steel of the best quaUty, became known as the cmcible process. 

Before the invention of the Bessemer process for steelmaking in 1856, only the cementation and cmcible processes were of any industrial importance. Although both of the latter processes had been known in the ancient world, thek practice seems to have been abandoned in Europe before the Middle Ages. The cementation process was revived in Belgium around 1600, whereas the cmcible process was rediscovered in the British Isles in 1740. 

Both processes were practiced in secret for some time after thek revival, and Httie is known of thek early history. The cementation process flourished in the United Kingdom during the eighteenth and nineteenth centuries and continued to be used to a limited extent into the early part of the twentieth century. 

F71 Fume/Vapor G01 Cement Processes (including Silicates)... 

Applicability Self-cementing processes require large amounts of calcium sulfate and calcium sulfite and are appropriate for immobilizing heavy metals. 

Zement-kalk, m. hydraulic lime, -kalkmdrtel, m. lime-and-oement mortar, -kalkstein, m. hydraulic limestone, -kohle, /. cementation carbon, -kufe, -kiipe, /. cement (or concrete) vat. -kupfer, m. cement copper, -mastiz, m. mastic cement, -metoll, n. metal precipitated by the cementation process. -miUk, /. thin cetnent mortar. 

Stratigraphic traps are formed by depositional and sedimentary factors. In such traps the depositional process and the follow-on cementing process, which changes the sediment bed into a rock, create porosity and permeability alterations in geometric forms that provide traps. 

The cementation process starts with a large difference of the equilibrium potentials [e.g., Cu2+/Cu(Hg) and Zn2+/Zn(Hg)] and will arrest when the potentials of both systems are equal, i.e., when (at 298 K) 85 88)... 

This value does not express the actual result since side and/or parallel reactions (e.g., H+ or 02 reduction) are not considered, but it does demonstrate the completeness of the cementation process and the effectiveness of this liquid-liquid extraction. During this extraction no external current flows through the phase boundary Hg (amalgam)/solution thereby establishing a potentiometric condition. The question of the potential difference at the phase boundary can be answered by constructing the experimentally accessible current-voltage curves for the reactions ... 

Static experiments with pistonlike filtering can be reliable, however, to obtain information on the fluid loss behavior in certain stages of a cementation process, in particular when the slurry is at rest. 

J. Kieffer, M. Michaux, and P. Rae. Additive for controlling the filtrate of well cementing slurries and corresponding cementing process (ad-ditif pour le controle du filtrat des laitiers de cimentation de puits, et procede de cimentation correspondant). Patent FR 2592056,1987. 

The process of precipitation of a metal from an aqueous solution of its salt by another metal is the well-known cementation process, so named because the precipitated metal is usually cemented on the metal introduced into the system. The process prediction stems from consideration of electrode potentials of metals. The metal positioned with greater (oxidation) potential in the electromotive series will pass into solution and remove a metal positioned with a less positive potential. The larger the spread of the positions of the two metals in the series, the greater is the possibility or feasibility of cementing out one by the other. 

Portland cement process. Sand is mixed with pordand cement (10% of sand weight) and water (5% of sand weight). Molds are air dried for 24h and may then be dried out more rapidly. 

Tests have been conducted on wet and dry cement processes in the United States, Canada, Sweden, and Puerto Rico for wastes containing a wide range of chlorinated chemicals, including PCBs (13-16). Generally, the DKEs have been found to be in the range of 99.99%, with no adverse impact on product quality or plant operation if chlorine addition is restricted to less than 1% of the net fuel/waste feed. DKEs of less than 99.99% have been observed, however, where poor control of combustion air exists and waste is inadequately atomized, even when an acceptable cement product is being produced. 

Hack Diffusion. Pack diffusion or cementation processes are similar 10 pack carburizing, anil are used to coat iron, nickel, cuhali. and coppci with chromium, boron, zinc (Sheradi/ingl. aluminum, silicon, titanium, molybdenum, and other metals. 

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