Boron deposits

Nickel barium titanium primrose priderite, formula and DCMA number, 7 347t Nickel-based alloys, properties of, 77 848t Nickel-base superalloys, 77 103 Nickel battery technology, 77 111 Nickel-beryllium alloys, 3 656-659 Nickel-boron deposition, 9 693-695, 708 Nickel brass, corrosion, 7 812 Nickel bromide, 77 110... 

The deposition of boron is then started by elevating the temperature of the reactor Q to 700°C. and of the evaporator V to 40°C. (Pbbd = 130 mm. Hg). To trap and recycle BBr, the condenser C is cooled to — 40°C. The flow rate of hydrogen is adjusted to 200 ml./minute. The boron deposits in the form of dendritic granules. The furnace F is displaced periodically from right to left so that the boron already deposited acts as a nucleus for the new deposit. If the boron remains in the hot zone for more than 15 hours at 700°C., the product will be contaminated with small quantities of /3-rhombohedral boron. ... 

Parametric Study. A study of the effect of process parameters on the deposition of boron using the static filament apparatus was conducted. The parameters studied include system pressure, reactant gas flow, ratios, electrode separation, and configurations, and field strengths. The evaluation of certain parameters has been quantitative and was based on the weight of boron deposited or on the thickness of the deposit at the midpoint of the filament. Other parameters were evaluated by a qualitative description of the deposit. 

Mechanism of Deposition. The results obtained indicate that the mechanism of boron deposition in a corona discharge is cathodic. In this type of system, electrons are generated and repelled from the cathode while positive ions are drawn to it. At the anode, positive ions are generated, or electrons are drawn to it. Thus, the boron radical is positively charged and drawn to the cathode where it is deposited as elemental boron. 

Figure 4. Boron deposit on 0.5-mil tungsten wire, Run No. 35-1 (27OX)...

Boron deposited on wire etched to an orange peel finish gives a coating similar to that pictured in Figure 6. 

Examination of boron deposited on variously etched wire indicates that the coating morphology and growth structure are directly dependent upon the morphology of the substrate. 

The results obtained indicate that the best process conditions and plating procedure for boron deposition on a stationary 0.5-mil tungsten wire are as indicated in Figure 7. 

Experimental. Figure 8 is a schematic of the apparatus designed, assembled, and tested for continuous boron deposition on a moving Ala-... 

Boron is a dark brown element that is widespread in the environment but occurs naturally only in combined form, usually as borax, colemanite (Ca2B60n 5H20),boronatrocal-cite (CaB40yNaB02 8H2O), and boracite (MgyCbBieOso). In the United States, boron deposits in the form of borax are concentrated in the desert areas of southern California, especially near Boron, California. Proven deposits of sodium tetraborates - from which borax is prepared and from which boron can be isolated - also exist in Nevada, Oregon, Turkey, Russia, and China. About 300,000 metric tons of boron are removed from mined ore each year. The United States supplies about 70% of the world boron demand, and Turkey supplies 18% the most common commercial compounds are boric acid and borax. 

It has to be remembered that boric acid may precipitate from the solution as various kinds of deposits (crud) which form on the inside primary system surfaces and especially on the hot surfaces of the fuel elements. Subsequently, in case of thermal or hydraulic transients, some of these deposits may peel off from the core giving rise to a reactivity transient. Over the years, no accidents due to this phenomenon have happened, notwithstanding the fact that the boron deposition on core surfaces has been observed and studied. The maximum reactivity which could be released can be evaluated of the order of 0.1 per cent in half a second (Petrangeli, 1967). 

Later work by FMI workers, Brewster, Nelson and Patton [134], showed that the boron deposits were confined to a surface layer on the fibers about 15mn thick, strengthening the fibers by healing surface defects such as holes and cracks. 

Boron fiber n. An advanced reinforcing fiber produced by passing 10-pm, resistively heated tungsten wire through an atmosphere of boron trichloride and hydrogen. Hydrogen reduces the BCI3 and the boron deposits on the wire to make a filament from 120 to 140 pm in diameter. Density... 

There are hints that the structure of amorphous boron deposited by evaporation on surfaces at lower temperatures are essentially different from those in thermal equilibrium (see Ref. 38 and compare with Ref. 34). 

The thicknesses of the films on the sapphire substrates were measured with a multiple-beam interferometer and ranged from 442 to 4740 A. In the case of the films deposited on tantalum, the film thickness could not be measured optically because of the rough surface of the tantalum substrate. The thickness of boron films on tantalum subsfrates was estimated from the measured X-ray fluorescence of boron deposited using electron probe microanalysis (EPMA) with a 7-kV acceleration voltage, a 0.1-pA sample current, and a 100-pm beam diameter. The relation between the X-ray intensity and the film thickness was previously obtained using boron films on a sapphire substrate. 

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