Boron surfaces

After the gaseous reaction system is established, the B203 diffuses back to the nascent boron surface to form BO, just as C02 diffuses back to the carbon surface to form CO. The reaction is... 

Boron does not meet Glassman s criterion for vapor-phase combustion of the metal. Thus, the boron surface remains coated with a vitreous B203 layer and boron consumption becomes extremely slow consequently, boron is not burned efficiently in propulsion devices. 

Boron as a dopant allows silicon and carbon materials to significantly change their conductivity and thereby open up applications in particular with boron-doped diamond (sp -carbon) as mechanically and chemically robust electrode material. The range of beneficial effects of boron in boron-doped diamond as electrode materiaP has been reported. Bio-electrochemical processes like the oxidation of NADH are possible with diamond dominating the interfacial chemistry. The sp nature of the diamond allows adsorption processes to be modified, and electrode erosion to be minimised, with electroanalytical application even under extreme conditions, for example in the presence of ultrasound and for pharmaceutical components. Boron surface functional groups have been reported to be crucial for electron transfer, for example, during glucose oxidation. ... 

Diffusion profiles of acceptor dopants have a standard form and can be described by one diffusion coefficient when boron surface concentrations are low ((Vbs < 3 X 10 cm ). Diffusion profiles became more complicated with increasing boron concentration. A steep region... 

Etchants and catalysts (or solvents) of cBN also react with cBN (see Secs. II.D.2.b. and IV.A.2). They are alkaline or alkaline earth metals, their nitrides and boron nitrides, H2O, alkaline salt etchants (NaOH, LiOH, KOH, Na2C03, NaNOs), and acid etchants (HNO3 + H2O). The reaction occurs promptly at high temperatures (usually above 1300-1400°C at high pressures). As described in Sec. II.D.2.b, some base etchants appear to react more rapidly with (111) nitrogen surfaces of cBN crystals and acid etchants with (111) boron surfaces. 

Boron trifluoride has been used in mixtures to prepare boride surfaces on steel (qv) and other metals, and as a lubricant for casting steel (see... 

Adberabibty of the film may be enhanced by its treatment with flame, electric discharge, boron trifluoride gas, activated gas plasma, dichromate sulfuric acid, and a solution of alkab metal ia Hquid ammonia (84—87). A coating of polyurethane, an alkyl polymethacrylate, or a chlotinated adhesive can be apphed to PVF surfaces to enhance adhesion (80,88,89). 

A thin layer of dark green beryl had been grown by a hydrothermal technique over the surface of a pale beryl to imitate emerald. It has been suggested that such stones should be called synthetic emerald-beryl doublets (16). The abiHty to grow thin, but not thick, single-crystal diamond on the surface of natural diamond (17) leads to the possibiHty of growing such a thin film colored blue with boron this has been done experimentally (18). 

Hydrazine—borane compounds are made by the reaction of sodium borohydride and a hydrazine salt in THF (23,24). The mono-(N2H4 BH ) and di-(N2H4 2BH2) adducts are obtained, depending on the reaction conditions. These compounds have been suggested as rocket fuels (25) and for chemical deposition of nickel—boron alloys on nonmetallic surfaces (see Metallic COATINGS) (26). 

In the case of the fibrous laminate not much work has been done, but it has been observed that a significant loss of stiffness in boron—aluminum laminate occurs when cycled in tension—tension (43,44). Also, in a manner similar to that in the laminated PMCs, the ply stacking sequence affects the fatigue behavior. For example, 90° surface pHes in a 90°/0° sequence develop damage more rapidly than 0° pHes. In the case of laminates made out of metallic sheets, eg, stainless steel and aluminum, further enhanced resistance against fatigue crack propagation than either one of the components in isolation has been observed (45). 

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