Boron mechanical properties

Lower Oxides. A number of hard, refractory suboxides have been prepared either as by-products of elemental boron production (1) or by the reaction of boron and boric acid at high temperatures and pressures (39). It appears that the various oxides represented as B O, B O, B22O2, and B23O2 may all be the same material ia varying degrees of purity. A representative crystalline substance was determined to be rhombohedral boron suboxide, B12O2, usually mixed with traces of boron or B2O3 (39). A study has been made of the mechanical properties of this material, which exhibits a hardness... 

As an illustration of the results of the measurements just described, the mechanical properties for four unidirectionally reinforced composite materials, glass-epoxy, boron-epoxy, graphite-epoxy, and Kevlar 49 -... 

Carlsson, J., and Lundstrom, T., Mechanical Properties and Surface Defects of Boron Fibers Prepared in a Closed CVD System, / Mater. ScL, 14(4) 966-974 (1979)... 

Properties. Properties of SiC fibers are shown in Table 19.2. They are similar to those of CVD boron fibers except that SiC is more refractory and less reactive than boron. CVD-SiC fibers retain much of their mechanical properties when exposed to high temperature in air up to 800°C for as long as one hour as shown in Fig. 19.3. [ 1 SiC reacts with some metals such as titanium in which case a diffusion barrier is applied to the fiber (see Sec. 2.5 below). 

M. M. S. Fakhrabadi, A. Allahverdizadeh, V. Norouzifard, B. Dadashzadeh, Effects of boron doping on mechanical properties and thermal conductivities of carbon nanotubes., Solid State Communications, vol. 152, pp. 1973-1979, 2012. 

H. Y. Song, X. W. Zha, The effects of boron doping and boron grafts on the mechanical properties of single-walled carbon nanotubes., Journal of Physics D-Applied Physics 2009,... 

Other than in polymer matrix composites, the chemical reaction between elements of constituents takes place in different ways. Reaction occurs to form a new compound(s) at the interface region in MMCs, particularly those manufactured by a molten metal infiltration process. Reaction involves transfer of atoms from one or both of the constituents to the reaction site near the interface and these transfer processes are diffusion controlled. Depending on the composite constituents, the atoms of the fiber surface diffuse through the reaction site, (for example, in the boron fiber-titanium matrix system, this causes a significant volume contraction due to void formation in the center of the fiber or at the fiber-compound interface (Blackburn et al., 1966)), or the matrix atoms diffuse through the reaction product. Continued reaction to form a new compound at the interface region is generally harmful to the mechanical properties of composites. 

Ryder, C.. Vidoz, A., Crossman, F., Camahorl, J. (1970), Mechanical properties of nitrided boron-aluminium composites, J. Composite Mater. 4, 264-272. 

McCoy, H., M.A. Kenney, C. Montgomery, A. Irwin, L. Williams, and R. Orrell. 1994. Relation of boron to the composition and mechanical properties of bone. Environ. Health Perspec. 102(Suppl. 7) 49-53. 

The catalytically functioning curing agents do not directly participate in the crosslinked network but promote reactions between epoxy groups themselves. Tertiary amines as well as boron trifluoride type complexes are effective catalytic agents. Excellent discussions of the specific curing agents, their reactivity with epoxy and their effect on epoxy mechanical properties are available in the literature 4 6I. 

The carbides and nitrides are well known for their hardness and strength, and this section will briefly compare a number of these properties with those of the pure metals. Concentration will be placed here on the first row compounds, since these constitute a complete series, and Mo and W, since these are the most commonly studied metals. As will be shown, the physical and mechanical properties of carbides and nitrides resemble those of ceramics not those of metals. Comparisons will be made with boron carbide (B4C), silicon carbide (SiC), aluminium nitride (AIN), silicon nitride (Si3N4), aluminium oxide (A1203), and diamond, as representative ceramic materials. 

Although few applications have so far been found for ceramic matrix composites, they have shown considerable promise for certain military applications, especially in the manufacture of armor for personnel protection and military vehicles. Historically, monolithic ("pure") ceramics such as aluminum oxide (Al203), boron carbide (B4C), silicon carbide (SiC), tungsten carbide (WC), and titanium diboride (TiB2) have been used as basic components of armor systems. Research has now shown that embedding some type of reinforcement, such as silicon boride (SiBg) or silicon carbide (SiC), can improve the mechanical properties of any of these ceramics. 

Baskaran, S., and Halloran, J.W. (1994), Fibrous monolithic ceramics III, Mechanical properties and oxidation behavior of the silicon carbide/boron nitride system , J. Am. Ceram. Soc., 77(5) 1249-1255. 

Trice, R.W. (1998), The Elevated Temperature Mechanical Properties of Silicon Nitride/Boron Nitride Fibrous Monoliths, PhD Thesis. University of Michigan, Ann Arbor, MI. 

There is obviously a particular need to develop materials which can function at high temperatures. Due to their strong covalent bonding, boron cluster compounds generally possess attractive mechanical properties as materials, e.g. stability under high temperature due to their high melting points (typically >2300 K), chemical stability, resistance to acidic conditions, and small compressibility. Furthermore, importantly, the B12 icosahedra compounds have also been found to have intrinsic low thermal conductivity, as will be discussed in detail in later sections, and which is desirable for thermoelectric applications. 

Spinner assemblies (l.e., stator, holder, rotor) have been constructed from three materials Kel-F, Delrin, and machinable boron nitride (BN) (14). For observation of hydrocarbon materials at ambient and low temperatures, the Kel-F assembly is used. It displays suitable mechanical properties and does not interfere with the carbon spectrum since the resonances of the carbons in the Kel-F are >10 kHz in width due to the unremoved C-F dipolar interactions. To observe fluorocarbon materials at ambient and low temperature by C-F dipolar decoupling/CP/MAS, the Delrin assembly is used since unremoved C-H dipolar interactions broaden... 

The afterglow of open-cell foams (punking) can be suppressed by the addition of flame-retardants such as boron trioxide or aluminum hydroxide. Hybrid foams with good mechanical properties and low combustibility can be produced from PF resins and polyisocyanates.104... 

Zvyagintseva A.V., Falytcheva A.Y. (1997) Physico-mechanical properties of nickel-boron coatings, Galvanotechnique and surface treatment 2 (5), 24-31. 

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