Aluminum Boride Research Articles

Properties of high-temperature solution-grown aluminium borides

The laws of crystal growth in the Al-B-C system in the temperature range 2023-1073 K are analysed, and data are given on the properties of the crystals. The crystals are divided into three groups on the basis of their appearance: 1. (1) AlB 2 with hexagonal symmetry, 2. (2) amber crystals with tetragonal symmetry and 3. (3) black crystals with tetragonal and orthorhombic symmetry. The Knoop hardness of the (111) face of the amber crystals is 26.5 GPa, that of the (100) face of the black crystals is 22.9 GPa under a load of 2 N. The (100) faces of the amber crystals and those of the black ones exhibit a fracture toughness of 5.3 MPa m 1 2 and 2.2 MPa m 1 2 , respectively. The amber and the black crystals are p-type semiconductors. The activation energy of electrical conductivity in the temperature range 200–400 K is 1 eV for the amber crystals and 0.1 eV for the black ones. The failure load as a function of crystal size is defined under static load; thermal conductivity of the amber and the black crystals at 310 K is estimated to be 19.6 W m −1K −1 and 38.7 W m −1 K −1, respectively.

Application of pattern recognition methods in secondary ion mass spectrometry

Pattern recognition methods were applied to SIMS spectra of aluminum and manganese borides to test if proper feature selection and distinction between the various compounds on the basis of the evaluation of cluster ions is possible. It was found that the features selected on an empirical basis could be reduced for practical application from 13 and 11 to 2–3 and 5–8 for aluminum borides and manganese borides, respectively, and that identification of the different compounds is possible by evaluation of the fragmentation pattern. Furthermore, there is evidence that this approach does not only work for pure compounds but also for specimens, where the interesting species is only a minor fraction in the analysed volume.

Products of interaction in contact of molten aluminum with boron fibers with a B4C coating

1. On the boron fiber with a B4C barrier coating-molten aluminum interface there are formed the products of their interaction, which are Al4C3 aluminum carbide and AlB2 and AlB12 aluminum borides. 2. The formation of the phases occurs as the result of solution of the coating material, which leads to failure of the B4C coating in long contact of the fiber with the molten aluminum. 3. Softening of the boron fiber in contact of the molten aluminum occurs primarily as the result of formation of aluminum borides on the interphase boundary.

Features of the interaction of boron with molten aluminum

1. In the reaction of solution of boron in molten aluminum during chemical interaction of boron fibers with molten aluminum, the properties of the fibers improve while in the reaction with the formation of aluminum borides they become poorer. 2. In liquid phase metallization of boron fibers at the aluminum coating-boron fiber interface the following phases are formed: a solid solution of boron in aluminum, AlB2 diboride, and the α-and β-modifications of AlB12 phase. Oxides and spinels were not detected at the fiber-coating interface. 3. Application of the matrix to the fiber by the continuous-casting method makes it possible to create a continuous interface of variable composition. Depending upon the degree of chemical interaction, the composition of the interface may be varied within wide limits without significant loss of strength of the fiber itself.

ChemInform Abstract: REFINEMENT OF THE STRUCTURE OF MAGNESIUM ALUMINUM BORIDE (MGALB14)

Chemischer InformationsdienstVolume 14, Issue 43 Physical Inorganic Chemistry ChemInform Abstract: REFINEMENT OF THE STRUCTURE OF MAGNESIUM ALUMINUM BORIDE (MGALB14) I. HIGASHI, Search for more papers by this authorT. ITO, Search for more papers by this author I. HIGASHI, Search for more papers by this authorT. ITO, Search for more papers by this author First published: October 25, 1983 https://doi.org/10.1002/chin.198343006AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume14, Issue43October 25, 1983 RelatedInformation

Behavior of gases in aluminum boride

Behavior of gases in aluminum boride

Mécanisme de formation des couches borurées sur les aciers a haut carbone—I. Technique des pates

The boridisation of SAE 1095 steel by means of a paste of boron carbide and cryolite in an aqueous solution of methyl cellulose has been studied. An homogeneous boridised layer approximately 120 μm thick was obtained after 4 h treatment at 900°C. Two borides FeB and Fe 2B have been identified in this film as well as a continuum structure joining these phases to the matrix. This continuum itself is composed of three phases, namely iron silicon boride, aluminium boride and cementite in a dilute solid solution of silicon in α-iron. In the mechanism proposed the initiator of boron diffusion is ascribed to aluminium. The orientation texture along the 001 axis in the boridised layer and in the stages of formation of the transition zone has also been explained. These stages are consequent upon the saturation of the adjacent matrix in silicon. The specific volume differences between FeB and Fe 2B, and Fe 2B and the matrix cause the formation of residual compressive stresses which are responsible for both the texture orientation and some cracking in the middle of the boridised layer.

Corrosion and Electrochemical Behavior of Boron/Aluminum Composites

Abstract Electrochemical measurements in 3.5% NaCI solution at room temperature indicated that there was no galvanic interaction when virgin boron fibers were coupled to aluminum. In contrast, boron fibers, extracted from a boron/aluminum composite, containing an aluminum boride intermetallic on the surface (produced during high temperature fabrication), showed a galvanic current flow when coupled with aluminum. Therefore, galvanic corrosion would be expected between the aluminum boride intermetallic and the aluminum matrix causing preferential attack of the aluminum. Corrosion potential, galvanic current, and polarization measurements verified this conclusion.

Structural principles in refractory borides

Abstract

ESCA surface study of metal borides

Abstract To investigate metal-boron bonding, a number of typical transition metal borides have been studied using ESCA; for the sake of comparison, spectra have been obtained as well on aluminium borides as on other boron compounds. Spectra are very sensitive to surface oxidation and give a semi-quantitative appreciation of the relative oxidability of boron and metal (or metals when dealing with binary metal borides). Relevant features are discussed herein.

Interface Microstructures in Boron-Aluminum Composites

High-resolution studies of interface microstructures provide unique information on the role of interfaces in the mechanical behavior of boron-aluminum composites; some results related to diffusion kinetics, phase transformations, and bond integrity are presented below. Composite specimens were thinned for transmission electron microscopy by ion-bombardment.The degradation of boron filaments in aluminum alloys is the result of chemical interaction over distances estimated to be < 2000 A (angstroms). Figure 1a shows a representative interface microstructure in a boron-6061 aluminum composite which was degraded during diffusion bonding at 500°C, 1 hr, 4000 psi. Aluminum boride(s) formed at intermittent sites at interfaces and reduced the ultimate tensile strength to only ≲ 60% of predicted values. A comparable interface is shown in Figure lb in a composite which was fabricated at 475°C; interface reaction products did not form and mechanical properties indicated that no degradation occurred.

Grain geometry and strength of some refractory-compound powders

1. With increase in grain size, the value of mean rupturing load rises and that of specific strength falls. Arranged in order of increasing mean grain-rupturing load, the refractory compounds investigated form the following series: zirconium carbide, cubic boron nitride (BO), tungsten and aluminum borides, and silicon carbide. The results obtained may be utilized also at low machining speeds, under conditions approaching static loading. 2. The wide grain-strength range exhibited by various grades of synthetic diamond enables its high abrasive power to be utilized more fully. 3. In the grinding of titanium alloys, the least residual stresses are generated by abrasives exhibiting a relatively high microhardness, a low degree of chemical affinity for the work material, and a low grain strength.

Heats of Formation of Aluminum Diboride and α-Aluminum Dodecaboride.

The energies of combustion of AlB2 and α-AlB12 were measured in a bomb calorimeter using fluorine as the oxidant. Major problems of this investigation were the assessment of the state and distribution of impurities in the samples and the establishment of the stoichiornetry of the aluminum boride phase. We obtain -16±3 kcal mol-1 and -48±10 kcal mol-1 for the heats of formation of AlB2 and α-AlB12, respectively. The uncertainties cited are the overall experimental errors. Their magnitudes are chiefly due to uncertainties in the impurity correction applied and the uncertainties in the heats of formation of the combustion products.

On the preparation of crystalline aluminium borides by a vapour deposition process

The possibility of the formation of crystalline aluminium borides rich in boron, by a vapour-deposition process has been investigated. The gas phase contained pure AlBr 3, BCl 3 and H 2. Deposition on tungsten leads to a complex mixture of tungsten and aluminium borides. Crystals of C 4AlB 24 were deposited on a graphite surface at 1400°–1600°C, carbon being supplied at the beginning of the process by diffusion from the graphite. Subsequently, to make further crystal growth possible, a compound containing carbon was introduced into the gas phase; otherwise β-rhombohedral boron appears on the C 4AlB 24 crystals already formed. A binary compound of aluminium and boron (α-AlB 12) has been prepared at temperatures above 1600°C.

Crystal Structure of Higher Aluminium Borides

THE higher aluminium borides AlB10, AlB12 and their polymorphs are distinct from other higher metal borides in that the exact stoichiometric chemical formulae of the former are accompanied by an anomalous number of formula units per crystallographic unit cell. Despite extensive efforts, the crystal structure of none of the higher aluminium borides has so far been solved.

Preparation and properties of aluminum borides

Preparation and properties of aluminum borides

Presence of Carbon in Aluminum Borides

Abstract : The effect of carbon on the formation of the reported phases in the aluminum-boron system was investigated. The results indicate that there are only three pure binary aluminum borides, AlB2, alpha AlB12, and gamma AlB12. The phase referred to in the literature as beta AlB12 was found to correspond to a stoichiometry C Al2B32. The phase referred to in the literature as AlB10 was found to correspond to stoichiometry C4AlB24. Both ternary, Al-B-C, phases have an integral number of formula units per crystallographic unit cell. A new ternary phase corresponding to the formula Al4C4B1-3 has been discovered. A method for preparation of crystals of each phase is described. (Author)

AlB10, a new phase, and a critique on the aluminum borides

AlB₁₀, a new phase, and a critique on the aluminum borides