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1. An investigation was carried out into the preparation of alloys of the system zirconium diboridezirconium nitride by the hot-pressing technique. 2. It was established that the solubility of zirconium nitride in zirconium diboride is 2 mol.%, while the solubility of the diboride in the nitride is 5 mol,%.

As previously suggested, specific heat (15–250 K) and electrical resistivity (4.2–125 K) measurements show that CrB 2 is an itinerant antiferromagnet ( T N ∼85K). These results are also in agreement with the assumption of spin fluctuations in chromium diboride and its alloys.

Particulate composites of TiB2 in ZrO2, Y2O3 and Al2O3 have been prepared by vacuum hot pressing. Specimens were tested in oxyacetylene flames at 1650 to 2050°C; in vacuum at 1600°C and by induction heating in air at 1400 to 1600°C in order to evaluate the chemical compatability between the diboride/oxide combinations, as well as the effectiveness of the oxides as diffusion barriers. Results indicate that the large vapor ressure of B2O3 formed at the diboride/oxide interfaces presents serious problems under all the conditions tested.

The diborides of neptunium and plutonium and their solid solutions Np1 − xPuxB2 were synthesized by reaction between boron and actinide hydrides at 900 °C. The solid solution is observed for the whole range of composition. The variations in the lattice parameters obey Vegard's law: a = 0.31622(4) + 0.00247(5)x nm and c = 0.39720(5) − 0.00228(7)x nm. An attempt to form the plutonium monoboride at low temperature (800 °C) was made without success. The earlier reported PuB was probably the isotypic plutonium mononitride.

The possibility of using hot-compacted specimens of boron carbide and titanium diboride as materials for the indentors for measuring the hardness of tungsten carbide at high temperatures has been explored. It is shown that a titanium diboride indent or flattens at 1770°K owing to a fall in the hardness of the material at this temperature. A boron carbide indentor can be used repeatedly for measuring the hardness of tungsten carbide at temperatures up to 2170°K without any trace of chemical reaction between the material of the specimen and that of the indentor and also without failure of the latter.

The anisotropic thermal expansion of manganese diboride has been determined with neutron diffraction over the temperature range 5–298 K. The variation of lattice parameter with temperature is defined by the equations a = 3.0044 + 4.9 × 10−6 T c = 3.0358 − 2 × 10−6 T + 7 × 10−8 T2. The c parameter is found to contract initially, passing through a minimum at 14 K.

The anisotropic thermal expansion of manganese diboride was determined by neutron diffraction over the temperature range 5 to 298 deg K. The variation of lattice parameter with temperature is defined by the equations a =3.0044 + 4.9 x 10/sup -6/ T and c = 3.0358-2 x l0/sup -6/ T + 7 x l0/sup -8/ T/sup 2/. The c parameter is found to contract initially, passing through a minimum at 14 deg K. (auth)

The new compounds, vanadium(III) acetate and benzoate, have been prepared by the reaction of vanadium diboride with the appropriate anhydrous acid. The molecular weight, and infrared and proton n.m.r. spectra show that these compounds are dimeric and probably have a structure with four bridging and two terminal carboxylate groups. The magnetic properties are also described.

A new tungsten boride has been prepared and has been assigned the formula WB(2). The assignment is based on comparison of the x-ray diffraction data of this boride with those of diborides of the AlB(2) type structure. Values of a(0) = 3.02 and c(0) = 3.05 were calculated for a hexagonal unit cell.