One of the challenges facing additive manufacturing is the current lack of control over the microstructure that forms during the process. Typically, the rapid cooling rates and steep thermal gradients in the melt pool encourages epitaxial columnar grain growth. In this paper the effectiveness of...

A new scandium boride has been found to exist between ScB12 and β-boron. A single phase was established at a nominal composition of [B]/[Y]=19.0–19.5. X-ray powder diffraction and electron diffraction analyses showed that the new ScB19 phase has a tetragonal system with a=b=1.02915(4) nm and c...

The structural, electronic, mechanical, thermal and transport properties of parent binary diborides viz., ScB2, TiB2, VB2, ZrB2 and newly proposed ternary Zr0.5Sc0.5B2, Zr0.5Ti0.5B2, Zr0.5V0.5B2, Ti0.5Sc0.5B2 and Ti0.5V0.5B2 ultra-high-temperature ceramics (UHTC) are discussed. This leads to the...

Niobium boride powders having NbB, NbB2 and Nb3B4 phases in various amounts and single phase NbB powders were successfully synthesized by using powder metallurgy methods from related metal oxide raw materials in the presence of a strong reducing agent. Nb2O5, B2O3 and Mg powder blends were mille...

This study reports on the consolidation of niobium boride powders by cold pressing/pressureless sintering (PS, with or without Co addition) and spark plasma sintering (SPS) techniques. Niobium boride powders (containing NbB, Nb3B4 and NbB2 phases) which were mechanochemically synthesized from Nb...

The structure and physical properties of the Zr-stabilized, nonstoichiometric molybdenum diboride superconductor are reported. Good quality material of the diboride structure type can only be obtained by partial substitution of Zr for Mo, and quenching of melts. The diboride phase is best made w...

Boron is an attractive fuel for propellants because of its high energy density. However, its combustion is inhibited by the oxide layer that covers the particles. The use of magnesium borides instead of boron was shown to promote the combustion of boron-based propellant. The combustion behavior ...

The present work reports on the comparative characterization of optical properties of hafnium and zirconium-based ultra-refractory ceramics at room and high temperature, in view of their possible use in novel solar receivers for thermal solar plants operating at higher temperatures. We show how ...

Among the non-oxide ceramics, carbides and borides such as B4C, TiB2, ZrB2, HfB2, NbB2, CrB2, LaB6, CeB6, NdB6, EuB6 posses attractive combination of high temperature properties for engineering applications. However, they are difficult to synthesize and fabricate in the form of dense bodies, bec...

The oxidation behavior of an ultra-high temperature ceramic (UHTC) based on HfB2 with 20vol% SiC and was studied following two 10 min arc-jet test cycles with nominal heat flux of 350 W cm−2, stagnation pressure of 7 kPa, and a sustained peak surface temperature of 2360 °C. Microstructure chara...

The first principles method was used to investigate the elastic, electronic properties and anisotropy of Manganese Borides (Mn-B) compounds. The convex hull of formation enthalpy implies that Mn-B compounds exhibit the structural stability at ground state. According to Born criteria, Mn-B compou...

The correlation between structural stability and mechanical properties of Hf–B compounds is systemically investigated by first-principle calculations. The convex hull indicates that the HfB2 is more stability than other Hf–B compounds at ground state. The calculated bulk modulus, shear modulus...

Zirconium and Hafnium Di-Boride are the two major material systems that are of critical importance for applications in ultra-high temperature environments where both oxidation and mechanical damage mechanisms (such as creep) are operative. Atomistic simulations of these materials at finite tempe...

To improve the anti-oxidation and ablation properties of carbon/carbon (C/C) composites, they are modified by hafnium boride (HfB2) using a two-step process of in situ reaction and thermal gradient chemical vapor infiltration. X-ray diffraction is used to monitor the composition of the samples. ...

Nanocrystalline HfB2, HfBN and multilayer HfB2/HfBN films were deposited using chemical vapor deposition. Half of the amorphous as-deposited films were subjected to annealing at 700 °C to obtain their annealed equivalent samples. Nanoindentation and nanoscratch experiments were performed to mea...

The availability of spectrally-selective, thermally stable and more efficient sunlight absorbers represents a crucial aspect for the development of solar energy technologies able to operate at elevated temperature. In this regard, the optical properties of dense HfB2, HfC, HfB2-SiC and HfB2-HfC-...

Metal boride coatings are attracting increased interest, due to the fact that they combine high hardness with good wear and corrosion resistance. These coatings are often deposited by the sputtering of hot-pressed or sintered ceramic targets. However, targets of this nature can be prone to crack...

Chromium diboride has considerable potential as a protective coating for materials exposed to wear and corrosion. A series of CrB2 coatings have been deposited on polished AISI 316L substrates by unbalanced magnetron sputter deposition at temperatures below 200°C. All of the coatings were fully...

We report 11B NMR studies of a single crystal CrB2. From the temperature dependence of the Fourier-transformed NMR spectra in the paramagnetic state, the hyperfine coupling constants are estimated to be ACr–B = −0.64,−0.74 and −0.71kOe/μB for H||c, H||a and H|| [2 1 0], respectively. In the ma...

Experimental investigations were carried out on synthesis of chromium diboride through boron carbide reduction of Cr2O3. The products obtained were characterized by X-ray diffraction and the process optimized to prepare single-phase CrB2 powder. Densification of CrB2 was investigated by pressure...