Titanium Diboride Powder Research Articles

Densification of titanium diboride by hot isostatic pressing and production of near-net-shape components

Hot isostatic pressing (HIP) was applied to the production of titanium diboride (TiB2) parts. Cylinders were first produced to select the best starting powder (of two possible choices) and the processing conditions. Transverse strength, hardness, and toughness measurements were carried out on the densified products. Results were equivalent or better than data published in the literature, showing that HIP is an efficient method of processing ceramic powders. Constitutive equations representing the rheology of porous materials are presented and applied to the selected titanium diboride powder. Hot pressing and sinter forging tests were carried out to obtain the parameters of the constitutive equations. These equations were used in a finite-element program to simulate the forming of TiB2 crucibles by HIP. These parts were actually processed using graphite or titanium inserts to produce a hollow, cylindrical part with a closed end. Observed and calculated final shapes were compared, showing good agreement. In addition, the finite-element program allowed the calculation of residual stresses after processing, of eventual remaining porosity. It then became possible to optimize processing routes, can, and insert geometries.

Milling Effect and Contamination of Titanium Diboride Powder Using WC-Co Ball-mill

Milling effect and contamination of titanium diboride powder by centrifugal-type ball-milling carried out in a WC-Co pot, with WC-Co balls were examined. The average particle-size of the as-recieved powder with 6μm decreased to 2.5μm by ball-milling for 3 hr. However, the contamination quantities of WC, Co and O2 remarkably increased with the lapse of the milling times.

Continuous Production of Titanium Diboride Powder

Continuous Production of Titanium Diboride Powder

Laser-induced vapour-phase syntheses of boron and titanium diboride powders

Small diameter boron and titanium diboride powders were synthesized from vapour phase reactants heated with infrared radiation from a CO2 laser. Boron powders were synthesized from BCI3 + H2 gas mixtures undfrom B2H6. TiCl4 + B2H6 gas mixtures yielded TiB2 powder. BCI3 + H2 + TiCl4 gas mixtures yielded TiCl2 powder but no TiB2. Novel equipment designed to vapourize TiCI4 liquid is described, Detailed characterizations of the product powders are presented.

Specific surface area studies of shock-modified inorganic powders

Modification of inorganic powders with high-pressure shock-wave loading is of interest for shock-activated sintering, material synthesis, shock-enhanced catalytic activity, dynamic compaction, and shock-enhanced solid-state reactivity. The specific surface area of shock-modified powders is a direct quantitative measure of powder morphology changes, yet few studies have been carried out on powders subjected to controlled shock-loading conditions. In the present work aluminium oxide, zinc oxide, aluminium nitride, titanium carbide and titanium diboride powder compacts were subjected to controlled shock-loading to peak pressures of from 4 to 27 GPa at various starting densities, and characterized with specific surface area measurements by the BET (gas adsorption) method. Low-temperature cyclical thermal pretreatment and outgassing pretreatment of the shock powders at 250° C were employed; the former improves the reliability of the BET measurements, and makes the surfaces of the shock-modified powders more chemically active than those of the starting powders. Each powder shows a somewhat different response to shock-loading, ranging from a decrease in specific surface by a factor of six for zinc oxide to a 200% increase for titanium diboride. Shock-induced changes in specific surface show four characteristic behaviours as shock pressure is increased. Well-understood and controllable shock-loading conditions are found to be essential to shock-modification studies. An update on earlier measurements on rutile, zirconia and silicon nitride is also reported.

ChemInform Abstract: MECHANICAL PROPERTIES OF DENSELY SINTERED HIGH‐PURITY TITANIUM DIBORIDES IN MOLTEN ALUMINUM ENVIRONMENTS

AbstractIm Hinblick auf eine Anwendung von TiB2 für Kathoden in Hall‐Heroult‐Zellen wurden für Proben mit verschiedenen Korngrößen Festigkeiten und kritische Spannungsintensitätsfaktoren in Al bei 960‐1000°C getestet.

Mechanical Properties of Densely Sintered High‐Purity Titanium Diborides in Molten Aluminum Environments

Titanium diboride powder, produced in an arc‐plasma reactor, was pressureless‐sintered to near theoretical density to produce materials of different grain sizes. Mechanical properties in an aluminum environment at 960° to 1000°C were studied by strength vs stressing rate and KIc tests. All materials experienced liquid‐metal embrittlement in aluminum containing Fe, Si, and P impurities. During exposure, these metals penetrate TiB2 grain boundaries and the impurities preferentially segregate there. Fine‐ and coarse‐grained materials exhibited stress‐strengthening (negative N) and stress‐corrosion (positive N) slow crack growth behavior, respectively. Results were interpreted in terms of opposing slow crack growth mechanisms.

Sintering and Properties of Titanium Diboride Made from Powder Synthesized in a Plasma‐Arc Heater

The pressureless sintering to near theoretical density of high‐purity titanium diboride powder, produced in a plasma arc from halogen vapor reactants, is described. Physical and mechanical property measurements between 25° and 1400°C are reported for materials densified at T=1800° to 2275°C. Titanium diboride exhibits several unusual and interesting properties, which include high electronic conductivity, a large positive strength‐vs‐temperature coefficient, and an intrinsic resistance to high‐temperature slow crack growth (negative N) Property trends are explained in terms of microstructural development and residual grain‐boundary stresses.

Hydrostatic pressing of a mixture of titanium diboride and titanium carbide powders

1. The process of hydrostatic pressing of a titanium diboride + 20% titanium carbide powder mixture is described by a logarithmic dependence of its relative volume on pressing pressure. The pressing of parts should be performed under pressures below 3000 kgf/cm2 in order to prevent the appearance of overpressing cracks. The optimum pressing pressure is 1500 kgf/cm2, which gives rise to the least elastic aftereffect. 2. By subjecting the mixture to vacuum treatment before pressing it is possible to increase the density of compacts by 1.5% in the pressure range 1500–2500 kgf/cm2 and decrease the probability of stratification. 3. Holding under a pressure of 2000 kgf/cm2 for 1–3 min enables the density of compacts to be increased by 1.5%. 4. High-temperature sintering leads to a marked increase in density, by 25–28%; sintered specimens have a residual porosity of 2–5%. 5. Hydrostatic pressing enables large-sized parts of complex three-dimensional shape with an even density distribution to be produced from titanium diboride powder with 20% titanium carbide.

Effects of particle size on the sintering of titanium diboride powder containing a 20 % titanium carbide addition

Effects of particle size on the sintering of titanium diboride powder containing a 20 % titanium carbide addition