boride ceramics, An Introduction to Ultra High-Temperature Ceramics
Borides. Boride ceramics offer an unusual combination of ceramic-like properties including high melting temperature (>3000°C), elastic modulus ( Glass Ceramics
Often, the borides are combined with other refractory phases such as SiC or MoSi2 to improve the strength and oxidation resistance.5 Traditionally, borides and boride-based particulate composites have been densified by hot pressing at temperatures of 2000°C or higher.
More recently, additives such as C, B4C, and MoSi2 have been used to devise pressureless sintering methods that allow near-net-shape forming of diboride ceramics.6,7 The keys to pressureless densification appear to be the use of starting particles with high purity and an average size of 2 µm or less combined with additives to react with and remove oxide impurities present on the surfaces of powder particles.
Image showing rectangular and circular plates prepared by pressureless sintering of ZrB2 powders.
The room temperature flexure strengths for ZrB2 and HfB2 ceramics are typically in the range of 300 to 500 MPa.
When second phases such as SiC or MoSi2 are present in volume fractions of 10% or higher, room strengths in the range of 800 MPa to 1000 MPa or higher have been reported.8,9 Because the proposed applications will expose these ceramics to temperatures of 2000°C or above, one of the key issues with boride ceramics is the retention of strength at elevated temperatures.
As temperature increases to ~1000°C, the strength of fine-grained boride ceramics (including those containing particulate reinforcements such as SiC or MoSi2) tends to increase slightly.
However, as temperatures reach the range of 1000°C to 1200°C, strength typically decreases dramatically, often falling by 50% or more.
One of the few reports that have shown strength retention to temperatures as high as 1500°C involved spark plasma sintering of a HfB2-based ceramic.10 Further research is needed to understand the strength and other elevated temperature properties of boride ceramics.
Compared to borides, carbide ceramics tend to have higher melting temperatures (typically 200°C or higher than the corresponding boride) and lower values of thermal and electrical conductivities (electrical conductivity for ZrC is 106 S/m compared to 107 S/m for ZrB2).11 In particular, TaC is thought to have the highest melting temperature of any material at 3997°C.
Carbides tend to have lower oxidation resistance at intermediate temperatures due to the formation of CO gas as one of the oxidation products.12 However, carbide ceramics such as TaC have shown promise for use in environments that include a combination of ultra-high temperature, reactive phases, and erosion such as throats for solid rocket nozzles.
Carbides are typically used as nominally single-phase ceramics to maximize the melting temperatures by avoiding reactions, solution formation, or the formation of eutectics.
The high melting temperatures combined with low self-diffusion coefficients make densification of carbides difficult, or in some cases impossible, using conventional hot pressing of commercially available powders.
A further impediment to densification is the apparent overlap of the temperature regimes in which densification and grain coarsening occur, which can lead to the formation of porosity entrapped within individual grains in polycrystalline ceramics.13 The result is that some carbides reach what appears to be a limiting density where further increases in temperature can, in some cases, actually lead to a decrease in the relative density of the resulting ceramic.
The development of ultra-high temperature ceramics for aerospace applications continues around the globe.
While significant progress has been made in recent years in understanding fundamental microstructure-processing-property relationships in these materials, further work is needed to develop UHTCs for applications such as sharp leading edges for hypersonic aerospace vehicles and propulsion components for rocket motors.
Development is likely to be driven by "market pull" based on applications where performance requirements necessitate the use of ceramics due to some combination of temperature requirements, weight savings compared to heavier refractory metals, or use of simpler passive designs as opposed to more complex actively cooled components.
Boride Ceramic Evaporation Materials
Boride ceramic materials include Hafnium Boride (HfB2), Aluminum Boron (AlB2), Tantalum Boride (TaB2), Cerium Boride (CeB6), Chromium Boride (CrB2), Magnesium Boride (MgB2), Molybdenum Boride (Mo2B5), Nickel boride (Ni2B), Lanthanum Boride (LaB6), Zirconium Boride (ZrB2), Titanium Boride (TiB2) and Iron Boride (Feb).
Stanford Advanced Materials supplies a variety of high quality elemental and composite evaporation materials in a full range of purities and dimensions to suit any customer needs.
We can supply by the gram, kilogram, troy ounce, pound, pellet and spool in any of our available purities.
SAM can customize Boride ceramic targets with specific chemical compositions and geometric sizes.
Boride is a compound between boron and a less electronegative element.
Boride ceramic powders
Due to their hardness, chemical, and thermal resistance, borides are materials meeting the highest demands.
They are used, for example, in high-temperature furnaces, turbine blades, and armor plates.
The most significant boride is titanium boride (TiB2), which is characterized by its high hardness, high melting point at over 3.200 ° C, and its electrical conductivity;
it is used for the production of evaporation boats.
A number of various borides can be produced and be supplied to different industries.
Hot-pressed composites of excellent electrical conductivity, e.g.
evaporation boats (TiB2-BN or TiB2-BN-AlN) for continuous aluminum metalizing
Crucible material for non-ferrous metals (Al, Cu, Mg, Zn, etc.)
Ceramic shapes to be used in the production of Al in Hall-Héroult cells
Hot-pressed TiB2 armor plates
Cutting tools and cermets, used for machining aluminum
Metal Matrix composites (MMCs)
Other grades, i.e. coarse and fine powders are available upon request.
CERAMIC SUPER STONES
The Ceramic Super Stone is used for fine detail polishing. Extremely strong and thin for tight ribs and slots.
Excellent stone for EDM removal.
Perfect for polishing ribs, hard-to-reach slots, and sidewalls.
Our Ceramics are offered in approximate Particle Size:50nm, 1um, 1-3um, 10-40um, -100+325mesh
Fabrication of new zirconium boride ceramics
Low, I.M., McPherson, R. Fabrication of new zirconium boride ceramics. J Mater Sci Lett 8, 1281–1284 (1989).
I. M. Low Present address: Department of Materials Engineering, Curtin University of Technology, GPO Box U 1987, 6001, Perth, Western Australia
Affiliations Department of Chemical and Materials Engineering, University of Auckland, Private Bag, Auckland, New Zealand
I. M. LowDepartment of Materials Engineering, Monash University, 3168, Clayton, Victoria, Australia R. McPherson
Three borides of zirconium have been reported: ZrB,1 ZrB2,2,3, and ZrB12.4 The phase relationships, range of stability, and some physical properties of these compounds are described.
The effect of boron and zirconium on the microstructure and tensile properties of Nimonic 105 superalloy.
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