Sintering kinetics in tungsten powder with and without a liquid phase

An experimental study of the sintering kinetics of tungsten powder has been made in the temperature range 1100-1600°C. The effects of particle size, compacting pressure, sintering atmosphere, sintering temperature and sintering time upon the rate of sintering were examined. 

Isothermal changes in the length, volume and density of the compacts were measured and the results were evaluated in terms of the usual degree of sintering parameter, δ , a new volume parameter, V, and by the linear shrinkage method. Of these parameters, it was found that the most reliable information was obtained by use of the volume parameter. 

It was found that the activation energy for sintering tungsten powder was 102 ± 2 kcal/mole which is consistent with a mechanism which involves grain boundary diffusion. The increase in fine particle size of the tungsten powder increases the sintering rate. 

The kinetics of isothermal grain growth during sintering were also examined in the temperature range 1100 to 1650°C. No grain growth was observed at temperatures below 1400°C,however, above this temperature the grain diameter increased at a rate proportional to sintering time, t 1/3. The activation energy of 94 kcal/mole obtained for this process is in reasonable agreement with that derived for densification. 

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Potassium Tungstate CAS No 7790-60-5

Application / Uses Preparation
This salt is soluble in water and is a moderately strong oxidizing agent, but finds no common use in the chemistry laboratory. Like the molybdate, the deep-coloured complex tungstate(VI,V) is formed on reducing the compound with a very mild reducing agent, such as complex organic compounds.

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Calcium Tungstate CAS No 7790-75-2

Application / Uses Preparation
This salt is soluble in water and is a moderately strong oxidizing agent, but finds no common use in the chemistry laboratory. Like the molybdate, the deep-coloured complex tungstate(VI,V) is formed on reducing the compound with a very mild reducing agent, such as complex organic compounds.
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Cadmium Tungstate CAS No 7790-85-4

Application / Uses Preparation
Cadmium tungstate is the cadmium salt of tungstic acid, is a dense, chemically inert solid which is used as a scintillation crystal to detect gamma rays. It has density of 7.9 g/cm3 and melting point of 1325 °C. It is toxic if inhaled or swallowed. Its crystals are transparent, colorless, with slight yellow tint. It is odorless. Its CAS number is [7790-85-4]. It is not hygroscopic.

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Common Compounds of Tungstate WO4{2-}

Common Compounds of Tungstate WO4{2-}

Compound Name	Formula	Molar Mass (g/mol)
Sidium Tungstate Dihydrate	Na2WO4.2H2O	329.84768
Cobalt(II) Tungstate	CoWO4	306.770795
Ammonium Tungstate	(NH4)2WO4	283.91452
Ammonium Tetrathiotungstate	(NH4)2WS4	348.17692
Barium Tungstate	BaWO4	385.1646
Cesium Orthotungstate	Cs2WO4	513.6485038
Nickel(II) Orthotungstate	NiWO4	306.531
Potassium Tungstate	K2WO4	326.0342
Lithium Orthotungstate	Li2WO4	261.7196
Magnesium Tungstate	MgWO4	272.1426
Copper(II) Orthotungstate	CuWO4	311.3836
Thallium(I) Orthotungstate	Tl2WO4	656.6042
Ammonium Paratungstate Hexahydrate	(NH4)6W7O25.6H2O	1903.18744
Iron(II) Tungstate	FeWO4	303.6826
Calcium Tungstate	CaWO4	287.9156
Cadmium Tungstate	CdWO4	360.2486
Potassium Tungstate(IV)	K2W4O13	1021.5488
Sodium Metatungstate Hydrate	Na6H2W12O41.H2O	3020.02512
Zirconium Tungstate	ZrW2O8	586.899
Zinc Orthotungstate	ZnWO4	313.2176
Tungstate Ion	WO4	247.8376

 

 

 

 

 

 

 

 

 

 

 

 

 

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Zirconium Tungstate

Zirconium tungstate (Zr(WO4)2) is a metal oxide with unusual properties. The phase formed at ambient pressure by reaction of ZrO2 and WO3 is a metastable cubic phase, which has negative thermal expansion characteristics, namely it shrinks over a wide range of temperatures when heated.[1] In contrast to most other ceramics exhibiting negative CTE (coefficient of thermal expansion), the CTE of ZrW2O8 is isotropic and has a large negative magnitude (average CTE of -7.2x10−6K−1) over a wide range of temperature (-273 °C to 777 °C).[2] A number of other phases are formed at high pressures.

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Spherical tungsten powders

Spherical tungsten powders were synthesized by (RF) argon plasma with irregular tungsten powders. The microstructure and crystallographic phases of the synthesized powders were characterized using scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The results showed that fine spherical powder composed of pure tungsten phase with favorable dispersity and its surface becomes smooth. The spheroidization efficiency of synthesized powders was almost 100 %, and the particle size distribution became narrower after spheroidization treatment. The spheroidization efficiency of the sample decreases gradually as increasing of the feeding rate. The RF plasma spheroidization of tungsten powder is an ideal route synthesis of well- spherical metallic tungsten powders which is widely used in thermal spraying and metal injection moulding process.
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How Carbide Powder is Pressed

Tungsten carbide shapes are made from a powder which is typically tungsten, carbon, cobalt and wax to bind it all together.

Carbide shapes are made three ways; pressing in a die, ”whittling” a shape from a green piece of carbide or grinding a shape from a finished piece of carbide.  See our Carbide Articles Index for more information on Carbide, and the different grades of carbide.

This is a carbide press.  At top is a ram.  The powder is poured into the press cavity (the die) then the ram comes down and compresses the powder.  Once the powder is fully pressed the top ram withdraws.  There is a second ram at the bottom of the cavity that comes up and pushes the part out of the cavity.

Below are two different dies (seen from the top) to press a diamond shape and a trapezoid respectively.   Next to them is a saw tip seen from the side.  Saw tips are pressed from the side.  This means you can use one die to produce many different widths of the same shape.

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Crystalline Tungsten Powder Propertities

Crystalline Tungsten Powder

Main physical properties

Appearance: bright grey with good flowability.

Apparent density (g/cm3): 7.3-8.9

Tap density (g/cm3): 9.0-10.5

FSSS (um): >30;

Screen Size(Mesh): 60~325;

Crystalline Tungsten Powder (Matrix & Spray Powders) have a number of critical uses in today’s world.  Crystalline Tungsten Powder used for infiltration in Mining Bits and other Oil and Gas applications. Crystalline Tungsten Powder is also used in a variety of other applications: lead replacement, golf club weights, show dog ear weights and more.

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Nanostructured Tungsten Oxide

Metal oxides are the key ingredients for the development of many advanced functional materials and smart devices. Nanostructuring has emerged as one of the best tools to unlock their full potential. Tungsten oxides (WO_x) are unique materials that have been rigorously studied for their chromism, photocatalysis, and sensing capabilities. However, they exhibit further important properties and functionalities that have received relatively little attention in the past. This Feature Article presents a general review of nanostructured WO_x, their properties, methods of synthesis, and a description of how they can be used in unique ways for different applications.

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NICKEL TUNGSTATE, NiWo4

This product belongs to MP Biomedicals Rare Chemical library. Most Rare Chemical products are available for immediate delivery and sold "As Is". MP Biomedicals does not collect analytical data for those products. All sales are final. However, analytical test may be performed upon custom request for bulk orders. 

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Tantalum Carbide Powder

Tantalum carbide (TaC) is an extremely hard (Mohs hardness 9-10) refractory ceramic material, commercially used in tool bits for cutting tools. The hardness is only exceeded by diamond. It is a heavy, brown powder usually processed by sintering, and an important cermet material. It is sometimes used as a fine-crystalline additive to tungsten carbide alloys. Tantalum carbide has the distinction of being the stoichiometric binary compound with the highest known melting point, at 4150 K (3880°C). The substoichiometric compound TaC0.89 has a higher melting point, near 4270 K (4000°C). It burns in air with a bright flash and only slightly soluble in acids. Has a metallic luster.


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