Mechanical alloying method is an effective method to compound fine crystalline alloy powder material. For example, titanium aluminum alloys was required to use this method to form crystals, its most important feature is easier to obtain nano-crystalline organization, but its compactness is not good and its forming is more difficult, besides, the rapid cooling method can not get titanium aluminum alloy products.

Tungsten contacts prepared by mechanical alloying method have the following features:

1. With dispersion strengthening phase and fine, uniform microstructure;
2. The production process is simpler and more economical;
3. Improve the electrical and mechanical properties of tungsten contacts;
4. Prepare supersaturated solid solution, so immiscible tungsten contact material can be an alloying system;
5. Prepare nano contact materials with good performance;
6. Prepare refractory metal, metal oxide-based and other series of contact materials.



 

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For their approved use in scintillating applications, solid-state optoelectronic devices, lasers and optical fibers-like components, scheelite-type photonic crystals have attracted much interest and materials like scheelite CaWO4 have been synthesized in the last years by a diversity of methods including Pechini, polymeric precursor, co-precipitation, solvothermal, Czochralski, and microemulsion-mediated hydrothermal. However, scheelites obtained by these routes show serious problems like off-stoichiometry in any case and undesirable optical quality and scintillating properties in single crystals.

In this work, powders and single crystal minirods of scheelite CaWO4 were obtained by the methods of solid state reaction and laser heated pedestal growth, respectively, and an investigation has been made of their composition, scintillating and optical properties as revealed by X-ray diffraction (XRD), radioluminescence (RL) and optical absorption (OA) measurements.

We have found single phase CaWO4 in both as-obtained powders and single crystals, and wellbehaved optical and scintillating properties. Enhanced scintillating properties in single crystal samples were evidenced, with single or double RL peaks between 400 nm and 500 nm, with sources of β-ray or X-ray, respectively. Also, a decrease of the RL light yield with the temperature increase was observed in all the samples. A shift of the RL peak was also observed with the temperature increase.

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The interest in CaWO₄ and CaMoO₄ has been driven by the fact that these compounds have especially attractive properties for a variety of optical applications (phosphors, laser hosts, scintillators). Recently, CaWO₄ was implemented in the CRESST dark matter search, enabling discrimination between electron and nuclei recoils. Different types of interaction events can be identified by simultaneously measuring a combination of phonon and scintillation signals from cryogenic phonon-scintillation detectors (CPSD) operating at milli-kelvin temperatures. This technique offers high sensitivity and the unique advantage of background identification, which is crucially important for experimental searches for rare events.

 

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Powders and high optical quality single crystal minirods of stoichiometric scheelite CaWO4 have been prepared by solid state reaction and floating zone methods, respectively, and their single phase formation, optical and scintillating properties have been evaluated by X-ray diffraction, optical absorption and radioluminescence measurements. All obtained results indicate that every sample is stoichiometric, while scintillation measurements reveal radioluminescence peaks at about 420 nm, 440 nm and 490 nm depending on the source of irradiation used. The single crystal samples exhibit higher radioluminescence light yield.

Tungsten Powder Manufacturer & Supplier: Chinatungsten Online - www.tungsten-powder.com
Tel.: 86 592 5129696; Fax: 86 592 5129797
Email: sales@chinatungsten.com
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