High density tungsten alloy has excellent mechanical property, anti burning property and absorption ability to radiation. Therefore, it is used in explosive parts such as armor piercing bomb. Normally, the part should keep well after impacted by the front end explosion, but in the test, the component breaks without external force.

Tungsten carbide (chemical formula WC) is the compound made up of tungsten and carbon, following will show the preparation procedure. The molecular formula is WC and the molecular weight is 195.85, which is black hexagonal crystal with metallic luster and has similar hardness to diamond. It is a good conductor of electricity and heat.

Molybdenum carbide (chemical formula MoC) has the characteristics of high melting point, hardness, good thermal, fine mechanical stability and excellent corrosion resistance.

With the development of chemical engineering technology, there are a series of synthesis methods used to produce nanometer scale pure molybdenum carbide (chemical formula MoC) , the followings are five common preparation methods:

Impurity elements in tungsten alloys include H, O, C, N, P, S, and Si. Because these elements have small atomic radii, and strong diffusivity in alloys, they are more likely to be in the grain boundaries and phases. Segregation occurs in places with higher energy such as the boundary, and the increase in value generates brittle phases, thereby reducing the performance of the alloy and influence tungsten alloys properties.

Tungsten electrodes tip shapes can be flat, sharpened or rounded. Flat tip is cut by grinding wheel, molybdenum wire or machining. Sharpening is much more difficult. And both shapes and welding current will influence the life time of electrodes.

During the process of nanostructured WO3 synthesis it is found that citric acid content, system pH value before hydrothermal synthesis, hydrothermal reaction temperature and hydrothermal reaction time will have great influence on the product, therefore the following will focus on several influence factors affecting the phase and morphology of nanostructured WO3.

Liquid phase method is the most widely used method among many methods for synthesizing nano tungsten trioxide. Its advantage is that the nano structured WO3 particles are fine and evenly distributed, the content of the chemical components can be precisely controlled, the morphology of the nanostructured WO3 can be controlled by adjusting the morphology control agent, the synthetic process is simple, economical and good to mass production. There are four main methods including hydrothermal synthesis, sol-gel method, precipitation method and microemulsion method.

This article will discuss the gas sensitivity of nano plate shaped tungsten trioxide gas sensor at different concentration of ethanol gas, acetone gas, ammonia gas and formaldehyde gas in terms of temperature-sensitivity. As semiconductor material with good sensitivity to various toxic gases, nanostructured tungsten trioxide can effectively improve the sensitivity and response speed of gas sensors. The gas sensor using nanostructured tungsten trioxide as gas sensitive material can be done to make lower thickness detection of target gas, which can greatly decrease the harm of noxious gas to human health. Therefore, the research of nanostructured WO3 is good to make full use of its good semiconductor property, improve its value in the gas sensing field, and provide better semiconductor material.

For GTAW welding, tungsten electrodes are chosen for its good properties of low electric discharged powder, good welding arc, high temperature resistance, sharpening machinability and low radiation. There are many grades are suitable for the welding, difficult welding objectives and conditions, different grade is applied.