Nitrogen oxide is a serious air pollutant, which can cause environmental problems such as acid rain and photochemistry smog. It can also cause direct harm to human respiratory system. To win the Blue Sky Defense War, the important task is to effectively control the emission of NO_x.

Cesium tungstate (Cs₂WO₄) is a new material discovered in recent years. At present, some famous coating companies in Japan, Germany, the United States and other countries are vigorously developing transparent heat insulation coatings of cesium tungstate.

Nano tungsten-copper composites have excellent properties of tungsten and copper, and are widely used in electrode materials, electrical contact materials, electronic packaging materials and heat sink materials. However, the disadvantages of immiscible tungsten and copper elements, large melting point difference, poor wettability and low density after sintering lead to the decrease of properties and the increase of production cost of tungsten-copper composites.

Tungsten trioxide (WO₃) is an important n-type semiconductor oxide. It has many crystal structures. It has been extensively studied because of its unique physical and chemical properties. It has been applied in the fields of electrochromic, photochromic, sensing and catalysis.