The biggest difference between ordinary ceramics and glass in appearance is that ceramics are opaque, while glass is transparent. However, with the development of science and technology, many up-and-coming members have emerged in the ceramic family—high-performance ceramics. Among them, one type of alumina ceramics can be as transparent as glass, and it is even harder and more heat-resistant than glass.
Have you ever seen beautiful, transparent rubies and sapphires? Rubies and sapphires both belong to corundum, whose main chemical component is alumina. Scientists use powdered alumina as raw material and sinter it to produce alumina ceramics. This new type of ceramics can withstand extremely high temperatures and will not melt or deform even when heated to 2000°C in a fire, so it can be used as a high-temperature-resistant material. Alumina ceramics also have the same transparent and hard characteristics as corundum, so it can be used as bulletproof glass for military tank viewing windows, etc. Some people also call it artificial gemstones.
In the early 21st century, many cities in China switched their street lights to high-pressure sodium lamps, whose power consumption is only one-tenth of that of ordinary incandescent lamps. However, the sodium vapor produced by high-pressure sodium lamps is corrosive to glass. Not to mention ordinary glass, even quartz glass can be severely corroded. So people thought of alumina ceramics. Using alumina ceramics to make high-pressure sodium lamps not only transmits light, but also withstands high temperatures and is not afraid of corrosion. The service life of the lamps is 20 times longer than that of ordinary incandescent lamps.
In addition to alumina ceramics, there are many hard and impact-resistant products in new ceramics. We know that the biggest drawback of traditional ceramics is its easy cracking and breaking. Ceramic engineers use some synthetic oxides to replace natural clay, or mix metal fine powder into clay and add special fibers to make it a composite ceramic. Or they heat the ceramics in a nitrogen-filled furnace during processing, which results in the firing of new ceramics that are hard and surprisingly tough. For example, the new metal ceramic materials mixed with metal fine powder are not only hard but also extremely tough, and can be used to cut steel. Some fiber-reinforced ceramics and graphite-silicon carbide composite ceramics are more wear-resistant and impact-resistant than steel, and are even used to make tank armor, which can withstand the powerful impact of fierce artillery fire. These high-performance ceramics are hundreds of times stronger than ordinary ceramics. Not only are they unbreakable, but they are also often used in high-precision and cutting-edge research and production fields as special materials, playing an increasingly important role.