What is sapphire glass?
Although it is often called sapphire glass, it is actually not glass-it is single crystal transparent sapphire. Of course, this sapphire is artificially synthesized, and the process is similar to that of monocrystalline silicon synthesis in the semiconductor industry. The general process is to put a small piece of sapphire (seed crystal) into molten alumina, and then crystallize a large crystal like the first picture. The next step is cutting and polishing.
Therefore, the whole process will consume a lot of energy, the cost is not low, and cutting large crystals will cause a lot of waste. In the past, sapphire was not widely used because of the cost, and basically only a few high-priced products could be used.
For example, high-end watches, as well as high-strength glass in military applications. Although sapphire glass is expensive, it has some very ideal characteristics. First of all, it has high transparency and is much stronger than ordinary glass (Mohs hardness is 9, only diamonds with hardness 10 are harder than it, and the hardness of Corning Gorilla is around 7). In addition, sapphire has excellent corrosion resistance.
How to identify sapphire glass?
1) laboratory method:
Detecting sapphire glass is very similar to identifying jewelry, and the instruments and equipment used are the same. The most commonly used instrument for jewelry identification is refractometer, which can measure the refractive index of the detected object. Although sapphire watch glass is artificial, its refractive index is 1.76~ 1.77, just like natural glass. Because sapphire glass is crystal, the refractive index is very heavy, which is 0.008. When testing, you can see it clearly by rotating the polarizer on the eyepiece. Flat glass is best observed, spherical glass is not very beautiful, so refractive oil should be coated when testing. The refractive index of mineral glass is about 1.52, which is easy to distinguish from sapphire. It has no birefringence.
Another method is to use a polarizer through which all crystals can be detected.
For example, crystal is like this. Sapphire is also a crystal. When the polarizer is rotated, the light will change alternately with a period of 90 degrees. However, if you use a polarizer to check the watch glass, you must take out the whole movement and expose the watch glass. But some non-sapphire watch glasses may also have polarizing effect, because they are also made into crystals, such as crystals. (There are many watches in Japan) (2) Drip method:
Legend has it that the method of measuring sapphire glass by dripping water is to drop a small drop of water on the surface of the glass to be measured. If the water drops are obviously beaded, it is sapphire glass; If the water drops are scattered, it is not sapphire glass. Any droplet on the surface of a smooth medium will have a different liquid level, which is related to the nature and temperature of the medium and is called liquid tension.
It is also calculated by included angle, including watch oil. It is the reason why sapphire has a relatively large density and specific gravity and a relatively smooth and delicate surface. (3) Look at the product identification and the hardness of the glass:
If it is a regular brand watch, sapphire glass is usually printed on the back cover of the watch, which is expressed by English sapphire or sapphire crystal. Now even if it is a fake watch or a fake watch,
It is also common to use sapphire watches. To test the hardness of the watch glass, you can use a sharp metal object like a needle to draw the most inappropriate eye on the edge of the watch glass. It feels hard, and there is a feeling that metal objects are floating over. There are no scratches on the glass. It should be sapphire glass. What are the advantages of sapphire glass?
Since the hardness of sapphire is second only to that of diamond, technology manufacturers can achieve better hardness performance than traditional chemically strengthened glass by purifying its elements and applying them to some transparent glass panels. According to what we have learned above, the hardness of sapphire is 9, while the hardness of glass is 5. The fracture toughness of the former is 2.3MPa√m, which is almost 3 to 4 times that of ordinary glass.
Sapphire not only has extremely high hardness, but also has excellent electrical and dielectric properties. It has the characteristics of chemical corrosion resistance, high temperature resistance, good thermal conductivity, high hardness, infrared transmittance and good chemical stability. Therefore, in some industrial fields, many instruments often use it instead of other optical materials to make optical elements, infrared optical windows and so on.
In addition, sapphire glass is also widely used in infrared and far-infrared military equipment, such as night-vision infrared and far-infrared sights, night-vision cameras and other instruments and meters in satellite and space technology, as well as windows of high-power lasers, various optical prisms, optical windows, ultraviolet and infrared windows and lenses, observation ports for low-temperature experiments, and has been completely used in high-precision instruments and meters for navigation and aerospace.
Sapphire glass does have great advantages. If used in the mobile phone industry, it can greatly improve the scratch resistance of the mobile phone screen. But at present, it seems that the popularization of sapphire glass will take some time. According to professionals in the industry, sapphire glass is extremely complicated in manufacturing process, the manufacturing time is 4000 times that of ordinary glass, and the temperature requirement is much higher than that of ordinary glass. Moreover, due to the hardness of sapphire glass, the manufacturing process is also difficult. If there is a little mistake in the furnace, the cost of later cutting will increase geometrically.
Good chemical stability and the like. Therefore, in some industrial fields, many instruments often use it instead of other optical materials to make optical elements, infrared optical windows and so on. In addition, sapphire glass is also widely used in infrared and far-infrared military equipment, such as night-vision infrared and far-infrared sights, night-vision cameras and other instruments and meters in satellite and space technology, as well as windows of high-power lasers, various optical prisms, optical windows, ultraviolet and infrared windows and lenses, observation ports for low-temperature experiments, and has been completely used in high-precision instruments and meters for navigation and aerospace.
Sapphire glass does have great advantages. If used in the mobile phone industry, it can greatly improve the scratch resistance of the mobile phone screen. But at present, it seems that the popularization of sapphire glass will take some time. According to professionals in the industry, sapphire glass is extremely complicated in manufacturing process, the manufacturing time is 4000 times that of ordinary glass, and the temperature requirement is much higher than that of ordinary glass. Moreover, due to the hardness of sapphire glass, the manufacturing process is also difficult. If there is a little mistake in the furnace, the cost of later cutting will increase geometrically.