Glass is a common material in our daily lives. Ordinary glass is commonly used for windows in residential buildings. The main raw materials for ordinary glass are soda ash, limestone, and quartz sand, which are substances obtained by melting sodium silicate, calcium silicate, and silica together. When people produce ordinary glass, the raw materials are crushed, mixed in appropriate proportions, and placed in a glass kiln to strengthen the heat. After the raw materials are melted, they undergo complex physical and chemical changes.
Glass does not have a certain melting point, but gradually softens within a certain temperature range. When glass is softened, it can be made into any shape of product, and commonly used glass bottles and cups are made of ordinary glass.
By adding different substances and adjusting their chemical composition during the glass production process, glass with different properties and uses can be produced. For example, adding boron oxide to the production of ordinary glass can improve its chemical stability, reduce its coefficient of thermal expansion, and make it more resistant to high temperatures and chemical corrosion. It can be used to manufacture advanced chemical reaction containers. In addition, optical glass made by adding lead oxide has a high refractive index and can be used to manufacture eyeglass lenses as well as lenses in cameras, telescopes, and microscopes. Also, if certain metal oxides are added during the production of glass, colored glass can be made. When cobalt oxide is added, the glass will appear blue; Adding cuprous oxide will make the glass appear red. Generally, ordinary glass we see appears light green because there is a mixture of divalent iron in the raw material.
In addition, glass can undergo various process treatments. For example, ordinary glass is flipped into a tempering furnace and heated. When it approaches the softening temperature, it is quickly removed from the furnace and then blown rapidly with cold air to produce tempered glass. The mechanical strength of tempered glass is 4-6 times greater than that of ordinary glass, and it is resistant to seismic cracking and not easily broken. After tempered glass is broken, the fragments have no sharp edges and are less likely to harm people.
Color changing glass is used as window glass, which can soften the light passing through under the scorching sun. Color changing glass can also be used to make sunglasses. Color changing glass is a type of glass containing silver bromide (or silver chloride) and trace amounts of copper oxide. When the color changing glass is exposed to sunlight or ultraviolet radiation, the silver bromide in it decomposes, producing silver atoms that can attract visible light. When the silver atoms gather in a certain amount, most of the visible light shining on the glass will be absorbed. At this point, the previously colorless and transparent glass will turn gray black. Place the discolored glass in the dark, and under the catalytic action of copper oxide, silver atoms and bromine atoms will combine to form silver bromide. Because silver ions do not absorb visible light, the glass will once again become colorless and transparent, which is the basic principle of color changing glass.
Among them, the characteristic of photochromic glass is that the color and transmittance of the glass automatically change with the intensity of sunlight. High sunlight intensity, dark color of glass, and low light transmittance. On the contrary, with low sunlight intensity, the color of the glass is light and the transparency is high. Photochromic glass is generally used for building doors, windows, curtain walls, etc.