Silicate non-metallic materials - glass


Silicate non-metallic materials - glass

Glass is an amorphous, inorganic, non-metallic material. Generally, various inorganic minerals such as quartz sand, borax, boric acid, barite, barium carbonate, limestone, feldspar, soda ash, etc. are used as the main raw material, and a small amount of auxiliary materials are added. Made from raw materials. Its main components are silicon dioxide and other oxides.

The chemical composition of ordinary glass is Na2SiO3, CaSiO3, SiO2 or Na2O CaO 6SiO2, etc. The main component is double silicate salt, which belongs to the mixture and is an amorphous solid with irregular structure.

1. Development History

The first glass makers in the world were the ancient Egyptians.

More than 3,000 years ago, a European Phoenician merchant ship was loaded with the crystalline mineral "natural soda" and sailed along the Belut River along the Mediterranean Sea. Due to the low tide on the sea, the merchant ship ran aground, so the crews landed on the shore one by one. Some crew members also brought a large pot and firewood and used a few pieces of "natural soda" as a large pot holder to cook on the beach.

The tide began to rise as the crew finished their meal. When they were about to pack up and board the ship to continue sailing, someone suddenly shouted: "Everyone, go and look, there are some crystal bright and shiny things on the sand under the pot!"

The crew took these shining things to the ship and carefully examined them. They found that some silica sand and melted natural soda were stuck to these shiny things.

It turns out that these shiny things are natural soda, which was used to make pots when they cooked. Under the influence of the flame, they chemically reacted with the quartz sand on the beach. This is the earliest glass.

Around the 4th century, the ancient Romans began to use glass for doors and windows. By 1291 glassmaking technology in Italy was highly developed.

In the 12th century AD, commercial glass appeared and was used in industry.

In 1688, a man named Neph invented a process for making large pieces of glass, and glass has been a common item ever since.

In the 18th century, optical glass was produced for the manufacture of telescopes. In 1874 flat glass was produced for the first time in Belgium. In 1906, the flat glass induction machine was produced in the United States. Since then, with the industrialization and scale of glass production, glasses with different uses and characteristics have appeared one after another.

In our time, glass has become an important material in everyday life, production, science and technology.

For hundreds of years, people believed that glass was green and could not be changed. Later, it was found that the green color comes from a small amount of iron in the raw material, and the compound is bivalentheavy iron makes the glass green. After the addition of manganese dioxide, the original ferrous iron is converted to trivalent and turns yellow, and the tetravalent manganese is reduced to trivalent manganese and turns purple. Optically, yellow and violet can complement each other to a certain extent, but when they are mixed together to form white light, the glass will have no color cast. However, after a few years, the trivalent manganese will continue to be oxidized by air, and the yellow color will gradually increase, so the window panes of those old houses will be slightly yellowish.

2. Glass production process

Silicate glass is usually made from quartz sand, soda ash, feldspar and limestone as raw materials after mixing, high temperature melting, homogenization, processing and shaping, and then annealing. Mainly include:

⒈ Pretreatment of raw materials. Grinding bulk raw materials (quartz sand, soda ash, limestone, feldspar, etc.), drying wet raw materials, and removing iron from iron-containing raw materials to ensure glass quality.

2. Preparation of batch material.

3. Melting. The glass charge is heated at high temperature (1550-1600°C) in a pool furnace or a crucible furnace to obtain a homogeneous, bubble-free water glass that meets molding requirements.

4. Formation. Processing of liquid glass into products of the required shape, such as flat plates, various dishes, etc.

5. Heat treatment. Annealing, tempering and other processes remove or create stresses, phase separation or crystallization within the glass and change the structural state of the glass.

Third, the condition of the glass

Glass is not completely solid. The glass is neither crystalline nor amorphous nor polycrystalline nor mixed. The theoretical name is the glassy state.

From a microscopic point of view, glass is also a type of liquid. Its molecules do not have long-range order in space, like crystals, but have short-range order, like liquids. Glass holds a definite shape like a solid and does not flow under gravity like a liquid.

Characteristics of glass condition at room temperature:

Short order, that is, within a few or tens of atoms, the atoms are ordered, showing crystalline characteristics;

Disorder, that is, after increasing the number of atoms, it becomes a disordered state, and its degree of disorder is similar to that of a liquid.

Macroscopically, glass is a solid.

Glass is one such substance. The reason for this glass structure is that the viscosity of the glass changes too quickly with temperature and the crystallization rate is too slow. When the temperature drops and the crystallizationAs soon as it starts, the viscosity becomes very large and the movement of the atoms is limited, which leads to this result. Therefore, the state of glass is like a solid liquid, and the atoms in matter are always in the process of crystallization.

Thus, the position of the atoms in the glass seems to be fixed, but there are still forces between the atoms that tend to rearrange them. This is not a stable state, different from the state of the atoms in the paraffin. Therefore, it is also not a crystal. At room temperature, paraffin is completely solid, while glass can be thought of as a liquid with an extremely high viscosity.

Fourthly, glass characteristics

(1) Characteristics of glassy substances


The molecular structure of glass is random, and its molecules are statistically homogeneous in space. In an ideal state, the physical and chemical properties of homogeneous glass, such as refractive index, hardness, elastic modulus, thermal expansion coefficient, thermal conductivity, electrical conductivity, etc., are the same in all directions.

2. No fixed melting point

Because glass is a mixture, not a crystal. The transformation of glass from a solid to a liquid state occurs in a certain temperature range (i.e., in the softening temperature range), unlike crystalline substances, it does not have a fixed melting point.

3. Metastability

Vitreous substances are usually obtained by rapidly cooling molten bodies. During the transition from a molten state to a glassy state, the viscosity increases sharply during cooling. , The glassy substance contains a higher internal energy than the crystalline substance, and its energy is between the molten state and the crystalline state, which belongs to the metastable state. From a mechanical point of view, glass is an unstable high-energy state, for example, there is a tendency to go into a low-energy state, that is, a tendency to devitrify, therefore, glass is a metastable solid material. .

⒋ Gradient Reversal

The process of transition of a glassy substance from a molten state to a solid occurs gradually, and the change in its physico-chemical properties is also continuous and gradual. This obviously differs from the melt crystallization process: during the crystallization process, a new phase will inevitably appear, and many properties will change dramatically near the crystallization temperature. The glassy substance is completed in a wide range of temperatures from the molten state to the solid state. As the temperature gradually decreases, the viscosity of the glass melt gradually increases, and eventually a solid glass is formed, but no new phase is formed in the process. On the contrary, the process of heating the glass to the state of the melt is also gradual.

(ii) Glass characteristics

Glass has different properties depending on the type.

⒈ Good perspective and light transmission (visible light transmittance of 3mm and 5mm lenses is 87% and 84% respectively). The transmittance of near-infrared heat rays in sunlight is relatively high, but it can effectively block the long-wavelength far-infrared heat rays generated by the reflection of visible light on the upper floor, furniture, and fabrics in the room, so it can produce a distinct "warming effect". Clear glass has low UV transmittance in sunlight.

2. Sound insulation and certain heat retention characteristics.

⒊The tensile strength is much less than the compressive strength, which is a typical brittle material.

4. It has high chemical stability. Under normal conditions, it is highly resistant to acids, alkalis, salts, chemicals and gases, but long-term exposure to corrosive environments can also lead to deterioration and damage, such as glass. Weathering and mold damage the appearance and reduce light transmission. .

5. Thermal stability is poor and it is prone to rupture in extreme cold and extreme heat.

4. Ordinary flat glass

Flat glass comes in different thicknesses, and the thickness in millimeters is usually referred to as centimeters or pieces. What we call 3mm (piece) glass refers to glass with a thickness of 3mm glass.

⒈ 3-4mm thick glass, this glass is mainly used on the surface of picture frames.

2. 5-6mm thick glass, mainly used for small area light-transmitting molds such as exterior walls, windows and door leafs.

⒊ 7-9mm thick glass, mainly used in large area but frame protection structures, such as indoor screens.

⒋ 9-10mm thick glass can be used for large area interior partitions, railings and other decorative items.

⒌ Glass with a thickness of 11-12mm can be used for floor spring glass doors and some partitions with a large flow of people.

6. More than 15mm thick glass is mainly used for large floor glass doors and the whole outer wall glass wall.

5. Glass application

Glass is widely used in construction, everyday life, art, medicine, chemistry, electronics, instrumentation, nuclear energy and other fields.

⒈ Colored flat glass: It has the characteristics of corrosion resistance, erosion resistance and easy cleaning.

2. Glazed glass: has good chemical stability and decorative effect.

⒊ Embossed glass, sprayed glass, milky glass, faceted glass and frosted glass: depending on the different patterning techniques, there are various colors, shades and glitter effects, which are full of decorations.

4. Tinted glass: effectively absorbs heatsolar radiation to achieve the effect of thermal protection and energy saving; absorbs more visible light to make transmitted light soft; strongly absorbs UV rays to prevent UV rays from affecting the interior. ; Bright and durable color, enhances the shape of the building beautifully.

5. Coated glass: better thermal insulation effect, easy light pollution to the environment.

6. Insulating glass: good optical performance, good thermal insulation performance, anti-condensation and good sound insulation.

⒎ Tempered glass: high mechanical strength, good elasticity, good thermal stability, not easy to hurt people after broken, not easy to self-explode.

⒏ Reinforced glass: shards do not shatter after impact or sudden change in temperature, can briefly prevent the spread of flames;

⒐Laminated glass: good transparency, high impact resistance, adhesion of PVB interlayer film to protect fragments from scattering and injury to people, high strength, heat resistance, moisture resistance and frost resistance.

6. Glass cleaning and precautions

(1) Wipe glass

⒈ Wipe the glass: Wipe the glass frame clean with a towel first, then use the glass scraper to dip into the diluted aqueous glass solution, spread the glass evenly from top to bottom, use the glass scraper to clean it from top to bottom and wipe it dry The watermark left on the mesh frame and the watermark on the glass must be wiped off with the glass, otherwise marks will remain on the glass.

2. For daily cleaning, wipe with a damp towel or newspaper. In case of stains, wipe with a towel soaked in beer or warm vinegar. Mix vinegar and water in a ratio of 1: 2 and apply this in a spray, spray on glass, and then wipe it, it can be wiped very cleanly. In addition, you can also use commercially available glass cleaners and avoid cleaning with strong acid and alkali solutions. The surface of the glass is prone to frost in winter, and it can be wiped with a cloth soaked in concentrated salt water or white wine, which works very well.

3. Add 5% ammonia solution or gasoline to the water tank and use it to clean the glass. After the glass is slightly dry, wipe it with a dry cloth. Glass will be flawless, bright and transparent. When cleaning glass, you can choose from a variety of window cleaners to see if it is double or single.

4. If there is mold on the surface of the glass, you can mix hydrofluoric acid (HF) and water in a ratio of 1:8 (note: if it exceeds 1:8, it will cause damage to the hands), and wipe the glass.

Note: Be sure to take good care of the corrosion protection, and the skin must not touch the HF, otherwise it will be severely corroded! After wiping the glass, wipe it again with clean water and finally indry the glass.

⒌ Once the patterned frosted glass gets dirty, you can use a toothbrush dipped in detergent and rub the pattern to remove it. In addition, you can also drop some kerosene on the glass, or apply chalk dust and gypsum powder to the glass to dry it, and then wipe it with a clean cloth or cotton to keep the glass clean and shiny.

⒍Using plastic wrap and a damp cloth dampened with detergent can also "revive" oiled glass. First, spray the glass with a cleaner, then stick a plastic film to soften the hardened oil stains, after ten minutes, remove the plastic film and wipe it with a damp cloth. If you want the glass to be clean and shiny, you need to clean it by hand often. If there is handwriting on the glass, you can rub it with a rubber soaked in water, and then wipe it with a damp cloth; paint on glass, you can use cotton wool soaked in hot vinegar to wipe it; , can make it bright like a crystal.

ii Notes

⒈ In order to avoid unnecessary loss during transportation, we must pay attention to fixing and adding soft pads. It is generally recommended to use a groupage method for transportation. Vehicles must also pay attention to maintaining stability and low speed.

2. If the other side of the glass installation is closed, pay attention to surface cleaning before installation. It is best to use a special glass cleaner, and you can install it after it has completely dried and confirmed that there are no stains. When installing, it is best to use clean construction gloves.

⒊ Glass installation should be fixed with silicone sealant, and it should be used together with rubber sealing strips when installing windows, etc.

4.After construction is completed, attention should be paid to the placement of collision warning signs. Typically, stickers, colored tape, etc. can be used as a reminder.

⒌ Do not hit the glass surface hard at normal times. In order not to scratch the glass surface, it is better to spread the tablecloth. When placing things on glass furniture, handle them carefully and avoid collisions.

⒍ Glass furniture is best placed in a relatively fixed location, don't move back and forth at will; items should be placed stably, and heavy items should be placed on the bottom of the glass furniture to prevent the furniture from falling. due to unstable center of gravity. Also, avoid moisture, stay away from the stove, and insulate it from chemicals such as acids and alkalis to prevent corrosion and wear.

⒎ Do not collide with sharp objects.