Tag: ADVANTAGE AND DISADVANTAGE - archiHUNGER

Glass has been a fascinating material to humankind since it was first made in about 500 BC. At first thought to possess magical properties, glass has come a long way. It is one of the most versatile and oldest materials in the building industry.  From its humble beginnings as a window pane in luxury houses of Pompeii to sophisticated structural members in new age buildings, its role in architecture has evolved over the years.

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Composition

The soda-lime-silicate glass used in buildings has the following composition:

&#; silica, the raw material, in the form of sand (70 to 72 %)
&#; soda, the flux, as carbonate and sulphate (approximately 14 %)
&#; lime, a stabiliser, in the form of limestone (approximately 10 %)
&#; various other oxides such as alumina and magnesia, to improve the physical properties of the glass, including its resistance to
atmospheric pollutants
&#; for body-tinted glasses, metal oxides can also be incorporated.

MANUFACTURING OF FLOAT GLASS

While each glass plant is different from the other, the float glass production process can be divided into five universal steps:

1. Batching of raw materials:

The main components, namely, soda lime glass, silica sand (73%), calcium oxide (9%), soda (13%) and magnesium (4%), are weighed and mixed into batches to which recycled glass (cullet) is added. The use of &#;cullet&#; reduces the consumption of natural gas. The materials are tested and stored for later mixing under computerised control.

2. Melting of raw materials in the furnace:

The batched raw materials pass from a mixing silo to a five-chambered furnace where they become molten at a temperature of approximately °C.
 

3. Drawing the molten glass onto the tin bath:

The molten glass is &#;floated&#; onto a bath of molten tin at a temperature of about °C. It forms a ribbon with a working width of mm which is normally between 3 and 25mm thick. The glass which is highly viscous and the tin which is very fluid do not mix and the contact surface between these two materials is perfectly flat.
 

4. Cooling of the molten glass in the annealing lehr:

On leaving the bath of molten tin, the glass &#; now at a temperature of 600°C &#; has cooled down sufficiently to pass to an annealing chamber called a lehr. The glass is now hard enough to pass over rollers and is annealed, which modifies the internal stresses enabling it to be cut and worked in a predictable way and ensuring flatness of the glass. As both surfaces are fire finished, they need no grinding or polishing.
 

5. Quality checks, automatic cutting, and storage:

After cooling, the glass undergoes rigorous quality checks and is washed. It is then cut into sheets of sizes of up to mm x mm which are in turn stacked, stored and ready for transport.

COMPOSITION  OF GLASS

Nearly all commercial glasses fall into one of six basic categories or types. These categories are based on chemical composition. Within each type, except for fused silica, there are numerous distinct compositions.

1. Soda-lime glass is the most common (90% of glass made), and least expensive form of glass. It usually contains 60-75% silica, 12-18% soda, 5-12% lime. Resistance to high temperatures and sudden changes of temperature are not good and resistance to corrosive chemicals is only fair. 

   
   

    

2. Lead glass has a high percentage of lead oxide (at least 20% of the batch). It is relatively soft, and its refractive index gives a brilliance that may be exploited by cutting. It is somewhat more expensive than soda-lime glass and is favored for electrical applications because of its excellent electrical insulating properties. 

   
   

    

3. Borosilicate glass is any silicate glass having at least 5% of boric oxide in its composition. It has high resistance to temperature change and chemical corrosion. Pipelines, light bulbs, photochromic glasses, sealed-beam headlights, laboratory ware, and bake ware are examples of borosilicate products. 

   
   

    

4. Aluminosilicate glass has aluminum oxide in its composition. It is similar to borosilicate glass but it has greater chemical durability and can withstand higher operating temperatures. Compared to borosilicate, aluminosilicates are more difficult to fabricate. When coated with an electrically conductive film, aluminosilicate glass is used as resistors for electronic circuitry. 

   
   

    

5. Ninety-six percent silica glass is a borosilicate glass, melted and formed by conventional means, then processed to remove almost all the non-silicate elements from the piece. By reheating to °C the resulting pores are consolidated. This glass is resistant to heat shock up to 900°C. 

   
   

    

6. Fused silica glass is pure silicon dioxide in the non-crystalline state. It is very difficult to fabricate, so it is the most expensive of all glasses. It can sustain operating temperatures up to °C for short periods.

HOW GLASS IS USED IN CONSTRUCTION

PROPERTIES OF GLASS

1. It absorbs, refracts or transmits light. It can be made transparent or translucent.

2. It can take excellent polish.

3. It is an excellent electrical insulator.

4. It is strong and brittle.

5. It can be blown, drawn or pressed.

6. It is not affected by atmosphere.

7. It has excellent resistance to chemicals.

8. It is available in various beautiful colours.

9. With the advancement in technology, it is possible to make glass lighter than cork or stronger than steel.

10. Glass panes can be cleaned easily.

VARIETIES OF GLASS

Float Glass:

Float glass is also called soda lime glass or clear glass. This is produced by annealing the molten glass and is clear and flat.

Tinted Glass:

Certain additions to the glass batch mix can add color to the clear glass without compromising its strength. Iron oxide is added to give glass a green tint; sulphar in different concentrations can make the glass yellow, red or black. Copper sulphate can turn it blue. etc.

Toughened Glass :

This type of glass is tempered, may have distortions and low visibility but it breaks into small dice-like pieces at modulus of rupture of psi. Hence it is used in making fire resistant doors etc. They are available in same weight and thickness range as float glass.

Laminated Glass:

This type of glass is made by sandwiching glass panels within a protective layer. It is heavier than normal glass and may cause optical distortions as well. It is tough and protects from UV radiation (99%) and insulates sound by 50%. Used in glass facades, aquariums, bridges, staircases, floor slabs, etc.

Shatterproof glass:

By adding a polyvinyl butyral layer, shatter proof glass is made. This type of glass does not from sharp edged pieces even when broken. Used in skylight, window, flooring, etc.

Extra clean glass:

This type of glass is hydrophilic i.e. The water moves over them without leaving any marks and photocatylitic i.e. they are covered with Nanoparticles that attack and break dirt making it easier to clean and maintain.

Double Glazed Units:

These are made by providing air gap between two glass panes in order to reduce the heat loss and gain. Normal glass can cause immense amount of heat gain and upto 30%of loss of heat of air conditioning energy. Green, energy efficient glass can reduce this impact.

Chromatic glass:

For more information, please visit RuiQi Optics.

This type of glass can control daylight and transparency effectively. These glass are available in three forms- photochromatic (light sensitive lamination on glass), thermochromatic (heat sensitive lamination on glass) and electrochromatic (light sensitive glass the transparency of which can be controlled by electricity switch.) It can be used in meeting rooms and ICUs

Glass blocks:

Hollow glass wall blocks are manufactured as two separate halves and, while the glass is still molten, the two pieces are pressed together and annealed. The resulting glass blocks will have a partial vacuum at the hollow center. Glass bricks provide visual obscuration while admitting light.

Advantages:

1. Use of glass in construction work adds beauty to the building.
2. Its use fulfills the architectural view for external decoration.
3. By using glass in interior, it saves the space inside the building.
4. Glass cladding in building fulfill functional requirement of lighting, heat retention and energy saving.
5. Its use appear a sense of openness and harmonious.
6. As toughened glass is available, one can have good interior design with the use of glass in transparent staircase, colored shelves, ceiling etc.
7. Glass is an excellent material for thermal insulation, water proofing and energy conservation.
8. Glass is bad conductor of heat; it saves energy in air conditioning of building.
9. For making glass partition on upper floors, no extra design is required for slab as glass is light in weight.

Disadvantages:

1. As glass is very costly material, it may increase the budgeted cost of construction work.
2. Use of glass also enhances the cost of security.
3. Its use in hilly area and desert may cause more maintenance cost.
4. Glass is also unsafe for earthquake proven area.

Coating refers to coating a transparent electrolyte film or metal film on the surface of the substrate material by physical or chemical methods. The purpose is to change the reflection and transmission characteristics of the material surface to reduce or increase the reflection, beam splitting, color separation, light filtering, polarization and other requirements.We can provide various optical coatings such as anti-reflective films, high-reflective films, spectral films, and metallic films. Broadband anti-reflective films are available for UV, visible, NIR and mid-infrared wavelengths.

Compared to K9 and bk7 materials, fused silica offers higher thermal properties and purity, as well as excellent environmental durability, making it more suitable for use in harsh applications.

Natural quartz, also called quartz glass, which is synthesized by a number of processes to form fused silica, is the most common and most important material for optical components. Compared to natural quartz, synthesized fused silica has a higher radiometric hardness and higher absolute transmittance. This enables it to have excellent optical properties in the ultraviolet, visible, near-infrared, and infrared bands, as well as in the terahertz band.

Windows are optical glass that have been ground and polished to form two surfaces parallel to each other. They are commonly used as protective devices for electronic sensors, optical lenses, and laser processing heads. When selecting a window, focus on its material transmission properties as well as its mechanical properties.The important parameters of windows are transmission, surface quality, thickness, parallelism, substrate material and other properties, which can be selected according to the specific application.

Windows are optical glass that have been ground and polished to form two surfaces parallel to each other. They are commonly used as protective devices for electronic sensors, optical lenses, and laser devices. With high transmittance, good heat resistance, and excellent environmental durability, fused silica windows are well suited for laser equipment, emission and detection protection equipment, and imaging systems in the UV spectrum.Our company can provide fused silica windows in various sizes.

Natural quartz, also called quartz glass, is synthesized by a number of processes to form fused silica (Fused silica). It is the most common and most important material for optical components. Compared to natural quartz, synthetic fused silica has a higher radiometric hardness and higher absolute transmittance. Therefore, it is able to have good optical properties in the UV, visible, near IR, IR bands, and terahertz bands.

According to the transmittance of different bands, quartz transmittance is classified as follows.

JGS1  Far Ultraviolet Optical Quartz Glass 185- nm 

JGS2  Ultraviolet Optical Quartz Glass 220- nm 

JGS3  Infrared Optical Quartz Glass 260- nm

Transmission spectroscopy:

These two images show the transmittance of fused silica and natural quartz respectively.

The above graph shows the transmission spectra of several commercial fused silica models, and it can be seen that they all have high transmission at 185-nm. Depending on the model, the transmission spectra vary slightly, for example, some models still have more than 80% transmission in the deep UV band at 165nm, some models have an absorption peak near nm, and some models can maintain more than 80% transmission until nm.

The chart below shows the transmission spectrum of natural quartz, which is only guaranteed to have high transmission from 270nm to nm and much lower transmission in the UV band than fused silica. The reflectance of natural and fused quartz is basically the same, both are less than <10%. In the near UV band it is close to 10%, and at any time the wavelength increases, the quartz reflectance slowly decreases to approximately 6% in the near IR band.

Monocrystalline

&#;There are no visible grain boundaries or wicker-like stripes on the crystal surface when examined under naked eye daylight. 

Sub-crystal

&#;When examined under naked-eye daylight, there are willow stripes on the surface of the crystal with an area < 1/6 (end diameter), and the willow stripes are not visible after polishing . 

Polycrystalline

&#;When examined under naked-eye daylight, there are penetrating crystal boundary lines on the surface of the crystal, and the difference in the degree of light and darkness between the two sides of the crystal boundary lines is obvious. 

&#;N-BK7

    N-BK7 is the most commonly used optical glass for processing high quality optical components,, with excellent transmittance from visible to near-infrared wavelengths(350-nm), and has a wide range of applications in telescopes, lasers and other fields. N-BK7 is generally chosen when the additional benefits of UV fused silica (very good transmittance and low coefficient of thermal expansion in the UV band) are not required.

&#;UV fused silica

     UV fused silica has a high transmission from the UV to NIR  (185-nm).  In addition, UV fused silica has better uniformity and lower coefficient of thermal expansion than H-K9L (N-BK7), making it particularly suitable for high power laser and imaging applications.

&#;Calcium fluoride

    Due to its high transmittance and low refractive index within a wavelength of 180nm-8um, calcium fluoride is often used as windows and lenses in spectrometers and thermal imaging systems. In addition, it has good applications in excimer lasers because of its high laser damage threshold.

&#;Barium fluoride

    Barium fluoride have high transmittance from the 200nm-11um and they are resistant to stronger high-energy radiation. At the same time, barium fluoride has excellent scintillation properties and can be made into various infrared and ultraviolet optical components. However, the disadvantage of barium fluoride is that it is less resistant to water. When exposed to water, the performance degrades significantly at 500&#;, but it can be used for applications up to 800&#; in a dry environment. At the same time, barium fluoride has excellent scintillation properties and can be made into various infrared and ultraviolet optical components.It should be noted that when handling barium fluoride material, gloves must be worn at all times and hands must be washed thoroughly after handling.

&#;Magnesium fluoride 

    Magnesium fluoride is ideal for applications in the wavelength range of 200nm-6um. Compared to other materials, magnesium fluoride is particularly durable in the deep UV and far IR wavelength ranges. Magnesium fluoride is a powerful material for resistance to chemical corrosion, laser damage, mechanical shock and thermal shock. It is harder than calcium fluoride crystals, but relatively soft compared to fused silica, and has a slight hydrolysis. It has a Nucleus hardness of 415 and a refractive index of 1.38.

&#;Zinc selenide 

    Zinc selenide has high transmittance in the 600nm-16um and is commonly used in thermal imaging, infrared imaging, and medical systems. Also, due to its low absorption, zinc selenide is particularly suitable for use in high-power CO2 lasers. It should be noted that zinc selenide is a relatively soft material (Nucleus hardness 120) and is easily scratched, so it is not recommended for use in harsh environments. Extra care should be taken when holding, and cleaning, pinching or wiping with even force, and it is best to wear gloves or rubber finger covers to prevent tarnishing. Cannot be held with tweezers or other tools.

&#;Silicon 

    Silicon is suitable for use in the NIR band from 1.2-8um.Because of its low 

    density, silicon is particularly suitable in applications where weight

    requirements are sensitive, especially in the 3-5um . Silicon has a Nucleus 

    hardness of , which is harder than germanium and not as fragile as 

    germanium.It is not suitable for transmission applications in CO2 lasers 

    because of its strong absorption band at 9um.

&#;Germanium 

    Germanium is suitable for use in the near-infrared band of 2-16um and is well 

    suited for infrared lasers. Due to its high refractive index, minimal surface 

    curvature and low chromatic aberration, germanium does not usually require 

    correction in low power imaging systems. However, germanium is more 

    severely affected by temperature, and the transmittance decreases with

    increasing temperature; therefore, it can only be applied below 100°C. The 

    density of germanium (5.33 g/cm³) is taken into account when designing 

    systems with strict weight requirements. Germanium lenses feature a

    precision diamond lathe turned surface, a feature that makes them well suited

    for a variety of infrared applications, including thermal imaging systems, 

    infrared beam splitters, telemetry, and in the forward-looking infrared (FLIR)

    field.

&#;CVD ZnS 

    CVD ZnS is the only infrared optical material, other than diamond, that covers visible to long-wave infrared (LWIR), full wavelength and even microwave wavelengths, and is currently the most important LWIR window material. It can be used as windows and lenses for high-resolution thermal imaging systems, as well as for advanced military applications such as "tri-optical" windows and near-infrared laser/dual-color infrared composite windows.

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