Lead-alkali glass is a relatively soft type of glass with an extremely high percentage of lead oxide (around 20%). It has excellent electrical insulating properties, making it popular in electrical applications.
Fossil glass has a higher refractive index than soda-lime glass and its natural luster makes it perfect for fine crystal tableware. Unfortunately, it is not resistant to high temperatures or drastic changes in temperature.
Borosilicate
Borosilicate glass is an exceptionally high-grade material used in various products, from kitchen ware to laboratory equipment. It also finds application in high-tech devices like wind turbine blades and printed circuit boards (PCBs).
Borosilicate is a type of lead-alkali glass containing large amounts of silica and boron oxide. It primarily consists of 81% silicon dioxide (SiO2) and 15% boron trioxide (B2O3).
Boren glass has an added advantage due to the presence of boron, as it does not expand or shrink when exposed to temperature changes like soda-lime glass does. Not only does this make the material much more resistant and durable, but also stronger overall.
Its outstanding chemical resistance and thermal shock properties make it an ideal choice for lab equipment and research applications. Furthermore, it has many industrial uses such as panels on consoles or viewing machinery.
Due to its strength, borosilicate is commonly used to manufacture water bottles and wine glasses. Furthermore, these glasses can be safely used in the kitchen since they won’t break under heat or pressure.
Another advantage of borosilicate is its safety; it’s resistant to acid and chemical degradation, meaning you won’t leach hazardous toxins into your beverage like plastic water bottles or cheaper stainless steel alternatives may. Thus, borosilicate makes for a much safer drinking option than those plastic water bottles or less expensive stainless steel alternatives.
Another advantage of borosilicate glass is its ease of workability and shapeability compared to other types of glass. This makes it perfect for many scientific laboratory tasks, such as mixing chemical compounds.
Boron can also be molded into shapes, which makes it ideal for making components for medical devices and other electronics. For instance, borosilicate glass can be formed into spheres to form glass microspheres – incredibly durable and heat-resistant.
Another advantage of borosilicate is that it’s free from lead and arsenic, making it better for the environment than glass that contains these elements. However, be aware that improper melting may result in defects.
Alkali barium
Alkali barium glass is an essential type of glass that contains barium as one of its principal elements. It finds applications in aerospace, industrial chemical processes and in bulbs for high-powered lamps. At home, cooking plates and other heat-resistant items may also be made using this glass type for use by homeowners.
Alkali barium glass composition varies depending on the manufacturer and its intended use. Some companies advertise that their formulations do not contain any lead, while others list lead concentrations at less than 3% by weight.
Studies have revealed that some alkali barium glasses do contain lead. These lead-alkali glasses can be found in lamps and other lighting products, as well as being an element in safety glass.
Contrary to popular belief, some of the lead in glass powders comes from barium itself – a mineral not naturally present in nature.
These lead-alkali glass powders were melted using several possible recipes and then tested to identify the role and source of sodium in the glass. This finding is significant because it was previously believed that sodium wasn’t required to form lead-barium glass.
By this method, twenty-four different combinations of raw materials were melted and tested for glass formation. The results revealed that sodium was essential in the process as it provided a source of sodium flux.
After the experiments, the altered glass powders were filtered through a Buchner funnel and dried for 24 hours at 50 degC to form gels. Subsequently, they were analysed using spectroscopic techniques and solid analysis.
The gels had a distinct morphology compared to that of pristine glass (Fig. 1a), likely due to the reduction in B and Na content from each powder during alteration.
Despite this distinction in morphology, alkali concentrations were consistent enough to transform glass to gel over time with volume constant rates. The resulting gels had consistent thicknesses that were well correlated to t1/2 (usually around 130 days) for most alkali-solutions.
Optical
Optical glass is used in many applications that require it to be transparent, allowing light to pass through and be seen. It also enables different wavelengths of light to be absorbed and transmitted, making it popular in optical communication, sterilization, and medical uses.
Ordinary glass, which is typically composed of silica (SiO2), cannot provide the optical clarity desired. Optical glasses are made from other oxides like boron oxide (B2O3) and alumina (Al2O3). When designing optical materials for production, the raw materials chosen must be taken into consideration so that a specific composition can be designed to achieve the desired performance level.
High-quality optical glass is distinguished by its refractive index. This value determines the focusing and dispersing power of lenses and prisms, and several factors influence it such as temperature, wavelength, and thickness of the glass.
Another critical characteristic of glass is its absorption coefficient, which measures the percentage of light that is absorbed rather than transmitted through it. This figure is especially crucial in lens manufacturing and can influence how well a particular lens performs.
Other characteristics of high-quality glass include its refractive index, Abbe number and coefficient of thermal expansion. These values differ between various glasses and must be taken into account when selecting one for use in a particular application.
Furthermore, glass must have a homogenous chemical composition to avoid bubbles or other imperfections that might affect its optical performance. This is particularly challenging with special optical glasses but can be achieved through meticulous mixing of all constituent parts.
For example, a high iron content in the raw material can lead to undesirable changes to the optical properties of the finished product. This is particularly pertinent when manufacturing optics for monochromatic light sources.
Thirdly, glass’ transmittance measures how well light is transmitted through it. This inverse value of transmission is crucial in lens manufacturing and can be affected by both temperature and thickness.
Optical glass is an essential tool in nearly all industries. Therefore, its production requires a great deal of expertise and precision.
Thermal shock
Thermal shock is a phenomenon in which materials are damaged due to sudden temperature changes. This damage occurs due to uneven expansion of different parts of the material, leading to tensile stress and cracking – an especially pressing concern for materials like glass and ceramics that experience rapid temperature swings.
Thermal shock damage can have devastating structural repercussions and is the reason why glass-lined equipment often requires reglazing after experiencing a major thermal shock event. The most vulnerable places for thermal shock to occur are fillet welds between vessel shell and jacket, at top and bottom jacket closure rings, as well as any buildup of sludge inside the reactor jacket.
There are several methods available to increase shock resistance of glass and other materials. One way is reducing their Coefficient of Linear Thermal Expansion (CTE). This coefficient measures how much expansion a material experiences when exposed to sudden temperature changes, measured using ASTM C149 testing method.
The second method is to strengthen the material by increasing its tensile strength. This can be accomplished by adding or removing elements from the mixture. For instance, borosilicate glass has greater strength than soda-lime due to boron oxide that binds silicate with aluminum oxide or sodium oxide.
Borosilicate glass is highly resistant to shock due to its low coefficient of linear thermal expansion. This makes it suitable for modeling intricate shapes and ideal for vacuum-insulated flasks and vessels.
Finally, borosilicate glass is more resistant to acid erosion than regular soda-lime glass and so it’s often chosen in chemistry labs.
Six types of glass can be classified based on their chemical composition: soda-lime, lead-alkali, borosilicate, alkali-aluminum-silica, 96% silica and fused silica. Of all these materials, fused silica is the hardest and costliest; with a CTE less than 5 x 10-6 at 20 degrees Celsius. As such it finds application in high temperature applications like solar cells.
