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Foam Glass
Foam glass is a porous glass foam material. Its advantages as a building material include its light weight, high strength, and thermal and acoustic insulating properties. It is made by heating a mixture of crushed or granulated glass and a blowing agent (chemical foaming agent) such as carbon or limestone. Near the melting point of the glass, the blowing agent releases a gas, producing a foaming effect in the glass. After cooling the mixture hardens into a rigid material with gas-filled closed-cell pores comprising a large portion of its volume. As to chemical foaming agents, there are several additives that facilitate the release of the gaseous phase upon heat treatment. In general, these additives are categorized into two categories: a) redox and neutralization agents, and b) decomposing agents. Redox and neutralization agents include nonoxide materials, e.g. carbides or nitrides. Decomposing agents include sulfates, e.g. CaSO4•nH2O, organic compounds, and carbonates, e.g. Ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Building Insulation Materials
Building insulation materials are the building materials which form the thermal envelope of a building or otherwise reduce heat transfer. Insulation may be categorized by its composition (natural or synthetic materials), form (batts, blankets, loose-fill, spray foam, and panels), structural contribution ( insulating concrete forms, structured panels, and straw bales), functional mode (conductive, radiative, convective), resistance to heat transfer, environmental impacts, and more. Sometimes a thermally reflective surface called a radiant barrier is added to a material to reduce the transfer of heat through radiation as well as conduction. The choice of which material or combination of materials is used depends on a wide variety of factors. Some insulation materials have health risks, some so significant the materials are no longer allowed to be used but remain in use in some older buildings such as asbestos fibers and urea. Consideration of materials used Factors affecting the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Foam Glass Gravel
Foam glass gravel is a building material made from recycled glass. Characteristics Foam glass gravel is light and dimensionally stable, with a lambda rating of 0.08 W/mK and a specific weight of 150 kg per cubic metre. Being made from glass, the aggregate is non-combustive and inert, ageing resistant, pH neutral and insect and rodent resistant. The manufacturing process seals the air bubbles giving the gravel non-capillary properties. The material has a high compressive strength as well as insulatory properties making it ideal for insulated floor construction Sourcing and manufacture Glass shards are cleaned and milled to a powder before a foaming agent, active carbon, is added in either liquid or solid form. The material is passed through a continuous tunnel furnace and heated to a temperature of 800–900 °C. Optimum temperatures produce maximum quantities of the foamed product. The foamed molten glass breaks into gravel on cooling. Uses Foam glass gravel ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reticulated Foam
Reticulated foam is a very porous, low density solid foam. 'Reticulated' means like a net. Reticulated foams are extremely open foams i.e. there are few, if any, intact bubbles or cell windows. In contrast, the foam formed by soap bubbles is composed solely of intact (fully enclosed) bubbles. In a reticulated foam only the lineal boundaries where the bubbles meet ( Plateau borders) remain. The solid component of a reticulated foam may be an organic polymer like polyurethane, a ceramic or a metal. These materials are used in a wide range of applications where the high porosity and large surface area are needed, including filters, catalyst supports, fuel tank inserts, and loudspeaker covers. Structure and properties A description of the structure of reticulated foams is still being developed. While Plateau's laws, the rules governing the shape of soap films in foams were developed in the 19th century, a mathematical description of the structure is still debated. The computer-gener ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Porous Medium
A porous medium or a porous material is a material containing pores (voids). The skeletal portion of the material is often called the "matrix" or "frame". The pores are typically filled with a fluid ( liquid or gas). The skeletal material is usually a solid, but structures like foams are often also usefully analyzed using concept of porous media. A porous medium is most often characterised by its porosity. Other properties of the medium (e.g. permeability, tensile strength, electrical conductivity, tortuosity) can sometimes be derived from the respective properties of its constituents (solid matrix and fluid) and the media porosity and pores structure, but such a derivation is usually complex. Even the concept of porosity is only straightforward for a poroelastic medium. Often both the solid matrix and the pore network (also known as the pore space) are continuous, so as to form two interpenetrating continua such as in a sponge. However, there is also a concept of closed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ceramic Foam
Ceramic foam is a tough foam made from ceramics. Manufacturing techniques include impregnating open-cell polymer foams internally with ceramic slurry and then firing in a kiln, leaving only ceramic material. The foams may consist of several ceramic materials such as aluminium oxide, a common high-temperature ceramic, and gets insulating properties from the many tiny air-filled voids within the material. The foam can be used not only for thermal insulation, but for a variety of other applications such as acoustic insulation, absorption of environmental pollutants, filtration of molten metal alloys, and as substrate for catalysts requiring large internal surface area. It has been used as stiff lightweight structural material, specifically for support of reflecting telescope mirrors. Properties Ceramic foams are hardened ceramics with pockets of air or another gas trapped in Porosity, pores throughout the body of the material. With its ability to create a large specific surface are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metal Foam
Regular foamed aluminium A metal foam is a cellular structure consisting of a solid metal (frequently aluminium) with gas-filled pores comprising a large portion of the volume. The pores can be sealed (closed-cell foam) or interconnected (open-cell foam). The defining characteristic of metal foams is a high porosity: typically only 5–25% of the volume is the base metal. The strength of the material is due to the square–cube law. Metal foams typically retain some physical properties of their base material. Foam made from non-flammable metal remains non-flammable and can generally be recycled as the base material. Its coefficient of thermal expansion is similar while thermal conductivity is likely reduced. Definitions Open-cell Open-celled metal foam, also called metal sponge, can be used in heat exchangers (compact electronics cooling, cryogen tanks, PCM heat exchangers), energy absorption, flow diffusion, scrubbers, flame arrestors, and lightweight optics. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nanofoam
Nanofoams are a class of nanostructured, porous materials (foams) containing a significant population of pores with diameters less than 100 nm. Aerogels are one example of nanofoam. Metal Overview Metallic nanofoams are a subcategorization of nanofoams; more specifically, there are nanofoams consisting of metals, often pure, that form interconnected networks of ligaments that make up the structure of the foam. A variety of metals are used, including copper, nickel, gold, and platinum. Metallic nanofoams may offer certain advantages over alternative polymer nanofoams; structurally, they retain the electrical conductivity of metals, offer increased ductility, as well as the higher surface area and nano-architecture properties offered by nanofoams. Fabrication Synthesis of metallic nanofoams may be accomplished through a variety of methods. In 2006, researchers produced metal nanofoams by igniting pellets of energetic metal bis(tetrazolato)amine complexes. Nanofoams of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Conductivity
The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by k, \lambda, or \kappa. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal conductivity. For instance, metals typically have high thermal conductivity and are very efficient at conducting heat, while the opposite is true for insulating materials like Rockwool or Styrofoam. Correspondingly, materials of high thermal conductivity are widely used in heat sink applications, and materials of low thermal conductivity are used as thermal insulation. The reciprocal of thermal conductivity is called thermal resistivity. The defining equation for thermal conductivity is \mathbf = - k \nabla T, where \mathbf is the heat flux, k is the thermal conductivity, and \nabla T is the temperature gradient. This is known as Fourier's Law for heat conduction. Although commonly expressed as a scalar, the most general form ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Construction Aggregate
Construction aggregate, or simply aggregate, is a broad category of coarse- to medium-grained particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates. Aggregates are the most mined materials in the world. Aggregates are a component of composite materials such as concrete and asphalt; the aggregate serves as reinforcement to add strength to the overall composite material. Due to the relatively high hydraulic conductivity value as compared to most soils, aggregates are widely used in drainage applications such as foundation and French drains, septic drain fields, retaining wall drains, and roadside edge drains. Aggregates are also used as base material under foundations, roads, and railroads. In other words, aggregates are used as a stable foundation or road/rail base with predictable, uniform properties (e.g. to help prevent differential settling under the road or building), or as a low-cost exte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Porous Glass
Porous glass is glass that includes pores, usually in the nanometre- or micrometre-range, commonly prepared by one of the following processes: through metastable phase separation in borosilicate glasses (such as in their system SiO2-B2O3-Na2O), followed by liquid extraction of one of the formed phases; through the sol-gel process; or simply by sintering glass powder. The specific properties and commercial availability of porous glass make it one of the most extensively researched and characterized amorphous solids. Due to the possibility of modeling the microstructure, porous glasses have a high potential as a model system. They show a high chemical, thermal and mechanical resistance, which results from a rigid and incompressible silica network. They can be produced in high quality and with pore sizes ranging from 1 nm up to any desired value. An easy functionalization of the inner surface opens a wide field of applications for porous glasses. A further special advantage of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Obsidian
Obsidian () is a naturally occurring volcanic glass formed when lava extruded from a volcano cools rapidly with minimal crystal growth. It is an igneous rock. Obsidian is produced from felsic lava, rich in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. It is commonly found within the margins of rhyolitic lava flows known as obsidian flows. These flows have a high content of silica, granting them a high viscosity. The high viscosity inhibits diffusion of atoms through the lava, which inhibits the first step ( nucleation) in the formation of mineral crystals. Together with rapid cooling, this results in a natural glass forming from the lava. Obsidian is hard, brittle, and amorphous; it therefore fractures with sharp edges. In the past, it was used to manufacture cutting and piercing tools, and it has been used experimentally as surgical scalpel blades. Origin and properties The '' Natural History'' by the Roman writer Pliny the Elder inc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
