วันเสาร์ที่ 6 กรกฎาคม พ.ศ. 2556

What kind of glue.


fabricglue.First. Adhesive fabric (Fabric Glue).
Was produced to be used for material fabric By this time the adhesive will not harm the skin. And less time to dry.
superglue.Two. Glucosamine super glue (Super Glue).
Perhaps we could call this type of glue that "Glue CA" production of chemicals called cyanobacteria acrylate. You are the glue that hold the joint practice is quite tight and dry within 10 to 30 seconds by just one square inch of adhesive bonding material that weighs more than one ton easily. The box will look like a liquid or gel.Can be put to immediate use. If the liquid is applied to materials, plastic, metal, rubber, vinyl and ceramic tiles. Girl with a gel adhesive. Materials to be used with wood and material with different pore. Applications just dipping glue surface to be identified only There are many brands to choose from and the type of adhesive that hot glue.

Adhesive types.

In the year 1951 Dr.Harry Coover has partnered with Dr.Fred Joyner led the cyanobacterium acrylate compounds to new research by the then Dr.Harry Coover moved to the Kodak Company. The Eastman Company in the State of Tennessee, USA Tel. During which they are conducting research on the heat resistance of Acrylate polymers. (Acrylate-polymer) for use in the roof (Canopies) of the jet on Dr.Fred Joyner growing film material for ethyl acrylate cyanobacterium. (Ethylcyanoacrylate) crystalline substance, he has seen it happen more attention. Seriously and has conducted research with other drivers. Cooper River until the dream came true when he brought substance acrylate polymer was produced in the year 1958 in the name of "The Eastman Compound # 910" and a favorite as well as "Super. glucosamine (Super Glue) ".
After getting to know the history then. We came to know each type of adhesive do it.

Adhesive types.

When the fracture of materials. Or that we want to connect two materials together. We often use a chemical one. Which has the ability to help coordinate things. Them with good adhesion. Chemicals that help to coordinate this, we often refer to it as the "glue" itself.
Mostly by adhesive material containing polymer is poly (Polymer), which is composed of subunits called monomers (Monomer) concatenating a long chain molecules. Similar to the paper clip to clamp together. The adhesive was then. Because of long molecular wires. That is tied to it. Now we come to know the history of the glue before it.
Glue was first produced in England around 1750 by the time it was used as raw material in the manufacture of fish glue and subsequently developed by the introduction of rubber. Nature, animal bones, starch, protein and dairy etc. Used as raw material in the manufacture of various types of glue. With the emergence of advanced even more so in the year 1942 Dr.Harry Coover, who at that time was working in the laboratory of the Kodak Research Laboratories have discovered a chemical called cyanobacteria acrylate. (Cyanoacrylate, CH NO) with cohesive and adhesive properties. He is offering a Kodak company, but the company has denied this material. Due to the application of this cohesive and adhesive properties too.

วันอังคารที่ 11 มิถุนายน พ.ศ. 2556

Thermal insulation

Thermal insulation

From Wikipedia, the free encyclopedia
Mineral wool Insulation, 1600 dpi scan against the grain Thermal insulation is the reduction of heat transfer (the transfer of thermal energy between objects of differing temperature) between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with specially engineered methods or processes, as well as with suitable object shapes and materials.
Heat flow is an inevitable consequence of contact between objects of differing temperature. Thermal insulation provides a region of insulation in which thermal conduction is reduced or thermal radiation is reflected rather than absorbed by the lower-temperature body. The insulating capability of a material is measured with thermal conductivity (k).
Low thermal conductivity is equivalent to high insulating capability (R-value). In thermal engineering, other important properties of insulating materials are product density (ρ) and specific heat capacity (c).

Clothing of Thermal insulation

Clothing of Thermal insulation

Clothing can help control the temperature of the human body. To offset high ambient temperature insulation, clothing can enable sweat to evaporate (thus permitting cooling by evaporation). The billowing of fabric during movement can create air currents that increase evaporation and cooling. A layer of fabric then insulates slightly and can help keep skin temperatures to a cooler level.
To combat low ambient temperatures, a thick insulation is desirable to reduce conductive heat loss. Other things being equal, a thick sleeping bag is warmer than a thin one. At the same time, evacuating skin humidity remains important: several layers of materials with different properties may be used to achieve this goal while lowering heat losses so they match the body’s internal heat production. Clothing heat loss occurs due to wind, radiation of heat into space, and conductive bridging. The latter is most apparent in footwear where insulation against conductive heat loss to the ground is most important.
Buildings Main article: Building insulation
Common insulation applications in apartment building in Ontario, Canada. Maintaining acceptable temperatures in buildings (by heating and cooling) uses a large proportion of global energy consumption. When well insulated, a building: is energy-efficient, thus saving the owner money. provides more uniform temperatures throughout the space. There is less temperature gradient both vertically (between ankle height and head height) and horizontally from exterior walls, ceilings and windows to the interior walls, thus producing a more comfortable occupant environment when outside temperatures are extremely cold or hot. has minimal recurring expense. Unlike heating and cooling equipment, insulation is permanent and does not require maintenance, upkeep, or adjustment.
lowers the Tripton rating of the carbon footprint produced by the house. Many forms of thermal insulation also reduce noise and vibration, both coming from the outside and from other rooms inside a building, thus producing a more comfortable environment. Window insulation film can be applied in weatherization applications to reduce incoming thermal radiation in summer and loss in winter. In industry, energy has to be expended to raise, lower, or maintain the temperature of objects or process fluids. If these are not insulated, this increases the energy requirements of a process, and therefore the cost and environmental impact.

Mechanical systems of High Temperature Adhesive

Mechanical systems 


Thermal insulation applied to exhaust component by means of plasma spraying
Space heating and cooling systems distribute heat throughout buildings by means of pipe or ductwork. Insulating these pipes using pipe insulationreduces energy into unoccupied rooms and prevents condensation from occurring on cold and chilled pipework.
Pipe insulation is also used on water supply pipework to help delay pipe freezing for an acceptable length time.
Spacecraft
Thermal insulation on the Huygens probe
Cabin insulation of a Boeing 747-8 airliner
Launch and re-entry place severe mechanical stresses on spacecraft, so the strength of an insulator is critically important (as seen by the failure of insulating foam on the Space Shuttle Columbia). Re-entry through the atmosphere generates very high temperatures due to compression of the air at high speeds. Insulators must meet demanding physical properties beyond their thermal transfer retardant properties. E.g. reinforced carbon-carbon composite nose cone and silica fiber tiles of the Space Shuttle. See also Insulative paint.

Spacecraft

Thermal high temperatures Insulation on the Huygens probe
Cabin insulation of a Boeing 747-8 airliner Launch and re-entry place severe mechanical stresses on spacecraft, so the strength of an insulator is critically important (as seen by the failure of insulating foam on the Space Shuttle Columbia). Re-entry through the atmosphere generates very high temperatures Insulation  due to compression of the air at high speeds. Insulators must meet  demanding physical properties beyond their thermal transfer retardant properties. E.g. reinforced carbon-carbon composite nose cone and silica fiber tiles of the Space Shuttle. See also Insulative paint.

Thermal insulation on the Huygens probe


 
Cabin insulation of a Boeing 747-8 airliner

Automotive
Main article: Exhaust Heat Management

Internal combustion engines produce a lot of heat during their combustion cycle. This can have a negative effect when it reaches various heat-sensitive components such as sensors, batteries and starter motors. As a result, thermal insulation is necessary to prevent the heat from the exhaust reaching these components
High performance cars often use thermal insulation as a means to increase engine performance.

Factors influencing performance of high temperatures Insulation

Factors influencing performance
Insulation performance is influenced by many factors the most prominent of which include:
  • Thermal conductivity ("k" or "λ" value)
  • Surface emissivity ("ε" value)
  • Insulation thickness
  • Density
  • Specific heat capacity
  • Thermal bridging
It is important to note that the factors influencing performance may vary over time as material ages or environmental conditions change.
Calculating requirements Industry standards are often rules of thumb, developed over many years, that offset many conflicting goals: what people will pay for, manufacturing cost, local climate, traditional building practices, and varying standards of comfort. Both heat transfer and layer analysis may be performed in large industrial applications, but in household situations (appliances and building insulation), air tightness is the key in reducing heat transfer due to air leakage (forced or natural convection).
Once air tightness is achieved, it has often been sufficient to choose the thickness of the insulating layer based on rules of thumb. Diminishing returns are achieved with each successive doubling of the insulating layer. It can be shown that for some systems, there is a minimum insulation thickness required for an improvement to be realized. high temperatures Insulation

วันจันทร์ที่ 27 พฤษภาคม พ.ศ. 2556

Portland cement blends are often available as inter-ground mixtures from cement producers,

Portland cement blends
Portland cement blends are often available as inter-ground mixtures from cement producers, but similar formulations are often also mixed from the ground components at the concrete mixing plant. Portland blastfurnace cement contains up to 70% ground granulated blast furnace slag, with the rest Portland clinker and a little gypsum. All compositions produce high ultimate strength, but as slag content is increased, early strength is reduced, while sulfate resistance increases and heat evolution diminishes. Used as an economic alternative to Portland sulfate-resisting and low-heat cements. Portland flyash cement contains up to 35% fly ash. The fly ash is pozzolanic, so that ultimate strength is maintained. Because fly ash addition allows a lower concrete water content, early strength can also be maintained. Where good quality cheap fly ash is available, this can be an economic alternative to ordinary Portland cement. Portland pozzolan cement includes fly ash cement, since fly ash is a pozzolan, but also includes cements made from other natural or artificial pozzolans. In countries where volcanic ashes are available (e.g. Italy, Chile, Mexico, the Philippines) these cements are often the most common form in use. Portland silica fume cement. Addition of silica fume can yield exceptionally high strengths, and cements containing 5–20% silica fume are occasionally produced. However, silica fume is more usually added to Portland cement at the concrete mixer.[20] Masonry cements are used for preparing bricklaying mortars and stuccos, and must not be used in concrete. They are usually complex proprietary formulations containing Portland clinker and a number of other ingredients that may include limestone, hydrated lime, air entrainers, retarders, waterproofers and coloring agents. They are formulated to yield workable mortars that allow rapid and consistent masonry work. High Temperature Cement
Subtle variations of Masonry cement in the US are Plastic Cements and Stucco Cements. These are designed to produce controlled bond with masonry blocks. Expansive cements contain, in addition to Portland clinker, expansive clinkers (usually sulfoaluminate clinkers), and are designed to offset the effects of drying shrinkage that is normally encountered with hydraulic cements. This allows large floor slabs (up to 60 m square) to be prepared without contraction joints. White blended cements may be made using white clinker and white supplementary materials such as high-purity metakaolin. Colored cements are used for decorative purposes. In some standards, the addition of pigments to produce "colored Portland cement" is allowed. In other standards (e.g. ASTM), pigments are not allowed constituents of Portland cement, and colored cements are sold as "blended hydraulic cements". Very finely ground cements are made from mixtures of cement with sand or with slag or other pozzolan type minerals that are extremely finely ground together. Such cements can have the same physical characteristics as normal cement but with 50% less cement particularly due to their increased surface area for the chemical reaction. Even with intensive grinding they can use up to 50% less energy to fabricate than ordinary Portland cements.

High Temperature Cement :Pozzolan-lime cements. Mixtures of ground pozzolan

Non-Portland hydraulic cements
Pozzolan-lime cements. Mixtures of ground pozzolan and lime are the cements used by the Romans, and can be found in Roman structures still standing (e.g. the Pantheon in Rome). They develop strength slowly, but their ultimate strength can be very high. The hydration products that produce strength are essentially the same as those produced by Portland cement. Slag-lime cements. Ground granulated blast furnace slag is not hydraulic on its own, but is "activated" by addition of alkalis, most economically using lime. They are similar to pozzolan lime cements in their properties. Only granulated slag (i.e. water-quenched, glassy slag) is effective as a cement component. Supersulfated cements. These contain about 80% ground granulated blast furnace slag, 15% gypsum or anhydrite and a little Portland clinker or lime as an activator. They produce strength by formation of ettringite, with strength growth similar to a slow Portland cement. They exhibit good resistance to aggressive agents, including sulfate. Calcium aluminate cements are hydraulic cements made primarily from limestone and bauxite. The active ingredients are monocalcium aluminate CaAl2O4 (CaO · Al2O3 or CA in Cement chemist notation, CCN) and mayenite Ca12Al14O33 (12 CaO · 7 Al2O3, or C12A7 in CCN). Strength forms by hydration to calcium aluminate hydrates. They are well-adapted for use in refractory (high-temperature resistant) concretes, e.g. for furnace linings. Calcium sulfoaluminate cements are made from clinkers that include ye'elimite (Ca4(AlO2)6SO4 or C4A3S in Cement chemist's notation) as a primary phase. They are used in expansive cements, in ultra-high early strength cements, and in "low-energy" cements. Hydration produces ettringite, and specialized physical properties (such as expansion or rapid reaction) are obtained by adjustment of the availability of calcium and sulfate ions. Their use as a low-energy alternative to Portland cement has been pioneered in China, where several million tonnes per year are produced.[22][23] Energy requirements are lower because of the lower kiln temperatures required for reaction, and the lower amount of limestone (which must be endothermically decarbonated) in the mix. In addition, the lower limestone content and lower fuel consumption leads to a CO2 emission around half that associated with Portland clinker. However, SO2 emissions are usually significantly higher. "Natural" cements correspond to certain cements of the pre-Portland era, produced by burning argillaceous limestones at moderate temperatures. The level of clay components in the limestone (around 30–35%) is such that large amounts of belite (the low-early strength, high-late strength mineral in Portland cement) are formed without the formation of excessive amounts of free lime. As with any natural material, such cements have highly variable properties. Geopolymer cements are made from mixtures of water-soluble alkali metal silicates and aluminosilicate mineral powders such as fly ash and metakaolin.

วันพุธที่ 10 เมษายน พ.ศ. 2556

Types of modern cement


Non-Portland hydraulic cements
Pozzolan-lime cements. Mixtures of ground pozzolan and lime are the cements used by the Romans, and can be found in Roman structures still standing (e.g. the Pantheon in Rome). They develop strength slowly, but their ultimate strength can be very high. The hydration products that produce strength are essentially the same as those produced by Portland cement. Slag-lime cements. Ground granulated blast furnace slag is not hydraulic on its own, but is "activated" by addition of alkalis, most economically using lime. They are similar to pozzolan lime cements in their properties. Only granulated slag (i.e. water-quenched, glassy slag) is effective as a cement component. Supersulfated cements. These contain about 80% ground granulated blast furnace slag, 15% gypsum or anhydrite and a little Portland clinker or lime as an activator. They produce strength by formation of ettringite, with strength growth similar to a slow Portland cement. They exhibit good resistance to aggressive agents, including sulfate. Calcium aluminate cements are hydraulic cements made primarily from limestone and bauxite. The active ingredients are monocalcium aluminate CaAl2O4 (CaO · Al2O3 or CA in Cement chemist notation, CCN) and mayenite Ca12Al14O33 (12 CaO · 7 Al2O3, or C12A7 in CCN). Strength forms by hydration to calcium aluminate hydrates. They are well-adapted for use in refractory (high-temperature resistant) concretes, e.g. for furnace linings. Calcium sulfoaluminate cements are made from clinkers that include ye'elimite (Ca4(AlO2)6SO4 or C4A3S in Cement chemist's notation) as a primary phase. They are used in expansive cements, in ultra-high early strength cements, and in "low-energy" cements. Hydration produces ettringite, and specialized physical properties (such as expansion or rapid reaction) are obtained by adjustment of the availability of calcium and sulfate ions. Their use as a low-energy alternative to Portland cement High Temperature Cement has been pioneered in China, where several million tonnes per year are produced.[40][41] Energy requirements are lower because of the lower kiln temperatures required for reaction, and the lower amount of limestone (which must be endothermically decarbonated) in the mix. In addition, the lower limestone content and lower fuel consumption leads to a CO2 emission around half that associated with Portland clinker. However, SO2 emissions are usually significantly higher. "Natural" cements correspond to certain cements of the pre-Portland era, produced by burning argillaceous limestones at moderate temperatures. The level of clay components in the limestone (around 30–35%) is such that large amounts of belite (the low-early strength, high-late strength mineral in Portland cement) are formed without the formation of excessive amounts of free lime. As with any natural material, High Temperature Insulation such cements have highly variable properties. Geopolymer cements are made from mixtures of water-soluble alkali metal silicates and aluminosilicate mineral powders such as fly ash and metakaolin.

Types of modern cement


Portland cement blends

Portland cement blends are often available as inter-ground mixtures from cement producers, but similar formulations are often also mixed from the ground components at the concrete mixing plant.[35] Portland blastfurnace cement contains up to 70% ground granulated blast furnace slag, with the rest Portland clinker and a little gypsum. All compositions produce high ultimate strength, but as slag content is increased, early strength is reduced, while sulfate resistance increases and heat evolution diminishes. Used as an economic alternative to Portland sulfate-resisting and low-heat cements.Portland flyash cement contains up to 35% fly ash. The fly ash is pozzolanic, so that ultimate strength is maintained. Because fly ash addition allows a lower concrete water content, early strength can also be maintained. Where good quality cheap fly ash is available, this can be an economic alternative to ordinary Portland cement Portland pozzolan cement includes fly ash cement, since fly ash is a pozzolan, but also includes cements made from other natural or artificial pozzolans. In countries where volcanic ashes are available (e.g. Italy, Chile, Mexico, the Philippines) these cements are often the most common form in use.. High Temperature Insulation  Portland silica fume cement. Addition of silica fume can yield exceptionally high strengths, and cements containing 5–20% silica fume are occasionally produced.

However, silica fume is more usually added to Portland cement at the concrete mixer. Masonry cements are used for preparing bricklaying mortars and stuccos, and must not be used in concrete. They are usually complex proprietary formulations containing Portland clinker and a number of other ingredients that may include limestone, hydrated lime, air entrainers, retarders, waterproofers and coloring agents. They are formulated to yield workable mortars that allow rapid and consistent masonry work. Subtle variations of Masonry cement in the US are Plastic Cements and Stucco Cements. These are designed to produce controlled bond with masonry blocks. Expansive cements contain, in addition to Portland clinker, expansive clinkers (usually sulfoaluminate clinkers), and are designed to offset the effects of drying shrinkage that is normally encountered with hydraulic cements. This allows large floor slabs (up to 60 m square) to be prepared without contraction joints. White blended cements may be made using white clinker and white supplementary materials such as high-purity metakaolin. Colored cements are used for decorative purposes.
High Temperature Cement

In some standards, the addition of pigments to produce "colored Portland cement" is allowed. In other standards (e.g. ASTM), pigments are not allowed constituents of Portland cement, and colored cements are sold as "blended hydraulic cements". Very finely ground cements are made from mixtures of cement with sand or with slag or other pozzolan type minerals that are extremely finely ground together. Such cements can have the same physical characteristics as normal cement but with 50% less cement particularly due to their increased surface area for the chemical reaction. Even with intensive grinding they can use up to 50% less energy to fabricate than ordinary Portland cements.

Types of modern cement



Portland cement

Main article: Portland cement

Cement is made by heating limestone (calcium carbonate) with small quantities of other materials (such as clay) to 1450 °C in a kiln, in a process known as calcination, whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide, or quicklime, which is then blended with the other materials that have been included in the mix. The resulting hard substance, called 'clinker', is then ground with a small amount of gypsum into a powder to make 'Ordinary Portland Cement', the most commonly used type of cement (often referred to as OPC). Portland cement is a basic ingredient of concrete, mortar and most non-specialty grout. The most common use for Portland cement is in the production of concrete. Concrete is a composite material consisting of aggregate (gravel and sand), cement, High Temperature Cement and water. As a construction material, concrete can be cast in almost any shape desired, and once hardened, can become a structural (load bearing) element. Portland cement may be grey or white.
[edit]Energetically Modified Cement ("EMC Cement")


Proving Energetically Modified Cement's "self-healing" capabilities...



PHOTO A: Proving Energetically Modified Cement's "self-healing" capabilities. Mechanically-induced cracking in concrete comprising EMC Cement, caused by RILEM 3-point bending induced after ~3 weeks of water curing (September, 2012). Cracks had an average width of 150-200 μm.
The photo above depicts a concrete test-beam made from EMC Cement undergoing RILEM 3-point bending at Luleå University of Technology in Sweden (February, 2013). This treatment induces cracks so as to test for EMC Cement's "self-healing" capabilities.



PHOTO B: Former cracks in concrete comprising EMC Cement, taken 5 months after PHOTO A. The photograph shows that the former cracks had undergone a complete "self healing" process without any intervention, by virtue of newly-synthesized CSH gel — itself a product of the ongoing pozzolanic reaction.
Concrete (total cmt: 350 kg/m³) containing 40% Portland cement and 60% EMC Cement made from fly ash was used. Cracks of average width 150-200 μm were induced after ~3 weeks of water curing. This is depicted in PHOTO A.

Control cubes were tested for compressive strength at different ages.

As expected, without any intervention the high volume pozzolan concrete exhibited the gradual filling-in of the cracks with newly-synthesized CSH gel (a product of the ongoing pozzolanic reaction). These were completely filled-in after ~4.5 months. This is depicted in PHOTO B.

During the observation period, continuous strength-development was also recorded by virtue of the ongoing pozzolanic reaction. This, together with the observed "self healing" properties, both have a positive impact on concrete durability.

All photos courtesy of Dr. V. Ronin
An alternative fabrication technique EMC (Energetically Modified Cement) produces cementitious materials made from pozzolanic minerals that have been treated using a patented milling process ("EMC Activation").[13] The resultant concretes can have the same, if not improved, physical characteristics as "normal" concretes — at a fraction of the Portland cement. Note, although Energetically Modified Cement is able to replace Portland cement in concrete to high levels, it cannot fully replace it.
Energetically Modified Cement is better known as "EMC Cement". EMC Cement may be classified both as an "Alternative Cementitious Material" and as a "Supplemental Cementitious Material", on account of the range of the Portland cement replacement-ratios offered. Colloquially, EMC Cement may be referred-to also as a "Green Cement", on account of the significant energy and carbon dioxide savings yielded by EMC Activation as compared to Portland cement production.
The trade name for EMC Cement is "CemPozz". At the 45th World Exhibition of Invention, Research and Innovation, held in Bruxelles, Belgium, EMC Activation was awarded the Gold Medal "with mention" by the EUREKA Organisation (the pan-European research & development funding and coordination organization, comprising all 27 EU Member States). High Temperature Insulation

Put simply, EMC Activation is a patented, cost– and energy–efficient, near zero-emission technology for the high replacement of Portland cement in concrete.

Materials that are used to replace Portland cement in concrete (such as fly ash, blast furnace slag, natural pozzolans – e.g. volcanic ash – and silica sand) are mechanically activated in proprietary milling systems.EMC Activation increases the amount of Portland cement that can be replaced over and above "traditional" replacement methods (which typically replace an average of circa. 15% of the Portland Cement in concrete). By contrast, up to 70% of the Portland cement in concrete can be replaced using EMC Cement.
EMC Activation generates high-energy particle impacts. This leads to deep transformations in the particle micro-structure in the form of (among others) sub-micro cracks, dislocations and lattice defects that significantly increase reactivity, with no material increase in overall powder fineness.
EMC Cements comply with relevant normative standards and specifications. For example, where EMC Cement is made from fly ash, high Portland cement replacements (i.e., the replacement of at least 50% Portland cement) yield concretes that exhibit consistent field results.This is also the case for EMC Cement made from natural pozzolans (e.g., volcanic ash).

For example, volcanic ash deposits situated in Southern California of the United States were tested by independent consultants, according to the relevant normative standards. EMC Activation was then applied to the raw materials. At 50% Portland cement replacement, the resulting concretes exceeded the normative requirements. At 28 days, the compressive strength was recorded at 4,180 psi / 28.8 MPa (N/mm²). The 56-day strength exceeded the requirements for 4,500 psi (31.1 Mpa) concrete, even taking into account the safety margin as recommended by the American Concrete Institute.

EMC Cement presents dramatic savings both in terms of carbon dioxide and energy-savings. The figures vary slightly depending on the source material used. For example, if volcanic ash is used, the resulting compound has to be dried. This drying process consumes about 150,000 Btu per ton of EMC Cement produced.

All in all, as compared to a total energy consumption of ~1,000 to 1,400 KWh for each ton of Portland cement produced:
For each ton of EMC Cement made from fly ash, the energy requirement is usually ~25 KWh. There are no direct CO2 emissions.
For each ton EMC Cement made from volcanic ash, the energy requirement (including drying, as above) is no more than ~80KWh, with direct emissions of only 8 kgs CO2 per ton.

The performance of concretes made from EMC Cement can also be custom designed. Hence, concretes can range from those exhibiting superior strength and durability that reduce the carbon footprint at up to ~70% as compared to concretes made from Portland Cement, through to the production of rapid and ultra-rapid hardening, high-strength concretes (for example, over 70 MPa / 10,150 psi in 24 hours and over 200 MPa / 29,000 psi in 28 days).This allows EMC Cement to yield High Performance Concretes (HPCs).
EMC Cement exhibits a high resistance to chloride and sulfate ion attack, together with a low Alkali–Silica Reactivity (ASR).These features allow concretes made from EMC Cement to exhibit superior durabilities as compared to concretes made from Portland cement. For example, an early project using EMC Cement was the construction of a road bridge in Karungi, Sweden, with Swedish construction firm Skanska. The Karungi road bridge has successfully withstood the tests of time, despite Karungi's harsh subarctic climate and extremely divergent diurnal temperatures.

EMC Activation and EMC Cements are well-proven to an "industrial scale". In the United States, EMC Cement has been approved for usage by PennDOT (Pennsylvania Department of Transportation), TxDOT (Texas Department of Transportation) and CalTrans (California Department of Transportation). As a result, hundreds of miles of highway paving have been laid, together with assorted highway bridges, using concretes made from EMC Cement — including large sections of Interstate 10, which is the main U.S. Interstate highway linking Miami, Florida with Los Angeles, California.
Another notable project in the United States includes the extension of the passenger terminals at the Port of Houston, Texas. This project fully exploits EMC Cement's known propensity to yield concretes that exhibit high-resistances to chloride– and sulfate–ion permeability (i.e., increased resistance to sea waters), as compared to concretes made from Portland cement.

History of the origin of cement


Modern cements
Modern hydraulic cements began to be developed from the start of the Industrial Revolution (around 1800),

driven by three main needs:
Hydraulic cement render (stucco) for finishing brick buildings in wet climates.
Hydraulic mortars for masonry construction of harbor works, etc., in contact with sea water.
Development of strong concretes.

In Britain particularly, good quality building stone became ever more expensive during a period of rapid growth, and it became a common practice to construct prestige buildings from the new industrial bricks, and to finish them with a stucco to imitate stone. Hydraulic limes were favored for this, but the need for a fast set time encouraged the development of new cements. Most famous was Parker's "Roman cement". This was developed by James Parker in the 1780s, and finally patented in 1796. It was, in fact, nothing like any material used by the Romans, but was a "Natural cement" made by burning septaria – nodules that are found in certain clay deposits, and that contain both clay minerals and calcium carbonate. The burnt nodules were ground to a fine powder. This product, made into a mortar with sand, set in 5–15 minutes. The success of "Roman Cement" led other manufacturers to develop rival products by burning artificial mixtures of clay and chalk.

John Smeaton made an important contribution to the development of cements when he was planning the construction of the third Eddystone Lighthouse (1755–9) in the English Channel. He needed a hydraulic mortar that would set and develop some strength in the twelve hour period between successive high tides. He performed an exhaustive market research on the available hydraulic limes, visiting their production sites, and noted that the "hydraulicity" of the lime was directly related to the clay content of the limestone from which it was made. Smeaton was a civil engineer by profession, and took the idea no further. Apparently unaware of Smeaton's work, the same principle was identified by Louis Vicat in the first decade of the nineteenth century. Vicat went on to devise a method of combining chalk and clay into an intimate mixture, and, burning this, produced an "artificial cement" in 1817. James Frost, working in Britain, produced what he called "British cement" in a similar manner around the same time, but did not obtain a patent until 1822. In 1824, Joseph Aspdin patented a similar material, which he called Portland cement, because the render made from it was in color similar to the prestigious Portland stone.

Setting time and "early strength" are important characteristics of cements. Hydraulic limes, "natural" cements, and "artificial" cements all rely upon their belite content for strength development. Belite develops strength slowly. Because they were burned at temperatures below 1250 °C, they contained no alite, which is responsible for early strength in modern cements. The first cement to consistently contain alite was made by Joseph Aspdin's son William in the early 1840s. This was what we call today "modern" Portland cement. Because of the air of mystery with which William Aspdin surrounded his product, others (e.g., Vicat and I.C. Johnson) have claimed precedence in this invention, but recent analysis[11] of both his concrete and raw cement have shown that William Aspdin's product made at Northfleet, Kent was a true alite-based cement. However, Aspdin's methods were "rule-of-thumb": Vicat is responsible for establishing the chemical basis of these cements, and Johnson established the importance of sintering the mix in the kiln.

William Aspdin's innovation was counterintuitive for manufacturers of "artificial cements", because they required more lime in the mix (a problem for his father), a much higher kiln temperature (and therefore more fuel), and the resulting clinker was very hard and rapidly wore down the millstones, which were the only available grinding technology of the time. Manufacturing costs were therefore considerably higher, but the product set reasonably slowly and developed strength quickly, thus opening up a market for use in concrete. The use of concrete in construction grew rapidly from 1850 onward, and was soon the dominant use for cements. Thus Portland cement began its predominant role.. High Temperature Cement

In the US the first large scale use of cement was Rosendale cement a natural cement mined from a massive deposit of a large dolostone rock deposit discovered in the early 19th century near Rosendale, New York. Rosendale cement was extremely popular for the foundation of buildings (e.g., Statue of Liberty, Capitol Building, Brooklyn Bridge) and lining water pipes. But its long curing time of at least a month made it unpopular after World War One in the construction of highways and bridges and many states and construction firms turned to the use of Portland cement. Because of the switch to Portland cement, by the end of the 1920s of the 15 Rosendale cement companies, only one had survived. But in the early 1930s it was soon discovered that, while Portland cement had a faster setting time it was not as durable, especially for highways, to the point that some states stopped building highways and roads with cement. High Temperature Insulation

 Bertrain H. Wait, an engineer whose company had worked on the construction of the New York Cities Catskill Aqueduct, was impressed with the durability of Rosendale cement, and came up with a blend of both Rosendale and synthetic cements which had the good attributes of both: it was highly durable and had a much faster setting time. Mr. Wait convinced the New York Commissioner of Highways to construct an experimental section of highway near New Paltz, New York, using one sack of Rosendale to six sacks of synthetic cement, and it was proved a success and for decades the Rosendale-synthetic cement blend became common use in highway and bridge construction.

History of the origin of cement


Early uses

It is uncertain where it was first discovered that a combination of hydrated non-hydraulic lime and a pozzolan produces a hydraulic mixture (see also: Pozzolanic reaction), but concrete made from such mixtures was first used by the Ancient Macedonians and three centuries later on a large scale by Roman engineers. High Temperature Cement.

 They used both natural pozzolans (trass or pumice) and artificial pozzolans (ground brick or pottery) in these concretes. Many excellent examples of structures made from these concretes are still standing, notably the huge dome of the Pantheon in Rome and the massive Baths of Caracalla. The vast system of Roman aqueducts also made extensive use of hydraulic cement. High Temperature Insulation

Although any preservation of this knowledge in literary sources from the Middle Ages is unknown, medieval masons and some military engineers maintained an active tradition of using hydraulic cement in structures such as canals, fortresses, harbors, and shipbuilding facilities.The technical knowledge of making hydraulic cement was later formalized by French and British engineers in the 18th century.

Cement



For other uses, see Cement (disambiguation).
Not to be confused with Concrete.


Lafarge cement plant in Contes, France.
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder. The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum, cimentum, cäment, and cement. High Temperature Cement

Cement used in construction is characterized as hydraulic or non-hydraulic. Hydraulic cements (e.g., Portland cement) harden because of hydration, chemical reactions that occur independently of the mixture's water content; they can harden even underwater or when constantly exposed to wet weather. The chemical reaction that results when the anhydrous cement powder is mixed with water produces hydrates that are not water-soluble. Non-hydraulic cements (e.g. gypsum plaster) must be kept dry in order to retain their strength. High Temperature Insulation

The most important uses of cement are as an ingredient in the production of mortar in masonry, and of concrete, a combination of cement and an aggregate to form a strong building material.

วันพฤหัสบดีที่ 21 มีนาคม พ.ศ. 2556

What Is Mastic Adhesive?



Ceramic tile adhesive is mainly available in two forms: mastic and thin set. Mastic adhesive is a premixed adhesive that can be directly applied, while thin set is a powder that must be mixed and left to sit for several minutes before using. The premixed adhesive is applied in areas where moisture will not be an issue, such as backsplashes in kitchens or wall tile. Thin set is applied in bathrooms because it is moisture-resistant. It is not typically used on walls because it takes longer to bond.
Mastic is only suitable for ceramic tile because other types, such as porcelain or marble, are porous. Over time, the adhesive could seep into the tiles and cause them to discolor. Ceramic tile is often used on walls in restaurants and homes. Mastic works well in these applications because it creates an extremely tight bond with the wall. It also sets quickly, which is an advantage when working with vertical designs because the need to stand and hold each tile while it dries is greatly reduced. High Temperature Adhesive

What Is Mastic Adhesive?



Mastic adhesive is made from the sticky resin of the mastic tree, which grows in the Mediterranean. Because of its sticky nature, it is used as a bonding agent in many commercial applications. Some types include construction adhesive, industrial adhesive, and ceramic tileadhesive. Depending on the application, the adhesive is available in thin liquid, thick glue, or paste form.
When used in construction, mastic adhesive is typically in liquid form and applied with a caulking gun. The adhesive is squeezed out by hand in a thin line along wall or ceiling joints. The strength of the adhesive helps hold load-bearing walls in place. In ceilings, the quick-setting adhesive eliminates the need to support heavy drywall for extended periods of time. Construction adhesive is also used as a temporary hold for fixtures so they can be nailed or screwed in place by one person.
Industrial uses for this adhesive include repairing duct work in the heating and air industry. This is due to its heat resistant properties and the ability to seal and form and a strong bond. The adhesive also bonds with most any material, so repairs to concrete, brick, or mortar are also possible. The adhesive for industrial uses comes in a finely ground powder that is mixed to form a paste. It is smeared onto the repair area and allowed to dry.

วันพุธที่ 27 กุมภาพันธ์ พ.ศ. 2556

New method of growing high-quality graphene promising for next-gen technology



New method of growing high-quality graphene promising for next-gen technology (Nanowerk News) Making waves as the material that will revolutionize electronics, graphene – composed of a single layer of Carbon atoms – has nonetheless been challenging to produce in a way that will be practical for innovative electronics applications. Researchers at UC Santa Barbara have discovered a method to synthesize high quality graphene in a controlled manner that may pave the way for next-generation electronics application.


Kaustav Banerjee, a professor with the Electrical and Computer Engineering department and Director of the Nanoelectronics Research Lab at UCSB that has been studying carbon nanomaterials for more than seven years, led the research team to perfect methods of growing sheets of graphene, as detailed in a study to be published in the November 2011 issue of the journal Carbon.

UCSB researchers have successfully controlled the growth of a high-quality bilayer graphene on a copper substrate using a method called chemical vapor deposition (CVD), which breaks down molecules of methane gas to build graphene sheets with carbon atoms. (Image: Peter Allen) "Our process has certain unique advantages that give rise to high quality graphene," says Banerjee. "For the electronics industry to effectively use graphene, it must first be grown selectively and in larger sheets. We have developed a synthesis technique that yields high- quality and high-uniformity graphene that can be translated into a scalable process for industry applications."

Using adhesive tape to lift flakes of graphene from graphite, University of Manchester researchers Geim and Novoselov were awarded the 2010 Nobel Prize in Physics for their pioneering isolation and characterization of the material. To launch graphene into futuristic applications, however, researchers have been seeking a controlled and efficient way to grow a higher quality of this single-atom-thick material in larger areas.

The discovery by UCSB researchers turns graphene production into an industry-friendly process by improving the quality and uniformity of graphene using efficient and reproducible methods. They were able to control the number of graphene layers produced – from mono-layer to bi-layer graphene – an important distinction for future applications in electronics and other technology.

"Intel has a keen interest in graphene due to many possibilities it holds for the next generation of energy- efficient computing, but there are many roadblocks along the way," added Intel Fellow, Shekhar Borkar. "The scalable synthesis technique developed by Professor Banerjee's group at UCSB is an important step forward."

As a material, graphene is the thinnest and strongest in the world – more than 100 times stronger than diamond – and is capable of acting as an ultimate conductor at room temperature. If it can be produced effectively, graphene's properties make it ideal for advancements in green electronics, super strong materials, and medical technology. Graphene could be used to make flexible screens and electronic devices, computers with 1,000 GHz processors that run on virtually no energy, and ultra-efficient solar power cells. Key to the UCSB team's discovery is their understanding of graphene growth kinetics under the influence of the substrate. Their approach uses a method called low pressure chemical vapor deposition (LPCVD) and involves disintegrating the hydrocarbon gas methane at a specific high temperature to build uniform layers of carbon (as graphene) on a pretreated copper substrate. Banerjee's research group established a set of techniques that optimized the uniformity and quality of graphene, while controlling the number of graphene layers they grew on their substrate.

According to Dr. Wei Liu, a post-doctoral researcher and co-author of the study, "Graphene growth is strongly affected by imperfection sites on the copper substrate. By proper treatment of the copper surface and precise selection of the growth parameters, the quality and uniformity of graphene are significantly improved and the number of graphene layers can be controlled."

Professor Banerjee and credited authors Wei Liu, Hong Li, Chuan Xu and Yasin Khatami are not the first research team to make graphene using the CVD method, but they are the first to successfully refine critical methods to grow a high quality of graphene. In the past, a key challenge for the CVD method has been that it yields a lower quality of graphene in terms of carrier mobility – or how well it conducts electrons. "Our graphene exhibits the highest reported field-effect mobility to date for CVD graphene, having an average value of 4000 cm2/V.s with the highest peak value at 5500 cm2/V.s. This is an extremely high value compared with the mobility of silicon." added Hong Li, a Ph.D. candidate in Banerjee's research group.

"Kaustav Banerjee's group is leading graphene nanoelectronics research efforts at UCSB, from material synthesis to device design and circuit exploration. His work has provided our campus with unique and very powerful capabilities," added David Awschalom, Professor of Physics, Electrical and Computer Engineering, and Director of the California NanoSystems Institute (CNSI) at UCSB where Banerjee's laboratory is located. "This new facility has also boosted our opportunities for collaborations across various science and engineering disciplines."

"There is no doubt graphene is a superior material. Intrinsically it is amazing," says Banerjee. "It is up to us, the scientists and engineers, to show how we can use graphene and harness its capabilities. There are challenges in how to grow it, how to transfer or not to transfer and pattern it, and how to tailor its properties for specific applications. But these challenges are fertile grounds for exciting research in the future."

High temperature insulation wool


High-temperature superconductors (abbreviated high-Tc or HTS) are materials that behave as superconductors at unusually high temperatures. The first high-Tc superconductor was discovered in 1986 by IBM researchers Karl Müller and Johannes Bednorz, who were awarded the 1987 Nobel Prize in Physics "for their important break-through in the discovery of superconductivity in ceramic materials".

Whereas "ordinary" or metallic superconductors usually have transition temperatures (temperatures below which they superconduct) of about 30 K (−243.2 °C), HTS superconductors have been observed with transition temperatures as high as 138 K (−135 °C). Until recently, only certain compounds of copper and oxygen (so-called "cuprates") were believed to have HTS properties, and the term high-temperature superconductor was used interchangeably with cuprate superconductor for compounds such as bismuth strontium calcium copper oxide (BSCCO) and yttrium barium copper oxide (YBCO). However, several Iron based compounds (the Iron pnictides) are now known to be superconducting at high temperatures.

วันพฤหัสบดีที่ 31 มกราคม พ.ศ. 2556

Economic importance


Economic importance

In the course of time and during their development, adhesives have gained a stable position in an increasing number of production processes. There is hardly any product in our surroundings that does not contain at least one adhesive – be it the label on a beverage bottle, protective coatings on automobiles or profiles on window frames. Market researchers forecast a turnover of almost US$50 billion for the global adhesives market in 2019. Especially the dynamic economic development in emerging countries such as China, India, Russia or Brazil will cause a rising demand for adhesives in the future.

History Of Adhesive


History Of Adhesive

The oldest known adhesive, dated to approximately 200,000 BC, is from spear stone flakes glued to wood with birch-bark-tar, which was found in central Italy.[4] The use of compound glues to haft stone spears into wood dates back to approximately 70,000 BC. Evidence for this has been found in Sibudu Cave, South Africa and the compound glues used were made from plant gum and red ochre. The Tyrolean Iceman had weapons fixed together with the aid of birch-bark-tar glue.

6000-year-old ceramics show evidence of adhesives based upon animal glues made by rendering animal products such as horse teeth. During the times of Babylonia, tar-like glue was used for gluing statues. The Egyptians made much use of animal glues to adhere furniture, ivory, and papyrus. The Mongols also used adhesives to make their short bows, and the Native Americans of the eastern United States used a mixture of spruce gum and fat as adhesives to fashion waterproof seams in their birchbark canoes.

In medieval Europe, egg whites were used as glue to decorate parchments with gold leaf. The first actual glue factory was founded in Holland in the early 18th century. In the 1750s, the English introduced fish glue. As the modern world evolved, several other patented[clarification needed] materials, such as bones, starch, fish skins and isinglass, and casein, were introduced as alternative materials for glue manufacture. Modern glues have improved flexibility, toughness, curing rate, and chemical resistance.

In the late 19th century in Switzerland, casein was first used as a wood glue. Today, it is used to glue grocery bags.

Adhesive


An adhesive, also known as glue, is a material, typically liquid or semi-liquid, that adheres or bonds items together. Adhesives come from either natural or synthetic sources. The types of materials that can be bonded are vast but adhesives are especially useful for bonding thin materials. Adhesives cure (harden) by either evaporating a solvent or by chemical reactions that occur between two or more constituents.
Adhesives are useful for joining thin or dissimilar materials, minimizing weight, and providing a vibration-damping joint. A disadvantage of most adhesives is that most do not form an instantaneous joint, unlike many other joining processes, because the adhesive needs time to cure.
The earliest known date for a simple glue is 200,000 BC and for a compound glue 70,000 BC.

วันอังคารที่ 22 มกราคม พ.ศ. 2556

Mesh


Mesh
       Mesh consists of semi-permeable barrier made of connected strands of metal, fiber, or other flexible/ductile material. Mesh is similar to web or net in that it has many attached or woven strands Types of mesh A plastic mesh is extruded, oriented, expanded or tubular. Plastic mesh can be made from polypropylene, polyethylene, nylon, PVC or PTFE. A metal mesh can be woven, knitted, welded, expanded, photo-chemically etched or electroformed (screen filter) from steel or other metals.In clothing, a mesh is often defined as a loosely woven or knitted fabric that has a large number of closely spaced holes, frequently used for modern sports jerseys and other clothing. A mesh skin graft is a skin patch that has been cut systematically to create a mesh. Meshing of skin grafts provides coverage of a greater surface area at the recipient site, and also allows for the egress of serous or sanguinous fluid. However, it results in a rather pebbled appearance upon healing that may ultimately look less aesthetically pleasing. Uses of meshes Meshes are often used to screen out unwanted things, such as insects. Wire screens on windows and mosquito netting can be considered as types of meshes. Wire screens can be used to shield against radio frequency radiation, e.g. in microwave ovens and Faraday cages. Metal and nylon wire mesh filters are used in filtration Wire mesh is used in guarding for secure areas and as protection in the form of vandal screens. Wire mesh can be fabricated to produce park benches, waste baskets and other baskets for material handling. A huge quantity of mesh is being used for screen printing work. Surgical mesh is used to provide a reinforcing structure in surgical procedures like inguinal hernioplasty, and umbilical hernia repair. Meshes are also used as drum heads in practice and electronic drum sets.

High temperature insulation


High temperature insulation Calcium silicate
    Calcium silicate (often referred to by its shortened trade name Cal-Sil or Calsil) is the chemical compound Ca2SiO4, also known as calcium orthosilicate and sometimes formulated 2CaO.SiO2. It is one of group of compounds obtained by reacting calcium oxide and silica in various ratios[3] e.g. 3CaO•SiO2, Ca3SiO5; 2CaO•SiO2, Ca2SiO4; 3CaO•2SiO2, Ca3Si2O7 and CaO•SiO2, CaSiO3. Calcium orthosilicate is a white powder with a low bulk density and high physical water absorption. It is used as an anti-caking agent and an antacid. A white free-flowing powder derived from limestone and diatomaceous earth, calcium silicate has no known adverse effects to health[citation needed]. It is used in roads, insulation, bricks, roof tiles, table salt[4] and occurs in cements, where it is known as belite (or in cement chemist notation C2S).


High temperature insulation
   Calcium silicate is commonly used as a safe alternative to asbestos for high temperature insulation materials. Industrial grade piping and equipment insulation is often fabricated from calcium silicate. Its fabrication is a routine part of the curriculum for insulation apprentices. Calcium silicate competes in these realms against rockwool as well as proprietary insulation solids, such as perlite mixture and vermiculite bonded with sodium silicate. Although it is popularly considered an asbestos substitute, early uses of calcium silicate for insulation still made use of asbestos fibers.

Natural adhesives


Natural adhesives
      Natural adhesives are made from organic sources such as vegetable matter, starch (dextrin), natural resins or from animals e.g. casein or animal glue. They are often referred to as bioadhesives. One example is a simple paste made by cooking flour in water. Animal glues are traditionally used in bookbinding, wood joining, and many other areas but now are largely replaced by synthetic glues. Casein is mainly used to adhere glass bottle labels. Starch based adhesives are used in corrugated board production and paper sack production, paper tube winding, and wall paper adhesives. Masonite, a wood hardboard, was bonded using natural lignin, (although most modern MDF particle boards use synthetic thermosetting resins). Another form of natural adhesive is blood albumen (made from protein component of blood), which is used in the plywood industry. Animal glue remains the preferred glue of the luthier. Casein based glues are made by precipitating casein from milk protein using the acetic acid from vinegar. This forms curds, which are neutralized with a base, such as sodium bicarbonate (baking soda), to cause them to unclump and become a thicker plastic-like substance

Synthetic adhesives


Synthetic adhesives
     Synthetic adhesives are based on elastomers, thermoplastics, emulsions, and thermosets. Examples of thermosetting adhesives are: epoxy, polyurethane, cyanoacrylate and acrylic polymers. See also post-it notes. The first commercially produced synthetic adhesive was Karlsons klister in the 1920s.