Macor

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Macor is the trademark for a machineable glass-ceramic developed and sold by Corning Inc. It is a white material that looks somewhat like porcelain. Macor is a good thermal insulator and is stable up to temperatures of 1000 °C, with very little thermal expansion or outgassing. It can be machined using standard metalworking tools. [1]

Machining process in which a piece of raw material is cut into a desired final shape and size by a controlled material-removal process; manufacturing process

Machining is any of various processes in which a piece of raw material is cut into a desired final shape and size by a controlled material-removal process. The processes that have this common theme, controlled material removal, are today collectively known as subtractive manufacturing, in distinction from processes of controlled material addition, which are known as additive manufacturing. Exactly what the "controlled" part of the definition implies can vary, but it almost always implies the use of machine tools.

Glass-ceramics have an amorphous phase and one or more crystalline phases and are produced by a so-called "controlled crystallization" in contrast to a spontaneous crystallization, which is usually not wanted in glass manufacturing. Glass-ceramics have the fabrication advantage of glass, as well as special properties of ceramics. When used for sealing, some glass-ceramics do not require brazing but can withstand brazing temperatures up to 700 °C. Glass-ceramics usually have between 30% [m/m] and 90% [m/m] crystallinity and yield an array of materials with interesting properties like zero porosity, high strength, toughness, translucency or opacity, pigmentation, opalescence, low or even negative thermal expansion, high temperature stability, fluorescence, machinability, ferromagnetism, resorbability or high chemical durability, biocompatibility, bioactivity, ion conductivity, superconductivity, isolation capabilities, low dielectric constant and loss, high resistivity and break-down voltage. These properties can be tailored by controlling the base-glass composition and by controlled heat treatment/crystallization of base glass. In manufacturing, glass-ceramics are valued for having the strength of ceramic but the hermetic sealing properties of glass.

Corning Inc. American manufacturer of glass & ceramics

Corning Incorporated is an American multinational technology company that specializes in specialty glass, ceramics, and related materials and technologies including advanced optics, primarily for industrial and scientific applications. The company was named Corning Glass Works until 1989. Corning divested its consumer product lines in 1998 by selling the Corning Consumer Products Company subsidiary to Borden, but still holds an interest of about 8 percent.

Contents

Composition

Macor is made up of fluorphlogopite mica in a borosilicate glass matrix. Its composition is roughly: 46% silica (SiO2), 17% magnesium oxide (MgO), 16% aluminium oxide (Al2O3), 10% potassium oxide (K2O), 7% boron trioxide (B2O3), 4% fluorine (F). [2]

Phlogopite true mica, phyllosilicate mineral

Phlogopite is a yellow, greenish, or reddish-brown member of the mica family of phyllosilicates. It is also known as magnesium mica.

Borosilicate glass type of glass with silica and boron trioxide as the main glass-forming constituents

Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. Borosilicate glasses are known for having very low coefficients of thermal expansion, making them resistant to thermal shock, more so than any other common glass. Such glass is less subject to thermal stress and is commonly used for the construction of reagent bottles. Borosilicate glass is sold under such trade names as Borcam, Borosil, DURAN, Suprax, Simax, BSA 60, BSC 51, Heatex, Endural, Schott, Refmex, Kimble, MG(India) and some items sold under different trade names.

Magnesium oxide chemical compound

Magnesium oxide (MgO), or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium (see also oxide). It has an empirical formula of MgO and consists of a lattice of Mg2+ ions and O2− ions held together by ionic bonding. Magnesium hydroxide forms in the presence of water (MgO + H2O → Mg(OH)2), but it can be reversed by heating it to separate moisture.

Properties

Macor has a density of 2.52 g/cm3, [3] a Young's modulus of 66.9 GPa at 25 °C, [3] a specific stiffness of 26.55×106 m2s−2, a Poisson’s Ratio of 0.29 [3] and a thermal conductivity of 1.46 W/(m·K). [3] It has a low-temperature (25 to 300 °C) thermal expansion of 9.3×10−6 K−1. [3] Its compressive strength is 50×103 lb/in2 (~350 MPa). [3] Nominal engineering properties are comparable to borosilicate glass. [4]

The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is ρ, although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume:

Young's modulus or Young modulus is a mechanical property that measures the stiffness of a solid material. It defines the relationship between stress and strain in a material in the linear elasticity regime of a uniaxial deformation.

Pascal (unit) SI unit of pressure

The pascal is the SI derived unit of pressure used to quantify internal pressure, stress, Young's modulus and ultimate tensile strength. It is defined as one newton per square metre. It is named after the French polymath Blaise Pascal.

Extremely machinable, Macor offers tight-tolerance capabilities, allowing complicated shape design (optimal performances up to ±0.013 mm for dimensions, < 0.5 μm for finished surface and up to 0.013 μm for polished surface). Macor remains continuously stable at 800 °C, with a maximum peak at 1000 °C under no load, and unlike ductile materials, doesn’t creep or deform. Its coefficient of thermal expansion readily matches most metals and sealing glasses. As an electric insulator, particularly at high temperatures, it is excellent at high voltages and a broad spectrum of frequencies.

Macor comes in a standard size maxi slab (about 36 cm × 36 cm × 6cm). [5] Components, bars, rods and plates can be machined within the size of this slab (hand tools can be used).

Applications

Macor is used in the following applications:

Safety

There are no major safety concerns or toxic effects associated with Macor. The dust created when machining it can be an irritant, and inhalation should be avoided. [6]

Safety state of being secure from harm, injury, danger or risk

Safety is the state of being "safe", the condition of being protected from harm or other non-desirable outcomes. Safety can also refer to the control of recognized hazards in order to achieve an acceptable level of risk.

Dust small particles in the air

Dust are fine particles of solid matter. It generally consists of particles in the atmosphere that come from various sources such as soil, dust lifted by wind, volcanic eruptions, and pollution. Dust in homes, offices, and other human environments contains small amounts of plant pollen, human and animal hairs, textile fibers, paper fibers, minerals from outdoor soil, human skin cells, burnt meteorite particles, and many other materials which may be found in the local environment.

Irritation, in biology and physiology, is a state of inflammation or painful reaction to allergy or cell-lining damage. A stimulus or agent which induces the state of irritation is an irritant. Irritants are typically thought of as chemical agents but mechanical, thermal (heat), and radiative stimuli can also be irritants. Irritation also has non-clinical usages referring to bothersome physical or psychological pain or discomfort.

Machining guidelines

Key factors for successful machining are proper machining speeds and coolant. Macor can be machined with high-speed steel tools, but carbide tools are recommended for longer wear. Best results achieved by using a water-soluble coolant (such as Cimstar 40 – Pink) especially formulated for cutting and grinding glass or ceramics. Note: No post-firing is required after machining.

High-speed steel subset of tool steels

High-speed steel is a subset of tool steels, commonly used as cutting tool material.

Tungsten carbide chemical compound

Tungsten carbide is a chemical compound containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into shapes through a process called sintering for use in industrial machinery, cutting tools, abrasives, armor-piercing rounds, other tools and instruments, and jewelry.

Related Research Articles

Ceramic inorganic, nonmetallic solid prepared by the action of heat

A ceramic is a solid material comprising an inorganic compound of metal, non-metal or metalloid atoms primarily held in ionic and covalent bonds. Common examples are earthenware, porcelain, and brick.

Glass fiber Material consisting of numerous extremely fine fibers of glass

Glass fiber is a material consisting of numerous extremely fine fibers of glass.

Pyrex trademark for borosilicate glass

Pyrex is a brand introduced by Corning Inc. in 1915 for a line of clear, low-thermal-expansion borosilicate glass used for laboratory glassware and kitchenware. It was later expanded to include clear and opal ware products made of soda-lime glass.

Fused quartz fused silica

Fused quartz or fused silica is glass consisting of silica in amorphous (non-crystalline) form. It differs from traditional glasses in containing no other ingredients, which are typically added to glass to lower the melt temperature. Fused silica, therefore, has high working and melting temperatures. Although the terms fused quartz and fused silica are used interchangeably, the optical and thermal properties of fused silica are superior to those of fused quartz and other types of glass due to its purity. For these reasons, it finds use in situations such as semiconductor fabrication and laboratory equipment. It transmits ultraviolet better than other glasses, so is used to make lenses and optics for the ultraviolet spectrum. The low coefficient of thermal expansion of fused quartz makes it a useful material for precision mirror substrates.

Transparent ceramics

Many ceramic materials, both glassy and crystalline, have found use as optically transparent materials in various forms from bulk solid-state components to high surface area forms such as thin films, coatings, and fibers. Such devices have found widespread use for various applications in the electro-optical field including: optical fibers for guided lightwave transmission, optical switches, laser amplifiers and lenses, hosts for solid-state lasers and optical window materials for gas lasers, and infrared (IR) heat seeking devices for missile guidance systems and IR night vision.

Solid oxide fuel cell fuel cell that has a ceramic electrolyte

A solid oxide fuel cell is an electrochemical conversion device that produces electricity directly from oxidizing a fuel. Fuel cells are characterized by their electrolyte material; the SOFC has a solid oxide or ceramic electrolyte.

Vycor is the brand name of Corning's high-silica, high-temperature glass. It provides very high thermal shock resistance. Vycor is approximately 96% silica and 4% boron trioxide, but unlike pure fused silica, it can be readily manufactured in a variety of shapes.

Beryllium oxide chemical compound

Beryllium oxide (BeO), also known as beryllia, is an inorganic compound with the formula BeO. This colourless solid is a notable electrical insulator with a higher thermal conductivity than any other non-metal except diamond, and exceeds that of most metals. As an amorphous solid, beryllium oxide is white. Its high melting point leads to its use as a refractory material. It occurs in nature as the mineral bromellite. Historically and in materials science, beryllium oxide was called glucina or glucinium oxide. Formation of BeO from beryllium and oxygen releases the highest energy per mass of reactants for any chemical reaction, close to 24 MJ/kg.

Aluminosilicate

Aluminosilicate minerals are minerals composed of aluminium, silicon, and oxygen, plus countercations. They are a major component of kaolin and other clay minerals.

Soda–lime glass

Soda–lime glass, also called soda–lime–silica glass, is the most prevalent type of glass, used for windowpanes and glass containers for beverages, food, and some commodity items. Glass bakeware is often made of borosilicate glass. Soda–lime glass accounts for about 90% of manufactured glass.

Thermal barrier coating Thermal barrier coating

Thermal barrier coatings (TBC) are advanced materials systems usually applied to metallic surfaces, such as on gas turbine or aero-engine parts, operating at elevated temperatures, as a form of exhaust heat management. These 100 μm to 2 mm coatings serve to insulate components from large and prolonged heat loads by utilizing thermally insulating materials which can sustain an appreciable temperature difference between the load-bearing alloys and the coating surface. In doing so, these coatings can allow for higher operating temperatures while limiting the thermal exposure of structural components, extending part life by reducing oxidation and thermal fatigue. In conjunction with active film cooling, TBCs permit working fluid temperatures higher than the melting point of the metal airfoil in some turbine applications. Due to increasing demand for higher engine operation, better durability/lifetime, and thinner coatings to reduce parasitic weight for rotating/moving components, there is significant motivation to develop new and advanced TBCs.

Zerodur trademark

Zerodur, a registered trademark of Schott AG, is a lithium-aluminosilicate glass-ceramic produced by Schott AG since 1968. It has been used for a number of very large telescope mirrors including Keck I, Keck II, and SOFIA, as well as some smaller telescopes. With its very low coefficient of thermal expansion it can be used to produce mirrors that retain acceptable figures in extremely cold environments such as deep space. Although it has advantages for applications requiring a coefficient of thermal expansion less than that of borosilicate glass, it remains very expensive as compared to borosilicate. The tight tolerance on CTE, ±0.007×106 K−1, allows highly accurate applications that require high-precision.

Ultra low expansion glass (ULE) is a registered trademark of Corning Incorporated. ULE has a very low coefficient of thermal expansion and contains as components silica and less than 10% titanium dioxide. Such high resistance to thermal expansion makes it very resistant to high temperature thermal shock. ULE has been made by Corning since the 1960s, but is still very important to current applications.

Glass-to-metal seal

Glass-to-metal seals are a very important element of the construction of vacuum tubes, electric discharge tubes, incandescent light bulbs, glass encapsulated semiconductor diodes, reed switches, pressure tight glass windows in metal cases, and metal or ceramic packages of electronic components.

Solid solid object

Solid is one of the four fundamental states of matter. In solids particles are closely packed. It is characterized by structural rigidity and resistance to changes of shape or volume. Unlike liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a gas does. The atoms in a solid are tightly bound to each other, either in a regular geometric lattice or irregularly. Solids cannot be compressed with little pressure whereas gases can be compressed with little pressure because in gases molecules are loosely packed.

Anodic bonding is a wafer bonding process to seal glass to either silicon or metal without introducing an intermediate layer; it is commonly used to seal glass to silicon wafers in electronics and microfluidics. This bonding technique, also known as field assisted bonding or electrostatic sealing, is mostly used for connecting silicon/glass and metal/glass through electric fields. The requirements for anodic bonding are clean and even wafer surfaces and atomic contact between the bonding substrates through a sufficiently powerful electrostatic field. Also necessary is the use of borosilicate glass containing a high concentration of alkali ions. The coefficient of thermal expansion (CTE) of the processed glass needs to be similar to those of the bonding partner.

Glass frit bonding, also referred to as glass soldering or seal glass bonding, describes a wafer bonding technique with an intermediate glass layer. It is a widely used encapsulation technology for surface micro-machined structures, e.g., accelerometers or gyroscopes. This technique utilizes low melting glass and therefore provides various advantages including that viscosity of glass decreases with an increase of temperature. The viscous flow of glass has effects to compensate and planarize surface irregularities, convenient for bonding wafers with a high roughness due to plasma etching or deposition. A low viscosity promotes hermetically sealed encapsulation of structures based on a better adaption of the structured shapes. Further, the coefficient of thermal expansion (CTE) of the glass material is adapted to silicon. This results in low stress in the bonded wafer pair.

Visions is a brand of transparent stove top cookware created by Corning France and introduced to Europe during the late 1970s. In 1983, it was introduced in the United States and became the number one selling cookware set for a number of years. Visions is made of Calexium, a transparent material belonging to the Pyroceram family of glass-ceramics. It is one of the few cookware lines than can be used on the range, in the oven, and under a broiler. It will withstand heat up to 850 °C (1,560 °F) with thermal traits similar to Corning Ware plus improved resistance to staining and the detrimental effects of acids and detergents. Visions is sold worldwide by Corelle Brands, LLC.

References

  1. "Macor Machinable Glass".
  2. "MACOR Brochure" (PDF).
  3. 1 2 3 4 5 6
  4. Compare Materials: Borosilicate Glass and Macor.
  5. Corning Macor Maxi-Slab.
  6. "Macor Glass Ceramic".