MACOR
Encyclopedia
MACOR is a machineable
glass-ceramic
developed and sold by Corning Incorporated. It is a white material that looks somewhat like porcelain
. MACOR has excellent thermal characteristics, acting as efficient insulation
, and stable up to temperatures of 1000 °C, with very little thermal expansion
or outgassing. It can be machined into any desired shape using standard metalworking
bits and tools. This combination of machineability and good thermal properties have made it the material of choice in many engineering
contexts.
in a borosilicate glass
matrix. Its composition is roughly:
of 2.52 g/cm3, and a thermal conductivity
of 1.46 W/(m·K). Its low-temperature (25 to 300 °C) thermal expansion
is 93×10-7 m/(m·K). Its compressive strength is 50×103 lb/in2. Nominal engineering properties are comparable to borosilicate glass
.
MACOR is a very good insulator with excellent tolerance. Even with temperature changes, its low thermal expansion ensures that its shape changes very little.
concerns or toxic effects associated with MACOR. Its excellent temperature stability makes it safe in most situations. The dust
created when machining it can be an irritant
and inhalation should of course be avoided.
MACOR can burn/explode in oxygen under extremely high temperatures, or very rapid temperature changes. The flame is usually quite bright (risk of blinding), but usually extinguishes rapidly.
, nuclear engineering
, medicine
, and fundamental research. It is often used in high-temperature and/or high-vacuum
environments, where dimensional stability and low outgassing are critical.
Machining
Conventional machining is a form of subtractive manufacturing, in which a collection of material-working processes utilizing power-driven machine tools, such as saws, lathes, milling machines, and drill presses, are used with a sharp cutting tool to physical remove material to achieve a desired...
glass-ceramic
Glass-ceramic
Glass-ceramics are polycrystalline material produced through controlled crystallization of base glass. Glass-ceramic materials share many properties with both glasses and ceramics...
developed and sold by Corning Incorporated. It is a white material that looks somewhat like porcelain
Porcelain
Porcelain is a ceramic material made by heating raw materials, generally including clay in the form of kaolin, in a kiln to temperatures between and...
. MACOR has excellent thermal characteristics, acting as efficient insulation
Thermal insulation
Thermal insulation is the reduction of the effects of the various processes of heat transfer between objects in thermal contact or in range of radiative influence. Heat transfer is the transfer of thermal energy between objects of differing temperature...
, and stable up to temperatures of 1000 °C, with very little thermal expansion
Thermal expansion
Thermal expansion is the tendency of matter to change in volume in response to a change in temperature.When a substance is heated, its particles begin moving more and thus usually maintain a greater average separation. Materials which contract with increasing temperature are rare; this effect is...
or outgassing. It can be machined into any desired shape using standard metalworking
Metalworking
Metalworking is the process of working with metals to create individual parts, assemblies, or large scale structures. The term covers a wide range of work from large ships and bridges to precise engine parts and delicate jewelry. It therefore includes a correspondingly wide range of skills,...
bits and tools. This combination of machineability and good thermal properties have made it the material of choice in many engineering
Engineering
Engineering is the discipline, art, skill and profession of acquiring and applying scientific, mathematical, economic, social, and practical knowledge, in order to design and build structures, machines, devices, systems, materials and processes that safely realize improvements to the lives of...
contexts.
Composition
MACOR is made up of fluorphlogopite micaMica
The mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, and are similar in chemical composition...
in a borosilicate glass
Borosilicate glass
Borosilicate glass is a type of glass with the main glass-forming constituents silica and boron oxide. 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...
matrix. Its composition is roughly:
- 46% silica (SiO2)
- 17% magnesiumMagnesiumMagnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
(MgO) - 16% aluminium oxideAluminium oxideAluminium oxide is an amphoteric oxide with the chemical formula 23. It is commonly referred to as alumina, or corundum in its crystalline form, as well as many other names, reflecting its widespread occurrence in nature and industry...
(Al2O3) - 10% potassiumPotassiumPotassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
(K2O) - 7% boronBoronBoron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...
(B2O3) - 4% fluorineFluorineFluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...
(F)
Properties
MACOR has a densityDensity
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...
of 2.52 g/cm3, and a thermal conductivity
Thermal conductivity
In physics, thermal conductivity, k, is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction....
of 1.46 W/(m·K). Its low-temperature (25 to 300 °C) thermal expansion
Thermal expansion
Thermal expansion is the tendency of matter to change in volume in response to a change in temperature.When a substance is heated, its particles begin moving more and thus usually maintain a greater average separation. Materials which contract with increasing temperature are rare; this effect is...
is 93×10-7 m/(m·K). Its compressive strength is 50×103 lb/in2. Nominal engineering properties are comparable to borosilicate glass
Borosilicate glass
Borosilicate glass is a type of glass with the main glass-forming constituents silica and boron oxide. 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...
.
MACOR is a very good insulator with excellent tolerance. Even with temperature changes, its low thermal expansion ensures that its shape changes very little.
Safety
There are no major safetySafety
Safety is the state of being "safe" , the condition of being protected against physical, social, spiritual, financial, political, emotional, occupational, psychological, educational or other types or consequences of failure, damage, error, accidents, harm or any other event which could be...
concerns or toxic effects associated with MACOR. Its excellent temperature stability makes it safe in most situations. The dust
Dust
Dust consists of particles in the atmosphere that arise from various sources such as soil dust lifted up by wind , volcanic eruptions, and pollution...
created when machining it can be an irritant
Irritation
Irritation or exacerbation, 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...
and inhalation should of course be avoided.
MACOR can burn/explode in oxygen under extremely high temperatures, or very rapid temperature changes. The flame is usually quite bright (risk of blinding), but usually extinguishes rapidly.
Applications
MACOR is used in a wide variety of industries, including aerospaceAerospace
Aerospace comprises the atmosphere of Earth and surrounding space. Typically the term is used to refer to the industry that researches, designs, manufactures, operates, and maintains vehicles moving through air and space...
, nuclear engineering
Nuclear engineering
Nuclear engineering is the branch of engineering concerned with the application of the breakdown as well as the fusion of atomic nuclei and/or the application of other sub-atomic physics, based on the principles of nuclear physics...
, medicine
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
, and fundamental research. It is often used in high-temperature and/or high-vacuum
Vacuum
In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in...
environments, where dimensional stability and low outgassing are critical.