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| Term | Definition | |
| ceramic | Poly-crystalline material produced by sintering. | |
| constant of proportionality | In thermodynamic law, the constant of proportionality (or the Stefan-Boltzmann constant) is denoted in formulas by the Greek letter σ in the Stefan-Boltzmann law, which states that the energy radiated for a unit of surface area of a blackbody in unit time is proportional to the fourth power of the thermodynamic temperature. This constant is used by infrared pyrometer to calculate the surface temperature of a remote object. | |
| dielectric loss | The dielectric loss is the power lost in a microwave due to heating as a wave passes through a specific material. Some materials absorb microwaves, some reflect them, and others are somewhat transparent allowing the wave to pass through unempeded. The dielectric loss is often expressed as dielectric loss tangent or loss factor, and low loss makes for a good dielectric while high loss is an absorber or poor dielectric. In a microwave sintering oven, it is important that the crucible be a good dielectric material easily allowing microwaves to pass through, but the susceptor plate needs to be a poor dielectric. | |
| emissivity | Emissivity is the ratio of the energy radiated by an object at a given temperature to the energy emitted by a perfect radiator (a black body) at the same temperature. All radiation energy must be either emitted (E) due to the temperature of the body, transmitted (T) or reflected (R). The emissivity of a blackbody is 1.0, producing no transmitted or reflected energy radiation. Zirconia is highly emissive (typically in the 0.94 to 0.95 range) which makes it fairly easy to obtain an accurate remote temperature measurement using an infrared pyrometer. Materials with low emissivities (<0.2) can be very difficult upon which to get a reading, as are polished or shiny metallic surfaces that are high reflective (R) in the infrared spectrum. | |
| infrared pyrometer | A device that remotely senses infrared radiation being emitted from an object, and determines the termperature of that object\'s surface. | |
| Kanthal | Kanthal is the name of a company AND the name of a special alloy of iron, chromium (20-30 %) and aluminium (4-7.5 %). Kanthal, the alloy, was developed by Hans von Kantzow in Hallstahammar, Sweden, it\'s name being derived from Kantzow and Hallstahammar. The alloy is used in heating elements and is known for its ability to withstand fairly high temperatures with great electric resistance. Ordinary Kanthal has a melting point of 1200 °C, and special grades have a melting point as high as 1425°C, both of which are too low for sintering of zirconia. Kanthal is also the largest maker of molybdenum disilicide heating elements, which are capable of sintering zirconia, but have the adverse affect of discoloring the zirconia in the course of sintering. | |
| microwave crucible | Microwave crucibles are made of a light low density insulating material with a very low dielectric loss, designed to allow microwave energy to easily pass through the material, but radiating the heat generated inside back to the objects being sintered. | |
| molybdenum disilicide | Molybdenum disilicide (MoSi2) is a ceramic compound, a silicide of molybdenum, primarily used as heating elements in conventional sintering furnaces. It has a melting point of 2030°C and is electrically conductive, and is mainly sold under the Kanthal brand. Use of molybdenum disilicide as a heating elements in a dental zirconia furnace can cause a discoloration of the sintered coping or substructure. | |
| silicon carbide | Silicon carbide (SiC) is a ceramic compound made of silicon and carbon, used by industrial microwave furnaces as a susceptor material to speed radiant heating in the ramp-up stages of sintering, and to moderate the cooling stages. The microSinterWave dental ovens use a high temperature formulation of silicon carbide which remains effective and stable at temperatures of 1600°C, manufactured by combining silica sand and carbon in a high temperature graphite electric resistance furnace.. | |
| sintering | Densification of powders by heating | |
| Stefan-Boltzmann constant | The Stefan-Boltzmann constant (also Stefan\'s constant), a physical constant denoted by the Greek letter σ, is the constant of proportionality in the Stefan-Boltzmann law: the total energy radiated per unit surface area of a black body in unit time is proportional to the fourth power of the thermodynamic temperature. This constant is used by infrared pyrometer to calculate the surface temperature of a remote object. | |
| Stefan\'s constant | The Stefan-Boltzmann constant is denoted in formulas by the Greek letter σ, and is the constant of proportionality in the Stefan-Boltzmann law, which states that the energy radiated for a unit of surface area of a blackbody in unit time is proportional to the fourth power of the thermodynamic temperature. This constant is used by infrared pyrometer to calculate the surface temperature of a remote object. | |
| susceptor | A susceptor is a material which easily absorbs microwave radiation and converts it to heat. Susceptors are used in industrial heating processes and occasionally even in home cooking. In home microwaves, the grey paper susceptor material in the sleeve around a Hot Pocket frozen entree gets to high termperatures very quickly and radiates heat on the food effectively browning the outside with infrared energy while the microwaves more deeply penetrate and cook the inside. The same principles apply to microwave sintering of dental ceramics, where copings are placed on a susceptor plate made of silicon carbide inside a crucible that contains silicon carbide flakes, both designed to radiate infrared heat onto the samples. The susceptors quickly get the dental ceramics up to a temperature where they can directly couple with the microwave energy to complete the sintering process (Zirconia couples with microwaves at about 1000ºC). | |
| Yttrium | (Y) metal - atomic number 39, included in the rare earth group. | |
| Zirconia | ZrO2 - zirconium oxide | |
| Zirconium | Zr - white metal - atomic number 40, density 6.51 | |
| Definition | ||
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