Alumina Specific Heat Capacity and Thermal Conductivity

Alumina boasts superior thermal and electrical insulating properties, making it suitable for high temperature environments such as those found in X-ray components, high voltage bushings, as well as special crucibles used in both metallurgical and chemical processes.

Alumina can exist in several structural phases, but most often returns to its hexagonal alpha phase at elevated temperatures. This material features high strength, hardness and corrosion and wear resistance properties.

Specific Heat

The specific heat of a material measures the amount of energy (measured in joules) necessary to raise its temperature by one degree Kelvin. This property is invaluable when designing applications involving temperature changes; designers can use specific heat values to predict how a material will respond. Alumina boasts an exceptionally high specific heat, meaning that less energy is required than with other materials to raise its temperature, making it suitable for heat transfer applications.

To understand how the specific heat of alumina varies with temperature, we conducted measurements using a Quantum Design Physical Properties Measurement System at various temperatures from 300 to 1200 degC and collected data over the range from 300-1200 degC using functional forms to determine its entropy, enthalpy, Gibbs energy functions and molecular structure. Its specific heat was found to depend significantly on both storage temperature and storage duration and was closely related with both its a-phase fraction (a-f) as well as porosity.

Corundum alumina’s specific heat is well-documented and often used as a reference point in calorimetric calibration; however, information on gamma phase alumina remains scarce due to its many different structural phases, each with their own thermodynamic properties that vary depending on its synthetic method and catalyst preparation method. Furthermore, water from catalytic preparation tends to bind tightly with this phase, further complicating data collection for thermodynamic studies.

As part of an effort to expand this measurement, we conducted studies on the specific heat and other thermodynamic properties of silica-doped gamma phase aluminas synthesized through either an inorganic or organic route, including their rheological behavior and isobaric specific heat measurements of pure alumina and its mixture with water; Newtonian behavior can be observed even at high concentrations of alumina-water mixtures; no viscosity hysteresis has been observed at any concentration;

Θερμική αγωγιμότητα

Alumina boasts a high thermal conductivity, meaning it quickly transfers heat through its material. This is thanks to the material’s structure – including strong network of crystals and porous granules – as well as other factors including lattice arrangement, mineralogical composition and pore connectivity of its granules; temperature can also impact this parameter as free electron movement affects molecular vibration and energy transfer processes within them. Thermal conductivity measurements in Watts per Meter Kelvin-1 are taken for every material temperature gradient difference measured over 1K-1

Thermal diffusivity of alumina is directly proportional to its thermal conductivity; thus as its conductivity increases, thermal diffusion decreases. Fourier’s law can be used to calculate its thermal conductivity; heat transfer rates are determined by subtracting temperature gradient from product of thermal diffusivity and material density; both these measurements are reported in Wm-1K-1 units for comparison between materials.

To understand alumina’s thermal properties and effectively use it as catalyst support material, corundum is usually considered the primary form of alumina; many thermodynamic measurements have been conducted on this material; however, less data exists regarding other structural phases like alpha or gamma forms of alumina which could prove more valuable for catalyst support applications.

Alumina thermal conductivity (TC) is inextricably tied to its calcination temperature, and may vary based on factors like its microstructure and porosity. Furthermore, moisture can significantly impact its TC; wet material tends to exhibit higher TC than dry unsoaked material due to increased vapor pressure which raises boiling and melting points; but when dried without moisture present its TC will remain relatively constant regardless of its calcination temperature.

Thermal Insulation

Alumina ceramic insulation is an exceptionally versatile engineering material used in various industrial applications. Its excellent abrasion resistance, corrosion resistance and thermal stability make it a fantastic material to use as insulation in crucibles, thermocouple protection systems or advanced ceramic tubes. Furthermore, understanding these physical characteristics will enable users to select appropriate materials for their particular purposes.

As alumina’s specific heat and thermal conductivity can vary based on its calcination temperature and water content, for accurate results it is vitally important that equipment be calibrated against standard samples in order to understand how such variations impact its performance and ensure measurements are precise. To do so accurately and reliably.

Corundum alumina has long been used for calibration since the early 20th century, but other forms of alumina may vary widely in their chemical composition and physical properties. Below are tables which outline some variations among them and how they relate to overall characteristics of alumina.

Recent years have seen an explosion of research into alumina-based aerogels, specifically their application as high temperature insulation and energy storage technologies. Alumina aerogels possess higher thermal conductivities than silica aerogels while still being capable of maintaining their high porosity and pore texture at elevated temperatures. To enhance mechanical and high temperature insulating performance further, reinforcement with ceramic fibers or whiskers has also proven successful, increasing both their compressive strengths as well as thermal conductivity properties.

As previously discussed, zirconia whisker-modified alumina-silica aerogel composites have demonstrated significant reductions in their permeability at 1000 degC due to their high specific heat value, making these an excellent combination of thermal and mechanical properties for high temperature applications.

Though alumina provides impressive thermal insulation and mechanical properties, its susceptibility to thermal shock must also be taken into account. Careful handling can avoid damage to the material and ensure its long-term efficacy in demanding environments by gradually heating and cooling rates, and preventing overheating or undercooling.

Δύναμη

Alumina is one of the strongest engineering ceramics, boasting a hardness rating just behind diamond and tungsten carbide on the Mohs scale of hardness. This strength allows alumina to withstand mechanical wear-and-abrasion damage as well as heat from high-powered arc welding equipment and has excellent chemical resistance properties that extend its lifespan in processing environments with high amounts of contaminants such as corrosion.

Strength of Alumina Ceramics grows with their purity. Fewer voids mean more material can be packed together more tightly, increasing density. Due to this higher level of density, Alumina ceramics remain highly thermally resistant at higher temperatures without suffering thermal shock as easily.

Alumina’s stability at high temperatures contributes to its remarkable durability. Resistant to abrasion and impact damage, as well as capable of stopping small arms fire and medium caliber projectiles, its toughness can be enhanced using zirconia particles or silicon-carbide whiskers to enhance industrial cutting tool functionality. Furthermore, adding small amounts of magnesia can make its typically opaque ceramic become translucent.

Alumina’s low coefficient of thermal expansion makes it ideal for use in high-temperature applications, including sintering furnaces and kilns, where intensive pressure and temperatures exist. Its strong atomic bonds withstand these environments without straining, helping prevent warping or damage of the material in question.

94% alumina has excellent compressive and flexural strengths, hermeticity, and wear resistance; therefore it can be used in applications such as pressure sensors, insulators for sputtering targets and electron tubes, high voltage bushings and medical implants – it even can be made into ergonomic body armor for military vehicles and structures!

Harper International provides advanced ceramic shapes with its alumina sintering presses and systems, providing accurate control of pressure, speed, stroke, adjustable residence times and advanced automation features for producing dense alumina ceramic shapes in controlled environments. Harper offers advanced sintering presses that meet these specifications to produce ceramic products of desired density in controlled conditions.