The key difference between alpha and gamma alumina is that alpha alumina has a very low surface area and is almost non-porous, whereas gamma alumina has a high surface area with some porosity.
Alumina or aluminum oxide nanoparticles are simply a category of metal oxides having high dielectric strength and other thermal properties that can lead to an increased electrical capacity, hardness, and stronger metals and alloys. These nanoparticles are spherical shaped and appear as white powder. Moreover, these particles can be applied in integrated circuits, ceramics, laser crystals, cutting equipment, furnace tubes, polishing materials, etc. Basically, there are two types of particles as alpha and gamma alumina.
What is Alpha Alumina?
Alpha alumina is the alpha form of aluminum oxide. Alpha alumina or alpha aluminum oxide crystallizes in the corundum structure where the oxygen positions approximate to hexagonal close packing and trivalent aluminum cations occupying 2/3rds of the octahedral sites. According to some research studies, the corundum structure and its space group have six formula units in the hexagonal unit cell.
When considering the structure of alpha alumina, it is trigonally structured with the ABAB arrangement of planes of oxygen along the C-way. This substance phases with temperatures ranging from 1050 – 1100 degrees Celsius. According to the X-ray diffraction calculations, alpha alumina has a crystallite shape of about 33 nm. This substance observes its highest surface area of 266 m2/g at 400 degrees Celsius. The lowest surface area can be observed at 1100 degrees Celsius as 5.0 m2/g. The overall pore volume is obtained at 600 degrees Celsius.
Alpha alumina, due to its thermal properties, can be used in the production of plastics, ceramics, and other factory products. It helps in improving the density ratio in ceramics and serves as anti-fatigue thermal resistance. Furthermore, it has a high performance and has many uses in the production of synthetic rubies, aluminum garnets, and other fabrics.
What is Gamma Alumina?
Gamma alumina is the gamma form of aluminum oxide. It has a cubic shape and shows a face-centered cubic structure. The pattern can be given as ABCABC oxygen stacking. In gamma alumina, there are vacant spaces on aluminum (III) posts. It also occupies not only the octahedral positions but also the tetrahedral positions through the level of occupancy that remains a subject of dispute.
Gamma alumina phases with temperatures ranging from 400 to 600 degrees Celsius. According to X-ray diffraction calculations, the crystallite group is in the range of 5.0 to 10.0 nm. This type of alumina has a low melting point at room temperature, and we can use it to manufacture plastic sapphires using thermal melting methods.
Gamma alumina comes in the form of a nanopowder, having a white color, with a purity of 99.97%, and the size ranges from 20 – 30 nm. It is an extensively used material with applications that ranges from absorbents to heterogenous catalysis due to its high surface area and acidic surface properties.
What is the Difference Between Alpha and Gamma Alumina?
Alpha and gamma alumina are important polymorphic structures of alumina. The key difference between alpha and gamma alumina is that alpha alumina has a very low surface area and is almost non-porous, whereas gamma alumina has a high surface area with some porosity. Moreover, alpha alumina is amorphous while gamma alumina is acidic.
The below infographic presents the differences between alpha and gamma alumina in tabular form for side-by-side comparison.
Summary – Alpha vs Gamma Alumina
Alpha alumina is the alpha form of aluminum oxide, while gamma alumina is the gamma form of aluminum oxide. The key difference between alpha and gamma alumina is that alpha alumina has a very low surface area, and it is almost non-porous, whereas gamma alumina has a high surface area with some porosity.
1. “Alpha-Aluminium Oxide.” An Overview | ScienceDirect Topics.