Alumina

Alumina

Alumina

  • 1 alumina окись алюминия, глинозём, Al₂O₃@alpha aluminaальфа-окись алюминия, корунд, сапфир@beta aluminaбета-окись алюминия@bonded aluminaсвязанная окись алюминия@foamed aluminaвспененная окись алюминия, пенокерамика из окиси алюминия@fused aluminaплавленая окись алюминия, плавленая керамика из окиси алюминия@gamma aluminaгамма-окись алюминия@high-temperature polycrystalline aluminaжаростойкая поликристаллическая керамика на основе окиси алюминия@hydrated aluminaгидратированная окись алюминия, Al₂O₃ • H₂O@molybdenum-disilicide aluminaкерамика на основе окиси алюминия и дисилицида молибдена@polycrystalline aluminaполикристаллическая окись алюминия@single crystal aluminaмонокристаллическая окись алюминия@sintered aluminaспечённая окись алюминия, спечённая керамика из окиси алюминия@ Англо-русский словарь по авиационно-космическим материалам
  • 2 alumina о/кись алюми/ния, глинозём Al2O3alpha alumina — а/льфа-о/кись алюми/нияbeta alumina — бе/та-о/кись алюми/нияbonded alumina — свя/занная о/кись алюми/нияfoamed alumina — вспе/ненная о/кись алюми/ния, пе/нокера/мика из о/киси алюми/нияfused alumina — пла/вленая о/кись алюми/ния, пла/вленая кера/мика из о/киси алюми/нияgamma alumina — га/мма-о/кись алюми/нияhigh-temperature polycrystalline alumina — жаросто/йкая поликристалли/ческая кера/мика на осно/ве о/киси алюми/нияhydrated alumina — гидрати/рованная о/кись алюми/ния Al2O3 x H2Omolybdenum-disilicide alumina — кера/мика на осно/ве о/киси алюми/ния и дисилици/да молибде/наpolycrystalline alumina — поликристалли/ческая о/кись алюми/нияsingle crystal alumina — монокристалли/ческая о/кись алюми/нияsintered alumina — спечённая о/кись алюми/ния, спечённая кера/мика из о/киси алюми/нияEnglish-Russian dictionary of aviation and space materials
  • 3 aluminaEnglsh-Russian aviation and space dictionary
  • 4 aluminaАнгло-русский словарь технических терминов
  • 5 aluminaEnglish-Russian dictionary of mechanical engineering and automation
  • 6 aluminaactivated alumina — активированный глинозём, активированный оксид алюминияalumina activated — активированная окись алюминияsilicated alumina — оксид алюминия с добавкой кремнияalumina hydrate lake — лак, осаждённый на гидрате алюминияalumina package — керамический корпус на основе оксида алюминияalumina ceramic scribing — скрайбирование керамических плат из оксида алюминияEnglish-Russian big polytechnic dictionary
  • 7 aluminaАнгло-русский строительный словарь
  • 8 aluminaАнгло-русский технический словарь
  • 9 aluminaactivated alumina — активированный глинозём, активированный оксид алюминияalumina hydrate lake — лак, осаждённый на гидрате алюминияsilicated alumina — оксид алюминия с добавкой кремнияEnglish-Russian base dictionary
  • 10 aluminaalumina activated — активированная окись алюминияsilicated alumina — оксид алюминия с добавкой кремнияalumina hydrate lake — лак, осаждённый на гидрате алюминияEnglish-Russian big medical dictionary
  • 11 alumina alumina n– activated aluminaАнгло-русский строительный словарь. — М.: Русский Язык. С.Н.Корчемкина, С.К.Кашкина, С.В.Курбатова. 1995. Англо-русский словарь строительных терминов
  • 12 aluminaАнгло-русский словарь по кондиционированию и вентиляции
  • 13 aluminaEnglish-Russian dictionary of terms for heating, ventilation, air conditioning and cooling air
  • 14 aluminaглиноземимя существительное:глинозем (alumina, clay, alum earth)окись алюминия (alumina, alum Earth) Англо-русский синонимический словарь
  • 15 alumina[lang name=”English”]alumina activated — активированная окись алюминия[lang name=”English”]alumina hydrate lake — лак, осаждённый на гидрате алюминияEnglish-Russian dictionary on nuclear energy
  • 16 aluminaalumina hydrate lake — лак, осаждённый на гидрате алюминияsilicated alumina — оксид алюминия с добавкой кремнияThe English-Russian dictionary general scientific
  • 17 aluminalevigated alumina тонкоизмельченный оксид алюминия English-Russian dictionary of biology and biotechnology
  • 18 alumina
    1. глинозем (металлургия)
    2. глинозем

    глинозем Оксид алюминия, являющийся основной частью большинства горных пород.Примечание Оксид алюминия существует в различных модификациях.[ГОСТ Р 52918-2008] 

EN

глинозем
Белый кристаллич. порошок, состоящий до 98 % из а- и у-модификаций Аl2О3 и являющийся исходным сырьем для получения металлич. Аl, специальных видов керамики, белого электрокорунда, огнеупоров, электроизоляторных изделий и катализаторов при произ-ве каучука. По физич. свой-вам технич.

глинозем обычно разделяют на три группы: «мучнистый», «песчаный» и промежуточный или недообоженный. «Мучнистый» глинозем представляет плохо текучий порошок с удельной поверхностью < 5 м2/г и углом естеств. откоса > 45°.

«Песчаный» глинозем – сравнительно крупный, свободно текучий порошок с удельной поверхностью > 35 м2/г и углом естественного откоса 30-35°, лучше растворяющийся в криолите, чем «мучнистый» глинозем. «Недообожженный» глинозем по своим физич. св-вам приближается к песчаному. Г. из алюминиевых руд (бокситов, нефелинов, алунитов и др.

) извлекают в промышл. щелочными, кислотными и электротермич. способами. Наиболее распространены щелочные способы, которые подразделяют на гидрохим., термич. и комбинир.

[http://metaltrade.ru/abc/a.htm]

What are natural occurring aluminum oxides?

The most common ore is bauxite, which is aluminum oxide, Al2O3, mixed with oxides of silicon, iron, and other elements and varying small percentages of clay and other silicates.

Physically, bauxite can be as hard as rock or as soft as mud, and its color may be red, white, buff, pink, yellow or any combination of these. The picture shows the mining of bauxite at Gove in Australia Bauxite is the product of extreme chemical weathering of aluminum-rich rocks.

Australia produces the largest amount of alumina because she has a large body of bauxite. Jamica, South Africa and some other countries also have a good reserve.

Alcan is an international company in Canada, that produces aluminum products, including aluminum foils. You might have used it to wrap your burgers. Alcan is associated with industries in Australia, Jamica, Brazil, UK, etc. Canada and the United States produces the most amount of aluminum from alumina imported from Austria, but North America does not have a lot of viable alumina mines.

Aluminum oxides often coexist with silicates. Natural aluminum oxide minerals include Corundum, Al2O3

Spinel, MgAl2O4
Hercynite, FeAl2O4
Galaxite, MnAl2O4

Gibbsite, Al(OH)3 Diaspore, AlO(OH) Boehmite, AlO(OH)

Bauxites are mainly used for producing pure alumina, which is the feed stock for aluminum metal production, raw material for ceramics, and other applications.

Corundum

There are a few forms of aluminum oxide, and corundum being the most common.

The structure of corundum can be viewed as a hexagonal close packed array of oxygen atoms with 2/3 of the octahedral sites occupied by Al3+ ions.

Thus, the Al3+ ions are bonded to 6 oxygen in a distorted octahedron. Each such octahedron share a face with one on the upper and one on the lower layers.

The distortion is caused by repulsion between Al3+ ions in octahedra sharing the faces.

Corundum is a dense (specific gravity of 3.97), hard (9 on the Mohs' scale, next only to diamond), high melting (melting point 2288 K), and insoluble in water. Crystals of corundum are usually prismatic or barrel-shaped bounded by steep pyramids. A massive grey granular corundum powder is called emery.

Colored corundum are called ruby (deep red due to presence of Cr3+ ions) and sapphire (blue, pink, yellow or green due to various degrees of Fe2+ or 3+, and Ti4+). The color may be modified by heating or irradiation. Some ruby crystals are shown here exposed in a piece of bauxite ore.

Grey corundum or emery are used as abrasive, for example, emery paper (sand paper) and ruby and sapphire are for gemstones. They do have technical applications. For example, the first LASER was produced using a ruby crystal.

The picture shown here are ruby balls of various size ranging from 0.5 to 6 mm. The picture is from High Precision Components for industrial applications in Ceramics, Ruby, Sapphire, and Tungstencarbide, and they are commercial products. This link shows some interesting applications of alumina related materials.

How is bauxite mined and processed?

Pure aluminas are used for pottery, ceramics, refratories, catalyst supports, and for the production of aluminum by the Hall process. Thus, bauxite and other aluminum containing minerals such as kaolinite (Al4Si4O10(OH)8) must be mined and processed to produce pure alumina.

Australia produces about $3 billion worth of alumina a year from six Australian refineries. These refineries use the Bayer Process to extract aluminum hydroxide from the bauxite using hot caustic liquor. Aluminum oxide, Al2O3, is a typical amphoteric oxide, which dissolves in a strong acid and a strong base.

Al2O3 + 6H+ = 2 Al3+ + 3 H2O
Al2O3 + 6 OH- + 3 H2O = 2 Al(OH)63-
After separation of the solids residue, the clear liquor is cooled.

Depending on the pH of the solution, the aluminate ion Al(OH)63- bears various amounts of charge due to these reactions: Al(OH)63- + H+ = Al(OH)52-(H2O)
Al(OH)52-(H2O) + H+ = Al(OH)4-(H2O)2
Al(OH)4-(H2O)2 + H+ = Al(OH)3(H2O)3 (a precipitate)
In a neutral solution, the compound, Al(OH)3(H2O)3 or Al(OH)3 if water is ignored, forms a gelatinous precipitate. Under controlled manner, the liquor crystallizes to give particles of gibbsite of the desired chemical purity and physical characteristics. A lot of research and development has gone into this crystallization process alone.

The hydroxide ions of gibbsite form two layrs similar to layers of closest packed spheres with Al3+ ions filling in some of the octahedral sites. The crystal structure of gibbsite consists of stacked double layers. It is expected that the hydroxide ions form extensive intra- and inter-layer hydrogen bonds.

Further dehydration converts Al(OH)3 into diaspore and boehmite, both of which have the stoichiometry AlO(OH). Gibbsite is is converted to alumina, Al2O3 by calcination. Alumina is marketed as the feed stock to smelters for the production of aluminium metal, ceramics, catalyst supports and other applications.

Jamica also produces alumina by the Bayer process. This Jamica link describes this process very well, including flow chart of operation. For those who are interested in the mining, chemistry, and economics of alumina production, the Australia companies also have nice web sites to describe their operations.

What are some of the applications of aluminum oxides?

Mineralogists consider a mineral a homogeneous solid body, formed by natural process that has a regular crystal structure with a limit range of atomic compositions. Engineers are mainly interested in properties and their applications.

Scientists are interested in correlate the relationship of structures and properties. Engineers deal with natural and synthetic materials a. Aluminum oxide is a basic material for the ceramic industry.

For more details regarding the properties of alumina, consult the data sheet for alumina ceramics.

Aluminas are basic materials for ceramics, and they are useful for lining containers and mass transferring pipes, especially if heat resistance is required.

Intricate tools such as the 95 % alumina ceramic rotor for 20 cm rotary valve have been made of these materials.

Ceramics are related to many technologies. A list of resources related to ceramics gives many companies, whose main products are made of ceramic materials. For example, aluminas are used for paint, ink, coating and filling paper, adhesives, rubber, pharmaceuticals, tiles, bricks, cooking utilities, table wares, electronic components, porcelain, pottery, dental restoration, and plastics.

Technological changes demand materials with new specific properties. Since changes take place all the time, new materials are also developed all the time.

Additions of specific amounts of other oxides to aluminas produce composite materials whose properties differ from both parent materials. This type of blending is a new frontier of material engineering.

This type of research is carried out in companies such as Precision Engineered Ceramics, The KEIR Manufacturing, Inc., and Intertec Southwest LLC.

How does aluminum oxide protect aluminum from corrosion?

Aluminum is a very reactive metal if it is not protected by its aluminum oxide film. It is much more reactive than zinc and iron, but far less reactive than magnesium. Their oxidation reduction potentials are given below for you to compare.

Fe3+ + 3 e- = Fe(s),       Eo = -0.037 V.
Fe2+ + 2 e- = Fe(s),       Eo = -0.447 V.
Zn2+ + 2 e- = Zn(s),       Eo = -0.76 V.
Al3+ + 3 e- = Al(s),       Eo = -1.67 V.
Mg2+ + 2 e- = Mg(s),       Eo = -2.70 V.

If the oxide film is cracked under aerated water, Al3+ is formed instantly along with OH- ions. Thus, an oxide film is formed immediately, sealing it from further corrosion at the anodic site.

Another important fact is that Al2+ ions will not form, and the aluminum oxide is an inert substance.

Example 1 Calculate the molar volume of aluminum and aluminum oxide.

Solution


The question requires the densities of aluminum and aluminum oxides. The CRC Handbook give their densities as 2.702 and 3.97 g/cc respectively. Thus, molar volumes of Al and aluminum oxides are Vo of Al = 26.98 / 2.702 = 9.96 cc per mol of Al
Vo of Al2O3 = (26.98 + 24.0) / 3.97 = 12.84 cc

Discussion
By applying the Pilling and Bedworth model, aluminum oxide formed has a larger molar volume per Al than the metal itself. Thus, the Pilling and Bedworth model also apply to aluminum and its oxide.

Furthermore, aluminum oxide and some hydrates have different densities, Al2O3.H2O, 3.014 g/cc.
Al2O3.3 H2O, 2.42 g/cc.
Inorganic Chemistry by Swaddle suggested that the formation of Al(OH)3 forms a protective layer. This formula suggest the formation of gibbsite, density 2.44 g/cc leading to a molar volume of 32.0 cc.

Confidence Building Questions

  • What is bauxite?
  • Hint . . . Bauxite is an ore of aluminum oxide and other metal oxide. Skill – To be able to identify the ore bauxite from the description given in this page.

  • What are the two colored forms of corundum?
  • Hint . . . Red corundum is ruby and blue corundum is sapphire.Skill – Explain the relationship of various materials, even if they appear very different.

  • What is the hardness of corundum?
  • Hint . . . 9 on the Mohs' scale, next to diamond.Skill – Explain the properties of corundum and relate them to its applications.

  • What is the arrangement of the oxygen atoms in corundum?
  • Hint . . . The oxygen atoms pack as a hexagonal array.Skill – Describe the structure of corundum, an important mineral related to ruby and sapphire.

  • What is an amphoteric oxide?
  • Hint . . . An oxide that dissolves in strong acid and strong base.Skill – Explain why a concentrated basic solution is used in the Bayer process.

  • What solution is used to extract aluminium from bauxite in the Bayer process?
  • Hint . . . A strong base is used to dissolve aluminum oxide.Skill – Describe the chemistry of the Bayer process for the extraction of alumina.

  • Is aluminum a more reactive metal than zinc towards oxygen?
  • Hint . . . Yes, it is.Skill – Explain the chemical property base on electromotive potentials.

  • Why does aluminum not rust?
  • Hint . . . A thin layer of aluminum oxide protects it from oxidation.Discussion – The thin layer does not cover the luster of aluminum metal.

How is aluminum refined from alumina?

The method to refine aluminum by electrolysis was invented by Charles M. Hall

How is cement related to alumina?

Example 2 A problem related to electrolysis of aluminum

Solution


Al3+ + 3 e- = Al(s),       Eo = -1.67 V.

Discussion

© cchieh@uwaterloo.ca

Источник: http://www.science.uwaterloo.ca/~cchieh/cact/applychem/alumina.html

Alumina | Ceramic | Al2O3 | Aluminon

Alumina

Alumina (or aluminium oxide, Al2O3) is the most widely used advanced ceramic in the world. It combines good hardness and corrosion resistance with reasonable strength and can be used in applications up to 1700°C.

Alumina is available in a range of purities. The high purity ceramics offered by International Syalons are especially suitable for wear and corrosion resistant applications. In addition they offer excellent electrical properties and possess good thermal stability.

ISN offer three fully dense grades of alumina, Aluminon 96, Aluminon 995 and Aluminon 999. The properties of these materials are outlined below.

Aluminon 96

Aluminon 96 is fully dense and suitable for wear and corrosion resistant applications. The table below lists typical mechanical, thermal and electrical property data for Aluminon 96.

Physical property data for Aluminon 96

PropertyValueUnits
Composition96% Al2O3
Density3.75g/cc
Porosity0%
3 point Modulus of Rupture 20°C
(Specimen 3 × 3 × 50mm, span 19.

05mm)

300MPa
3 point Modulus of Rupture 1000°C200MPa
Weibull Modulus10
Compressive Strength>2000MPa
Young's Modulus of Elasticity330GPa
Poisson's Ratio0.

22

Hardness (HR45N)83
Hardness (Vickers Hv50)15.71 (1600)GPa (Kg/mm2)
Fracture Toughness K1C3.5MPa m½
Thermal Expansion Coefficient (0-1200°C)7.0X10-6K-1
Thermal Conductivity20.

0

W/(mK)
Thermal Shock Resistance200ΔT°C quenched in cold water
Maximum Use Temperature1600°C
Electrical Resistivity1015ohm cm

Typical physical property data obtained under test conditions.

All properties have been measured by independent testing authorities. The values given only apply to the test bodies on which they were determined, and therefore can only be recommended values. See our disclaimer.

Download the Aluminon 96 Property Data Sheet PDF (0.17 Mb).

Aluminon 995

Aluminon 995 is fully dense and has excellent corrosion resistance. In addition, it has excellent thermal stability up to 1700°C and can be used as noble metal thermocouple protection tubes. The table below lists typical mechanical, thermal and electrical property data for Aluminon 995.

Physical property data for Aluminon 995

PropertyValueUnits
Composition99.5% Al2O3
Density3.89g/cc
Porosity0%
3 point Modulus of Rupture 20°C
(Specimen 3 × 3 × 50mm, span 19.

05mm)

330MPa
3 point Modulus of Rupture 1000°C250MPa
Weibull Modulus15
Compressive Strength>2000MPa
Young's Modulus of Elasticity370GPa
Poisson's Ratio0.

22

Hardness (HR45N)82
Hardness (Vickers Hv50)15.71 (1600)GPa (Kg/mm2)
Fracture Toughness K1C4.0MPa m½
Thermal Expansion Coefficient (0-1200°C)7.8X10-6K-1
Thermal Conductivity30.

0

W/m/K
Thermal Shock Resistance200ΔT°C quenched in cold water
Maximum Use Temperature1700°C
Electrical Resistivity1015ohm cm

Typical physical property data obtained under test conditions.

All properties have been measured by independent testing authorities. The values given only apply to the test bodies on which they were determined, and therefore can only be recommended values. See our disclaimer.

Download the Aluminon 995 Property Data Sheet PDF (0.13 Mb).

Aluminon 999

Aluminon 999 is a very high purity material with excellent mechanical, thermal and corrosion resistant properties. It is the most stable of our aluminas and is suitable for severe wear and corrosion applications. The table below lists typical mechanical, thermal and electrical property data for Aluminon 999.

Physical property data for Aluminon 999

PropertyValueUnits
Composition99.9% Al2O3
Density3.95g/cc
Porosity0%
3 point Modulus of Rupture 20°C
(Specimen 3 × 3 × 50mm, span 19.

05mm)

500MPa
3 point Modulus of Rupture 1000°C300MPa
Weibull Modulus15
Compressive Strength>2500MPa
Young's Modulus of Elasticity400GPa
Poisson's Ratio0.

22

Hardness (HRA)92
Hardness (Vickers Hv50)17.65 (1800)GPa (Kg/mm2)
Fracture Toughness K1C4.5MPa m½
Thermal Expansion Coefficient (0-1200°C)8.5X10-6K-1
Thermal Conductivity30.

0

W/m/K
Thermal Shock Resistance220ΔT°C quenched in cold water
Maximum Use Temperature1700°C
Electrical Resistivity1015ohm cm

Typical physical property data obtained under test conditions.

All properties have been measured by independent testing authorities. The values given only apply to the test bodies on which they were determined, and therefore can only be recommended values. See our disclaimer.

Download the Aluminon 999 Property Data Sheet PDF (0.13 Mb).

The successful integration of advanced technical ceramics into engineering systems requires close collaboration between you, the end-user, and ourselves, the material suppliers. Please contact our Technical Department to discuss your requirments in detail and assist in exploiting the significant advantages which our advanced ceramics offer.

In addition, see our resources section for guides on designing with ceramics and more property data comparing Aluminon ceramics with other engineering ceramics. For a comparison of the physical properties of all our materials see our Material Properties Datasheet.

Источник: https://www.syalons.com/materials/alumina

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