12055-23-1 Usage
Physical Properties
White crystalline solid, when heated at 1,500°C, it transforms into a tetragonal modification with shrinkage; tetragonal form converts to a cubic polymorph with fluorite structure when heated at 2,700°C; density 9.68 g/cm3; melts at 2,774°C; insoluble in water; dissolves slowly in hydrofluoric acid at ordinary temperatures.
Uses
Different sources of media describe the Uses of 12055-23-1 differently. You can refer to the following data:
1. Hafnium dioxide is a high temperature refractory material. It is used for control rods in nuclear reactors. It has high stability and high thermal neutron absorption values. It also is used in special optical glasses and glazes.
2. Hafnium(IV) oxide is used as Intermediates, Paint additives and coating additives, metal Products. And it is also used in optical coatings, as a refractory material in the insulation of such devices as thermocouples.
Preparation
Hafnium dioxide may be prepared by heating the metal with air or oxygen at elevated temperatures (above 400°C). Also, the oxide can be obtained by igniting hafnium salts, such as hydroxide, oxalate, sulfate, nitride, carbide, boride or tetrachloride in air. Hafnium carbide converts to dioxide when heated with oxygen at 500°C. The commercial products generally contain about 95-97% hafnium dioxide mixed with small amount of zirconium oxide. The compound can be prepared at 99.9% purity.
Reactions
Hafnium dioxide reacts with chlorine in the presence of carbon at elevated temperatures to yield hafnium tetrachloride, HfCl4. When ammonium hydroxide solution is added to an acid solution of hafnium dioxide, the hydrous oxide, HfO2?xH2O precipitates.
When heated with concentrated sulfuric acid, the product is hafnium sulfate, Hf(SO4)2.
Reaction with carbon at 1,500°C produces hafnium carbide, HfC.
Reaction with sodium fluorosilicate, Na2SiF6 at elevated temperatures yields sodium fluorohafnate, Na2HfF6.
Description
Hafnium is a shiny, silvery, ductile metal and resistant to corrosion. The physical properties
of hafnium metal samples are markedly affected by zirconium impurities, especially
the nuclear properties, as these two elements are among the most difficult to separate
because of their chemical similarity.
Hafnia is used in optical coatings and as a high-k dielectric in dynamic randomaccess
memory (DRAM) capacitors. Hafnium (IV) oxide is a colourless, inert solid and
has been reported as one of the most common and stable compounds of hafnium. It is
an electrical insulator. Hafnium dioxide is an intermediate in some processes that give
hafnium metal. It reacts with strong acids and strong bases. It dissolves slowly in hydrofluoric
acid. At high temperatures, it reacts with chlorine in the presence of graphite or
carbon tetrachloride and forms the hafnium tetrachloride. Hafnium-based oxides are
currently important materials to replace silicon oxide as a gate insulator because of its
high dielectric constant.
Hafnium (Hf) is found in association with zirconium ores, production based on zircon
(ZrSiO4) concentrates which contain 0.5%–2% hafnium. Hafnium has extensive applications
in industries especially because of its resistance to corrosion. Different compounds
of hafnium used in ceramics industry are hafnium boride, hafnium carbide, hafnium
nitride, hafnium oxide, hafnium silicate, and hafnium titanate. Hafnium-based oxides
are currently leading candidates to replace silicon oxide as a gate insulator in fieldeffect
transistors. The compound appears to have been chosen by both IBM and Intel
as a substrate for future integrated circuits, where it may help in the continuing effort
Chemical Properties
Hafnium is a refractory metal which occurs in
nature in zirconium minerals.
Flammability and Explosibility
Nonflammable
Potential Exposure
Hafnium metal has been used as a
control rod material in nuclear reactors. Thus, those
engaged in fabrication and machining of such rods may be
exposed.
Shipping
UN1326 Hafnium powder, wetted with not
<,25% water (a visible excess of water must be present)
(1) mechanically produced, particle size<53 μm; (2)
chemically produced, particle size<840 μm, Hazard Class:
4.1; Labels: 4.1-Flammable solid. UN2545 Hafnium pow der, dry, Hazard Class: 4.1; Labels: 4.1-Flammable solid.
UN1346 Hafnium powder, wetted with not less than 25%
water (a visible excess of water must be present)
(1) mechanically produced, particle size less than 53 μm;
(2) chemically produced, particle size less than 840 μm,
Hazard Class: 4.1; Labels: 4.1-Flammable solid.
Incompatibilities
Fine powder or dust may form explosive
mixture in air. The powder is highly flammable and a strong
reducing agent. The powder or dust reacts with moisture
forming flammable hydrogen gas; may spontaneously ignite
on contact with moist air; and at higher temperatures, with
nitrogen, phosphorous, oxygen, halogens, and sulfur; contact
with hot nitric acid; heat, shock, friction, strong oxidizers;
or ignition sources may cause explosions.
Waste Disposal
Recovery. Consider recycling,
otherwise, this chemical must be disposed of in compliance
with existing federal and local regulations.
Check Digit Verification of cas no
The CAS Registry Mumber 12055-23-1 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,2,0,5 and 5 respectively; the second part has 2 digits, 2 and 3 respectively.
Calculate Digit Verification of CAS Registry Number 12055-23:
(7*1)+(6*2)+(5*0)+(4*5)+(3*5)+(2*2)+(1*3)=61
61 % 10 = 1
So 12055-23-1 is a valid CAS Registry Number.
InChI:InChI=1/Hf.2O/rHfO2/c2-1-3
12055-23-1Relevant articles and documents
Infrared spectrum and structure of the Hf(OH)4 molecule
Wang, Xuefeng,Andrews, Lester
, p. 7189 - 7193 (2008/10/09)
Laser-ablated Hf atoms react with H2O2 and with H2 + O2 mixtures in solid argon to form the Hf(OH) 2 and Hf(OH)4 molecules, which are identified from the effect of isotopic substitution on the matrix infrared spectra. Electronic structure calculations at the MP2 level varying all bond lengths and angles converge to nearly linear and tetrahedral molecules, respectively, and predict frequencies for these new product molecules and mixed isotopic substituted molecules of lower symmetry that are in excellent agreement with observed values, which confirms the identification of these hafnium hydroxide molecules. This work provides the first evidence for a metal tetrahydroxide molecule and shows that the metal atom reaction with H2O2 in excess argon can be used to form pure metal tetrahydroxide molecules, which are not stable in the solid state.
