hafnium
Hafnium atomic absorption standard solution
CAS: 7440-58-6
Molecular Formula: Hf
hafnium - Names and Identifiers
| Name | Hafnium atomic absorption standard solution |
| Synonyms | celtium Hafnium hafniumpowder HafniumZrwire HafniumpowderZr HafniumpowderNZrmesh hafniummetal,wet(dot) hafniummetal,dry(dot) HafniumwireNZrmmdiagcm HafniumfoilNZrmmthickxmmwidegx Hafnium atomic absorption standard solution |
| CAS | 7440-58-6 |
| EINECS | 231-166-4 |
| InChI | InChI=1/Hf |
| InChIKey | VBJZVLUMGGDVMO-UHFFFAOYSA-N |
hafnium - Physico-chemical Properties
| Molecular Formula | Hf |
| Molar Mass | 178.49 |
| Density | 13.3 g/cm3 (lit.) |
| Melting Point | 2227 °C (lit.) |
| Boling Point | 4602 °C (lit.) |
| Water Solubility | soluble HF; slowly reacts with conc H2SO4, aqua regia [KIR80] |
| Appearance | wire |
| Specific Gravity | 13.31 |
| Color | Silver-gray |
| Exposure Limit | ACGIH: Ceiling 2 ppmOSHA: Ceiling 5 ppm(7 mg/m3)NIOSH: IDLH 50 ppm; Ceiling 5 ppm(7 mg/m3) |
| Merck | 13,4603 |
| Storage Condition | Store at +15°C to +25°C. |
| Stability | Stable. Incompatible with oxygen, sulfur, strong oxidizing agents, halogens, phosphorus, strong acids. Highly flammable. |
| Physical and Chemical Properties | The chemical properties of hafnium and zirconium are very similar, with good corrosion resistance, not easily attacked by the general acid and alkali aqueous solution; Soluble in hydrofluoric acid and the formation of fluoride complexes. At high temperatures, hafnium can also be directly combined with gases such as oxygen and nitrogen to form oxides and nitrides. Hafnium is often 4 in the compound. The major compound is hafnium oxide hfo2. There are three different variants of hafnium oxide: The hafnium oxide obtained by continuously calcining the sulfate and oxychloride of hafnium is a monoclinic variant; The hafnium oxide obtained by heating the hydroxide of hafnium at about 400 ° C. Is a tetragonal variant; cubic variants are available if calcined above 1000 °c. Another compound is hafnium tetrachloride, which is a raw material for the preparation of metallic hafnium and can be prepared by the action of chlorine on a mixture of hafnium oxide and carbon. Upon contact with water, hafnium tetrachloride is immediately hydrolyzed to a very stable HfO(4H2O)2 ion. The HfO2 ion is present in many compounds of hafnium, and crystals of hafnium oxychloride hydrate HfOCl2 · 8H2O are crystallized in a solution of hafnium tetrachloride acidified with hydrochloric acid. |
hafnium - Risk and Safety
| Risk Codes | R11 - Highly Flammable R20/21/22 - Harmful by inhalation, in contact with skin and if swallowed. R34 - Causes burns R23/24/25 - Toxic by inhalation, in contact with skin and if swallowed. |
| Safety Description | S9 - Keep container in a well-ventilated place. S16 - Keep away from sources of ignition. S26 - In case of contact with eyes, rinse immediately with plenty of water and seek medical advice. S27 - Take off immediately all contaminated clothing. S33 - Take precautionary measures against static discharges. S36 - Wear suitable protective clothing. S36/37/39 - Wear suitable protective clothing, gloves and eye/face protection. S45 - In case of accident or if you feel unwell, seek medical advice immediately (show the label whenever possible.) S28 - After contact with skin, wash immediately with plenty of soap-suds. |
| UN IDs | UN 3178 4.1/PG 3 |
| WGK Germany | - |
| RTECS | MG4600000 |
| TSCA | Yes |
| HS Code | 3822 00 00 |
| Hazard Class | 8 |
| Packing Group | III |
hafnium - Reference Information
| resistivity (resistivity) | 29.6 μΩ-cm, 0°C |
| EPA chemical information | Information provided by: ofmpub.epa.gov (external link) |
| Introduction | Hafnium, metal Hf, atomic number 72, atomic weight 178.49, is a shiny silver-gray transition metal. Hafnium has 6 natural stable isotopes: hafnium 174, 176, 177, 178, 179, and 180. Hafnium does not interact with dilute hydrochloric acid, dilute sulfuric acid and strong alkali solutions, but is soluble in hydrofluoric acid and aqua regia. The element name comes from the Latin name of Copenhagen City. In 1925, the Swedish chemist Hevesi and the Dutch physicist Koster used the method of fractional crystallization of fluorine-containing complex salts to obtain pure hafnium salt, and reduced it with metal sodium to obtain pure hafnium metal. The content of hafnium in the earth's crust is 0.00045%, and it is often associated with zirconium in nature. |
| Physical properties | Hafnium is a silver-gray metal with a metallic luster; there are two variants of hafnium: α hafnium is a hexagonal close-packed variant (1750 ℃), Its transition temperature is higher than zirconium. Hafnium metal has allotomorphic variants at high temperatures. Hafnium metal has a high neutron absorption cross section and can be used as a control material for reactors. there are two kinds of crystal structures: hexagonal close packing (α-formula) below 1300 ℃; When above 1300 ℃, it is body centered cubic (β-formula). A metal with plasticity that becomes hard and brittle when impurities are present. It is stable in the air and only darkens on the surface when burning. The filaments can be ignited by the flame of a match. Properties like zirconium. It does not interact with water, dilute acid or strong alkali, but is easily dissolved in aqua regia and hydrofluoric acid. It is mainly 4-valent in the compound. Hafnium alloy (Ta4HfC5) is the substance with the highest known melting point (about 4215 ℃). |
| Discovery history | Hafnium was believed to exist in a variety of minerals many years before it was discovered, until D. Coster and G. von Hevesey discovered hafnium in 1923. According to Bohr's theory, it is expected that the new element is related to zirconium. It was finally identified by X-ray spectroscopy in Norway's zircon. Named hafnium to commemorate the city where it was discovered. Most zirconium minerals contain 1 to 5% hafnium. The Von Hevesey and Jantzen repeatedly recrystallized either ammonium difluoride or potassium fluoride, separating them from zirconium. Hafnium metal was first prepared by Van Arkel and deBoer by passing the vapor of tetraiodide through a heated tungsten wire. Almost all hafnium metals produced now are made by reducing tetrachloride with magnesium or sodium (Kroll process). Hafnium is a tough metal with a bright silver luster, and its performance is greatly affected by zirconium impurities. Of all the elements, zirconium and hafnium are the two most difficult to separate. Their chemical properties are almost the same. However, the density of zirconium is about half that of hafnium, and very pure hafnium has been produced, of which zirconium is the main impurity. |
| Source | Hafnium has more crustal abundance than commonly used metals bismuth, cadmium, and mercury, which is equivalent to beryllium, germanium, and uranium. All zirconium-containing minerals contain hafnium. The hafnium content in industrial zircon is 0.5 ~ 2%. Beryllium zircon (alvite) in secondary zirconium ore can contain hafnium as high as 15%. There is also a metamorphic zircon curved spar (cyrtolite), containing HfO of more than 5%. The latter two minerals have small reserves and have not been adopted in industry. Hafnium is mainly recovered from the process of producing zirconium. Zirconium exists in most zirconium ores. Because there is very little content in the earth's crust. It often coexists with zirconium and has no separate ore. |
| application | is very useful because hafnium is easy to emit electrons (such as used as a filament for incandescent lamps). Used as the cathode of an X-ray tube, an alloy of hafnium and tungsten or molybdenum is used as the electrode of a high-voltage discharge tube. Commonly used as X-ray cathode and tungsten wire manufacturing industry. Pure hafnium has plasticity, easy processing, high temperature and corrosion resistance, and is an important material for the atomic energy industry. Hafnium has a large thermal neutron capture cross section and is an ideal neutron absorber, which can be used as a control rod and protection device for atomic reactors. Hafnium powder can be used as a rocket thruster. The cathode of X-ray tube can be manufactured in the electrical industry. Hafnium alloy can be used as the front protective layer for rocket nozzles and gliding re-entry aircraft. Hafnium-tantalum alloy can be used to make tool steel and resistance materials. Hafnium is used as an additive element in heat-resistant alloys, such as tungsten, molybdenum, and tantalum alloys. Hafnium carbide can be used as a cemented carbide additive due to its high hardness and melting point. The melting point of 4TaCHfC is about 4215 ℃, which is the compound with the highest melting point known. Hafnium can be used as a getter for many inflation systems. Hafnium getter can remove oxygen, nitrogen and other unnecessary gases in the system. Hafnium is often used as an additive of hydraulic oil to prevent the volatilization of hydraulic oil during high-risk operations. It has strong anti-volatility. If this characteristic is used, it is generally used in industrial hydraulic oil. Medical hydraulic fluid. |
| Preparation | 1. It can be prepared by reducing hafnium tetrachloride by magnesium or thermally decomposing hafnium tetraiodide. HfCl4 and K2HfF6 can also be used as raw materials. Electrolytic production in NaCl-KCl-HfCl4 or K2HfF6 melt is similar to that of zirconium. 2. Hafnium mostly coexists with zirconium, and there is no hafnium raw material that exists alone. The raw material for manufacturing hafnium is crude hafnium oxide separated in the process of manufacturing zirconium. Hafnium oxide is extracted by ion exchange resin, and then the metal hafnium is prepared from this hafnium oxide by the same method as zirconium. 3. It can be prepared by reducing hafnium tetrachloride (HfCl4) and sodium by co-heating. 4. The earliest method to separate zirconium and hafnium is the graded crystallization of fluorine-containing complex salt and the graded precipitation of phosphate. These methods are troublesome to operate and are limited to laboratory use. New technologies for separating zirconium and hafnium, such as fractional distillation, solvent extraction, ion exchange and fractional adsorption, have emerged one after another. Among them, solvent extraction has more practical value. The two commonly used separation systems are thiocyanate-isohexone system and tributyl phosphate-nitric acid system. The products obtained by the above method are all hafnium hydroxide, and pure hafnium oxide can be obtained by calcination. High-purity hafnium can be obtained by ion exchange. |
| Production method | 1. It can be produced by reducing hafnium tetrachloride by magnesium or thermally decomposing hafnium tetraiodide. HfCl 4 and K 2 HfF 6 can also be used as raw materials. Electrolytic production in NaCl-KCl-HfCl 4 (or K 2 HfF 6) melt is similar to that of zirconium. 2. Hafnium mostly coexists with zirconium, and there is no single hafnium raw material. At present, the raw material for manufacturing hafnium is crude hafnium oxide separated in the process of manufacturing zirconium. Hafnium oxide is extracted by ion exchange resin, and then the metal hafnium is prepared from this hafnium oxide by the same method as zirconium. |
| category | flammable solids |
| toxicity classification | highly toxic |
| acute toxicity | (reference) mice-injection LD50: 76 mg/kg |
| explosive hazard characteristics | blastable when mixed with oxidant |
| flammability hazard characteristics | flammability in case of open flame, high temperature and oxidant |
| storage and transportation characteristics | warehouse ventilation and low temperature drying; Store separately from oxidants and acids |
| fire extinguishing agent | water, dry powder |
| occupational standard | TWA 0.5 mg/m3; STEL 1.5 mg/m3 |
| toxic substance data | information provided by: pubchem.ncbi.nlm.nih.gov (external link) |
| immediate life-threatening and health concentration | 50 mg Hf/m3 |
Last Update：2024-04-09 02:00:04
