Hafnium Bromide is a highly water soluble crystalline Hafnium source for uses ... Ultra high purity and high purity compositions improve both optical quality and usefulness as ... it is found as colorless soluble crystalline mineral halide salts. Bromine was discovered and first isolated by Antoine Jérôme Balard and Leopold Gmelin in 1825 ...Web
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On the basis of their intraperitoneal LD50 values, these elements increase in toxicity in the following order: scandium, samarium, gadolinium, terbium, thulium, ytterbium, hafnium, and niobium. Moreover, acute lethality except for hafnium and niobium appears to be related to atomic number, increasing as this unit is increased.Web
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The toxicology and pharmacology of hafnium salts was investigated. Acute intraperitoneal toxicity of hafnyl chloride is of the delayed type with an LD/sub 50//7 days of 112 (93.3 to 134.4) mg/kg. Chronic feeding for 90 days at levels of 1.0, 0.1, and 0.01% of the diet produced liver changes at the 1.0% level.Web
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Hafnium Sulfate is a moderately water and acid soluble Hafnium source for uses compatible with sulfates. Sulfate compounds are salts or esters of sulfuric acid formed by replacing one or both of the hydrogens with a metal. ... Ultra high purity and high purity compositions improve both optical quality and usefulness as scientific standards.Web
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Download Citation | Direct Ester Condensation from a 1:1 Mixture of Carboxylic Acids and Alcohols Catalyzed by Hafnium(IV) or Zirconium(IV) Salts. | To promote atom efficiency in synthesis and to ...Web
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A series of hafnium salts of heteropoly tungstate (Hf x TPA) catalysts were prepared by exchanging the counter cations (hydrogen) of heteropoly tungstate with hafnium ions. The prepared catalysts were characterized by FT-IR, Laser Raman, temperature programmed desorption of ammonia, scanning electron microscopy, and X …Web
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The toxicology and pharmacology of hafnium salts have been investigated. Acute intraperitoneal toxicity of hafnyl chloride is of the delayed type with an LD 50 per 7 days of 112 (93.3–134.4) mg/kg. Chronic feeding for 90 days at levels of 1.0, 0.1, and 0.01% of the diet produced liver changes at the 1.0% level.Web
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Hafnium (Hf) is a refractory metal with a high melting point. Hf is exploited to produce the elements of reactor control and shielding systems and containers for storing radioactive …Web
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Hafnium is a ductile metal with a brilliant silver luster and is very difficult to separate. Resistant to concentrated alkalis, it reacts at elevated temperatures with oxygen, nitrogen, carbon, boron, sulfur, and silicon, and directly with halogens to form tetrahalides. ... Salts and Inorganics ; Elemental Metals ; Transition Metals ; Hafnium ...Web
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The toxicologic and pharmacologic effects of hafnium salts. The toxicologic and pharmacologic effects of hafnium salts Toxicol Appl Pharmacol. 1962 Mar:4:238-46. doi: …Web
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Hafnium, symbol Hf, atomic number 72, atomic weight 178.49, belongs to group IVB in the periodic table. Hafnium is a shiny silver-gray transition metal with a density of 13.31g/cm³ (20℃), a melting point of 2233 ℃ (2506 K, 4051 °F), and a boiling point of 4603 °C (4876 K, 8317 °F). The dense metal hafnium is inactive and reacts with air ...Web
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Hafnium salts of dodeca-tungstophosphoric acid catalysts for liquid phase benzylation of anisole with dibenzylether Chowdari Ramesh Kumar, N. Rambabu, N. Lingaiah, P.S. Sai Prasad, A.K. Dalai Pages 1-11Web
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Elemental hafnium reacts with hydrogen (>250°C), carbon (>500°C), and nitrogen (>900°C) to form brittle, nonstoichiometric interstitial compounds with metal-like conductivity. In molten salts, hafnium is normally quadrivalent, but in anhydrous molten halide salts, it can be reduced to hafnium(III) and hafnium(II).Web
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Hafnium dioxide, hafnia (HfO 2) is isomorphic with zirconia, and the crystal ionic radius of Hf 4 + (85 pm) is very similar to that of Zr 4 + (86 pm), allowing complete solid solubility, …Web
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A process is disclosed for producing a stabilised hafnium oxide powder or a hafnium oxide-containing powder suitable for compacting molded bodies, then for sintering them into high-density ceramic materials. For that purpose an aqueous solution of hafnium salt containing an additive is transformed into droplets. The thus obtained droplets are consolidated …Web
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Fig. 1 shows the FT-IR spectra of hafnium salts of 12-tungstophosphoric acid along with the parent acid. Pure TPA (Fig. 1 (a)) shows characteristic bands in the fingerprint region, at 1081, 988, 896, and 796 cm −1 that indicate P–O, W=O t (O t —refers to the terminal oxygen), W–O c –W (O c —refers to the corner oxygen), and W–O e –W …Web
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Among Sn(II) heteropoly salts, the Sn1.5PW12O40 was the most active and selective catalyst, achieving high conversions (ca. 90 %) and selectivity (90–97 %) for alkyl esters and angelica lactone ...Web
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Transition Metal Salts Hafnium(IV) chloride, 99.9% (metals basis), Zr0.5%, Thermo ... Hafnium(IV) chloride is used as a precursor for catalyst involved in the Ziegler-Natta polymerization of propylene. ... Quality Management. Thermo Fisher Scientific. Programs & Services. Encompass Procurement Services. eProcurement Integration Solutions.Web
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Electrochemical processing is used extensively in the primary extraction of metals (electrowinning), the purification and recycling of metals (electrorefining), and the formation of metal coatings (electroplating). With respect to the refractory metals, electrochemical processing is conducted almost exclusively in nonaqueous media, predominantly in …Web
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and Q. C. Zhang found that HfO2 film has better interface quality, so it has been actively studied as the gate dielectric of transistors [28]. At the same time, hafnium oxide has a high dielectric constant (~30) and large bandgap (~5.68 eV) [29], which enables the devices to obtain better capacitor performances.Web
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The properties of high-temperature diborides with layered structures comprised of alternating atomic planes of metal and boron (Fig. 2) have been best studied experimentally.The physicomechanical properties of titanium, zirconium and hafnium diborides are presented in Table 2.A detailed analysis of more recent results taking into …Web
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Related Elements. 72 Hf 178.480000000 Hafnium. See more Hafnium products. Hafnium (atomic symbol: Hf, atomic number: 72) is a Block D, Group 4, Period 6 element with an atomic weight of 178.49. The number of electrons in each of Hafnium's shells is 2, 8, 18, 32, 10, 2 and its electron configuration is [Xe] 4f 14 5d 2 6s 2.Web
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Element Hafnium (Hf), Group 4, Atomic Number 72, d-block, Mass 178.486. Sources, facts, uses, scarcity (SRI), podcasts, alchemical symbols, videos and images.Web
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Subsequently, the salt was dehydrated by stepwise heating to 400 °C, 600 °C, and 800 °C [25]. Metalliding of the iridium plates was performed at 950–1200 °C for 5 h in the molten salt, as shown in Fig. 1. The iridium and hafnium plates were immersed in molten salt with stainless steel wire connections outside the metalliding cell.Web
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We show that the direct condensation of equimolar amounts of carboxylic acids and alcohols can be achieved with the use of hafnium(IV) salts, such as commercially available hafnium(IV) chloride and hafnium(IV) tert-butoxide. The present method can be applied to direct polyesteriÞcation and may be suitable for large-scale operations.Web
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Natural hafnium is a mixture of six stable isotopes: hafnium-174 (0.2 percent), hafnium-176 (5.2 percent), hafnium-177 (18.6 percent), hafnium-178 (27.1 percent), hafnium-179 (13.7 percent), and hafnium-180 (35.2 …Web
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The interaction of hafnium(IV) salts (oxide-dichloride, chloride, and bromide) with nitrilotriacetic acid (NTA), diethylenetriamminepentaacetic acid (DTPA), 1,2 …Web
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It was the discovery of one of the only six then remaining gaps in the periodic table. It also turned out to be the one but last discovery of any naturally occurring element, the last one being rhenium a few years later. single highest melting point of any known compound at 4125. Hafnium is not cheap given how difficult it is to extract and ...Web
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The electrolysis of fluoride-containing salts can produce zirconium metal with comparable purity to that from the Kroll process, but the generation of environmental harmful off-gas chloroflourocarbons ... nuclear grade zirconium tetrachloride and commercially pure quality hafnium tetrachloride can be obtained. The fused salt solvent is able to ...Web
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See more Hafnium products. Hafnium (atomic symbol: Hf, atomic number: 72) is a Block D, Group 4, Period 6 element with an atomic weight of 178.49. The number of electrons in each of Hafnium's shells is 2, 8, 18, 32, 10, 2 and its electron configuration is [Xe] 4f 14 5d 2 6s 2. The hafnium atom has a radius of 159 pm and a Van der Waals radius ...Web
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Hafnium salts of dodeca-tungstophosphoric acid catalysts for liquid phase benzylation of anisole with dibenzylether Chowdari Ramesh Kumara,b, N. Rambabua, N. Lingaiahb,∗, P.S. Sai Prasadb, A.K. Dalaia,∗ a Department ofChemical and Biological Engineering, University Saskatchewan, Saskatoon, SK, S7N 5A9, Canada b CatalysisWeb
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It involves the direct electrolysis of the tetra- chloride HfCl4 in a molten bath of purified salts, based on the alkaline chlorides, NaCI and KC1, with a small amount of fluoride, NaF [13-15]. ... It should be noted that nuclear quality hafnium, containing about 300 ppm of oxygen, has mechanical properties similar to those of Zircaloy. The ...Web
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Hafnium Acetate is a moderately water soluble crystalline Hafnium source that decomposes to Hafnium oxide on heating. It is generally immediately available in most volumes. All metallic acetates are inorganic salts containing a metal cation and the acetate anion, a univalent (-1 charge) polyatomic ion composed of two carbon atoms ionically …Web
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We describe highly efficient and di-rect ester condensation with equimolar amounts of carboxylic acids and alcohols -alyzed by hafnium(IV) chloride and alkox …Web
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Hafnium(IV) chloride purified by sublimation, 99.9% trace metals basis; CAS Number: 1; EC Number: 236-826-5; Synonyms: Hafnium tetrachloride,Tetrachlorohafnium; Linear Formula: HfCl4; find Sigma-Aldrich-590592 MSDS, related peer-reviewed papers, technical documents, similar products & more at Sigma-AldrichWeb
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Abstract The toxicology and pharmacology of hafnium salts have been investigated. Acute intraperitoneal toxicity of hafnyl chloride is of the delayed type with an LD 50 per 7 days of 112 (93.3–134.4) mg/kg. Chronic feeding for 90 days at levels of 1.0, 0.1, and 0.01% of …Web
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Hafnium, an important element for oxide scale adherence effects, is occasionally added at low levels (approximately 0.01 wt. %) to superalloy compositions. However, such a level may not be the optimum level for protective coating performance. ... salts and oxides that accelerate the rate of oxidation of structural materials. Protective coatings ...Web
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