Showing papers on "Hydrofluoric acid published in 1987"

Diode laser spectroscopy of the ν3 and ν2 bands of FHF− in 1300 cm−1 region

Abstract: The ν3, ν2, and ν1+ν3−ν1 bands of a linear molecular anion FHF− have been detected by diode laser spectroscopy in 1300 cm−1 region. The previously reported 1848 cm−1 band [K. Kawaguchi and E. Hirota, J. Chem. Phys. 84, 2953 (1986)] was reassigned to the ν1+ν3 combination band. Analysis of the observed spectra gave the fundamental frequencies ν1=583.0539(13), ν2=1286.0284(22), and ν3=1331.1502(7) cm−1 with three standard deviations in parentheses. From the rotational constants obtained, the equilibrium F–F internuclear distance was calculated to be 2.277 71(7) A.

Surface treating composition for micro processing

Abstract: A surface treating composition for micro processing which comprises a mixture of hydrofluoric acid, ammonium fluoride solution and water, and at least one compound selected from the group of surfactants consisting of aliphatic carboxylic acids, salts of aliphatic carboxylic acids, aliphatic amines and aliphatic alcohols.

The Effect of Phosphoric Acid Treatment on the Catalytic Property of Niobic Acid

Abstract: The effects of the treatment of niobic acid with phosphoric acid, sulfuric acid, and hydrofluoric acid on its surface area, structure, acidic property, and catalytic activity have been studied. The treatment with phosphoric acid was found to be most effective for maintaining a large surface area and a large amount of strong acid sites and for preventing niobic acid from crystallizing even after the heat treatment at higher temperatures above 600 °C. The XPS study revealed that a large amount of phosphorous exists on niobic acid after high temperature heat treatment. In accordance with these results, niobic acid treated with phosphoric acid and heat-treated at higher temperatures exhibited high catalytic activities for methanol conversion and ethylene hydration, whereas the activities of niobic acid containing no phophoric acid were very low when heat-treated at high temperatures.

VG-13: A nuclear-track-recording glass detector with uniquely high resolution

Abstract: We find that tracks of relativistic heavy nuclei as light as lanthanum (Z = 57) can be revealed in VG-13, a commercially available phosphate glass, by etching it in fluoboric, nitric or hydrofluoric acid. A study of its response to relativistic U, Au and La ions at temperatures from −77°C to +20°C shows that the temperature-dependence of the response is one or two orders of magnitude smaller than for track-recording plastic detectors. Ionic charge states corresponding to fully stripped ions, ions with one electron, and ions with two electrons are resolved with standard deviations ranging from −0.1 to 0.25 charge unit. This charge resolution for heavy nuclei exceeds that of any other detector, making possible searches for fractionally charged heavy nuclei in high-energy nucleus-nucleus collisions. It may also be possible, by range and etch rate measurements, to determine the isotopic abundances of iron and heavier elements in cosmic rays.

Radiotracer investigation of the interference of hydrofluoric acid in the determination of arsenic and antimony by hydride generation atomic absorption spectrometry

Abstract: The influence of hydrofluorica acid on the behavior of arsenic and antimony in hydride generation with NaBH/sub 4/ was investigated by means of the radiotracers /sup 76/As and /sup 124/Sb. Simultaneously, the corresponding extinctions were measured. Up to a concentration of 1% hydrofluoric acid present in hydrochloric acid sample solutions does not affect the hydrogenation of As(III) and Sb(III). In solutions with higher HF concentration, As(V) forms (AsF/sub 5/OH)/sup -/ ions which do not react with NaBH/sub 4/. After the (AsF/sub 4/OH)/sup -/ ions are hydrolyzed, the interference of hydrofluoric acid can be sufficiently reduced by complex formation with boric acid. Antimony(V) is not hydrogenated in the presence of hydrofluoric acid, which, in addition, seriously hinders the reduction of Sb(V) to Sb(III). Improved procedures are proposed which allow the elimination of the interference of hydrofluoric acid in both the hydrogenation and the absorption measurement stages and also in the reduction of Sb(V) to Sb(III) in this medium.

Inhibitors for Armco iron and ASTM A106 plain steel in hydrofluoric acid

Abstract: Different classes of organic substance (acetylenic derivatives, nitrogen containing additives, and/or sulphur containing additives) were tested as inhibitors for corrosion of ASTM A 106 plain steel and Armco iron in hot diluted hydrofluoric acid solutions. Those additives interacting with the metal surface by chemisorption through available electron lone pairs were the most efficient substances. The best results were obtained with sulphur containing additives; these markedly inhibit the acid attack on both Armco iron and plain steel. Though very efficient, some sulphur containing additives (e.g. phenylthiourea) act as promoters of hydrogen entry into the metal lattice in hydrofluoric acid corrosion: however, others (e.g. dibenzylsulphoxide) can be safely used as inhibitors in this acid solution.

Semiconductor wafer washing equipment

Abstract: PURPOSE:To enable removing minute particles in a liquid and perfectly replacing a washing liquid between treatment processes by synthesizing the washing liquid using a gas and very pure water in a treatment tank. CONSTITUTION:A retainer 3 which holds and rotates a semiconductor wafer 2, a water supply nozzle 9 which spouts very pure water in a foggy state, gas cylinders 6, 10, 11 which contain various reactive gases for the raw materials of a washing liquid, a vaporizer 12 which evaporates anhydrous hydrofluoric acid and a gas filter 5 which removes minute particles during evaporation are provided. The washing liquid is synthesized by mixing the reactive gases and the evaporated anhydrous hydrofluoric acid spouted in a treatment tank 1 and the vary pure water spouted from the water supply nozzle 9. This can reduce the number of the minute particles and can more perfectly replace a washing agent between treatment processes since evaporation is used.

Catalyzed gaseous etching of silicon

Abstract: Traces of copper and silver are shown to accelerate the etching of silicon by molecular fluorine. Copper residue formed by aqueous HF etching of sputter‐deposited aluminum (0.5% Cu) produces a 100‐fold increase in the etching rate of an underlying (100) silicon, compared to unmetallized samples, at temperatures above 80 °C. Above 180 °C, F2 exhibits a higher absolute etch rate than equivalent concentrations of fluorine atoms. The temperature dependence of the reaction is interpreted in terms of a Cu‐CuF(x=1,2) catalytic cycle in which CuF(x=1,2) is the active intermediate. Preliminary results for other gases and metals are presented, and the origin of discrepancies in published rate data for the F2/Si reaction are discussed.

Production of lithium fluoride complex salt

Abstract: PURPOSE:To efficiently produce a high purity LiF complex salt useful as the electrolyte of a cell, a catalyst, etc., by releasing hydrofluoric acid from acidic LiF and allowing the resulting porous LiF to react with the fluoride of a group III, IV or V element of the periodic table. CONSTITUTION:Acidic LiF obtd. by the reaction of LiF with hydrofluoric acid is heated to 60-700 deg.C to release hydrofluoric acid from the acidic LiF. The resulting porous LiF is allowed to react with the fluoride of a group III, IV or V element of the periodic table, e.g., BF at 50-200 deg.C to obtain an LiF complex salt contg. 0.1-10wt.% unreacted LiF. This unreacted LiF is removed by washing the complex salt with an org. solvent such as 1,2-dimethoxyethane. The amt. of the org. solvent used is twice-ten-odd times the amt. of the complex salt.

Glass substrate for electronic apparatus

Abstract: PURPOSE:To obtain a transparent glass substrate having excellent hydrofluoric acid resistance and heat-resistance and causing little alkali elusion, by specifying the composition range of the components of alkali metal oxide, CaO, BaO, B2O3, Al2O3 and SiO2. CONSTITUTION:The objective glass substrate has a composition composed of 0-0.5wt.% of R2O (alkali metal oxide), 5-18wt.% of CaO, 0-15wt.% of BaO, 8-24wt.% of B2O3, 5-21wt.% of Al2O3 and 50-70wt.% of SiO2. Among the above glass substrates, most desirable ones are those for electronic apparatus and having a BaO/(CaO+BaO) molar ratio of 0-6. The substrate may contain other impurities such as Fe2O3 and a glass-clarifying agent such as As2O3, Al2O3, As2O5, Sb2O3, Sb2O5, SO3, Cl or F in an amount of <=1wt.% each.

Production of methacrylate polymer

Abstract: PURPOSE:To obtain the titled polymer of a narrow MW distribution in good efficiency, by polymerizing a silyl group-containing methacrylate by using ketene silyl acetal as a polymerization initiator and using a source of (bi)fluoride ions as a cocatalyst. CONSTITUTION:A methacrylate monomer of formula I (wherein R is 1-20 C monovalent hydrocarbon group having at least on silyl group in the carbon chain), e.g., formula II or III, is polymerized in the presence of a ketene silyl acetal of formula IV (wherein R , R , R and R are each H or a 1-10 C monovalent hydrocarbon group), e.g., formula V or VI, as a polymerization initiator and a source of fluoride bifluoride ions (e.g., tetrabutylammonium fluoride or potassium fluoride acidified with hydrofluoric acid) as a cocatalyst to obtain the purpose methacrylate polymer.

Glass for substrate for electronic device

Abstract: PURPOSE: To contrive to improve acid resistance, hydrofluoric acid resistance and heat resistance, by specifying alkali metal oxides (R 2 O), MgO, CaO, BaO, SrO, ZnO, etc. CONSTITUTION: Glass for substrate for electronic devices consists of 0W0.5wt.% R 2 O, 0W10wt.% MgO, 11W25wt.% CaO, 0W5wt.% BaO, 0W5wt.% SrO, 0W5wt.% ZnO, 0W5wt.% B 2 O 3 , 13W30wt.% Al 2 O 3 , 53W70wt.% SiO 2 , 0W3wt.% TiO 2 , 0W3wt.% ZrO 2 and 0W3wt.% R 2 O 5 . The glass has more improved acid resistance than glass of silica soda lime type. The glass has more improved hydrofluoric acid resistance than aluminosilicate glass. Further the glass has improved heat resistance. COPYRIGHT: (C)1988,JPO&Japio

Motor fuel alkylation process utilizing a surfactant containing catalyst to reduce hydrofluoric acid requirements

Abstract: A novel hydrofluoric acid-catalyzed motor fuel alkylation process and catalyst is disclosed which incorporates from 0.5 to 5 vol. % of a cationic or anionic surfactant component in an HF containing acid alkylation catalyst to enable the process to be operated at an olefin-to-acid volumetric feed ratio greater than 1.0 while producing a motor alkylate product with a good octane number.

Method of separating and purifying tantalum and niobium-containing compounds

Abstract: A method for obtaining a high-purity tantalum compound and a high-purity niobium compound comprises: (a) dissolving a crude compound containing tantalum and niobium in hydrofluoric acid optionally with an inorganic acid, adjusting the resulting acidic aqueous solution to have a HF concentration not higher than 4 N, and contacting the acidic aqueous solution with a sparingly water-soluble organic solvent containing from 1.0 to 1.2 equivalents of a sparingly water-soluble quaternary ammonium compound per equivalent of the Ta in the aqueous solution, to selectively extract Ta in the aqueous solution in the organic solution; (b) adjusting the HF concentration of the Ni-containing aqueous solution from step (a) to from 0.5 to 5 N and contacting the aqueous solution with a sparingly water-soluble organic solvent containing from 1.0 to 2.0 equivalents of a sparingly water-soluble quaternary ammonium compound per equivalent of the Ni contained in the aqueous solution, to extract the Ni into the organic solution; (c) contacting the tantalum-containing organic solution obtained in (a) with an aqueous solution containing at least one inorganic acid and/or ammonium salt, and optionally HF, to remove impurities extracted concomitantly into the organic solution; and (d) contacting the Ni-containing organic solution obtained in (b) with an aqueous solution containing HF and optionally an inorganic acid and/or ammonium salt, to remove impurities extracted concomitantly into the organic solution. The method provides a Ta compound and Ni compound, particularly tantalum pentoxide and niobium pentoxide, having high purities (99.999% to 99.9999%) at high yields.

Process for separately recovering uranium and hydrofluoric acid from waste liquor containing uranium and fluorine

Abstract: A process for separately recovering uranium and hydrofluoric acid from a waste liquor containing uranium and fluorine comprises a neutralizing precipitation step wherein a magnesium compound is added to the waste liquor containing uranium and fluorine to form a precipitate and the thus formed precipitate is then separated; a distillation step wherein an aqueous solution of sulfuric acid is added to the precipitate separated in said neutralizing precipitation step to dissolve the precipitate and the thus formed solution is then distilled to recover hydrofluoric acid as a distillate; and a uranium recovery step wherein uranium is recovered from a residue produced by said distillation step.

Spectrophotometric determination of germanium and phosphorus in siliceous materials after hydrofluoric acid distillation

Abstract: Hydrofluoric acid distillation has been applied to the determination of phosphorus and germanium in siliceous materials based on the formation of their heteropolymolybdates. Silicon and arsenic are separated by distillation from phosphorus, germanium and the remainder of the sample. The formation of colourless P2Mo5O236– is employed to avoid the interference of phosphorus in germanium determination. Germanium is determined spectrophotometrically as its heteropolymolybdate and phosphorus gravimetrically by difference.

Process for the preparation of an aqueous alkali metal fluoride solution

Abstract: Process for the preparation of an aqueous alkali metal fluoride solution by treating an ore in which the alkali metal is in the silicoaluminate form. More particularly, the invention is aimed at obtaining a caesium fluoride solution from pollucite. The process for the preparation of an alkali metal fluoride solution according to the invention, which insists in carrying out the treatment of the said ore using hydrofluoric acid, is characterised in that the attack is carried out in the presence of sodium fluoride.

Method for surface activation of water atomized powders

Abstract: A method for pickling and consolidating water atomized metallic powders to reduce surface oxides. The technique includes introducing the powder into an acid bath--preferably nitric acid and hydrofluoric acid, rinsing the powder, introducing the powder into an alkaline bath, rinsing the powder and then consolidating the powder into a workpiece. Alternatively, the powder can be additionally introduced into a second acid bath and/or placed into a finishing boric acid bath before consolidation.

Statistical analysis of the removal of aluminum and magnesium impurities from wet‐process phosphoric acid

Abstract: The present paper relates to the treatment of crude wet-process phosphoric acid with ammonium nitrate and hydrofluoric acid to precipitate aluminum and magnesium impurities in the form of an easily separable phase: (NH4)xMgyAlz (F, OH)6.2 H2O. To check the effect of some concentration factors on this reaction, an orthogonal central composite design is realized with three variables: %Al3+, %NH4+ and %F−. It is concluded that the amount of aluminum in acid is the limiting factor of magnesium precipitation. Thus complete removal of magnesium, which is a major impurity in wet-process phosphoric acid, can be obtained by adding to the crude acid extra soluble aluminum salt simultaneously with hydrofluoric acid and ammonium nitrate.

Recovery of hydrogen fluoride from an aqueous solution containing ammonium fluoride and hydrogen fluoride

Abstract: RECOVERY OF HYDROGEN FLUORIDE FROM ANAQUEOUS SOLUTION CONTAINING AMMONIUM FLUORIDE AND HYDROGEN FLUORIDE ABSTRACT OF THE DISCLOSURE A method of recovering HF from an aqueous solution containing NH4F and HF is provided. The solution is contacted with a water-immiscible, amine-containing extractant which extracts HF in preference to NH4F.The HF:NH4F molar ratio of the solution, the amine, the concentration of the amine in the extractant and the contact temperature are selected so as to form an HF-loaded organic liquid phase having an HF:amine molar ratio of at least about 1.2. The extractant is preferably selected from amines, amine-HF complexes, quaternary amine fluorides and mixtures thereof with inert organic diluents. After equilibration, the HF-loaded amine is separated from the solution and HF is stripped therefrom in an amount sufficient to lower the HF:amine molar ratio by at least about 0.2.

Method and device for decomposition thin film of semiconductor substrate

Abstract: PURPOSE:To execute a thin film decomposition with a high efficiency by heating hydrofluoric acid in a closed container, cooling and condensing the generated vapor, and dropping it as a droplet to a thin film on a semiconductor substrate CONSTITUTION:After packing a refrigerant chamber 12b with a refrigerant C such as liquid nitrogen, etc, a hydrofluoric acid liquid L in a liquid tank 7 is heated and evaporated by a heater 11 Vapor of the hydrofluoric acid liquid L which is evaporated in a closed container 1 is quenched and condensed by the surface of a conical body 12a of a cooling member 12, and dropped down as a liquid droplet (d) to the center of a thin film (f) on a rotary supporting base 8 In such a case, since the supporting base 8 is rotating, the liquid droplet (d) which is dropped down onto the thin film (f) spreads radially and uniformly from the center of a semiconductor substrate W, the liquid contacts to the whole surface of the thin film (f) and the thin film (f) is dissolved, and the thin film decomposition is executed efficiently Also, a decomposed liquid l containing a dissolved component of the thin film (f) flows into a groove 8c of a loading part 8a and collected by a centrifugal force, and analyzed by a frameless atomic absorption device, etc

Production of uranium tetraflouride

Abstract: In a process for the production of uranium tetrafluoride (UF4), uranic oxides, UO3 and U3O8, are dissolved in dilute sulphuric acid (H2SO4) and hydrofluoric acid (HF) is added to produce a uranyl fluoride-sulphate solution which is electrolytically reduced to uranous fluoride-sulphate complexes from which hydrated uranium tetrafluoride is precipitated by the addition of dilute HF at elevated temperature (preferably above 90 deg.C). The uranyl fluoride-sulphate solution can alternatively be produced by dissolving uranyl fluoride in H2SO4 or from uranyl sulphate solutions (derived from solvent extraction or ion exchange purification processes) conditioned with HF.

Production of high-purity silica

Abstract: PURPOSE:To produce high-purity silica at a low cost, by dissolving a low-purity silica source in a mixture of hydrofluoric acid and sulfuric acid, distilling the solution and adding ammonia water to the resultant silicon fluoride to form a silica gel CONSTITUTION:A compound or mixture utilizable as a silica source (eg white carbon) is dissolved in a liquid mixture of hydrofluoric acid and sulfuric acid The hydrofluoric acid is preferably the one having a concentration of about 45% and its amount is selected to be sufficient to convert silicon in the raw material to fluoride The sulfuric acid is preferably the one having a concentration of about 60% and its amount is selected to be sufficient to convert the ingredient metals in the raw material to sulfides The solution produced by the above method is distilled at about 120 degC to recover a fraction composed of high-purity silicon fluoride and water The fraction is added with ammonia water of about 25% concentration and the formed silica gel is separated by filtration, washed with water, dried and calcined to obtain silica having a purity of higher than five-nines

Production of 1,1-dichloro-1,2,2,2-tetrafluoroethane

Abstract: PURPOSE:To inexpensively obtain the title high-purity compound without preparing by-products, by using readily obtainable 1,1,2-trichloro-1,2,2-trifluoroethane as a starting raw material, carrying out isomerization reaction and fluorinating the resultant compound with hydrofluoric acid. CONSTITUTION:1,1,2-Trichloro-1,2,2-trifluoroethane is used as a starting raw material and isomerized preferably in the presence of an isomerizing catalyst in a gas phase under normal pressure or under pressure or in a liquid phase under pressure at 50 deg.C-550 deg.C, especially 100 deg.C-400 deg.C to give 1,1,1-trichloro-2,2,2- trifluoroethane. Then the reaction product is fluorinated with hydrofluoric acid preferably in the presence of a fluorinating agent in a gas phase under normal pressure or in a liquid phase under pressure at 50-550 deg.C, especially 50 deg.C-450 deg.C to give the aimed compound. Preferably 0 or Cl is present to maintain catalytic activity.

Method of controlling the crystal grain size of uranium dioxide pellet

Abstract: A method of controlling the crystal grain size of UO2 pellets is disclosed, which comprises (1) providing an aqueous uranyl solution which is free of hydrofluoric acid and nitric acid and which contains uranyl fluoride (UO2 F2) and/or uranyl nitrate (UO2 (NO3)2) as a uranium component, (2) reacting with ammonia said aqueous uranyl solution to precipitate ammonium diuranate (ADU), while adjusting the ratio of said uranium components to a predetermined value within the range varying from the ratio 100% of uranyl fluoride and 0% of uranyl nitrate to the ratio 0% of uranyl fluoride and 100% of uranyl nitrate, adjusting the uranium concentration of the reaction mixture to 50 to 1,000 gU/liter and also adjusting the rate of contact between said uranium component in said aqueous uranyl solution with ammonia to at least 2 moles NH3 /min/mole U, (3) calcining and reducing said ADU precipitate to form UO2 powder, and (4) molding and sintering said UO2 powder, thus producing UO2 pellet having a predetermined crystal grain size in the range varying from 5 to 100 micrometers

Recovering method for metal

Abstract: PURPOSE:To separate a platinum metal by a simplified process obviating the necessity of heating means by bringing a platinum metal-containing titanium waste catalyst into contact with an aqueous solution of hydrofluoric acid to dissolve titanium. CONSTITUTION:The waste titanium catalyst coated with platinum metal is brought into contact with the >=about 5wt% aqueous solution of hydrofluoric acid by means of immersion, spraying, etc. The above contacting operation is carried out at ordinary temp. or under cooling to a slight extent. By this treatment, the titanium in the titanium spent catalyst is dissolved in the aqueous solution of hydrofluoric acid and platinum-metal oxides such as RuO2, etc., at the titanium surface are exfoliated. Insoluble matter of the exfoliated platinum-metal oxides is collected by filtration, centrifugation, etc.

Making method for preparing calcium fluosilicate as the rough material of calcium fluoride and pure fluosilicic acid

Abstract: Process for the production of anhydrous calcium fluosilicate from anhydrous calcium chloride and impure fluosilicic acid solution, a by-product of the acid treatment of phosphorus ores containing fluorine, characterized in that a calcium fluosilicate dihydrate is precipitated at low temperature and quantitatively by suitable adjustment of the fluosilicic acid concentration and the molar ratio CaCl2/H2SiF6 and that after filtration, washing and drying of the precipitate, an anhydrous calcium fluosilicate which can be easily decomposed by heat treatment is obtained to restore calcium fluoride and silicon tetrafluoride suitable for the manufacture of pure hydrofluoric acid and fluosilicic acid. For gravimetric concentrations of H2SiF6>25% and molar concentration ratios CaCl2/H2SiF6 between 2 and 5, the yields of the anhydrous calcium fluosilicate obtained are greater than 94%.

Extraction of niobium and tantalum with bis-2-ethylhexyl acetamide

Abstract: ABSTRACT The extraction of Nb and Ta from acid solutions with bis-2-ethylhexyl acetamide and the stripping of these metals with sulphuric acid solutions were investigated. The organic phase was a binary solution of bis-2-ethylhexyl acetamide and xylene, while the aqueous phase was composed of hydrofluoric acid solution or hydrofluoric-sulphuric acid solution containing 3.5-13 Kg/m3 Nb and 5-10 Kg/m3 Ta. Sulphuric acid, hydrofluoric acid and nitric acid were used as salting out agents to understand the effect on the extraction. Niobium and tantalum were not sufficiently extracted from hydrofluoric acid solutions, whereas the extraction of both metals remarkably increased with an addition of sulphuric acid to the aqueous phase. Both metals were completely co-extracted under the aqueous condition of 6N hydrofluoric acid and 8N sulphuric acid. The stripping occurred for both metals with high efficiency when water or dilute sulphuric acid was used as a stripping agent. The increase in sulphuric acid c...