Showing papers on "Hydrofluoric acid published in 1988"

Hydrofluoric acid-induced hypocalcemia

Abstract: Among patients exposed to hydrofluoric acid the potentially lethal effect of calcium depletion induced by binding with fluoride ion has not been well reported. Three patients exposed to hydrofluoric acid had acute fluoride poisoning with serum calcium levels equal to or below 4.1 mgm/dl. Treatment included administration of large amounts of calcium, both intravenously and by subsechar injection, to replenish the biologically active calcium and to bind fluoride. This report describes successful treatment of two survivors, apparently the first two, of severe hypocalcemia caused by hydrofluoric acid.

Surface-micromachining processes for electrostatic microactuator fabrication

Abstract: Etch characteristics are discussed of three forms of hydrofluoric acid, used as the micromachining etchant for fabricating a rotary variable-capacitance micromotor structure from polycrystalline silicon (poly-Si) thin films. Low-pressure chemically vapor deposited SiO/sub 2/ (LPCVD LTO) is used to form the sacrificial layers and LPCVD Si/sub 3/N/sub 4/ is used as an electrical isolation layer for the micromachined structure. 7:1, NH/sub 4/F:HF buffered HF (BHF), 48 wt.% concentrated hydrofluoric acid (LHF), and HF vapor in air (VHF) are evaluated at 20 degrees C for etch rate and selectivity, and attack of four types of LPCVD poly-Si films; POCl/sub 3/-doped or undoped, with or without 1150 degrees C annealing. Both BHF and VHF are found to damage POCl/sub 3/-doped poly-Si films, possibly by attack of grain boundaries. VHF is found to be effective for micromachining suspended structures since it avoids deformation of microstructures due to surface tension effects during drying after wet etching with LHF or BHF. >

Etching solution for evaluating crystal faults

Abstract: An etching solution used for evaluating crystal defects in a silicon wafer is disclosed. The etching solution is characterized by consisting of acetic acid, hydrofluoric acid, nitric acid, silver nitrate, and copper nitrate, and is very advantageous in considera­tion of the operator's health, since it does not contain Cr⁶⁺. The etching solution has a sufficiently high etching rate and detection properties.

Efficiency of oxygen plasma cleaning of reactive ion damaged silicon surfaces

Abstract: It is demonstrated with the use of in situ x‐ray photoemission spectroscopy, secondary ion mass spectrometry, and transmission electron microscopy, that the commonly practiced in situ oxygen plasma/hydrofluoric acid dip treatment of reactive ion damaged silicon surfaces is insufficient in removing all reactive ion etching (RIE) related contaminants and damage. For CHF3/CO2 RIE the residual modifications are shown to be fluorine and carbon contamination and deeper lying modifications, e.g., hydrogen‐induced extended Si defects. An enhanced silicon oxidation rate during air exposure has been observed for post‐RIE‐treated silicon, which correlates to the amount of residual fluorine.

Process and apparatus for etching semiconductor surfaces

Abstract: A process and apparatus for etching semiconductor surfaces, in particular,ilicon, with a mixture containing nitrogen-oxygen based compounds as oxidizing compounds, hydrofluoric acid as the component which dissolves the oxidation product, and sulfuric acid, optionally with phosphoric acid added, as a carrier medium. This mixture makes it possible to design the process as a cyclic process in which oxygen supplied to the system ultimately effects an oxidation of the material to be etched, and the product of its oxidation is removed from the circuit. The process is noteworthy for its low usage of reagents and because it is not harmful to the environment.

Surface pretreatments of aluminium for electroplating

Abstract: The effects of concentration and temperature of sodium hydroxide and nitric acid + hydrofluoric acid pretreatment solutions on the morphology of aluminium surfaces have been studied SEM/EDS observations indicated that NaOH solutions produced etch concavities on the surface, but failed to etch second-phase particles, namely FeAl3 The acid solutions, however, succeeded in preferentially removing these particles, while they did not change the surface roughness of the aluminium In an attempt to improve the coverage rate of zinc alloy films, chemically deposited prior to nickel electroplating, a new pretreatment sequence has been designed It consists of a double-step nitric + hydrofluoric acid solution immersion, with NaOH immersion treatment between the two acid immersion steps The results obtained with this new sequence indicate that the first acid step removes most of the biggest FeAl3 particles, as well as the previous oxide layer, while the alkaline step generates a micro-roughness on the surface whereby a net of shallow cellular cavities, as in a honeycomb structure, forms The last acid treatment preferentially etches the small FeAl3 particles and the most protuberant inhomogeneities of the surface This new pretreatment sequence proved to be more effective than those previously reported in the literature, in terms of producing a good surface on which zinc alloy films could develop The adhesion of nickel electrodeposits to such a surface reached values one order of magnitude higher than those for conventional two-step sequences Interpretation of these results is based on the improved chemical homogeneity of the surface resulting from the removal of second-phase particles and on the small (ca 1 μm in diameter) and uniform dimensions of the cells produced by the etch treatment This effectively leads to a good surface coverage during the zincate treatment, as intially intended

Alkali-free glass

Abstract: PURPOSE:To ensure superior acid and hydrofluoric acid resistances, superior meltability and moldability by providing a compsn consisting of a specified amt, in total, of specified amts of SiO2, Al2O3 and B2O3, specified amts of CaO, BaO, ZnO, TiO2 and ZrO2 and a specified amt or less of MgO CONSTITUTION:This alkali-free glass consists of, by weight, 75-80%, in total, of 54-60% SiO2, 10-15% Al2O3 and 6-10% B2O3, 8-15% CaO, 4-10% BaO, 1-6% ZnO, 03-4% TiO2 and/or ZrO2 and 0-2% MgO and contains practically no alkali metal oxide Since this alkali-free glass has superior heat, acid and hydrofluoric acid resistances, it is suitable for use as the material of a substrate on which a thin metal or metal oxide film is formed and patterned by etching This alkali-free glass gives a homogeneous glass product free from bubbles, striae and foreign matter owing to its superior meltability and moldability

Hydrogen fluoride vapor containment and neutralization

Abstract: A method of containing and neutralizing a hydrofluoric acid spill which comprises the steps of detecting a hydrofluoric acid spill, and then drenching the hydrofluoric acid spill area with a drench composition comprising water, and an alkali agent, or water an alkali agent and a surfactant, or water an alkali agent, a surfactant and a foaming agent. The alkali agents are present in an amount of 0.1 to 10 parts per 100 parts of water.

On the modelling of multicomponent acid extraction with long-chain aliphatic amines

Abstract: The solvent extraction of phosphoric, hydrochloric, sulphuric, hydrofluosilicic and hydrofluoric acids with long-chain aliphatic amins is modelled. Pure acid equilibria are based on existing isotherms or calculated extraction constants when only experimental data are available. For binary mixtures binary combinations of acid complexes are added. In the aqueous phase Bromley's model for electrolytes is used for calculation of ionic activity coefficients and the appropriate association/dissociation equilibria taken into account for calculation of ionic strength. For the organic phase an empirical model for the non-ideal behaviour of phosphoric acid is used. For multicomponent mixtures at low acid concentrations the model calculates the extraction of phosphoric, hydrochloric and sulphuric acid almost quantitatively. For hydrofluosilicic and hydrofluoric acid the calculations are less precise and further information is needed about the different fluoride exchange equilibria involved.

Hydrogen fluoride vapor containment

Abstract: A method of containing a hydrofluoric acid spill which includes the steps of detecting the spill, drenching the hydrofluoric acid spill area with an aqueous drench, drenching the hydrofluoric acid area with an aqueous solution composed of at least one foam generating surfactant, a foam stabilizer and a phase transfer agent. The drenching steps may be performed in sequence or concurrently.

Method for producing titanium fluoride

Abstract: A method for producing titanium fluoride comprises: a dissolution process (2), wherein iron-containing titanium material (1) is dissolved in solutions containing hydrofluoric acid (3), fluoride solutions (4) being produced; a first crystallization and separation process (8), wherein ferric fluoride is crystallized and ferric fluoride crysals (10) thus obtained are separated from the fluoride solutions by cooling the fluoride solutions, crude titanium fluoride solutions (9) being produced; a second crystallization and separation process (15), wherein ammonium fluoride salt (16) [mixed salt of (NH₄)₂ TiF₆ and (NH)₃FeF₆ ] is crystallized and separated by mixing ammonium fluoride solutions (26) with the crude titanium solutions to obtain a mixture and concentrating the mixture; a first pyrolysis process (19), wherein the ammonium fluoride salt is pyrolyzed at a temperature of from 300 to 800 ° C in a stream of dry gas after having dried the ammonium fluoride, ferric fluoride (FeF₃) in a solid state and TF₄, HF and NH₃ in a gaseous state being produced; and a condensation and separation process (22), wherein the TiF₄ HF and NH₃ in a gaseous state are condensed at a temperature of from 20 to 280° C and the TiF₄ in a solid state is separated from HF and NH₃ in a gaseous state.

Method for reducing hot-electron-induced degradation of device characteristics

Abstract: Hot-electron-induced degradation of a semiconductor device (10) is reduced by converting the silicon surface (18) to a fluorinated-silicon compound interface region (23). The fluorinated-silicon compound interface region (23) is formed by etching the device (10) in a fumer (30) using anhydrous hydrofluoric acid. After a sacrificial oxide is grown over the silicon surface (18), the device (10) is placed in a container (32). A mixture of nitrogen, moistened nitrogen and nitrogen/anhydrous hydrofluoric acid is injected into the container (32) to conduct the etch. The anhydrous hydrofluoric acid converts the silicon to a fluorinated-silicon compound, such as H 2 SiF 6 , and water. The fluorinated-silicon compound interface region (23) has stronger molecular bonds than the typical hydrogen-silicon formed at the oxide/silicon interface and is, therefore, less likely to be broken apart by hot-electrons.

Process for the recovery and/or regeneration of acids from metalliferous solutions of these acids

Abstract: In the pickling, etching, chemical milling etc. of steels, stainless steels, special alloys and special metals and also when dissolving these metals, metalliferous solutions of the acids used arise in the course of these processes, and these must either be disposed of by neutralisation or used in expensive processes in order to recover the acids and metals. Nitric acid or a nitric acid/hydrofluoric acid mixture are obtained or recovered according to the invention by spray-roasting the solutions at temperatures from 200 to 500 DEG C in a reactor (1) followed by absorption and condensation of the resulting gases in columns (7, 8) at temperatures from 0 to 70 DEG C.

Photoelectrochemical evolution of elemental fluorine at TiO2 electrodes in anhydrous hydrogen fluoride solutions

Abstract: Although elemental fluorine has been known for more than 100 years, it is still produced by Moissan's original method, electrolysis of anhydrous HF/alkali fluoride solutions. Only one convenient alternative route for preparing fluorine has been reported to date. Several oxide and oxyfluoride semiconductors have valence band edges that are positive of the F/sup -/, F/sub 2/ standard potential, and holes photogenerated in the valence band of these materials should, in principle, be capable of oxidizing F/sup -/ to F/sub 2/. In aqueous fluoride-containing solutions other processes such as water oxidation and photoanodic corrosion compete effectively with F/sup -/ oxidation, and no fluorine is formed. Even in nonaqueous solutions these wide bandgap semiconductors photocorrode, unless sufficient reductant is present to compete for photogenerated holes. In anhydrous solutions containing sufficient quantities of fluoride ion is reasonable to expect that fluorine might be generated photoelectrochemically at a semiconductor surface which is somehow stabilized against photocorrosion. They report here that elemental fluorine is evolved at n-type TiO/sub 2/ electrodes in anhydrous HF/NaF solutions. Using bandgap illumination (365 nm) gaseous F/sub 2/ is produced with a sizable photovoltage and high power conversion and current efficiencies. While electrode photocorrosion occurs to some extent in all thesemore » experiments, it may be minimized greatly by using fluorine-doped TiO/sub 2/ electrodes.« less

Etching of Tungsten and Tungsten Silicide Films by Chlorine Atoms

Abstract: Thin films of tungsten and tungsten silicide were etched both within and downstream from a Cl/sub 2/ plasma discharge at 200 mtorr pressure and temperatures below 150/sup 0/C. When samples were positioned downstream from the discharge, etching proceeded solely by chemical reaction of the film with chlorine atoms. Without a discharge, molecular chlorine did not etch tungsten or tungsten silicide. Downstream and in-plasma tungsten etch rates were approximately equal at 110/sup 0/C, but the chlorine atom etch rate dropped more rapidly than the in-plasma etch rate as temperature decreased. The chemical reaction between chlorine atoms and the tungsten film was proportional to the gas phase Cl atom mole fraction. A pretreatment consisting of either a dilute hydrofluoric acid dip or a short plasma etch cycle was necessary for atom etching of tungsten silicide films. The etch rate of tungsten silicde in Cl/sub 2/ plamsas were approximately an order of magnitude higher and less temperature sensitive than those in the downstream (atom) configuration.

Formation of through-hole on glass plate

Abstract: PURPOSE:To obtain a glass plate having many through-holes little in the variance of pore diameter by photoetching the glass plate wherein wettability is enhanced by using a surface active agent. CONSTITUTION:The wettability of a glass plate 1 is enhanced by immersing the glass plate 1 having 0.1-0.5mm thickness wherein photoresist layers 2 are formed on all surfaces excepting exposed parts 3, where through-holes 4 are formed, into an aq. soln. contg. 0.0001-10wt% fluorine-base surface active agent. Then many fine through-holes 4 are formed on the glass plate 1 by immersing this glass plate 1 into etching liquid contg. hydrofluoric acid and ammonium fluoride or the like.

Method for synthesizing diamond by explosion in water

Abstract: PURPOSE: To make it possible to easily repeat explosion by a desired number of repetitions and to facilitate the recovery of a reaction product by exploding a starting material mixture of an explosive with graphite in water. CONSTITUTION: A starting material mixture of an explosive with graphite is press-molded so as to attain ≥1.4 g/cm 3 density and the resulting molded body is charged into a pipe with one end or both ends open as required. The molded body or the pipe is suspended in water in a water tank at ≥50cm depth of water. After explosion, the supernatant liq. is removed and the deposit is recovered. The metals in the deposit are dissolved and removed with nitric acid, the residual graphite is removed with a mixed soln. of hydrochloric acid and nitric acid and then the deposit is treated with a mixed soln. of hydrofluoric acid and nitric acid to obtain high purity diamond. COPYRIGHT: (C)1990,JPO&Japio

Process for recovering nitric acid and hydrofluoric acid from waste pickle liquors

Abstract: A method for regenerating a waste liquor containing nitric acid and hydrofluoric acid to recover highly pure nitric and hydrofluoric acids therefrom. The method comprises adding hydrofluoric acid, or an acid mixture of nitric and hydrofluoric acids having a major content of the hydrofluoric acid, to a nitric acid and hydrofluoric acid waste liquor, and subjecting the resulting mixture to dialysis with an ion-exchange electrodialyzer to recover the dialyzed acids. The acid-removed solution is neutralized to cause a precipitate to form and the precipitate is separated. The resultant solution is subjected to an ion-exchange membrane electrodialyzer using a combination of a bipolar membrane, an anion-exchange membrane and a cation-exchange membrane for separation into the acids and the alkali, which are subsequently recovered. The process has a high current efficiency and high recovery rates for acids.

Method of producing NF3

Abstract: A method for producing NF 3 by fused salt electrolysis of electrolytes containing hydrofluoric acid salts of ammonia and of hydrazine and electrolyte mixtures for use therein.

Acid washing-passivating paste for stainless steel

Abstract: It is widely used for cleanning the welding seams of stainless steel and oxides in the proximity, esp. for removing the scales of 2~3 mm thickness which remains on the closed ends of stainless steel containers after high-temp. treatment in a red furnace. The paste offers both acid-washing and passivating functions. The steel treated with this invention can reproduce its original silver luster. It contains nitrate acid and hydrofluoric acid, and uses the thickner (magnesium stearate), inorganic filler (magnesium nitrate) and buffering corrodent (sodium polyphosphonate) as carriers.

Process for preparing vinylidene fluoride by the direct fluorination of vinylidene chloride

Abstract: Vinylidene fluoride is produced by the gaseous phase reaction of vinylidene chloride with hydrofluoric acid at a temperature of from about 400° to 700° C. in the presence of oxygen and a catalyst containing AlF 3 either alone or in combination with a transition metal fluoride selected from iron, cobalt, chromium, nickel, zinc and combinations thereof.

Analysis of nickel-base and cobalt-base heat-resistant alloys by single column anion exchange chromatography and inductively coupled plasma-atomic emission spectrometry

Abstract: Single-column anion exchange chromatography has been combined with inductively coupled plasma-atomicemission spectrometry (ICP-AES). A complex Ni-base or Co-base heat-resistant alloy was dissolved in a mixed acid containing hydrofluoric acid. A strongly basic anion exchange resin was used to separate the alloying elements. Hydrofluoric acid was removed by fuming or was masked after elution in order to use a glass sample introduction system for the ICP-AES. Thirteen alloying elements were determined in Ni-base and eleven in Co-base heat-resistant alloys. Good results were obtained by both the calibration curve method and the internal standard method. Synthetic standard solutions were used for the calibration. Magnesium was used as an internal standard element.

Process for the preparation of aromatic aldehydes

Abstract: Process for the preparation of aromatic aldehydes by formylation of aromatic derivatives in liquid hydrofluoric acid in the presence of boron trifluoride.

Simultaneous multielement analysis of zeolite catalysts by inductively-coupled plasma atomic emission spectrometry

Abstract: A method comprising digestion of zeolites with an acid mixture followed by inductively-coupled plasma atomic emission spectrometry (ICP-AES) has been established for the simultaneous determination of Al, Na, La and Si in various zeolite samples. Various aspects including sample digestion, instrumental interference effects as well as analytical performance and applicability of the established method have been investigated in detail. The results indicated that aqua regia in combination with hydrofluoric acid was effective for decomposition of a wide variety of zeolite samples. The effects of borate and fluoride ions in the digested sample solution on the ICP-AES determination have been carefully investigated. The method established will be generally applicable for the simultaneous determination of Al, Na, La and Si in zeolite with a precision of ≤5%. The analytical results obtained were checked by comparison with classical wet chemistry methods and found to be in reasonably good agreement. Application to the kinetic study of La-NaY exchange reaction was also performed.

Method for recovering platinum group metal from waste catalyst

Abstract: PURPOSE:To efficiently recover platinum group metals by subjecting a waste catalyst of an oxide carrier contg. the platinum group metals and alumina to acid dissolution and separating and removing the alumina from the resulted aq. soln. by diffusion dialysis with a cation exchange membrane. CONSTITUTION:The waste catalyst of the oxide carrier contg. part or whole of the platinum group metals and alumina is subjected to the acid dissolution. An acid prepd. by adding an oxidizing agent such as gaseous chlorine and at least one kind among nitric acid, sulfuric acid, hydrofluoric acid and phosphoric acid to hydrochloric acid is suitable as the acid for said treatment. The aq. soln. obtd. in such a manner is subjected to the diffusion dialysis by using the ion exchange membrane. The concn. of Al in the aq. soln. is kept at ions are thereby migrated through the cation exchange membrane to a recoverying liquid side. On the other hand, the platinum group metals on the raw liquid side form a chlorocomplex and do not flow to the recoverying liquid side. The platinum group metals are thereby easily recovered at a high recovery rate.

Synthesis of 1-chloro-1, 1-difluoroethane

Abstract: The invention relates to a process for the manufacture of 1-chloro-1,1-difluoroethane in the liquid phase by reacting hydrofluoric acid with 1,1,1-trichloroethane and/or 1,1-dichloro-1-fluoroethane. The selectively is improved by using a perfluoroalkanesulphonic acid, in particular trifluoromethanesulphonic acid, as a catalyst.