Showing papers on "Hydrofluoric acid published in 1972"

Dislocation Etch for (100) Planes in Silicon

Abstract: A new etch composed of a dilute aqueous solution of an alkali dichromate and hydrofluoric acid, for suitably revealing dislocations and other lattice defects in (100) planes of silicon, is reported. The etch is fast (typically 5 min), brings out both lineage (low angle grain boundaries) and slip lines, and works over a wide range of resistivities for n‐ and p‐type material. The application of the etch is not restricted to (100) planes; dislocation etch pits are formed on all crystallographic orientations. The same etching characteristics were found with dilute aqueous solutions prepared from various chromium compounds and hydrofluoric acid.

Etch Channel Formation during Anodic Dissolution of N‐Type Silicon in Aqueous Hydrofluoric Acid

Abstract: Anodic dissolution of n+‐, n‐, and n−‐type silicon in 5% aqueous hydrofluoric acid at moderate current densities results in the formation of etch channels which propagate in crystal‐oriented directions in the monocrystal. Density and depth of the channels are a function of the applied voltage, the donor concentration, and the exposure time of the electrolyte under anodic bias conditions. It is assumed that the channel formation originates at spots with a lower breakdown voltage of the depletion layer which exists on the surface of the crystal under reverse bias conditions. Channel formation in epitaxial n layers can occur during preferential electrochemical etching of the n+ substrate of structures. This is the case when the interface profile is not abrupt and when defects in the epitaxial layer are present. Some methods of restricting the influence of channels occurring during device processing are mentioned.

Semiconductor device and method of producing the same

Abstract: A semiconductor device and a method of producing the same. The semiconductor device comprises a silicon single crystal including a porous substance formed so as to advance from surface area toward inside area of said silicon single crystal. The porous substance is produced on the silicon single crystal by utilizing said crystal and a conductive metal material which is not soluble to hydrofluoric acid as electrodes, applying a positive direct current voltage to the silicon single crystal and a negative direct current voltage to the other metal electrode, and carrying out an electrolysis in an aqueous solution of the hydrofluoric acid.

Oil recovery process

Abstract: A process for recovering petroleum from a subterranean reservoir by flooding with a surfactant wherein the adsorption of surfactant by the reservoir rock is inhibited by treating the reservoir with a water-soluble fluorine containing compound such as hydrofluoric acid or sodium fluoride prior to injecting the surfactant Preferably, treatment is accomplished by injecting an aqueous solution of hydrofluoric acid or sodium fluoride into the reservoir in an amount sufficient to satisfy substantially all of the adsorption capacity of the reservoir matrix followed by injection of an aqueous solution of the surfactant The hydrofluoric acid or sodium fluoride and the surfactant solution can be subsequently displaced through the formation by any convenient aqueous drive fluid including water

Production of hf from fluorine by-products

Abstract: Fluorine values are recovered from fluosilicic acid aqueous streams by electrodialytic water-splitting of fluoride salt to hydrofluoric acid and hydroxide base and further optionally concentration of the hydrofluoric acid via membrane electro-dialysis, to produce anhydrous HF.

Alkylation process with recovery and regeneration of fluorosulfuric acid catalyst

Abstract: The present invention provides an improved alkylation process comprising: contacting an olefin and a paraffin with an alkylation catalyst comprising fluorosulfuric acid, at alkylation conditions, in an alkylation reactor, thereby forming a hydrocarbon phase comprising alkylate reactor product and containing at least a portion of the catalyst; washing the hydrocarbon phase with an acid comprising sulfuric acid to form an acid phase containing fluorosulfuric acid, hydrofluoric acid, and sulfuric acid; contacting the acid phase with water thereby converting at least a portion of the fluorosulfuric acid to hydrogen fluoride and sulfuric acid; removing at least a portion of the hydrogen fluoride from the acid phase by contacting the same with a paraffin such as n-butane thereby forming a hydrocarbon phase containing hydrogen fluoride; treating the hydrocarbon phase with sulfur trioxide to regenerate the fluorosulfuric acid; and recycling at least a portion of the regenerated fluorosulfuric acid to the alkylation zone to be used as an alkylation catalyst therein.

Solvent extraction and separation of zirconium, niobium and tantalum by 2-carbethoxy-5-hydroxy-1-(4-tolyl)-4-pyridone

Abstract: Extraction of zirconium, niobium and tantalum from oxalic and hydrofluoric acid solutions, by 2-carbethoxy-5-hydroxy-1-(4-tolyl)-4-pyridone (HA) dissolved in chloroform was studied. Extraction mechanism for the extraction of zirconium from oxalate solutions and of niobium from fluoride solutions is proposed. Separation of zirconium and niobium from oxalate solution as well as from fluoride solution and tantalum and niobium from fluoride solution is described. Back-extraction of these metals is possible by hydrofluoric and oxalic acid. Results obtained show that the efficiency of extraction by HA decreases in the sequence tantalum > niobium > zirconium.

The determination of tungsten and silicon in highly alloyed materials by atomic-absorption spectroscopy

Abstract: Tungsten and silicon are determined in the presence of large amounts of iron, nickel, cobalt, molybdenum and other constituents of highly alloyed materials by means of atomic-absorption spectrophotometry with a nitrous oxide-acetylene flame. Complete dissolution is effected in a mixture of aqua regia and hydrofluoric acid, which necessitates the entire use of plasticsware. Inter-element effects are both numerous and complex, and the method of standard addition is recommended for calibration purposes.

Method of separating plutonium from uranium and from other transuranium elements

Abstract: Plutonium is separated from uranium and other transuranium elements by subjecting an aqueous solution in dilute nitric acid of the elements to be separated to electrolytic extraction by counter-current or cross-current ion migration in the presence of a complexing agent, preferably acetic acid or a mixture of hydrofluoric acid with an alkali metal fluoride, until plutonium and the other elements present accumulate in separate portions of the solution which are thereafter separately withdrawn.

Determining boron in glass by flame emission spectroscopy.

Abstract: A method has been developed at the Oak Ridge Y-12 Plant1 that will determine the percentage quantities of boron in borosilicate glass by flame emission spectroscopy The sample is dissolved in hydrofluoric acid, nebulized into a nitrous oxide-acetylene flame, and a measurement made of the BO2 band emission at 5180 angstroms Glass containing at least 10 weight percent boron can be analyzed The relative standard deviation of the method is 51 percent Approximately 10 samples (2 aliquots each) can be analyzed in four hours

Acid catalyzed alkylation of hydantoin

Abstract: 1. A PROCESS FOR THE PRODUCTION OF A 1-ALKYLATED HYDANTOIN WHICH COMPRISES REACTING AN OLEFIN OF FROM 3 TO 8 CARBON ATOMS AND A HYDANTION, SAID HYDANTION HAVING FORMULA: 2,4-DI(O=),3-R3,5-R,5-R1-IMIDAZOLIDINE WHEREIN R AND R1 ARE SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, LOWER ALKYL, BENZYL AND PHENYL, AND R3 IS SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, LOWER; ALKYL AND BENZYL, IN THE PRESENCE OF A STRONG ACID SELECTED FROM THE GROUP CONSISTING OF SULFURIC AICD PHOSPHORIC ACID, FLUOROSULFONIC ACID, PHOSPHORIC ACID, BF3, HYDROFLUORIC ACID AND HYDROCHLORIC ACID, AND SAID ACID BEING PRESENT IN AN AMOUNT SUFFICIENT TO AT LEAST PARTIALLY DISSOLVE SAID HYDANTION AND MAINTAIN THE REACTION IN A FLUID STATE, AT A TEMPERATURE IN THE RANGE FROM ABOUT -75* C. TO ABOUT 25* C.

Recovery of hydrofluoric acid in alkylation processes

Abstract: Propane is employed in the HF rerun zone as a substitute for isobutane to strip HF from the acid-soluble oils, avoiding the losses attendant to the use of isobutane.

Determination of total phosphorus in detergents by atomic absorption spectroscopy.

Abstract: A method is described for the determination of phosphorus in solid detergents. Nitric acid plus perchloric acid followed by treatment of the residue with hydrofluoric acid serves admirably to dissolve detergents in aqueous solutions. The phosphorus is determined by atomic absorption spectroscopy using a phosphorus hollow cathode tube. The method of additions is utilized to overcome matrix interference. The values obtained for phosphorus are in good agreement with a standard colorimetric method. No loss occurred by volatilization.

Coating ferrous metals

Abstract: PROCTETIVE COATINGS ARE APPLIED TO FERROUS METALS BY: (A) ETCHING THE METAL FIRST IN NITRIC, THEN IN HYDROFLUORIC ACID; (B) FORMING A MAGNETITE COATING ON THE ETCHED METAL BY HEATING IN CONTACT WITH AQUEOUS HYDRAZINE, AND (C) APPLYING AN ORGANIC COATING TO THE MAGNETITECOATED FERROUS METAL.

Time differential perturbed γγ-angular correlation studies with 181 Ta in frozen aqueous solutions

Abstract: Time-differential measurements of the 133 keV to 482 keV γγ-angular correlation of181Ta have been performed in frozen solutions of hafnium fluoride in dilute hydrofluoric acid as a function of temperature. Time-dependent perturbations were observed between −40 °C and −80 °C. Below −100 °C the interaction became static.

Washing Treatment to Doped Tungsten Powder by Hydrofluoric Acid

Abstract: A tungsten filament of incandescent lamp recrystallizes and becomes brittle when the lamp is first lighted. It has been desired to prevent the filament to become brittle. In order to find the desirable process, effects of the dopant added to tungsten oxide on tungsten powder and the washing treatment of doped or undoped tungsten powder were investigated in the present study.This study revealed the following facts. (1) Dopant rich layers were deposited on the surfaces of tungsten perticles produced through the reduction process of doped tungsten oxide by hydrogen. (2) These dopant rich layers played a role as adhesive and joined primary particles into coalescences. (3) The washing treatment by dilute hydrofluoric acid removed these dopant rich layers, and therefore broke the coalescences into smaller particles. (4) This washing treatment by hydrofluoric acid increased the apparent densitys of both of green compact and sintered body, and increased the ductility of recrystallized filament.Furthermore, the effects of the doping and the washing treatment on the ductility of recrystallized filament were discussed.

Aluminum Metaphosphate as a Hydrofluoric Acid Resistant Raman Cell Material

Abstract: It is sometimes desireable to study the Raman spectra of materials dissolved in aqueous hydrofluoric acid or in solutions which produce hydrogen fluoride during the course of chemical reactions. The hydrolysis of complex fluoride anions1 is one example. Generally, Raman cells of quartz or of borosilicate glass are available but tend to be rapidly etched by HF solutions with the result that the quality of spectra tend to deteriorate as well. On the other hand, plastic cells, resistant to hydrofluoric acid, can be used provided one is willing to accept the presence of plastic Raman lines which accompany and often overlap Raman lines of interest. This is a useful expedient at best. Another material that is sometimes used as a cell material, single crystal sapphire, suffers on the basis of high cost. Part of the cost arises from the necessity of aligning one of the crystallographic axis with the axis of the cell. Such a cell is ideal for high temperature experiments, however.

Hydrofluoric acid production studies: An investigation into the kinetics of reaction between fluorspar and sulfuric acid.

Abstract: The reaction between flotated fluorspar and concentrated sulfuric acid was investigated in a batch and a continuous reactor system. Conversion-time data were obtained with the batch reactor in the range of 25 0 350°F» Two series of runs were conducted in the continuous reactor. The first,varying temperature (300 450°F) and 4-1 the acid:spar ratio (0.95 ~ 1*05) and the second, a 2 fractional factorial design of experiments, varying temperature (370 and 450°F), mixing speed (15-8 and 25 r.p.m.), calcium carbonate content of the fluorspar (3-5 and 7.14 % by wt.).and the fineness of the fluorspar (2 levels). By means of statistical analysis of the data, it was shown that three rate models provide a satisfactory fit. The results indicated that the reaction is diffusion controlled (activation energy 16,000 Btu/lb.mole), and that the reactivity of the spar is appreciably enhanced by an increase in the calcium carbonate content. No appreciable change in the reactivity was detected with a change in the fluorspar fineness. The mixing speed seems to enhance the reaction at 25 r.p.m. levels .only when the calcium carbonate of the fluorspar is 3*5 % by wt.