Showing papers on "Hydrofluoric acid published in 2013"

Exceptional Photocatalytic Activity of 001-Facet-Exposed TiO2 Mainly Depending on Enhanced Adsorbed Oxygen by Residual Hydrogen Fluoride

Abstract: Is it true that the exceptional photocatalytic activity of 001-facet-exposed TiO2 is attributed to its high-energy surfaces? In this work, nanocrystalline anatase TiO2 with different percentages of the exposed (001) facet has been controllably synthesized with a hydrothermal process using hydrofluoric acid as a morphology-directing agent. It is shown that the percentage of (001)-facet exposure is tuned from 6 to 73% by increasing the amount of used hydrofluoric acid, and meanwhile the amount of residual fluoride in the as-prepared TiO2 is gradually increased. As the percentage of (001) facet is increased, the corresponding TiO2 gradually exhibits much high photocatalytic activity for degrading gas-phase acetaldehyde and liquid-phase phenol. It was unexpected that the photocatalytic activity would obviously decrease when the residual fluoride was washed off with NaOH solution. By comparing F-free 001-facet-exposed TiO2 with the F-residual one, it is concluded that the exceptional photocatalytic activity of...

Phosphorus and Boron Codoped Colloidal Silicon Nanocrystals with Inorganic Atomic Ligands

Abstract: The surface structure of P and B codoped colloidal Si-NCs are studied by photoluminescence (PL) in hydrofluoric acid (HF) solution and X-ray photoelectron spectroscopy (XPS). We find that codoped Si-NCs are much more stable in HF solution than undoped, P-doped, and B-doped Si-NCs. The PL study combined with XPS results reveal that a high B concentration layer is formed on the surface of codoped Si-NCs and the layer acts as a kind of inorganic atomic ligands for Si-NCs. The high B concentration layer makes Si-NCs hydrophilic and dispersible in polar liquids. Furthermore, the layer effectively protects Si-NCs from oxidation in solution and in air.

Shear bond strength of resin cement to an acid etched and a laser irradiated ceramic surface.

Abstract: PURPOSE To evaluate the effects of hydrofluoric acid etching and Er,Cr:YSGG laser irradiation on the shear bond strength of resin cement to lithium disilicate ceramic.

Anatase TiO2 microspheres with reactive {001} facets for improved photocatalytic activity

Abstract: Anatase TiO2 microspheres with a high percentage (>90%) of exposed high-reactivity {001} facets were synthesized using hydrofluoric acid generated in situ through hydrolysis of titanium tetrafluoride (TiF4) as a capping and stabilizing agent without introducing any additional hydrofluoric acid under hydrothermal conditions. The as-prepared TiO2 microspheres show excellent photocatalytic activity in the degradation of toxic organic contaminants as well as production of hydrogen in water under UV light irradiation.

Method for manufacturing semiconductor device

Abstract: The invention discloses a method for manufacturing a semiconductor device. Layers on the two sides of a micropattern window formed on a patterned semiconductor substrate are etched. The method comprises the following steps of: (1) performing dry etching to remove a photoresist layer; (2) performing wet etching for the first time, namely cleaning for 10 to 15 seconds by using hydrofluoric acid, and cleaning for more than 10 minutes by using sulfuric acid and hydrogen peroxide; and (3) performing wet etching for the second time, namely cleaning for 70 to 150 seconds by using the hydrofluoric acid, and cleaning for more than 10 minutes by using phosphoric acid. Through staged two-time wet etching, particularly the layers are cleaned by using the hydrofluoric acid for a long time during the second-time wet etching, so that the photoresist layer and silicon dioxide in an anti-reflective coating are completely removed, the peeling defect of the silicon dioxide in the manufacturing process is overcome, and the quality of the semiconductor device is ensured.

Comparison of Conventional and HF-Free-Synthesized MIL-101 for CO2 Adsorption Separation and Their Water Stabilities

Abstract: The preparation of MIL-101 was simplified to avoid the use of hazardous hydrofluoric acid (HF). The potential application of MIL-101, prepared by both this new method and the conventional approach,...

Application of microwave digestion and ICP-MS to simultaneous analysis of major and trace elements in aerosol samples collected on quartz filters

Abstract: A microwave digestion method in a closed vessel was developed for the simultaneous determination of trace and major elements, with the highest possible recoveries, in atmospheric aerosols using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). This method was developed to quantify the concentration of Na, Mg, Al, P, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Cd, Sb, Cs, Ba, La, Ce and Pb present in quartz filters containing particulate matter (PM10). The performance of the procedure was evaluated by analysis of the standard reference material NIST 1633b and CTA-FFA-1. Different combinations of nitric acid (HNO3), hydrogen peroxide (H2O2), hydrofluoric acid (HF) and hydrochloric acid (HCl) were tested to improve the recovery factors for the studied elements. The addition of a large amount (3 mL) of HF was required to fully dissolve the quartz filters. This fact made difficult the obtention of high recoveries for alkali (Rb, Cs), alkaline earth (Mg, Ca, Ba), and rare earth (La, Ce) elements, which showed the lowest recoveries. In this study three different digestion methods were assessed using a closed evaporation system, the addition of boric acid and a mixture of both procedures to minimize the effects of residual fluoride.

Realization of single-termination SrTiO3 (100) surfaces by a microwave-induced hydrothermal process

Abstract: A microwave-induced hydrothermal etching of SrTiO3 (100) single crystal surfaces in deionized water and subsequent annealing in oxygen atmosphere results in single-terminated and atomically flat terraces for pure and niobium-doped substrates as confirmed through one unit-cell step height and uniform phase by atomic force microscopy. This process that requires 3 min of moderate microwave radiation completely avoids the use of hydrofluoric acid (HF) and related point defects due to fluorine in the crystal surface. The advantages of a safe, inexpensive, and environmentally neutral process hold promise to replace the existing standard protocol for substrate preparation based on buffered HF.

UF4, ThF4 Solubility in LiF–NaF–KF Melt

Abstract: The results of measurements of the solubility of UF 4 and ThF 4 in the eutectic 46.5LiF‐11.5NaF‐42KF are presented. Isothermal saturation of the salt melt by the experimental compounds is used. The UF 4 and ThF 4 solubility in the experimental salt system is experimentally shown to be high (45 and 41 mol. %, respectively, at 700°C) and temperature-dependent in the interval 550‐700°C. The available data on the solubility of heavy-element fluorides in LiF‐NaF‐KF are limited and the systematic errors are not known. A few theoretical estimates, obtained using a thermodynamic approach, exist [1, 2]. The measured values of the solubility in salt with the composition 45LiF‐12NaF‐43KF at 600, 650, and 700°C are 4.7, 9.7, and 11.7 for UF 4 and 4.5, 6.8, and 7.6 for ThF 4 [3]. The present work is devoted to measuring the solubility of UF 4 and ThF 4 in a salt system with eutectic composition 46.5LiF‐11.5NaF‐42KF (T melt = 454°C) in the interval 550‐700°C by a method of isothermal saturation of melt, differing somewhat from the one used in [3]. Experiment. A schematic diagram of the setup for measuring solubility is presented in [4]. The initial reagents were factory products of depleted uranium tetrafluoride and thorium nitrate. Thorium nitrate was dissolved in distilled water followed by precipitation of hydrated ThF 4 by concentrated hydrofluoric acid. The precipitate obtained was separated from the solution, washed with a dilute 0.001 M solution of hydrofluoric acid and dried over a long period of time to a powder. Hydrated thorium tetrafluoride ThF 4 ·H 2 O was dewatered in a special hermetic cell in an argon (high purity grade 5.5) stream in a nickel boat, adding ammonium bifluoride NH 4 F·HF to the cell and boat. ThF 4 ·H 2 O was processed repeatedly at 350°C until phase-pure anhydrous thorium tetrafluoride was obtained. Pellets were produced from uranium and thorium tetrafluoride using a 5-mm in diameter die-casting mold under pressure 200 MPa. The quality of the preparations was monitored by x-rays in a RKU-114M Debye‐Scherrer chamber with a copper anti-cathode and nickel filter as well as a DRON-3N x-ray diffractometer. The interpretation of the x-ray diffraction patterns and calculations of the functions of the scattering angles were performed in the PIKAR laboratory measuring complex taking account of the main systematic errors (absorption and uncertainty of the film radius) [5, 6]. The intensity of the reflections was evaluated visually according to the blackening marks on a 100 unit scale with step 2 1/4 . The JCPDS diffraction data library was used to identify the phase composition of the products [7]. The eutectic was prepared using the initial reagents lithium, sodium and potassium fluorides manufactured by the Sigma-Aldrich Company (USA). Weighed portions of anhydrous Li, Na, and K fluorides were placed into a box with a dry

Evaluation of Organic-Hydrofluoric Acid Mixtures for Sandstone Acidizing

Abstract: Mud acid, which is a mixture of hydrochloric (HCl) and hydrofluoric (HF) acids, is typically used to stimulate sandstone formations. The success rate of mud acid is limited mainly because of its high spending rate, high corrosion rate, and incompatibility with HCl sensitive minerals; i.e., illite. Organic (acetic, formic and citric) HF acid mixtures, in comparison, have a retarded nature and a low corrosion rate, and are compatible with sensitive sandstone formations; therefore, they can be used as an effective stimulation fluid alternative to regular mud acid. In this study, dissolution tests of kaolinite, illite or chlorite in acetic, formic and citric with 3 wt% HF acid was conducted. A coreflood was conducted to investigate the ability of organic acids, when combined with HF acid, to remove carbonaceous and siliceous minerals from Berea sandstone plugs at 250 °F. The core effluent samples were analyzed using inductively coupled plasma (ICP). The core plugs were analyzed using the X-ray diffraction (XRD). All of the tested organic acids were effective in dissolving calcium during the coreflood preflush stage without any indication of precipitation; however, only citric acid extracted aluminum during the preflush, while formic and acetic acids were not effective in leaching aluminum. Additionally, low amounts of aluminum were detected in the effluent of acetic-HF during the main flush and severe damage to the core plug was noticed. Although formic-HF acid extracted a significant amount of calcium and aluminum, there was no change in permeability before or after the treatment. Citric-HF acid dissolved a significant amount of calcium and aluminum, and an apparent increase in permeability was subsequently observed. In addition, a higher permeability ratio was obtained with low HF acid concentrations. This work provides new insights into the applications and potential limitations of organic-HF acids.

Facile Synthesis of 2-Fluoro-1,3-dicarbonyl Compounds with Aqueous Hydrofluoric Acid Mediated by Iodosylarenes

Abstract: Direct fluorination of 1,3-dicarbonyl compounds including 1,3-diketones, 3-oxo esters, and 3-oxoamides was conducted using aqueous hydrofluoric acid with the aid of iodosylarenes, giving the corresponding 2-fluorinated products in good to high yields. Among the used iodosylarenes, o-iodosyltoluene was found to be the most effective, and the yield of 2-fluorinated products was improved.

Selective etching of copper and copper-barrier materials by an aqueous base solution with fluoride addition

Abstract: Wet-etch solutions for conductive metals (e.g., copper) and metal nitrides (e.g., tantalum nitride) can be tuned to differentially etch the conductive metals and metal nitrides while having very little effect on nearby oxides (e.g., silicon dioxide hard mask materials), and etching refractory metals (e.g. tantalum) at an intermediate rate. The solutions are aqueous base solutions (e.g., ammonia-peroxide mixture or TMAH-peroxide mixture) with just enough hydrofluoric acid (HF) added to make the solution's pH about 8-10. Applications include metallization of sub-micron logic structures.

Method of manufacturing silicon carbide semiconductor device

Abstract: A method of manufacturing a silicon carbide semiconductor device includes forming a first silicon carbide layer of a first conductivity type on a front surface of a silicon carbide semiconductor substrate. A thermal oxidation film is formed on a surface of a base body including the first silicon carbide layer. The thermal oxidation film is subsequently removed using a solution containing hydrofluoric acid. The base body is washed with a mixture of ammonia water and a hydrogen peroxide solution, a mixture of hydrochloric acid and a hydrogen peroxide solution, and a dilute hydrofluoric acid. The base body is held at temperature of 700 degrees C. to 1700 degrees C., and an insulating film is deposited on the base body.

Stability of carbon nanowalls against chemical attack with acid solutions

Abstract: In this paper we report on the stability of CNW layers, synthesized by a radiofrequency plasma jet, against the chemical attack with different acid solutions (sulfuric acid, nitric acid, hydrochloric acid, and hydrofluoric acid). We present the changes of the morphology and structure of the CNW caused by the post-growth chemical treatments. We demonstrate that self-sustaining and transferable CNW layers can be obtained, by chemically dissolving the substrates, while the initial characteristics of the material are well preserved.

Polyaniline synthesis using hydrofluoric acid as doping agent: Comparative evaluation with polyaniline doped with sulfuric acid

Abstract: This work focuses on the comparison between the morphological, chemical, and electrical properties of polyaniline doped with fluoridric and polyaniline, and doped with sulfuric acid. The FT-IR, XRD, and SEM/EDS results indicate that the use of hydrofluoric acid as doping agent does not provide meaningful changes in the crystalline and morphological structure of polyaniline. Although, the inclusion of F− type counter-ions from the doping process with HF provide more compact, denser, and with higher electrical conductivity polymeric matrices. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2013

Anti-scaling multi-hydrogen retarded acid for highly argillaceous sandstone reservoir

Abstract: The invention provides an anti-scaling multi-hydrogen retarded acid for a highly argillaceous sandstone reservoir. The retarded acid is prepared from the following raw materials by weight: 3 to 5 parts of hydrochloric acid, 3 to 5 parts of amino trimethylene phosphonic acid, 3.5 to 6 parts of ammonium bifluoride, 1 to 2.2 parts of a corrosion inhibitor, 0.5 to 1 part of a ferric ion stabilizing agent, 0.2 to 1 part of a clay stabilizing agent, 0.3 to 1 part of a de-emulsifier, 0.2 to 1 part of a mutual solvent and 78 to 87 parts of water. The anti-scaling multi-hydrogen retarded acid is used in the petroleum industry to control a reaction speed of hydrofluoric acid and clay so as to realize deep acidization of the highly argillaceous reservoir.

Method for preparing silicon-based nano-scale ordered porous silicon

Abstract: The invention discloses a method for preparing silicon-based nano-scale ordered porous silicon, comprising the following steps of: (1) ultrasonically washing an n-shaped one-side polished monocrystalline silicon piece in an acetone solvent, absolute ethyl alcohol and de-ionized water sequentially; and (2) preparing a porous silicon layer on the polished surface of the silicon piece by a double-tank electrochemical corrosion method, taking the aqueous solution of hydrofluoric acid having the mass fraction of 5-9% as corrosive liquid, and applying corrosion current, wherein the density of the corrosion current is 75-155 mA/cm , and the corrosion time is 5-30 min; and the process is performed at the room temperature without illumination. The method disclosed by the invention is simple, quick, effective and practicable, and high in operability; and the bore diameter of the obtained porous silicon is at hundred-nanometer scale, and has the characteristics of high porosity and highly ordered pore canals. The method is capable of achieving the purpose of the silicon-based nano-scale ordered porous silicon by controlling the concentration of the hydrofluoric acid, the corrosion current density and the corrosion time; and the silicon-based nano-scale ordered porous silicon is an ideal material for preparing biological and chemical sensor elements.

Interaction between a transition-metal fluoride and a transition-metal hydride: water-mediated hydrofluoric acid evolution following fluoride solvation.

Abstract: The reaction between the nickel(II) PCP pincer fluoride complex ((tBu)PCP)Ni(F) [(tBu)PCP = 2,6-C6H3(CH2P(t)Bu2)2] and the tungsten(II) carbonyl hydride CpW(H)(CO)3 (Cp = η(5)-C5H5(-)) leads to hydrofluoric acid evolution and formation of the bimetallic isocarbonylic species [CpW(CO)2(μ-κ,C:κ,O-CO)···Ni((tBu)PCP)]. The process has been monitored through multinuclear ((19)F, (31)P{(1)H}, (1)H) variable-temperature NMR spectroscopy, collecting (19)F T1 data values for a fluoride ligand bound to a transition metal. The extremely short relaxation time (minimum value of 13 ms at 193 K) is ascribed to the large chemical shift anisotropy of the Ni-F bond (688 ppm). The in-depth NMR analysis has revealed that the fluoride-hydride interaction is not direct but water-mediated, at odds with what was previously observed for the "hydride-hydride" case ((tBu)PCP)Ni(H)/CpW(H)(CO)3. Kinetic measurements have unveiled that the first step of the overall mechanism is thought to be solvation of the fluoride ligand (as a result of Ni-F···H2O hydrogen bonding), while further reaction of the solvated fluoride with CpW(H)(CO)3 is extremely slow and competes with the side reaction of fluoride replacement by a water molecule on the nickel center to form the [((tBu)PCP)Ni(H2O)](+) aquo species. Finally, density functional theory analysis of the solvation process through a discrete + continuum model has been accomplished, at the M06//6-31+G(d,p) level of theory, to support the mechanistic hypothesis.

Stainless steel passivation water solution and preparation method thereof

Abstract: The invention provides a stainless steel passivation water solution. The solution comprises the components of: molybdate, sulfamic acid, organic phosphoric acid, sodium citrate, benzotriazole, thiosemicarbazide, and a PH adjusting agent. The invention also provides a preparation method of the stainless steel passivation water solution. The stainless steel passivation water solution provided by the invention does not contain harmful components of nitric acid, hydrofluoric acid, and potassium dichromate. The solution is an environment-friendly novel alkaline passivation solution. A stainless steel passivation layer processed by the passivation of the passivation solution is compact and has good corrosion resistance.

Etching method for OGS (One Glass Solution) glass subjected to secondary chemical enhancement

Abstract: The invention relates to an etching method for OGS (One Glass Solution) glass subjected to secondary chemical enhancement, and the etching method comprises the following steps of: etching an OGS glass sheet in an etching bath for 6-15 minute, wherein an acid-resisting film is respectively adhered to the forward surface and back surface of the OGS glass sheet, the etching bath is filled with etching acid liquor, and the temperature of the etching bath is 30-35 DEG C, the etching acid liquor is prepared by mixing a hydrofluoric acid solution, auxiliary acid liquor and water at a volume ratio of (4-5):(1.5-2.5):(3-4), the auxiliary acid liquor is a mixture of one or more of a salpeter solution, a sulfuric acid solution or a hydrochloric acid solution, the mass concentration of the hydrofluoric acid solution is 40%, the mass concentration of the salpeter solution is 68%, the mass concentration of the sulfuric acid solution is 86%, and the mass concentration of the hydrochloric acid solution is 31%; bubbling the etching acid liquor in an etching process, wherein the bubbling amount is 50-150 l/min. According to the invention, the occurrence of irregular edge and sawteeth phenomena caused by the poor etching of OGS glass can be avoided, the glass strength is improved, and the problem of bad appearance caused by edge BM falling off and corrosion of an ITO circuit is avoided; micro cracks at the edges of glass can be effectively eliminated, so that the mechanical compressive resistance amplitude can be enhanced, and the strength and yield of the OGS glass can be significantly enhanced.

Low-Acid Extraction of Tantalum from a Tantalum-Niobium Pulp by MIBK

Abstract: The technological parameters and the mechanism of low-acid pulp extraction of tantalum were investigated. The results show that hydrofluoric acid concentration, sulfuric acid concentration, organic to pulp phase ratio, the concentration of tantalum and niobium, contact time and temperature have a significant effect; optimum process operating parameters were established as follows: hydrofluoric acid concentration 1.6 mol/L, sulfuric acid concentration 0.6 mol/L, organic to pulp phase ratio 3:1, tantalum concentration 26.61 g/L, niobium concentration 11.64 g/L, contact time 5min and room temperature. Under these experimental conditions, tantalum extraction can reach more than 98% and the separation factors of Ta/Nb, Ta/Fe and Ta/Sn were maximal. According to slope analysis, the equimolar series method and the saturation capacity method, the extraction product was identified as 3MIBK center dot H2TaF7.

구미 불산 누출사고 지점 주변 식물의 불소화합물 농도 분포 및 공기 중 불화수소 농도 추정에 관한 연구

Abstract: Objectives: The goal of this study is to identify the distribution of the foliar fluorine content of vegetation surrounding the area where hydrofluoric acid was accidently released in Gumi, Gyeongsangbuk-do on September 27, 2012. In addition, it also aims to estimate the concentration of hydrogen fluoride in the air on the day of the accident. Methods: Samples of plant leaves were collected on October 7, 2012 within 1 km from the site where the accident occurred. These samples were analyzed for soluble fluorine ion with an ion selective electrode. The ambient concentration of hydrogen fluoride was calculated using the fluoride content in the plant via the doserate equation (ΔF=KCT). Results: The arithmetic and geometric means of the concentrations were 2158.2 and 1183.7mg F kg-1 for leaves and, 2.4 and 1.1 ppm HF for the air, respectively. The highest concentration of hydrogen fluoride in the air was 14.7 ppm, which is higher than the maximum concentration reported by the government (1 ppm) and the exposure limit (ceiling, 3 ppm). The concentrations of both fluorine and hydrogen fluoride decreased with increasing distance from the accident site and showed a significant decrease outside of a 500m radius from the site (p Conclusions: The area around the accident site was highly polluted with hydrogen fluoride according to the results of this study. Considering the persistency of hydrogen fluoride in the environment, long-term monitoring and environmental impact assessment should be pursued.

Unexpectedly High Etching Rate of Highly Doped n-Type Crystalline Silicon in Hydrofluoric Acid

Abstract: The high selectivity in etching of dielectric films over crystalline silicon (c-Si) by hydrofluoric acid (HF) is routinely exploited in the fabrication of various silicon based devices such as microelectromechanical systems (MEMS) and silicon solar cells. In this paper it is shown that the high selectivity does not apply to highly doped n-type c-Si. We confirm experimentally that the etch rate of highly doped n-type c-Si is about 0.8 nm/minute in diluted HF, which is more than 10 times higher than previous results reported in the literature and measured at lower carrier concentrations. We propose that a combination of factors is contributing to the observed fast etching rate of heavily doped n-type c-Si. The proper understanding and exploitation of the etching mechanism of n + c-Si by HF can be very beneficial for the fabrication of silicon MEMS and solar cell devices. © 2013 The Electrochemical Society. [DOI: 10.1149/2.026309jss] All rights reserved.