The fluorine-based chemical method shows great potential in leaching lithium(Li) from lepidolite. Leaching kinetics of Li in a mixture of sulfuric acid and hydrofluoric acid, which is a typical lixivant for the fluori...The fluorine-based chemical method shows great potential in leaching lithium(Li) from lepidolite. Leaching kinetics of Li in a mixture of sulfuric acid and hydrofluoric acid, which is a typical lixivant for the fluorine-based chemical method, was carried out under crucial factors such as different HF/ore ratios(1:1-3:1 g/mL) and leaching temperatures(50-85℃). The kinetics data fit well with the developed shrinking-core model, indicating that the leaching rate of Li was controlled by the chemical reaction and inner diffusion at the beginning of leaching(0-30 min) as a calculated apparent activation energy(Ea) of 20.62 kJ/mol. The inner diffusion became the rate-limiting step as the leaching continues(60-180 min). Moreover, effects of HF/ore ratio and leaching temperature on selective leaching behavior of Li, Al and Si were discussed. 90% of fluorine mainly existed as HF/F-in leaching solution, which can provide theoretical guidance for further removal or recovery of F.展开更多
Leaching kinetics of acid-soluble Cr（VI） in chromite ore processing residue （COPR） using hydrofluoric （HF） acid solution as a leaching agent was investigated for potential remediation of COPR with industrial was...Leaching kinetics of acid-soluble Cr（VI） in chromite ore processing residue （COPR） using hydrofluoric （HF） acid solution as a leaching agent was investigated for potential remediation of COPR with industrial waste water containing HF. The results show that HF can effectively destabilize the Cr（VI）-bearing minerals, resulting in the mobilization of Cr（VI） from COPR into the leachate. Particle size significantly influences the leaching of acid-soluble Cr（VI） from COPR, followed by leaching time, whereas the effects of HF concentration and leaching temperature are slight and the influence of stirring rate is negligible. The leaching process of acid-soluble Cr（VI） from COPR is controlled by the diffusion through the product layer. The apparent activation energy is 8.696 kJ/mol and the reaction orders with respect to HF concentration and particle size is 0.493 8 and -2.013 3, respectively.展开更多
AIM: To review the current evidence of the treatment of hydrofluoric acid(HF) exposure to the human cornea.METHODS: A comprehensive manual search of the literature was conducted through the Ovid interface to assess th...AIM: To review the current evidence of the treatment of hydrofluoric acid(HF) exposure to the human cornea.METHODS: A comprehensive manual search of the literature was conducted through the Ovid interface to assess the mechanism and efficacy of each irrigator through a variety of clinical cases and experimental studies.· RESULTS: Ocular exposure to HF is extremely damaging to the eye and swift recognition and decontamination with an appropriate agent forms the basis of treatment. Although there are various decontamination solutions that have efficacy against the corrosive action of HF, irrigation with Hexafluorine proved to be the most safe and effective treatment for the eye.CONCLUSION: In conclusion emergency departments could benefit from the availability of Hexafluorine for the treatment of HF ocular burns in patients.展开更多
BACKGROUND Hydrofluoric acid(HF)is one of the most common causes of chemical burns.HF burns can cause wounds that deepen and progress aggressively.As a result,HF burns are often severe even if they involve a small are...BACKGROUND Hydrofluoric acid(HF)is one of the most common causes of chemical burns.HF burns can cause wounds that deepen and progress aggressively.As a result,HF burns are often severe even if they involve a small area of the skin.Published cases of HF burns have mostly reported small HF burn areas.Few cases of HF inhalation injury have been reported to date.CASE SUMMARY A 24-year-old man suffered from extensive hydrofluoric acid burns covering 60%of the total body surface area(TBSA),including deep second degree burns on 47%and third degree burns on 13%of the TBSA,after he fell into a pickling pool containing 15%HF.Comprehensive treatments were carried out after the patient was admitted.Ventricular fibrillation occurred 9 times within the first 2 h,and the lowest serum Ca2+concentration was 0.192 mmol/L.A dose of calcium gluconate(37 g)was intravenously supplied during the first 24 h,and the total amount of calcium gluconate supplementation was 343 g.Extracorporeal membrane oxygenation(ECMO)was applied for 8 d to handle the acute respiratory distress syndrome(ARDS)induced by the HF inhalation injury.The patient was discharged after 99 d of comprehensive treatment,including skin grafting.CONCLUSION Extensive HF burns combined with an inhalation injury led to a potentially fatal electrolyte imbalance and ARDS.Adequate and timely calcium supplementation and ECMO application were the keys to successful treatment of the patient.展开更多
The results of XPS measurements of commercially pure titanium cp-Ti) before and after chemical treatment are presented. We have measured XPS spectra of core levels (Ti 2p, O 1s, C 1s, F 1s) and valence bands of coarse...The results of XPS measurements of commercially pure titanium cp-Ti) before and after chemical treatment are presented. We have measured XPS spectra of core levels (Ti 2p, O 1s, C 1s, F 1s) and valence bands of coarse-grained cp-Ti before and after standard acid treatment accepted in dentistry (in 1% HF and 40% HF for 1 min). It is found, that acid treatment of cp-Ti reduces the content of hydrocarbons increasing the surface energy and bio-compatibility of Ti-implants. On the other hand, it is fixed that oxygen concentration on the surface of the acid treated cp-Ti is much higher than for the untreated sample, because the acid treatment removes the contaminated surface layers, increases their reactivity, provides a better passivation and formation of thick protecting TiO2 layer.展开更多
The development of a nucleophilic fluorination protocol using hydrofluoric acid as the fluoride source represents a long-sought goal in the field of organofluorine chemistry.We report herein the realization of such a ...The development of a nucleophilic fluorination protocol using hydrofluoric acid as the fluoride source represents a long-sought goal in the field of organofluorine chemistry.We report herein the realization of such a reaction that employed alkyl-substituted sulfonium ylides as the substrates.The key to the success of the protocol was attributed to two factors:First,as a Brϕnsted base,the ylide was able to be protonated by HFaq,thus serving as a phase-transfer shuttle generated in situ to bring F−from aqueous phase to the organic phase promoting desolvation of fluoride ion.Second,after protonation,a sulfonium salt,a good leaving group,was generated and subsequent attacked by the fluoride to afford the alkyl fluoride.Mechanistic investigation indicates that the reaction occurs via an SN1 pathway.Because of the nature of the cationic intermediate in the reaction,two attractive rearrangement-fluorination approaches including 1,2-aryl migration fluorination and ring-expansion fluorination were disclosed.展开更多
This study investigates microstructure, hydrogen diffusion properties, and stress corrosion cracking(SCC) behavior of Q345R steel subject to pre-applied strains of 1 %, 3 %, and 5 %. The relationship between microstru...This study investigates microstructure, hydrogen diffusion properties, and stress corrosion cracking(SCC) behavior of Q345R steel subject to pre-applied strains of 1 %, 3 %, and 5 %. The relationship between microstructure and SCC susceptibility in hydrofluoric acid(HF) vapor is examined. It is found that pre-strain cannot change the microstructure of Q345R steel but increases dislocation density. The increasing SCC sensitivity of Q345R steel in HF vapor is associated with the dislocation density induced by pre-strain. With increasing pre-strain, dislocation density and reversible hydrogen trap increase, and interaction between hydrogen and dislocation accelerates hydrogen-induced SCC. In addition, irreversible hydrogen traps caused by high pre-strain can severely aggravate hydrogen-induced SCC, resulting in high SCC vulnerability.展开更多
A transformative beryllium metallurgy theory and method was proposed based on the low-temperature dissociation of hydrofluoric acid and purification by exploiting the large difference of fluoride solubility.Hydrofluor...A transformative beryllium metallurgy theory and method was proposed based on the low-temperature dissociation of hydrofluoric acid and purification by exploiting the large difference of fluoride solubility.Hydrofluoric acid can quickly dissociate berylum ore powder directly at low or room temperature with more than 99%dissociation rate.The solubility of AlF_(3),FeF_(3) CrF_(3) and MgF_(2),is low.Coupled with common ion effect,99.9%-purity beryllium products can be prepared without chemical purification.For high-purity beryllium products of grade 4N or higher,they can be prepared through the superior property that the pH intervals of iron,chromium,and other hydroxide precipitates are distinctly different from those corresponding to Be(OH)_(2),precipitates.This new method can be used to prepare most of the beryllium products that are prepared by modern beryllium metallurgy.展开更多
Although hydrofluoric acid(HF)surface treatment is known to enhance the joining of metals with polymers,there is limited information on its effect on the joining of AZ31 alloy and carbon-fiber-reinforced plastics(CFRP...Although hydrofluoric acid(HF)surface treatment is known to enhance the joining of metals with polymers,there is limited information on its effect on the joining of AZ31 alloy and carbon-fiber-reinforced plastics(CFRPs)through laser-assisted metal and plastic direct joining(LAMP).This study uses the LAMP technique to produce AZ31-CFRP joints.The joining process involves as-received AZ31,HFpretreated AZ31,and thermally oxidized HF-pretreated AZ31 alloy sheets.Furthermore,the bonding strength of joints prepared with thermally oxidized AZ31 alloy sheets is examined to ascertain the combined effect of HF treatment and thermal oxidation on bonding strength.The microstructures,surface chemical interactions,and mechanical performances of joints are investigated under tensile shear loading.Various factors,such as bubble formation,CFRP resin decomposition,and mechanical interlocking considerably affect joint strength.Additionally,surface chemical interactions between the active species on metal parts and the polar amide along with carbonyl groups of polymer play a significant role in improving joint strength.Joints prepared with surface-pretreated AZ31 alloy sheets show significant improvements in bonding strength.展开更多
An enhanced leaching of Li fromα-spodumene was carried out using a mixture of hydrofluoric and sulfuric acid(HF/H_(2)SO_(4))as the medium.Based on the optimized leaching conditions,the leaching kinetics of Li was inv...An enhanced leaching of Li fromα-spodumene was carried out using a mixture of hydrofluoric and sulfuric acid(HF/H_(2)SO_(4))as the medium.Based on the optimized leaching conditions,the leaching kinetics of Li was investigated in an ore/HF/H_(2)SO_(4) ratio of 1:3:2 g:mL:mL with leaching temperature ranging from 50 to 100°C.The results indicate that the leaching kinetics of Li fitted well with a model based on the shrinking core model.In addition,the leaching rate of Li was controlled by chemical reactions and diffusion through the product layers.The apparent activation energy Ea was calculated to be 32.68 kJ/mol.Solid films were formed because of the generation of insoluble products such as cryolithionite(Na_(3)Li_(2)Al2F _(12) ),cryolite(Na_(3)AlF_(6)),calcium fluoride(CaF_(2)),potassium cryolite(K_(2)AlF_(5)),aluminum fluoride(AlF_(3)),and fluorosilicates(Na_(2)SiF_(6 )or KNaSiF_(6)).Furthermore,the effects of the ore/HF ratio and leaching temperature on the leaching behavior of Li,Al and Si were investigated.The results indicate that the ore/HF ratio and leaching temperature could clearly affect the distribution of HF molecules on the leaching of Li,Al and Si,which are important for the selective leaching of Li over Al and Si with this fluorine-based chemical method.展开更多
Coal is the world＇s most abundant energy source because of its abundance and relatively low cost. Due to the scarcity in the supply of high-grade coal, it is necessary to use low-.grade coal for fulfilling energy dem...Coal is the world＇s most abundant energy source because of its abundance and relatively low cost. Due to the scarcity in the supply of high-grade coal, it is necessary to use low-.grade coal for fulfilling energy demands of modern civilization. However, due to ItS high ash and moisture content, low-grade coal exerts the substantial impact on their consumption like pyrolysis, liquefaction, gasification and combus- tion process. The present research aimed to develop the efficient technique for the production of clean coal by optimizing the operating parameters with the help of response surface methodology. The effect of three independent variables such as hydrofluoric acid （HF） concentration （10-20% by vo!ume ）,. temper- ature （60-100 ~C）, and time （90-180 min）, for ash reduction from the low-grade coal was Investigated.. A quadratic model was proposed to correlate the independent variables for maximum ash reduction at the optimum process condition by using central composite design （CC.D）method. The study reveals that HF concentration was the most effective parameter for ash reduction in comparison with time and temper- ature. It may be due to the higher F-statistics value for HF concentration, which effects to large extent of ash reduction. The characterization of coal was evaluated by Fourier transform infrared spectroscopy （FTIR） analysis and Field-emission scanning electron microscopy with energy-dispersive X-ray （FESEM- EDX） analysis for confirmation of the ash reduction.展开更多
Fiber Bragg grating Fabry-Perot (FBG F-P) cavity is used as the sensing model to measure the refractive index of the liquid solution. The cladding of the fiber, which is used as the F-P cavity, is etched by HF solutio...Fiber Bragg grating Fabry-Perot (FBG F-P) cavity is used as the sensing model to measure the refractive index of the liquid solution. The cladding of the fiber, which is used as the F-P cavity, is etched by HF solution to enhance the sensitivity to the external refractive index. The experimental results show that with the concentration change of the external solution, the effective refractive index of etched fiber will change, thus the spectra of FBG F-P cavity will appear a spilt point. The relationship be...展开更多
In order to extract gallium from a high-silica-content flue dust generated in corundum production,a mixed acid solution of H2SO4 and HF was used for leaching,and test parameters of the leaching process were optimized....In order to extract gallium from a high-silica-content flue dust generated in corundum production,a mixed acid solution of H2SO4 and HF was used for leaching,and test parameters of the leaching process were optimized.Experimental results show that the leaching rate of gallium was only 38%when H2SO4 was used as leaching agent.Composition analysis results of micro areas in this corundum flue dust indicate that the content of gallium in silica-enriched phases was high;this portion of gallium was insoluble in H2SO4 solution.The leaching rate of gallium increased significantly with addition of HF due to corrosion of silica.Effects of reaction time,temperature,and concentrations of HF and H2SO4 on leaching rates of gallium were investigated.The leaching rate of gallium reached 91%when this corundum flue dust was leached in a mixed acid solution of H2SO4 and HF for 4 h,at a temperature of 80°C,with a liquid-to-solid ratio of 5:1(mL/g).The optimal concentrations of H2SO4 and HF in the mixed acid solution were 1.5 and 6.4 mol/L,respectively.展开更多
The aim of this study was to determine if accelerated aging of porcelain veneering had an effect on the surface properties specific to a tetragonal-to-monoclinic transformation（TMT） of zirconia restorations. Thirty-...The aim of this study was to determine if accelerated aging of porcelain veneering had an effect on the surface properties specific to a tetragonal-to-monoclinic transformation（TMT） of zirconia restorations. Thirty-six zirconia samples were milled and sintered to simulate core fabrication followed by exposure to various combinations of surface treatments including as-received（control）,hydrofluoric acid（HF）, application of liner plus firings, application of porcelain by manual layering and pressing with firing, plus accelerated aging. The quantity of transformed tetragonal to monoclinic phases was analyzed utilized an X-ray diffractometer and one-way analysis of variance was used to analyze data. The control samples as provided from the dental laboratory after milling and sintering process had no TMT（X m5 0）. There was an effect on zirconia samples of HF application with TMT（X m5 0.8%） and liner plus HF application with TMT（X m5 8.7%）. There was an effect of aging on zirconia samples（no veneering） with significant TMT（X m5 70.25%）. Both manual and pressing techniques of porcelain applications reduced the TMT（manual, X m5 4.41%, pressing,X m5 11.57%）, although there was no statistical difference between them. It can be concluded that simulated applications of porcelain demonstrated the ability to protect zirconia from TMT after aging with no effect of a liner between different porcelain applications.The HF treatment also caused TMT.展开更多
A new method is presented to tune Bragg wavelength slightly by using hydrofluoric acid to etch fiber cladding.The spectral characteristics before and after etching and the change properties of Bragg wavelength are stu...A new method is presented to tune Bragg wavelength slightly by using hydrofluoric acid to etch fiber cladding.The spectral characteristics before and after etching and the change properties of Bragg wavelength are studied.Cladding modes are reduced during the etching process.High-order cladding modes are converted into radiation modes,and energy of cladding modes is coupled to the outside.As the cladding radius decreases,the Bragg wavelength shifts to longer direction.Experimental results show that this method can tune Bragg wavelength slightly,and the tunable range is 0.002-0.120 nm.展开更多
Abstract: In the occurrence of arc discharges, spark discharges, corona discharges and overheated faults in electrical equipment, SF 6would be decomposed to complicated byproducts, such as SO2 , H2S and HF. Analyzing ...Abstract: In the occurrence of arc discharges, spark discharges, corona discharges and overheated faults in electrical equipment, SF 6would be decomposed to complicated byproducts, such as SO2 , H2S and HF. Analyzing these byproducts is an effective method to judge the internal operation condition of electric equipment. In order to study characters of SF6byproducts at different temperature of overheated faults in the electric equipment, a series of overheated faults of electric equipment were simulated. SF6is very stable and not significantly decomposed at 200oC, 250oC and 300oC. SF6is significantly decomposed to SO2, H2S and HF at 350oC. The concentration of SO2, H2S and HF was 7.2, 1.6 and 1.9 μL/L after heating for 5 hours in environment of SF6with 3616 μL/L water, and it was increased to 23.0, 3.0 and 1.2 μL/L 3 hours later. SF6is more easily to be decomposed and decomposed more rapidly at higher temperature. The concentration of SO2, H2S and HF was 62.2, 15.6 and 3.6 μL/L after heating for 5 hours in environment of SF6with 4064 μL/L water, and it was increased to 91.4, 25.2 and 2.3 μL/L 3 hours later. SF6will be decomposed to format HF, which is strongly corrosive and whose concentration is likely to decrease when it is above a certain concentration.展开更多
Mixtures of lanthanum oxide, europium oxide, and phosphoric acid were heated with various ratios of P/(La + Eu) and Eu/(La + Eu). The obtained phosphates were estimated using XRD patterns, FT-IR spectra, and SEM image...Mixtures of lanthanum oxide, europium oxide, and phosphoric acid were heated with various ratios of P/(La + Eu) and Eu/(La + Eu). The obtained phosphates were estimated using XRD patterns, FT-IR spectra, and SEM images. The fluo-rescence spectra and resistance against hydrofluoric acid were estimated as functional properties of these phosphate materials. The condensed phosphates showed a strong peak at 615 nm and high resistance against hydrofluoric acid.展开更多
Mixtures of lanthanum oxide, europium oxide, calcium carbonate, and phosphoric acid were heated with various ratios of P/(Eu + La + Ca) and La/Ca. Europium ratio was settled at Eu/(Eu + La + Ca) = 0.03. The obtained p...Mixtures of lanthanum oxide, europium oxide, calcium carbonate, and phosphoric acid were heated with various ratios of P/(Eu + La + Ca) and La/Ca. Europium ratio was settled at Eu/(Eu + La + Ca) = 0.03. The obtained phosphates were estimated using X-ray diffraction (XRD) patterns, Fourier transform infrared spectroscopy (FT-IR) spectra, and scanning electron micrograph (SEM) images. The fluorescence spectra and resistance against hydrofluoric acid were estimated as functional properties of these phosphate materials. The mixture of lanthanum and calcium phosphates were formed from XRD patterns and IR spectra. Samples prepared in P/(Eu + La + Ca) = 2 and 3 had large particles in SEM images. The condensed phosphates showed a strong peak at 615 nm and high resistance against hydrofluoric acid.展开更多
A simple and compact refractive index sensor is demonstrated by tapering a photonic crystal fiber （PCF） in-line interferometer. The PCF is spliced between two single-mode fibers and tapered via hydrofluoric acid etc...A simple and compact refractive index sensor is demonstrated by tapering a photonic crystal fiber （PCF） in-line interferometer. The PCF is spliced between two single-mode fibers and tapered via hydrofluoric acid etching. Its sensitivity in liquid is more than an order of magnitude larger than the untapered one. By optimizing the etching process, we can fabricate more uniformly and thinly tapered PCF interferometers with higher sensitivity in the future.展开更多
A method for fabricating deep grating structures on a silicon carbide （SIC） surface by a femtosecond laser and chemical-selective etching is developed. Periodic lines corresponding to laser-induced structure change ...A method for fabricating deep grating structures on a silicon carbide （SIC） surface by a femtosecond laser and chemical-selective etching is developed. Periodic lines corresponding to laser-induced structure change （LISC） are formed by femtosecond laser irradiation, and then the SiC material in the LISC zone is removed by a mixed solution of hydrofluoric acid and nitric acid to form grating grooves. Grating grooves with a high-aspect ratio of approximately 25 are obtained. To obtain a small grating period, femtosecond laser exposure through a phase mask was used to fabricate grating structures with a 1.07 μm period on the surface of the SiC.展开更多
基金Project(51474237)supported by the National Natural Science Foundation of China
文摘The fluorine-based chemical method shows great potential in leaching lithium(Li) from lepidolite. Leaching kinetics of Li in a mixture of sulfuric acid and hydrofluoric acid, which is a typical lixivant for the fluorine-based chemical method, was carried out under crucial factors such as different HF/ore ratios(1:1-3:1 g/mL) and leaching temperatures(50-85℃). The kinetics data fit well with the developed shrinking-core model, indicating that the leaching rate of Li was controlled by the chemical reaction and inner diffusion at the beginning of leaching(0-30 min) as a calculated apparent activation energy(Ea) of 20.62 kJ/mol. The inner diffusion became the rate-limiting step as the leaching continues(60-180 min). Moreover, effects of HF/ore ratio and leaching temperature on selective leaching behavior of Li, Al and Si were discussed. 90% of fluorine mainly existed as HF/F-in leaching solution, which can provide theoretical guidance for further removal or recovery of F.
基金Project(2009FJ1009) supported by Major Program of Hunan Provincial Science and Technology, ChinaProject(2005CB6237) supported by the National Basic Research Program of China
文摘Leaching kinetics of acid-soluble Cr（VI） in chromite ore processing residue （COPR） using hydrofluoric （HF） acid solution as a leaching agent was investigated for potential remediation of COPR with industrial waste water containing HF. The results show that HF can effectively destabilize the Cr（VI）-bearing minerals, resulting in the mobilization of Cr（VI） from COPR into the leachate. Particle size significantly influences the leaching of acid-soluble Cr（VI） from COPR, followed by leaching time, whereas the effects of HF concentration and leaching temperature are slight and the influence of stirring rate is negligible. The leaching process of acid-soluble Cr（VI） from COPR is controlled by the diffusion through the product layer. The apparent activation energy is 8.696 kJ/mol and the reaction orders with respect to HF concentration and particle size is 0.493 8 and -2.013 3, respectively.
文摘AIM: To review the current evidence of the treatment of hydrofluoric acid(HF) exposure to the human cornea.METHODS: A comprehensive manual search of the literature was conducted through the Ovid interface to assess the mechanism and efficacy of each irrigator through a variety of clinical cases and experimental studies.· RESULTS: Ocular exposure to HF is extremely damaging to the eye and swift recognition and decontamination with an appropriate agent forms the basis of treatment. Although there are various decontamination solutions that have efficacy against the corrosive action of HF, irrigation with Hexafluorine proved to be the most safe and effective treatment for the eye.CONCLUSION: In conclusion emergency departments could benefit from the availability of Hexafluorine for the treatment of HF ocular burns in patients.
基金Supported by the National Nature Science Foundation of China,No.81701899 and No.81671911Youth Incubation Plan of the Military Medical Science and Technology,No.16QNP091+3 种基金Naval Medical University Youth Start-up Fund,No.2016QN10the Logistics Scientific Research Program,No.AWS14C001-4Jiangsu Provincial Health Commission Project,No.H2017071Suzhou Clinical Medical Center Construction Program,No.SZZXJ201506
文摘BACKGROUND Hydrofluoric acid(HF)is one of the most common causes of chemical burns.HF burns can cause wounds that deepen and progress aggressively.As a result,HF burns are often severe even if they involve a small area of the skin.Published cases of HF burns have mostly reported small HF burn areas.Few cases of HF inhalation injury have been reported to date.CASE SUMMARY A 24-year-old man suffered from extensive hydrofluoric acid burns covering 60%of the total body surface area(TBSA),including deep second degree burns on 47%and third degree burns on 13%of the TBSA,after he fell into a pickling pool containing 15%HF.Comprehensive treatments were carried out after the patient was admitted.Ventricular fibrillation occurred 9 times within the first 2 h,and the lowest serum Ca2+concentration was 0.192 mmol/L.A dose of calcium gluconate(37 g)was intravenously supplied during the first 24 h,and the total amount of calcium gluconate supplementation was 343 g.Extracorporeal membrane oxygenation(ECMO)was applied for 8 d to handle the acute respiratory distress syndrome(ARDS)induced by the HF inhalation injury.The patient was discharged after 99 d of comprehensive treatment,including skin grafting.CONCLUSION Extensive HF burns combined with an inhalation injury led to a potentially fatal electrolyte imbalance and ARDS.Adequate and timely calcium supplementation and ECMO application were the keys to successful treatment of the patient.
文摘The results of XPS measurements of commercially pure titanium cp-Ti) before and after chemical treatment are presented. We have measured XPS spectra of core levels (Ti 2p, O 1s, C 1s, F 1s) and valence bands of coarse-grained cp-Ti before and after standard acid treatment accepted in dentistry (in 1% HF and 40% HF for 1 min). It is found, that acid treatment of cp-Ti reduces the content of hydrocarbons increasing the surface energy and bio-compatibility of Ti-implants. On the other hand, it is fixed that oxygen concentration on the surface of the acid treated cp-Ti is much higher than for the untreated sample, because the acid treatment removes the contaminated surface layers, increases their reactivity, provides a better passivation and formation of thick protecting TiO2 layer.
基金supported by the National Key Research and Development Program of China(Grant Number 2021YFF0701-700)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB0590000).
文摘The development of a nucleophilic fluorination protocol using hydrofluoric acid as the fluoride source represents a long-sought goal in the field of organofluorine chemistry.We report herein the realization of such a reaction that employed alkyl-substituted sulfonium ylides as the substrates.The key to the success of the protocol was attributed to two factors:First,as a Brϕnsted base,the ylide was able to be protonated by HFaq,thus serving as a phase-transfer shuttle generated in situ to bring F−from aqueous phase to the organic phase promoting desolvation of fluoride ion.Second,after protonation,a sulfonium salt,a good leaving group,was generated and subsequent attacked by the fluoride to afford the alkyl fluoride.Mechanistic investigation indicates that the reaction occurs via an SN1 pathway.Because of the nature of the cationic intermediate in the reaction,two attractive rearrangement-fluorination approaches including 1,2-aryl migration fluorination and ring-expansion fluorination were disclosed.
基金the financial support from the National Key Research and Development Program of China (2022YFC3004500 and 2018YFC0808600)the Young Elite Scientists Sponsorship Program by CAST (2021QNRC001)Ningbo Natural Science Foundation (2021J006)
文摘This study investigates microstructure, hydrogen diffusion properties, and stress corrosion cracking(SCC) behavior of Q345R steel subject to pre-applied strains of 1 %, 3 %, and 5 %. The relationship between microstructure and SCC susceptibility in hydrofluoric acid(HF) vapor is examined. It is found that pre-strain cannot change the microstructure of Q345R steel but increases dislocation density. The increasing SCC sensitivity of Q345R steel in HF vapor is associated with the dislocation density induced by pre-strain. With increasing pre-strain, dislocation density and reversible hydrogen trap increase, and interaction between hydrogen and dislocation accelerates hydrogen-induced SCC. In addition, irreversible hydrogen traps caused by high pre-strain can severely aggravate hydrogen-induced SCC, resulting in high SCC vulnerability.
基金National Key Research and Development Program of China(2021YFC2902301,2021YFC2902302)。
文摘A transformative beryllium metallurgy theory and method was proposed based on the low-temperature dissociation of hydrofluoric acid and purification by exploiting the large difference of fluoride solubility.Hydrofluoric acid can quickly dissociate berylum ore powder directly at low or room temperature with more than 99%dissociation rate.The solubility of AlF_(3),FeF_(3) CrF_(3) and MgF_(2),is low.Coupled with common ion effect,99.9%-purity beryllium products can be prepared without chemical purification.For high-purity beryllium products of grade 4N or higher,they can be prepared through the superior property that the pH intervals of iron,chromium,and other hydroxide precipitates are distinctly different from those corresponding to Be(OH)_(2),precipitates.This new method can be used to prepare most of the beryllium products that are prepared by modern beryllium metallurgy.
基金supported by the Nano&Material Technology Development Program through the National Research Foundation of Korea(NRF),funded by the Ministry of Science and ICT(RS-2023-00234757).
文摘Although hydrofluoric acid(HF)surface treatment is known to enhance the joining of metals with polymers,there is limited information on its effect on the joining of AZ31 alloy and carbon-fiber-reinforced plastics(CFRPs)through laser-assisted metal and plastic direct joining(LAMP).This study uses the LAMP technique to produce AZ31-CFRP joints.The joining process involves as-received AZ31,HFpretreated AZ31,and thermally oxidized HF-pretreated AZ31 alloy sheets.Furthermore,the bonding strength of joints prepared with thermally oxidized AZ31 alloy sheets is examined to ascertain the combined effect of HF treatment and thermal oxidation on bonding strength.The microstructures,surface chemical interactions,and mechanical performances of joints are investigated under tensile shear loading.Various factors,such as bubble formation,CFRP resin decomposition,and mechanical interlocking considerably affect joint strength.Additionally,surface chemical interactions between the active species on metal parts and the polar amide along with carbonyl groups of polymer play a significant role in improving joint strength.Joints prepared with surface-pretreated AZ31 alloy sheets show significant improvements in bonding strength.
基金Project(51474237) supported by the National Natural Science Foundation of China
文摘An enhanced leaching of Li fromα-spodumene was carried out using a mixture of hydrofluoric and sulfuric acid(HF/H_(2)SO_(4))as the medium.Based on the optimized leaching conditions,the leaching kinetics of Li was investigated in an ore/HF/H_(2)SO_(4) ratio of 1:3:2 g:mL:mL with leaching temperature ranging from 50 to 100°C.The results indicate that the leaching kinetics of Li fitted well with a model based on the shrinking core model.In addition,the leaching rate of Li was controlled by chemical reactions and diffusion through the product layers.The apparent activation energy Ea was calculated to be 32.68 kJ/mol.Solid films were formed because of the generation of insoluble products such as cryolithionite(Na_(3)Li_(2)Al2F _(12) ),cryolite(Na_(3)AlF_(6)),calcium fluoride(CaF_(2)),potassium cryolite(K_(2)AlF_(5)),aluminum fluoride(AlF_(3)),and fluorosilicates(Na_(2)SiF_(6 )or KNaSiF_(6)).Furthermore,the effects of the ore/HF ratio and leaching temperature on the leaching behavior of Li,Al and Si were investigated.The results indicate that the ore/HF ratio and leaching temperature could clearly affect the distribution of HF molecules on the leaching of Li,Al and Si,which are important for the selective leaching of Li over Al and Si with this fluorine-based chemical method.
文摘Coal is the world＇s most abundant energy source because of its abundance and relatively low cost. Due to the scarcity in the supply of high-grade coal, it is necessary to use low-.grade coal for fulfilling energy demands of modern civilization. However, due to ItS high ash and moisture content, low-grade coal exerts the substantial impact on their consumption like pyrolysis, liquefaction, gasification and combus- tion process. The present research aimed to develop the efficient technique for the production of clean coal by optimizing the operating parameters with the help of response surface methodology. The effect of three independent variables such as hydrofluoric acid （HF） concentration （10-20% by vo!ume ）,. temper- ature （60-100 ~C）, and time （90-180 min）, for ash reduction from the low-grade coal was Investigated.. A quadratic model was proposed to correlate the independent variables for maximum ash reduction at the optimum process condition by using central composite design （CC.D）method. The study reveals that HF concentration was the most effective parameter for ash reduction in comparison with time and temper- ature. It may be due to the higher F-statistics value for HF concentration, which effects to large extent of ash reduction. The characterization of coal was evaluated by Fourier transform infrared spectroscopy （FTIR） analysis and Field-emission scanning electron microscopy with energy-dispersive X-ray （FESEM- EDX） analysis for confirmation of the ash reduction.
基金supported by the National Nature Scien- ce Foundation of China (Grant No.60672015).
文摘Fiber Bragg grating Fabry-Perot (FBG F-P) cavity is used as the sensing model to measure the refractive index of the liquid solution. The cladding of the fiber, which is used as the F-P cavity, is etched by HF solution to enhance the sensitivity to the external refractive index. The experimental results show that with the concentration change of the external solution, the effective refractive index of etched fiber will change, thus the spectra of FBG F-P cavity will appear a spilt point. The relationship be...
基金Projects(51274240,51204209)supported by the National Natural Science Foundation of China
文摘In order to extract gallium from a high-silica-content flue dust generated in corundum production,a mixed acid solution of H2SO4 and HF was used for leaching,and test parameters of the leaching process were optimized.Experimental results show that the leaching rate of gallium was only 38%when H2SO4 was used as leaching agent.Composition analysis results of micro areas in this corundum flue dust indicate that the content of gallium in silica-enriched phases was high;this portion of gallium was insoluble in H2SO4 solution.The leaching rate of gallium increased significantly with addition of HF due to corrosion of silica.Effects of reaction time,temperature,and concentrations of HF and H2SO4 on leaching rates of gallium were investigated.The leaching rate of gallium reached 91%when this corundum flue dust was leached in a mixed acid solution of H2SO4 and HF for 4 h,at a temperature of 80°C,with a liquid-to-solid ratio of 5:1(mL/g).The optimal concentrations of H2SO4 and HF in the mixed acid solution were 1.5 and 6.4 mol/L,respectively.
基金supported in part by Deanship of Research, Taibah University, Kingdom of Saudi Arabia, and Matt Winstead, CDT, Vice President, Oral Arts Dental Labs, Huntsville, AL, USA
文摘The aim of this study was to determine if accelerated aging of porcelain veneering had an effect on the surface properties specific to a tetragonal-to-monoclinic transformation（TMT） of zirconia restorations. Thirty-six zirconia samples were milled and sintered to simulate core fabrication followed by exposure to various combinations of surface treatments including as-received（control）,hydrofluoric acid（HF）, application of liner plus firings, application of porcelain by manual layering and pressing with firing, plus accelerated aging. The quantity of transformed tetragonal to monoclinic phases was analyzed utilized an X-ray diffractometer and one-way analysis of variance was used to analyze data. The control samples as provided from the dental laboratory after milling and sintering process had no TMT（X m5 0）. There was an effect on zirconia samples of HF application with TMT（X m5 0.8%） and liner plus HF application with TMT（X m5 8.7%）. There was an effect of aging on zirconia samples（no veneering） with significant TMT（X m5 70.25%）. Both manual and pressing techniques of porcelain applications reduced the TMT（manual, X m5 4.41%, pressing,X m5 11.57%）, although there was no statistical difference between them. It can be concluded that simulated applications of porcelain demonstrated the ability to protect zirconia from TMT after aging with no effect of a liner between different porcelain applications.The HF treatment also caused TMT.
基金supported by the National Natural Science Foundation of China (Nos.60837002 and 61177069)the Ph.D. Programs Foundation of Ministry of Education of China (No.20090009110003)the Fundamental Research Funds for the Central Universities (No.2011YJS219)
文摘A new method is presented to tune Bragg wavelength slightly by using hydrofluoric acid to etch fiber cladding.The spectral characteristics before and after etching and the change properties of Bragg wavelength are studied.Cladding modes are reduced during the etching process.High-order cladding modes are converted into radiation modes,and energy of cladding modes is coupled to the outside.As the cladding radius decreases,the Bragg wavelength shifts to longer direction.Experimental results show that this method can tune Bragg wavelength slightly,and the tunable range is 0.002-0.120 nm.
文摘Abstract: In the occurrence of arc discharges, spark discharges, corona discharges and overheated faults in electrical equipment, SF 6would be decomposed to complicated byproducts, such as SO2 , H2S and HF. Analyzing these byproducts is an effective method to judge the internal operation condition of electric equipment. In order to study characters of SF6byproducts at different temperature of overheated faults in the electric equipment, a series of overheated faults of electric equipment were simulated. SF6is very stable and not significantly decomposed at 200oC, 250oC and 300oC. SF6is significantly decomposed to SO2, H2S and HF at 350oC. The concentration of SO2, H2S and HF was 7.2, 1.6 and 1.9 μL/L after heating for 5 hours in environment of SF6with 3616 μL/L water, and it was increased to 23.0, 3.0 and 1.2 μL/L 3 hours later. SF6is more easily to be decomposed and decomposed more rapidly at higher temperature. The concentration of SO2, H2S and HF was 62.2, 15.6 and 3.6 μL/L after heating for 5 hours in environment of SF6with 4064 μL/L water, and it was increased to 91.4, 25.2 and 2.3 μL/L 3 hours later. SF6will be decomposed to format HF, which is strongly corrosive and whose concentration is likely to decrease when it is above a certain concentration.
文摘Mixtures of lanthanum oxide, europium oxide, and phosphoric acid were heated with various ratios of P/(La + Eu) and Eu/(La + Eu). The obtained phosphates were estimated using XRD patterns, FT-IR spectra, and SEM images. The fluo-rescence spectra and resistance against hydrofluoric acid were estimated as functional properties of these phosphate materials. The condensed phosphates showed a strong peak at 615 nm and high resistance against hydrofluoric acid.
文摘Mixtures of lanthanum oxide, europium oxide, calcium carbonate, and phosphoric acid were heated with various ratios of P/(Eu + La + Ca) and La/Ca. Europium ratio was settled at Eu/(Eu + La + Ca) = 0.03. The obtained phosphates were estimated using X-ray diffraction (XRD) patterns, Fourier transform infrared spectroscopy (FT-IR) spectra, and scanning electron micrograph (SEM) images. The fluorescence spectra and resistance against hydrofluoric acid were estimated as functional properties of these phosphate materials. The mixture of lanthanum and calcium phosphates were formed from XRD patterns and IR spectra. Samples prepared in P/(Eu + La + Ca) = 2 and 3 had large particles in SEM images. The condensed phosphates showed a strong peak at 615 nm and high resistance against hydrofluoric acid.
基金supported by the National "973" Program of China (No. 2010CB327800)the Natural Science Foundation of Jiangsu Province of China (No.BK2010247)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘A simple and compact refractive index sensor is demonstrated by tapering a photonic crystal fiber （PCF） in-line interferometer. The PCF is spliced between two single-mode fibers and tapered via hydrofluoric acid etching. Its sensitivity in liquid is more than an order of magnitude larger than the untapered one. By optimizing the etching process, we can fabricate more uniformly and thinly tapered PCF interferometers with higher sensitivity in the future.
基金supported by the Collaborative Innovation Center of Suzhou Nano Science and Technologysupported by the National Basic Research Program of China (No.2012CB921804)+1 种基金the National Natural Science Foundation of China (Nos.11204236 and 61308006)The SEM work was done at the International Center for Dielectric Research (ICDR),Xi’an Jiaotong University,Xi’an,China
文摘A method for fabricating deep grating structures on a silicon carbide （SIC） surface by a femtosecond laser and chemical-selective etching is developed. Periodic lines corresponding to laser-induced structure change （LISC） are formed by femtosecond laser irradiation, and then the SiC material in the LISC zone is removed by a mixed solution of hydrofluoric acid and nitric acid to form grating grooves. Grating grooves with a high-aspect ratio of approximately 25 are obtained. To obtain a small grating period, femtosecond laser exposure through a phase mask was used to fabricate grating structures with a 1.07 μm period on the surface of the SiC.
