Hydrofluoric acid

Wet etching in hydrofluoric acid (HF) is one of the most common routes for the surface texturing of silica, leading to improved optical properties, which find applications in several fields. In this work, wet etching of silica is mediated by the deposition of chemically synthesized gold nanoparticles on the substrate. Nanoparticles of different sizes are coated on silica and act as a mask when etching using HF. The effect of parameters such as etching time, nanoparticle size, and HF concentration on the surface morphologies and transmittance are studied and correlated with the chemical etching mechanism. This work reveals that a proper choice of masking and etching conditions can reduce the optical transmission of silica. Etching leads to the formation of arrays of micron-size elongated pits. The pit width and surface roughness are found to increase with etching time and HF concentration, in turn leading to a decrease in transmittance. The results show that nanoparticle masking is a...

Improvements in the synthesis, deprotection and purification of oligoribonucleotides are described. These advances allow for reduced synthesis and deprotection times, while improving product yield. Coupling times are reduced by half using 5-ethyrthic-1 H-tetrazole (S-ethyltetrazole) as the activator. Base and Z-O-tbutyldimethylsllyl deprotection with methylamlne (MA) and anhydrous trtethylamlne/hydrogen fluoride In W-methylpyrrolidinone (TEAHF/NMP), respectively, requires a fraction of the time necessitated by current standard methods. In addition, the ease of ollgoribonucleotlde purification and analysis have been significantly enhanced using anion exchange chromatography. These new methods Improve the yield and quality of the oligoribonucleotides synthesized. Hammerhead ribozymes synthesized utilizing the described methods exhibited no diminution in catalytic activity.

Silicon wafers were cut into the samples with a size of 1×1 cm 2 . To remove various contaminations from the surface, a standard RCA clean procedure was employed. After ultrasonication in acetone, water and ethanol for 15 min at each step and degreasing in Piranha solution (98% H 2 SO 4 /30% H 2 O 2 = 3:1, v/v) at room temperature for 30 min, the native oxide layer was finally removed in 5% HF for 5 min. For one-step MACE, we have used a water solution containing AgNO 3 (0.02 M)/HF(2.0 M) for 60 min. At the final step, Si samples were Electronic Supplementary Material (ESI) for Analytical Methods.

In this study, dense gold-assembled SiO 2 nanostructure (SiO 2 @Au) was successfully developed using the Au seed-mediated growth. First, SiO 2 (150 nm) was prepared, modified by amino groups, and incubated by gold nanoparticles (ca. 3 nm Au metal nanoparticles (NPs)) to immobilize Au NPs to SiO 2 surface. Then, Au NPs were grown on the prepared SiO 2 @Au seed by reducing chloroauric acid (HAuCl 4) by ascorbic acid (AA) in the presence of polyvinylpyrrolidone (PVP). The presence of bigger (ca. 20 nm) Au NPs on the SiO 2 surface was confirmed by transmittance electronic microscopy (TEM) images, color changes to dark blue, and UV-vis spectra broadening in the range of 450 to 750 nm. The SiO 2 @Au nanostructure showed several advantages compared to the hydrofluoric acid (HF)-treated SiO 2 @Au, such as easy separation, surface modification stability by 11-mercaptopundecanoic acid (R-COOH), 11-mercapto-1-undecanol (R-OH), and 1-undecanethiol (R-CH 3 ), and a better peroxidase-like catalysis activity for 5,5 -Tetramethylbenzidine (TMB) and hydrogen peroxide (H 2 O 2 ) reaction. The catalytic activity of SiO 2 @Au was two times better than that of HF-treated SiO 2 @Au. When SiO 2 @Au nanostructure was used as a surface enhanced Raman scattering (SERS) substrate, the signal of 4-aminophenol (4-ATP) on the surface of SiO 2 @Au was also stronger than that of HF-treated SiO 2 @Au. This study provides a potential method for nanoparticle preparation which can be replaced for Au NPs in further research and development.

In this study, dense gold-assembled SiO2 nanostructure (SiO2@Au) was successfully developed using the Au seed-mediated growth. First, SiO2 (150 nm) was prepared, modified by amino groups, and incubated by gold nanoparticles (ca. 3 nm Au metal nanoparticles (NPs)) to immobilize Au NPs to SiO2 surface. Then, Au NPs were grown on the prepared SiO2@Au seed by reducing chloroauric acid (HAuCl4) by ascorbic acid (AA) in the presence of polyvinylpyrrolidone (PVP). The presence of bigger (ca. 20 nm) Au NPs on the SiO2 surface was confirmed by transmittance electronic microscopy (TEM) images, color changes to dark blue, and UV-vis spectra broadening in the range of 450 to 750 nm. The SiO2@Au nanostructure showed several advantages compared to the hydrofluoric acid (HF)-treated SiO2@Au, such as easy separation, surface modification stability by 11-mercaptopundecanoic acid (R-COOH), 11-mercapto-1-undecanol (R-OH), and 1-undecanethiol (R-CH3), and a better peroxidase-like catalysis activity for...

This work consists in elaborating a gas sensor based on porous silicon and a polypyrrole obtained by covalent grafting and studying its answer in different environments. At first, we were interested in the formation of the nanoporous layers by cyclovoltammetric (CV) in a hydrofluoric acid solution followed by an electrochemical grafting of the polypyrrole (PPy) on the porous silicon and oxide porous silicon surfaces. The various interfaces were characterized using different techniques such as Fourier transform infrared spectroscopy (FT-IR), energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). Finally, a series of electric characterizations to study the answer of the structures in the contact of the carbon dioxide was achieved.

The industrial partner manufactures high quality lead crystal glassware. The cutting of decorative features in the glass damages the surface and the cuts are optically opaque; to restore transparency, the glass is polished in a solution of hydrofluoric (HF) and sulphuric acid (H2 SO4 .) The polishing process comprises three stages: 1. immersion in a polishing tank containing acid; 2. rinsing in a tank containing water; and 3. settlement of the solid reaction products in a settlement tank. The manufacturer hopes to optimise its polishing process to • minimise the health/environmental impact of the process; • maximise throughput; • maintain the sharpness of the cut edges while still polishing to an acceptable level of transparency. The study group was asked to focus on modelling three aspects of the process: • the chemical reactions involved in the etching at the glass-acid solution interface; • the removal of reaction products in the settlement tank; • flow within the polishing tank.

In this paper, thin films of copper oxide nanoparticles mixed with 2% wt of nickel oxide are deposited on glass and porous silicon (PS) substrates with orientation (111) etched at 30 minutes. The current density was varied from (10 to 50) mA/cm2 with a step of 10 utilizing pulsed laser deposition technique for the manufacture of hydrogen gas sensor. The films are annealed in air at 400 °C for two hours. The PL result of PS shows that the peak position is shifted to the higher wavelength region due to increase etching current. On the other hand, the atomic force microscopy shows an increase in average diameter with increasing etching current (10-30) mA then decrease. Moreover, the FTIR spectra of porous silicon exhibit that the pore surface includes a high density of dangling bonds of Si for original impurities such as hydrogen and fluorine, which are residuals from the electrolyte. Finally the sensitivity of the hydrogen gas sensor are increased with increasing operating temperature.

To advance the MXene field, it is crucial to optimize each step of the synthesis process and create a detailed, systematic guide for synthesizing high‐quality MXene that can be consistently reproduced. In this study, a detailed guide is provided for an optimized synthesis of titanium carbide (Ti3C2Tx) MXene using a mixture of hydrofluoric and hydrochloric acids for the selective etching of the stoichimetric‐Ti3AlC2 MAX phase and delamination of the etched multilayered Ti3C2Tx MXene using lithium chloride at 65 °C for 1 h with argon bubbling. The effect of different synthesis variables is investigated, including the stoichiometry of the mixed powders to synthesize Ti3AlC2, pre‐etch impurity removal conditions, selective etching, storage, and drying of MXene multilayer powder, and the subsequent delamination conditions. The synthesis yield and the MXene film electrical conductivity are used as the two parameters to evaluate the MXene quality. Also the MXenes are characterized with sca...

Sediments as a tool for monitoring contamination by heavy metals in the environment has long been considered. It is therefore a necessity to produce reliable data for such purposes. Microwave-assisted acid dissolution has proved to be a suitable method for digesting complex matrices, such as sediments. However, due to the infancy of the technique, the procedures are numerous and varied in both the reagents used and microwave conditions. In this study, the efficiency of two recommended acid mixtures, a HNO3-HF mixture and an aqua regia-HF mixture, under the same microwave digestion conditions were compared using certified reference materials. It was observed that the HNO3-HF mixture showed better efficiency than the aqua regia-HF mixture in most of the heavy metals analyzed in all certified reference materials used.

Sediments as a tool for monitoring contamination by heavy metals in the environment has long been considered. It is therefore a necessity to produce reliable data for such purposes. Microwave-assisted acid dissolution has proved to be a suitable method for digesting complex matrices, such as sediments. However, due to the infancy of the technique, the procedures are numerous and varied in both the reagents used and microwave conditions. In this study, the efficiency of two recommended acid mixtures, a HNO3-HF mixture and an aqua regia-HF mixture, under the same microwave digestion conditions were compared using certified reference materials. It was observed that the HNO3-HF mixture showed better efficiency than the aqua regia-HF mixture in most of the heavy metals analyzed in all certified reference materials used.

The quantitative determination of average roughness parameters, from the determination of height variations of the surface points, is frequently used to estimate the adhesion between an adhesive and the surface of a substrate. However, to determine the interaction between an adhesive and a surface of a heterogeneous material, such as a red ceramic, it is essential to define other roughness parameters. This work proposes a method for determining the roughness of red ceramic blocks from a three-dimensional evaluation, with the objective of estimating the contact area that the ceramic substrate can provide for a cementitious matrix. The study determines the average surface roughness from multiple planes and proposes the adoption of 2 more roughness parameters, the valley area index and the average valley area. The results demonstrate that there are advantages in using the proposed multiple plane method for roughness computation and that the valley area parameters are efficient to estimate the extent of adhesion between the materials involved.

This work describes the fabrication of anisotropically etched, faceted pyramidal structures in amorphous layers of silicon dioxide or glass. Anisotropic and crystal‐oriented etching of silicon is well known. Anisotropic etching behavior in completely amorphous layers of silicon dioxide in combination with purely isotropic hydrofluoric acid as etchant is an unexpected phenomenon. The work presents practical exploitations of this new process for self‐perfecting pyramidal structures. It can be used for textured silica or glass surfaces. The reason for the observed anisotropy, leading to enhanced lateral etch rates, is the presence of thin metal layers. The lateral etch rate under the metal significantly exceeds the vertical etch rate of the non‐metallized area by a factor of about 6–43 for liquid and 59 for vapor‐based processes. The ratio between lateral and vertical etch rate, thus the sidewall inclination, can be controlled by etchant concentration and selected metal. The described ...

Background: Hydrofluoric acid (HF) is an extremely dangerous weak inorganic acid, which can produce extensive burn lesions, depending especially on the solution concentration and exposure time, systemic toxicity occurring in patients with large burn areas, high concentration of acid or an extensive time of exposure. The subcutaneous infi ltration and intravenous administration of calcium gluconate is essential for preventing dyselectrolytemia and severe pain appearance. Case summary: A 26-year-old man patient presented to our hospital after a hydrofluoric burn, secondary to an occupational accident. At the scene, the wound was irrigated with fresh water and topical calcium gluconate was applied. In the Emergency Department, we started the intravenous calcium gluconate administration, and in the Burn Unit it was injected subcutaneously and the pain was thus diminished. A prolonged QT interval was identifi ed upon admission that has been corrected over the next few days. Particularly, the serum pseudocholinesterase levels were within normal range. The local treatment involved repeated copious lavage with sterile water and Betadine solution, the evolution being rapidly favorable with the burn lesions completely healed in the next week. Conclusion: HF burns are a very special type of chemical burn taking into account that exposure to a small quantity of solution can be life threatening and that the immediate treatment is mandatory in order to maximize the outcome. It is of vital importance that any medical facility had a chemical burn protocol.

Background: Hydrofluoric acid (HF) is an extremely dangerous weak inorganic acid, which can produce extensive burn lesions, depending especially on the solution concentration and exposure time, systemic toxicity occurring in patients with large burn areas, high concentration of acid or an extensive time of exposure. The subcutaneous infi ltration and intravenous administration of calcium gluconate is essential for preventing dyselectrolytemia and severe pain appearance. Case summary: A 26-year-old man patient presented to our hospital after a hydrofluoric burn, secondary to an occupational accident. At the scene, the wound was irrigated with fresh water and topical calcium gluconate was applied. In the Emergency Department, we started the intravenous calcium gluconate administration, and in the Burn Unit it was injected subcutaneously and the pain was thus diminished. A prolonged QT interval was identifi ed upon admission that has been corrected over the next few days. Particularly, the serum pseudocholinesterase levels were within normal range. The local treatment involved repeated copious lavage with sterile water and Betadine solution, the evolution being rapidly favorable with the burn lesions completely healed in the next week. Conclusion: HF burns are a very special type of chemical burn taking into account that exposure to a small quantity of solution can be life threatening and that the immediate treatment is mandatory in order to maximize the outcome. It is of vital importance that any medical facility had a chemical burn protocol.

To advance the MXene field, it is crucial to optimize each step of the synthesis process and create a detailed, systematic guide for synthesizing high‐quality MXene that can be consistently reproduced. In this study, a detailed guide is provided for an optimized synthesis of titanium carbide (Ti3C2Tx) MXene using a mixture of hydrofluoric and hydrochloric acids for the selective etching of the stoichimetric‐Ti3AlC2 MAX phase and delamination of the etched multilayered Ti3C2Tx MXene using lithium chloride at 65 °C for 1 h with argon bubbling. The effect of different synthesis variables is investigated, including the stoichiometry of the mixed powders to synthesize Ti3AlC2, pre‐etch impurity removal conditions, selective etching, storage, and drying of MXene multilayer powder, and the subsequent delamination conditions. The synthesis yield and the MXene film electrical conductivity are used as the two parameters to evaluate the MXene quality. Also the MXenes are characterized with sca...

One industrially important metal oxide nanoparticle (NP) is cadmium oxide (CdO). A study was performed using timedpregnant CD-1 mice to determine if Cd associated with inhaled CdO NP could reach the placenta and adversely affect the developing fetus and/or neonate. Pregnant mice were exposed by inhalation either every other day to 100 mg of freshly generated CdO/m 3 (exposure 1) or daily to 230 mg CdO/m 3 (exposure 2). In each exposure, mice were exposed to CdO NP or carrier gas (control) for 2.5 h from 4.5 days post coitus (dpc) through 16.5 dpc. At 17.5 dpc, fetuses and placentas from both exposures 1 and 2 were collected, measured, and weighed. A subgroup from the second exposure was allowed to give birth, and neonates were weighed daily until weaning. Cadmium in the uterus and placenta, as well as in other maternal organs, was elevated in NP-treated mice, but was undetectable in fetuses at 17.5 dpc. Daily inhalation of 230 mg CdO NP/m 3 decreased the incidence of pregnancy (i.e., no evidence of implantation) by 23%, delayed maternal weight gain, altered placental weight, and decreased fetal length, as well as delayed neonatal growth. This study demonstrates that inhalation of CdO NP during pregnancy adversely affects reproductive fecundity and alters fetal and postnatal growth of the developing offspring.

AlF3 has interesting electrophysical properties, due to which the material is promising for applications in supercapacitors, UV coatings with low refractive index, excimer laser mirrors, and photolithography. The formation of AlF3-based nano- and micro-wires can bring new functionalities to AlF3 material. AlF3 nanowires are used, for example, in functionally modified microprobes for a scanning probe microscope. In this work, we investigate the AlF3 samples obtained by the reaction of initial aluminum with an aqueous hydrofluoric acid solution of different concentrations. The peculiarity of our work is that the presented method for the synthesis of AlF3 and one-dimensional structures based on AlF3 is simple to perform and does not require any additional precursors or costs related to the additional source materials. All the samples were obtained under normal conditions. The morphology of the nanowire samples is studied using scanning electron microscopy. We performed an intermediate ...

Background: Fracture of ceramic-metal restorations is a major problem facing the dentists and the patients. There are several bonding systems currently available in the market to repair the fractured ceramic-metal restorations inside or outside the oral cavity. Purpose: The purpose of this study was to test the efficiency of repairing of metal-ceramic restorations using different bonding systems with different surface treatments. This efficiency was tested through the conduction of shear bond strength of the composite bonded to the porcelain and to nickel-chromium alloy using three different bonding agents (Excite, AdheSE, and Prompt L-Pop) with four different surface treatments (sandblasting and enchant, diamond stone roughening, sandblasting and hydrofluoric acid etching, or without surface treatment). Materials and Methods: A total of 120 specimens were prepared, 60 specimens from porcelain and 60 specimens from nickel-chromium alloy. Each group was divided into three equal subgroups, 20 specimens each, corresponding to the 3 bonding agents used. Each subgroup was further subdivided into four subgroups, 5 specimens each, corresponding to the surface treatment procedures. Bonding agents applied over all specimens and cured, followed by application of a microhybrid light-cured composite resin (Tetric Ceram).Thermal cycling was done for all specimens between 5°C and 55°C for 1000 cycles with a 10-second dwell time. Shear bond strength test was conducted using a universal testing machine at a cross-head speed of 0.5 mm/min. Results: The highest shear bond strength value recorded for the porcelain specimens bonded with Excite bonding agent with surface treatment sandblasting and hydrofluoric acid etching. In metal groups, the AdheSE bonding agent showed the highest shear bond strength value with the same surface treatment of the porcelain specimens. It was observed that sandblasting followed by hydrofluoric acid etching produced the most effective treatment method for porcelain and metal surfaces. Conclusion: The most effective technique for repairing metal ceramic restoration was sandblasting with hydrofluoric acid etching as surface treatment together with AdheSE or Excite bonding agents.

Objective This study investigates the effect of different chemical surface treatment protocols with different functional monomers of universal adhesives on the shear bond strength between resin-matrix ceramic and resin composite. Materials and Methods Eighty resin-matrix ceramics (Shofu block HC) were built and designed into eight groups of ten specimens and surface treated with HC primer (HC) and/or three universal adhesives (single bond universal [SBU], Scotchbond universal plus [SBP], and Tetric N-bond universal [TNU]) assigning follows; group 1, nonsurface treated; group 2, HC; group 3, SBU; group 4, HC þ SBU; group 5, SBP; group 6, HC þ SBP; group 7, TNU; group 8, HC þ TNU. A template was put on the specimen center, and then pushed packable resin composite. Mechanical testing machinery was used to examine the samples' shear bond strength (SBS) values. To examine failure patterns, the debonded specimen surfaces were examined by a stereomicroscope. Statistical Analysis The one-way analysis of variance method was used to evaluate the data, and the Tukey's test was used to determine the significant level (p < 0.05). The highest SBS was obtained in group 6 (39.25 AE 1.65 MPa). Group 1 (4.15 AE 0.54 MPa) had the lowest SBS. Group 6 exhibited the highest percentage of cohesive failure patterns (70%). High SBS values were frequently correlated with the surface treatment groups and the cohesive failure patterns. Conclusion The application of HC primer prior to the universal adhesive is an alternative protocol for enhancing the repair bond strength between resin-matrix ceramic and resin composite interfaces. Moreover, the application of HC primer prior to the SBP is the best strategy for resin-matrix ceramic and resin composite repairs.

As a result of the rapid reduction in productivity of well B14, south west of the Niger Delta region, the need to investigate the cause of the damage was initiated. When it was identified fine migration as the major cause of the production decline, acid stimulation was recommended as the mitigation strategy. Acid (matrix) stimulation practice involves the pumping of acid into the formation through the wellbore at the rates and pressures below the fracture gradient of the formation. Conventionally, hydrochloric acid (HCL) is used for carbonate formations while hydrofluoric acid (HF)/ mud acid (HCL +HF) is best suited for sandstone formations. Also, in a very high damaged formation and very high temperature environment that requires prolong contact of the HCL acid with the steel pipe, due to the severe corrosion that will occur, organic acids are more suitable. In stimulating this well, mud acid was used and the well was stimulated using organic mud acid or organic clay acid. Stimulat...

Recently, approximately 80% of participating laboratories failed to accurately determine uranium isotopes in soil samples in the U.S Department of Energy Mixed Analyte Performance Evaluation Program (MAPEP) Session 30, due to incomplete dissolution of refractory particles in the samples. Failing laboratories employed acid dissolution methods, including hydrofluoric acid, to recover uranium from the soil matrix. The failures illustrate the importance of rugged soil dissolution methods for the accurate measurement of analytes in the sample matrix. A new rapid fusion method has been developed by the Savannah River National Laboratory (SRNL) to prepare 1-2 g soil sample aliquots very quickly, with total dissolution of refractory particles. Soil samples are fused with sodium hydroxide at 600 o C in zirconium crucibles to enable complete dissolution of the sample. Uranium and thorium are separated on stacked TEVA and TRU extraction chromatographic resin cartridges, prior to isotopic measurements by alpha spectrometry on cerium fluoride microprecipitation sources. Plutonium can also be separated and measured using this method. Batches of 12 samples can be prepared for measurement in <5 hours.

The rapid measurement of 89/90 Sr in steel samples is important in the event of a radiological emergency as well as for the characterization of routine nuclear decommissioning samples. A new method for the determination of radiostrontium in steel samples has been developed at the Savannah River Environmental Laboratory. The new method employs a rugged acid digestion that includes hydrofluoric acid, followed by a single preconcentration step to rapidly collect the radiostrontium and remove nearly all of the high iron content. A fusion step can be implemented after the steel dissolution when soil, concrete, or highly refractory particles are present. The 89 Sr + 90 Sr and/or 90 Y are separated using extraction chromatographic resins and measured radiometrically, either by gas flow proportional counting or liquid scintillation counting. Several approaches for the measurement of 89 Sr + 90 Sr, 90 Sr, and discrimination between 89 Sr and 90 Sr are discussed. This approach has a sample preparation time for steel samples of 6-8 hours.

Recently, approximately 80% of participating laboratories failed to accurately determine uranium isotopes in soil samples in the U.S Department of Energy Mixed Analyte Performance Evaluation Program (MAPEP) Session 30, due to incomplete dissolution of refractory particles in the samples. Failing laboratories employed acid dissolution methods, including hydrofluoric acid, to recover uranium from the soil matrix. The failures illustrate the importance of rugged soil dissolution methods for the accurate measurement of analytes in the sample matrix. A new rapid fusion method has been developed by the Savannah River National Laboratory (SRNL) to prepare 1-2 g soil sample aliquots very quickly, with total dissolution of refractory particles. Soil samples are fused with sodium hydroxide at 600 o C in zirconium crucibles to enable complete dissolution of the sample. Uranium and thorium are separated on stacked TEVA and TRU extraction chromatographic resin cartridges, prior to isotopic measurements by alpha spectrometry on cerium fluoride microprecipitation sources. Plutonium can also be separated and measured using this method. Batches of 12 samples can be prepared for measurement in <5 hours.

The rapid measurement of plutonium isotopes in steel samples is very important in the event of a radiological emergency as well as for the characterization of nuclear decommissioning samples. A new method for the determination of plutonium isotopes in steel samples has been developed at the Savannah River Environmental Laboratory. The new method employs a rugged acid digestion method that includes hydrofluoric acid, followed by a single preconcentration step to rapidly preconcentrate the plutonium isotopes and remove most of dissolved steel sample matrix. A fusion option improves ruggedness when soil or concrete is present and can be implemented after steel dissolution. The Pu isotopes are separated using an extraction chromatographic resin and measured by alpha spectrometry. The method can also be adapted for measurement by inductively-coupled plasma mass spectrometry. This approach has a sample preparation time for steel samples of 6-8 hours.

In the present work, regularity of the pores generated during the electrochemical etching of silicon wafer is analyzed. The wafer-electrolyte (ethanolic hydrofluoric acid) composite is placed in an electrochemical cell operated galvanostatically at a fixed (set-point) anodic current. This set-point current is subsequently perturbed by a sub-threshold periodic current signal. Numerous experiments were performed for diverse experimental configurations. Some of the experimental parameters varied were hydrofluoric concentration, set-points, and the properties of the input periodic signal (i.e., duty cycle and amplitude). The regularity of the generated pore size distribution was quantified by calculating the spatial normalized variance (NV). For certain experimental configurations, as described later, the phenomena of Periodic Stochastic Resonance (PSR) could be provoked. In PSR, enhanced regularity of the Porous Silicon nanostructures for an optimal HF concentration is observed. Consequently, the spatial NV versus the HF concentration curve exhibits a unimodal profile.

The ordered LiNi0.5Mn1.5O4 spinel exhibits great promise as a potential high-energy positive electrode for lithium-ion batteries due to its exceptionally high working potential of 4.7 V (vs. Li) and energy density of 640 Wh kg-1. The commercial application of this material at such voltages is unfortunately prevented by reaction phenomena including hydrofluoric acid attack and manganese dissolution, as well as the two-phase mechanism of Li insertion and extraction, with these limiting Li diffusivity and cycling stability. In this work, we demonstrate the improved performance of LiNi0.5Mn1.5O4 achieved by encapsulating the material in a thin layer of silica (SiO2) or polyimide using a simple wet-chemical method and organic solvents. The pristine and coated ordered LiNi0.5Mn1.5O4 spinel are both confirmed to have P4332 symmetry, with only a minor difference in their lattice parameter. The SiO2 coating is found to reduce capacity fade of ordered LiNi0.5Mn1.5O4 by 45 and 65% at 25 and 55 °C, respectively, with the improvement attributed to enhanced Li diffusivity alongside the suppression of the hydrofluoric acid attack. The polyimide coating is found to have a marginally negative effect on both capacity and rate performance of ordered LiNi0.5Mn1.5O4, with this being greatly offset by excellent thermal stability leading to high-temperature protection, with the material having the low capacity fade of 0.0585 mAh g-1 cycle-1 at 55 °C, which is comparable to that at 25 °C. While similar effects of these coatings are found for disordered LiNi0.5Mn1.5O4, the magnitude of enhancement to properties offered by these coatings is significantly lesser than those found here for the ordered LiNi0.5Mn1.5O4. A stabilizing effect of the coatings that mitigates against phase segregation occurring during the additional two-phase reaction in the ordered but not the disordered phase of the material may explain the greater benefit of the coatings to the ordered phase. Publication Details

The ordered LiNi0.5Mn1.5O4 spinel exhibits great promise as a potential high-energy positive electrode for lithium-ion batteries due to its exceptionally high working potential of 4.7 V (vs. Li) and energy density of 640 Wh kg-1. The commercial application of this material at such voltages is unfortunately prevented by reaction phenomena including hydrofluoric acid attack and manganese dissolution, as well as the two-phase mechanism of Li insertion and extraction, with these limiting Li diffusivity and cycling stability. In this work, we demonstrate the improved performance of LiNi0.5Mn1.5O4 achieved by encapsulating the material in a thin layer of silica (SiO2) or polyimide using a simple wet-chemical method and organic solvents. The pristine and coated ordered LiNi0.5Mn1.5O4 spinel are both confirmed to have P4332 symmetry, with only a minor difference in their lattice parameter. The SiO2 coating is found to reduce capacity fade of ordered LiNi0.5Mn1.5O4 by 45 and 65% at 25 and 55 °C, respectively, with the improvement attributed to enhanced Li diffusivity alongside the suppression of the hydrofluoric acid attack. The polyimide coating is found to have a marginally negative effect on both capacity and rate performance of ordered LiNi0.5Mn1.5O4, with this being greatly offset by excellent thermal stability leading to high-temperature protection, with the material having the low capacity fade of 0.0585 mAh g-1 cycle-1 at 55 °C, which is comparable to that at 25 °C. While similar effects of these coatings are found for disordered LiNi0.5Mn1.5O4, the magnitude of enhancement to properties offered by these coatings is significantly lesser than those found here for the ordered LiNi0.5Mn1.5O4. A stabilizing effect of the coatings that mitigates against phase segregation occurring during the additional two-phase reaction in the ordered but not the disordered phase of the material may explain the greater benefit of the coatings to the ordered phase. Publication Details

Objective This study aimed to evaluate the bond strength between lithium disilicate ceramic and resinous cement when silane (Prosil, FGM) was applied in different amounts of layers under heating or not. Materials and Methods Sixty IPS E-max CAD ceramic (Ivoclar) was used. They were conditioned with 10% hydrofluoric acid for 20 seconds. The samples were distributed in six groups (n = 10): 1Sil, 1 layer of silane without heating; 1SilAq, 1 layer of silane with heating; 2Sil, 2 layers without heating; 2SilAq, 2 layers with heating; 3Sil, 3 layers without heating; and 3SilAq, 3 layers with heating. After each layer, a jet of cold air was applied for 20 seconds in groups 1Sil, 2Sil, 3Sil, and jet of hot air (50°C) in groups 1SilAq, 2SilAq, and 3SilAq. Subsequently, an adhesive layer was applied, and fourcylinders were made on the ceramic with a resin cement AllCemVeneer and photoactivated for 20 seconds. The samples were stored at 37°C for 24 hours and analyzed to the microshear test at ...

Considers of nanostructures created beneath different modes of submersion testimony of silver on permeable silicon (PS) for their utility as dynamic substrates in monster Raman spectroscopy (SRS) are displayed. PS was shaped by anodizing monocrystalline silicon in an aqueous-alcoholic arrangement of hydrofluoric corrosive. The reflection spectra of the gotten silver nanostructures on PC have been examined. It is uncovered that to form ideal conditions for SERS spectroscopy utilizing silver nanostructures on PC, it is vital to utilize an energizing laser with a wavelength of 400–450 nm.

The potential formation and the size of microgaps at the material/dentin interface after various surface modifications of a resin-matrix computer-aided design/computer-aided manufacturing (CAD/CAM) ceramic following artificial aging was investigated. Fifty human third molars were used, and a resin-matrix CAD/CAM ceramic, Lava Ultimate, and a resin cement material, Rely X Ultimate, were tested. CAD/CAM blocks were sectioned, and each slab was luted on the tooth surface using the same resin cement. The surface material was modified using the following treatments: Group 1—no treatment (control); Group 2—hydrofluoric acid (HF) + silane; Group 3—air abrasion with Al2O3 particles (29 μm); Group 4—air abrasion with Al2O3 particles (53 μm); and Group 5—erbium, chromium:yttrium–scandium–gallium–garnet (Er,Cr:YSGG) (2780 nm) laser treatment. The specimens were submitted to thermocycling (5000 cycles: 5 °C–55 °C) and then transversely cut in the middle and examined using scanning electron micr...

Aim: evaluate the influence of etching time with hydrofluoric acid on the bond strength of a Yttrium-stabilized polycrystalline tetragonal zirconia (Y-TZP) ceramic with a superficial glaze layer and a resin cement. Methods: Y-TZP blocks were cut to obtain 40 samples. They were distributed into four groups (n = 10): control treated by sandblasting with silica-coated alumina (RS) and three glazed experimental groups with different etching times: GS20s, GS60s and GS100s. Cementation was done with a universal adhesive and a resin cement. Two cement cylinders were made in each block. After thermocycling, the shear bond test was performed. Two extra samples of each group were made to obtain profilometry, scanning electron microscopy, mapping and backscattered electron detector images. Energy dispersive spectrometry and goniometry were also performed. Results: Kruskal-Wallis and Dunn tests demonstrated bond strength differences only between the RS (22.10MPa) and the GS groups (GS20s: 8,10M...

Introduction Despite being one of the most studied ceramics today, zirconia still does not have a well-defined adhesion protocol. Objective Evaluate the influence of different etching times and hydrofluoric acid (HF) concentrations on the zirconia surface and bond strength between a vitrified Y-TZP ceramic and a resin cement. Materials and method The zirconia surface treatments were: sandblasting with silica-coated alumina (Co); glaze application + 5% HF etching for 5s (G5-5s), 10s (G5-10s) or 20s (G5-20s); glaze application + 10% HF etching for 5s (G10-5s), 10 (G10-10s) or 20s (G10-20s) . Then, cement cylinders (3.3 × 3.3 mm) were built up for shear bond test on all specimens. The specimens were subjected to 6000 thermal cycling before the test. Fractures were analyzed by stereomicroscope. Data were statistically analyzed by Kruskal-Wallis and Dunn statistical tests (5%). Extra samples of each group were made to obtain profilometry and scanning electron microscopy (SEM). Result Zir...

Short-wavelength infrared radiation has been successfully applied to accelerate the acid digestion of refractory rare-earth ore samples. Determinations were achieved with microwave plasma-atomic emission spectrometry (MP-AES) and dynamic reaction cellinductively coupled plasma-mass spectrometry (DRC-ICP-MS). The digestion method developed was able to tackle high iron-oxide and silicate matrices using only phosphoric acid in a time frame of only 8 min, and did not require perchloric or hydrofluoric acid. Additionally, excellent recoveries and reproducibilities of the rare earth elements, as well as uranium and thorium, were achieved. Digestions of the certified reference materials OREAS-465 and REE-1, with radically different mineralogies, delivered results that mirror those obtained by fusion processes. For the rare-earth CRM OKA-2, whose REE data are provisional, experimental data for the rareearth elements were generally higher than the provisional values, often exceeding z-values of þ2. Determined values for Th and U in this reference material, for which certified values are available, were in excellent agreement.

Hydrofluoric acid readily penetrates the skin and mucous membranes, causing deep tissue layer destruction. Dermal exposure can produce hypocalcaemia, hypomagnesaemia, hyperkalaemia, cardiac dysrhythmias and death. We report the case of a 52-year-old man who presented hypocalcaemia and hypomagnesaemia due to occupational dermal contact with hydrofluoric acid. Hypocalcaemia and hypomagnesaemia were corrected by i.v. administration of calcium gluconate and magnesium sulphate.

Volatlliratlon and mass fractionation of boron during evapor a t h of the hydrofhwk and hyckocMorlc acid sdutions were investigated wRh varying mann#ol/boron ratlos. The degree of vdafllzation and mass fractlonatlon decreases with increasing mannltoVboron mole ratio, and the boron volatlllration Is completely suppressed when the ratio Is more than unlty. These resutts indicate that the flnai stable compound is an equimolar complex of boron and mannltol. The formation of this complex in the acid solutions allows the use of hydrofluorlc and hydrochloric acids for the dissolution of sllicate rock samples and for the subsequent chemical separation of boron from the samples adopting anion-exchange chromatography In F-form.

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Background and Aims: The aim of this study was to evaluate the quality of an experimental hydrofluoric acid (HF) for preparation of porcelain and to compare it with two commercial hydrofluoric acids in Iranian trademark. Materials and Methods: AEvaluation of etch pattern of experimental HF using scanning electron microscope (SEM): 6 feldespathic discs were divided into 3 groups. Each group was etched with related HF (experimental, Ultradent and Kimia) for 1 minute. SEM images were recorded at 3 magnifications. BBond strength test: 18 feldespathic discs were considered for each acidic group. Then the porcelain surfaces were etched and bonded to composite with unfilled resin. Consequently, the microshear test was done. CMicroleakage test: 54 discs were divided into 3 groups (n=18). Then the porcelain surfaces were etched and bonded to composite with unfilled resin and finally observed under stereomicroscope. The data were analyzed with one-way ANOVA and Smirnov tests. Results: SEM ana...

This study evaluated the effect of Zircos-E etching as a surface treatment on the monotonic and fatigue strength of 4 mol% yttria-stabilized zirconia (4YSZ), with and without resin cement. Disc-shaped specimens (n = 15 per group; Ø = 15 mm × 1.2 mm) were assigned to four surface conditions: control (no treatment), alumina air abrasion (AirAbr), Zircos-E etching for 30 min (ZE30), and for 2 h (ZE2). Each group was tested both with and without resin cement (Multilink N). Monotonic strength was measured using a biaxial flexural test, while fatigue strength was assessed via stepwise loading, beginning at 130 MPa with 30 MPa increments every 10,000 cycles. Surface roughness, topography, and fractography were also analyzed. Statistical analysis showed that surface treatment significantly influenced fatigue strength (p < 0.001), especially in cemented groups. After cementation, the AirAbr (768.2 ± 174.1 MPa) and ZE2 (757.4 ± 155.1 MPa) groups exhibited the highest fatigue strength, while the untreated control group had the lowest values (519.4 ± 88.7 MPa). Monotonic strength was significantly improved by air abrasion (894.2 ± 153.1 MPa), while Zircos-E produced intermediate results. In terms of surface roughness, ZE2 presented the highest Ra (0.99 ± 0.13 μm) and Rz values, significantly higher than the control (Ra = 0.45 ± 0.07 μm), confirming enhanced micro-retentive topography. Zircos-E etching, particularly for 2 h, effectively improved fatigue performance and roughness of 4YSZ ceramics, with outcomes comparable to conventional air abrasion. Clinical significance: Zircos-E treatment may offer a promising surface conditioning strategy for zirconia restorations, providing improved mechanical performance, particularly when combined with resin cement.

Experiments aimed at recovering soft-x-ray projection lithography mirrors that have defective reflective coatings by stripping and redeposition of Mo/Si multilayers are being reported. Two wet etchants were found that would remove the multilayers from composite glass substrates. One etchant is a solution of potassium ferricyanide and sodium hydroxide in water; the other is nitric acid with a minute quantity of hydrofluoric acid. Although each of these solutions offers preferential etch selection of the multilayers over the substrate glass, the selectivities are insufficient. The result is a surface roughening that lowers the reflectance from subsequently deposited multilayer coatings to an unacceptable level. With the addition of a carbon barrier layer between the substrate and the multilayer coating, either etchant can be used to strip the multilayers without damage to the underlying substrate surface.

Mucin from xenografts of LS174T human colon cancer cells was treated with anhydrous HF for 1 h at 0 degree C to give a product (HFA) with over 80% of the glucosamine and hexose removed, but retaining some galactosamine, and for 3 h at room temperature to give a product (HFB) devoid of carbohydrate. Rabbit antibodies against HFA bound to HFA much more than to HFB, and bound to native mucin to an intermediate extent. Antibodies to HFB bound to HFB more than to HFA, and did not bind to native mucin. Both HFA and native mucin bound a number of lectins, but HFB did not. By SDS/polyacrylamide-gel electrophoresis and size-exclusion h.p.l.c., native mucin and HFA are of apparent molecular mass greater than 400 kDa, whereas HFB is heterogeneous and of low molecular mass. On Western blots, antibody to HFA detected both high-molecular-mass mucin and a 90 kDa protein in homogenates of LS174T cells. Antibody to HFB detected a major 70 kDa band as well as higher-molecular-mass species. In tissue ...

Titanium samples of different roughness R a and morphology were prepared using a combination of mechanical (grinding with a SiC paper or blasting with aluminum oxide particles with 65 or 250 mm) and chemical (attack with a sulphuric acid based solution or a hydro¯uoric acid based solution) treatments. The biological performance of the prepared surfaces was evaluated using human bone marrow osteoblastic cell cultures. Mechanically treated samples presented different R a values and surface morphology. The hydro¯uoric acid solution was more effective than the sulphuric acid solution in smoothing titanium surface and also in eliminating aluminum contamination resulting from the blasting process. Bone marrow cells seeded on the different titanium samples showed a similar pattern of behavior during cell attachment and spreading. Cells proliferated very well on all the titanium surfaces and cell growth was observed during approximately two to three weeks. The samples treated with the hydro¯uoric acid solution presented higher alkaline phosphatase activity. Only the blasted samples treated with the acid solutions allowed seeded bone marrow cells to form a mineralized extracellular matrix. The best biological performance was found in the blasted samples treated with the hydro¯uoric acid solution, which could be related to the characteristic microtopography of these samples that presented a homogeneous and smooth roughness.

Aim: The purpose of this study is to investigate the effect of changes in hybrid ceramics to resin cement after the application of different surface treatments. Material and Method: In our work, 330 pieces of 3 different hybrid CAD-CAM ceramics were used. The ceramics were divided into 5 subgroups and their surfaces were treated differently. These were set as bonding with hydrofluoric acid, bonding with CoJet, Silane application with hydrofluoric acid, only bonding application, and control group. The shear bond strength was measured with a universal tester, INSTRON. Values from the measurements were analyzed by one-way ANOVA and the Tukey HSD test was used to determine significant differences (p = 0,05). Results: Bonding values between CAD/CAM hybrid ceramic blocks subjected to the same surface treatment were statistically significant in all HF applied samples. (p&lt;0,05) The highest bonding values were observed in HF + silane samples (52,24 ± 7,4 MPa) in the Vita Enamic group and ...

Objective. To assess the effect of mould and glass casting temperatures on the biaxial flexural strength (BFS) of two different types of castable glass-ceramic, using existing laboratory equipment and techniques. Methods. Two castable glass-ceramic materials were evaluated. One glass (LG3) is based on SiO 2 -Al 2 O 3 -P 2 O 5 -CaO-CaF 2 , and is similar in composition to glasses used in the manufacture of glassionomer cements. The other glass (SG3) is based on SiO 2 -K 2 O-Na 2 O-CaO-CaF 2 , and is a canasite-based material. Both materials were used to produce discs of 12 mm diameter and 2 mm thickness using the same lost-wax casting process as used for metal castings. Mould temperatures of between 500ЊC and 1000ЊC and glass casting temperatures of between 1100ЊC and 1450ЊC were evaluated. The cast discs were cerammed and the biaxial flexural strength determined with a Lloyd 2000 R tester. Results. A significant difference was found for the BFS in the range of mould temperatures evaluated, with the optimum investment mould temperature being 590ЊC for LG3 and 610ЊC for SG3 (p = 0.0002 and p = 0.019, respectively). No significant differences were seen between any of the glass casting temperatures evaluated. Significance. The mould temperature for castable glass-ceramic materials produced using the lost-wax casting process can have a significant effect on BFS. The optimum mould temperature may differ slightly depending on the type of material being used. The glass casting temperature of these materials does not appear to have a significant effect on BFS.

Reactions in the system Cr -NH 3 OHF -HF -H 2 O were investigated. Green crystals of a new compound with the formula (NH 3 OH) 3 CrF 6 have been isolated from the water solution and characterized by chemical analysis. The compound crystallizes as triclinic, P-1, with cell parameters: a = 6.5461(2) Å, b = 6.9347(2) Å, c = 9.4072(3) Å, α = 86.772(1)°, β = 83.804(1)°, γ = 70.283(1)°. The effective magnetic moment, µ eff = 3.82 BM, was calculated from magnetic susceptibility measurements in the temperature range 80-290 K. The thermal decomposition of the compound was studied by TG and DSC analysis. (NH 3 OH) 3 CrF 6 decomposes above 125 °C in three steps and the residue has been identified by X-ray powder diffraction as α -Cr 2 O 3 .

The objective of this study was to evaluate the effect of passive or active phosphoric acid (PA) application after hydrofluoric acid (HA) treatment on the microshear bond strength of lithium disilicate. Thirty ceramic discs were made with IPS Emax 2 (10 mm thick and 10 mm diameter). The specimens were divided into 3 groups, A: 9.6% HA application; AF: 9.6% HA application + cleaning with 37% PA in passive mode and AFF: 9.6% HA application + cleaning with 37% PA in active mode. For the microshear test, four tygons (0.9 mm diameter and 0.2 mm high) were filled with resin cement (RelyX Ultimate) and placed on the ceramic disks. After testing, the fracture modes were examined under scanning electron microscopy. Data were analyzed by one-way ANOVA and Tukey&#39;s post test (α=0.05). The bond strength values were significantly higher in Group AFF (11.0±2.5 MPa) compared with group A (8.1±2.6 MPa) (p&lt;0.002). AF group was not statistically different (9.4±2.5 MPa) from Group A. It was conc...