Hydrofluoric Acid Concentration Research Articles

Research on the process and mechanism of preparing titanium-rich materials from complex ilmenite

A new process for the development and utilization of titanium-iron sand ore from Yunnan province is proposed. We provide a detailed analysis of the chemical composition and mineral structure of the raw material, and describe a pretreatment involving low-temperature oxidation and reduction, hydrofluoric acidolysis, and hydrochloric acid leaching to remove impurities and generate titanium-rich materials. Hydrofluoric acid was used to break down the complex titanite, silica-titanium, and calcium-titanium mixture in the starting mineral into simple oxides. The results have indicated that the thermal reduction process should not be conducted at elevated temperatures. Optimal process conditions are established for the leaching process: leaching temperature of 80 °C; leaching time of 240 min; hydrofluoric acid concentration of 3%; liquid–solid ratio of 6 m l/g. Under these conditions, the extent of TFe leaching reached 96%, while the leaching of Ca and Mg reached 94%. The TiO2 grade of the final titanium-rich material was 89.95%, with a CaO content of 0.39%, a MgO content of 0.15%, and a TFe content of 7.5%. This material can serve as raw material for subsequent chlorination.

Coal quality enhancement by using bio extracts of carissa carandas fruits in combination with Hydro Fluoric acid

ABSTRACT This paper addresses the imperative need for environmentally sustainable beneficiation technologies tailored for low-rank coals, constituting about 50% of global coal deposits. The focus is on recent advancements in bio-beneficiation methods for sub-bituminous coals in thermal power stations, employing ”bio extract of Carissa carandas fruits” with lower concentrations of Hydrofluoric acid. The objective is to enhance coal quality by reducing ash content and adjusting mineral composition to mitigate clinker formation during combustion. The research investigates simultaneous coal treatment with bio extract and low-concentration Hydrofluoric acid. While traditional beneficiation techniques, such as physical, chemical, and physicochemical methods, have been extensively used, a research gap is identified in green methods utilizing biomaterial extracts to remove/reduce metal oxides from coal and the need to regulate the silica-to-alumina ratio in coal composition, for resolving the issue of clinker formation. The investigation demonstrates the bio extract’s efficacy in leaching alumina, iron oxide, and alkali/alkaline earth metal oxides from coal, significantly reducing ash content. Consequently, there is a remarkable increase in coal’s gross calorific value post bio-beneficiation, accompanied by a significant reduction in sulfur content in addition to the decrease in tendency of clinker formation of coal during combustion. This study is a significant contribution to the field of environmentally friendly coal beneficiation and to reduce the tendency of clinker formation during combustion.

First-principles study of MXene properties with varying hydrofluoric acid concentration

With varying hydrofluoric acid (HF) concentrations under three etching conditions, we presented a comparative study of the effects of both the ordered and randomly ternary mixed terminated Ti3C2Tx surfaces with a wide variation of O/OH/F stoichiometry on the thermodynamic stability and electronic properties. Regardless of the HF concentration, an OH-rich surface is found to be thermodynamically stable and the electrical conductivity of Ti3C2Tx is substantially affected by the OH concentration. The charge density difference and electron localization function demonstrated a significant electron localization at the hydroxyl group on the O/OH/F mixed terminated surface, which could yield a locally induced dipole on the surface that renders favorable reaction sites on the functionalized surface. In addition, a large tunability in the work function (ΔΦ ∼ 3.5 eV) is predicted for Ti3C2Tx. These findings provide a pathway for strategically tuning the electronic and structural properties of Ti3C2 MXenes etched with HF.

Effect of hydrofluoric acid concentration and aging on the bond strength ceramics to a resin cement.

This study evaluated the influence of hydrofluoric acid (HF) concentration and thermal cycling on the microshear bond strength (µSBS) of a resin luting agent to IPS e.max® CAD and Rosetta® SM. Ceramic specimens (12.0 x 14.0 x 1.5mm) were randomized into 8 groups (n=10) according to HF concentration, commercial brand, and aging. Immediately after polishing, and etching, all specimens were silanized and a layer of adhesive was applied. A PVS mold of 3 mm thickness and 10mm diameter with (four) 1.0mm holes was fabricated, placed on each specimen, and then filled with a resin luting agent. Half of the specimens were subjected to the µSBS test using an Instron at a speed of 1.0 mm/min, following a 24-hour storage in deionized water at 37ºC. The remaining specimens were subjected to thermal cycling (5ºC-55ºC, 30 seconds per bath) and µSBS. The data were evaluated utilizing a three-way ANOVA and Tukey's post-hoc test (α=0.05). Significant differences were found for HF concentration and aging (p<0.0001). No significant difference in µSBS was found for commercial brands (p=0.085). The interaction between brand and HF concentration (p=0.358), brand and aging (p=0.135), and HF concentration and aging (p=0.138) were not statistically significant. The triple interaction among these factors was not statistically significant (p=0.610). In conclusion, the bond strength is affected by the HF concentration. No statistical difference was observed between the two ceramics. Thermal cycling significantly reduced µSBS.

Use of composites to control bottomhole zones at high reservoir temperatures

It is found that one of the ways to increase the depth of penetration, as well as to prevent the formation of sediments, is the use of systems that contribute to the generating formation of hydrofluoric acid in reservoirs due to the ability to maintain a limited concentration of hydrofluoric acid over time. It is shown that the method of generating formation of hydrofluoric acid based on chelate compounds and ammonium hydrofluoride is a simultaneous solution to the problems associated with high temperature and the formation of secondary precipitates. Due to the strong properties of chelate compounds, some of them, which are adsorbed on the surface of the formation of the bottomhole zone, play the role of an inhibitor of salt deposition and protect the bottomhole zone from contamination with inorganic salts for a long time.

Comparison of self-etching and conventional bifunctional coupling agent in lithium disilicate ceramic: A systematic review and meta-analysis.

The aim of this systematic review is to determine the effectiveness of self-etching primers in comparison to the conventional protocol with hydrofluoric acid and silane treatment for bonding lithium disilicate ceramics. The formulated PICO question for this research was: "Does self-etching silane primer surface treatment in lithium disilicate ceramics present a similar bond strength value compared to conventional hydrofluoric acid and silane treatment?". Combinations of words and appropriate truncations were adapted for each database. For the selection, duplicate articles were systematically eliminated using Mendeley software. The Cohen's Kappa statistic was then computed, RoBDEMAT questions were addressed, and the meta-analyses were conducted using RevMan 5.4, at a significance level of 5%. Two independent reviewers conducted a blind and independent analysis of 190219 articles from PubMed, Scopus, Web of Science, and OpenGrey. Subsequently, they extracted data from 21 studies for the systematic review and in 16 the meta-analysis. In all in vitro studies, the most frequently cited concentration of hydrofluoric acid was 5%. In the meta-analysis, no statistical differences were observed between the two treatments concerning bond strength. Self-etching silane primers demonstrate promising results in lithium disilicate bonding, suggesting their potential as an alternative surface treatment to hydrofluoric acids + silane. Key words:Lithium disilicate, Hydrofluoric acid, Dental Porcelain, Ceramics, Silanes.

Targeting Oxide Concentration in Tantalum Oxide-Fluoride Anions

The design of both molecular and non-molecular solid materials with specific properties fundamentally relies on the controlled synthesis of crystals with desired functional groups, bonding motifs, polarity, chirality, and more. To this end, fluoride and oxide-fluoride anions have been utilized as basic building units (BBUs) in the synthesis of noncentrosymmetric racemic materials for their ability to create polar axes that facilitate the breaking of an inversion center as demonstrated in a series of compounds with [MF6]2- anions (M = Ti, Zr, Hf). Targeting an analog with a [TaOF5]2- anion, the phase space of (CuO, Ta2O5)/bpy/HF(aq)/H2O (bpy = 2,2′-bipyridine) was investigated and three new compounds with Cu-bpy cations and Ta-fluoride or Ta-oxyfluoride anions were synthesized: [Cu(bpy)2][TaF6], [Cu(bpy)2][Ta2OF10], and [Cu(bpy)F(H2O)2]2[TaF7]∙H2O with the anions [TaF6]-, [Ta2OF10]2-, and [TaF7]2-, respectively. The formation of these anions was found to be a product of both the concentration of hydrofluoric acid in solution and the ratio of metal-oxide starting materials to ligand. This work contributes to the understanding of mixed anion formation in the solid state.

Effect of Hydrofluoric Acid Concentration on Bond Strength to Glass-Ceramics: A Systematic Review and Meta-Analysis of In-Vitro Studies.

To conduct a systematic review and meta-analysis of in-vitro bond strength to glass-ceramics using hydrofluoric acid (HF) at lower (<5%) and higher (>5%) concentrations ([HF]) to treat ceramic surfaces. Systematic searches were carried out in PubMed, Scopus, LILACS, and Web of Science for articles published through July 2021, and a meta-analysis was performed to estimate the combined effect by comparing the differences between the standardized means of the bond strengths of the evaluated materials. In total, 943 articles were found, of which 17 studies were selected for qualitative analysis and 12 for quantitative analysis. The bond strength to glass-ceramics using 4% to 5% HF did not differ from that using 7% to 10% HF for the following HF etching times and glass-ceramic materials: 20 s for lithium-disilicate (Z = 0.65, p = 0.51), 60 s for feldspathic (Z = 0.53, p = 0.60), and 60 s for leucite (Z = 0.72, p = 0.35). The lower concentration HF (<5%) etchant is a reliable surface treatment for adhesive bonding to glass-ceramics with satisfactory bond strength in short-term evaluations.

Effects of Hydrofluoric Acid Concentrations, Commercial Brands, and Adhesive Application on the Bond Strength of a Resin Luting Agent to Lithium Disilicate Glass Ceramic.

To evaluate the surface topography/roughness and bond strength of a resin luting agent to a lithium disilicate glass ceramic after etching with different concentrations of hydrofluoric acid (HF) and commercial brands. For bond strength evaluation, 260 lithium disilicate glass ceramic (EMX) discs were randomly distributed into 13 groups based on concentrations of HF and commercial brands (n=20): 5% and 10%, Lysanda (LY5 and LY10); 5% and 10%, Maquira (MA5 and MA10); 5% and 10%, FGM (FG5 and FG10); 4.8%, Ivoclar Vivadent (IV5); 5% and 10%, PHS do Brasil (PH5 and PH10); 5% and 10%, BM4 (BM5 and BM10); 9%, Ultradent Inc (UL10); and Dentsply (DE10). A further random distribution (n=10) was made based on the application (+) or absence (-) of an adhesive layer. Resin luting agent cylinders (1 mm in diameter) were added on EMX surfaces, light-cured, and stored for 24 hours in deionized water at 37°C. On a universal testing machine (DL 500, EMIC), specimens were submitted to a microshear bond strength test at a crosshead speed of 1 mm/min until failure. A representative etched EMX disc from each group underwent surface topography analysis using field-emission scanning electron microscopy (n=1), and five (n=5) etched EMX discs from each group were tested for surface roughness. Data were statistically analyzed using analysis of variance and Tukey test (α=0.05). A less conditioned and smoother surface was observed for 5% HF compared to 10%. Additionally, commercial brands of HF were shown to affect bond strength. When the adhesive layer was not used (-), a 10% concentration promoted higher bond strengths to EMX. However, when adhesive was applied (+), the concentrations of HF and commercial brands had no effect on bond strength results. A 10% concentration of HF results in higher bond strength than a 5% concentration. If an adhesive layer is applied, neither this distinction nor the influence of commercial brands is observed.

Hydrofluoric acid concentration and etching time affect differently the microstructure and surface properties of pressed lithium disilicate glass ceramics.

To evaluate the effect of different hydrofluoric acid concentrations and etching times on the surface, chemical composition and microstructure of lithium disilicate. Ninety specimens of pressed lithium disilicate (LDS) were obtained (IPS e.max Press, Rosetta SP and LiSi Press). The specimens of each material were divided in two groups according to the hydrofluoric acid concentration: 5% and 10% (n = 15/group), and subdivided according to the etching time: 20, 40 and 60 s (n = 5/group). Crystalline evaluations and chemical composition were performed through x-ray diffraction (XRD) and energy-dispersive x-ray spectroscopy (EDS), respectively. Microstructural analyses were performed by scanning electron microscope (SEM), surface roughness (Ra), and material thickness removal evaluation. Thickness removal and Ra data were analyzed by ANOVA and Tukey test (p < 0.05). XRD demonstrated characteristic peaks of lithium disilicate crystals, lithium phosphate and of a vitreous phase for all materials. EDS identified different compositions and SEM confirmed different surface responses to acid etching protocols. Material and etching time influenced Ra and material thickness removal (p < 0.05). Hydrofluoric acid concentration and etching time affect the surface characteristics of LDS differently. LiSi Press presented higher resistance to hydrofluoric acid etching compared to e.max Press and Rosetta SP. Applying the appropriate etching protocol is pivotal to avoid excessive material removal and to prevent jeopardize the mechanical and optical properties of the material.

Study the Effect of Hydrofluoric (HF) Concentration on the Topography of the Porous Silicon Layer Prepared by Sunlight Photochemical Etching (SLPCE)

Silicon nanocrystals have a vast range of potential applications, from improving the efficiency of solar cells and optoelectronic devices to biomedical imaging and drug delivery, wastewater treatment, and antibacterial activities. In this study a photochemical etching technique was used to create layers of porous silicon on a donor silicon wafer with orientation (111) and resistivity equal to 1‑10 ohm·cm. The process involved focusing sunlight onto the samples using a telephoto lens with a suitable focal length of 30cm and a diameter of 90 mm, which provided sufficient energy to complete the chemical etching. By using a constant etching time of 60 minutes and different concentrations of hydrofluoric acid (ranging from 25% to 40%), layers with varying properties were obtained. The resulting surfaces were studied using the atomic force microscope (AFM), revealing the formation of different nanostructures and particles with varying shapes, sizes, and thicknesses depending on the preparation conditions. The average size of the particles was found to be 90.43nm at a concentration of 40% acid, while decreasing to 48.7nm at a concentration of 25% HF acid.

Simulation of the influences of different minerals contained in acidified coal on CH4 adsorption

To reveal the microscopic mechanism of CH4 adsorption by the main minerals in acidified coal, the depth of acid ion intrusion, the amount of CH4 adsorbed using isothermal adsorption experiments, and heat of adsorption were simulated by Grand Canonical Monte Carlo (GCMC) method for the composite molecular model composed of kaolinite, calcite, dolomite, and quartz with coal, respectively. The results show that the depth of acid ion intrusion directly affects the amount of methane adsorption. At pressures of 0–8 MPa, the F− intrusion depth directly affected the CH4 adsorption of the composite model of coal–kaolinite (quartz); the depths of Cl− and CH3COO− intrusion directly affected the methane adsorption of the composite model of coal–dolomite; the mixed acid containing Cl− and CH3COO− had the greatest effect on promoting methane adsorption. When acidifying the coal–calcite (quartz) compound structure, Cl− and CH3COO− increased the depth of F− intrusion, and the increase caused by CH3COO− was greater than that of Cl−. After acidification of the coal–calcite composite, the relationship between methane adsorption and heat of adsorption gradually changed from negative to positive with the increase of the hydrofluoric acid (HF) concentration; after acidification of composites of coal and other minerals, CH4 adsorption and heat of adsorption were positively correlated. The amount of CH4 adsorption after coal–kaolinite and coal–quartz acidification exceeded that of coal–calcite and coal–dolomite, mainly because the acidification of dolomite and calcite would generate CO2 to compete with CH4 for adsorption.

Kinetics and spectroscopic characterization of silica nanoparticles formed while etching quartz in hydrofluoric acid

The kinetic regularities of the silica nanoparticles formed during the quartz etching in hydrofluoric acid were explored for the first time. The main drivers for nanoparticle formation, as well as for the etching reaction of quartz, are the concentration of hydrofluoric acid and the ratio of the solid surface area to the liquid volume. Kinetic factors combined with nanoparticle interaction and agglomeration lead to kinetic changes of their concentrations. The proportion of nanoparticles in the weight balance with the dissolved solids decreases significantly and remains in the 0.03% range during quartz etching. XPS analysis of nanoparticles identified elements of Si, O, and F in chemical states such as Si–O, Si-Ox, SiO2, and F–Si. FT-IR reflection also identified the stretching and bending vibration peaks of the Si–O–Si and O–H. The wide fluorescence peak with a maximum at ∼633–650 nm matches the spectrums of known non-bridging oxygen centers ≡Si–O∙. The UV absorption band with maximum in the range of 195–197 nm, detected for nanoparticle samples in liquid, belongs to the silica E’ defect centers ≡Si. In some spots of the deposited nanoparticles Raman peaks are recorded, which is typical for crystal forms of silica. Using AFM, 3D images of nanoparticles deposited on silicon or glass wafers reveal the grain size range of the particles and the feedback between the morphology of the deposited layers and the surface hydrophilicity. The high stability of the quartz etching nanoparticles in hydrofluoric acid explained their structural specificity because they have a surface fluorinated layer consisting of Si–F bonds around the silica grains. The lack of known molybdate-reactive silica inspection methods for the analysis of etching nanoparticles is disclosed. On the basis of the experimental data, new approaches are proposed for the cleaning of quartz parts from particles and for operative inspection of cleanliness.Silica, nanoparticles, etching, quartz, fluorescence, FT-IR, XPS, NP-ICP-MS.

Experimental Investigation on Physicochemical and Wetting Characteristics of Modified Gas Coal: Effects of Multicomponent Acids and Surfactant

Abstract In this study, the effects of the different concentrations of hydrochloric acid, hydrofluoric acid, and acetic acid and a surfactant on the physicochemical characteristics of coal, such as pore diameter distribution, pore fractal dimension, and chemical structures were studied. The wettability performance of the reagent-modified coal was proposed. The results demonstrated that the mineral dissolution rate of HF in the coal sample was much higher than those by HCl and HAC treatment, which increases the surface roughness of coal. With the increase in the concentration of a multicomponent acid solution, the number of micropores decreased and the number of macropores increased. Moreover, both fractal dimensions D1 and D2 of the coal sample treated with the multicomponent acid comprising 6% HCl, 6% HF, and 6% HAC (#3) were the smallest. This shows that compound reagent #3 is available to enhance the pore size distribution with a better effect than the other five ones. Compared with the raw coal (#7), treatment with high concentrations of HCl (#4) significantly decreased the contact angle on coal (#4), whereas treatment with high concentrations of HF or HAC (#6 or #5), significantly increased it.

Identification of Key Events and Emissions during Thermal Abuse Testing on NCA 18650 Cells

Thermal abuse of lithium-ion batteries (LIBs) leads to the emission of gases, solids, fires and/or explosions. Therefore, it is essential to define the temperatures at which key events occur (i.e., CID activation, venting, and thermal runaway (TR)) and to identify the related emissions for identifying the hazards to which people and especially rescue teams are exposed. For this purpose, thermal abuse tests were performed on commercial lithium nickel cobalt aluminum oxide (NCA) 18650 cells at 50% state of charge in a reactor connected to an FT-IR spectrometer by varying test conditions (feed gas of N2 or air; heating rates of 5 or 10 °C/min until 300 °C). In particular, the concentrations of the gases and the composition of the condensed-phase emissions were estimated. As regards gases, a high concentration (1695 ppmv) of hydrofluoric acid (HF) was measured, while the emissions of condensed matter consisted of organic compounds such as polyethylene oxide and paraffin oil, and inorganic compounds containing Li (0.173 mg/m3) and Al (0.344 mg/m3). The main safety concerns were caused by the temperatures (564 ± 85 °C) reached by the cell during TR, by the HF concentration which exceeded the toxicity limits of 30 ppm, the IDLH defined by the NIOSH, and the diameter of the particles (1.54 ± 0.69 µm) that rose the PM2.5 concentration. These results are also useful for identifying personal protection equipment for rescue teams.

Concentration of hydrofluoric acid during processing columbite and loparite concentrates

The results of modeling the concentration of hydrofluoric acid on the example of processing columbite and loparite concentrates are presented. It is shown that when optimizing the rectification process, it is necessary to use the electrolyte NRTL vapor-liquid equilibrium model and use the total energy consumption going to the separation of the mixture as an optimization criterion. The information about the work on the extraction of anhydrous hydrogen fluoride from hydrofluoric acid is presented.

Research on composite manufacturing method of semi-buried 1×32 optical splitter

In this paper, a composite manufacturing method was proposed to reduce the inner surface roughness of silica groove. Firstly, femtosecond laser was used to ablate the silica groove, then, a 5% concentration hydrofluoric acid solution was used to corrode the inner surface of silica groove. Secondly, Su8 adhesive was filled with the groove to form a semi-buried 1×32 optical splitter by doctor blade. The test results showed that the surface roughness Ra was less than 0.2 µm, and average insertion loss of output ports was 21.34 dB, moreover, the uniformity was less than 1.44 dB. Compared with the traditional femtosecond laser ablating method, surface roughness reduced by at least 0.1 µm, and the average insertion loss of output ports was reduced by 1.22 dB, and the uniformity was reduced by 0.41 dB. So, the composite manufacturing method improved the communication performance. It is satisfied with the requirements for optical interconnection in the electro-optical printed circuit boards.

Treatment of Spent Pickling Solutions by Diffusion Dialysis Using Anion-Exchange Membrane Neosepta-AFN.

This article presents the possibility of using diffusion dialysis for processing spent pickling solution from pickling stainless steels with a mixture of nitric acid and hydrofluoric acid. A counter-current two-compartment dialyzer equipped with an anion-exchange membrane Neosepta-AFN was used to study and compare the diffusion dialysis of model mixture of hydrofluoric acid and ferric nitrate and a real spent pickling solution. The separation efficiency was characterized by the acid recovery yield, the rejection coefficient of the metals, the permeability coefficient of the membrane, and the separation factor. These characteristics were calculated from the data obtained at steady state. For the real spent pickling solution tested, the permeability values of nitrates 1.7 × 10-6 m s-1, fluorides 0.4 × 10-6 m s-1, and ferric ions 1.1 × 10-7 m s-1 were achieved. The separation factor for nitrates/ferric ions was 15.7 and 3.6 for fluorides/ferric ions. Furthermore, the dependencies of recovery yield and rejection for different concentrations of hydrofluoric acid and ferric nitrate were determined.

Acid dissolution of ultrathin glass-ceramic and its correlation with flexural strength

Statement of problemWhen glass-ceramics are treated with hydrofluoric acid (HF), not only the area of application is affected but also other surfaces. Information regarding the correlation of the dissolution caused by HF and the flexural strength of the ceramic is lacking. PurposeThe purpose of this in vitro study was to investigate the effect of HF etching protocols on the flexural strength of 2 glass-ceramics, the correlation of their flexural strength with the internal and lateral dissolution, and the differences in Weibull characteristics concerning the etching protocols. Material and methodsSpecimens (4×12×0.3mm) of leucite-reinforced glass-ceramic—LEU (IPS Empress) and of lithium disilicate-reinforced glass-ceramic—LD (IPS e.max) were prepared. The specimens were divided into 5 groups (n=12) according to etching protocol: control—untreated; hydrofluoric acid (HF) 5% for 20 seconds (HF5%20s); HF5%60s; HF10%20s; and HF10%60s. Flexural strength was evaluated through 3-point bend testing. The fractured specimens were submitted to a morphological and metrical analysis of each pattern (LEU I–IV, LD I–III) on the lateral surface (LS) and of the dissolution areas (μm2) on the internal surface (IS) using a scanning electron microscopy (SEM) and a software program (FIJI). Flexural strength (MPa) values were analyzed by 1-way ANOVA, Bonferroni test, and Weibull and the correlation between flexural strength and dissolution by Pearson correlation coefficient (α=.05). ResultsANOVA revealed that the HF etching protocol was significant (P<.001) for LEU ceramic. When HF10%60s was applied, LEU showed Weibull characteristic strength (σθ) values lower than those of the other protocols. LD showed no difference in σθ and reliability (m) among the groups. The internal dissolution areas concerning LEU had a significant high negative correlation with the flexural strength (r=-0.6; P<.001). LEU-IV on the LS was the only pattern to show a significant decrease in flexural strength (r=-0.3, P<.05). ConclusionsSpecial care should be taken when applying hydrofluoric acid on glass-ceramic restorations. Protocols with higher hydrofluoric acid concentrations and longer application times were more related to greater internal areas of dissolution which reduced the flexural strength of leucite ceramics.

Tailoring surface structure and diameter of etched fiber Bragg grating for high strain sensing

Sensitivity and mechanical properties are the key factors that affect the performance of strain-sensitive etched fiber Bragg grating (EFBG) sensors. Typically, EFBG sensors are fabricated via solvent etching. The manipulation of etching temperature and hydrofluoric acid (HF) concentration during the solvent etching process is particularly crucial to control the surface and mechanical properties of the sensors. In this study, the effects of these two etching conditions on the surface and mechanical properties of the etched fiber surface were investigated. It is found that higher etching temperature and higher HF concentration can cause rougher fiber surface with lower Young’s modulus, fracture stress and strain. EFBG produced at 20 °C temperature and 30% HF concentration exhibits smooth surface and high mechanical properties. Under these optimized etching conditions, the sensitivity of EFBGs was improved by reducing the fiber diameter. The results show that EFBGs with smaller diameters demonstrate higher strain sensing performance due to lower fiber stiffness. EFBG with a diameter of 15 μm has Young modulus of 7.21 GPa and achieves the highest strain sensitivity of 52.74 pm/με. To conclude, EFBG with excellent strain sensing performance can be obtained by tailoring the surface structures and fiber’s diameter during the etching process.