Showing papers on "Hydrofluoric acid published in 2023"

Hydrofluoric Acid‐Removable Additive Optimizing Electrode Electrolyte Interphases with Li+ Conductive Moieties for 4.5 V Lithium Metal Batteries

Abstract: High‐voltage lithium metal batteries (LMBs) are capable to achieve the increasing energy density. However, their cycling life is seriously affected by unstable electrolyte/electrode interfaces and capacity instability at high voltage. Herein, a hydrofluoric acid (HF)‐removable additive is proposed to optimize electrode electrolyte interphases for addressing the above issues. N, N‐dimethyl‐4‐(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl) aniline (DMPATMB) is used as the electrolyte additive to induce PF6− decomposition to form a dense and robust LiF‐rich solid electrolyte interphase (SEI) for suppressing Li dendrite growth. Moreover, DMPATMB can help to form highly Li+ conductive Li3N and LiBO2, which can boost the Li+ transport across SEI and cathode electrolyte interphase (CEI). In addition, DMPATMB can scavenge traced HF in the electrolyte to protect both SEI and CEI from the corrosion. As expected, 4.5 V Li|| LiNi0.6Co0.2Mn0.2O2 batteries with such electrolyte deliver 145 mAh g−1 after 140 cycles at 200 mA g−1. This work provides a novel insight into high‐voltage electrolyte additives for LMBs.

Step-by-Step Guide for Synthesis and Delamination of Ti3 C2 Tx MXene.

Abstract: 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 (Ti3 C2 Tx ) MXene using a mixture of hydrofluoric and hydrochloric acids for the selective etching of the stoichimetric-Ti3 AlC2 MAX phase and delamination of the etched multilayered Ti3 C2 Tx 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 Ti3 AlC2 , 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 scanning electron microscopy, x-ray diffraction, atomic force microscopy, and ellipsometry. The Ti3 C2 Tx film made via the optimized method shows electrical conductivity as high as ≈21,000 S/cm with a synthesis yield of up to 38 %. A detailed protocol is also provided for the Ti3 C2 Tx MXene synthesis as the supporting information for this study.

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

Abstract: 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.

Effects of Two Different Acid Etching and Surface Washing Methods on Bond Strength on Different CAD-CAM Blocks under Aging Protocols

Abstract: Aim. The purpose of this study is to investigate the effects of hydrofluoric acid and one-component ceramic primer and silane (Monobond Etch and Prime (MEP)) applications on lithium disilicate glass ceramics and zirconium-infiltrated lithium silicate glass ceramics, as well as the effect of ultrasonic and phosphoric acid surface washing methods on bond strength. Materials and Method. A total of 240 ceramic samples were prepared using two different CAD-CAM material blocks with a thickness of 2 mm made of lithium disilicate glass-ceramic (IPS e.max CAD) and zirconium-infiltrated lithium silicate glass ceramic blocks (Celtra Duo). The samples were cemented to the composite discs (Tetric N-Ceram) after two different acid treatments, and surface washing processes were applied to them. As such, 24 groups were formed, each with two different acid applications, three different washing processes, two different CAD-CAM blocks, and two different aging procedures ( n = 10 ). Following the application of the acid, different washing processes are used. These were HF acid and washing only (HF + W), HF acid and ultrasonic washing (HF + US), HF acid and phosphoric acid (HF + PA), MEP with washing only (MEP + W), MEP and ultrasonic washing (MEP + US), and MEP and phosphoric acid (MEP + PA). The composite discs were cemented with dual cure adhesive cement (Multilink Automix) after the determined surface treatments were applied to the blocks. After surface applications, SEM analysis was conducted. Following exposure to two different thermal procedures, long-term (TL) and short-term (TS), bond strengths were measured using an Instron universal test device. SPSS version 23.0 software was used to perform the statistical analyses. Histogram graphs and the Kolmogorov-Smirnov/Shapiro-Wilk test were used to assess the variables’ conformity to the normal distribution. Results. The bond strength values of TS and TL in the Celtra Duo block were significantly higher than those in the e.max CAD block ( p < 0.05 ). The TS-TL bonding strength value difference in the e.max CAD block was significantly higher than the surface measurements in the Celtra Duo block. While the highest bond strength value HF + US for TS in e.max CAD was 20.07 ± .31 , the values of HF + US in Celtra Duo were significantly higher in terms of TL values when compared to other groups. Conclusion. Celtra Duo material demonstrated higher bond strength values after a short and long thermal cycle than e.max CAD material. In general, groups bonded with HF were less affected by the thermal cycle than groups treated with MEP.

Framework Uranyl Silicates: Crystal Chemistry and a New Route for the Synthesis

Abstract: To date, uranyl silicates are mostly represented by minerals in nature. However, their synthetic counterparts can be used as ion exchange materials. A new approach for the synthesis of framework uranyl silicates is reported. The new compounds Rb2[(UO2)2(Si8O19)](H2O)2.5 (1), (K,Rb)2[(UO2)(Si10O22)] (2), [Rb3Cl][(UO2)(Si4O10)] (3) and [Cs3Cl][(UO2)(Si4O10)] (4) were prepared at harsh conditions in “activated” silica tubes at 900 °C. The activation of silica was performed using 40% hydrofluoric acid and lead oxide. Crystal structures of new uranyl silicates were solved by direct methods and refined: 1 is orthorhombic, Cmce, a = 14.5795(2) Å, b = 14.2083(2) Å, c = 23.1412(4) Å, V = 4793.70(13) Å3, R1 = 0.023; 2 is monoclinic, C2/m, a = 23.0027(8) Å, b = 8.0983(3) Å, c = 11.9736(4) Å, β = 90.372(3) °, V = 2230.43(14) Å3, R1 = 0.034; 3 is orthorhombic, Imma, a = 15.2712(12) Å, b = 7.9647(8) Å, c = 12.4607(9) Å, V = 1515.6(2) Å3, R1 = 0.035, 4 is orthorhombic, Imma, a = 15.4148(8) Å, b = 7.9229(4) Å, c = 13.0214(7) Å, V = 1590.30(14) Å3, R1 = 0.020. Their framework crystal structures contain channels up to 11.62 × 10.54 Å filled by various alkali metals.

Step‐by‐Step Guide for Synthesis and Delamination of Ti ₃ C ₂ T <i> _x </i> MXene

Abstract: 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 (Ti3 C2 Tx ) MXene using a mixture of hydrofluoric and hydrochloric acids for the selective etching of the stoichimetric-Ti3 AlC2 MAX phase and delamination of the etched multilayered Ti3 C2 Tx 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 Ti3 AlC2 , 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 scanning electron microscopy, x-ray diffraction, atomic force microscopy, and ellipsometry. The Ti3 C2 Tx film made via the optimized method shows electrical conductivity as high as ≈21,000 S/cm with a synthesis yield of up to 38 %. A detailed protocol is also provided for the Ti3 C2 Tx MXene synthesis as the supporting information for this study.

LiF-Rich Interfaces and HF Elimination Achieved by a Multifunctional Additive Enable High-Performance Li/LiNi0.8Co0.1Mn0.1O2 Batteries.

Abstract: Li-metal batteries (LMBs), especially in combination with high-energy-density Ni-rich materials, exhibit great potential for next-generation rechargeable Li batteries. Nevertheless, poor cathode-/anode-electrolyte interfaces (CEI/SEI) and hydrofluoric acid (HF) attack pose a threat to the electrochemical and safety performances of LMBs due to aggressive chemical and electrochemical reactivities of high-Ni materials, metallic Li, and carbonate-based electrolytes with the LiPF6 salt. Herein, the carbonate electrolyte based on LiPF6 is formulated by a multifunctional electrolyte additive pentafluorophenyl trifluoroacetate (PFTF) to adapt the Li/LiNi0.8Co0.1Mn0.1O2 (NCM811) battery. It is theoretically illustrated and experimentally revealed that HF elimination and the LiF-rich CEI/SEI films are successfully achieved via the chemical and electrochemical reactions of the PFTF additive. Significantly, the LiF-rich SEI film with high electrochemical kinetics facilitates Li homogeneous deposition and prevents dendritic Li from forming and growing. Benefiting from the collaborative protection of PFTF on the interfacial modification and HF capture, the capacity ratio of the Li/NCM811 battery is boosted by 22.4%, and the cycling stability of the symmetrical Li cell is expanded over 500 h. This provided strategy is conducive to the achievement of high-performance LMBs with Ni-rich materials by optimizing the electrolyte formula.

The role of silanol groups on the reaction of SiO 2 and anhydrous hydrogen fluoride gas

Abstract: It is essential to etch SiO2 for producing silica glass components, semiconductor devices, and so on. Although wet-etching with hydrogen fluoride (HF) solutions is usually employed for this purpose, it faces a drawback that microstructures stick during the drying of the solution. To overcome this problem, we have developed a dry-etching technique with gaseous HF at high temperatures. In the present study, an interesting phenomenon was found that silicon thermal oxides were much less etched than vitreous silica by gaseous HF. Such difference had not been found in wet- or humid HF gas etching. Because their bulk chemical formulae are the same (SiO2), it was suggested that the surface species affected the reaction rate. In fact, preprocessing with water vapor plasma remarkably increased the etching rate on the thermal oxides layer, and vacuum heating almost completely suppressed the reaction on the vitreous silica and the plasma-treated thermal oxides. These results indicate that the surface silanol groups enhance the reaction between SiO2 and gaseous HF. Based on the results, a model of chain reaction for SiO2 and gaseous HF was proposed, where the surface silanol groups act as the reaction center.

Optimum criteria of using Er:YAG laser in roughening PICN surface: a pilot in-vitro study

Abstract: The purpose of this study was to evaluate the efficiency of Er:YAG laser irritation on the roughness (Ra) value of Enamic surface (PICN) at different energy settings, and determine the optimal energy setting for a successful pre-treatment.The study included 5 experimental groups (N.=8), including group A, untreated group (control); surface roughness of this group was measured with surface roughness tester (profilometer), then a total number of 32 PICN discs were randomly divided into 4 groups according to the treatment conducted, group B, hydrofluoric acid-etched (HF); group C, D, E in order (150, 250, 400 mJ Er:YAG laser-irritated); and roughness was measured by the same method applied to control group. Data were collected in microns (μm) and analyzed using one-way ANOVA and post hoc comparison tests (a=0.05).All of the treatments improved surface roughness because a significant difference was observed between group A and all other groups P<0.05, the highest mean roughness value was in group B and E, followed by group C and D. The post hoc test showed there was no statistical difference found between groups B and E.In terms of surface roughening, a conclusion can be made that irritating PICN inner surface with 400w Er:YAG can be an alternative pretreatment method to hydrofluoric acid.

Etching peculiarities in sapphire induced by double-pulse irradiation with variable delay and crossed polarisation

Abstract: This manuscript presents the results of the intra-volume modifications and etching peculiarities of bulk crystalline sapphire (α-AL2O3) induced by double-pulse femtosecond laser radiation with a variable delay between pulses. The selective etching of sapphire was tested using various combinations of double-pulse irradiation. It was demonstrated that by varying the inter-pulse delay from −10 ps to 10 ps, the enhanced etching rate of the sapphire microchannels could be achieved compared to the single-pulse processing. It was demonstrated that there is an asymmetrical etching behaviour versus inter-pulse delay, depending on what polarisation of the first pulse relative to the scan direction is, (positive and negative pulse delays) when etching only in hydrofluoric acid (HF). In order to etch the entire structure, a combination of HF and a solution of H3PO4: H2SO4 (3:1) was used. The isotropic etching properties of H3PO4: H2SO4 made it possible to release items from the crystalline portion of the sapphire.

Evaluation of shear bond strength and translucency of zirconia-reinforced lithium silicate and lithium disilicate: An in vitro study

Abstract: Aim: To analyze the effect of various surface treatment protocols on shear bond strength between the ceramic and resin cement (RC) and influence of zirconia on the translucency of LD as compared to zirconia-reinforced lithium silicate (ZLS). Setting and Design: In-Vitro Study. Materials and Methods: Specimens (14 mm × 12 mm × 2 mm) (n = 135) and (14 mm × 12 mm × 1 mm) (n = 45) of ZLS computer-aided design/computer-aided manufacturing glass ceramic block and LD were fabricated, respectively. All the ZLS specimens were crystallized and were tested for the translucency parameter and ceramic-resin shear bond strength. Two different types of surface treatment were used on the ZLS and LD samples. The specimens were treated using the hydrofluoric acid (HF) etching or air abrasion with diamond particles (DPs). The specimens were then bonded using self-adhesive RC to a composite disc of 10 mm and thermocycling was performed. A universal testing machine was used to evaluate ceramic-resin shear bond strength after 24 h. The translucency of the specimens was evaluated using the spectrophotometer by calculating the difference in color between the readings over a black background and a white background. Statistical Analysis Used: Data were statistically analyzed using the independent sample t-test and analysis of variance with Bonferroni's correction and comparison was made between the specimens. Results: Independent sample t-test demonstrated statistically significantly higher translucency for group ZLS (61.44 ± 22) as compared to group LD (20.16 ± 8.39) (P < 0.001). Group ZLS showed statistically significant higher shear bond strength when surface treatment using HF or air abrasion with synthetic DPs was performed as compared to untreated group (3.58 ± 0.45) (P < 0.001). Moreover, air abrasion group (16.79 ± 2.11 megapascal [MPa]) demonstrated statistically significant higher shear bond strength as compared to HF etched group (8.25 ± 0.30 MPa) (P < 0.001). Furthermore, statistically significant higher shear bond strength was noted when air abrasion was done for group ZLS (16.79 ± 2.11 MPa) as compared to group LD (10.82 ± 1.92 MPa) (P < 0.001). However, on surface treatment with HF, a statistically significantly lower shear bond strength was noted for group ZLS (8.25 ± 0.30 MPa) as compared to group LD (11.29 ± 0.58 MPa) (P = 0.001). Conclusion: ZLS demonstrated higher translucency compared to LD restorations. DP abrasion of ZLS is recommended to achieve higher shear bond strength between the ceramic and RC.

Investigation of Factors Causing Watermark Defect on Hydrophobic Silicon Surface

Abstract: Watermark defect has been known to occur in HF (Hydrofluoric acid) last wet clean process due to the Hydrophobic nature of the exposed Silicon surface. Some water mark causing factors such as HF concentration, humidity, presence of megasonic in rinse etc. are well known to the industry. In this paper, new factors causing watermark defect on silicon surface and the recommended solutions are proposed. HF chemical bath batch life, HF dip duration and DI water rinse duration are identified as the factors that promote watermark defects. Avoiding running wafer in fresh HF chemical batch, reducing HF dip duration and DI water rinse duration are very important to prevent watermark defect on sensitive silicon surfaces.

Simultaneously Monitoring Humidity and Temperature Based on Waveguide Bragg Grating Sensor Chip

Abstract: Herein, we proposed and demonstrated a novel relative humidity (RH) sensing chip with temperature compensation, which is based on waveguide Bragg grating (WBG) assisted with polyvinyl alcohol (PVA) and polydimethylsiloxane (PDMS) composite film. Half of the cladding of the WBG region was corroded with hydrofluoric acid, which results in a split of the Bragg peak into two peaks. The PVA-PDMS composite film coated on the surface of the corroded region shows a high sensitivity to RH due to the hydrophilic hydroxyl groups of PVA film. PDMS not only enhances the stability of the composite film, but also reduces the RI of the PVA film, which restricts the energy loss of the light passing through. In our experiment, average RH sensitivities of -12.2 pm/RH% and 0 pm/RH% in the RH range of 50%-90%, and temperature sensitivities of 9.6 pm/°C and 9.8 pm/°C were obtained by the two peaks shift, respectively. We testified that the simultaneous measurement of RH and temperature can be achieved by the sensitivity matrix method. Furthermore, the proposed sensor possesses remarkable stability and excellent repeatability. Such a cost-effective, integrated, easily fabricated, and reflection power detection-based humidity sensor promises great application prospects in the fields of agriculture, food industry, biological field and other production activities.

The Impact of Different Surface Treatments on Topography and Bond Strength of Resin Cement to Lithium Disilicate Glass Ceramic

Abstract: SUMMARY Objective To evaluate the influence of different surface treatments on topography, surface roughness, surface energy, and microtensile bond strength stability of resin cement to lithium disilicate glass ceramic. Methods and Materials Seventy disc-shaped specimens of IPS e.max Press were divided into seven groups according to the surface treatment: NT – non-treated (control); FSil − hydrofluoric acid (HF) + silane; FPSil − HF + phosphoric acid (HP) + silane; FUSil − HF + ultrasonic bath (U) + silane; FPUSil − HF + HP + U + silane; MEP − Monobond Etch and Prime (MEP); and MEPH − MEP + heating. Topography and surface roughness were evaluated using a 3D laser confocal microscope (3DLCM) and scanning electron microscopy (SEM) and surface energy with a goniometer. The microtensile bond strength (μTBS) was evaluated after storage in distilled water at 37°C for 24 hours and after thermocycling (5,000 cycles, 5°–55° C, 30-second dwell time). Data were analyzed using one-way ANOVA (surface roughness and surface energy), two-way ANOVA (μTBS), Tukey′s HSD post-hoc test, and Student t-test (α=0.05). Results FUSil, FPSil, and FSil presented similar and highest surface roughness, whereas NT, FPUSil, MEP, and MEPH showed similar, and lowest, roughness values (p&lt;0.05). FPUSil, FPSil, FUSil, and FSil presented a similar and highest surface energy. NT, MEP, and MEPH showed similar and lowest surface energy. Conclusion Only FSil, FPSil, and MEPH maintained bond strength stability after thermocycling, with FPSil leading to less bond strength reduction, suggesting this protocol is more reliable for bonding resin cements to lithium disilicate glass ceramics.

Reproducible 2D Ti3C2Tx for perovskite-based photovoltaic device

Abstract: Ti3C2Tx (Tx denotes terminal group), resulting from two-dimensional (2D) Mxenes, has attracted significant attention due to energy shortage and catalysis. Herein, we present reproducible 2D Ti3C2Tx obtained from commercial bulk Ti3AlC2 using a cost-effective and environment-friendly approach. Both etching and exfoliation processes were investigated with the rational selection of etchant, reaction time and exfoliation solution. The hydrofluoric acid (HF) etchant plays a key role in the production of 2D Ti3C2Tx and therefore the recycling of HF is addressed for reproducible 2D MXenes. Hazardous HF waste was also neutralized via CaF2 precipitation according to the regulations for HF sewage. Equally important, dimethyl sulfoxide (DMSO) was employed to promote the exfoliation of multilayer Ti3C2Tx MXenes into Ti3C2Tx nanosheets in an aqueous solution, which can couple with terminal groups and protect the exfoliated single-layers from recombination, facilitating interface passivation toward perovskite solar devices. The resulting perovskite solar cell exhibited striking improvements to achieve champion efficiency, with a PCE of 19.11%, which accounts for ∼9% enhancement as compared to pristine devices.

Is Ammonium Hydrogen Difluoride a Solution for Zirconia Surface Conditioning?

Abstract: This research investigated the topographical features and phase transformation of high-translucent monolithic zirconia after different surface conditioning methods.Zirconia slabs were divided into six groups according to surface treatment method. Group I: etched with hydrofluoric acid (HF); Group II: etched with an experimental acid solution (EAS); Group III: melt-etched with ammonium hydrogen difluoride (AHD); Group IV: air abrasion (AB); Group V: etched with EAS after air abrasion (AB+EAS); Group VI: melt-etched with AHD after air abrasion (AB+AHD). Surface topographies of specimens were documented by scanning electron microscopy (SEM). Tetragonal-to-monoclinic phase transformation was detected by X-ray diffraction and surface evaluation of zirconia specimens; surface roughness and contact angle measurements were performed. The data were statistically analyzed by the Kruskal- Wallis test and post hoc tests (P⟨0.05).The acid-etched zirconia groups (Group I, II, and III) showed the lowest contact angle and surface roughness values (P⟨0.05), while the air abrasion groups (Group IV, V, VI) showed the highest. The SEM images also supported these results.Within the limitations of this in vitro study, treating the monolithic zirconia surfaces with EAS or AHD after air abrasion may be recommended to alter the zirconia surfaces.

Investigation of the Angle of Sliding a Drop of Water from the Surface of the SI (111)

Abstract: Silicon is the main raw material for micro- and nanoelectronics. Achievements in these areas are based to a sufficient extent on knowledge of the processes occurring on the surface. Therefore, the study of these processes on a silicon surface is topical today. In this work, the dependences of the angles of water runoff from the silicon surface on the modes of their preparation are experimentally studied. The objects of study were Si single-crystal silicon wafers with (111) surface orientation. An aqueous solution of hydrofluoric acid was used to clean the surface from contamination and natural oxide. To assess the efficiency of cleaning and the state of the studied solid surfaces, the dynamic wetting angle was measured. Distilled water was used as a wetting liquid. It has been found that plates for which ethanol is used in the preparation procedure are better wetted with water. The obtained experimental data are confirmed by the Auger analysis — the plates treated with ethanol contain a smaller amount of carbon-containing impurities. The obtained surface topograms also indicate the effect of surface chemical treatment on its roughness.