Hydrofluoric Research Articles

How does hydrofluoric acid etching affect the cyclic load-to-failure of lithium disilicate restorations?

This study investigated the effect of etching with distinct hydrofluoric (HF) acid concentrations on the cyclic load-to-failure (CLf) of simplified lithium disilicate glass-ceramic restorations adhesively cemented to a dentin analogue (n = 20): non-etched/control (CTRL), or etched for 20 s with HF acid at 3% (HF3), 5% (HF5), or 10% (HF10). A silane coating was then applied onto the ceramic surfaces. Fatigue tests followed the staircase approach (initial load= 720 N; step-size= 70 N; 500,000 cycles per sample; 20 Hz) using a hemispheric stainless-steel piston (Ø= 40 mm) under water. The CLf data were analyzed using Dixon and Mood method. Topographic and fractographic analyses were conducted. CLf (in N) of HF3 (1355 ± 32.0) and HF5 (1335 ± 58.8) groups were the highest and statistically similar; HF10 presented intermediate CLf (1175 ± 132.9), while the non-etched group had the lowest one (965 ± 145.0). Topographical analysis showed that the higher the HF acid concentration, the more pronounced the topographical changes. All failures (radial cracks) started from the inner surface of the ceramic discs. Topographical changes promoted by intermediate HF acid concentrations (3% and 5%) may improve fatigue performance for adhesively-cemented lithium disilicate restorations.

Calcium gluconate alleviates the toxic effect of hydrofluoric acid on human dermal fibroblasts through the Wnt/β-catenin pathway.

The present study was performed to determine the molecular mechanism of calcium gluconate (CG) in alleviating the toxic effect of hydrofluoric (HF) acid on human dermal fibroblasts (HDFs). HDF morphology was observed by optical microscopy and the vimentin immunofluorescence assay. Cell viability and apoptosis were evaluated by the Cell Counting Kit-8 and Annexin V/propidium iodide assays, respectively. The levels of apoptosis-associated factors, as well as Wnt2, Wnt3a and β-catenin were detected by reverse transcription-quantitative polymerase chain reaction and western blotting. Levels of matrix metalloproteinase (MMP)-1 and basic fibroblast growth factor (bFGF) were detected by ELISA and western blotting. Carboxyterminal propeptide of type I collagen (CICP) was detected by ELISA, while L-Hydroxyproline (L-HYP) was detected by colorimetry. First, the morphology of normal HDFs was observed. Cell viability was inhibited and apoptosis was increased in a dose- and time-dependent manner following treatment with HF acid [0, 2, 4, 6, 8, 10 and 20% (v/v)] for 0, 2, 4, 6, 8, 10 and 20 min. The effects were blocked by CG at different doses (50, 100 and 200 µmol/l) and time points (6, 12 and 24 h), following treatment with 8% (v/v) HF acid for 6 min. The levels of Caspase-3, B-cell lymphoma (Bcl)-2 associated X protein, Wnt2, Wnt3a and β-catenin were decreased, whereas Bcl-2 was increased by CG treatment dose-dependently, when compared with HF control. CG promoted the expression of MMP-1, bFGF and L-HYP, and inhibited CICP, when compared with HF control. Based on the present results, CG alleviated the toxic effect of HF acid on HDFs by regulating the Wnt/β-catenin signaling pathway.

Thermal oxidation and hydrofluoric acid treatment on the sandblasted implant surface: A histologic histomorphometric and biomechanical study.

This study aimed to analyze and compare the topographical, chemical, and osseointegration characteristics of a sandblasted acid-etched surface (SLA group), a sandblasted thermally oxidized surface (SO group), and a surface chemically modified by hydrofluoric (HF) acid (SOF group). Following the preparation and characterization of the relevant surfaces, 90 implants (30 for each group) were placed on the pelvic bone of six sheep. Resonance frequency analysis (RFA), insertion (ITV), removal torque value (RTV), and histomorphometric analyses (BIC%) were performed after three and 8weeks of healing. The results were analyzed by nonparametric tests (p<0.05). The roughness value (Ra) in the SOF group was significantly lower than the SLA and the SO group (p=0.136, p<0.001, respectively). This resulted in a substantially inferior ITV 14.83N/cm (SD: 4.04) than those achieved in the SLA and SO groups (19.50 (SD: 6.07) and 20.17N/cm (SD: 8.95), respectively; p=0.001). A statistically significant change in the RFA from the baseline (47.36 ISQ, SD: 6.93) to the 3rd week (62.56 ISQ, SD: 5.29) was observed in the SOF group only (p=0.008). The highest postplacement RFA and RTV values were measured from the SLA group (61.11 ISQ, SD: 7.51 and 78.22N/cm, SD: 28.73). The early-term (3rd week) BIC% was highest in the SO group (39.93%, SD: 16.14). After 8weeks, the differences in BIC% values were statistically not significant. Adjunct HF acid application on the thermally oxidized surface did not provide an additional benefit compared to the sandblasted and acid-etched surface (SLA group).

The Influence of Selective Laser Melting (SLM) Process Parameters on In-Vitro Cell Response.

The use of laser 3D printers is very perspective in the fabrication of solid and porous implants made of various polymers, metals, and its alloys. The Selective Laser Melting (SLM) process, in which consolidated powders are fully melted on each layer, gives the possibility of fabrication personalized implants based on the Computer Aid Design (CAD) model. During SLM fabrication on a 3D printer, depending on the system applied, there is a possibility for setting the amount of energy density (J/mm3) transferred to the consolidated powders, thus controlling its porosity, contact angle and roughness. In this study, we have controlled energy density in a range 8–45 J/mm3 delivered to titanium powder by setting various levels of laser power (25–45 W), exposure time (20–80 µs) and distance between exposure points (20–60 µm). The growing energy density within studied range increased from 63 to 90% and decreased from 31 to 13 µm samples density and Ra parameter, respectively. The surface energy 55–466 mN/m was achieved with contact angles in range 72–128° and 53–105° for water and formamide, respectively. The human mesenchymal stem cells (hMSCs) adhesion after 4 h decreased with increasing energy density delivered during processing within each parameter group. The differences in cells proliferation were clearly seen after a 7-day incubation. We have observed that proliferation was decreasing with increasing density of energy delivered to the samples. This phenomenon was explained by chemical composition of oxide layers affecting surface energy and internal stresses. We have noticed that TiO2, which is the main oxide of raw titanium powder, disintegrated during selective laser melting process and oxygen was transferred into metallic titanium. The typical for 3D printed parts post-processing methods such as chemical polishing in hydrofluoric (HF) or hydrofluoric/nitric (HF/HNO3) acid solutions and thermal treatments were used to restore surface chemistry of raw powders and improve surface.

Facile Preparation of Ag-Coated Superhydrophobic/Superoleophilic Mesh for Efficient Oil/Water Separation with Excellent Corrosion Resistance.

We present the facile preparation of a superhydrophobic-oleophilic stainless steel mesh with excellent oil/water separation efficiency and resistance to corrosion through hydrofluoric (HF) acid etching, Ag nanoparticle coating, and stearic acid modification, to construct a superhydrophobic micro/nanohierarchical structure. The surface of the treated mesh exhibits superhydrophobicity, with a water contact angle of 152°, and superoleophilicity, with an oil contact angle of 0°. The effects of variation in the HF etching time and Ag nanoparticle coating on surface wettability were explored. The treated mesh demonstrated a very high separation efficiency, as high as 98% for the optimal preparation, on a series of oil/water mixtures. The durability of the treated mesh was tested by repeated separation of kerosene/water mixtures, with the separation efficiency remaining higher than 97% after 40 cycles. In addition, the mesh exhibited an excellent chemical resistance to both acidic and alkaline conditions, with good wearing in hot water. The improved superhydrophobic-oleophilic mesh represents a feasible and realistic oil/water separation methodology even under harsh conditions, and it could have wide application in industrial processes.

Long-Term Effects on Graphene Supercapacitors of Using a Zirconia Bowl and Zirconia Balls for Ball-Mill mixing of Active Materials

Improving the energy storage performance of supercapacitor electrodes based on reduced graphene oxide (RGO) is one of the main subjects in this research field. However, when a zirconia bowl and zirconia balls were used for ball-mill mixing of the active materials for RGO supercapacitors, the energy storage performance deteriorated over time. Our study revealed that the source of the problem was the inclusion of zirconia bits from abrasion of the bowl and the balls during the ballmill mixing, which increased during a period of ~ 1 year. We probed two solutions to this problem: 1) hydrofluoric (HF) acid treatment of the RGO supercapacitors and 2) use of a tempered steel bowl and tempered steel balls for the mixing. For both cases, the energy storage performance was restored to near the initial level, showing a specific capacitance (C sp ) of ~ 200 F/g. Our results should lead to progress in research on RGO supercapacitors.

Synthesis of pyridinic-N doped carbon nanofibers and its electro-catalytic activity for oxygen reduction reaction

As catalytic active sites of nitrogen (N)-doped carbon nanomaterials (CNMs) for oxygen reduction reaction (ORR) are always under debate, synthesis of high purity pyridinic-N dominated CNMs is an effective approach to study the relation between pyridinic-N and active sites, as well as catalytic mechanism for ORR. Herein, the carbon nanofibers (CNFs) etched by hydrofluoric (HF) acid can be used to synthesize pure pyridinic-N, suggesting that the exposed edge-patterned surface facilitates to synthesize pure pyridinic-N. Moreover, it reveals that the carbon atoms adjacent to pyridinic-N could be the catalytic active sites for ORR.

Enhanced dielectric properties of Ca2+ doped Li-Al-Si photoetchable glass

The Li-Al-Si photoetchable glass (PEG) easily forms a complex three-dimensional (3D) structure, which is promising as an interposer in 3D integrated microsystems. However, its dielectric loss is rather large (~10−2@ 1 GHz), which inhibits the corresponding application in radio frequency (RF) microsystems. In this paper, the enhancement of dielectric properties caused by of Ca doping on the microstructure of the Li-Al-Si photoetchable glass system was investigated. The structure and performance were analyzed through X-ray diffraction (XRD), Mid-infrared spectroscopy analysis (MIR), Raman spectroscopy and impedance analysis. The results demonstrated that a significant modification in the dielectric properties were obtained with dielectric loss of 3 × 10−3. The reason was attributed to the decreased number of the non-oxygen bridge, which makes the structure more stable. Using hydrofluoric (HF) etching, through glass vias with a diameter of 117 µm were obtained.

The effect of Laser Shock Peening on Fatigue Life Using Pure Water and Hydrofluoric Acid As a Confining Layer of Al – Alloy 7075-T6

Laser shock peening (LSP) is deemed as a deep-rooted technology for stimulating compressive residual stresses below the surface of metallic elements. As a result, fatigue lifespan is improved, and the substance properties become further resistant to wear and corrosion. The LSP provides more unfailing surface treatment and a potential decrease in microstructural damage. Laser shock peening is a well-organized method measured up to the mechanical shoot peening. This kind of surface handling can be fulfilled via an intense laser pulse focused on a substantial surface in extremely shorter intervals. In this work, Hydrofluoric Acid (HF) and pure water as a coating layer were utilized as a new technique to improve the properties and to harden the treated surface of the Al -alloy 7075-T6. Fatigue life by means of laser peened workpieces was improved to 154.3%, 9.78%, respectively, for Hydrofluoric (HF) and pure water compared to un-peened specimens. And the outcomes of Vickers hardness test for laser shock peening with acid and pure water as well as un-peened specimens were 165.2HV30, 143.95HV30 and 134.7HV30, respectively showed a significant improvement in the hardness property.&#x0D;

Under pressure? Epicormic shoots and traumatic growth zones in high-latitude Triassic trees from East Antarctica.

Investigating the biology of trees that were growing at high latitudes during warmer geological periods is key to understanding the functioning of both past and future forest ecosystems. The aim of this study is to report the first co-occurrence of epicormic shoots and traumatic growth zones in fossil trees from the Triassic of Antarctica and to discuss their biological and environmental implications. Permineralized woods bearing scars of epicormic shoots were collected from the Triassic Fremouw Formation in Gordon Valley, Central Transantarctic Mountains, Antarctica in 2010. Samples from different portions of three specimens were prepared using standard thin section and hydrofluoric (HF) acid peel techniques, and anatomical details were studied in transmitted light. The fossil woods represent the outer part of trunks, with at least 40 growth rings that are 0.2-4.8 mm in width. Anatomical comparisons suggest that they represent a new tree taxon for the Triassic of Antarctica. Numerous small epicormic shoots can be seen crossing the wood almost horizontally and are locally branched. Each specimen also contains several occurrences of traumatic growth zones located in the early wood, in the cells produced either at the very start of the growing season or slightly later. This is the first report of epicormic shoots and traumatic growth zones in the wood of a Triassic tree from Antarctica. Their co-occurrence indicates that these trees from Gordon Valley were subjected to environmental stresses not seen in Triassic trees previously described from this region. This suggests that they had a different biology and/or were growing in a different habitat, which offers a new glimpse into the diversity of high-latitude trees in the Triassic greenhouse climate.

Effect of Erbium-yttrium, scandium, gallium and garnet (Er-YSGG) laser on the bond strength of lithium disilicate ceramics.

Objectives:To assess the bond strength of LD ceramics with resin composite material and surface conditioning using Er: YSGG laser and HF acid.Methods:Thirty LD ceramic (Emax, Ivoclar vivadent) discs were prepared using hot pressing technique and treated with hydroflouric acid (Group-1-HF acid) (9%) (n=10) and Er- yttrium, scandium, gallium and garnet laser (Group-2-ER-YSGG laser) (Waterlase iPlus, 10 Hz and power of 0.5 W, pulse duration of 230 μs) (n=10). Ten specimens were left untreated to be included as controls (Group-3-Control). All the specimens were treated with Adper Single Bond adhesive (3MESPE, St. Paul, MN, USA). Multicore buildups (3mmx3mm) were performed using a rubber mold on the ceramic surfaces and cured using LED light-curing unit for 140 sec. All specimens were tested using shear bond test and failure modes were assessed with a stereomicroscope and scanning electron microscope. Data was analysed using ANOVA and Tukey Kramer multiple comparisons test.Results:The maximum and minimum shear bond strength values were achieved in HF Acid specimens (Group-1) (28.15±4.72 MPa) and control specimens (13.47± 3.14 MPa) respectively. Specimens treated with HF acid showed significantly higher bond strength in comparison to laser treated and control specimens (p<0.01). Laser treated specimens had significantly higher bond strength as compared to controls (p<0.01).Conclusions:Hydrofluoric (HF) acid treatment showed significantly better outcomes than YSGG laser surface treatment.

Shear Bond Strength of Metal Brackets to Porcelain Using a Universal Adhesive.

Introduction: Bracket bonding to porcelain has high failure rate compared to bonding to enamel.Aim:This study aimed to assess the shear bond strength (SBS) of metal brackets to porcelain using a universal adhesive. Material and Methods:In this in vitro experimental study, 40 porcelain blocks (1x1x1 cm3)were divided into four groups (n=10). The porcelain surfaces were etched with 10% hydrofluoric (HF) acid and bonded to metal brackets using Transbond XT composite and the following bonding protocols: Transbond XT bonding agent alone in group 1, silane plus Transbond XT bonding agent in group 2, silane plus universal adhesive (G-Premio bond) in group 3 and universal adhesive alone in group 4. The SBS was measured using a universal testing machine at a crosshead speed of 1 mm/minute. Fracture surfaces were evaluated under a stereo microscope, and the adhesive remnant index (ARI) scores were determined. Results: The highest and the lowest SBS values were noted in groups 3 (17.06±2.58 MPa) and 4 (9.85±4.76 MPa), respectively. Type of adhesive had no significant effect on SBS (P=0.611). However, the effect of application of silane on SBS was significant (P=0.000). Groups subjected to the application of silane showed higher SBS values than others. The mode of failure was mainly adhesive in groups 2 and 3, and adhesive and mixed in groups 1 and 4. The difference in ARI scores was statistically significant (P=0.016). Conclusion: Universal adhesive and Transbond XT were not significantly different in SBS. However, application of silane significantly increased the bond strength.

Production of open-cell Al composite foams by direct casting with silica-gel beads

Open-cell Al composite foams, with the addition of Al2O3 particles, have been successfully produced, using direct casting technique of space holder materials. The amorphous silica-gel (SiO2) beads of 3 mm were employed as a space holder. The ADC12 cast Al alloy was added with 1-5 wt.% Al2O3 particles, prior to casting process. The infiltration of molten Al composites was performed at 750°C for 30 min with a pressure assistance. Elimination of silica-gel beads was achieved, using the solution of hydrofluoric (HF) acid for 10 h, resulting in open-cell foams with a porous structure, replicated to the morphology of silica-gel beads. However, it was found that the foam structure was also slightly damaged during the removal process of silica-gel beads.© 2017 Elsevier Ltd. All rights reserved.Selection and/or Peer-review under responsibility of The 10th Thailand International Metallurgy Conference.

Laboratory Study of Micro-shear Bond Strength of Two Resin Cements to Leucite Ceramics using Different Ceramic Primers

To evaluate the effect of Monobond Etch & Prime on the micro-shear bond strength (MSBS) of resin cements to leucite surface and to compare the MSBS of two different resin cements to conditioned leucite surfaces with different primer systems. Twenty-one leucite ceramic disks (10 mm diameter, 2 mm thickness) were divided into three groups (n = 7). Group I: 9.6% hydrofluoric (HF) acid and Monobond S (Ivoclar Vivadent, Liechtenstein), then conventional resin cement was applied. Group II: Monobond Etch & Prime (Ivoclar Vivadent, Liechtenstein), then conventional resin cement was applied. Group III: 9.6% HF acid and with Monobond N (Ivoclar Vivadent, Liechtenstein), then adhesive resin cement was applied. The assigned resin cement was applied in each disk through five plastic tubes with an inner diameter of 1.6 and 1.9 mm height, and then light cured. Micro-shear bond strength was determined by pulling out the resin cement using universal testing machine (Instron®, USA). One-way analysis of variance (ANOVA) and Student's t-test were used to determine statistical difference (a = 0.05) between each two groups. The results showed that group III had the highest MSBS values (7.32 ± 2.47) followed by group II (6.24 ± 2.16), whereas group I had the lowest MSBS values (5.7 ± 2.7). Nevertheless, there was no statistically significant difference between the results of all the groups. Monobond Etch & Prime has shown comparable results to the most popular combination of HF acid and silane. The combination of HF acid and Monobond N and self-adhesive resin cement has shown the best MSBS results, though not statistically significant. The clinicians can use simplified ceramic primer technique (Monobond Etch & Prime) which has comparable MSBS to the most popular combination of HF acid and silane.

Whispering gallery modes in a liquid-filled hollow glass microsphere.

We develop a hydrofluoric (HF) etching process to open a microhole on the hollow glass microsphere (HGM). The typical whispering gallery mode (WGM) resonance was observed by coupling the HGM with a tapered fiber. Dioctyl phthalate was filled into the HGM, and the resonance wavelength decreased at elevated temperatures. We analyzed the WGM resonance properties inside the liquid-filled HGM with a higher or lower refractive index in comparison to the HGM wall. Four different liquids were also injected into the HGM to investigate the influence of the thermo-optic coefficient on the temperature sensitivity. Size-dependent experiments further showed that HGMs with varying sizes have varying temperature sensitivity. The maximum temperature sensitivity observed was 334.3 pm/°C.

Surface Microfabrication of Conventional Glass Using Femtosecond Laser for Microfluidic Applications

Recently, a lot of attention has been paid to a single-cell analysis using microfluidic chips, since each cell is known to have several different characteristics. The microfluidic chip manipulates cells and performs high-speed and high-resolution analysis. In the meanwhile, femtosecond (fs) laser has become a versatile tool for the fabrication of microfluidic chips because the laser can modify internal volume solely at the focal area, resulting in three-dimensional (3D) microfabrication of glass materials. However, little research on surface microfabrication of materials using an fs laser has been conducted. Therefore, in this study, we demonstrate the surface microfabrication of a conventional glass slide using fs laser direct-writing for microfluidic applications. The fs laser modification, with successive wet etching using a diluted hydrofluoric (HF) acid solution, followed by annealing, results in rapid prototyping of microfluidics on a conventional glass slide for fluorescent microscopic cell analysis. Fundamental characteristics of the laser-irradiated regions in each experimental procedure were investigated. In addition, we developed a novel technique combining the fs laser direct-writing and the HF etching for high-speed and high-resolution microfabrication of the glass. After establishing the fs laser surface microfabrication technique, a 3D microfluidic chip was made by bonding the fabricated glass microfluidic chip with a polydimethylsiloxane (PDMS) polymer substrate for clear fluorescent microscopic observation in the microfluidics.

Experimental Investigation and Study the Effect of Hydro Fluoric Acid in Ultrasonic Machining of Polycarbonate Bullet Proof UL-752 and Acrylic Heat Resistant BS-476 Glass

The main objective of this experimental work is to study the effect of Hydro Fluoric acid in ultrasonic machining of polycarbonate bullet proof UL-752 and Acrylic Heat resistant BS 476 Glass. In which, mixture of abrasive particle are also used as the input machining parameter. Three types of abrasive; Alumina, Silicon Carbide and Boron Carbide are used for machining. Experiment has been performed with 8mm of high carbon high chromium tool steel (D2), high carbon steel (HCS) and high speed tool steel (HSS) tools. The material removal rate was father enhanced by HF acid. The experimentation date represent the main effect plots for tool wear rate and material removal rate. After analysis, results reveals that Al2O3+SiC+B2C mixed slurry (1:1:1), Hydro Fluoric acid with 1% concentration and High Speed tool Steel material produce the higher material removal affect.

Improvement of laser damage thresholds of fused silica by ultrasonic-assisted hydrofluoric acid etching**Project supported by the China Postdoctoral Science Foundation (Grant No. 2016M592709) and the National Natural Science Foundation of China (Grant No. 51535003).

Polished fused silica samples were etched for different durations by using hydrofluoric (HF) acid solution with HF concentrations in an ultrasonic field. Surface and subsurface polishing residues and molecular structure parameters before and after the etching process were characterized by using a fluorescence microscope and infrared (IR) spectrometer, respectively. The laser induced damage thresholds (LIDTs) of the samples were measured by using pulsed nanosecond laser with wavelength of 355 nm. The results showed that surface and subsurface polishing residues can be effectively reduced by the acid etching process, and the LIDTs of fused silica are significantly improved. The etching effects increased with the increase of the HF concentration from 5 wt.% to 40 wt.%. The amount of polishing residues decreased with the increase of the etching duration and then kept stable. Simultaneously, with the increase of the etching time, the mechanical strength and molecular structure were improved.

Corrosive fluid casing is rebuilt

At one Hydrofluoric (HF) Alkylation Unit, a pump casing in the depropanizer reflux service had suffered many years of wear and needed to be replaced. One company manufactured a casing for the backup pump.

Elucidation of the pore size and temperature dependence of the oxygen diffusion into porous silicon

Steady state photoluminescence technique is proposed for the measurement of the diffusion of oxygen into porous silicon (PS). In this work, the PS layers on n-type Si substrates were prepared by anodic etching in hydrofluoric (HF) acidic solution at a dc current under white light illumination. The PS layers with three different pore sizes (0.7, 1.9, and 4.5μm) were obtained by etching in different HF concentrations in ethanol (from 33% to 67%). The effect of the pore size on the oxygen diffusion was performed at room temperature. In addition to the pore size, the effect of the temperature on the oxygen diffusion was also studied at 35, 45, and 65°C for PS layer with 1.9μm pore size. It was observed that the diffusion of the oxygen to PS layers takes place in two different stages. In the first stage, the oxygen molecules are adsorbed on the surface of the PS layer while they diffuse through into the pores in the second stage. For all cases the diffusion in the first stage is much faster than the second stage. The oxygen diffusion increases as the pore size and the temperature increase in the first stage. In the second stage, while the diffusion increases with the pore size, it almost does not change with temperature.