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The one-dimensional structure preparation by electrospinning method is one of the most important especially since it can get fine diameters of fibers. Poly (vinyl alcohol) and (PVA)/polyethylene glycol (PEG) were mixed to get the blend and doped with different ratios (0.001, 0.002, 0.003) wt.% of calcium fluoride (CaF2) to get nanocomposite were fabricated using the electrospinning method at RT and voltage of 23 kV. Structural and optical properties were studied and the antibacterial activity was examined. The result of SEM analysis showed that the polymer blend and doped samples produced a random distribution with fine fibers at an average diameter range before CaF2 addition to be 68.97 nm and after CaF2 addition for each sample to be 45.76, 68.71, and 98.45 nm with a smooth surface. XRD analysis confirmed the existence of semi-crystalline PVA and PEG aggregates, and the CaF2 cubic crystalline phase appears when an additive of CaF2 nanoparticles up to 0.003 g. Absorbance spectra were recorded in the wavelength range of (200–800) nm. Absorption increased by two times when doping of CaF2 increased to 0.003 wt.%. The optical energy gap of fabricated films decreased with increasing CaF2 nanoparticles from (3.6–3.3) eV, while the refractive index increased. Increasing the content of NPs for the (PVA-PEG:CaF2) nanofibers mixture leads to an increase in the diameter of the inhibition zone for Escherichia coli for antibacterial activity. [ABSTRACT FROM AUTHOR]

On-axis single point diamond turning experiments were performed on (111)CaF 2 to investigate the effect of the resulting force system on the single crystal response. The cutting and thrust forces were measured and the resulting surface topography was characterized. The Schmid factors and fracture factors were calculated, and their ratio S f F f * was determined as a function of cutting direction and resultant force angle. It was found that this approach can be used to predict the number and location of resulting fracture lobes on the surface with respect to the lattice orientation. Two regimes with different topography were predicted when turning (111)CaF 2 , depending on the resultant force angle. [Display omitted] • Deformation in machined CaF 2 can be predicted by Schmid and fracture factors. • For resultant force angles > 55° fracture occurs in the 〈 2 1 ¯ 1 ¯ 〉 direction. • For resultant force angles < 45° fracture occurs in the 〈 2 ¯ 11 〉 and 〈 2 1 ¯ 1 ¯ 〉 directions. [ABSTRACT FROM AUTHOR]

Fluorapatite glass-ceramics were prepared at lower temperatures by atmospheric pressure sintering method using KF, MgF 2 and CaF 2 as additives, respectively. Using XRD, SEM and mechanical property test to justify the effect of different fluorides on the sintering properties of fluorapatite composites. The results show that fluoride can be used as nucleating agent, react with wollastonite and phosphate glass to crystallize rod-like fluorapatite phase during heat treatment. The crystallization mechanism of fluorine-containing glass-ceramics was analyzed by crystallization thermodynamics and crystallization kinetics. KF with lower melting point is beneficial to promote the crystallization reaction and improve the morphology stability of the glass ceramic composite, but the volatile gas released during the reaction will affect the mechanical properties of it, resulting in a flexural strength of only 11.81 MPa at 900 °C. For the samples supplemented with MgF 2 and CaF 2 , because of the formation of polycrystalline phase systems, the flexural strength of the composite at 900 °C increases to 62.79 and 52.6 MPa, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

Introduction: Hydroxyapatite (HAP) is promoted as biomimetic material in dentistry. The aim of the study was to investigate whether HAP-containing formulations can reduce erosive/abrasive tissue loss and to analyse components in these formulations. Methods: Two HAP toothpastes with and two without fluoride and a HAP mouthrinse were investigated, controls were active agent-free toothpaste, SnF2 toothpaste and F/Sn mouthrinse. For 10 days, human enamel samples were eroded for 2 min, 6×/day in 0.5% citric acid and immersed for 2 min, 2×/day in toothpaste slurries or mouthrinse. Half were additionally brushed for 15 s, 2×/day. The particulate fraction was extracted and examined morphologically and with element analyses. Other parameters were REA, RDA, fluoride and calcium content. Results: The F/Sn mouthrinse almost completely prevented tissue loss; none of the HAP formulations reduced tissue loss compared to the negative control, two increased it instead. Brushing increased tissue loss in all groups except the F/Sn mouthrinse. All toothpastes contained amorphous particles of different sizes. Elemental analysis identified Si and O, and additionally, Ca and P were present in small amounts on the particles of the HAP toothpastes and one HAP+F toothpaste. In the liquid phase, elevated calcium levels were found in one HAP toothpaste and in both HAP+F toothpastes; in the formulation with the highest value, the fluoride concentration was low. REA and RDA values were not associated with tissue loss. Conclusions: Whether alone or in combination with fluoride, HAP formulations had either no or a detrimental effect on erosive tissue loss and could not reduce abrasion. In the context of erosive tooth wear, HAP seems to be neither an alternative to fluoride nor a suitable supplement to it. [ABSTRACT FROM AUTHOR]

This study aimed to assess the antibiofilm effects of dentin desensitizers using a modified Robbins device flow cell system. The test desensitizers were Saforide, Caredyne Shield, and Clinpro White Varnish. Standardized dentin specimens were prepared from human single-rooted premolars, treated with one of the materials, and mounted on the modified Robbins device flow cell system. Streptococcus mutans biofilms were developed for 24 h at 37 °C under anaerobic conditions. Scanning electron microscopy, fluorescence confocal laser scanning microscopy, viable and total cell counts, acid production, and gene expression analyses were performed. A wavelength-dispersive X-ray spectroscopy electron probe microanalyzer was used to analyze the ion incorporations. Clinpro White Varnish showed the greatest inhibition, suggesting its suppression of bacterial adherence and transcription of genes related to biofilm formation. Saforide reduced only the number of viable bacteria, but other results showed no significant difference. The antibiofilm effects of Caredyne Shield were limited. The uptake of ions released from a material into dentin varies depending on the element. Clinpro White Varnish is effective for the short-term treatment of tooth sensitivity due to dentin demineralization. It prioritizes remineralization by supplying calcium and fluoride ions while resisting biofilm formation. [ABSTRACT FROM AUTHOR]

The solid waste generated during the process of aluminum electrolysis served as a valuable secondary source of fluorine. Within this category, regenerated cryolite stood as an intermediate product obtained from the anode carbon slag of aluminum electrolysis, which underwent treatment through flotation or baking. Regenerated cryolite could be transformed into more valuable products such as aluminum and calcium fluorides. This paper used regenerated cryolite as the raw material and calcium carbonate as the reagent, and the effects of baking temperature, insulation time, and reagent-to-cryolite mass ratio on the degree of cryolite transformation were discussed. The transformation degree of cryolite was characterized by baking loss rate, leaching loss rate, reaction rate, and fluoride ion concentration. Optimal transformation conditions were baking temperature of 850–900°C, insulation time of 2.0–3.0 h, and a mass ratio of calcium carbonate to regenerated cryolite of 0.7–0.8:1. The orthogonal experimental results showed that temperature had a significant effect, followed by the reagent, with time being a weaker factor. At a baking temperature of 900°C, a mass ratio of 0.8:1, and an insulation time of 2.0 h, the conversion rate of regenerated cryolite was 66.82%, and the purity of the direct calcium fluoride was 73.3%. By suitable acid leaching, the resultant calcium fluoride can be increased obviously. [ABSTRACT FROM AUTHOR]

This study investigates the thermoluminescence (TL) emission spectra of various doped CaF2 materials after exposure to ionizing radiation. The understanding of the TL spectra of these single-doped materials, systematically produced under the same sintering conditions, contributes to the interpretation of complex TL spectra observed in naturally occurring fluorite crystals. The production of Ce3+, Tm3+, Tb3+, Dy3+, Er3+, Pr3+, Nd3+, and Yb3+ doped calcium fluoride was carried out using the combustion synthesis method. The emission spectrum lines could be ascribed to the RE transitions that occur when a trapped hole center recombines with a RE2+. Emissions range from the ultra-violet to the near-infrared. This study aids in tailoring new materials for specific applications and the matching of emitted light to specific filters and instrumentation used for detection. [ABSTRACT FROM AUTHOR]

The properties of bulk contribution to sum-frequency generation reflected and transmitted by a finite layer in a multilayer system are described. The leading term is essentially due to the processes emitting in the transmission geometry, in particular for macroscopic layers. For such transmission processes, phase mismatch leads to the production of interference fringes when the layer thickness or a wavelength is tuned, which may be mistaken for resonant processes inside or at the surface of the material. Experimental evidence of such fringes measured from centrosymmetric bulks is provided for a diamond window in the far infrared and suggested for other materials in previously published data. The existence of a stationary point in the phase mismatch, related to the group velocity mismatch, is shown to be the source of another pseudo-resonant process in centrosymmetric calcium and barium fluorides, for which theoretical predictions reproduce the experimental observations. [ABSTRACT FROM AUTHOR]

Developing a feasible and low-cost strategy for the recovery of calcium fluoride efficiently from fluoride-containing wastewater is very essential for the recycle of fluoride resources. Herein, a modified lime precipitation method was employed to recover CaF2 from fluorinated wastewater using a special icy lime solution. Intriguingly, the highest F– removal was greater than 95% under the optimal condition, leaving a fluoride concentration from 200 to 8.64 mg/L, while the lime dosage was much lower than that of industry. Importantly, spherical-shaped CaF2 particles with a 93.47% purity and size smaller than 600 nm were recovered, which has a high potential for the production of hydrofluoric acid. Besides, the precipitation was significantly affected by Ca/F molar ratio, stirring time, temperature, and solution pH. Furthermore, the thermodynamics and kinetics were investigated in detail to reveal the crystallization process. As a result, the defluorination reaction followed the pseudo-second order reaction kinetics model. Also, CO2 in the air adversely influenced the CaF2 purity. Based on this facile method, a high lime utilization efficiency was applied to defluorination, which contributed to protecting the environment and saving costs. This study, therefore, provides a feasible approach for the green recovery of fluorine resources and has significance for related research. HIGHLIGHTS A facile icy lime precipitation method was employed to remove F−.; Highly pure spherical particles with CaF2 of more than 93% were recovered.; Thermodynamics implied that CO2 had an inhibitory effect on the purity of CaF2.; Change in F fitted well with the pseudo-second order reaction kinetics model.; The co-precipitation of CaF2 and CaCO3 occurred.;

This concise review provides an update on the use of calcium-based materials for the prevention of dental caries. Some calcium-based materials promote remineralization and neutralize bacterial acids, disrupting cariogenic biofilms and inhibiting bacterial growth. Medical Subject Headings of [Dental Caries] and [Calcium] were adopted to search publications. Information related to the aim of this review was extracted and summarized. Common calcium-based materials are calcium phosphate, hydroxyapatite, calcium carbonate, calcium fluoride and casein phosphopeptide–amorphous calcium phosphate (CPP-ACP). Calcium phosphate is commonly used in toothpaste. It provides calcium and phosphate ions, enhances the incorporation of fluoride into caries lesions and increases mineral density. Hydroxyapatite is a form of calcium phosphate that is chemically similar to the mineral found in teeth. It can be applied on teeth to prevent caries. Calcium carbonate can be found in toothpastes. It neutralizes bacterial acids and acts as a calcium reservoir during remineralization. Calcium fluoride is found in dental products and promotes remineralization as a source of fluoride, which can be incorporated into tooth enamel, forming fluorapatite and increasing resistance to caries. CPP-ACP is derived from milk proteins. It contains calcium and phosphate, which help to remineralize tooth enamel. CPP-ACP inhibits cariogenic bacteria. It also interacts with bacterial biofilms and disrupts their formation. These calcium-based materials can be used to boost the preventive effect of fluorides or, alternatively, as a therapy for caries prevention. [ABSTRACT FROM AUTHOR]

To compare the performance of Cention-N® with direct restorative materials used at the daily practice (e.g., resin-based composites/RBC, glass ionomer cements/GIC, bioactive resins, silver amalgam) via a systematic review study. The review followed the PRISMA-NMA recommendations, and the protocol of the review was published at osf.io/ybde8. The search was conducted in PubMed/MEDLINE, Scopus, Web of Science, Embase, Lilacs, and SciELO databases, as well as in the grey literature (Open Grey, Proquest, and Periódicos CAPES). Studies with an in vitro experimental design evaluating the characteristics and properties of Cention-N in comparison to other restorative materials were included. The risk of bias of included studies was assessed using the RoBDEMAT tool, and meta-analyses were conducted using Review Manager 5.4 and MetaInsight V3 tools. A total of 85 studies were included in the review, from which 79 were meta-analyzed. Several characteristics of direct restorative materials were analyzed, including physical (color change, degree of conversion, hardness, microleakage, polymerization rate, roughness, water solubility, water sorption), mechanical (bond strength to dentin, compressive strength, diametral tensile strength, flexural modulus, flexural strength, load-to-fracture, wear), and biological (alkalinizing effect, antibacterial activity, calcium and fluoride release) properties. Cention-N presented similar physico-mechanical properties compared to RBCs, but a stronger behavior than GICs. Despite the Alkasite nature of Cention-N, GICs may still demonstrate the greatest fluoride releasing ability from all direct restorative materials. This review confirmed the adequate behavior of Cention-N when compared to several other more traditionally used materials, confirming its applicability for the permanent restoration of decayed or fractured teeth. • Systematic review with meta-analysis that evaluates the physical-mechanical and biological properties of Cention-N. • Cention-N has superior properties to glass ionomer cement in terms of several properties. • Limitations of Cention-N are limited to color variety and manual manipulation. [ABSTRACT FROM AUTHOR]

Objectives: The main purpose of this study was to compare the remineralizing effects of casein phosphopeptide amorphous calcium phosphate fluoride (CPPACPF) and tricalcium phosphate (TCP) on artificially induced enamel white spot lesions (WSLs). Materials and Methods: In this in vitro study, 45 sound extracted premolars were immersed in a demineralizing solution (pH=4.5) for 96 hours, and were randomly divided into 3 groups of TCP, MI Paste Plus, and control. They were exposed to the remineralizing agents for 5 minutes once a day for 30 days. After mounting the teeth in resin blocks and polishing, they underwent a microhardness test at 3 different depths from the enamel surface. Data were analyzed by Prism software, two-way ANOVA, and Tukey's test (α=0.05). Results: The volume percentage of mineral content (VPM) was significantly different among the three groups at 30-, 60- and 90µm depths (P<0.0001). At 30µm depth, CPP-ACPF was significantly more effective than TCP (P<0.0001). At 60- and 90µm depths, there was no significant difference between CPP-ACPF and TCP (P>0.05). Conclusion: Both CPP-ACPF and TCP had significant efficacy for remineralization of artificially induced enamel WSLs under in vitro conditions. [ABSTRACT FROM AUTHOR]

The contamination of F inhibits the recovery of pure Li from spent Li-ion batteries (LIBs). In this study, we extracted F from a cathode material of spent Li-ion batteries by dry and wet processes and investigated the effect on Li recovery. In the dry process, F was removed by calcination at a controlled temperature in the presence of an F-fixing agent. In the wet process, F− ions were removed by adding Ca(OH)2 as a F-fixing agent to F-containing aqueous Li solution. Through sequential calcination (500 °C) and water leaching cycles, we achieved high Li- and F-leaching efficiencies of 87 and 93%, respectively. When the second calcination temperature (500 °C) was higher than the first (350 °C), a high-purity Li solution was attained from water leaching after the second calcination, in which the F− concentration was approximately 1/10th that of the Li+ concentration. Furthermore, the wet process successfully removed 98% of F from a F-containing aqueous Li solution by adding Ca(OH)2. Thus, pure Li was successfully extracted from spent LIBs by a carbothermal process using calcium salt and water leaching treatment. The proposed acid-free process facilitates the recovery of Li from spent LIBs, which is promising for the closed-loop recycling of Li. [ABSTRACT FROM AUTHOR]

Background: The objective of the study was to prepare and assess novel remineralizing oral films loaded with fluorapatite powder and composed of a combination of hydroxyethyl cellulose (HC) and cellulose nanofibers (CF). Methods: Three concentrations of the prepared nano-fluorapatite were tried and tested after loading in the cellulose blends and films were prepared using solvent cast technique. Along with SEM, measurements of thickness of film, bending tolerance, time of disintegration, surface pH and release of ions were made. The produced film's ability to remineralize demineralized teeth in vitro was investigated. Results: The findings showed that the films' thicknesses were uniform, their folding endurance exceeded 300, and their disintegration times exceeded 24 h. High amounts of fluoride and calcium ions were released, and nearly neutral pH values were observed. The distribution of fluorapatite powder particles was uniform, as demonstrated by SEM. The Vickers microhardness (VHN) of enamel and morphological analysis results showed that in comparison with the demineralized specimens, there was a substantial microhardness value increase following 15 and 30 days remineralization. Conclusions: Newly developed prepared films are a successful method for remineralizing early-stage demineralized tooth lesions. [ABSTRACT FROM AUTHOR]

A novel synthesis process and characterization of nano-calcium fluoride (n-CaF2) single crystal prepared from phosphogypsum waste. The phosphogypsum (CaSO4·2H2O) powder has been mechanically mixed with NH4F in presence of a controlled amount of water. The mixture still sintered for 48 hours until the formation of nano calcium fluoride particles. The n-CaF2 particles have been characterized by several techniques, The techniques utilized included X-ray diffraction (XRD), infrared spectroscopy (IR), and scanning electron microscopy (SEM). Therefore, it was confirmed that very pure n-CaF2 was obtained with a Ca/F ratio of 0.5 and an average crystalizing size measured according to the Debye-Scherrer equation of 11 nm. Based on the findings reached, The characterization data revealed successful synthesis of n-CaF2 from phosphogypsum. Additionally, the adsorption performance of the elaborated n-CaF2 was tested in Reactive Blue 21 (RB21) anionic dye removal, Adsorption tests were conducted in a batch reactor, focusing on key factors such as contact time, which can significantly influence the adsorption results. adsorption amount, pH, and dye concentration were tested. Hence results show an important adsorption performance of n-CaF2 with Reactive Blue 21 removal rate up to 90%. [ABSTRACT FROM AUTHOR]

The aim of this work was to optimize the sintering process of Tm-doped calcium fluoride in order to maximize the thermoluminescent (TL) response and the optically stimulated luminescence response when stimulated by visible light in the infrared (IRSL) and blue (BSL) regions. The samples were prepared by liquid phase synthesis. X-ray diffraction confirmed the formation of the characteristic calcium fluoride phase. In order to optimize the sintering process, response surface methodology (RSM) was applied separately to the three luminescence responses (TL, IRSL, and BSL). The results showed that this technique is an invaluable tool for optimizing the sintering process and that it is possible to approximate a predictive mathematical model that can estimate the luminescent area as a function of sintering temperature and time. [ABSTRACT FROM AUTHOR]

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The retrograde filling material, particularly mineral trioxide aggregate (MTA) employed in apicoectomy, should possess high antibacterial efficacy and osteogenic potential. We evaluated the antibacterial efficacy, biocompatibility, and osteogenic potential following the addition of silver nanoparticles (AgNPs) and calcium fluoride (CaF 2) in retrograde filling material of MTA. MTA was mixed with four different solvents. Group 1 (G1): distilled water, Group 2 (G2): 50 ppm AgNPs, Group 3 (G3): 1 wt% CaF 2 , and Group 4 (G4): 50 ppm AgNPs and 1 wt% CaF 2. The pH variation of each group was monitored, while the surface roughness was measured. The antibacterial efficacy against Enterococcus faecalis (E. faecalis) and the viability of murine pre-osteoblast (MC3T3) were evaluated for each group using colorimetric assays. The gene expression levels of osteogenic potential marker (OCN, ALPL, and RUNX2) in MC3T3 cells for each group were quantified using real-time-qPCR. Statistical analysis was performed at α = 0.05 level of significance. When comparing the levels of antibacterial efficacy, the order of effectiveness was G4>G2>G3>G1 (P < 0.05). In the cell viability test, owing to MTA-eluted growth medium having a positive effect on MC3T3 cell proliferation, G1–4 exhibited a statistically increased cell viability compared to the control (P < 0.05). However, G2–4 did not result in a statistically significant difference when compared to G1 (P < 0.05). Moreover, G4 exhibited the highest gene expression among the four groups (P < 0.05). The addition of AgNPs and CaF 2 to MTA could be a promising option for use as a new retrograde filling material. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Inorganic Analytical Chemistry / Zhongguo Wuji Fenxi Huaxue is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Crystalline calcium fluoride (CaF2) is drawing significant attention due to its great potential of being the gate dielectric of two-dimensional (2D) material MOSFETs. It is deemed to be superior to boron nitride and traditional silicon dioxide (SiO2) because of its larger dielectric constant, wider band gap, and lower defect density. Nevertheless, the CaF2-based MOSFETs fabricated in the experiment still present notable reliability issues, and the underlying reason remains unclear. Here, we studied the various intrinsic defects and adsorbates in CaF2/molybdenum disulfide (MoS2) and CaF2/molybdenum disilicon tetranitride (MoSi2N4) interface systems to reveal the most active charge-trapping centers in CaF2-based 2D material MOSFETs. An elaborate Table comparing the importance of different defects in both n-type and p-type devices is provided. Most impressively, the oxygen molecules (O2) adsorbed at the interface or surface, which are inevitable in experiments, are as active as the intrinsic defects in channel materials, and they can even change the MoSi2N4 to p-type spontaneously. These results mean that it is necessary to develop a high-vacuum packaging process, as well as prepare high-quality 2D materials for better device performance. [ABSTRACT FROM AUTHOR]

Nowadays, researches on the use of alkali metal salts as friction‐reducing and anti‐wear oil additives are continuing. In this study, the tribological effects of heavy metal containing MoS2 and alkali metal salt CaF2 additives on pure engine oil (20W50) were investigated using block‐on‐ring tester configured as surface contact geometry. The tests were performed at various contact loads, revolutions, and additive ratios. The crystal structure of the additives and their effects on surface quality and surface roughness analysed by x‐ray crystallography, scanning electron microscope and profilometry. Moreover, Energy dispersive spectrometry was used for element detection on worn surfaces. Results indicated that additives of MoS2 and CaF2 can reduce the friction, increase the capacity of load‐carrying and the wear resistance of surfaces. The additives improved the operation of the base oil in boundary lubrication zone by increasing the tribofilm forming effect. It was observed that the CaF2 additive exhibited more stable friction behaviour, while the MoS2 additive has better protective effects against scratches on the block surface. [ABSTRACT FROM AUTHOR]

Dentin hypersensitivity (DH) is a common challenge in pediatric patients with molar incisor hypomineralization (MIH), stemming from enamel porosity or exposed dentin after enamel breakdown. This three-arm randomized controlled clinical trial aims to evaluate the effectiveness of three different desensitizing treatment protocols. The study was conducted on 39 children, aged 6–14 years old, with MIH and DH. Group A received casein phosphopeptide plus amorphous calcium phosphate fluoride (CPP-ACPF) mousse and sham light therapy, Group B received placebo mousse and photo-bio-modulation therapy (PMBT), and Group C received both CPP-ACPF mousse and PMBT. DH evaluation using a visual analogue scale was performed at multiple time points. Both CPP-ACPF mousse and PMBT individually demonstrated desensitizing effects on dental elements affected by MIH. While PMBT had a greater immediate effect, the combination of the two therapies proved most effective in reducing DH. The VAS scores were statistically lower in group C compared to groups A and B, both after the first session (p = 0.0001) and after 28 days (p = 0.0005). This study suggests promising avenues for managing DH in MIH patients, highlighting the potential of combined therapies, specifically CPP-ACPF mousse and PMBT, for enhanced clinical outcomes. [ABSTRACT FROM AUTHOR]

In this work, Fe-2Cu-0.8C-CaF2 self-lubricating composites with calcium fluoride solid lubricant (3 □ 12 wt.%) were examined for their friction and wear at 5 and 10 m/s, at 500 °C. Addition of CaF2 decreased density and hardness of composites. During sliding, materials gained weight due to oxidation. Compared to the base matrix (Fe-2Cu-0.8C), composites showed lower weight gain and lower coefficient of friction. Increase in porosity with CaF2 content increased oxidation resulting in higher weight gain and increased friction due to wear debris abrasion. Increase in speed reduced weight gain due to higher material loss. Adhesion was the dominant wear mechanism in base matrix; delamination and wear debris abrasion in composites. Temperature rise at sliding surfaces was theoretically estimated. Increase in speed increased temperature, which reduced friction due to softening and shearing of solid lubricant. Composite with 3 wt.% CaF2 showed least surface damage and 6 wt.% showed lowest coefficient of friction, i.e., lower by 16% and 10% at 5, 10 m/s than base matrix. Tribological response of the composites to a broad range of applied parameters, viz. speed, load and temperature taken from earlier works and present work is briefly summarized. The study suggests the dominant role of CaF2 content and the wear debris in altering the tribological response. Further, the stability of the developed composites at high temperature and high load conditions was also established. The study suggests that the developed composites could serve high-load and high-temperature applications for heavy machinery such as bearings, shafts and gears. [ABSTRACT FROM AUTHOR]

The polynomial approach has previously been proposed for modelling the optical response of electromagnetic waves propagating across lossless multilayer thin films when a voltage is applied. This study presents a comprehensive investigation of the propagation of electromagnetic plane waves in lossless, nonmagnetic multilayer thin films under the influence of external transverse voltage. The main objectives of this research are to analyse the optical response of thin films subjected to varying numbers of layers. The model involves introducing an external transverse potential to the multilayer thin films to evaluate the impact on the optical response. External voltage can provide a means to actively tune and control the optical properties of multilayer thin films. By applying a transverse voltage, it becomes possible to modify the reflectance, transmittance, and absorption spectra of the films. This ability to dynamically manipulate the optical behaviour opens up new avenues for designing reconfigurable and adaptive optical devices with versatile functionalities. In this present article, the optical responses of electromagnetic waves propagating through multilayer thin films fabricated from calcium fluoride and silicon dioxide are being modelled and generated using the WT code. Both CaF2 and SiO2 are lossless materials. CaF2 and SiO2, being largely different in resistivity, are expected to display an enhanced effect in the accumulation of charge at the interfaces of adjacent layers. Simulations are performed on the optical response of multilayer CaF2/SiO2 thin films subjected to a tuneable transverse potential. The model is computationally implemented in a MATLAB program written by the author, dubbed the Wave Tensor (WT) code. The study demonstrates that the WT code efficiently and reliably predicts the optical response of thin films containing alternating lossless-lossless materials. The optical responses are obtained for different numbers of thin film layers and at various values of external transverse potential. The results show that the impact of the thickness of layers is greater than that of applying transverse voltage. In other words, the effect of the propagation matrices is stronger than the interface matrices. The variance in resistivity of adjacent layers partially enhances the influence of the interface matrices when applying a transverse voltage, leading to more significant effects on the curves of reflections and transmissions. The significance of the obtained results lies in their potential applications in optoelectronic devices and Nano photonics. Understanding and controlling the optical properties of thin films under external electrical fields can enhance the performance of devices such as optical filters, waveguides, and photodetectors. Moreover, the findings contribute to the fundamental understanding of light-matter interactions in layered structures and offer insights into the design and optimization of future nanostructured systems (Malek in Opt Quantum Electron 55:196, 2023; Al-Dossari in Opt Quantum Electron 55:484, 2023; Aly in Ismail Polym Bull, 2023; Aly in Sci Rep 13:9422, 2023). This research elucidates the optical behaviour of multilayer thin films under external transverse voltage and establishes a foundation for further investigations in the field (Shabat in Phys Scr 67:147, 2003; Taya in Optik Stuttg 122:666, 2011). The outcomes contribute to both applied and fundamental aspects of thin film optics and pave the way for future advancements in developing innovative optoelectronic devices and Nano photonic systems. [ABSTRACT FROM AUTHOR]

Using the method of evaporation by pulsed electron beam in vacuum the mesoporous nanopowder of CaF 2 with a specific surface area up to 91.5 m2/g was produced. The effect of annealing in different media and irradiation with a nanosecond electron beam (700 keV) on the evolution of the magnetic, luminescent and textural properties of CaF 2 nanoparticles have been studied. For the first time, a joint effect of the annealing medium and the absorbed dose of a relativistic electron beam irradiation on the specific surface area and magnetization of mesoporous nanopowders of the CaF 2 was discovered, which confirms the defective nature of ferromagnetism at room temperature of CaF 2 nanopowders. The effect of nanopowder surface properties on ferromagnetism at room temperature after annealing in different media is shown, a parameter for assessing this influence is proposed. It was found that annealing and irradiation caused a significant change only in the visible range, of the pulse cathodoluminescence spectra of the CaF 2 nanopowder, with the temperature and medium of the nanopowder pre-annealing as well as the irradiation dose being important. The relationship between luminescent and magnetic properties of nanopowder was shown. [ABSTRACT FROM AUTHOR]

This study explored the feasibility of fluoride removal from simulated semiconductor industry wastewater and its recovery as calcium fluoride using fluidized bed crystallization. The continuous reactor showed the best performance (>90% fluoride removal and >95% crystallization efficiency) at a calcium-to-fluoride ratio of 0.6 within the first 40 days of continuous operation. The resulting particle size increased by more than double during this time, along with a 36% increase in the seed bed height, indicating the deposition of CaF2 onto the silica seed. The SEM-EDX analysis showed the size and shape of the crystals formed, along with the presence of a high amount of Ca-F ions. The purity of the CaF2 crystals was determined to be 91.1% though ICP-OES analysis. Following the continuous experiment, different process improvement strategies were explored. The addition of an excess amount of calcium resulted in the removal of an additional 6% of the fluoride; however, compared to this single-stage process, a two-stage approach was found to be a better strategy to achieve a low effluent concentration of fluoride. The fluoride removal reached 94% with this two-stage approach under the optimum conditions of 4 + 1 h HRT combinations and a [Ca2+]/[F−] ratio of 0.55 and 0.7 for the two reactors, respectively. CFD simulation showed the impact of the inlet diameter, bottom-angle shape, and width-to-height ratio of the reactor on the mixing inside the reactor and the possibility of further improvement in the reactor performance by optimizing the FBR configuration. [ABSTRACT FROM AUTHOR]

Conventional resin-based sealants release minimal fluoride ions (F) and lack antibacterial activity. The objectives of this study were to: (1) develop a novel bioactive sealant containing calcium fluoride nanoparticles (nCaF2) and antibacterial dimethylaminohexadecyl methacrylate (DMAHDM), and (2) investigate mechanical performance, F recharge and re-release, microleakage, sealing ability and cytotoxicity. Helioseal F served as commercial control. The initial F release from sealant containing 20% nCaF2 was 25-fold that of Helioseal F. After ion exhaustion and recharge, the F re-release from bioactive sealant did not decrease with increasing number of recharge and re-release cycles. Elastic modulus of new bioactive sealant was 44% higher than Helioseal F. The new sealant had excellent sealing, minimal microleakage, and good cytocompatibility. Hence, the nanostructured sealant had substantial and sustained F release and antibacterial activity, good sealing ability and biocompatibility. The novel bioactive nCaF2 sealant is promising to provide long-term F ions for caries prevention. [ABSTRACT FROM AUTHOR]

Objective The aim of the study was to investigate the effects of silver diamine fluoride (38% SDF), sodium fluoride (NaF) varnish, and casein phosphopeptide-amorphous calcium phosphate fluoride (CPP-ACPF) on cola-eroded root dentin microhardness and mineral alteration in vitro. Materials and Methods Forty human root dentin slabs were exposed to alternating 10 cycles of cola drink and artificial saliva, repeated 3 times at 6-hour intervals. Specimens were randomly assigned to four groups: control (deionized water), 38% SDF, NaF varnish, and CPP-ACPF. All specimens underwent the second erosion process. Microhardness was measured at baseline (KHN 0), pretreatment (KHN 1), and posttreatment (KHN 2). The mean difference of microhardness (ΔKHN 2-1) was analyzed using one-way analysis of variance (ANOVA) and Tukey's post hoc tests (α = 0.05). The chemical composition and surface morphology were assessed using energy dispersive spectroscopy (EDS) and scanning electron microscope (SEM). Results All experimental groups exhibited dentinal tubule occlusion. Both 38% SDF and NaF varnish demonstrated a statistically significant increase in microhardness compared to CPP-ACPF. However, CPP-ACPF was comparable to the control group. EDS analysis showed an increase in weight percentage of fluorine in all groups. Furthermore, silver and chlorine were detected in the 38% SDF group. Conclusion All treatments enhanced eroded root dentin microhardness, with 38% SDF and NaF varnish demonstrating superior acid resistance and preventing morphological changes induced by cola re-immersion. [ABSTRACT FROM AUTHOR]

• Microwave hydrothermal acid leaching treatment of SCC is proposed firstly. • Microwave greatly reduces the reaction activation energy of the leaching process. • Under optimal process conditions, the fluoride removal rate can reach 95.6%. Toxic substances, like fluoride salts present in spent cathode carbon (SCC), have been a great risk to the environment and public health. Our approach involves alkali leaching to eliminate soluble fluoride, followed by microwave hydrothermal acid leaching to efficiently remove insoluble CaF 2 from SCC. The optimized conditions, including a temperature of 353 K, a solid–liquid ratio of 1:20, and a 60-minute reaction time, resulted in an impressive 95.6 % removal of fluoride from SCC. Various characterization techniques were employed to analyze the composition, micro-morphology, and elemental content of the materials before and after the leaching process. Furthermore, critical process parameters on the leaching separation of insoluble CaF 2 during microwave hydrothermal acid leaching were systematically investigated. The study removal mechanism revealed the transformation of insoluble CaF 2 in the process of microwave oxidation insertion-hydrothermal acid leaching for SCC. The kinetic characteristics of the two-stage leaching process of CaF 2 at different temperatures were analyzed according to the shrinkage kernel model. The results indicate that the two-stage leaching process of CaF 2 is affected by mixing control and by diffusion control, severally. The expansion of the graphite flake layer of SCC through oxidative intercalation was identified as a critical process for the thorough removal of CaF 2. Microwave hydrothermal acid leaching demonstrated a 17 % improvement over traditional hydrothermal acid leaching within the same reaction time, showcasing a noteworthy enhancement in fluoride removal. Consequently, the microwave oxidizing intercalation-hydrothermal acid leaching treatment of SCC, as explored in this study, offers an effective approach for achieving deep defluoridation of SCC. [ABSTRACT FROM AUTHOR]

To achieve optimal light transparency in MgAl 2 O 4 transparent ceramics, a higher sintering temperature is required to eliminate pores. However, inevitable rapid grain growth occurs, leading to lower mechanical properties. To address this problem, calcium fluoride (CaF 2) is utilized as a sintering additive to enhance the transparency of MgAl 2 O 4 ceramics. The influence of CaF 2 on the densification process and microstructure evolution is investigated. CaF 2 demonstrates notable abilities in facilitating densification and lowering the sintering temperature. Moreover, it inhibits grain growth during the final sintering stage. However, the sintering temperature must be controlled because the secondary phases (calcium aluminate) precipitate at a higher temperature, thereby affecting the homogeneity of the ceramic microstructure. After optimizing the sintering process, ceramics (with a thickness of 5 mm) containing 0.05 wt% CaF 2 exhibited the highest in-line transmittance of 81 % and 87 % in the visible and near-infrared wavelengths, respectively, after pre-sintering at 1505 °C for 3 h and subsequent hot isostatic pressing (HIPing) at 1550 °C for 3 h. [ABSTRACT FROM AUTHOR]

We propose and study a nanoscale strong coupling effect between metamaterials and polymer molecular vibrations using metallic split-ring resonators (SRRs). Specifically, we first provided a numerical investigation of the SRR design, which was followed by an experimental demonstration of strong coupling between mid-infrared magnetic dipole resonance supported by the SRRs fabricated on a calcium fluoride substrate and polymethyl methacrylate molecular vibrations at 1730 cm−1. Characterized by the anti-crossing feature and spectral splitting behaviors in the transmission spectra, these results demonstrate efficient nanoscale manipulation of light–matter interactions between phonon vibrations and metamaterials. [ABSTRACT FROM AUTHOR]

Aiming at the problem that it is difficult to recover valuable zinc from industrial solid wastes such as zinc oxide tailings and Grain slags, this paper prepares high-purity zinc oxide micro powder by using carbothermal reduction and oxidation method with local industrial zinc-containing solid wastes as raw materials. The thermodynamic process of the reaction between zinc silicate and carbon reduction in the zinc-containing slag was analyzed by a combination of thermodynamic calculations and experimental studies through HSC Chemistry. The effects of carbon allocation, roasting temperature, roasting time and CaF2 on zinc yield during zinc silicate reduction were discussed, and the results showed that the catalytic effect was most significant at 1000 ℃~1100 ℃ when CaF2 was used as a catalyst. The optimum process conditions were obtained: the zinc yield reached 97.44% at a temperature of 1100 °C, a holding time of 40 min, a carbon content of 20 wt% and a CaF2 addition of 5 wt%. Structural and compositional analyses of the volatilized product showed that the physical phase was hexagonal zinc oxide crystals with a particle size of 2~4 um and a purity of 99.47%. [ABSTRACT FROM AUTHOR]

The Yulong copper deposit in Tibet is a typical porphyry copper deposit, with about 30 million tons of copper oxide ore in the surface layer. However, more than 40% of the copper resources are in a combination state, resulting in an extraction efficiency of only 50% for copper via the hydrometallurgical process. In this study, the process mineralogy of the combined copper oxide ore was systematically investigated and a calcium fluoride-enhanced leaching process is proposed to increase the leaching efficiency of the combined copper ore. The process mineralogy of the combined copper oxide ore was analyzed using various testing techniques, including chemical analysis, X-ray diffraction, and a process mineralogy parameter testing system (Mineral Liberation Analysis). The results revealed that limonite accounted for 86.12% of the sample, and 63.51% of the copper resource existed in the form of combined copper oxide in limonite. However, it is difficult for the uniformly distributed combined copper oxide in limonite to sufficiently make contact with sulfuric acid, which is the leaching agent, resulting in low copper leaching efficiency. The enhanced leaching behavior of the combined copper oxide ores was also investigated, thereby determining effective and economical enhanced leaching conditions. Under optimal conditions, at a grinding fineness ratio of −0.074 mm (accounting for 85%), liquid-solid ratio of 4:1, sulfuric acid concentration of 50 g/L, temperature of 30 °C, CaF2 dosage of 1% of the ore mass, and leaching time of 4 h, the copper leaching efficiency increased to 60.57%, which was 7.34% higher than that of atmospheric pressure leaching. Finally, the enhanced leaching slag was analyzed using an electron probe microanalyzer. It indicated that fluorine ions can erode the combined copper oxide ore and facilitate the diffusion of hydrogen ions inside the limonite, thereby achieving a strengthening effect. [ABSTRACT FROM AUTHOR]

This study utilized a fluidized bed reactor (FBR) for fluoride removal from high-concentration fluoride-ion-containing simulated semiconductor industry wastewater and recovered high-purity CaF2 crystals. The effects of hydraulic retention time (HRT), pH, Ca2+ to F− ratio, upflow velocity, seed size and seed bed height were investigated by performing lab-scale batch experiments. Considering fluoride removal and CaF2 crystallization efficiency, 5 h HRT, pH 6, seed height of 50 cm and [Ca2+]/[F−] ratio of 0.55 (mol/mol) were found to be optimum. The effect of the interaction between the important process parameters on fluoride removal was further analyzed using response surface methodology (RSM) experimental design. The results showed that all the individual parameters have a significant impact (p = 0.0001) on fluoride removal. SEM-EDX and FTIR analysis showed the composition of the crystals formed inside FBR. HR-XRD analysis confirmed that the crystalline structure of samples was mainly CaF2. The results clearly demonstrated the feasibility of silica seed material containing FBR for efficient removal and recovery of fluoride as high-purity calcium fluoride crystals. [ABSTRACT FROM AUTHOR]

The requirement for clinically effective treatments to remineralize early enamel caries lesions is dictated by the principles of minimally invasive dentistry. Numerous studies outlined the significance of treating early carious lesions with different remineralizing agents. This study aimed to evaluate and compare the remineralization potential of topical cream containing casein phosphopeptideamorphous calcium phosphate (CPP-ACP) and CPP-ACP with fluoride in remineralizing artificial carious lesions on enamel. Forty-five freshly extracted human premolar teeth were selected as samples. These samples were divided into three groups: Group I-regular toothpaste without specific remineralizing agent; Group II-topical cream containing CPP-ACP and Group III topical cream containing CPP-ACP with fluoride. All the samples were viewed under scanning electron microscope (SEM) to assess the topographical pictures of the enamel surface and also subjected to energy dispersing X-ray analysis (EDX) for quantitative estimation of minerals, calcium (Ca), and phosphorous (P). In the result of the study, Group I does not show any increase in the Ca and P after applying toothpaste without any remineralizing agent but Group II and Group III showed a net increase in Ca and P-values after applying concerned remineralizing agents. Intergroup comparison showed Group III yielded higher net Ca and Pvalues than Group II. Two remineralizing agents showed remineralization potential on samples. Descriptive statistics were used to calculate the mean and standard deviation. Mann-Whitney test was used. The level of significance was set at 0.05. CPP-ACP containing fluoride showed better remineralizing potential than CPPACP. Hence, CPP-ACP containing fluoride can be considered the material of choice in remineralizing early enamel carious lesions. [ABSTRACT FROM AUTHOR]

Whispering gallery mode (WGM) resonators with an ultra-high quality (Q) factor provide a new idea for high-precision underwater acoustic sensing. However, acoustic energy loss due to watertight encapsulation has become an urgent problem for its underwater application. In order to solve this problem, this paper proposes a hollowed-out array structure. The finite element simulation shows that the acoustic wave transmission loss is improved by 30 dB compared with that of the flat plate encapsulation structure. Using a calcium fluoride (CaF2) resonator with a Q factor of 1.2 × 108 as an acoustic sensitive unit, the amplitude and frequency of the loaded acoustic wave are retrieved by means of the dispersion coupling response mechanism. The resonator's underwater experimental test range is 100 Hz–1 kHz, its acoustic sensing sensitivity level reaches −176.3 dB re 1 V/µPa @ 300 Hz, and its minimum detectable pressure can be up to 0.87 mPa/Hz1/2, which corresponds to a noise-equivalent pressure (NEP) of up to 58 dB re 1 µPa/Hz1/2. [ABSTRACT FROM AUTHOR]

Background: Recurrent caries were attributed to the lack of antibacterial properties of the dental materials. Silver nanoparticles (AgNPs) and calcium fluoride nanoparticles (CaF2NPs) are broad-spectrum antibacterial agents. The object of the study was to investigate the antibacterial properties of composite-incorporated AgNPs and CaF2NPs on Streptococcus mutans. Materials and Methods: This experimental study forty-eight disks containing 0.5, 1, and 1.5% wt AgNPs s (n = 24) and 5, 10, and 15% wt CaF2NPs were prepared from flowable composite resin (n = 24). The third group consisted of 9 types of the combination of AgNPs and CaF2NPs (n = 72). A field emission scanning electron microscope with an energy-dispersive X-ray spectroscopy analysis system was used to test for the presence of nanoparticles in composite resins. The antibacterial efficacy of dental composite was evaluated by disk diffusion agar test. The minimum inhibitory concentration (MIC) and minimal bactericidal concentration were conducted. Data were analyzed using one-way ANOVA and multiple Tukey HSD (Honestly Significant Difference) tests. Significance level was set at 0.05. Results: Nanoparticles added to composite produce bacterial inhibition zone. The greatest inhibition of bacterial growth was recorded in the third group which contained both nanoparticles (P < 0.05). MIC values decreased after adding CaF2 NPs to the AgNPs-containing composite. The results of the FE-SEM test indicate the presence of AgNPs and CaF2NPs in the dental composite resin sample. On the other hand, the formation of AgNPs and their elemental nature were proved using energy dispersive X-ray microanalysis EDX analysis. According to the results, composite resins containing 0.5% of AgNPs s and 15% of CaF2NPs exhibited a significantly lower antibacterial activity compared to the 1.5% and 1% of AgNPs s with 15% of CaF2NPs (P < 0.05). Conclusion: Dental composite resins-containing CaF2NPs and AgNPs showed anti-bacterial activity against S. mutans.

Objectives: This study assessed the effects of two remineralizing agents namely MI Paste Plus containing casein phosphopeptide amorphous calcium phosphate fluoride (CPP-ACFP) and Remin Pro containing hydroxyapatite, fluoride and xylitol (HFX) with/without erbium-doped yttrium aluminium garnet (Er:YAG) and CO2 laser irradiation on demineralized enamel microhardness. Materials and Methods: In this in vitro study, 70 sound human premolars were mesiodistally sectioned, demineralized at a pH of 4.6 for 8 hours, and randomly divided into 7 remineralization groups (n=10): of (I) MI Paste Plus (CPP-ACFP), (II) Remin Pro (HFX), (III) MI Paste Plus+CO2 laser (0.7 W power, 50 Hz), (IV) Remin Pro+CO2 laser, (V) MI Paste Plus+Er:YAG laser (1 W power, 10 Hz), (VI) Remin Pro+Er:YAG laser, and (VII) negative control. The Vickers hardness number of specimens was then measured. The groups were compared by one-way ANOVA and Tukey's test (α=0.05). Results: The mean microhardness was 319.8±49.9, 325.3±44.6, 359.4±35.7, 296.4±33.7, 319.9±58.1, 358.9±28.4, and 240.0±41.6 kg/mm2 in groups 1 to 7, respectively. The difference in microhardness was significant among the groups (P<0.0001). Pairwise comparisons revealed significant differences in microhardness between all groups (P=0.03) except between groups 1 and 2, 1 and 5, 2 and 5, and 3 and 6 (P>0.05). Conclusion: Both Remin Pro (containing HFX) and MI Paste Plus (containing CPP-ACFP) can cause enamel remineralization. MI Paste Plus+CO2 laser irradiation and Remin Pro+Er:YAG laser irradiation were significantly more effective than the application of each remineralizing agent alone. [ABSTRACT FROM AUTHOR]

Hydroxyapatite is widely used in bone implantation because of its similar mineral composition to natural bone, allowing it to serve as a biocompatible osteoconductive support. A bovine-derived hydroxyapatite (BHA) scaffold was developed through an array of defatting and deproteinization procedures. The BHA scaffold was substituted with fluoride ions using a modified sol-gel method to produce a bovine-derived fluorapatite (BFA) scaffold. Fourier-transform infrared spectroscopy and X-ray diffraction analysis showed that fluoride ions were successfully substituted into the BHA lattice. According to energy dispersive X-ray analysis, the main inorganic phases contained calcium and phosphorus with a fluoride ratio of ~1–2 wt%. Scanning electron microscopy presented a natural microporous architecture for the BFA scaffold with pore sizes ranging from ~200–600 μm. The BHA scaffold was chemically stable and showed sustained degradation in simulated-body fluid. Young's modulus and yield strength were superior in the BFA scaffold to BHA. In vitro cell culture studies showed that the BFA was biocompatible, supporting the proliferative growth of Saos-2 osteoblast cells and exhibiting osteoinductive features. This unique technique of producing hydroxyapatite from bovine bone with the intent of producing high performance biomedically targeted materials could be used to improve bone repair. [ABSTRACT FROM AUTHOR]

Calcium fluoride (CaF 2) ionic crystals have been observed to be sensitive to humid environments during ultra-precision machining, but further discussion about detailed mechanisms of the corresponding water-induced mechanical behaviors is still lacking. This work aims to perform a systematic investigation to understand the effect of water on the deformation and correlated plastic enhancement of CaF 2 under indentation. Micro-indentation experiments were employed to observe different mechanical responses including the pop-in behavior and surface pile-up to identify the water-enhanced plasticity of CaF 2 preliminarily. Then, atomic simulations were performed to reproduce the indentation process and confirm the close relationship between the indentation behaviors and water. The dislocation activities and crystal slip of both simulations with and without water were captured to analyze the plastic flow induced by hydration. Furthermore, Raman spectroscopy measurement was also adopted in this study to explain the corresponding enhancing mechanisms of plastic behaviors from the perspective of surface effect. • Micro-indentation tests confirm the water-enhanced plasticity of CaF 2. • MD simulations explain the enhanced plasticity from the view of plastic flow. • The deformation mechanisms are uncovered by theoretical analysis. • Water enhances plasticity by pre-stressing and reducing surface effects. • Results of Raman tests further demonstrate the water-induced prestressing. [ABSTRACT FROM AUTHOR]

The calcium fluoride (CaF 2) component has excellent light transmission and a high laser damage threshold in the UV band, and thus is a potentially ideal material for high-power laser facility. However, the low-damage surface is difficult to attain via the existing processing technologies due to its brittleness, especially the dissociation property of the (111) surface. We innovatively propose H 2 O(g) plasma-assisted porous diamond abrasive lapping technology to achieve low-damage and high-precision surface processing of CaF 2 component, which means that the CaF 2 component is modified first and then the softened modified layer is removed by the porous diamond abrasive lapping. The H 2 O(g) plasma modification mechanism was elucidated through a combination of molecular dynamics simulation and experiment and comparison with H 2 O(g) plasma etching. The modification layer including an oxide layer and a phase change layer was produced by adjusting the plasma processing process (power of 25 W and H 2 O(g) content of 10 ml). Then the modified CaF 2 component was lapped by the porous diamond abrasive tool on the ductile domain layer which is more than the modified layer and less than the sum of the modified layer and plastic domain. When the lapping process parameters were 200 rpm platen rotation speed and 20 N lapping pressure, a surface accuracy of 15.34 nm PV, 2.29 nm RMS (φ1 mm) was obtained. This study provides technical support for the low-damage processing of CaF 2 component. [ABSTRACT FROM AUTHOR]

Crystalline glass–ceramic fillers were prepared from calcium carbonate, silica, alumina, and calcium fluoride by heating and subsequent quenching in cold water. The fillers were incorporated into natural rubber (1,4‐cis‐polyisoprene) and the filled rubber composites were crosslinked with sulfur in the presence of different rubber additives. The unfilled and filled rubber composites were characterized. The transport properties of benzene, toluene, and p‐xylene (BTX) through the rubber composites were studied in terms of sorption, diffusion, permeation, and mass transfer coefficients. The effect of the ceramic fillers on the mechanical, thermal and transport properties were studied. The sorption data at different temperatures were used for calculating activation energy of diffusion, permeation, free energy, and enthalpy of sorption. The BTX remained in the liquid state within the composite matrix as evident from negative ΔS. The diffusion coefficient (D) and mass transfer coefficient (kmtc) of BTX decreased with the increase in filler loading. Accordingly, for the transport of BTX the unfilled rubber showed a D (D × 107 cm2/s) and mass transfer coefficient (kmtc × 104 cm/s) of 5.67/3.97/2.96 and 7.71/7.08/7.04, respectively which decreased to 5.06/2.95/2.57 and 7.53/6.95/6.90, respectively for the composite containing 50 wt.% ceramic filler. [ABSTRACT FROM AUTHOR]

The prevalence of dental caries in peatlands and non-peatlands in West Kalimantan require preventive acts based on its natural conditions and the behavior of local communities. The objective was to analyse risk factors for dental caries in communities living in peatlands and non-peatlands in West Kalimantan. The research is a causal comparative study with cross-sectional approach. The samples were chosen by purposive sampling technique among adolescents aged 17-27 years, who were domiciled in Pontianak City (peatland) and Bengkayang (non-peatland) all their lives. The results showed that dental caries is significantly correlated with debris in peatlands (rs= 0.289). On nonpeatlands, dental caries is correlated with drinking water phosphate (rs= 0.313) and calculus (rs = 0.034). In West Kalimantan, dental caries is significantly correlated with drinking water minerals (fluoride rs=-0.243; phosphate rs= 0.260), drinking water pH (rs = 0.235), behavior (rs= -0.327), and debris (rs = 0.240). The risk factors for dental caries in peatlands and non-peatlands in West Kalimantan are pH and drinking water minerals (fluoride and calcium), debris, calculus, and behavior. [ABSTRACT FROM AUTHOR]

This study presents an efficient and sustainable procedure for converting phosphogypsum (PG) waste, along with hydrofluoric acid (HF) and ammonia (NH3), into valuable materials. The results obtained demonstrate the high efficiency of this proposed procedure, resulting in the synthesis of relatively pure calcium fluoride (CaF2) nanoparticles and ammonium sulfate ((NH4)2SO4). The latter is recommended for agricultural use as a fertilizer, while the obtained CaF2 can be utilized in the metallurgical industry. Furthermore, this procedure not only offers a solution for reducing fluorine gas emissions and managing PG waste but also contributes to the conservation of fluorite reserves. [ABSTRACT FROM AUTHOR]

Electrolytic manganese residue (EMR) is toxic industrial solid waste. Electrolytic manganese enterprises have established a desulfurization and sulfuric acid production process to address its storage risks leaving desulfurized EMR (DEMR). In this study, DEMR was used as a raw material to prepare glass-ceramics. A method of melting and one-stage heat treatment was used to realize controlled crystallization of diopside, with calcium fluoride sludge (FS) as a nucleating agent. The impact of CaF 2 on the glass network structure, as well as on the microstructure and performance of the glass-ceramics, are discussed. CaF 2 can greatly improve the nucleation ability of glass precursors. When the addition of FS is small, the phase transition of glass is dominated by the diffusion of atoms and growth of diopside, forming dendritic crystals. When introducing more FS, the glass-ceramics form smaller island-shaped crystals due to many nucleation sites. The prepared glass-ceramics show excellent mechanical properties and chemical stability. Its hardness exceeds 6.5 GPa, with bending strength over 110 MPa. The acid resistance of glass-ceramics is higher than 99.5%, and the toxic metals in the raw materials are stable solidified. This study perfects the technology of EMR desulfurization pretreatment, which provides an effective graded recycling approach for EMR. [ABSTRACT FROM AUTHOR]

In this work, diboron trioxide and calcium fluoride are applied as composite additives to explore a process suitable for processing low-grade, high-vanadium, ultra-high-titanium vanadium–titanium magnetite. The metallized coal-based direct reduction–electromagnetic separation experiment was conducted. Results show that a good metallization ratio, separation, and the recovery of valuable components can be achieved under the following conditions: 8 pct diboron trioxide additive content, 8 pct calcium fluoride additive content, reduction temperature of 1100 °C, and reduction time of 30 min. The metallization ratio is 94 pct, and the recovery ratio of Fe, V, and Ti are 96, 84, and 85 pct, respectively. The X-ray diffraction results show that the phase transition under this condition is relatively simple, mainly metallic iron and different titanium oxides, without much intermediate product formation. Scanning electron microscope–energy-dispersive spectroscopy analysis shows that different conditions make the reduction products present differently in size, number, shape, and element distribution under different conditions, and this difference leads to differences in the separation and recovery effects of valuable components. The larger the metallic iron particle size is, the better the effect of component separation is. Diboron trioxide plays a role by destroying [SiO4] radicals to promote reduction. Fluorine is mainly diffused into silicate slag phase, and part of calcium fluoride still exists at relatively lower temperature of 1100–1150 °C. Overall, the metallization reduction–magnetic separation process with diboron trioxide and calcium fluoride as composite additives has achieved excellent metallization ratio, satisfied separation and recovery of valuable components, and large-scale lowered reaction temperature and time. [ABSTRACT FROM AUTHOR]

Objective: This study assessed whether combining photobiomodulation therapy (PBMT) with casein phosphopeptide‐amorphous calcium phosphate fluoride (CPP‐ACPF) paste can effectively reduce post‐home whitening tooth sensitivity (TS) without compromising shade change. Methods: Fifty participants were selected and assigned to one of four groups: (1) PLACEBO group—received a placebo paste and PBMT simulation; (2) PBMT group—received a placebo paste + PBMT; (3) CPP‐ACPF group—received CPP‐ACPF paste and PBMT simulation; (4) CPP‐ACPF + PBMT group—received both CPP‐ACPF paste and PBMT. The participants used whitening trays containing 22% carbamide peroxide for 2 h a day for 21 days. TS was measured daily using a visual analog scale, while shade change was assessed using a spectrophotometer: before bleaching treatment (T0), after the first (T1), second (T2), and third (T3) weeks of treatment, and 30 days (T4) after completing the whitening treatment. Results: Intragroup analysis revealed that the PLACEBO group had the highest increase in sensitivity during the whitening treatment. The CPP‐ACPF and PBMT groups showed no significant difference tooth whitening (TW) between weeks regarding aesthetic change. The CPP‐ACPF and PBMT group exhibited a significant reduction in TS between the first and third and between the second and third weeks TW, but not between the first and second. Conversely, the PLACEBO group showed a higher sensitivity than the other groups (p <.05). The CPP‐ACPF and PBMT groups did not differ from each other. Furthermore, the CPP‐ACPF and PBMT group showed a greater decrease in sensitivity than the PLACEBO group at T1, T2, and T3 (p <.01), and was significantly differed from CPP‐ACPF and PBMT groups only at T2 and T3. All groups confirmed TW effectiveness. Student's and paired t‐test did not reveal any significant difference between groups (p >.05). Conclusion: Therefore, PBMT associated with CPP‐ACPF paste can reduce TS without compromising the efficacy of TW. [ABSTRACT FROM AUTHOR]

The advent of organic polyester alkyd resin has revolutionized the coating industry due to its good adherence to any substrate, high gloss, and greater drying speed. This work deals with the characterization of nano calcium fluoride (CaF2 Nps) incorporated polyester alkyd coating for efficient multifunctional coating applications. The CaF2 Nps are prepared by employing a facile co‐precipitation process. The prepared particles are characterized using X‐ray diffraction analysis (XRD) and scanning electron microscopy (SEM) to analyze their size and morphology. By employing the ball milling technique, the CaF2 Nps along with other additives are mixed with alkyd resin to form a coating. The spreading ability, volatile and non‐volatile content, surface roughness, and coating thickness are evaluated. The minimal inhibitory concentration (MIC) is estimated by the turbidimetric assay method against gram‐negative and gram‐positive bacteria strains. Since these pigments hold very good antibacterial properties, the CaF2 are impregnated in alkyd resin coating, in which CaF2 nanoparticles are used as pigments. To reduce the nosocomial infection spreading in the hospital environment the formulated paint is analyzed for its antibacterial and anticorrosive studies. The current study confirmed CaF2 impregnated organic alkyd resin coating possesses promising comparable properties which would be a good choice for coatings, addressing multifunctional properties. [ABSTRACT FROM AUTHOR]

Defining the optimized volume of dual saturated (CaO and MgO) slags is of utmost importance to secondary metallurgy, especially for the ladle furnace. To be effective, these slags may present high desulphurization capability, combining the ability to shield the electric arc flare, to avoid the skull formation in the ladle borders and bottom, and suitable viscosity to provide fast incorporation of additives and tapping. Some fluidizers are applied for attaining the purpose of taking CaO/MgO into solution, being fluorspar (calcium fluoride, CaF 2) and silica sand (silicon oxide, SiO 2) broadly used in Si-killed steelmaking plants. At the Al-killed plants, either bauxite (mainly aluminum hydroxide) or calcium-aluminates are recommended choices. Nevertheless, for various reasons, some steelmakers use alternative fluidizers containing a significant amount of Na 2 O and K 2 O, such as sodalite and nepheline. Based on thermodynamic calculations (CALPHAD method), the effects of such alkalis on the CaO/MgO solubility and the optical basicity of slags on the CaO–SiO 2 –MgO–Al 2 O 3 system were explored in this paper. Moreover, the potential impact on the performance of MgO-based refractories in contact with these alkali-containing slags was also assessed by a thermodynamic approach. Although kinetic aspects must also be considered, it was seen that (Na 2 O) 2 ·(K 2 O) additions into these systems must be carefully managed to make the most of their ability to improve desulphurization, while avoiding the earlier corrosion of the refractory lining. [ABSTRACT FROM AUTHOR]