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Aufkonversions-Nanokristalle (UCNC) zeichnen sich als einzigartige Lumineszenzreporter aus, die Nah-infrarotes Anregungslicht in Photonen höherer Energie umwandeln. Für die gezielte Anpassung von Eigenschaften, bedarf es ein tiefes Verständnis der Prozesse der Aufwärtskonversionslumineszenz (UCL) und deren Abhängigkeit von Material und Partikeldesign. Diese Doktorarbeit untersucht die UCL-Prozesse von Yb3+,Er3+ dotierten SrF2-UCNC und zielt darauf ab, die UCL-Eigenschaften der bisher unterschätzten kubischen Wirtsgitter zu verstehen und zu steigern. Hierbei wird die fluorolytische Sol-Gel-Synthese als neuartige Syntheseroute für UCNC vorgestellt. Vorteile wie ausgezeichnete Reproduzierbarkeit, viele Freiheitsgrade bei der Temperaturbehandlung und Partikelgestaltung werden anhand von SrF2 UCNC demonstriert. Die UCNC wurden mittels UCL-Spektren, UCL-Quantenausbeuten, leistungsdichte-abhängiger relativer spektraler Verteilung sowie der Lumineszenzabklingkinetiken unter Einbeziehung kristalliner Eigenschaften wie der Kristallphase, der Kristallitgröße, der Gitterparameter und der Teilchengröße untersucht. Die Abhängigkeit der UCL-Eigenschaften von der Dotierungsmenge wurde mit einer umfassenden Dotierungsreihe beschrieben und der optimale Dotierungsbereich (Yb3+,Er3+) von kleinen, ungeschalten SrF2-UCNC eingegrenzt. Bei der Studie dotierter Kerne mit passivierenden Schalen wurde der Einfluss von Temperaturbehandlung auf die UCL-Mechanismen und die Kern-Schale-Vermischung untersucht. Anhand von unterschiedlich kalzinierten UCNC Pulvern wurde die Empfindlichkeit der UCL gegenüber der Änderung kristalliner Eigenschaften, wie Kristallphase, Kristallinität, und Kristallitgröße betrachtet. Zusammen liefern die Dotierungs-, die Kern-Schale- und die Kalzinierungsstudie wertvolle Einblicke in das gitterspezifische Verhalten der UCL-Eigenschaften als Funktion der Energiemigration und der Kristalleigenschaften. Upconversion nanocrystals (UCNC) represent a unique type of luminescence reporters that convert near-infrared excitation light into higher energy photons. Tailoring UCNC with specific luminescence properties requires an in-depth understanding of upconversion luminescence (UCL) processes and their dependence on material and particle design. This Ph.D. thesis focuses on the UCL processes of Yb3+,Er3+ doped SrF2-UCNC and aims to understand and enhance the UCL properties of the previously underestimated cubic host lattices. Herein, fluorolytic sol-gel synthesis is introduced as a novel synthetic route for UCNC. Advantages such as excellent reproducibility, high flexibility in temperature treatment and particle design are demonstrated using SrF2 UCNC. The UCNC were characterized by UCL spectra, UCL quantum yields, excitation power density-dependent relative spectral distribution, and luminescence decay kinetics involving crystalline properties such as crystal phase, crystallite size, lattice parameters, and particle size. The dependence of UCL properties on doping amount was described in a comprehensive doping study, and the optimal doping range (Yb3+,Er3+) of small, unshelled SrF2-UCNC was identified. In a core-shell study of doped core UCNC with passivating shells, the influence of temperature treatment on UCL mechanisms and core-shell mixing was investigated. Further, using different calcined UCNC powders, the sensitivity of UCL to the change of crystalline properties, such as crystal phase, crystallinity, and crystallite size, was assessed. Together, the doping, core-shell, and calcination studies provide valuable insight into the lattice-specific behavior of UCL properties as a function of energy migration and crystal properties.

BACKGROUND: Within the scope of minimally invasive dentistry, the use of different biocompatible remineralization agents on incisors affected by molar-incisor hypomineralization (MIH) gains importance. OBJECTIVE: To evaluate the effect of casein phosphopeptide amorphous calcium fluoride phosphate (CPP-ACFP) and calcium glycerophosphate (CaGP) in mineral density (MD) of white/creamy and yellow/brown demarcated opacities on incisors affected by MIH by means laser fluorescence (LF). METHODS: As a cross-over, randomized trial, twenty-two children with 167 incisors affected by MIH were recruited and randomly assigned to one of the two different agents and crossed over to other agents with two weeks washout in between. Incisors were examined by using LF at all before and after three months periods. RESULTS: The results of the paired t-tests for determining the period effect between the baseline findings showed significant difference in white/creamy and yellow/brown demarcated opacities of LF values for both groups (p

Composite restorations with calcium fluoride nanoparticles (nCaFThree nCaFBT and BTM nCaFNovel nCaF

It is vital to remove residual tumor cells after resection to avoid the recurrence and metastasis of osteosarcoma. In this study, a mineral nanomedicine, europium-doped calcium fluoride (CaF

At present, the production of magnesium is mainly carried out semi-continuously with ferrosilicon as reducing agent under high temperature and high vacuum. In order to continuously produce magnesium, a new method of extracting magnesium from low-grade magnesite and calcium carbonate by silicothermal method in flowing inert gas was proposed. The effects of calcium fluoride (CaF2) on decomposition rate, decomposition kinetics, reduction rate of magnesia, and crystal type of dicalcium silicate in reduction slag were investigated in the paper. The experimental results showed that calcium fluoride could accelerate the decomposition of carbonate, and had no side effect on the calcined products. In addition, the analysis results of DTA curves showed that calcium fluoride could reduce the decomposition reaction activation energy and the reaction temperature of carbonate in the prefabricated pellets. The results of reduction experiments showed that proper calcium fluoride could promote the reduction rate of magnesia, and in the temperature range of 1250? ~ 1350?, with the same timeframe, the corresponding calcium fluoride contents were 5%, 3%, and 1% respectively when the reduction rate reached the maximum. Excessive calcium fluoride reduced the reduction rate of magnesia, but it promoted the transformation of dicalcium silicate to ? phase in the reduction slag.

In this innovative study, biogas has been associated with calcium carbonate [CaCO

Transport phenomena including the electromagnetic, concentration of ions, flow, and thermal fields in the electroslag remelting (ESR) process made of slag, electrode, air, mold, and melt pool are computed considering tertiary current distribution. Nernst–Planck equations are solved in the bulk of slag, and faradaic reactions are regarded at the metal–slag interface. Aiming at exploring electrochemical effects on the behavior of the ESR process, the calculated field structures are compared with those obtained using the classical ohmic approach, namely, primary current distribution whereby variations in concentrations of ions and faradaic reactions are ignored. Also, the influence of the earth magnetic field on magnetohydrodynamics in the melt pool and slag is considered. The impact of the polarity of electrode, whether positive, also known as direct current reverse polarity (DCRP), or negative, as known as direct current straight polarity (DCSP), on the transport of oxygen to the ingot of ESR is investigated. The obtained modeling results enabled us to explain the experimental observation of higher oxygen content in DCSP than that of DCRP operated ESR process.

Background/purpose MTA is used to induce hard tissue regeneration in various procedures. This study evaluated the biocompatibility and mineralization potential of mineral trioxide aggregate (MTA) containing calcium fluoride (CaF2). To verify if the change of components affected physical properties, the setting time, solubility, and surface roughness were measured. Materials and methods Human dental pulp cells (HDPCs) were treated with powder and set MTA containing CaF2 (0, 1, 5, and 10 wt %). The proliferation of HDPCs was investigated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The mineralization potential of HDPCs was investigated with the relative gene expression of alkaline phosphatase (ALP), collagen type I (ColI), osteocalcin (OCN), and runt-related transcription factor 2 (Runx2) using real-time reverse transcription polymerase chain reaction (RT-PCR). For investigating the physical properties, setting time and solubility were tested. Surface profiles of material were analyzed by a non-contact surface profiler and a scanning electron microscope (SEM). Results MTA-5% CaF2 mixtures increased the proliferation and the mineralization-related gene expression of HDPCs to a greater degree than pure MTA. The addition of CaF2 to MTA delayed the setting, but the difference was only significant in the MTA-10% CaF2. Solubility and surface roughness was not altered. Conclusion The addition of more than 5% CaF2 can be considered to increase the regeneration potential of pulp cells without adverse effects on physical property.

Topical application of different fluoride preparations is considered to be the gold standard of oral prophylaxis measures in preventive dentistry. Hydroxyapatite nanoparticles (nano-HAP) as well, have received considerable attention for dental use in the past few decades. The purpose of this in-vitro study was to analyze the interaction between nano-HAP and different fluoride preparations. In order to investigate the possibility to establish, in the presence of nano-HAP, reproducible calcium fluoride surface layers, specimens were visually examined with regard to the surface coverage’s structure, morphology, homogeneity and stability. Test series based on enamel and dentine specimens, that were obtained from extracted bovine teeth, were conducted. Thereby, sodium fluoride, olaflur, elmex Fluid (10.000 ppm) and an aqueous nano-HAP solution (5%) served as test products and sterile water as reference. First, single application of nano- HAP and fluoride was tested. After 5 min of incubation in the test solution, the surface coverage was examined by scanning electron microscopy (SEM). Furthermore, samples were determined by energy dispersive X-ray spectroscopy (EDX) to identify the present elements of the surface layer, particularly fluoride. To test the calcium fluoride layer’s persistence and stability, samples were exposed to the spray of a dental multifunctional syringe for 20 s using maximum pressure and maximum water supply. In the second application protocol, fluoride and nano-HAP were applied simultaneously and in the third application protocol they were used sequentially. SEM visualisation showed that the simultaneous or sequential addition of nano-HAP led to a distinct change in the surface layer’s structure. Agglomerates of various sizes were formed, with obviously different morphology from the calcium fluoride globules, not covering the surface homogeneously and sprayed off with the multifunctional syringe easily. Application of pure fluoride compounds resulted in a more homogeneous calcium fluoride surface layer with higher persistence in comparison to the combination of fluoride and nano-HAP. Interaction between fluoride and nano-HAP clearly could be proved. On enamel as well as dentine surfaces, the combined application of nano-HAP and fluoride has a negative effect on the stability and persistence of the calcium fluoride surface precipitate.

The anticancer mechanism of nanozymes is dominantly associated with the capacity for generation of reactive oxygen species (ROS) caused by the valence change of metal elements. However, very little research is focused on and has achieved the exploration and development of enzyme-mimicking activities of valence-invariable metal compounds. Herein, a distinct valence-invariable calcium fluoride (CaF

Fluoride-containing alkali-free setting accelerators are a common type of admixture used in tunnel shotcrete but few studies in the literature focus on the effect of their fluoride compounds on the setting and hardening properties of accelerated cement paste under low environment temperatures. Tunnel shotcrete in cold regions or winter construction periods would be obviously influenced by low environment temperatures, especially for its fast setting and quick support applications. The objective of this work is to evaluate the early age hydration behavior of different accelerated cement pastes under 20 °C and 5 °C environment temperatures. In this study, setting time measurement, early age strength development, hydration ion leaching concentration, isothermal calorimetry, X-ray diffraction, and ESEM were performed on cement systems prepared with a non-fluoride alkali-free accelerator (aluminum sulfate solution with over 60% solid content) and a designed fluoride-containing alkali-free setting accelerator (aluminum sulfate and fluoride compound). The results showed that the fluorides obtained in alkali-free accelerators promote C3S dissolution and massive ettringite needles together with monosulfoaluminate (AFm) hydrate formation, thus leading to a quicker setting effect and low sensitivity to low environment temperatures than in non- fluoride groups. However, the rate of mechanical strength development of cement pastes hydrated within 24 h was decreased obviously when fluorine-containing alkali-free accelerator was used. This phenomenon is mainly related to the crystallization of thin-plate shape calcium fluoride (CaF2) formations and promoted conversion of ettringite to monosulfoaluminate hydrate in the accelerating period, thus weakening the denseness of C-S-H gel and inhibiting alite further hydration.

Precision laser spectroscopy of the 229-thorium nuclear isomer transition in a solid-state environment would represent a significant milestone in the field of metrology, opening the door to the realization of a nuclear clock. Working toward this goal, experimental methods require knowledge of various properties of a large band-gap material, such as calcium fluoride doped with specific isotopes of the heavy elements thorium, actinium, cerium, neptunium, and uranium. By accurately determining the atomic structure of potential charge compensation schemes by using a generalized gradient approximation within the ab-initio framework of density functional theory, calculations of electric field gradients on the dopants become accessible, which cause a quadrupole splitting of the nuclear-level structure that can be probed experimentally. Band gaps and absorption coefficients in the range of the 229-thorium nuclear transition are estimated by using the G0W0 method and by solving the Bethe–Salpeter equation.

This study aimed to investigate the efficacy of three remineralizing agents on dental erosion in primary teeth.Forty primary molars were randomly divided into four groups (n = 10 each): self-assembling peptide (Psub11-4/sub), casein phosphopeptide-amorphous calcium fluoride phosphate (CPP-ACFP), sodium fluoride (NaF) and artificial saliva (AS; control). The erosion-like formation was created by immersing the samples in citric acid (4 × 2 min, pH 2.3) and AS (4 × 2 h, pH 7). The eroded samples were then treated with remineralizing agents and subjected to further erosion consisting of 15 cycles (3x/8-h interval) of immersion in citric acid and AS for 6 s each. Alterations in the mineral content and morphology of the samples were quantified using a microhardness tester and atomic force microscope.All agents had a significant remineralization effect on eroded primary tooth enamel. After further erosive challenge, enamel loss in the CPP-ACFP group was found to be significantly lower than in all other groups, and no significant difference was found between the Psub11-4/suband NaF groups.This study showed that all tested materials had remineralization ability, and CPP-ACFP had a superior effect in inhibiting enamel loss due to dental erosion in primary teeth. © 2022 Australian Dental Association.

Adding uniaxial in-plane anisotropy to the otherwise four-fold Si(001) surface has for a long time been known to be possible via epitaxial deposition of a single atomic layer of calcium fluoride (CaF2), which forms an array of micron-long (110) oriented parallel stripes when the substrate temperature during the growth is kept in the range of 700–800 °C. As shown in the present paper, a fine control over dimensions and periodicity of the stripe array is possible through the introduction of a two-stage growth process at which the (110) orientation of the fluorite layer is settled at the high-temperature nucleation stage, while the stripes of controllable dimensions are formed at the second stage. By varying the substrate temperature at the second growth stage in the range of 800–400 °C, the stripe arrays with a periodicity from above 30 nm to below 10 nm can be fabricated with the height variation changing accordingly. Such variability can be of use in the applications in which the striped fluorite surface is used to influence the anisotropy of other functional (e.g., magnetically ordered or organic) materials grown on top. While large CaF2 stripes can be easily characterized by direct space techniques such as atomic force microscopy, the study of the shape and in-plane correlation between the stripes of a much smaller size is most effectively achieved through the use of grazing incidence reciprocal space techniques applied in the present paper. The discussed universal approach to 3D reciprocal space mapping utilizing scattering of X-rays and high-energy electrons offers a complementary way to study samples with arrays of long and narrow one-dimensional stripes at their surface.

Using the Bridgman-Stockbarger method, crystals of triple fluoride CaF2-SrF2-BaF2 were grown in a composition range similar to that of CaSrBaF6. The crystals were 10-12 mm in diameter and 50–60 mm in length. The CaSrBaF6 crystal is a new optical material which is transparent in the mid-IR, visible and UV ranges. The uneven distribution of the components along the length of the crystal did not exceed 10 %. The edge of the absorption band in the IR range was 14.3 μm, and the optical absorption at the wavelength of 200 nm did not exceed 18 % (less than 0.2 cm–1). The refraction indices were 1.4527, 1.4488, and 1.4458 for the wavelengths of 633, 969, and 1539 nm respectively. The crystal melts in the temperature range of 1150–1210 °С. The CaSrBaF6 composition is an appropriate matrix for doping with rare-earth ions in order to obtain functional single-crystal and ceramic materials of the visible and IR ranges.

Bone is a highly calcified tissue with 60 wt% inorganic components. It is made up of mineralized collagen fibrils, where the platelet-like hydroxyapatite nanocrystals deposit within the collagen fibrils in an oriented manner. Inspired by the special structure and biological activity of bone, we realize the intrafibrillar mineralization of collagen films with oriented calcium fluoride nanocrystals in vitro. Amorphous calcium fluoride (ACF) precursors are generated by polyacrylic acid through polymer-induced liquid precursor processes. The precursors are ready to infiltrate and fill the gap zones laterally and then diffuse to occupy the whole space inside the collagen longitudinally. Finally, the fully mineralized collagen fibrils exhibit a single-crystal-like structure after transforming precursors to co-oriented nanocrystals under the influence of arranged collagen molecules. Expanding the collagen mineralization from 1D fibrils to 2D films, the growth of mineralized areas on the films with a reaction-limited behavior is found. The kinetic rate of growth is around 0.2-0.3 μm min-1, which depends on the pH of the solution. Furthermore, the mineralized collagen films exhibit an enhanced ability of cell proliferation over the pure collagen matrices. Understanding the mineralization of artificial collagen-based scaffolds may have broad promising potentials for bone tissue regeneration and repair in the future.

Collagen fibrils present periodic structures, which provide space for intrafibrillar growth of oriented hydroxyapatite nanocrystals in bone and contribute to the good mechanical properties of bone. However, there are not many reports focused on bioprocess-inspired synthesis of non-native inorganic materials inside collagen fibrils and detailed forming processes of crystals inside collagen fibrils remain poorly understood. Herein, the rapid intrafibrillar mineralization of calcium fluoride nanocrystals with a periodically patterned nanostructure is demonstrated. The negatively charged calcium fluoride precursor phase infiltrates collagen fibrils through the gap zones creating an intricate periodic mineralization pattern. Later, the nanocrystals initially filling the gap zones only expand gradually into the remaining space within the collagen fibrils. Mineralized tendons with organized calcium fluoride nanocrystals acquire mechanical properties (indentation elastic modulus ∼25.1 GPa and hardness ∼1.5 GPa) comparable or even superior to those of native human dentin and lamellar bone. Understanding the mineral growth processes in collagen may facilitate the development of tissue engineering and repairing.

In most clinical circumstances, secondary caries at the margin of fixed dental restorations leads to restoration failure and replacement. Accordingly, the objectives of this study were to: (1) develop a novel rechargeable nano-calcium phosphate (NACP) and nano-calcium fluoride (nCaFsub2/sub) resin-based cement; and (2) investigate their mechanical properties and calcium (Ca), phosphate (P), and fluoride (F) ion release, recharge, and re-release for the first time.The cement matrix consisted of pyromellitic glycerol dimethacrylate (PMGDM), ethoxylated bisphenol-A-dimethacrylate (EBPADMA) was denoted PEHB. Four cements were fabricated: (1) PEHB+0%NACP+0%nCaFsub2/sub(experimental control); (2) PEHB+25%NACP+0%nCaFsub2/sub, (3) PEHB+0%NACP+25%nCaFsub2/sub; (4) PEHB+12.5%NACP+12.5% nCaFsub2/sub. RelyX luting cement was used as a commercial control. Mechanical properties and long-term Ca, P, and F ion release, recharge, and re-release were evaluated.Adding 25% NACP, 25% nCaFsub2/suband adding both 12.5% NACP and 12.5% nCaFsub2/subto the cement matrix presented a significantly higher shear bond strength, flexural strength compared to the commercial control (plt; 0.05) with a comparable outcome with no significant different (pgt; 0.05) compared to experimental control. The film thickness results of all cement groups met the ISO requirement (lt;50 µm). The resin cement group with both 12.5% NACP and 12.5% nCaFsub2/subsuccessfully released Ca, P, and F ions at 3.1 ± 0.01, 1.1 ± 0.05, and 0.51±0.01 mmol/L respectively. Moreover, it showed the ability to re-release Ca, P, and F ions at 0.62±0.01, 0.12±0.01, and 0.42±0.01 mmol/L respectively.The resin cement group with both 12.5% NACP and 12.5% nCaFsub2/subdemonstrated the advantages of both types of bio-interactive fillers as it could release a higher level of ions than the resin cement with 25%nCAFsub2/suband exhibited a better rechargeability compared to the resin cement with 25%NACP.The ability of this novel resin-based cement to release, recharge, and re-release Ca, P, and F ions could be one of the keys to lengthening the survivability of fixed dental restorations. These features could help to reduce the onset of secondary caries by enhancing the remineralization and preventing the demineralization of tooth structures.

In this paper, we report the fabrication and characterization of high-quality distributed Bragg reflectors (DBRs) deposited by low-energetic thermal evaporation. This technique allows deposition of high-quality thin films with an accurate control of thickness at the nanoscale. We investigated, for the first time, the use of tungsten oxide (WO3) and calcium fluoride (CaF2) as high (2.15) and low (1.4) refractive index materials, respectively, for DBR fabrication. They consist of nine pairs of WO3/CaF2 layers, with a central wavelength λc tuned at 640 nm and a maximum reflectance of 99.6%. A passive microcavity consisting of a λ/2 thick spacer of CaF2 sandwiched between 8.5 pairs of WO3/CaF2 has also been fabricated. We investigated the optical behavior of this microresonator after post-deposition thermal treatment at different temperatures, showing a blue shift of the resonant mode and an increase in its intensity. Indeed, heat treatment induced a compaction of the DBR multilayer, leading to more defined and clearer interfaces, as demonstrated by scanning electron microscopy cross section measurements. This behavior results in an improvement of the microcavity quality factor (up to 400) as the temperature increases, which is currently the highest value obtained for microcavities obtained by thermal evaporation processes, so far. These results represent a further step forward toward the development of high-reflectivity mirrors and high-quality microresonators fabricated by the low-energy deposition technique. Such a structure could find extensive application in nano-photonics, optoelectronics, and sensors, even based on soft organic materials.

Low-energy ion scattering (LEIS) probes the atomic composition of the outer surface. Well-defined reference samples are used for the quantitation. For elements like fluorine and calcium, it is not easy to find suitable, clean, and homogeneous references, since fluorine is a gas and calcium is a very reactive metal. In contrast to surface analytic techniques such as XPS, the extreme surface sensitivity of LEIS makes it difficult to use stable compounds like CaF2 as reference, since these compounds are not homogeneous at the atomic scale. With LEIS, CaF2 is not expected to show an atomic ratio F/Ca = 2.0. Thus, before CaF2 can be used as reference, its atomic surface concentrations have to be determined. Here, 3-keV He+ scattering by a LiF(001) single crystal, an evaporated layer of Ca, and a Cu foil are used as basic references. High-purity CaF2 is available in two forms: a single crystal and a powder. For a practical reference, powders are preferred, since if bulk impurities segregate to the surface, they will be dispersed over a large surface area. It is found that both CaF2 (111) and powder have similar F/Ca atomic ratios. This confirms the F termination for both samples. For the powder, the F and Ca signals are reduced by 0.77 ± 0.03 in comparison with those for the single crystal. The atomic sensitivity factors and relative sensitivity factors have been determined for F, Ca, and Cu.

Surface‐mounted metal–organic frameworks (SURMOFs) show promising behavior for a manifold of applications. As MOF thin films are often unsuitable for conventional characterization techniques, understanding their advantageous properties over their bulk counterparts presents a great analytical challenge. In this work, we demonstrate that MOFs can be grown on calcium fluoride (CaF2) windows after proper functionalization. As CaF2 is optically (in the IR and UV/Vis range of the spectrum) transparent, this makes it possible to study SURMOFs using conventional spectroscopic tools typically used during catalysis or gas sorption. Hence, we have measured HKUST‐1 during the adsorption of CO and NO. We show that no copper oxide impurities are observed and also confirm that SURMOFs grown by a layer‐by‐layer (LbL) approach possess Cu+ species in paddlewheel confirmation, but 1.9 times less than in bulk HKUST‐1. The developed methodology paves the way for studying the interaction of any adsorbed gases with thin films, not limited to MOFs, low temperatures, or these specific probe molecules, pushing the boundaries of our current understanding of functional porous materials., Calcium fluoride windows were functionalized to facilitate the growth of surface‐mounted metal–organic frameworks (SURMOF). The resulting HKUST‐1 SURMOF was measured by in situ IR spectroscopy during CO and NO adsorption. This work showcases the practicality for utilizing such calcium fluoride windows for in‐depth in situ studies of various functional porous materials.

Orientador: Jaime Aparecido Cury Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba Resumo: Como não há forte evidência científica que a aplicação profissional de fluoreto (APF) na forma de espuma fluoretada é eficaz para controlar cárie e os produtos são geralmente lançados no mercado sem uma avaliação mínima do seu potencial anticárie, o objetivo deste estudo foi avaliar o potencial anticárie da espuma Flúor Care® (FGM, Joinville, SC, Brasil,12300 ppm F, acidulado), utilizando como controle positivo o produto Flúor gel® (DFL, Rio de Janeiro, RJ, Brazil, 12300 ppm F, acidulado). Foi avaliado se a espuma tinha uma concentração necessária de fluoreto e se este foi capaz de reagir com o esmalte, formando produtos de reação implicados com o mecanismo de ação do fluoreto no controle de cárie. A concentração de fluoreto nos produtos foi avaliada pela técnica direta utilizando eletrodo íon-específico para fluoreto (EIE-F) e estava de acordo com o declarado pelos fabricantes. O estudo foi conduzido em duas etapas: Primeiro foi feita uma padronização de fatores que poderiam interferir com o efeito do fluoreto aplicado e em seguida foi feita a comparação da reatividade da espuma e gel com o esmalte hígido e cariado. Foram padronizados (n=5/variável) os fatores: i) Aplicar na superfície do esmalte seca ou úmida; ii) agitação ou não do produto durante a aplicação; iii) tempo de agitação durante a aplicação (1, 2 ou 4 min) e iiii) tempo de lavagem (15, 30 ou 60 s) com água purificada após a aplicação. As variáveis foram estudas a partir da formação do tipo-CaF2 ("CaF2") no esmalte com lesão de cárie induzida e foram analisadas estatisticamente de forma independente para espuma e gel. A única variável que se mostrou significante (p0,05) quanto à formação de FT e "CaF2", seja no esmalte hígido ou cariado. Em relação à FAp formada a espuma não diferiu do F-gel (p>0,05) para o esmalte cariado, mas a concentração no hígido foi menor (p0.05) in terms of TF and "CaF2" formation, whether in sound or carious enamel. Regarding the FAp formed, the foam did not differ from the F-gel (p>0.05) for carious like-lesion enamel, but the concentration in sound was lower (p

Spectroscopy on metal–organic framework (MOF) films and the molecular phenomena associated to them is mostly limited to grazing incidence methods. To allow for transmission-based characterization and highlight the applicability of MOFs on transparent substrates, UiO-67, UU-1, and ZIF-8 MOFs are synthesized on CaF2 windows. It is revealed that the growth of the UiO-67 MOF follows a Volmer–Weber mechanism using scanning electron microscopy (SEM). This growth is assisted by growing seeds in solution, which anchor on the film and become part of the intergrown film itself. UU-1, a copper-based MOF, is formed after spin coating the Cu-BTC precursors, showing its characteristic fiber-like morphology and resulting inter-fiber macroporosity. ZIF-8 is formed using a “flash”-synthesis, and it is shown that this approach resembles a Volmer–Weber growth mode as well. Last, CO probe molecule adsorption FT-IR spectroscopy is utilized to study the effect of methanol exposure. UiO-67 becomes inaccessible toward CO, due to the formation of methoxy species, whereas UU-1 undergoes a topotactic transformation to HKUST-1. ZIF-8 is the most stable as methanol only removes impurities from the framework. This approach opens the venue for other film materials to be studied in situ synthesis, sorption, or catalysis using transmission-based spectroscopy.

We report photoluminescence and photoionization properties of Sm

Dentin bonding based on a wet-bonding technique is the fundamental technique used daily in clinics for tooth-restoration fixation and clinical treatment of tooth-related diseases. Limited bonding durability led by insufficient adhesive infiltration in the demineralized dentin (DD) matrix is the biggest concern in contemporary adhesive dentistry. This study proposes that the highly hydrated noncollagenous protein (NCP)-formed interfacial microenvironment of the DD matrix is the root cause of this problem. Meanwhile, the endogenous phosphate groups of the NCPs are used as pseudonuclei to rapidly induce the formation of amorphous CaF

Received: 02.07.2021. Revised: 16.08.2021. Accepted: 13.09.2021. Available online: 21.09.2021. The viscosity of cryolite melts of conventional composition NaF–AlF3–CaF2–Al2O3 was studied by rotational viscometry using the FRS 1600 high-temperature rheometer. The cryolite ratio of the NaF–AlF3 melt was 2.1, 2.3, and 2.5; the Al2O3 content varied from 2 to 6.6, and CaF2 – from 0 to 8 wt%. The measurements were carried out in the temperature range from liquidus to 1200 °C. The conditions for the laminar flow of the investigated melts were determined, based on the measurements of the cryolite melts viscosity as a function of the shear rate at a constant temperature. A shear rate of 12 ± 1 s–1 was chosen for studying the viscosity temperature dependence for all samples. The viscosity temperature dependence of cryolite melts is described by a linear equation. The temperature coefficient b in this equation has negative values and varies in the range of (–0.01)–(–0.06) mPa·s/deg. It was found that the viscosity of cryolite melts of conventional composition in the range of operating temperatures of aluminum electrolysis (950–970 °C) varies from 2.5 to 3.7 mPa·s (depending on the composition and temperature). The viscosity of cryolite-alumina melts increases with the rise of alumina content: 1 wt% Al2O3 increases the viscosity, on average, by 1%. However, the influence of CaF2 is more significant: the addition of 1 wt% CaF2 leads to an increase in viscosity by 3%. A decrease in the CR of the melt by 0.1 (in the range of 2.1–2.5) leads to a decrease in the viscosity of cryolite melts by 2.3%. A viscosity regression equation for the cryolite melts of conventional composition as a function of several independent parameters (temperature, CR, CaF2 and Al2O3 content) is obtained by the multivariable approximation of experimental data. The equation satisfactorily (within 1.5%) describes the viscosity of conventional industrial electrolytes and can be used for estimation of their viscosity.

Ultrasound (US) and X-ray imaging are diagnostic methods that are commonly used to image internal body structures. Several organic and inorganic imaging contrast agents are commercially available. However, their synthesis and purification remain challenging, in addition to posing safety issues. Here, we report on the promise of widespread, safe, and easy-to-produce particulate calcium fluoride (part-CaF2) as a bimodal US and X-ray contrast agent. Pure and highly crystalline part-CaF2 is obtained using a cheap commercial product. Scanning electron microscopy (SEM) depicts the morphology of these particles, while energy-dispersive X-ray spectroscopy (EDS) confirms their chemical composition. Diffuse reflectance ultraviolet-visible spectroscopy highlights their insulating behavior. The X-ray diffraction (XRD) pattern reveals that part-CaF2 crystallizes in the face-centered cubic cell lattice. Further analyses regarding peak broadening are performed using the Scherrer and Williamson–Hall (W-H) methods, which pinpoint the small crystallite size and the presence of lattice strain. X-ray photoelectron spectroscopy (XPS) solely exhibits specific peaks related to CaF2, confirming the absence of any contamination. Additionally, in vitro cytotoxicity and in vivo maximum tolerated dose (MTD) tests prove the biocompatibility of part-CaF2. Finally, the results of the US and X-ray imaging tests strongly signal that part-CaF2 could be exploited in bimodal bioimaging applications. These findings may shed a new light on calcium fluoride and the opportunities it offers in biomedical engineering.

BACKGROUND Dentin hypersensitivity (DH) is a common problem in the population that can have a significant impact on the quality of life of those who suffer from the condition. OBJECTIVES Compare the efficacy of two treatments for DH: Ca/PO4- /F- varnish (Clinpro White Varnish) and ionomeric sealant (IS) (Clinpro XT Varnish) with a placebo. METHODS Participants (121) with at least one tooth with visual analogue scale (VAS) score of 4 and above were randomly and blindly allocated to the groups. Treatments were performed by a trained researcher. DH was evaluated by another blind researcher after the treatment and after 1 week, 4 weeks, 3 months and 6 months. After 4 weeks, placebo received the DH treatment with IS; thus, the participants were not assessed after 3 and 6 months. Primary outcome was DH reduction after 4 weeks. Differences in VAS scores in the other time intervals and entire values of VAS were considered secondary outcomes. Comparisons were made among the groups (α = 0.05). RESULTS IS showed the highest VAS value difference between baseline and 4 weeks (mean ± SD: 3.7 ± 2.2), differing significantly from placebo (2.3 ± 1.7) and Ca/PO4/F- varnish (2.6 ± 2.0). Ca/PO4- /F- varnish did not differ from placebo. In all time intervals, VAS values of all groups were significantly lower than the baseline value, without differences among groups. For the long-term differences in VAS values (3 and 6 months), the IS exhibited significantly higher values than Ca/PO4- /F- varnish. CONCLUSIONS The IS was the most efficacious product for reducing DH, whereas Ca/PO4- /F- varnish did not differ from placebo. Registered in ClinicalTrials.gov (NCT04591444).

Nickel composites doped by chromium and calcium fluoride were produced by powder metallurgy. The friction coefficient of the samples containing 20% of the CaF2 was lower at elevated temperatures (600 °C) than the friction coefficient for the Ni-50%NiCr(80/20) composite (0.14 vs. 0.20). Sample surfaces were analyzed by the scanning electron microscope (SEM). EDS analysis proved tribofilm formation on the surface of the sample with CaF2 addition. A laser confocal microscope (LCM) was used to investigate the surface condition of the counter-sample after wear tests. The presence of the tribofilm reduced the wear of the frictional pair, and because of that the wear tracks were smooth. Tribofilm limited the abrasive wear and ploughing. Therefore, the tribofilm protected the sample and counter-sample from wear.

The use of materials requires adjusting their features to current applications/needs. In crystallization, the production methods leading directly to the product with pre-determined characteristics are being sought. The research focuses on the abilities of “shaping” the solid product (CSD, shape, form, etc.) and is based on experimental work carried out in the ultrasound (US)-assisted Koflo static mixer (STM). As the model reaction calcium fluoride precipitation has been used as a “common denominator” that complements the previous authors’ studies, providing comprehensive knowledge and a more general look at the mentioned problem. It has been shown that it is possible to obtain crystals with the desired characteristics; however, one should be aware of the used reactors’ limitations. The conscious selection of operating conditions, as well as US parameters (if they are used), is also essential. It has been revealed that the introduction of US to the STM only affects the turbulence intensity, but it doesn’t change the mixing profile. The kinetics of crystallization remain unchanged, but crystals are subjected to greater attrition. In the stirred tank reactors, one might significantly improve the homogeneity of the unit mixing distribution by the selection of the relative input power εrel and, thus, affect the kinetics of crystallization.

The current technology of leaching low-grade scheelite with sodium hydroxide or sodium carbonate has the disadvantages of large leaching reagent dosage and low leaching efficiency of tungsten. In order to extract scheelite efficiently, the kinetics of low-grade scheelite leaching with a mixture of sodium phosphate and sodium fluoride was investigated. In this study, the effects of temperature, phosphate concentration, and fluoride ion concentration on the leaching rate of tungsten were investigated. Our results showed that the leaching rate of tungsten was greatly influenced by the temperature and less affected by the concentration of phosphate and fluorine ions. The leaching process was controlled by a chemical reaction with an apparent activation energy value of 51 ± 0.2 kJ/mol. The apparent reaction orders with respect to phosphate and fluorine ions were 0.49 and 0.11, respectively. The reaction product calcium fluorophosphate was a loose, rod-like crystal, which would not tightly wrap on the surface of scheelite to prevent the diffusion process. The leaching kinetics of low-grade scheelite was in accordance with the shrinking core model, and the corresponding kinetic equation was also established.

Orientador: Lívia Maria Andaló Tenuta Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba Resumo: O benefício no controle da cárie dentária da aplicação tópica profissional de flúor (ATPF), quer seja na forma de gel ou verniz, é bem estabelecido e resulta da formação de uma concentração elevada de flúor (F) nas superfícies dentárias. Embora in vitro a concentração de F formada no esmalte após o uso de gel ou verniz fluoretado seja semelhante, desconhece-se a capacidade de retenção de F no esmalte, in vivo, e seu efeito enriquecendo o biofilme dental com F. O objetivo deste estudo foi comparar a capacidade do F gel (F-gel) e do verniz fluoretado (VF) de formar depósitos de F no esmalte e avaliar sua liberação para o biofilme dental em função do tempo. Os voluntários (n=51) foram randomizados em três grupos experimentais: 1. Grupo controle negativo: nenhuma intervenção; 2. Grupo VF: aplicação de VF (NaF a 5% - Duraphat®) por 24 h; 3. Grupo gel: aplicação de F-gel (flúor fosfato acidulado em gel a 1,23%, DFL®) por 4 min. Amostras de esmalte dental foram obtidas de incisivos superiores pela técnica de microbiópsia ácida e utilizadas para determinação da concentração de F no esmalte antes da aplicação dos produtos, imediatamente após a remoção do F-gel e VF e após 7 e 28 dias. Biofilme dental formado sobre os dentes foi coletado antes da aplicação dos produtos e após 3, 7, 14 e 28 dias, para determinação da concentração de F na porção fluida e sólida do biofilme. A concentração do íon F no esmalte dental e nas amostras de biofilme foram determinadas por eletrodo específico. As variáveis resposta foram analisadas estatisticamente considerando um delineamento fatorial, com tratamento e tempo como fatores, com nível de significância de 5%. Na avaliação da concentração de F no esmalte, houve interação significativa entre os fatores tratamento e tempos de coleta; no grupo controle, não foi encontrada diferença entre os tempos de coleta, mas para os grupos F-gel e VF, aumento significativo da concentração de F no esmalte foi observado imediatamente após os tratamentos. Esse aumento permaneceu significativamente mais alto do que o valor inicial até 7 dias para o grupo VF. Não houve diferença entre os tratamentos nos diferentes tempos de coleta, exceto imediatamente após as aplicações de F-gel e VF, quando esses grupos apresentaram concentrações de F no esmalte significativamente maiores do que o controle negativo, sem diferença entre si. Na avaliação da concentração de F no biofilme, não houve interação entre os fatores tratamento e tempos de coleta. Não houve diferença significativa entre os tratamentos na concentração de F no fluido do biofilme. Na parte sólida o efeito de tratamento foi significativo, com o grupo F-gel diferindo significativamente do grupo controle. Os resultados confirmam que F-gel e VF tem a mesma capacidade de formar F no esmalte e sugerem que seu efeito de longo prazo seja devido a um diminuto enriquecimento do biofilme dental com F Abstract: The benefit of the professional topical application of fluoride (ATPF), either as gel or varnish, for caries control is established and results from the formation of a high concentration of fluoride (F) on dental surfaces. Although in vitro the concentration of F formed in the enamel after the use of fluoride gel or varnish is similar, its retention in vivo, as well as its capacity to enrich dental biofilm with F is unknown. The objective of this study was to compare the capacity of F gel (F-gel) and fluoride varnish (VF) to form F deposits in the enamel and to evaluate their release to the dental biofilm with time. The volunteers (n=51) were randomized into three experimental groups: 1. Negative control group: no intervention; 2. Group VF: application of VF (NaF at 5% - Duraphat®) for 24 hours; 3. Group gel: application of F-gel (acidulated phosphate fluoride at 1.23%, DFL®) for 4 minutes. Samples of dental enamel were obtained from upper incisors using the acid microbiology technique and used to determine the concentration of F in the enamel before the application of the products, immediately after the removal of the F-gel and VF and after 7 and 28 days. Dental biofilm formed on the teeth was collected before application of the products and after 3, 7, 14 and 28 days, to determine the concentration of F in the fluid and solid portion of the biofilm. The concentration of F ion in the dental enamel and in the biofilm samples was determined by a specific electrode. Response variables were statistically analyzed considering a factorial design, with treatment and time as factors, with significance level of 5%. In the evaluation of the F concentration in the enamel, there was a significant interaction between the treatment factors and collection times; in the control group, no difference was found between the collection times, but for the F-gel and VF groups, a significant increase of F concentration in the enamel was observed immediately after the treatments. This increase remained significantly higher than the initial value up to 7 days for the VF group. There was no difference between the treatments at the different collection times, except immediately after the F-gel and VF applications, when these groups had F concentrations in the enamel significantly higher than the negative control, with no difference between them. In the evaluation of the concentration of F in the biofilm, there was no interaction between the treatment factors and the collection times. There was no significant difference between the treatments in the concentration of F in the biofilm fluid. In the biofilm solids, the treatment effect was significant, with the F-gel group differing significantly from the control group. The results confirm that F-gel and VF have the same ability to form F in the enamel and suggest that its long-term effect is due to a small enrichment of the dental biofilm with F Doutorado Cariologia Doutora em Odontologia

Orientador: Cínthia Pereira Machado Tabchoury Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba Resumo: A reatividade do fluoreto com o esmalte com lesão de cárie é potencializada pelo tamponamento da solução de reação, mas não é conhecido se o mesmo ocorreria com a dentina e se o efeito dose-resposta em relação à concentração de fluoreto seria mantido diante do tamponamento. Assim, objetivou-se avaliar o efeito do tamponamento na reatividade de soluções fluoretadas (SF) com a dentina, com lesão de cárie artificialmente induzida. Foram conduzidos dois experimentos in vitro, nos quais foram utilizados blocos de dentina radicular bovina. A lesão de cárie foi induzida pela imersão dos blocos (4x4x2 mm) em solução desmineralizante e, em seguida, os blocos foram selecionados e aleatoriamente distribuídos nos respectivos grupos de tratamento (n=12). O primeiro experimento avaliou o efeito do tamponamento de SF, com diferentes pH, na reatividade do fluoreto com a dentina com lesão de cárie, a partir de um delineamento fatorial 2 x 4, cujos fatores sob avaliação foram tamponamento em 2 níveis (com ou sem tampão histidina) e o pH das SF (226 µg F/mL) em 4 níveis (5,0; 5,5; 6,0 e 6,5). O segundo experimento avaliou o efeito do tamponamento na reatividade de SF, com diferentes concentrações de fluoreto, com a dentina com lesão de cárie, e envolveu um delineamento fatorial 2 x 4, sendo o tamponamento em 2 níveis (com ou sem tampão histidina) e a concentração de fluoreto em 4 níveis (113, 226, 452 e 904 µg F/mL). Nos 2 experimentos, os controles foram água purificada e histidina 0,1 M, e a reação dos blocos dentais com as soluções de tratamento ocorreu sob agitação, por 10 min. Em cada experimento, o pH das soluções foi determinado antes e após a reação, sendo o ?pH (pHfinal-pHinicial) analisado pelos testes Kruskal-Wallis e Mann-Whitney e as concentrações (µg F/cm2) de fluoreto fracamente ("CaF2") e firmemente ligado (FA) formados foram analisadas por ANOVA two-way. O nível de significância foi 5%. No experimento I, observou-se efeito significativo do tamponamento, mas não do pH ou da interação tampão x pH. O tamponamento aumentou significativamente as concentrações de "CaF2" (p

Orientador: Jaime Aparecido Cury Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba Resumo: O efeito anticárie do verni fluoretado é baseado em evidências. No entanto, não há consenso sobre quanto tempo o verniz aplicado deve permanecer sobre os dentes antes de ser mecanicamente removido. O objetivo do presente estudo clínico randomizado e controlado (ClinicalTrials.gov: NCT02486458) foi avaliar in vivo o efeito do tempo de manutenção do verniz sobre os dentes na concentração de fluoreto no esmalte e no biofilme dental. Voluntários (n=51, idade 18-30) foram randomicamente alocados em três grupos (n=17): Controle (sem aplicação de verniz); Verniz-4h e Verniz-24h (aplicação de verniz Duraphat® sobre todas as superfícies dos dentes após uma profilaxia dental e remoção mecânica após 4 e 24 h, respectivamente). As variáveis de resposta estudadas foram a concentração de fluoreto no esmalte e no biofilme dental (fluido e sólidos) em função do tempo decorrido desde a aplicação do verniz. Para análise do fluoreto no esmalte foram feitas biópsias ácidas em regiões distintas dos incisivos centrais superiores antes da aplicação (baseline), imediatamente após a remoção do verniz e após 7 e 28 dias da aplicação do verniz. O biofilme foi coletado antes (baseline) e após 3, 7, 14 e 28 dias da aplicação do verniz para análise do fluoreto no fluido e nos sólidos. Os voluntários ficaram 24 h sem escovar os dentes antes de cada coleta de biofilme e nesse período utilizaram goma de mascar açucarada para padronizar o consumo de sacarose. A concentração de fluoreto nas amostras de esmalte e biofilme foi determinada por meio de eletrodo íon-específico. Os resultados foram analisados por ANOVA - 2 vias considerando os fatores tratamento (Controle, Verniz-4h e Verniz-24h) e tempo (antes da aplicação (baseline) e após a remoção do verniz e nos tempos estabelecidos para as biópsias do esmalte e coletas de biofilme), seguido pelo pós-teste de Tukey. Para a concentração de fluoreto no esmalte foi observado efeito significativo para os fatores tratamento e tempo e sua interação (p 0,05). Conclui-se que um maior tempo de manutenção do verniz aplicado sobre a superfície dentária aumenta a reatividade do fluoreto com o esmalte, porém sem reflexo na concentração de fluoreto no biofilme Abstract: The anticaries effect of fluoride varnish is based on evidence. However, there is no consensus about the time that varnish should be maintained on enamel surfaces without it being mechanically removed. The aim of this randomized controlled clinical trial (ClinicalTrials.gov: NCT02486458) was to in vivo evaluate the effect of the maintenance time of the applied varnish in the fluoride concentration on enamel and dental biofilm. Volunteers (n=51, ages 18-30) were randomly allocated in three groups (n=17): Control (no varnish application) and groups Varnish-4h and Varnish-24h (varnish (Duraphat®) application onto every dental surface after a dental prophylaxis and mechanical removal after 4 and 24 h, respectively). The response variables studied were the fluoride concentration on the enamel and dental biofilm (fluid and solids) as a function of the time elapsed since the application of the varnish. For the analysis of the fluoride in the enamel, etching acid biopsies were made in different regions of the upper central incisors prior to the varnish application (baseline), immediately after the removal of the varnish and after 7 and 28 days of the application of the varnish. Biofilm was collected before and after 3, 7, 14 and 28 days of the varnish application for fluoride analysis in fluid and solids. The volunteers stayed without brushing their teeth for 24 h before each biofilm collection and in that period they used sugary chewing gum to standardize the consumption of sucrose. Fluoride concentration on enamel and biofilm samples was determined through ion specific electrode. Results were analyzed through ANOVA ¿ Two way considering treatment factor (Control, Varnish-4h e Varnish-24h) and time (prior to application (baseline) and after the varnish removal and on other established times for the collections of biofilm and enamel samples), followed by Tukey¿s post hoc test. For enamel¿s fluoride concentration a significant effect was observed for the treatment and time factors and their interaction (p 0.05). It concludes that a longer maintenance time of the applied varnish on the dental surface increases fluoride¿s reactivity with enamel, but without any reflexes in biofilm¿s fluoride concentration Doutorado Cariologia Doutor em Odontologia

One mechanism of action for the anticaries effect of topical fluoridation is through precipitation of CaF2. In this in vitro study energy-dispersive x-ray spectroscopy (EDX) is used as a semiquantitative method to detect enamel fluoride-precipitation under the influence of acidic and neutral pH-value and absence or presence of a salivary pellicle. Crowns of 30 human caries-free third molars were quartered into four specimens and the enamel surface ground flat and polished. Two specimens each were stored in human saliva (120 minutes pellicle formation). Teeth were randomly allocated into 6 treatment groups: NaF_a (experimental acidic sodium fluoride; 12500 ppmF(-), pH 4.75); NaF_n (experimental neutral sodium fluoride; 12500 ppmF(-), pH 7.0); GB_a (acidic gel base; 0 ppmF(-), pH 4.75); GB_n (neutral gel base; 0 ppmF(-), pH 7.0); AmF-NaF_a (experimental acidic amine/sodium fluoride; 12500 ppmF(-), pH 4.75); EG_a (acidic amine/sodium fluoride; Elmex Gelee, CP-GABA GmbH; 12500 ppmF(-), pH 4.75). Each gel was applied for 60 seconds to one specimen with and one specimen without pellicle. Two specimens served as controls (no gel, without/with pellicle). Atomic percent (At%) of O, F, Na, Mg, P, Ca was measured by EDX. Delta At% and Ca/P-ratios were calculated. EDX could semi-quantify superficial enamel fluoride-precipitation. Only specimens treated with acidic fluoride gels showed fluoride-precipitation, a salivary pellicle tended to decrease At%F.

Improving the cementitious activity and volume stability of steel slag by thermal reconstruction is an innovative method for efficient utilization of steel slag. In this study, different amounts of CaF2 and CaSO4 were added to steel slag as a mineralizer based on the determining admixtures needed for the reconstruction reaction, and the effects of CaF2 and CaSO4 on the cementitious activity and volume stability of the reconstructed steel slag were investigated. The results show that when the CaF2 content is increased to 5 wt%, the cementitious activity index of the reconstructed steel slag gradually increases to 92%, which is 12% higher than the first level technical requirement specified by the national standards, and the free CaO (f - CaO) and MgO (f-MgO) contents gradually decrease to 0.35 and 0.13 wt%, respectively. With increasing CaSO4 content, the cementitious activity index first increases and then decreases, while the contents of f -CaO and f-MgO show the opposite trend. When the CaSO4 content is 2 wt%, the activity index is 105%,which is 25%higher than the first level technical requirement specified by the national standards, and the f -CaO and f-MgO contents reach minima of 0.44 and 0.35 wt%, respectively.

Context: Pit and fissure sealants (PFSs) are the most effective preventive materials in dentistry. Secondary caries around the sealed pits and fissures at the material–tooth interface and the wear of the material remains the common problems. To address these problems, efforts have been made by incorporating zinc oxide (ZnO) and calcium fluoride (CaF2) nanoparticles (NPs) into the sealants to develop caries-inhibiting and stress-bearing sealants. Aim: Evaluation of antibacterial and mechanical properties of PFS containing ZnO and CaF2 NPs. Settings and Design: This was an in vitro study. Materials and Methods: A total of 196 fissure sealant samples were divided into six test groups and a control group. The test group samples were prepared by incorporating two concentrations (0.5 wt% and 1 wt%) of ZnO and CaF2 NPs into the sealants. The antibacterial activity was evaluated by direct contact test; compressive and flexural strengths were evaluated by a universal testing machine. Statistical Analysis Used: Statistical analysis was done by one-way ANOVA and post hoc Tukey test. Results: Sealants containing 1 wt% ZnO and CaF2 NPs and their mixture exhibited significantly higher antibacterial activity against Streptococcus mutans and Lactobacillus acidophilus when compared to control group (P < 0.001). Samples with ZnO NPs exhibited similar mechanical properties as conventional sealant (control group); however, the samples with CaF2 NPs showed inferior mechanical properties (P < 0.05). Conclusion: The observations of the study infer that sealants containing 1 wt% ZnO and CaF2 NPs and their mixture exhibited superior antibacterial activity. The mechanical properties of samples containing ZnO and mixture of ZnO and CaF2 particles remained comparable to the conventional sealants.

A powder metallurgy process was used to produce high temperature self-lubricating composites based on Ni, with varying content of calcium fluoride (10 wt.% and 20 wt.%). The wear properties of the samples were investigated by a pin-on-disc test at elevated temperature, up to 600 °C. Aside from standard techniques for the sample characterization, confocal microscopy and micro-Raman spectroscopy were used for the first time for this type of sample. These methods were used to examine the changes in topography and to detect the distribution of the tribofilm on sample surfaces. The addition of solid lubricant particles decreased the coefficient of friction and improved the tribological properties, because of the tribofilm which formed on sample surfaces.

The topical fluoride treatment of teeth can lead to a formation of CaF2-like material, which is considered to play a significant role in caries prevention . Different types of fluoride sources are applied. The aim of this study was to analyse the in vitro fluoridation effect of the lesser known organic fluoride compound nicomethanol hydroflu oride (NH) regarding fluoride accumulation and morpholog ical changes on dental enamel surfaces. Materials and Methods: The fluoridation effect was investigated by scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDX) after treatment with fluoride solutions at a concentration of 1350 ppm F - and a pH value of 5.5. NH was tested against inorganic sodium fluoride (NaF) as reference. Fluoridation was done on pellicle-free and pellicle-covered enamel. Results: Formation of globular CaF2-like material was observed for both fluoride types . However, NH led to considerably higher calcium fluoride accumulation on the enamel surface as shown by both EDX and SEM. The globule diameters varie d between 0.2 and 0.8 µm. Cross -sectional analysis revealed that the globular precipitates lay directly on the enamel surface; only the very surface-near volume was affected. No statistically significant difference of the fluoridation effect was measured with vs without saliva pre-treatment. Conclusion: The experiments showed a 6 times greater F - surface uptake on dental enamel with NH compared to sodium fluoride, thus suggesting an important role of NH during reminerali zation phases , fostering equilibrium between de- and reminerali zation.

International audience; The CaCl$_2$-CaF$_2$-CaO phase diagram was investigated in the CaO low region (

Calcium carbonate (CaCO3) is frequently added to polyethylene (PE) as a filler to reduce costs. An alternative to CaCO3, calcium fluoride (CaF2) was proposed in this research. PE/CaCO3 and PE/CaF2 composites in a wide composition range (0–60 wt.%) were prepared through a parallel twin screw extruder. Results indicated better interaction of CaF2 with PE matrix which improved samples yield stress. Statistical analysis showed the filler type was more influential factor on the yield stress while filler loading was not a statistically significant one. In contrast, crystallinity was strongly depended on the filler loading. The dynamic mechanical and rheological investigations revealed that PE/CaF2 composites had higher stiffness at ambient temperature and possessed lower viscosity below 40 wt.% of filler loading compared to PE/CaCO3 which could reduce the processing cost. Therefore, regarding its low price and good functional properties, CaF2 can be a promising alternative to CaCO3.

Preparation and synthesis of luminescent materials has a special interest in medicine, industry and research due to the wide variety of applications offered by phosphors. In this study, pellets of a mixture of CaF2 and Tm2O3 which were pressed and thermally treated up to 600 °C were prepared in air. Combined SEM (scanning electron microscopy), EDX (energy dispersive X-ray analysis) and CL-RGB (cathodoluminescence red-green-blue) microanalysis and, complementarily spectral CL analysis of this phosphor were performed. EDX analysis showed that the activator was homogeneously distributed in the prepared specimens. The additional CL emission can be attributed to the properties of some luminescent centers that were apparently created during the annealing. In addition, it seems that other trapping centers were created by new structural defects during the preparation process in the CaF2 lattice. The combined techniques SEM/EDX/CL-RGB have confirmed their capabilities in the characterization of the prepared materials. This contribution provides a process and characterization methods used in the fabrication and characterization of a phosphor that can also be used to optimize the luminescent emission of other similar synthetic materials with rare earth oxides as activators., This work has been partially supported by the Spanish Ministry of Economy and Competitiveness (MINECO) under Grant FIS2015-64793-C02.

Introduction: Fluoride toothpastes are a major reason for the decline in dental caries globally. For fluoride toothpaste to be effective, an adequate amount of Total Soluble Fluoride (TSF) must be available in the toothpastes. Aim: To determine and compare the Total Fluoride (TF), TSF and pH among various toothpaste brands. Materials and Methods: An in-vitro study was conducted during October 2019 on 20 toothpaste samples, which belonged to four groups namely, herbal toothpastes group, nonherbal toothpastes group, medicated toothpastes group and kids toothpastes group. Analysis of the samples was done at the Department of Environmental Engineering Laboratory, National Institute of Technology, Surathkal, Karnataka, India. The TF and the TSF concentration was determined using fluoride ion electrode. The pH was determined using pH meter. Statistical analysis was performed using Statistical Package for Social Sciences (SPSS version 19.0). Analysis of variance (ANOVA) was used by Tukey’s post-hoc test to determine the difference between groups. The level of significance was kept at 0.05. Results: The results showed that there was a significant difference between the toothpaste types for mean TF concentration (p=0.004). The post-hoc test showed that there was a significant difference between herbal and nonherbal toothpastes (p=0.041) where the mean TF concentration for nonherbal toothpastes was 1095.20 ppm when compared to herbal toothpastes was 704.40 ppm. The results showed that there was a siginificant difference between the toothpaste types for Mean TSF concentration (p

15 pags., 12 figs., The emission characteristics of a laser-ablated calcium fluoride CaF plasma have been investigated using time and space optical emission spectroscopy. The plasma-plume was produced by focusing 266 nm, 15 ns pulses from a Nd: YAG laser on a calcium fluoride crystal substrate placed in a vacuum chamber. The emission observed in the plasma region is due to electronic relaxation of excited neutral Ca and F, ionic fragments Ca, Ca and F and molecular features of CaF (AΠ- XΣ, BΣ- XΣ and CΠ- XΣ) band systems. Plasma species were analyzed both as a function of the delay from the laser pulse incidence and location from the target surface. Spectroscopic diagnostics were employed to estimate time-resolved electron densities, electron temperatures and velocity expansion of different species. The results show a faster decay of the continuum emission, ionic F, Ca, Ca, F species than in the case of neutral Ca atoms and molecular species of CaF. Different excitation temperatures were measured by comparing Ca and F atomic/ionic Saha-local thermodynamic equilibrium (LTE) spectra with experimental ones at various delay times after the ablation event. Vibrational temperatures of CaF were assessed from the temporal analysis of the AΠ - XΣ Δv = 0 band sequence molecular emission. We observed a non-equilibrium plasma although the plasma is found to maintain partial LTE., This research was supported by the Spanish State Research Agency (AEI) and the European Regional Development (FEDER) through Projects PID2019-104124RB-I00/AEI/10.13039/501100011033 and PID2019-106125GB-I00/AEI/10.13039/501100011033; the European H2020 IPERION HS Project (Integrated Platform for the European Research Infrastructure ON Heritage Science (GA 871034, WP5)); TOP Heritage-CM (S2018/NMT-4372) project from the Community of Madrid and with the support of Plataforma Temática Interdisciplinar of CSIC “Patrimonio Abierto: Investigación y Sociedad” (PTI-PAIS).

We experimentally demonstrate, for the first time to our knowledge, that upconversion pumping can be employed with a 1064-nm fiber laser to achieve tunable laser operation with 8 at. % T m 3 + : K Y 3 F 10 crystal near 1.9 µm, in addition to the previously explored upconversion pumping of the 2.3-µm laser transition. Two different sets of cavity optics were used to investigate lasing at 1.9 and 2.3 µm, corresponding to the laser transitions 3 F 4 − 3 H 6 and 3 H 4 − 3 H 5 , respectively. In the case of the 3 F 4 − 3 H 6 laser transition, an x-cavity laser oscillator was constructed with a 2.3% output coupler and as high as 142 mW of output power was obtained at an incident pump power of 1.9 W at 1064 nm. Tunable laser operation could be obtained between 1849 and 1994 nm by using C a F 2 and suprasil prisms. The highest slope efficiency of 29% with respect to average absorbed pump power was obtained with a 5.5% output coupler. For the case of 1.9 µm lasing, it was further demonstrated that the nonlinear absorption of the crystal at 1064 nm depends on the intracavity laser intensity as well as the pump intensity. The 3 H 4 − 3 H 5 laser transition was also investigated with the same crystal in a z-cavity configuration under upconversion pumping, giving as high as 130 mW of output power at the central wavelength of 2344 nm with 1.6 W of incident pump power.

The powder of CaF2 has been proposed as a practical reference for the quantitation of Ca and F in low energy ion scattering (LEIS) analysis. It is chemically inert, easy to clean, and inexpensive. LEIS is extremely surface sensitive. Thus, in contrast to surface analytic techniques such as x-ray photoelectron spectroscopy and secondary ion mass spectroscopy, the surface termination of a sample is clearly reflected in the LEIS results. It is, thus, unlikely that in LEIS, the F/Ca ratio for CaF2 is 2.0. This paper supports the reliability of the CaF2 powder reference by evaluating the calcium and fluorine atomic surface concentrations, roughness factor and shows that the surface termination of the powder is the same as that of CaF2(111). The CaF2 samples are treated by annealing at 725 K and measured at 625 K. The presented spectra are practically free of contamination. Ion scattering by LiF (001), an evaporated Ca layer, and a Cu foil are used as basic references for Ca and F. The atomic sensitivity factors and the relative sensitivity factors have been determined for F, Ca, and Cu (3 keV He+, 145 degrees). The F/Ca atomic ratio is found to be the same (2.3 +/- 0.1) for CaF2(111) and its powder. For the powder, the Ca and F signals are reduced by a factor of 0.77 +/- 0.03 in comparison with those for the single crystal.

In this study, the anaerobic quartz sand fixed biofilm reactor containing Cupriavidus sp. W12 was established to simultaneously remove calcium (Ca

Fluoride contamination is a major problem in wastewater treatment. Metaettringite (which has previously shown enhanced anion adsorption) was investigated as a possible adsorbent to remove fluoride from low-concentration solution (25 mg-F/L). The fluoride removal properties of ettringite and metaettringite were first compared at pH 10, and metaettringite was found to be more effective. The dominant reaction mechanism for fluoride adsorption in metaettringite was found to be recrystallization of metaettringite by rehydration; this was accompanied by precipitation of calcium fluoride. The adsorption kinetics followed the pseudo-second order model. Metaettringite was also able to remove fluoride effectively in low pH environment (i.e., at pH 3.5). The influence of coexistence of sulfate ions in solution on the fluoride removal performance was investigated, and a small decrease in performance was noted. The residual fluoride concentrations obtained with higher doses of metaettringite were lower than those specified by the Japanese effluent standard (non-coastal areas: 8 mg-F/L; coastal areas: 15 mg-F/L). The fluoride removal capacity of metaettringite was compared with those of other solid materials. The observed maximum capacity was 174.7 mg-F/g-metaettringite. In the case of high fluoride concentration solution, the main removal mechanism will be changed to calcium fluoride precipitation. In general, metaettringite is regarded as promising material for fluoride removal in wastewater treatment.

Entwicklung alternativer Entschwefelungsmittel und eines Zugabeverfahrens in der Gießereiindustrie zur nachhaltigen Substitution von Magnesium Diese Arbeit behandelt die Entwicklung eines alternativen Entschwefelungsmittels für den Einsatz in der Gießereiindustrie, sowie die Ermittlung eines dafür geeigneten Einbringungs- verfahrens, unter Berücksichtigung einer maximalen Behandlungszeit von 10 Minuten und einer zu behandelnden Schmelzmasse von 2-10 Tonnen. Diese Entwicklung ist von Interesse, da der Markt des bisher zu Entschwefelung eingesetzten Magnesiums sehr volatil ist und die Abhängigkeit von China, ein potenzielles Problem für die Versorgungssicherheit darstellt. Die Entschwefelung von Eisen mit den unterschiedlichsten Entschwefelungsmitteln und Einbringungsverfahren stellt, gerade im Bereich der Stahlerzeugung, ein sehr gut erforschtes Gebiet dar. Das in der Gießereiindustrie eingesetzte Kupolofeneisen hebt sich von dem in der Stahlindustrie eingesetzten Roheisen besonders durch den hohen Siliziumgehalt ab, welcher die Entschwefelungswirkung vieler Entschwefelungsmittel stark eingeschränkt. Dies macht es schwer, die zur Erzeugung von GJS und GJV geforderten Endschwefelgehalte von 150ppm respektive 200ppm, mit den bereits bekannten Magnesiumalternativen einzuhalten. Im Rahmen dieser Arbeit, wurden Labor- Technikums- und Industrieversuche geplant, durchgeführt und ausgewertet. Die erfolgversprechendsten ermittelten Entschwefelungsmit- tel konnten in einem Industrieversuch erfolgreich getestet werden., Sustainable Substitution of Magnesium in Foundries by Developing an Alternative Desulphurization Process In this thesis the developement of an alternative desulfurization agent for foundary use, as well as different insertion methods for said agent are discussed, considering a maximum treatment time of 10 minutes and a ladle mass of 2 - 10 tons. This research is of deeper interest, due to the market being very volatile, due to the resulting dependency on China. In steelmaking the desulfurization of iron with different agents and delivery methods is well developed. Especially due to its higher silicon content the cupola iron used in foundries differs from pig iron used in steelmaking, which limits the desulfurization capability of commonly used magnesium replacements and makes it difficult to reach the specified sulfur content of 150ppm respectively 200ppm needed for the production of SGI and CGI. During this thesis, experiments in three different stages: laboratory, prototype and industrial, were planed, performed and evaluated. The most promising of the developed agents were successfully tested in industrial scale.

Calcium fluoride formed by the reaction between ammonium bifluoride and calcium chloride was investigated as a dominating matrix for quantitative analysis by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Transformation from a solid sample to the calcium fluoride-based matrix permitted quantitative analysis based on calibration standards made from elemental standards. A low abundance stable calcium isotope, i.e. 44Ca+, was monitored as the internal standard for quantitative analysis by LA-ICP-MS. Correlation coefficient factors for multiple elements were obtained with values over 0.999. The results for multiple elements in a certified reference material of soil (NIST SRM 2710a) agreed with the certified values in the range of expanded uncertainty, indicating the present method was valid for quantitation of elements in solid samples.