MgF2 Nanoparticles Research Articles

Preparation of highly transparent mid-infrared MgF2 ceramics by low-pressure hot pressing

The co-precipitation approach was successfully used in this investigation to produce MgF2 nanoparticles. The effects of various heat treatments on the particle size and morphology of MgF2 nanoparticles were systematically investigated. Based on the experimental results, the powder calcined at 500 °C, having crystallites size that are typically between 80 and 120 nm in size, was identified as the optimal sample. This calcined powder was subsequently used to produce polycrystalline MgF2 ceramics through hot pressing (HP). It was also investigated how the characteristics of MgF2 ceramics were affected by low-pressure hot pressing. The results demonstrated that the optimal transmittance of 95.8 % was achieved at a pressure of 30 MPa and a hot-pressing temperature of 800 °C. Furthermore, the dielectric constant (εr), Q × f value, Vickers hardness (HV), and fracture toughness (KIC) of the samples produced at 30 MPa and 800 °C were evaluated. The dielectric constant and Q × f value of MgF2 ceramics, measured at 13.6231 GHz, were found to be 5.2996 and 114534 GHz, respectively. The Vickers hardness was measured at 5.21 ± 0.42 GPa, and the fracture toughness was determined to be 0.842 ± 0.067 MPa m1/2.

Simultaneous fluorination and carbonation to approach a high infrared transparent magnesium fluoride

In this research study, magnesium fluoride nanoparticles were successfully produced by the fluorination and carbonation method. MgF2 nanoparticles were calcined at temperature of 100, 300, 400, 500, 600, 640, and 680 °C. Also, polycrystalline magnesium fluoride ceramics were prepared using a hot-pressing process from calcined powders. The optical, structural, and mechanical characteristics of the magnesium fluoride samples were then investigated. The X-ray diffraction proved that magnesium fluoride nanoparticles were formed with a single-phase structure and no impurities. By using simultaneous fluorination and carbonation technique, crystalline MgF2 nanoparticles with a particle size of 50–60 nm were synthesized at a minimum temperature of 100 °C. Increasing the calcination temperature led to the evaporation of the volatile products and increased the crystallinity and particle size of MgF2 nano-particles. The optimal calcination temperature of 640 °C created a ceramic MgF2 with a hardness of 560 HV, and considerable relative density of 100%, and a high transmittance of over 90% in the 3.2–5.5 μm range. The obtained results, thus, revealed that the transparency of MgF2 ceramics was a function of the porosity and the grain size distribution. The microstructure of hot-pressed MgF2 confirmed a Gaussian grain size distribution in the range of 100–1000 nm, contributing to the enhancement of densification. An intra-granular fracture occurred in magnesium fluoride, which was related to the fine-grained structure of MgF2.

Fabrication of omnidirectional broadband dual-functional coating with high optical and self-cleaning properties for photovoltaic application

Escalating the transmitted irradiation, which diminishes due to the undesirable reflection at the interfaces and the surface dirt, requires a simultaneous functioning of antireflection and self-cleaning coating for photovoltaic modules. In this regard, an unprecedented, facile, economical, reproducible, and eco-friendly fabrication of dual-functional coatings (Anti-reflective and Self-cleaning) with high optical and photocatalytic properties is demonstrated. Highly crystalline MgF2 and TiO2 nanoparticles are successfully synthesized by the solvothermal method, and these nanoparticles are utilized to develop a dual-functional coating. HR-TEM and XRD are used to analyze the synthesized nanoparticles, and FE-SEM measures the coating morphology and thickness. The established dual-functional coating exhibits a 5 % enhancement in transmittance compared to uncoated glass in the 380–1100 nm wavelength range. The developed coating also shows high omnidirectional broadband antireflective property with 5–33 % net enhancement in the transmittance in the angle of incidence from 10 to 80°. The coating also exhibited good photocatalytic self-cleaning activity by degrading Methylene blue solution in 3 h with minimal loss in transmission. The bilayer dual-functional coating exhibited a net enhancement of 3.5 % in the power conversion efficiency for coated glass placed over a mini-module compared to uncoated glass positioned over a mini-module. This bilayer dual-functional coating offers enormous potential benefits and is highly conceivable for many applications.

The mechanism for tuning the corrosion resistance and pore density of plasma electrolytic oxidation (PEO) coatings on Mg alloy with fluoride addition

Here we prepared PEO coatings on Mg alloys in silicate–NaOH–phosphate electrolyte containing different concentrations of NaF addition. The detailed microstructural characterizations combining with potentiodynamic polarization and electrochemical impedance spectra (EIS) were employed to investigate the roles of fluoride in the growth and corrosion properties of PEO coating on Mg. The result shows the introduction of NaF led to a fluoride-containing nanolayer (FNL) formed at the Mg/coating interface. The FNL consists of MgO nanoparticles and insoluble MgF2 nanoparticles (containing rutile phase and cubic phase). The increase in the NaF concentration of the electrolyte increases the thickness and the MgF2 content in the FNL. When anodized in the electrolyte containing 2 g/L NaF, the formed FNL has the highest thickness of 100–200 nm along with the highest value of x of ∼0.6 in (MgO)1-x(MgF2)x resulted in the highest corrosion performance of PEO coating. In addition, when anodized in the electrolyte containing a low NaF concentration (0.4–0.8 g/L), the formed FNL was thin and discontinuous, which would decrease the pore density and increase the coating's uniformness simultaneously.

Fluorination synthesis of MgF2 nanoparticles synthesized for manufacturing IR windows by hot-pressing

In this study, magnesium fluoride (MgF2) nanoparticles were synthesized through the fluoridation method, by dissolving magnesium chloride and hydrofluoric acid (HF) in deionized water. The influences of some parameters, including pH, concentration ratio of reactants, F:Mg mole ratio, washing method and calcination temperature were investigated on the particle size, morphology, chemical purity and phase purity of MgF2 nanoparticles. In order to study the impact of pH on the properties of MgF2 nanoparticles, different samples at pH values of 1, 5 and 9 were synthesized. The obtained results revealed that as pH value increased from 1 to 9, the morphology of MgF2 nanoparticles changed from rod to spherical shape. The effect of mole ratio of fluorine ions to magnesium ions on the MgF2 nanoparticles at three ratios of 2, 6 and 12 also demonstrated that by increment of F:Mg mole ratio, the particle size was decreased from 150 nm to 30 nm. In addition, it was figured out that by the increment of F:Mg mole ratio, the MgO phase was eliminated. Afterwards, by decreasing the HF:MgCl2 molar ratios from 0.1 to 0.03 the particle size reduced from 300 nm to 30 nm. After determining the optimal synthesis conditions, magnesium fluoride nanoparticles were calcined at 470, 530 and 600 °C. Regarding the results, the powder that was calcined at 600 °C with a particle size of about 30–40 nm was selected as the optimal sample. Ultimately, the resulting powder was sintered using hot-press (HP) at a temperature of 700 °C for 45min in the vacuum pressure of 10−3 bar. After polishing the sintered piece, its inferred (IR) transparency was over 90% in the wavelength ranges of 3–5 μm.

Optical nanocomposites containing low refractive index MgF2 nanoparticles

Nanoparticles composed of magnesium fluoride were successfully introduced into polymer matrices used for the fabrication of planar optical waveguides. Optical layers without visible scattering were successfully prepared. The transparent nanocomposites were formulated by direct mixing of modified MgF2 nanoparticles with fluorinated co-polymer matrix or acrylate monomer mixture with a help of additional solvent. An addition of MgF2 nanoparticles results in decrease of refractive index and thermo-optic coefficient of the polymer but increases substantially the optical propagation losses for planar waveguide at 1547 nm.

Synergetic effect of multiple phases on hydrogen desorption kinetics and cycle durability in ball milled MgH2–PrF3–Al–Ni composite

A new MgH2–PrF3–Al–Ni composite was prepared by ball milling under hydrogen atmosphere. After initial dehydrogenation and rehydrogenation, Pr3Al11, MgF2, PrH3 and Mg2NiH4 nanoparticles formed accompanying the main phase MgH2. The hydrogen absorption-desorption properties were measured by using a Sieverts-type apparatus. The results showed that the MgH2–PrF3–Al–Ni composite improved cycle stability and enhanced hydrogen desorption kinetics. The improvement of hydrogen absorption-desorption properties is ascribed to the synergetic effect of the in situ formed Pr3Al11, MgF2, PrH3 and Mg2NiH4 nanoparticles. This work provides an important inspiration for the improvement of hydrogen storage properties in Mg-based materials.

The Effects of Various Parameters of the Microwave-Assisted Solvothermal Synthesis on the Specific Surface Area and Catalytic Performance of MgF2 Nanoparticles.

High-specific-surface-area MgF2 was prepared by microwave-assisted solvothermal synthesis. The influences of the solvent and the magnesium precursors, and the calcination atmospheres, on the nanoparticle sizes and specific surface areas, estimated by X-Ray Powder Diffraction, N2 sorption and TEM analyses, were investigated. Nanocrystallized (~7 nm) magnesium partially hydroxylated fluorides (MgF2−x(OH)x) with significant specific surface areas between 290 and 330 m2∙g−1 were obtained. After activation under gaseous HF, MgF2−x(OH)x catalysts underwent a large decrease of both their surface area and their hydroxide, rates as shown by their 19F and 1H solid-state NMR spectra. Expect for MgF2 prepared from the acetate precursor, an activity of 30–32 mmol/h∙g was obtained which was about 40% higher compared with that of MgF2 prepared using Trifluoroacetate method (21.6 mmol/h∙g).

Enhancement in power conversion efficiency of CdS quantum dot sensitized solar cells through a decrease in light reflection

In this research, the effect of a Magnesium Fluoride (MgF2) Anti-Reflection (AR) layer was investigated in quantum dot sensitized solar cells (QDSCs). MgF2 nanoparticles with the dominant size of 20 nm were grown by a thermal evaporation method and a thin layer was formed on the front side of the fluorine-doped tin oxide (FTO) substrate. In order to study the effect of the AR layer on the efficiency of solar cells, this substrate was utilized in CdS QDSCs. In this conventional structure of QDSC, TiO2 nanocrystals (NCs) were applied on the FTO substrate, and then it was sensitized with CdS quantum dots (QDs). According to the results, the QDSCs with a MgF2 AR layer represented the maximum Power Conversion Efficiency (PCE) of 3%. This efficiency was increased by about 47% compared to the reference cell without the AR layer. The reason is attributed to the presence of the AR layer and the reduction of incident light reflected from the surface of the solar cell.

DETERMINATION OF THE REFRACTIVE INDEX OF OPTICAL CERAMICS BY USING TRANSMISSION DATA IN THE MID-WAVE INFRARED REGION

Optical ceramics are emerging materials for optical devices operating in the Mid-Wave Infrared (MWIR) spectral range. Thus determination of their refractive index is of huge importance but is still a challenging issue. In this work, a model is delivered, which highlights a simple mathematic relationship between the refractive index of an optical material and its transmittance spectrum measured by Fourier Transform Infrared Spectroscopy. Such model allows determining the refractive index of ceramics fabricated by hot-pressing of MgF2 nanoparticles. The reliability of this method has been verified on a silicon wafer taken as a reference (< 0.5%, discrepancy with data from literature on Si). Our approach can be applied to a variety of promising novel optical materials being developed.

Single layer hollow MgF2 nanoparticles as high-performance omnidirectional broadband antireflective coating for solar application

Reflection is the most disconcerting phenomenon for solar cover glass, and Omnidirectional Broadband Antireflective coating (OBAR) enhances the transmission of the solar cover glass and power conversion efficiency of the photovoltaic cell. In this connection, a facile synthesis route is adapted to develop hollow MgF2 nanoparticles using Magnesium carbonate as a precursor for the first time. Small Angle X-ray scattering (SAXS) quantifies the spatial dimensions of the nanosized substructure, and Transmission Electron Microscope (TEM) utilized to investigate the morphological information of MgF2 hollow nanoparticles. The deposition of MgF2 hollow nanoparticles on the solar cover glass results in OBAR coating and exhibits enhancement of 5.8–31.7% by varying angle of incidence ranging from 10 to 80o in the wavelength range of 400–1100 nm is a breakthrough of its kind. Moreover, the average transmittance results to be 97.88% in spectral range (400–1100 nm) and 99.2% in the visible spectrum at normal incidence. Further, OBAR coated glass encapsulated polycrystalline Si solar cell has shown >10% net increment in the efficiency compared to that of uncoated glass encapsulated device. Also, the developed OBAR coatings exhibited excellent mechanical and weather stability.

Influence of MgF2 nanoparticles in the plasma polymer fluorocarbon‐based transparent nanocomposite thin films on the surface hardness properties

AbstractIn this study, the chemical structure at the interfaces of nanocomposite thin films, consisting of MgF2 nanoparticles and a plasma polymer fluorocarbon (PPFC) matrix, was analyzed to elucidate the relationship between fluorine dispersion and surface properties. Using self‐made MgF2–carbon nanotube–polytetrafluoroethylene ternary composite sputtering targets, MgF2 nanoparticles were successfully embedded in the PPFC matrix through sputtering. The spectrometric analysis showed that the fluorine atoms transfer at the nanoparticle interface created a carbon‐rich region in the PPFC polymer matrix, resulting in higher thin film hardness. The optimized MgF2 nanoparticle/PPFC matrix thin film showed that surface hardness reached 4.32 GPa, and it also exhibited high optical transparency and water repellency. MgF2–PPFC nanocomposite thin film could be applicable to protective optical coatings for display and automotive windows.

Hybrid Nanoparticle Layers Toward Enhanced Luminescence of Phosphor Plates for White LEDs.

MgF2 porous nanoparticle-silica hybrid coating layers were utilized to enhance luminescence efficiency of phosphor plates for white light-emitting diodes (wLEDs). Silica and chemically synthesized porous MgF2 nanoparticles were sequentially deposited by spin coating on the phosphor plate with phosphor-in-glass (PiG) configuration. Microscopic investigation the hybrid film suggested intermixing of silica and porous MgF2 nanoparticles. Numerical estimation based on transfer matrix method expected a significant reduction in reflectance and enhancement of transmission spectra by the hybrid coating. In accordance, the photoluminescence intensity of phosphor plates showed a drastic improvement and quantum yield were enhanced from 30% (for bare PiG plate) to 45% (for hybrid-layer-coated PiG plate). When assembled with blue LEDs, hybrid nanoparticle coating on the PiG phosphor plates improved luminescence efficacy from 40 to 49 lm/W without deterioration of chromaticity during operation. In addition, mechanical durability of the hybrid thin film was confirmed by an abrasion test. Conformal coating of matching layer consisting of porous MgF2 nanoparticles and silica can provide an efficient route to highly luminescent white LEDs with mechanical stability.

Correlative Analysis of Specific Compatibilization in Composites by Coupling in situ X-Ray Scattering and Mechanical Tensile Testing

In this study, a bio-inspired hybrid material is investigated by in situ X-ray scattering experiments in combination with mechanical tensile testing. The material is composed of nanometer-sized spherical magnesium fluoride particles which are linked via material-specific peptide-poly(ethylene glycol) (PEG) conjugates to a semi-crystalline poly(ethylene oxide) (PEO) matrix. Mechanically relevant changes in crystal size and orientation in the PEO matrix are followed by wide angle X-ray scattering during the application of tensile stress. The amorphous phase of PEO is stabilized by the surface-engineered MgF2 nanoparticles, leading to increased Young´s modulus and tensile strength. Furthermore, small angle X-ray scattering experiments allowed the identification of a layer on the MgF2 particle surfaces, which increases in thickness with the conjugate amount and leads to suppression of the agglomeration of MgF2 nanoparticles. In conclusion, the use of selected peptide-PEG conjugates tailored to link MgF2 particles to a PEO matrix successfully mimics the biological principle of interface polymers and suggests new directions for material fabrication for bio-applications.

Tuning mechanical reinforcement and bioactivity of 3D printed ternary nanocomposites by interfacial peptide-polymer conjugates

We present a study on ternary nanocomposites consisting of medical grade poly(ε-caprolactone) (mPCL) matrix, hydroxyapatite nanopowder (nHA) and compatibilized magnesium fluoride nanoparticle (cMgF2) fillers. MgF2 nanoparticles were compatibilized by following a design approach based on the material interfaces of natural bone. MgF2-specific peptide-poly(ethylene glycol) conjugates were synthesized and used as surface modifiers for MgF2 nanoparticles similarly to the non-collagenous proteins (NPC) of bone which compatibilize hydroxyapatite nanocrystallites. Different compositions of mPCL/nHA/cMgF2 composites were blended together and processed into three dimensional (3D) scaffolds using solvent-free techniques including cryomilling and melt extrusion-based additive manufacturing. The use of two different inorganic fillers in mPCL resulted in nanocomposite materials with enhanced mechanical and biological properties. In particular, cMgF2 nanoparticles were found to be the primary constitent leading to the significant improvements in the mechanical properties of these composites. The scaffolds of the ternary nanocomposites provided the best in vitro performance in terms of osteogenic differentiation and stimulated mineralization. In summary, we demonstrated that the concept of bioinspired interface engineering facilitates the development of homogeneous ternary nanocomposites with increased processability in additive biomanufacturing. Additionally, the concept leads to scaffolds exhibiting enhanced mechanical and biological properties. Overall, these multicomponent nano-interfaced building blocks add a new group of advanced functional materials with tunable mechanical properties, degradation and bioactivity.

Magnesium Fluoride Forms Unique Protein Corona for Efficient Delivery of Doxorubicin into Breast Cancer Cells.

Background: The efficacy of chemotherapy is undermined by adverse side effects and chemoresistance of target tissues. Developing a drug delivery system can reduce off-target side effects and increase the efficacy of drugs by increasing their accumulation in target tissues. Inorganic salts have several advantages over other drug delivery vectors in that they are non-carcinogenic and less immunogenic than viral vectors and have a higher loading capacity and better controlled release than lipid and polymer vectors. Methods: MgF2 crystals were fabricated by mixing 20 mM MgCl2 and 10 mM NaF and incubating for 30 min at 37 °C. The crystals were characterized by absorbance, dynamic light scattering, microscopic observance, pH sensitivity test, SEM, EDX and FTIR. The binding efficacy to doxorubicin was assessed by measuring fluorescence intensity. pH-dependent doxorubicin release profile was used to assess the controlled release capability of the particle-drug complex. Cellular uptake was assessed by fluorescence microscopy. Cytotoxicity of the particles and the drug-particle complex were assessed using MTT assay to measure cell viability of MCF-7 cells. Results and Discussion: Particle size on average was estimated to be <200 nm. The crystals were cubic in shape. The particles were pH-sensitive and capable of releasing doxorubicin in increasing acidic conditions. MgF2 nanocrystals were safe in lower concentrations, and when bound to doxorubicin, enhanced its uptake. The protein corona formed around MgF2 nanoparticles lacks typical opsonins but contains some dysopsonins. Conclusion: A drug delivery vector in the form of MgF2 nanocrystals has been developed to transport doxorubicin into breast cancer cells. It is pH-sensitive (allowing for controlled release), size-modifiable, simple and cheap to produce.

Investigation of the Coupled Effect of Liquid and Solid Inorganic Additives on Thermal Stability and Water Retention of PFSA Composite

Here, investigation of the high-temperature water retention property of new composites, which contain perfluorosulfonic acid (PFSA) polymer as matrix, a mineral acid, and MgF2 nanoparticles as inorganic additives, is done based on structural analysis. The composite shows an improvement in the water removal temperature from 50 to 250 °C because the crystalline water molecules were attached on the surface of solid inorganic additives at 250 °C. To optimize the water retention property, the 1 wt % of sulfuric acid and 3–15 wt % of MgF2-coated glass particles in PFSA polymer composites as additives were investigated. From the Fourier transform infrared-attenuated total reflection studies of these composite membranes, two major phenomena related to structural details of PFSA polymer as a function of the polymer and the weight ratio of the solid additives are observed: (1) sulfonic acid group released the proton even with low humidity and (2) the conformation and/or the degree of the crystallinity of the poly(t...

Nano Metal Fluorides for Wood Protection against Fungi

Wood treated with nano metal fluorides is found to resist fungal decay. Sol–gel synthesis was used to synthesize MgF2 and CaF2 nanoparticles. Electron microscopy images confirmed the localization of MgF2 and CaF2 nanoparticles in wood. Efficacy of nano metal fluoride-treated wood was tested against brown-rot fungi Coniophora puteana and Rhodonia placenta. Untreated wood specimens had higher mass losses (∼30%) compared to treated specimens, which had average mass loss of 2% against C. puteana and 14% against R. placenta, respectively. Nano metal fluorides provide a viable alternative to current wood preservatives.

Dual-functional broadband antireflective and hydrophobic films for solar and optical applications

We report hydrophobic modification of a high-performance broadband antireflective (AR) film comprising mesoporous MgF2 nanoparticles. The MgF2 film demonstrates high transmission, >99% (400–800 nm) and >97% (300–1500 nm) and is hydrophilic with a water contact angle of 27°. Hydrophobic modification with a fluorosilane containing silica sol by a simple dip coating process increases the water contact angle to 130° without affecting transmittance. Hence, this hybrid layer exhibits excellent anti-reflection in a broad wavelength range (98.8% (400–800 nm) and 97.03% (300–1500 nm)), along with good water-repellence. Moreover, the layer is also environmentally and mechanically stable indicating its suitability for solar and optical applications.

Broad band antireflective coatings using novel in-situ synthesis of hollow MgF2 nanoparticles

A high performance antireflective (AR) should be a thin film with low refractive index, highly transparent, economical, and highly durable. In this paper, we present a novel synthesis of hollow Magnesium Fluoride (MgF2) nanoparticles, which is used to produce a high performance broadband antireflective coating. A formation–deformation-reformation route has been adopted to synthesize nanoparticles with hexagonal structure and cavities, which are crystalline and dispersible in any polar solvent. This facile synthesis route is a major breakthrough to achieve high performance broadband antireflective coating with an average transmittance of 98.3% in the visible range (400–800nm) and 96.2% in active solar range (300–1500nm). No significant drop in the efficiency was observed with antireflective-coated cover glass on the c-Si solar cell, whereas 6–7% efficiency loss was observed with uncoated glass. This can be a promising approach to develop high performance antireflective dielectric layer, which will enhance the overall performance of photovoltaic and solar thermal systems.