Er3+-doped CaF2 polycrystalline ceramic with perfect transparency for mid-infrared laser

Er³⁺-doped CaF₂ transparent ceramics are promising mid-infrared gain materials because of their utra-low phonon energy as well as excellent physical, chemical, and optical properties. However, existing hot-pressed and hot-formed CaF₂ ceramics are very difficult to be used in practical applications due to residual pores and weak polycrystallization, respectively. Here, we developed the high quality Er³⁺-doped CaF₂ transparent polycrystalline ceramic by single crystal ceramization. The sample exhibits obvious polycrystalline structure, good mechanical properties, perfectly transmittance, and excellent mid-infrared performance, which provides significant and wide-ranging opportunities for advanced mid-infrared gain materials.     

Ionic liquids in electrochromic devices

The ionic liquid (PYR₁₄TFSI) has proved to be the key material to make a Li-ion conducting element of a complete electrochromic device, when interposed between transparent film electrodes like WO₃ and Li-charged V₂O₅. The key features of this ionic liquid and its mixtures with LiTFSI are the excellent transparency in the visible and NIR optical regions, the good ionic conductivity and the electrochemical compatibility with inorganic Li-intercalation oxide thin film electrodes used in electrochromic devices. The higher optical contrast found during WO₃ colouration with PYR₁₄TFSI-LiTFSI, compared to that in a conventional non-aqueous electrolyte like PC-LiTFSI, was attributed to the larger inertness of the former one (no decomposition reaction at the lowest electrode potential). This highly conductive ionic liquid has been incorporated into a polymer matrix (P(EO)₁₀LiTFSI), in order to obtain a transparent solid electrolyte with high Li ion conductivity and good mechanical stability. Finally this solid PYR₁₄TFSI-P(EO)₁₀LiTFSI transparent ion conductor was interposed between the same electrodes as above in order to yield a fully solid-state, Li-ion electrochromic device. This new solid electrolyte was able to transfer reversibly a Li ionic charge between 5 mC cm⁻² and 10 mC cm⁻² from the lithium storage electrode Li_xV₂O₅ to the WO₃ electrochromic electrode in less than 100 s at room T, darkening the device from an initial 80% to a final 30% transmittance (at 650 nm). Such a device has been tested first under various constant current conditions, and later under potentiostatic control using ±2 V steps. The latter method allows not only for a faster response of the electrochromic system, but provides also an easier life stability test of the device, which withstood 2000 cycles with little changes in its optical contrast.     

Preparation of transparent PVA/TiO2 nanocomposite films with enhanced visible-light photocatalytic activity

Polymer/semiconductor oxide nanocomposite films have been intensively investigated for various applications. In this work, we reported a simple hydrothermal method to fabricate highly transparent poly(vinyl alcohol)/titanium dioxide (PVA/TiO₂) nanocomposite films with enhanced visible-light photocatalytic activity. The as-prepared PVA/TiO₂ nanocomposite films showed high optical transparency in the visible region even at a high TiO₂ content (up to 40 wt.%). The determination of photocatalytic activity by photodegradation of methyl orange (MO) and colorless phenol showed that PVA/TiO₂ nanocomposite films exhibited enhanced visible-light photocatalytic activity and excellent recycle stability. This work provided new insights into fabrication of polymer/TiO₂ nanocomposites as high performance photocatalysts in waste water treatment.     

Synthesis of highly refractive and transparent poly(arylene sulfide sulfone) based on 4,6-dichloropyrimidine and 3,6-dichloropyridazine

A highly refractive and transparent poly(arylene sulfide sulfone) (PASS) containing pyrimidine (or pyridazine) unit has been developed. The polymer was prepared by a polycondensation reaction of 4,4′-dimercaptodiphenyl sulfone (DMDPS) and 4,6-dichloropyrimidine (DCPM) (or 3,6-dichloropyridazine (DCPD)). They showed good thermal stabilities such as a relatively high glass transition temperature of 193–202 °C and a 5% weight loss temperature (T_5%) of 370–372 °C. The optical transmittance of the polymer at 450 nm is higher than 81%. The heterocycles unit and plural –S– linkages provides the polymer with a high refractive index of 1.737–1.743 at 633 nm and a low birefringence of 0.003–0.004.     

Novel high performance poly(aryl ether ketone)s based on symmetrical naphthylene isomers

Summary  Two new bisphenol monomers containing naphthylene groups were synthesized by a Friedel-Crafts acylation reaction followed by a demethylation reaction. Four naphthylated poly(aryl ether ketone)s (PANEKs) were successfully prepared via a typical nucleophilic substitution polycondensation. These PANEKs exhibited excellent properties including high T_gs (above 204^oC) and good thermal stability (the temperature at 5% weight loss in air was above 430^oC). They had improved solubility, and flexible and transparent membranes could be cast from their solutions. The good mechanical property (tensile strength of 82.2∼102.8 MPa, Young’s moduli of 2.1∼2.4 GPa, and elongation at break of 17∼31%) indicated they were strong materials. Low dielectric constant (2.8-2.9 at 1 MHz) and moisture absorptions (i<<0.45%) were also detected from the polymer films.     

High-quality N-substituted maleimide for heat-resistant methacrylic resin

A preparation procedure for colorless, transparent N-substituted maleimide of high quality which can provide heat-resistant transparent methacryl resins was developed. N-Alkylmaleimide, the alkyl substituent of which was composed of 2 to 4 carbons, is employed, giving a polymer with enhanced heat distortion temperature (HDT) because of the higher T_g. The advantages of relatively low melting points and high vapor pressure of N-alkylmaleimide can be used for the preparation of a high-quality product with purification of the monomer by distillation. N-Isopropylmaleimide (IPMI), which fulfills these requirements, is especially useful as a monomer for transparent resins. IPMI was synthesized in a high-yield using a mixture of orthophosphoric acid and orthophosphoric acid-isopropylamine salt as catalyst. IPMI, the purity of which is 99.9 wt % or above, contains 100–200 ppm of N-isopropylmaleamic acid, maleic anhydride, dimethylmaleic anhydride, solvent, and water. IPMI, which solidifies at 25.8°C, is obtained as a colorless liquid and is freely soluble in common monomers such as methyl methacrylate (MMA), styrene (St), and acrylonitrile (AN). The obtained IPMI showed excellent thermal stability, and no quality change was observed after heating for 100 h at 50°C. The copolymer of MMA and IPMI exhibited the same YI value as a measure of coloration, and almost the same transparency as the homopolymer of MMA. An increase in IPMI content in the copolymer by 1 mol % increased the polymer T_g by 0.8°C. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1055–1062, 1997     

A high temperature polymer of phthalonitrile‐substituted phosphazene with low melting point and good thermal stability

A phthalonitrile‐substituted phosphonitrilic monomer has been synthesized from phosphonitrilic chloride trimer and then polymerized with addition of 4‐(hydroxylphenoxy)phthalonitrile (HPPN). The chemical structures of the phosphonitrilic monomer and polymer were characterized by Fourier Transform Infrared spectroscopy (FT‐IR) and proton Nuclear Magnetic Resonance spectroscopy (¹H NMR). Curing behaviors and thermal stabilities of the polymer were investigated through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Analysis showed that the monomer has large processing temperature window and good thermal stability. Apparent activation energy, initial curing temperature (T_i), curing temperature (T_p), and termination curing temperature (T_f) of the phosphonitrilic polymer were explored. Dynamic mechanical analysis (DMA), glass transition temperature (T_g) were studied, and limiting oxygen index (LOI) were estimated from the van Krevelen equation, which indicates the polymer process high modulus and good flame retardance. Micro‐scale combustion calorimetry (MCC) was also used for evaluating the flammability of the polymers. Postcuring effects were explored, showing excellent thermal and mechanical properties with postcuring. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42606.     

Optical properties of transparent polycrystalline ruby (Cr:Al2O3) fabricated by high-pressure spark plasma sintering

Doped transparent ceramics with high optical quality can serve as materials for photonic applications such as laser gain media. In that regard, transparent polycrystalline alumina has potential for high-power applications due to its excellent physical and chemical properties, combined with unique doping possibilities. However, optical birefringence of Al₂O₃ crystals make achieving sufficiently high optical transmittance a processing challenge. In the present study, we demonstrated fabrication of highly transparent 0.5 at.% Cr:Al₂O₃ ceramics by high-pressure spark plasma sintering (HPSPS). The optical properties of these polycrystalline ruby ceramics were analyzed in order to assess possible laser operation (at 694.3 nm). The obtained ceramics exhibit high in-line transmittance (～72.5 % at 700 nm), equivalent to a scattering coefficient of 2.15 cm^?1, and characteristic ruby photoluminescence. The theoretically estimated lasing threshold and percentage of absorbed pump power indicate that such ruby ceramic lasers could operate at reasonable thresholds of 80?225 mW with short lengths of 0.5?5 mm. Thus, HPSPS is a promising method for producing laser-quality doped transparent ceramics for compact laser systems.     

Aliphatic polyurethane elastomers with high performance properties

A new diisocyanate, 1,4-eyclohexane diisocyanate (CHDI), has been used in a series of polyether-based polyurethane elastomers. The slightly opaque samples are semicrystalline in nature with high performance properties, including high softening temperature, very good thermal stability, high tensile and tear strengths, excellent solvent resistance, and low hysteresis in compressive fatigue. Polymer properties are in part due to the small, compact, symmetrical structure of the aliphatic CHDI. Comparison of the physical, mechanical, and thermal properties of polyurethanes prepared from the aliphatic diisocyanate 4,4′-dicyclohexylmethane dilsocyanate (H₁₂MDI) reveal the H₁₂MDI polymers to be more flexible and transparent elastomers with lower softening temperatures and tensile moduli and higher hysteretic heat build up. They are generally soluble in organic solvents.     

Multifunctional fiberglass-reinforced PMMA-BaTiO3 structural/dielectric composites

Fiberglass-reinforced polymer composites were investigated for potential use as structural dielectrics in multifunctional capacitors that require simultaneous excellent mechanical properties and good energy storage characteristics. Composites were fabricated employing poly(methyl methacrylate), PMMA, as the structural matrix. While barium titanate (BaTiO₃) nanopowder was added to the composites for its high room temperature dielectric constant, fiberglass was employed to confer high stiffness. A conductive polymer blend of poly (3,4-ethylenedioxythiophene) and polystyrene sulfonate (PEDOT:PSS) was used to coat the BaTiO₃ nanoparticles with the purpose of further elevating the dielectric constant of the resultant PMMA-composites. FTIR spectroscopy, TGA and SEM measurements were conducted to prove the successful coating of BaTiO₃ nanoparticles with the PEDOT:PSS blend. TEM measurements revealed a good dispersion of coated nanoparticles throughout the PMMA matrix. The fiberglass-reinforced-PMMA composites containing neat and coated BaTiO₃ were found to exhibit excellent stiffness. In addition, the use of PEDOT:PSS in conjunction with BaTiO₃ was observed to improve the dielectric constant of the composites. Finally, the dielectric constant of the structural composites was found to vary only slightly with temperature.     

Preceramic polymer for Si?B?N?C fiber via one‐step condensation of silane,BCl3, and silazane

A preceramic polymer for Si? B? N? C fiber, polyborosilazane, has been synthesized by one‐step condensation reaction of dichloromethylsilane, BCl₃, and hexamethyldisilazane with high yield. The reaction mainly involves the condensation of Si? Cl and B? Cl with N? SiMe₃ followed by SiMe₃Cl evaporation and dehydrogenation between N? H and Si? H. The resulted polymer is a soluble colorless transparent solid with melting point of 70°C and molecular weight of 10,800. The backbone of the polymer is mainly composed of ? Si? N? B‐bridge with some borazine rings. The polymer exhibits good processability and flexible polymer fibers with diameter of 15–20 μm were obtained by melt spinning. Pyrolysis of the as‐synthesized polymer to 1000°C under nitrogen atmosphere results in a ceramic yield of 63 wt %, and the obtained Si? B? N? C ceramic remains fully amorphous up to 1700°C, and only small amount of poorly crystallized BN, Si₃N₄, and SiC phases were observed upon heating at 1850°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Enhancement of electrochemical properties of hot-pressed poly(ethylene oxide)-based nanocomposite polymer electrolyte films for all-solid-state lithium polymer batteries

PEO₁₆-LiClO₄-ZnAl₂O₄ nanocomposite polymer electrolyte (NCPE) films prepared by hot-pressing method have been investigated. In order to compare with the hot-pressed NCPEs, the NCPE films have also been prepared using the conventional solution-casting method. Field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC), conductivity (σ) and interface property studies have been carried out on above two kinds of films. The results show that the NCPE film prepared by hot-pressing method has smoother surface, higher interface stability, lower crystallization and melting temperature values than that prepared by solution-casting method. An all-solid-state lithium polymer battery using the hot-pressed NCPE film as electrolyte, lithium metal and LiFePO₄ as anode and cathode respectively, shows high discharge specific capacity, good rate capacity, high coulombic efficiency, and excellent cycling stability as revealed by galvanostatical charge/discharge cycling tests.     

Effect of heat treatment on the electrical properties of lead zirconate titanate/poly (vinylidene fluoride) composites

Ceramic/polymer composites are attracting increasing interest in materials research and practical applications due to the combination of excellent electric properties of piezoelectric ceramics and good flexibility of polymer matrices. In this case, the crystallization of the polymer has a significant effect on the electric properties of ceramic/polymer composites. Based on different heat treatment methods, the crystallization of poly(vinylidene fluoride) (PVDF) in composites of lead zirconate titanate (PZT) and PVDF can be controlled effectively. PZT/PVDF composites with various PVDF crystallizations exhibit distinctive dielectric and piezoelectric properties. When the crystallization of PVDF is 21%, the PZT/PVDF composites show a high dielectric constant (ε) of 165 and a low dielectric loss (tan δ) of 0.03 at 10³ Hz, and when the crystallization of PVDF reaches 34%, the piezoelectric coefficient (d₃₃) of PZT/PVDF composites can be up to ca 100 pC N^?1. By controlling the crystallization of PVDF, PZT/PVDF composites with excellent dielectric and piezoelectric properties were obtained, which can be employed as promising candidates in high‐efficiency capacitors and as novel piezoelectric materials. Copyright © 2010 Society of Chemical Industry     

New KNbTeO6 transparent tellurate ceramics

New transparent defect pyrochlore KNbTeO₆ ceramics were successfully prepared by Spark Plasma Sintering (SPS) of same composition polycrystalline powders elaborated by classic solid-state reaction from oxide precursors (K₂CO₃, Nb₂O₅, TeO₂) and followed by high energy milling powders. As such precursors are not available as commercial nanopowders, a suitable process has been developed by combining solid-state reactions and high energy milling. The determination of appropriate consolidation conditions and sintering parameters of the green body such prepared, are described in this paper. The resulting ceramic is transparent in both the visible and near infrared range (up to 5.5 μm). The maximum of transmittance is reached in the near infrared region around 2500 nm with a value of 78 % (1 mm thick sample), close to the maximum theoretical value of transmittance. This transparent KNbTeO₆ ceramic demonstrates a homogeneous and dense microstructure with an average grain size less than 500 nm. A small content of secondary phase has been detected by nanoscale observations without drastic effects on transparency. This ceramic exhibits very good mechanical properties similar to the Y₂O₃ transparent ceramic, as well as interesting dielectric properties in the microwave range. This innovative method should drive the development of new transparent materials with technologically relevant applications.     

Two‐Phase LaLuZr2O7 Transparent Ceramic with High Transparency

Two‐phase LaLuZr₂O₇ transparent ceramic was fabricated via vacuum sintering using powders obtained by a simple sol–gel combustion method. These two phases are pyrochlore and defective fluorite phase with different chemical components. The in‐line transmittance of LaLuZr₂O₇ transparent ceramic is 73.4% at 1100 nm, showing an excellent optical performance. LaLuZr₂O₇ transparent ceramic is a promising candidate for scintillator host due to its high density (6.82 g/cm³).     

Highly transparent and color-adjustable Eu2+ doped SrO-SiO2-Al2O3 multilayered glass ceramic prepared by controlling crystallization from glass

Multilayered inorganic transparent materials have been widely used as laser materials, scintillators and phosphors due to their excellent combined properties or functions. However, owing to the limitation of the current preparation technology, only the ceramics with cubic crystal structure could be fabricated into multilayered transparent materials, which has greatly obstructed the diversity of multilayered transparent materials. Here we report a novel non-cubic multilayered transparent phosphor with a ceramic/glass/ceramic sandwich-like structure prepared by controlling crystallization from Eu₂O₃-SrO-Al₂O₃-SiO₂ bulk glass. The ceramic thicknesses, total transmittances, emission colors and the fluorescence quantum yields of the samples can be adjusted continuously within a certain range. The multilayered transparent phosphor could be used as a potential candidate for the white LEDs with high color rendering index. It can be anticipated that the controlled crystallization from bulk glass method is a simple, fast, cost-effective and promising synthesis approach to prepare non-cubic transparent materials with ceramic/glass/ceramic structures.     

Crystallization,structure and properties of MgO-Al2O3-SiO2 highly crystalline transparent glass-ceramics nucleated by multiple nucleating agents

Generally, highly crystalline transparent glass-ceramics possess excellent physical and chemical properties compared to organic and other inorganic optical materials. We have successfully prepared highly crystalline transparent glass-ceramics in the MgO-Al₂O₃-SiO₂ system by "extreme-time" nucleation & "finite-time" crystallization processes using P₂O₅, ZrO₂ and TiO₂ as multiple nucleating agents. The results revealed that the crystallization of glass is controlled by a three-dimensional interfacial crystal growth process. These glass-ceramics mainly consisted of cordierite crystals with a residual glassy phase, and crystallinity increased with crystallization time, but light transmittance decreased with crystallization time due to enlarged grain sizes. EDS mapping revealed a uniform distribution of elements within the glass-ceramic. In the optimal preparation condition (825?°C/96?h?+?990?°C/3?h), these glass-ceramics exhibited a high crystallinity (87.3?vol. %), high transmittance (78%), and excellent mechanical properties. This work provides a roadmap for preparing highly crystalline transparent glass-ceramics for applications in optical engineering.     

Relationship between degree of polymerization and optical and thermal properties of fluorene in polycarbonate polymers

The influences of average degree of polymerization (D_p) and terminal group on thermal and optical properties of high refractive indexed transparent polymers were investigated. In this study, 9,9‐bis[4–(2‐hydroxyethoxy) phenyl] fluorene (BPEF) homo polymer was selected because it has been used as a representative monomer in high refractive index polymers as well as its unique property. BPEF has stable amorphous phase and reacts like a polymer. Its unique reaction allows continuous investigation from monomer to polymer. For hydroxyl‐terminated polymer, the refractive index (n_d) decreased with increasing D_p. On the other hand, for a phenolic‐terminated group, n_d increased with increasing D_p, and both converged to same value in high D_p region. As for glass transition temperatures (T_g), both terminal group series were increased as D_p increased. Though T_g of hydroxyl‐terminated polymer was higher than that of phenolic‐terminated polymer in the low D_p region, both converged to the same value and the inverse number of T_g had linear correlation against the weight percentage of carbonyl groups (CO), which was calculated by D_p. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45042.     

Preparation and properties of transparent and conducting nylon 6-based composite films

Highly transparent and conducting polypyrrole–(PPy–N) and polyaniline–nylon 6 (PAN) composite films could be easily obtained by immersing nylon 6 films containing pyrrole or aniline into an oxidant solution such as aqueous FeCl₃ solution or aqueous (NH₄)₂S₂O₈ solution containing HCl. The conductivity, transmittance, and mechanical properties of these composite films were affected by the preparative conditions. The maximum conductivity and transmittance of the PPy–N composite films were 10^?3 S/cm and about 75% at 550 nm, and in the case of the PA–N composite films, 10^?2 S/cm and 75%, respectively. The morphology of PPy–N and PA–N composite films depended on the polymerization conditions, which might be due to the difference in the polymerization speed of pyrrole or aniline in polymer matrices. These PPy–N and PA–N composite films exhibited good environmental stability and excellent mechanical properties. © 1994 John Wiley & Sons, Inc.     

Preparation of a Transparent Spherical Polymer Matrix Containing TiO2/SiO2 Hybrid Materials

A transparent spherical polymer matrix containing TiO₂/SiO₂ hybrid materials is prepared from the copolymerization reaction between TiO₂/SiO₂ hybrid materials containing vinyl groups and methyl methacrylate (MMA). Transparent TiO₂/SiO₂ hybrid materials are prepared from the reaction between nucleophilic agents and tetrabutyl titanate (TBT). Three reaction mechanisms leading to the formation of nanometer TiO₂/SiO₂ hybrid materials, including the single group coordination reaction mechanism (SGCRM), double group chelation reaction mechanism (DGCRM) and bridge coordination reaction mechanism (BCRM) are discussed in detail and confirmed by FT‐IR spectroscopy. The sizes of the TiO₂/SiO₂ hybrid material nanoparticles are also characterized and calculated by TEM and range from 20–40 nm. The diameter of the particles in the transparent spherical polymer matrix is ca. 100–200 nm and their shape is a regular spherical structure from TEM observations. The transparent spherical polymer matrix containing TiO₂/SiO₂ hybrid materials could be used as holographic anti‐counterfeiting materials.