Highly reflective interface design for phosphor-in-glass converter enabling ultrahigh efficiency laser-driven white lighting

To address the problems of low luminous efficacy and poor thermal stability of reflective phosphor-in-glass (PiG) converter, a thermally robust and highly reflective PiG-boron nitride (BN)-aluminum nitride (AlN) converter was designed for enabling ultrahigh efficiency laser-driven white lighting. Benefiting from the ingenious sandwich design with the thermally conductive AlN substrate and highly reflective BN-glass interface, a La₃Si₆N₁₁:Ce³⁺ (LSN) PiG-BN-AlN converter achieves white light emission with a high luminous efficacy of 214.2 lm/W under the 3.15 W blue laser excitation, which is the best recorded value for the reflective PiG-based converters thus far, and the surface temperature of LSN PiG is low to 126 °C. Furthermore, the LSN PiG-BN-AlN converter incorporates CaAlSiN3:Eu²⁺ (CASN) red phosphor to enable high-quality white light emission with high luminous flux and good color quality. The results reveal that the designed PiG-BN-AlN converter provides a promising strategy for achieving ultrahigh efficiency laser-driven white lighting.     

Bi3+/Mn4+ co-doped dual-emission phosphors for potential plant lighting

Developing environment-friendly dual-emission phosphors of both blue–cyan and deep-red lights is desirable for the utilized indoor plant lighting research. Notably, the naked 6s and 6p Bi³⁺ ions are sensitive to the lattice sites, which emit from Ultraviolet (UV) to red lights in various crystal compounds. Meanwhile, the ²E → ⁴A_2g transition of Mn⁴⁺ ions promises its deep-red light emissions, which satisfies the demand for specific wavelength lights for plants growth. Hence, a Bi³⁺/Mn⁴⁺ co-doped Sr₂LaGaO₅: Bi³⁺, Mn⁴⁺ (SLGO:Bi³⁺:Mn⁴⁺) phosphor was finally synthesized. The phase, micromorphology and luminescent properties were systematically evaluated. Upon excitation at 350 nm light, dual emissions of both blue–cyan (470 nm) and deep-red (718 nm) lights were observed. Besides, due to the pronounced photoluminescence (PL) spectral overlap between Bi³⁺ and Mn⁴⁺ ions, a potential energy transfer process from Bi³⁺ to Mn⁴⁺ ions was confirmed. The relative PL intensities between Bi³⁺ and Mn⁴⁺ ions can be tuned just by adjusting the Mn⁴⁺ ion concentration. Besides, Li⁺ co-doping has been evidenced to improve the deep-red emissions (718 nm) of SLGO:0.005Mn⁴⁺ due to charge compensation and rationally designed lattice distortion, together with the improved thermal stability. Finally, the emissions of SLGO:Bi³⁺, Mn⁴⁺, Li⁺ phosphor suit properly with the absorption of the four fundamental pigments for plant growth, indicating that the prepared phosphorescent materials may have a prospect in plant light-emitting diodes lighting.     

On the luminance saturation of phosphor-in-glass (PiG) films for blue-laser-driven white lighting: Effects of the phosphor content and the film thickness

To investigate the luminance saturation in high-power blue-laser-driven solid state lighting, the Y₃Al₅O₁₂: Ce (YAG)-based PiG films was co-fired with a high thermally conductive sapphire substrate. When the PtG ratio or the thickness of the PiG film increases, the luminance saturation becomes worse and both of the luminous flux and luminous efficacy decrease. With an additional sapphire substrate coated with an anti-reflection layer on one side and a blue-pass filter on another side attached to the PiG film, the film shows an improvement in luminous flux and efficacy, and produces the white light with a luminous flux of 1709 lm, a luminous efficacy of 211 lm W^?1 and a correlated color temperature of 6602 K under the maximum (10.3 W mm^?2) blue laser light excitation. It indicates that the PiG film could be applied in high power laser-driven solid state lighting when its microstructure is carefully tailored.     

Crosslinking of PET through solid state functionalization with alkoxysilane derivatives

A new way for crosslinking poly(ethylene terephthalate) (PET) films and fibers is described using solid state functionalization of the PET end groups (alcohol and acid) with two reagents, respectively, 3-isocyanatopropyltriethoxysilane (IPTESI) or/and 3-glycidoxypropyltrimethoxysilane (GOPTMSI). This functionalization is then followed by hydrolysis-condensation reactions of PET-alkoxysilane end groups leading to the PET crosslinking.First of all, the functionalization reactions were investigated on model compounds by ¹H NMR spectroscopy in a range of temperature 80-160 °C. Furthermore, the diffusion of reagents in solid PET, depending on the initial degree of PET crystallinity, was characterized in the same temperature range through the variation of sample mass. On the other hand, this method allowed us to determine the diffusion coefficients and the solubility of the reagents in solid PET at different temperatures and initial crystallinity degrees.End groups functionalized PET films and fibers by alkoxysilane were then crosslinked by immersion of the samples in hot water. The crosslinking density was characterized by measuring the insoluble fraction of PET in good solvent constituted by a mixture of trifluoroacetic acid and dichloromethane (50/50 vol.). An insoluble fraction close to 70% was obtained by the functionalization treatment of amorphous PET film (8% crystallinity) by a mixture of GOPTMSI + IPTESI (50/50 M) at 155 °C for 1 h followed by hydrolysis-condensation reactions at 80 °C for 72 h. Thermomechanical and thermal properties of films and fibers were observed and found to be considerably enhanced in comparison to the untreated samples. The tensile properties of these partially crosslinked samples were maintained up to 320 °C.     

Designing white‐light LED lighting for the display of art: A feasibility study

When displaying art, several criteria must be balanced when designing illumination including the artist's intention, damage, energy efficiency, viewing experience and understanding, and for commercial galleries and sales. The most common lighting for art includes natural daylight and incandescent spotlights. Neither source is optimal for all criteria; thus there is considerable interest in the use of white‐light light‐emitting diode (LED) lighting. A feasibility study was conducted to address two questions. First, was it possible to design a three‐primary LED source that yielded the same color rendering as common museum lighting? Second, could one design the lighting to achieve specific color appearance attributes? Three‐primary lights using a Gaussian function were optimized matching the chromaticity of D65 and minimizing color differences for a set of acrylic dispersion paints. The optimal wavelengths depended on bandwidth. Lights were also optimized that either maximized or minimized average chroma. A set of real LEDs was selected that produced similar results when evaluated computationally. A source that increases chroma may be useful when used to illuminate works of art with high light sensitivity: very low illuminances are necessary and such a source will compensate for the reduction of colorfulness and visual clarity. A source that decreases chroma may be used to render art in similar fashion to low‐light conditions such as churches and caves. In general, white LED lighting is advantageous for art conservation because they do not emit UV and IR radiation and their visible radiation is reduced when compared with their continuous spectrum equivalent. © 2010 Wiley Periodicals, Inc. Col Res Appl, 2011     

Stable and efficient all-inorganic color converter based on phosphor in tellurite glass for next-generation laser-excited white lighting

Laser lighting is considered as a next-generation high-power lighting due to its high-brightness, directional emission, and quasi-point source. However, thermally stable color converter is an essential requirement for white laser diodes (LDs). Herein, we proposed a stable and efficient phosphor-in-glass (PiG) in which YAG:Ce³⁺ and MFG:Mn⁴⁺ phosphors were embedded into tellurite glass matrixes. The glass matrixes with low-melting temperature and high refractive index were prepared by designing their composition. The luminescence of YAG:Ce³⁺ PiGs was adjusted by controlling phosphor thickness. Aiming to compensate for red emission, multi-color PiGs were realized by stacking MFG:Mn⁴⁺ layers on YAG:Ce³⁺ layer. The phosphor crystals are chemically stable and maintain intact in the glass matrix. Furthermore, white LDs were fabricated by combining the PiGs with blue LDs. As the phosphor thickness increases, the chromaticity of white LDs shifts from cool to warm white, and the white LDs exhibit excellent thermal stability under different excitation powers.     

Synthesis of Ca2SiO4:Dy3+ phosphors from agricultural waste for solid state lighting applications

Trivalent dysprosium (Dy³⁺) ions -doped calcium silicate (Ca₂SiO₄) phosphors have been synthesized by utilizing agricultural waste of egg shell and rice husk through solid-state reaction method. The synthesized Ca₂SiO₄ powders thus obtained are crystallized in monoclinic structure with unit cell parameters of a = 5.53 Å; b = 6.67 Å; c = 9.13 Å; β = 87.43° and irregular shape morphology. Luminescent properties of Dy³⁺:Ca₂SiO₄ phosphors were studied by varying active ion concentration. The phosphors emit characteristic blue and yellow emissions of Dy³⁺ ions corresponding to the ⁴F_9/2 → ⁶H_15/2 and ⁴F_9/2 → ⁶H_13/2 transitions, respectively. Color coordinates evaluated from emission spectra are found to fall in the white light region. Decay curves for the ⁴F_9/2 level of Dy³⁺ ions exhibit single exponential nature and turn into non-exponential with shortening of lifetime from 739 µs to 510 µs when Dy³⁺ ion concentration is increased from 0.001 to 0.5 mol%. All these results confirm that Ca₂SiO₄:Dy³⁺ phosphors are suitable for the use as low cost white light emitting phosphors.     

Experimental based full process simulation of alumina selective laser processed parts densified by cold isostatic pressing and solid state sintering

The compound process of cold isostatic pressing (CIP) of alumina selective laser processed (SLP) parts and solid state sintering (SSS) and its full process simulation were realized in this paper, focusing on studying the overall deformation, relative density distribution, grain growth and sintering stress variation during the process. Especially, correlation was established between the macroscopic deformation and microscopic evolution. Model parameters for alumina are presented, which were optimized in accordance with the experimental results. CIPed part still exhibited density inhomogeneity, of which SSS tended to increase the overall density and homogenize density distribution. The sintering behavior was studied with the employment of dilatometer experiments. Furthermore, compared with conventional heating strategy, fast firing turned out to decrease sintering production time as well as drive the matter diffusion and densification process. The master sintering curve (MSC) moves upward a little under the condition of fast firing.     

Novel chemically cross-linked solid state electrolyte for dye-sensitized solar cells

Poly(vinylpyridine-co-ethylene glycol methyl ether methacrylate) (P(VP-co-MEOMA)) and α,ω-diiodo poly(ethylene oxide-co-propylene oxide) (I[(EO)_0.8-co-(PO)_0.2]_yI) were synthesized and used as chemically cross-linked precursors of the electrolyte for dye-sensitized solar cells. Meanwhile, α-iodo poly(ethylene oxide-co-propylene oxide) methyl ether (CH₃O[(EO)_0.8-co-(PO)_0.2]_xI) was synthesized and added into the electrolyte as an internal plasticizer. Novel polymer electrolyte resulting from chemically cross-linked precursors was obtained by the quaterisation at 90 °C for 30 min. The characteristics for this kind of electrolyte were investigated by means of ionic conductivity, thermogravimetric and photocurrent-voltage. The ambient ionic conductivity was significantly enhanced to 2.3 × 10⁻⁴ S cm⁻¹ after introducing plasticizer, modified-ionic liquid. The weight loss of the solid state electrolyte at 200 °C was 1.8%, and its decomposition temperature was 287 °C. Solid state dye-sensitized solar cell based on chemically cross-linked electrolyte presented an overall conversion efficiency of 2.35% under AM1.5 irradiation (100 mW cm⁻²). The as-fabricated device maintained 88% of its initial performance at room temperature even without sealing for 30 days, showing a good stability.     

Power dependent upconversion in Er3+/Yb3+ co-doped BiNbO4 phosphors

In the present article, optical properties and energy upconversion in Er³⁺/Yb³⁺ co-doped BiNbO₄ matrix were investigated. The BiNbO₄ matrix was prepared using the solid-state reaction method. X-ray diffraction of the matrix shows that the crystal structure is consistent with ICSD code 74338. The grain distribution and the behavior of doping with Er³⁺ and Yb³⁺ on the sample surface were obtained by scanning electron microscope. Raman spectral characterization was carried out to examine the behavior of the vibrational modes of the samples. Upconversion emissions in the visible region at 484.5, 522, 541.5 and 670.5 nm in the matrices BiNbO₄:Er,Yb and BiNbO₄:Er were observed and analyzed as a function of 980 nm laser excitation power and rare-earth doping concentration. The results show that BiNbO₄ is a promising host material for efficient upconversion phosphors.     

Poly(triallyl phosphate) and its copolymers with allyl diglycol carbonate as solid state nuclear track detectors.

This paper describes the design and development of new polymers for solid state nuclear track detection. A monomer triallyl phosphate (TAP) has been synthesized and cast homo/ copolymerized with allyl diglycol carbonate (ADC) to get transparent thin films of poly(triallyl phosphate) (PTAP) and poly(TAP-co-ADC) polymers respectively, which were successfully explored for the first time for detection of alpha particles and fission fragments. The polymerization kinetics studies were carried out to generate constant rate polymerization profile for TAP and TAP: ADC monomer mixture. Poly(TAP-co-ADC) copolymer in 3:7 wt./wt. ratio showed better radiation sensitivity as compared to indigenously prepared PADC and commercially available CR-39 detectors.     

Copolymerization of norbornene with ethylene: A high-resolution liquid NMR, DSC and solid state NMR study

In this paper, we report the monomer reactivity on the copolymerization of norbornene and ethylene. The reactivity ratios for ethylene (M₁) and norbornene (M₂) are 18.5 and 0.035, respectively. Different copolymerization conditions can produce COC with different microstructures. A ¹³C NMR shift assignment in pentad sequences in copolymers has been obtained. More isolated polynorbornene or a micro-block length can be obtained using a low Zr/Al catalyst/co-catalyst ratio and at a lower NB/ethylene feed ratio. The T_1p ^C decay curve shows two component decays in all resonance peaks. These two component decays come from different norbornene microstructures, while the block and alternative have similar T_1p ^C values.     

PET recycling: Evaluation of the solid state polymerization process

Many studies have been carried out to make bottle‐to‐bottle recycling feasible. One of the difficulties found is the decrease in the polymer's molar mass, which damages the injection blow molding process. A method usually employed to increase the molar mass of virgin PET consists of solid‐state polymerization (SSP). In this work, we studied the SSP process applied to post‐consumer recycled PET by analyzing the inherent viscosity and amount of carboxylic end groups, and the results of dynamic flow rheometry. Although the results show that the recycling process decreases polymer molar mass, and this indicates degradative processes, SSP was successful in increasing molar mass in post‐consumer recycled PET. This made feasible bottle‐to‐bottle recycling. In addition, the parallel plate rheometry technique was powerful in assessing the degradative process and, therefore, that the SSP process was successful. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

PET固相缩聚反应动力学研究进展

目前多种固相缩聚反应动力学模型共存,影响了固相缩聚工艺优化及新工艺的开发。笔者从固相缩聚本征反应出发,对比分析了文献报道的动力学模型：经验模型、反应控制模型、扩散控制模型及反应与扩散共同控制模型及所涉及的反应及活化能,指出固相缩聚过程中扩散与结晶的研究不足是造成固相缩聚反应动力学模型多样性的主要原因。     

锑系催化剂聚酯的熔融及固相聚合

对锑系催化剂中常用的醋酸锑(Sb(AC)3)、三氧化二锑(Sb2O3)和乙二醇锑(Sb2(EG)3)进行熔融及固相聚合试验,结果表明,三氧化二锑的有效锑含量比醋酸锑及乙二醇锑低;乙二醇锑在固相聚合时的催化作用略低于醋酸锑和三氧化二锑;3种锑系催化剂相比,乙二醇锑催化剂聚酯固相聚合速度略慢,但特性粘数增幅最为平稳;220℃下的反应速率常数以醋酸锑制得的聚酯最大。     

A correlation for calculating HHV from proximate analysis of solid fuels

Higher heating value (HHV) and composition of biomass, coal and other solid fuels, are important properties which define the energy content and determine the clean and efficient use of these fuels. There exists a variety of correlations for predicting HHV from ultimate analysis of fuels. However, the ultimate analysis requires very expensive equipments and highly trained analysts. The proximate analysis on the other hand only requires standard laboratory equipments and can be run by any competent scientist or engineer. A few number of correlations of HHV with proximate analysis have appeared in the solid fuel literature in the past but were focused on one fuel or dependent on the country of origin. This work introduces a general correlation, based on proximate analysis of solid fuels, to calculate HHV, using 450 data points and validated further for additional 100 data points. The entire spectrum of solid carbonaceous materials like coals, lignite, all types of biomass material, and char to residue-derived fuels have been considered in derivation of present correlation which is given as below: HHV=0.3536FC+0.1559VM−0.0078ASH (MJ/kg) (where FC 1.0-91.5% fixed carbon, VM 0.92-90.6% volatile matter and Ash 0.12-77.7% ash content in wt% on a dry basis). The average absolute error of this correlation is 3.74% and bias error is 0.12% with respect to the measured value of HHV, which is much less than that of previous correlations of the similar kind. The major advantage of this correlation is its capability to compute HHV of any fuel simply from its proximate analysis and thereby provides a useful tool for modeling of combustion, gasification and pyrolysis processes. It can also be used in examining old/new data for probable errors when results lie much outside the predicted results.     

Engineering cation vacancies to improve the luminescence properties of Ca14Al10Zn6O35: Mn4+ phosphors for LED plant lamp

In the recent years, Mn⁴⁺-doped phosphors for indoor plant cultivation have received extensive concern owing to the far-red emission that can match well with the absorption spectra of plant pigments. Whereas, many Mn⁴⁺-doped phosphors still face some challenges such as poor light efficiency and low thermal stability. It is an effective way to resolve these problems via cation vacancies engineering. Herein, the Ca_14−xAl₁₀Zn_6−yO₃₅: Mn⁴⁺ phosphors are successfully synthesized by combustion method. The luminescence intensity of Ca_14−xAl₁₀Zn_6−yO₃₅: Mn⁴⁺ phosphor is enhanced through engineering Ca²⁺ and Zn²⁺ vacancies according to the charge compensation mechanism. The optimal content of each Ca²⁺ and Zn²⁺ vacancy is equal to be 0.3. Furthermore, the defect formation is accompanied with lattice distortion, which plays a vital role in driving the excited phonon traps to reduce the energy loss by non-radiation transitions. Therefore, the thermal stability of Ca_14−xAl₁₀Zn_6−yO₃₅: Mn⁴⁺ phosphor is also improved via engineering cation vacancies. In addition, the Ca_14−xAl₁₀Zn_6−yO₃₅: Mn⁴⁺ phosphors can be effectively excited by blue light and it exhibits far-red emission due to the Mn⁴⁺ spin-forbidden ²E → ⁴A₂ transition. The results suggest that the Ca_14−xAl₁₀Zn_6−yO₃₅: Mn⁴⁺ phosphors can have a tremendous potential in indoor plant cultivation.     

Luminescence enhancement of zincblende ZnS:Cl nanoparticles synthesized by a low temperature solid state reaction method

Cl⁻-doped ZnS (ZnS:Cl⁻) nanoparticles with strong blue emission were synthesized using a facile low temperature solid state reaction method. X-ray powder diffraction, scanning electron microscopy, UV–vis absorption, and X-ray photoelectron spectroscopy were used to characterize their crystal structures, microstructural characteristics, and chemical compositions, respectively. The ZnS:Cl⁻ nanoparticles were quasi-spherical in shape and had a cubic zincblende crystal structure. Cl⁻ doping was found to lead to a reduction in the crystallite size of the ZnS:Cl⁻ nanoparticles. It showed that Cl⁻ doping remarkably enhanced the luminescence properties of the ZnS:Cl⁻ nanoparticles, and an optimal Cl⁻ doping condition was determined. Post annealing was found to further improve the luminescence properties of the ZnS:Cl⁻ nanoparticles. The effect of post annealing temperature on the luminescence properties of the ZnS:Cl⁻ nanoparticles was systematically studied and discussed.     

New aspects on the mechanism of the solid state polyamidation of PA 6,6 salt

Hexamethylenediammonium adipate (PA 6,6 salt) was solid state polymerized in the temperature range of 158-190 °C, in a thermogravimetric analysis (TGA) chamber, which simulates a polyamidation reactor. A mechanism based on the role of the volatile component of the salt (i.e. hexamethylenediamine) is found to predominate: the diamine escapes along with polycondensation water, meanwhile this volatilization occurs earlier than the water formation, apparently resulting in an increase of the vacancy defects and of the nucleation sites in the salt crystals. In addition, critical reaction parameters, such as reaction time, temperature, surrounding gas and presence of catalyst in the starting material were investigated, so as to discern the rate-controlling mechanism of the process. Finally, proper SSP kinetics were studied taking into consideration the diamine loss occurred and SSP rate constants were calculated through a suitable rate expression.