Ultra-low Melting Research Articles

Insight into the optical evaluation of sunlike LED devices with full-visible spectrum emission based on ultra-low melting tin fluorophosphate glass for human centric lighting

Full spectrum sunlike light-emitting diode (LED) devices in the wavelength range of 380–670 nm have received much attention for their applications in human centric lighting. Herein, the inorganic color converter of the sunlike phosphor-in-glass (PiG) has been developed by embedding the green-emitting (Lu3-xYxAl5O12: Ce3+) and red-emitting (Sr0.6Ca0.4AlSiN3: Eu2+) phosphor powders in ultra-low melting tin fluorophosphate glass. Notably, the sunlike PiG exhibits the full spectrum in the wavelength range of 380–670 nm under the excitation of a near-ultraviolet (NUV) chip. Tunable color temperature (2785 K–5806 K) and high color rendering index (Ra = 95) were obtained by varying the mix ratio of the red-emitting component in the glass matrix. Further, the full visible spectrum emission was regulated by adjusting the Lu/Y ratio of the green phosphor Lu3-xYxAl5O12: Ce3+ and the color quality was further optimized (Ra = 97). The color quality of white light-emitting diode (WLED) was systematically investigated using Illuminating Engineering Society (IES) of North America evaluation systems and the LED devices exhibit fidelity index (Rf) and gamut index (Rg) close to sunlight (Rf = 95, Rg = 101). Compared with the traditional phosphor-in-silicone (PiS), the sunlike PiG based WLED exhibits a low working temperature of ∼37 °C for high power LED. Therefore, the WLED devices based on sunlike-PiG can be regarded as promising candidates for ultra-high color rendering index light sources because of the adjustable color temperature, high color quality, low-efficiency loss, excellent thermal properties and water stability.

PROGRESSIVE MUSCLE HYPOXIA RESEARCH: A MODIFIED METHOD FOR ASSESSING CELL VIABILITY IN SKELETAL MUSCLE BIOPSIES USING VITALITY DYES AND CONFOCAL MICROSCOPY

AbstractObjectivesAcute compartment syndrome (ACS) is a progressive form of muscle ischaemia that is a surgical emergency and can have detrimental outcomes for patients if not treated optimally. The current problem is that there is no clear diagnostic threshold for ACS or guidance as to when fasciotomies should be performed. A new diagnostic method(s) is necessary to provide real-time information about the extent of muscle ischaemia in ACS. Given that lactic acid is produced by cells through anaerobic respiration, it may be possible to measure H+ ion concentration and to use this as a measure of ischaemia within muscle. Although we are familiar with the key biochemical metabolites involved in ischaemia; and the use of viability dyes in cell culture to distinguish between living or dead cells is well recognised; research has not been undertaken to correlate the biochemical and histological findings of ischaemia in skeletal muscle biopsies. Our primary aim was to investigate the potential for viability dyes to be used on live skeletal muscle biopsies (explants). Our secondary aim was to correlate the intramuscular pH readings with muscle biopsy viability.MethodsNine euthanised Wistar rats were used. A pH catheter was inserted into one exposed gluteus medius muscles to record real-time pH levels and muscle biopsies were taken from the contralateral gluteus medius at the start of experiment and subsequently at every 0.1 of pH unit drop. Prior to muscle biopsy, the surface of the gluteus medius was painted with a layer of 50µmol/l Brilliant blue FCF solution to facilitate biopsy orientation. A 4mm punch biopsy tool was used to take biopsies. Each muscle biopsy was placed in a base mould filled with 4% ultra-low melting point agarose. The agarose embedded tissue block was sectioned to generate 400 micron thick tissue slices with a vibratome. The tissue slices were then placed in the staining solution with Hoechst 33342, Ethidium homodimer-1 and Calcein am. The tissue slices were imaged with Zeiss LSM880 confocal microscope's Z stack function. A dead muscle control was created by adding TritonX-100 to other tissue slices. For quantitative analyses, the images were analysed in Image J using the selection tool. This permitted individual cells to be identified and the mean grey value of each channel to be defined. Using the dead control, we were able to identify the threshold value for living cells using the Calcein AM channel.ResultsViability dyes, used primarily for cell cultures, can be used with skeletal muscle explants. Our study also showed that despite a significant reduction in tissue pH concentration over time, that almost 100% of muscle cells were still viable at pH 6.0, suggesting that skeletal muscle cells are robust to hypoxic insult in the absence of reperfusion.ConclusionsViability dyes can be used on skeletal muscle biopsies. Further research investigating the likely associations between direct measured pH using a pH catheter, the concentrations of key cellular metabolic markers, and muscle tissue histology using vitality dyes in response to ischaemia, rather than hypoxia, is warranted.Declaration of Interest(b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Activating ultra-low temperature Li-metal batteries by tetrahydrofuran-based localized saturated electrolyte

For realizing the commercialization of Li-metal batteries (LMBs), the discharge-blocking obstacles under ultra-low temperatures must be conquered besides the long-term reversibility. Nevertheless, commercial carbonate-based electrolytes are not only incompatible with the aggressive Li anode, but also have poor fluidity at low temperatures. The prevailing chain-ether-based electrolyte designing tactics, such as the common-used DME, improve the affinity with Li metal to some extent, but the multiple Lewis-acid binding sites of chain ethers are not conducive to the de-solvation of Li+. Herein, for the first time, the cheap cyclic-type tetrahydrofuran (THF) with ultra-low melting point and weak solvating power is adopted for designing an original THF-based localized saturated electrolyte (Tb-LSCE), demonstrating excellent adaptability for low-temperature LMBs. Computational and experimental evidence verify the original solvated structure is modified via the addition of fluorinated antisolvent, further contributing to the Li+-THF de-solvation. Therefore, equipped with Tb-LSCE, the assembled Li-NCM523 cells achieve powerful anti-polarization capability at low temperatures (73.3% discharge capacity retention at -30 °C). Furthermore, the unique solvated sheath structure of Tb-LSCE also regulates the interfacial chemistry and uniformity of Li depositing behavior, highlighted by the outstanding reversibility of Li-Li cells (a long lifespan of exceeding 1600 h at 30 °C and 1100 h at -30 °C, respectively) and Li-NCM523 cells (80.7%, 160 cycles) even remarkably stable operation within 50 cycles (ultra-high cathode loading of 19.7 mg cm−2). This work outlines a cheap and effective electrolyte design solution to activate the potential LMBs under practical conditions, especially those operated under cryogenic environments.

Versatile phosphor-in-glass based on Sn–F–P–O matrix with ultra-high color rendering for white LEDs/LDs

White light with excellent color rendering property has been highly required for comfortable and healthy illumination. A facile strategy to achieve high color rendering index (Ra >90) in practical applications is using near ultraviolet chips as excitation sources combined with RGB phosphors. However, achieving high color rendering with both blue chips and near-ultraviolet (NUV) chips for commercial phosphors dispersed in phosphor-in-glass (PiGs) materials is still a big challenge. In this work, the PiG based on the ultra-low melting point Sn–F–P–O glass with commercial green (Lu3Al5O12:Ce3+) and red (SrxCa1-xAlSiN3:Eu2+) phosphors has been successfully fabricated by one-step sintering method. The phase identification and distribution of monochromatic red phosphor in glass (R-PiG) and green phosphor in glass (G-PiG) were investigated in detail. The Sn2+ ions in Sn–F–P–O matrix show the intense blue emission bands centered at 420 nm under the excitation of NUV chips (365 nm). Notably, the polychromatic red/green phosphor in glasses (R/G-PiGs) are versatile and exhibited excellent color rendering (Ra = 93, Ra = 95, Ra = 92, respectively) properties excited by both blue chips, NUV chips and laser diodes (WLD). The working temperature of R/G-PiGs is stable at ∼33 °C and ∼55 °C when employed in WLEDs/WLDs (1 W), which greatly prevented the phenomenon of “thermal quenching” for the phosphors caused by high temperature. Thus, the versatile R/G-PiG with ultra-high color rendering and excellent thermal properties indicates its promising application in high-power white LEDs/LDs.

Ultralow Melting of Iron Nitrides and the Fe–N–C System at High Pressure

AbstractIron nitrides and carbonitrides are the two primary hosts of deep nitrogen in the Earth’s interior; hence, the storage and circulation of deep nitrogen can be largely controlled by the melting behavior of iron nitrides and the Fe–N–C system. In this study, the melting temperatures of these minerals were determined individually and jointly using the new diagnostics of electrical resistance jump up to 80 GPa in laser‐heated diamond‐anvil cells. The solidus curves of these samples are extremely low at mantle pressures, and are marginally affected by the iron spin transition, nitrogen concentration, and carbon incorporation, suggesting that nitrogen‐rich metallic liquids likely exist at depths of <1,500 km in the present‐day mantle. Meanwhile, our Raman spectra are indicative of N2 degassing out of iron nitride liquids at <12 GPa. These results suggest that low‐pressure N2 degassing in the proto‐Earth coupled with nitrogen‐rich liquids hidden in present‐day lower mantle play important roles in the redistribution of deep nitrogen through geologic time and space.

High-performance red@green core-shell emitting nitride phosphor with monodisperse Eu2+ luminescence centers for solid state lighting

The red@green core-shell emitting phosphor with monodisperse luminescence center was successfully constructed by Eu2+ doped Sr2Si5N8 and Sr2Si5N8@SrSi2O2N2 via a deposition-precipitation (DP) method. Compared to traditional solid state reaction (SSR) method, under excitation at 370 nm, Sr2Si5N8:0.05Eu2+ phosphor prepared by DP method exhibits red emission at 611 nm and an ~1.4-fold luminescent intensity enhancement. Interestingly, upon near-ultraviolet (NUV) excitation, Eu2+ doped Sr2Si5N8@SrSi2O2N2 phosphors prepared by DP method exhibit a dual emission feature with the green emission at 538 nm and red emission peak at 611 nm. The elemental line scanning spectrum of the energy dispersive X-ray analysis indicates a core@shell structure of Sr2Si5N8@SrSi2O2N2. Furthermore, this red@green core-shell emitting phosphor can be encapsulated in ultra-low melting Sn-F-P-O glass to achieve the white light with excellent color quality Ra = 85) and low correlated color temperature (4484 K) when pumped by near ultraviolet LED chips.

Phosphor-in-glass with full-visible-spectrum emission based on ultra-low melting Sn-F-P-O glass pumped by NUV LED chips

Herein, the phosphor-in-glass (PiG) with full-visible-spectrum emission has been successfully fabricated by incorporating SrSi2O2N2: Eu2+ (SSON:Eu) and CaAlSiN3: Eu2+ (CASN:Eu) phosphors in ultra-low melting Sn-F-P-O glass using one-step sintering method. The Sn2+ ions show intense blue-green emission characteristics under the excitation of NUV chips, which are highly dependent on its coordination environment in Sn-F-P-O glass. Then, it was investigated in detail for the first time that fluoride from Sn-F-P-O glass substrate migrates and gathers around the embedded phosphors, which is closely related to the emission performance of Sn2+ activators in the PiG. Furthermore, the mechanism of enhancing the PL intensity of Sn2+ ions by embedded phosphors is proposed. As a result, the PiG with full-visible-spectrum emission can be achieved under 370 nm excitation. Importantly, the PiG pumped by NUV LED chips shows excellent-quality white-light with high CRI (Ra = 91) and lower CCT (4993 K). The WLED based on this PiG has been demonstrated as a promising candidate for solid warm light source in the future because of the excellent optoelectronic performance and easy-preparation process.

Red-emitting improvement of CaAlSiN3:Eu2+ phosphor-in-glass: Insight into the effect of atmospheric pressure preparation on photoluminescence properties and thermal degradation

The red-emitting phosphor-in-glass (PiG)s have been successfully prepared by a facile one-step co-sintering method on the basis of ultra-low melting Sn-P-F-O glass and CaAlSiN3: Eu2+ red phosphors synthesized under atmospheric-pressure (denoted as CASN-AP) and high-pressure (denoted as CASN-HP), respectively. The crystal structure, particle morphology, photoluminescence (PL) properties and surface states of the phosphors were investigated detail by X-ray powder diffraction (XRD), field emission electron microscopy (FESEM), fluorescence spectroscopy and X-ray photoelectron spectroscopy (XPS). Under excitation of blue light (460 nm), CASN-AP phosphor with red emission at 659 nm shows a higher luminescent intensity by 23 % than that of CASN-HP phosphor. Moreover, a shorter photoluminescence lifetime and red shift of 9 nm for emission peak can be also found for the CASN-APphosphor, which is ascribed to the increased Si-N bonds and surface Si/N ratio (1.86) demonstrated by the XPS analysis. Besides, the quantum yield and thermal degradation of both phosphors have been investigated. CASN-AP phosphor exhibits higher emission intensity because of its more emitting photons, but a lower quantum yields than CASN-HP phosphor due to its more absorbed photons. Based on the above, the low-temperature melting process for Sn-P-F-O glass does not damage the phosphor and the enhanced (≥35%) red-emitting CASN-AP PiG will be a promising candidate for essential red component in high quality white LEDs.

A Bright Future for Liquid Functional Materials?

Liquid metals were merely sci-fi fantasy a few decades ago, playing a prominent role in the Terminator film franchise. Current research is leading to an array of emerging functional liquids. Here, we discuss the exciting possibilities of such fluid materials.

Tunable white light in trivalent europium single doped tin fluorophosphates ultra-low melting glass

In recent years, low melting temperature glasses have received wide attention as the hosts of phosphor-converted light emitting diodes (pc-WLED). In this work, a series of trivalent europium doped tin fluorophosphates glasses were prepared by conventional melting method. Under ultraviolet excitation, the blue-green broadband emission from Sn2+ activation centers in the glass matrix and the red emission of Eu3+ ions together constituted a cool white luminescence. The spectra analysis was used to demonstrate the energy transfer between Sn2+ centers and Eu3+ ions. The results showed that Sn2+ and Eu3+ possessed independent intrinsic emission and mutual energy transfer simultaneously. The 5D4 and 5G2 excited states of Eu3+ ion favored the energy transfer to Sn2+ center, the 5L6 excited state of Eu3+ ion would absorb more of the energy by the Sn2+ ground state excitation to contribute on red emission. Therefore, the fluorescent glass can transform cool white light to warm white light by changing the excitation wavelength. The tunable white light is obtained in the WLED devices built with the glass and commercial UV chips.

Concentration-dependent diffusion kinetics of Ti-Al binary system at elevated temperatures: Experiments and modeling

The aim of the present work is to investigate the dependence of concentration gradient on diffusion kinetics of Ti-Al binary system at high temperatures, which is a long-standing physical problem that cannot easily addressed by tradition diffusion couple experiments due to the ultralow melting point of Al and complicated compositions of various titanium aluminides. We conceived and established a simplified Fick-based diffusion model, making use of successive concentration gradient, in combination with experiments, to reveal the concentration-governed diffusion behavior. Our results showed an excellent agreement with currently available diffusion models. Therefore this approach was expected to be extensively applied to other binary system with large deviations in the melting points.

Phenylethynyl-terminated oligoimides with ultra-low melt viscosity derived from 1,4-bis(3,4-dicarboxy phenoxy)benzene dianhydride

Most of the existing polyimide oligomers for resin transfer molding (RTM) processing exhibited high melt viscosity, which can only maintain below 1 Pa·s at 280°C for 2 h, leading to very high process temperatures. So novel RTM-type oligomers with lower and stable melt viscosities are more desirable. Three series of thermoset oligoimides derived from 1,4-bis(3,4-dicarboxy phenoxy)benzene dianhydride and three different aromatic diamines were prepared herein. The diamines included 4,4′-oxydianiline, 2,2′-bis(trifluoromethyl)benzidine (TFDB), and 2-phenyl-4,4′-diaminodiphenyl ether ( p-ODA). 4-Phenylethynylphthalic anhydride was used as an endcapping reagent. Effects of the chemical structures and molecular weights of the oligoimides on their aggregated structures, melt processability, and the thermal and mechanical properties of the cured films were then systematically investigated. X-Ray diffraction results indicated that ODA series oligoimides and TFDB series oligoimides showed crystallinity in various degrees. However, the asymmetric p-ODA enables the p-ODA series oligoimides to exhibit amorphous forms. It was found that the p-ODA-based oligoimide with a molecular weight of 750 g mol−1 showed very low melt viscosity of 1 Pa·s even at 210°C, and the melt viscosity could maintain below 1 Pa·s after isothermal aging for 2 h at any temperature in the range of 200–280°C by rheological measurements. The cured film also showed a high glass transition temperature of 355°C by dynamic mechanical analysis, very good thermal stability by thermogravimetric analysis, and good mechanical properties. It might be more suitable for RTM processes in the future.

Effect of NH4H2PO4 content on properties of P-Sn-W-B glass system with ultra-low melting sealing temperature

The glass structure, thermal and electrical properties and water durability of the P-Sn-W-B glasses, prepared by traditional melt-quenching technique, were examined. The glasses exhibited relatively low transition temperatures (90–150 °C), ultra low sealing temperature (250–300 °C), high electrical resistivity (ρv = 1011–13 Ω·cm), high coefficient of thermal expansion(CTE = 182–230*10−7/K), and excellent water durability, could be used as low melting sealing material. With the increasing NH4H2PO4/P2O5 ratio, the O/P ratio increased, from the EDX analysis. The glass structure changed with the composition, the infrared spectra showed that the PO double bonds, OH bending vibration decreased whereas new bonds like P-O-W formed, enhancing the glass structure, also, the water durability of glass was improved.

Towards long-lifetime high-performance warm w-LEDs: Fabricating chromaticity-tunable glass ceramic using an ultra-low melting Sn-P-F-O glass

The strong demands for “high-power” w-LEDs stimulate development of the all-inorganic glass ceramic (GC) phosphors with admirable thermal/chemical reliabilities. Herein, an ultra-low melting Sn-P-F-O glass was successfully prepared, demonstrating as an appropriate host to accommodate yellow YAG:Ce3+ and red CASN:Eu2+ without degrading their original luminescent properties. The yellow and red GCs yield QE as high as 92.0% and 88.6%, respectively. Moreover, they exhibit excellent resistance to thermal quenching, i.e., only 9.5% and 3.0% decreases in luminescence intensity at 150°C compared with that at room temperature. Remarkably, LED using the YAG:Ce3+/CASN:Eu2+ co-sintered GC as color converter yields bright warm white light with CCT of 3554K, under 350mA current, highlighting a new record in LE of 90.71lm/W among the GC-based warm w-LEDs. Accelerated experiments demonstrate the presently studied GC also exhibits a superior thermal stability, therefore is capable for operating at high power condition for a long time.

Diels–Alder Reversible Thermoset 3D Printing: Isotropic Thermoset Polymers via Fused Filament Fabrication

This study presents a new 3D printing process, the Diels–Alder reversible thermoset (DART) process, and a first generation of printable DART resins, which exhibit thermoset properties at use temperatures, ultralow melt viscosity at print temperatures, smooth part surface finish, and as‐printed isotropic mechanical properties. This study utilizes dynamic covalent chemistry based on reversible furan‐maleimide Diels–Alder linkages in the polymers, which can be decrosslinked and melt‐processed during printing between 90 and 150 °C, and recrosslinked at lower temperatures to their entropically favored state. This study compares the first generation of DART materials to commonly 3D printed high‐toughness thermoplastics. Parts printed from typical fused filament fabrication compatible materials exhibit anisotropy of more than 50% and sometimes upward of 98% in toughness when deformed along the build direction, while the first generation of DART materials exhibit less than 4% toughness reduction when deformed along the build direction. At room temperature, the toughest DART materials exhibit baseline toughness of 18.59 ± 0.91 and 18.36 ± 0.57 MJ m−3 perpendicular and parallel to the build direction, respectively. DART printing will enable chemists, polymer engineers, materials scientists, and industrial designers to translate new robust materials possessing targeted thermomechanical properties, multiaxial toughness, smooth surface finish, and low anisotropy.

WITHDRAWN: Microscopic and macroscopic inspection of ultralow melting point behavior of dimethyl Sulfoxide–Water solutions

WITHDRAWN: Microscopic and macroscopic inspection of ultralow melting point behavior of dimethyl Sulfoxide–Water solutions

Non-Newtonian flow of an ultralow-melting chalcogenide liquid in strongly confined geometry

The flow of high-viscosity liquids inside micrometer-size holes can be substantially different from the flow in the bulk, non-confined state of the same liquid. Such non-Newtonian behavior can be employed to generate structural anisotropy in the frozen-in liquid, i.e., in the glassy state. Here, we report on the observation of non-Newtonian flow of an ultralow melting chalcogenide glass inside a silica microcapillary, leading to a strong deviation of the shear viscosity from its value in the bulk material. In particular, we experimentally show that the viscosity is radius-dependent, which is a clear indication that the microscopic rearrangement of the glass network needs to be considered if the lateral confinement falls below a certain limit. The experiments have been conducted using pressure-assisted melt filling, which provides access to the rheological properties of high-viscosity melt flow under previously inaccessible experimental conditions. The resulting flow-induced structural anisotropy can pave the way towards integration of anisotropic glasses inside hybrid photonic waveguides.

Influence of Melt Viscosity on the Structure and Properties of Electrically Conductive Nanocomposites Produced by Masterbatch Process

Electrically conductive polypropylene nanocomposites containing multi-walled carbon nanotubes were produced by melt blending by dilution of a concentrate masterbatch containing 10 wt.% of filler. In order to promote polymer infiltration within primary agglomerates a ultra-low melt viscosity polypropylene grade has been used for masterbatch production. Moreover, three polypropylenes with different melt viscosities have been used for successive dilutions. Filler dispersion has been assessed by both indirect macroscale analyses and direct morphological investigations. Characterization showed percolation thresholds occurring for very low filler contents. During dilution, lower polymer viscosities lead to more effective residue agglomerates dispersion, hence better electrical properties.

Entropically-driven ring-opening polymerization of cyclic butylene terephthalate: Rheology and kinetics

Cyclic butylene terephthalate oligomers (CBT) with ultra-low melt viscosity can be polymerized into poly (butylene terephthalate) (pCBT) via entropically-driven ring-opening polymerization (ED-ROP) in a short time (ranging from several seconds to 10 min) with no chemical emission and no heat generation during the polymerization process. Due to no heat generation, dynamic rheological measurements were used to monitor the polymerization of CBT from 220 to 250°C. The polymerization was accompanied by a steep increase of the melt viscosity and modulus in isothermal rheological tests, and much faster at higher temperature. With rheological results, reptation theory and Double reptation model were adopted to determine the variation of the molecular weight and concentration with time for pCBT. According to the ED-ROP mechanism of CBT, kinetics equations were also established to simulate the polymerization process. Furthermore, using the results of variation of molecular weight with time for pCBT and kinetics equations, the polymerization rate constants for initiation and propagation steps were evaluated, and the activation energy was also obtained. It was proved that rheological method is a convenient and reliable way to investigate the kinetics of ED-ROP of CBT. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers

Effect of B 2O 3 on Melting Temperature of CaO-Based Ladle Refining Slag

Abstract B 2O 3 is selected as fluxing agent of CaO-based ladle refining slag to decrease the melting temperature as well as to improve the speed of slag forming and the refining efficiency. The effects of B 2O 3 on the melting temperature of two series of refining slags including the low basicity slags (the mass ratio of CaO/SiO 2 is 3 — 4) and the high basicity slags (the mass ratio of CaO/SiO 2 is 5 — 8.75) were investigated. The slag melting temperature was measured using the hemisphere method. The results indicate that the fluxing action of B 2O 3 is better than that of CaF 2 and Al 2O 3. For the CaO-based refining slag with low basicity, the melting temperature is decreased effectively when B 2O 3 is used to substitute for equal mass of CaF 2, Al 2O 3 and SiO 2, respectively. For the CaO-based refining slag with high basicity, when CaF 2 is substituted by B 2O 3, the melting temperature can be decreased remarkably. Especially, when the mass ratios of CaO/Al 2O 3 and CaO/SiO 2 are in the range of 1.1 — 4.0 and 5.25 — 8.0, respectively, the slag melting temperature is lower than 1 300 °C. Therefore, the B 2O 3-containing refining slags with high ratios of CaO/Al 2O 3 and CaO/SiO 2 have ultra low melting temperature.