Search

Single-component white-light-emitting phosphors based on resonance energy transfer exhibit ultra-high Ra and appropriate CCT.

A series of semi-alicyclic poly(amic acid) varnishes designed for potential applications as the alignment layers for thin-film transistor driven liquid crystal display devices (TFT-LCDs) were prepared from an alicyclic dianhydride, norbornane-2-spiro-α- cyclopentanone-α′-spiro-2″-norbornane-5,5″,6,6″-tetracarboxylic dianhydride (CpODA) and aromatic diamines. Then, the liquid crystal (LC) minicells were fabricated by using the polyimide (PI) as the alignment layers, which were prepared by thermally dehydrating the PAA varnishes at elevated temperatures. The derived PI alignment layers exhibited good thermal stability with the 5% weight loss temperatures higher than 470 °C. In addition, the PI layers showed excellent optical transparency with the transmittances higher than 94.0% at the wavelength of 550 nm with a thickness around 100 nm. The LC cells fabricated with the CpODA-PI alignment layers exhibited good optoelectronic features. The rubbing PI layers could induce the effective alignment of the LC molecules with the pretilt angles in the range of 1.62–2.14°. The voltage holding ratios of the LC cells were higher than 92.00%, and the residual direct voltage values were all lower than 300 mV.

TiO2 is a potential alternative opacifier to ZrSiO4, but it is restricted because it easily causes glaze yellowing due to the formation of rutile. Herein, the CaCO3-TiO2 composite with close interface combination was added into the raw glaze for sanitary ceramics to prepare white glaze with negligible radioactivity. The glaze added CaCO3-TiO2 exhibits the surface properties similar to the glaze added ZrSiO4 and its excellent opacifying effect with L* value of 89–94 is achieved by the crystallization of titanite. Moreover, the optimal glaze added CaCO3-TiO2 shows a white surface with b* value of 2.73, while the glaze added pure TiO2 shows a yellowish surface with b* value of 7−10. Mechanism analysis indicates that the tight interface combination between CaCO3 (CaO) and TiO2 can promote their combination reaction to form perovskite and further promote the formation of titanite. Therefore, the formation of rutile is inhibited, resulting in the white glaze surface.

The modifications of local structure in solid solution are a crucial step to regulate the photoluminescence properties of rare-earth ion-based phosphors. However, the structural diversity of host matrices and the uncertain occupation of activators make it challenging to obtain phosphors with both high stability and tailored emission. Herein, We synthesized a series of β-Ca

It is highly desirable to red shift the emission of Y3Al5O12:Ce3+ phosphor to obtain a warmer correlated color temperature (CCT) in applications for blue-light pumped white-light emitting diodes (w...

A series of luminescent Ba0.79Al10.9O17.14:xEu (x = 0.005–0.12) phosphors were prepared by high-temperature solid-state reaction in air atmosphere. The coexistence of Eu2+ and Eu3+ was observed and verified by photoluminescence (PL) and photoluminescence excitation (PLE) spectra, X-ray photoelectron spectra (XPS), and diffuse reflection spectra. The band emission peaking at 430 nm was assigned to 4F65D–4F7 transition of Eu2+, and another four emissions peaking at 589, 619, 655, and 704 nm were attributed to 4F–4F transitions of 5D0–7F J (J = 1, 2, 3, 4) of Eu3+. The related mechanism of self-reduction was discussed in detail. The color of the Ba0.79Al10.9O17.14:xEu phosphors could be shifted from blue (0.23, 0.10) to red (0.42, 0.27) by doping Li+ ions, and the temperature dependence properties were investigated.

Gene flow patterns and the genetic structure of domesticated crops like cotton are not well understood. Furthermore, marker-assisted breeding of cotton has lagged far behind that of other major crops because the loci associated with cotton traits such as fiber yield and quality have scarcely been identified. In this study, we used 19 microsatellites to first determine the population genetic structure and patterns of gene flow of superior germplasm resources in upland cotton. We then used association analysis to identify which markers were associated with 15 agronomic traits (including ten yield and five fiber quality traits). The results showed that the upland cotton accessions have low levels of genetic diversity (polymorphism information content = 0.427), although extensive gene flow occurred among different ecological and geographic regions. Bayesian clustering analysis indicated that the cotton resources used in this study did not belong to obvious geographic populations, which may be the consequence of a single source of domestication followed by frequent genetic introgression mediated by human transference. A total of 82 maker–trait associations were examined in association analysis and the related ratios for phenotypic variations ranged from 3.04% to 47.14%. Interestingly, nine SSR markers were detected in more than one environmental condition. In addition, 14 SSR markers were co-associated with two or more different traits. It was noteworthy that NAU4860 and NAU5077 markers detected at least in two environments were simultaneously associated with three fiber quality traits (uniformity index, specific breaking strength and micronaire value). In conclusion, these findings provide new insights into the population structure and genetic exchange pattern of cultivated cotton accessions. The quantitative trait loci of domesticated cotton identified will also be very useful for improvement of yield and fiber quality of cotton in molecular breeding programs.

Sialon-SiC composite powders were synthesized from kyanite tailings through the carbothermal reduction nitridation (CRN) technique. Using Sialon-SiC composites to substitute Si3N4 composites via the CRN technique synthesize Sialon/Si3N4-SiC composite refractories. The phase composition, cross section morphology, and the substituent amount of Sialon-SiC composites impact on refractories mechanical properties were investigated, respectively. The optimized synthesis temperature for the CRN reaction was found to be 1550 °C for 4 h with the excess carbon 20%. The substituent amount of Sialon-SiC was 25%, the mechanical properties of Sialon/Si3N4-SiC composite refractories reached optimal performance, which bending strength value was 41.8 MPa and compression strength value was 61.6 MPa.

Cordierite samples were prepared using quartz sand tailings, industrial alumina and magnesite tailings as raw materials by high-temperature reaction. The influence of mineral composition and sintering temperature on the final phase composition and physical properties of cordierite were studied. The results shown that a large number of cordierite generated at 1300 °C. When the ratio of Al2O3/SiO2 equals to 1.08, the flexural strength of samples increased to 27.66 MPa.

Mullite material was prepared from quartz (SiO2) and industrial alumina (γ-Al2O3). The effects of mineral composition and sintering temperature on the final phase composition and physical properties of mullite were investigated. The results shown that a large number of mullite phase was emerged in samples when the ratio of alumina to silica (A/S) was 2.55. At 1500 oC and 1600 oC, the flexural strength of the samples reached to 87.13 MPa and 89.50 MPa, respectively. Consider the environmental protection and energy saving, the optimal sintering temperature was 1500 °C.

The performance and phase behavior of Quartz - Aluminum Matrix Composites at different temperatures were studied. Quartz aluminum matrix composites were prepared by powder metallurgy method. At the temperature that was less than 660.4°C(the melting point of aluminum), a portion of quartz was happened decomposition and revivification to silicon, most aluminum still existed in the form of metal aluminum. All quartz were happened at the temperature that was higher than 660.4°C. When the temperature is 700°C, the compressive strength of S5(added 40% quartz) is up to 46.02MP. The higher the value of compressive strength was, the less the amount of quartz were happened decomposition. At the temperature more than the melting point of aluminum, Quartz was revivification to silicon, aluminum is oxidized to Al2O3. When the amount of silica exceeded 10%, the mechanical properties of composites declined consequently.

The total bauxite reserves of China are about 3.7 billion tons, however the principal and the first-class bauxite reserves account for only about 20%. A large number of coal gangue was accumulated on the surface of earth, which not only encroaches land but also pollutes the environment. In this study, low-grade bauxite with alumina content of 53.18 wt.% originating from Shanxi Yangquan and coal gangue with alumina content of 38.07 wt.% originating from Shanxi Datong were used to synthesize mullite materials. Bauxite and gangue were mixed by the ratio of 1 to 1. The ingredients were prepared according to the alumina content of 45.63 wt.% and 70 wt.%, by adding a certain amount of industrial alumina, respectively. The samples were sintered at 1350°C to 1600°C after being milled, dried and formed. The influence of alumina content and sintering temperature on the phase, microscopic morphology and properties of samples were discussed. The results show that, the main phases of the sample with the alumina content of 70 wt.% were mullite (more than 60 %) and corundum after being sintered for 4h at 1600 °C. The phenomenon of columnar mullite and granular corundum staggering had been observed. The bulk density and the bending strength of sample is 3.21 g/cm3and of 220.73 MPa respectively.

This paper mainly discusses the influences of heating temperatures and CeO2additive contents on the phase transformations of zirconia from zircon ore by carbothermal reduction. The phase transformations of zirconia from zircon ore by carbothermal reduction were monitored by X-ray diffraction. The microstructure of the product was characterized by scanning electron microscopy. The results show that without adding CeO2, the optimized heating temperature of zircon carbothermal reduction was 1600 °C and the main phases of the product were m-ZrO2, ZrC and β-SiC, t-ZrO2; After adding CeO2, the main phase of the products consists of t-ZrO2, m-ZrO2, ZrC and β-SiC when the heating temperature is 1600 °C. CeO2additive can be introduced into zirconia lattice and can cause it to form cerium stabilized zirconia. Zirconia in the product would be turned into partially stabilized zirconia with cerium addition from 5 wt% to 20 wt%. However, the form of zirconia in the product is not changed greatly with the amount of CeO2additive increase.

In this paper, the KNN powders with Li+ substituted (K0.5Na0.5)+ were prepared by the sol-gel method in order to make powders pure, (Na0.50+xK0.50-2xLix) -NbO3 (x=0, 0.04, 0.06, 0.08) ceramics were prepared by pressureless sintering. The phase composition of powders was determined by XRD. The effects of the Li+ substitution on piezoelectric and ferroelectric properties of ceramics were systematically studied for determining optimal Li+ content. Li+ can significantly increase the piezoelectric constant of ceramic. When Li+ content was 0.04, piezoelectric properties of ceramics were the best, d33=115 pC/N, Pr=6.35 μC/cm2, Ec=14.24 kV/cm.

In this study the phase behavior of diatomite during magnesiothermic reduction process was investigated. Two packing routes were adopted to estimate the reduction effectiveness at a low reaction temperature of 650 °C for 2h. The phase and microstructure evolution of diatomite were investigated by XRD, SEM, EDS. The results show that diatomite was sucessessfully reduced by the magnesium vapor and reaction products were Si, MgO, and Mg2Si when the raw diatomite was blended with Mg powder. Mg2Si and MgO were alternatively and incompletely dissolved after being immersed in a 1 M HCl solution for 6 h. Meanwhile, the reactant molar ratio had an important influence on products when the raw diatomite was separated with the Mg powder. A small amount of diatomite was reacted to generate MgO and Mg2Si as the molar ratio of Mg and diatomite was 2:1. By contrast, with the molar ratio increasing to be 10:1, diatomite was completely reacted to be Mg2Si and MgO.

The non-sintering Ti (C,N)-Si3N4-SiC composite refractories were prepared using natural quartz, rutile and silicon carbide particles/powders as the raw materials, phenolic resin and urotropin as a complex binder and silicon powder as the additive. The influence of the binder amount on the density, flexural strength, volume shrinkage and the microstructure of the non-sintering Ti (C,N)-Si3N4-SiC composite refractories was studied in detail. The results showed that the amount of binder has significant effects on the properties of the non-sintering Ti (C,N)-Si3N4-SiC composite refractories. The bulk density decreased and the apparent porosity increased as the amount of binder increased, and the flexural strength increased and then decreased as the amount of binder increased, and the volume shrinkage increased with the increase of the amount of binder. The binder is propitious to the properties of the non-sintering Ti (C,N)-Si3N4-SiC composite refractories, but excessive binder will result in the degradation of properties of the as-fabricated composite refractories, the optimum amount of complex adhesive is 15%.

In this paper, SiC nanowires were successfully synthesized on Si substrate by the thermal evaporation method without the assistance of a metal catalyst. The phase composition, morphology and microstructure of the SiC–SiO 2 core–shell nanowires were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). The SiC nanowires produced grew along the [111] direction and had diameters of 50–100 nm with lengths of several hundreds of microns. The SiC nanowire was composed of a single-crystalline SiC core with a thin amorphous SiO 2 shell. The growth mechanism of the nanowires can be explained by the vapor–solid (VS) process.

Tourmaline has characteristics of repeatedly producing electric dipole polarity transformation. Using FTO glass substrate coated with conductive films as raw materials, the research aims to prepare functional glass materials, which have spontaneous polarization effect, absorption of wideband electromagnetic radiation and high visible light transmittance. This paper applied Magnetron Sputtering deposition technique, studying on tourmaline as target, sputtering on conductive FTO glass, using multiple means to measure and analyze the surface morphology, component, structure, electrical and magnetic properties. And the functions of tourmaline as composite electromagnetic shielding films are also discussed in the paper.

Aluminum-nitrogen six-fold octahedral coordination, [AlN

Ultralong single crystal Sialon nanobelts were prepared on a graphite cover coated with Ni(NO3)2 by facile thermal chemical vapor deposition reactions of Si, Al, and Al2O3 with flowing N2 at 1450 °C. The as-synthesized Sialon nanobelts were up to several millimeters long and several hundred nanometers wide, and they had width/thickness ratios of 5–15. Their growth process was codominated by a Ni-catalytic vapor–liquid–solid (VLS) base-growth mechanism and a vapor–solid (VS) tip-growth mechanism. The former was responsible for the initial nucleation and proto-nanobelt formation of Sialon and the subsequent growth along the [100] direction, and the latter additionally contributed the growth at tips. The room-temperature photoluminescence (PL) spectrum showed that the as-synthesized Sialon nanobelts had a special emission with two maximum peaks at 409 nm (3.03 eV) and 428 nm (2.90 eV) located in the violet-blue spectral range, making possible potential applications in LED and optoelectronic nanodevices.

Silicon nitride (β-Si3N4) nano-belts had been synthesized by used silica bricks and carbon powder as raw materials through carbothermal reduction nitridation. The morphology and microstructure of β-Si3N4 nano-belts were characterized by scanning electron microscopy (SEM/HRSEM), energy disperse spectrum (EDS) and X-ray diffraction (XRD). Results showed that the well-crystallized β-Si3N4 nano-beltes were grown with thinness of 50-150nm and width of 3-5μm. The relatively purer β-Si3N4 were prone to be thin films with thinness of 150nm, while the as-grown SiCN (impurityβ-Si3N4with C elements) were presented as nanorods with cross section length of 150*150nm. Orientation growth mechanism by grain dislocation and vapor-solid (VS) mechanism were both involved in the growth of nanostructures of β-Si3N4 nano-beltes and SiCN nanorods.

In this study, β-Sialon/Al2O3/TiN diphase powder was synthesized using low-grade bauxite and rutile via carbothermal reduction-nitridation. The phase transitions of low-grade bauxite and rutile in the carbothermal reduction and nitridation process were analyzed by XRD, SEM and EDS. The effects of different reaction parameters such as reaction temperature, rutile addition on the phase composition and microstructure of products were analyzed. The results showed that β-Sialon/Al2O3/TiN powder was prepared using low-grade bauxite and rutile as raw materials and coke as reducing agent by carbothermal reduction-nitridation reaction in flowing nitrogen atmosphere of 0.03 MPa at 1350-1375 °C, for 4 h.

Doping perovskite structure ceramics constitute an important type of solid oxides fuel cell (SOFC) cathode materials. In this study, BaCe1-xTaxO3+δ powders were prepared by solid state reaction at 1500oC for 4h. BaCe1-xTaxO3+δ ceramics were pressureless sintered at 1600oC for 5h. The results indicated that the relative density of BaCe1-xTaxO3+δ ceramics reached the range of 84.15 - 90.88%. At the frequency of 1Hz, the conductivity of BaCe0.65Ta0.35O3+δ ceramic samples varied greatly, when the testing temperature rose from room temperature to 900oC in increments of 100oC. The highest conductivity was obtained at 600oC with the value of 6.74×10-5 S/cm.

β-Sialon/Ti(C,N) composites were prepared using low and middle grade bauxite and ilmenite as raw material,while coke as reducing agent in high purity nitrogen atmosphere through carbothermal reducrion-nitridation(CRN).The main phases of low and middle grade bauxite are kaolinire(Al2O3•2SiO2•2H2O) and (Al2O3•H2O)2 and ilmenite mainly contain ilmenite(FeTiO3) and rutile(TiO2).The reaction products of bauxite are the β-Sialon(Z=3,Si3Al3O3N5) while those of ilmenite are TiC and Fe.The results showed that the main phases are β-Sialon,Ti(C,N),Al2O3 and Fe when the reaction temperature is at 1400°C holding for 4 hours(10wt% ilmenite and 90wt% bauxite as raw material).However,β-Sialon decomposes into 21R at 1450°C and into 15R and AlN at 1500°C.So 1400°C is selected as the proper temperature to synthesize β-Sialon/Ti(C,N) composites.At 1400°C,the β-Sialon crystals with the largest quantity grow well and show long column in shape.With the increase of the reacrion temperature β-Sialon begin to decompose,the β-Sialon crystals change to short columnar,with the number decreasing quickly.

Mullite with puncheon-like grains was synthesized by sintering the mixtures of coal gangue and γ-Al2O3 at 1400 °C~1550 °C for 4 h. The phase and microstructure evolution of the mullitization behavior were investigated by XRD, SEM and EDS. Phases of the sintered specimens were mullite, corundum and cristobalite at 1400 °C to 1450 °C. Arise of temperature would enhance mullitization, and total consumption of cristobalite occurred from 1500 °C upward. The in-situ produced primary mullite from gangue upon heating may be seeds for the growth of enenly dispersed mullite puncheons. Specimen sintered at 1550 °C consists of puncheons with an aspect ratio of 2~4, regionally forming an interlocking structure.

Mg2+2+,Al3+ Co-doped Li3V2(PO4)3/C powder was synthesized by sol-gel method under nitrogen. The crystal structure and micrograph ofLi3V2(PO4)3/C powder before and after doping was investigated by XRD, SEM and FT-IR. The effect of Mg2+/Al3+ Co-doping onLi3V2(PO4)3/C powder was discussed. The results indicated that Mg2+2+,Al3+ Co-doping did not change the crystal structure of Li3V2(PO4)3, but decreased the grain size of the as-synthesized powder. The FT-IR analysis indicated that weak Al-O bond was generated after doping.

Ta-doped Li3V2(PO4)3 cathode material coated by carbon was synthesized via a sol-gel method. Effects of Ta5+ doping on the physical structure and electrochemical performances of the Li3V2(PO4)3/C cathode materials were investigated. Compared with the undoped sample, the Ta-doped samples had no excess peaks but the larger particle size and the narrower distribution of the particle size, indicating that Ta5+ entered into the structure of (Li1-5xTax)3V2(PO4)3/C rather than forming any impurities. When x was up to 0.01, the best electrochemical properties of the Ta-doped cathode materials had been displayed at the charge and discharge rate of 0.1C with the voltage of 3.0～4.8V. The analysis of cyclic voltammetry revealed that the polarization of the Li3V2(PO4)3/C cathode materials could be effectively decreased by Ta5+ doping(x=0.01), mainly resulting from the better electronic conductivity.

Doped ceria-based (Gd0.2Ce0.8O1.9, GDC) solid electrolytes were prepared by Solid-phase synthesis method. The effect of doping bismuth oxide and samarium oxide on the phase and microstructure of GDC was investigated. The phase composition was analyzed by the X-ray diffraction (XRD).The single cubic fluorite structure was observed after doping these oxides. Appearance and microstructure of doped ceria-based solid electrolytes were analyzed by the scanning electron microscopy (SEM) and the transmission electron microscopy (TEM). The results showed that the doped trivalent cations had entered into the ceria structure uniformly. The density, porosity rate and water absorption of GDC were measured by Archimedes principle. It indicated that the density of doped GDC solid electrolyte increased with the rising of sintering temperature.

Lanthanum magnesium hexaaluminate (LaMgAl11O19, LMA) has attracted much interest as its widely used in solid state lasers, TV phosphors and fluorescent lamps. In this paper, LaMgAl11O19 ceramic was pressureless sintered at 1650 °C for 10 h in air atmosphere using LaMgAl11O19 powders prepared by solid-state reaction at 1500 °C for 4 h. The result indicated that the synthesis temperature of LaMgAl11O19 powders was about 1500 °C. The LMA ceramic sample was dense and had a microstructure of platelet-like gains. The excitation spectrum shows two wide bands with the peaks at about 254 nm and 265 nm by monitoring the strongest 362 nm emission, and the emission spectra is consisted of a broad band emission with their peaks near 362 nm with a half-width about 5 nm exciting with 265 nm wavelength.

In this paper, the mineral composition and main mineral morphology of bauxite were studied from ZhongXiang deposit, HuBei province. Through Electron Microscope Identification, there are two main rock types, oolitic, bean-like and aphanitic or fine crystalline structure of bauxite. The main mineral morphology is micro-crystalline or flake, crumby forms. The mineral and chemical compositions of samples were investigated by XRD, EPMA analysis tests. The EPMA results showed that Al2O3 content is 47.95% ~ 75.04%, in association with other isomorphous impurities, such as Si, Fe, Ti and Mg in varying proportions. The mineral compositions of bauxite ore are mainly aluminum, iron, silicon minerals, which totally account for from 83.01% to 86.40%. The XRD revealed that diaspore, hematite and kaolinite are the major mineral components in the bauxite ores. The bauxite from ZhongXiang deposits is a type of high diaspore bauxite, partly with clay minerals. Furthermore, the function of bauxite as a good fire-resistant material was discussed.

Sialon powder was synthesized using low grade bauxite as raw materials by carbothermal reduction-nitridation reaction. The influence of synthesizing temperatures (1300°C, 1350°C, 1400°C, 1450°C, 1500°C and 1550°C) on the phases of the final products was studied by XRD technique. β-Sialon (Z=3) formed at 1350°C and decreased when the temperature was higher than 1450°C. The optimizing reaction temperature for preparing Sialon was 1450°C. The Al2O3-SiC/Sialon composite refractories were prepared at 200°C, 400°C and 600°C for 24h with white corundum, brown corundum, SiC, Sialon powders prepared at 1450°C and calcium aluminate cement. The bulk density, apparent porosity, water absorption and bending strength of the Al2O3-SiC/Sialon composite refractories at room temperature were studied. The results show that the bulk density decreased and then increased with the enhancing of the temperature and reached the highest value of 2.43g/cm3 at 200°C. The apparent porosity and water absorption reached the lowest values of 26.68% and 10.99% at 200°C respectively. The bending strength decreased as the temperature increased, reached the highest value of 0.73MPa at 200°C.