White light emission from blue InGaN LED precoated with conjugated copolymer/quantum dots as hybrid phosphor

In this work we fabricated white LEDs using a blue InGaN LED precoated conjugated copolymer/quantum dots (QDs) composite (green-emitting Poly {(9,9-dioctyl-2,7-divinylenefluorenylene)-alto-co-(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene)}/red-emitting CdSe quantum dots) as a hybrid phosphor. The emission peak wavelengths of the blue and red emissions in the spectra were 462 and 618 nm, respectively. The green-emitting polymer had two emission peaks at 515 and 543 nm. The subpeak of the copolymer (515 nm) was decreased by the absorption of QDs as the ratio of QDs increased, while the emission of the QD (618 nm) increased. Therefore, changes in the CIE-1931 coordinate, color temperature (Tc) and color-rendering index (Ra) were dependent on the QDs to copolymer ratios. The white LED of the hybrid phosphor containing 20 wt.% QDs had a luminous efficiency of 44.2 l m/W at 20 mA with a CIE-1931 coordinate, Tc and Ra of (0.3297, 0.3332), 5620 K and 75.3, respectively.     

Crystal structure transformation and luminescent behavior of the red phosphor for plasma display panels

To improve the chroma of red phosphor for plasma display panels, Eu³⁺ activated phosphors were prepared by combustion method, and were investigated in detail by XRD and PL spectra. With the decreasing of the amount of H₃BO₃, the phosphor crystal structures transform from hexagonal ortho-borate to monoclinic RE₃BO₆, and then to cubic oxide. The dominating emissions of the phosphors also change from ⁵D₀–⁷F₁ transition to ⁵D₀–⁷F₂ transition. Accordingly, CIE coordinates of the phosphors show that x values are increasing while y values are decreasing. Thus, phosphor with higher color purity could be achieved by adjusting the mole ratio of H₃BO₃.     

The efficient fabrication of superconducting NbTi

The fabrication of NbTi material for superconducting applications requires a well-established quality assurance system. The development of defects in the rods and billets can be reduced by closely monitoring important process variables, such as the raw materials, melting procedure, heat treatment and surface condition. Imperfections can be pinpointed by ultrasonic inspection, eddy current methods and hardness testing.     

Preparation and its luminescent properties of AlPO4:Eu phosphor for w-LED applications

Orange-reddish-emitting phosphor AlPO₄:Eu³⁺ were fabricated by solid-state reactions at high temperature. X-ray diffraction analysis revealed that AlPO₄ doped with 3 mol% of Eu³⁺ (AlPO₄:0.03Eu³⁺) was pure orthorhombic phase. The photoluminescence study shows that the intensity of magnetic dipole transition (⁵D₀ → ⁷F₁) at 594 nm dominates over that of electric dipole transition (⁵D₀ → ⁷F₂) at 613 nm. The optimum concentration of Eu³⁺ for the highest luminescence is found to be 3 mol%. The PL excitation spectrum is composed of CTB of Eu-O and excitation lines of Eu³⁺ ions. The strongest excitation lines appeared at 392 nm. The color coordinates, quantum yield and lifetime for AlPO₄:0.03Eu³⁺ were measured. All the spectrum features indicate that AlPO₄:Eu³⁺ might be a promising phosphor for display devices or w-LEDs.     

Synthesis of an acrylic copolymer bearing fluorescent dye pendants and characterization as a luminescence conversion material in fabrication of a luminescence conversion light-emitting diode

A polymerizable arcyl group was incorporated into modified 4-N,N-diphenyl-9-(4-tert-butylphenyl)-1,8-naphthalimide (DBN), and the resulting compound (P-DBN) was copolymerized with methyl methacrylate (MMA) to obtain the corresponding copolymer (PMMA-co-DBN). A DBN/PMMA blend film underwent phase separation upon heating, while PMMA-co-DBN did not exhibit the phase separation problem under the same conditions. However, the fluorescence quantum yield (Ф_rel) of P-DBN was much lower (65%) than that of free DBN, and the Ф_rel of PMMA-co-DBN (36%) was lower still. The luminescent output power of a luminescence conversion light-emitting diode (LUCO LED), fabricated using PMMA-co-DBN, was not detectably changed during 288 h of operation at 20 mA, due to adequate stability of the copolymer under the experimental conditions.     

Eu/Sm ions co-doped white light luminescence SrSiO3 glass-ceramics phosphor for White LED

Eu²⁺/Sm³⁺ co-doped silicate glass was prepared by high temperature melting under reducing atmosphere and the Eu²⁺/Sm³⁺ co-doped SrSiO₃ transparent glass-ceramics were obtained after heat-treatment. X-ray diffraction (XRD) and Raman spectra confirmed the formation of SrSiO₃ nano-crystals in the glass matrix. The photoluminescence excitation (PLE) spectra and photoluminescence (PL) spectra of the samples were measured. A broad emission band from 400 nm to 550 nm due to the 4f⁶5d¹ → 4f⁷ transitions of Eu²⁺ was observed, as well as several sharp emission peaks at 563 nm, 600 nm, 646 nm and 713 nm ascribed to the 4f → 4f transitions of Sm³⁺. The luminescence properties of the glass ceramics with different molar ratio of Eu²⁺/Sm³⁺ were studied and the corresponding chromaticity coordinates were calculated. The ultraviolet light-emitting diode (UV-LED) excitable glass-ceramics emitting white light were obtained by tuning the relative emission intensity of Eu²⁺ and Sm³⁺. The results indicate that the Eu²⁺/Sm³⁺ co-doped SrSiO₃ transparent glass-ceramics can be used as a potential matrix material for White LED under UV-LED excitation.     

An electrochemical fabrication method for extremely thin cylindrical micropin

This paper deals with a slender micropin, which can be used for micromachining. The shaping mechanism in electrochemical etching is investigated on the basis of electrochemical kinetics. The pin profile can be controlled by adjusting the current and voltage level. A mathematical model is derived for controlling the diameter of the micropin.     

An effective round ball tool in electrochemistry process as novel reuse fabrication technology

A reuse fabrication module using micro electrochemistry (MECM) with a round-ball tool to remove the defective In2O3 SnO2 thin film from the surfaces of digital paper display was presented.The etching effect improves that the number of the round-balls decreases for promoting the concentration of electric power and increasing discharge space.Using a small size of the round-ball tool takes less time for the same amount of In2O3 SnO 2 layer removal since the effect of MECM is easily developed for supplying of sufficient electrochemical power.A higher feed rate of the poly ethylene terephthalate (PET) diaphragm combines with enough electric power to drive fast etching rate.A pulsed direct current can improve the effect of dreg discharge and is advantageous to couple this current with the fast feed rate of the workpiece.Through the ultra-precise etching of In2O 3 SnO2,the optoelectronic semiconductor industry can effectively reuse the defective products,reducing production costs.This precision etching process is of high efficiency and requires only a short period of time to remove the In2O3 SnO2 nanostructures.     

An alkaline fusion mechanism for aluminate rare earth phosphor:cation-oxoanion synergies theory

Waste aluminate rare earth phosphor is an important rare earth elements(REEs) secondary resource,which mainly consists of BaMgAl_(10)O_(17):Eu~(2+)(BAM) and CeMgAl_(11)O_(19):Tb~(3+)(CMAT). Alkaline fusion process is widely used to recycle REEs from aluminate phosphor, but the related theory remains imperfect. In this paper,a series of alkaline fusion experiments of CMAT were performed to describe the phase change law of CMAT reactions.Based on comprehensive analysis, cation-oxoanion synergies theory(COST) was proposed to explain the aluminate phosphor structure damage. On the mirror plane of aluminate phosphor crystal structure, alkali metal cations(Na~+, K~+) would substitute rare earth ions, while free oxoanion(OH~-,CO_3~(2-),O_2~(2-)) can combine with rare earth ions. These two ionic forces ensure that rare earth ions can be substituted by cations. Then, the structure is decomposed. Morphological analysis shows that observable expression of COST can be described by shrinking core model after simplification. Reaction rate constant calculated indicates that the reaction degree is nanometers per second. COST provides a more complete mechanism, and it can help improve rare earth recycling technology furtherly.     

Preparation of Eu-activated strontium orthosilicate (Sr1.95SiO4:Eu0.05) phosphor by a sol–gel method and its luminescent properties

Eu²⁺-activated Sr₂SiO₄ phosphor was successfully synthesized by a sol–gel method using sodium silicate and SrO as the starting materials. The wavelength of the emission peak and the emission intensity of the phosphor powders were influenced by the pre-treating temperature. The maximum emission intensity of the phosphor was found as pre-treated at 1200 °C in air and then heated at 1300 °C in the reducing atmosphere (10% H₂ + 90% He). As the pre-treating temperature was <1200 °C, the composition of the phosphor powder was not uniform, which leads to decrease of the emission intensity, whereas >1200 °C, the decrease of the emission intensity may be caused from the reversible phase transformation of Sr₃SiO₅ → Sr₂SiO₄ at 1300 °C, which also shows the red-shift behavior.     

EffectofEr~(3+) and Nd~(3+)doping on the luminescent properties of BaMgAl_(10)O_(17):Euphosphor

BaMgAl10O17:Eu blue phosphors were synthesized and the effect of doping er3+ and Nd3+ ions in the phosphor on the luminescent properties was investigated. When the content of Er3+ and Nd3+ ions is small, the phosphor remains single phase and the luminescent intensity of Eu2+ increases effectively. When Er3+ is doped, the shape of the excitation spectrum of the phosphor in the UV (ultraviolet) region remains unchanged. As Nd3+ is doped in the phosphor, the location and intensity of the two excitation peaks, and the emission intensity ratio excited by corresponding UV change dramatically owing to the alternation of crystal field splitting and level barycenter of 4f65d configuration of Eu2+ ion.     

An efficient approach for the identification of candidate datum set for a nominally flat primary datum feature

The first step in the evaluation of geometric characteristics is to establish the related datums. Correct establishment of datums is vital to the accurate evaluation of related geometric errors. ASME Y14.5.1M-1994 standard specifies a procedure for the establishment of candidate datum set for a nominally flat datum feature. Implementation of this procedure is not a trivial task. In this paper, an efficient and accurate algorithm for the implementation of the above-mentioned procedure is presented. The algorithm has been implemented and is evaluated for its ability to provide accurate results quickly.     

Phase composition and luminescent properties of strontium aluminate long persistence phosphor synthesized by combustion synthesis method with different Sr/Al ratios

Strontium aluminate long persistence phos phors are synthesized by combustion method. By control- ling the raw material ratio （Sr/Al）, the effects of phase composition on subsequent spectroscopic properties of phosphors are studied. Results show that the phase com-position changes from strontium-rich phase to aluminum- rich phase with the decrease of Sr/AI： when the rate of Al/Sr changes from 3：1 to 1：1, the main crystal phase of samples is Sr3Al206, and it exhibits the characteristic fluorescence of Eu^3＋ in the lattice of Sr3Al206; when the rate of Al/Sr is between 1：2 and 2：7, phase composition is the mixture of SrAl204 and SrAl4OT, and it emits the characteristic fluorescence of Eu^2＋ in SrAl204 but not in SrAl4OT; when Al/Sr decreases to 1：4 or even 1：12, the main crystal phase of samples transform into SrAl12019, and the characteristic emission peak is about 470 nm, which corresponds to the characteristic emission of Eu2＋ in SrAl12019. At the end of the article, the influence laws of two different synthesis methods on phase composition of samples between high-temperature solid method and combustion method are compared. Compared with the high-temperature solid method, the rule of influence is similar, but the mole ratio of Al/Sr in products is always higher than the initial ratio of the raw material, and com-pounds like Sr4Al14025 are not obtained by combustion method.     

Synthesis and luminescent properties of GdSrAl3O7:Tb phosphor under VUV/UV excitation

Superfine powder of Tb³⁺ ion-doped aluminates phosphors, GdSrAl₃O₇:Tb³⁺ was synthesized with a precursor prepared by an EDTA-sol–gel method at 900 °C. Field-emission scanning electron-microscopy (FE-SEM) observation indicated a narrow size-distribution of about 150–300 nm for the particles with elliptical shape. Upon excitation with vacuum ultraviolet (VUV) and near UV light excitation, the phosphors show a strong emission line at around 542 nm corresponding to the ⁵D₄ → ⁷F₅ transition of Tb³⁺, and the highest PL intensity at 542 nm was found at a content of about 12 mol% Tb³⁺. As the Tb³⁺ concentration increases, Tb ions strongly cross-relaxation interact resulting in a decrease of the lifetime. The results reveal that GdSrAl₃O₇:Tb³⁺ would be a promising green phosphor for PDP application.     

An efficient linear approximation of acceleration method for milling stability prediction

Chatter stability predictions catch much attention during machining operations in modern automotive and aerospace industry. This paper presents a novel time domain semi-analytical method for milling stability prediction based on linear acceleration approximation. Firstly, the milling dynamics considering the regenerative effect is presented as a linear time-delay system with periodic coefficients. The second step is to equally discretize the time duration of the forced vibration of the tooth passing period into small intervals where acceleration of the flexible cutter is approximated by linearly interpolating between the two boundary values, while the free vibration is analytically solved. Then, recursive formulas with constant recursive matrices are found for the presentation of relations between initial and final cutter motions (including position, velocity and acceleration) of each small time interval. Employing the method of weighted residuals over each time interval, discrete maps are constructed which relate motions of a period to the corresponding values one period earlier. Finally, the eigenvalues of the transition matrix are used to determine stability based on Floquet theory. By using the benchmark examples in literatures, the convergence and computational time of the proposed method are compared with those of the semi-discretization methods (SDMs), full-discretization method (FDM) and numerical integration method (NIM). The results verify the validity of the proposed approach, and the presented method is proved to be computationally highly efficient.     

Recombination studies in a polyfluorene copolymer for photovoltaic applications

We present detailed continuous wave (cw) and transient photoinduced absorption (PA) measurements in thin films of a novel alternating polyfluorene copolymer, poly[2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3-benzo-thiadiazole)] (DiO-PFDTBT), and its blends with the soluble fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) in weight ratios of 1:0, 4:1 and 1:4. We measure the frequency, intensity and temperature dependence of the PA signal in the frequency domain, and compare with the results obtained from the transient PA decay measurements in the time domain. In all blends, the PA spectrum shows a broad high energy PA band ranging from ∼1 eV to 2 eV as well as a low energy band peaking at ∼0.35 eV. We attribute the low energy band to the P₁ transition of polarons and part of the high energy band to the correlated P₂ transition of polarons. Both frequency and time domain measurements show that the high energy band has two decay components, a faster component in the microsecond time regime and a slower component in the millisecond time regime. The slow component is strongly dispersive, whereas the fast component is practically non-dispersive.     

花球状Mg(OH)2的制备及其对重金属离子的快速高效去除(英文)

由MgSO₄废液制备球形花状Mg(OH)₂,并评估其对重金属离子的吸附性能。合适的制备条件为Mg²⁺浓度2 mol/L、Mg²⁺/NH₄OH摩尔比1:0.5、温度120℃和时间1h。由超薄片组成的球形花状Mg(OH)2对重金属离子具有良好的吸附能力,6min即可达到吸附平衡。20℃时Mg(OH)₂对Ni²⁺、Cu²⁺、Zn²⁺、Pb²⁺、Fe³⁺和Co²⁺的最大吸附量分别为58.55、85.84、44.94、485.44、625.00和27.86 mg/g。吸附过程符合Langmuir模型,为单分子层吸附。吸附动力学符合准二级动力学模型,化学吸附是其作用机制。球形花状Mg(OH)₂是合格的重金属离子吸附材料。     

A novel red-emitting phosphors K2Ba (MoO4)2: Eu, Sm and improvement of luminescent properties for light emitting diodes

The novel red-emitting phosphors K₂Ba(MoO₄)₂: Eu³⁺, Sm³⁺ were prepared by solid-state reaction and their crystal structures, photo luminescent characteristics were investigated. The results show that all samples can be excited efficiently by UV (397 nm) and blue (466 nm) light, which are coupled well with the characteristic emission from UVLED and blue LED, respectively. A small amount of Sm³⁺, acting as a sensitizer, increased the energy absorption around 400 nm. In the Eu³⁺-Sm³⁺ co-doped system, both Eu³⁺ and Sm³⁺ f-f transition absorptions are observed in the excitation spectra, the intensities of the main emission line (⁵D₀ → ⁷F₂ transition of Eu³⁺ at 616 nm) are strengthened because of the energy transition from Sm³⁺ to Eu³⁺. The doping concentration of Eu³⁺-Sm³⁺ was optimized. The approach to charge compensation was used: Ba²⁺ → Eu³⁺/Sm³⁺ + X⁻ (X = F, Cl, and Br), and the influence of charge compensation on the luminescent intensity of phosphors is investigated.