Effect of shock wave treatment on luminescence of ZnS:Cu,Cl phosphors

It is shown that shock wave treatment of ZnS:Cu phosphor between synthesis and annealing steps by placing phosphor powder into preservation ampoule and subjecting to the effect of explosion has positive effect on photo- and electroluminescence brightness due to increase of activator (copper) solubility in phosphor matrix and formation of additional Cl_S–Cu_Zn and Cl_S–V_Zn luminescent centers.     

Preparation and properties of thin ZnS:Cu films phosphors

Thin films of ZnS and ZnS:Cu were prepared by an original metalorganic chemical vapour deposition (MOCVD) method under atmospheric pressure onto a glass substrate heated up to 230–250 °C. The film thickness varied from 0.6 to 1 μm. The thin films were doped with Cu and Cl by the thermal treatment during 1 h at 600 °C at atmospheric pressure in the blend composed of a ZnS powder with Cu and Cl compounds. These films were used for fabrication of the thin film electroluminescent (TFEL) devices with a conventional double insulating structure. The structural properties were investigated by use of X-ray diffraction (XRD) techniques and atomic force microscopy (AFM). Electroluminescent (EL) spectra, electrical and EL characteristics were investigated. The EL spectra and characteristics as well as structural parameters depend on the growth conditions and significantly modified after the annealing. Blue color emission with brightness of 10 cd m^− 2 under a sine wave excitation at 60 V and 5 kHz was obtained. The degradation behavior of the TFEL devices with ZnS:[Cu, Cl] films fabricated using an original non-vacuum methods of deposition and annealing is the same as that of commercial thin film phosphor.     

Effect of activator distribution on photo- and X-ray excited luminescence properties of ZnS:Cu,Cl phosphors

ZnS:Cu,Cl phosphors were prepared by conventional solid state reaction with the aid of NaCl-MgCl₂ flux. The copper activator was introduced into the phosphor precursors by three different methods: co-precipitated with ZnS (CP), wet-coated onto ZnS powders (WC), and simply mixed with ZnS in a mortar (SM). The samples were characterized by X-ray powder diffraction, photoluminescence spectra and X-ray excited luminescence spectra. The results show that both photo- and X-ray excited luminescence intensities of the as-prepared ZnS:Cu,Cl phosphors are in the decreasing order of CP > WC > SM. The different copper activator distribution in the phosphors resulting from the different methods was the main reason responsible for the different luminescence intensity, and uniform distribution is beneficial to the luminescence of the phosphors.     

Uniform and continuous silica nanocoatings on ZnS phosphors

The penetration depth of the primary electrons into amorphous silica, anatase titania, Y(2)O(3), ZnO, In(2)O(3), indium and tin oxides is compared at lower voltages. It shows that amorphous silica has the largest penetration depth, thus the silica coatings will lead to minimal energy loss and maximal cathodoluminescence intensity. Almost uniform and continuous silica coatings on ZnS phosphors have successfully been obtained by a sol-gel method with the catalysis of ammonia. Zeta potential analysis shows that the ZnS phosphors are covered almost completely. An adsorption-catalysis-growth mechanism is suggested, and used to explain other ammonia-catalyzed coating processes.     

Effect of magnesium on the performance characteristics of ZnS:Cu,Mn phosphors

We have studied the effect of magnesium added to the starting mixture as MgS or MgCl₂ on the performance characteristics of synthesized ZnS:Cu,Mn phosphor powders. It has been shown that the incorporation of certain amounts of magnesium into the ZnS:Cu,Mn phosphor leads to an increase in photo- and electroluminescence brightness and is favorable for Mn incorporation into the structure of the phosphor. In particular, additional doping of a dc electroluminescent ZnS:Cu,Mn phosphor with 30 mol % Mg ensured not only a shift of its luminescence spectrum to shorter wavelengths, thereby extending the color range of light sources, but also a twofold increase in its brightness.     

ZnS:Sm and ZnS:Cu,Sm electroluminescent phosphors

Electroluminescent ZnS: Sm and ZnS: Cu, Sm phosphors have been prepared and their electroluminescent (el) characteristics have been studied. The time-averagedel brightness follows the Alfrey-Taylor relation over a wide range of frequencies. The constants of this relation have been determined. Theel emission shows one main and one auxiliary peak during each half cycle of the applied voltage. Variation of current with applied voltage has also been investigated.     

Preparation of uniform titania nanocoating on ZnS-based phosphors by a sol–gel process

A sol–gel process has been developed to coat micron-sized ZnS:Cu,Au,Al phosphors with a smooth and uniform layer of amorphous titania having nanosize thickness. The titania nanocoating is based on the hydrolysis and condensation of titanium tetrabutoxide Ti(OBu)₄. Acetylacetone was used to decrease the reactivity of Ti(OBu)₄. The experimental variables such as water concentration, the amount of ZnS particles, and reaction time were investigated. The thickness of the titania nanocoating was homogeneous and can easily be controlled from 20 to 54 nm by adjusting the experimental variables. The as-prepared titania nanocoating was amorphous phase and could be crystallized to anatase phase upon heating at 500 °C in Ar atmosphere.     

Effect of precipitation conditions on the particle size and optical properties of ZnS

Submicron-sized ZnS particles have been prepared by reacting zinc chloride and thiourea in the pH range 8–12. The smallest particles (10–20 nm) have been obtained with the use of sodium hydroxide. Increasing the pH of the solution and the thiourea concentration has been shown to increase the particle size. In the diffuse reflection spectra of the ZnS powders obtained using NaOH, the fundamental absorption edge is shifted by 20 to 30 nm.     

Effect of viscosity on the shock wave profile in dusty gases

Summary The effect of viscosity on the shock wave profile in dusty gases is calculated, considering the temperature dependence of viscosity in the system of four autonomous nonlinear differential equations, which is investigated using the Navier-Stokes equations for the gas phase and the particle phase. This system is reduced to a system of two autonomous nonlinear differential equations by neglecting the heat conductivity (=0). The solution of the system is obtained formally by considering that the velocity of particles in the gas-dynamic shock wave is constant.     

激光冲击处理后Ni基高温合金的性能

对Ni基高温合金进行了激光冲击强化处理,测量了处理后Ni基高温合金的残余应力、表面粗糙度分布规律和疲劳强度．结果表明,激光冲击处理后凹坑内残余压应力值为200—400MPa,其分布服从泊松正态分布规律;承载能力比未冲击试样提高大约150MPa;激光冲击区的粗糙度降低一个等级,凹坑内粗糙度数值分布也服从正态分布规律．激光冲击处理后表面出现了组织细化的硬化层,强化效果明显,残余压应力有极大的提高,有效地提高了抗疲劳寿命．     

Fabrication of ZnS/C microsphere composites with enhanced electromagnetic wave absorption properties

Journal of Materials Science: Materials in Electronics - For electromagnetic wave-absorbing materials, organic-derived carbon materials and metal sulfides are highly preferred. In this paper, ZnS/C...     

Effect of inorganic shells on luminescence properties of ZnS:Ag nanoparticles

The hydrothermally synthesized Ag-doped ZnS (ZnS:Ag) nanoparticles have been coated with inorganic shells by a chemical precipitation method. The ZnS:Ag/ZnS, ZnS:Ag/CdS, and ZnS:Ag/ZnO core–shell nanoparticles with different thickness of ZnS, CdS, and ZnO shells have been prepared. The effects of shells on the luminescence properties of ZnS:Ag cores have been investigated through the photoluminescence (PL) spectra and luminescence stabilities of products. In the core–shell nanoparticles involved here, the ZnO shell can most significantly enhance the luminescence of ZnS:Ag cores. The 450 nm emission intensity of ZnS:Ag/ZnO nanoparticles is up to 125 % of that of ZnS:Ag nanoparticles. However, the ZnO shell can hardly influence the luminescence stability under ultraviolet irradiation. The ZnS shell can only increase the luminescence of ZnS:Ag cores to some extent, but it can improve the luminescence stability under ultraviolet irradiation. Although the CdS shell can improve the luminescence stability to some extent, it quenches the luminescence of ZnS:Ag nanoparticles dramatically.     

自由场传感器外形结构对冲击波测试的影响研究

对目前常用的笔式、杆式、盘式自由场冲击波传感器进行了激波管动态校准,借助matlab语言建立了不同外形结构的系统函数,仿真分析了外形结构对冲击波测试的影响。 激波管校准和仿真结果在爆炸源和传感器在同一高度的冲击波超压测试试验中得到了验证。得出如下结论：杆式传感器所测超压值过冲量最大,超压曲线形状有些失真,正压作用时间偏小;盘式结构所测的超压峰值和正压作用时间误差最小。通过传感器高于爆高的试验发现：当激波从传感器的斜下方传播到传感器时：笔式结构与掠入射时相比变化最小,且所测冲击波超压峰值比真值大;杆式结构变化最大;盘式结构与真值的误差最大。最后给出了在现场测试试验中选用传感器安装结构的一些建议。     

Effect of processing history on the properties of Ag-based tapes

The Bi-system tapes and coils were prepared by the powder-in-tube method. The effect of processing and heat treatment on the properties of the tapes and coils was studied. It is found that the shearing stress produced by the rolling process may destroy the 2223 phase, and the destroyed 2223 phase cannot be recovered by heat treatment, whereas the pressing stress produced by the uniaxial pressing process only makes the 2223 phase grains break, and the broken 2223 phase can be closed by the heat treatment. TheJ _c values of the rolling samples, pressing sample, and the coil with a diameter of 35 mm are over 1.3×10⁴, 2.5×10⁴, and 4×10³ A/cm² (77 K, 0 T), respectively.     

Effect of annealing on the morphology and properties of ZnS:Mn nanoparticles/PVP nanofibers

As one kind of new optoelectronic materials, ZnS:Mn nanoparticles/PVP composite nanofibers are prepared by the electrospinning technique successfully. SEM, XRD, FT-IR spectroscopy, photoluminescence and TEM measurements are employed in the study. By the method of annealing, the effect on the morphology and properties of the composite nanofibers is studied. After annealing treatment, the separating state of the nanofibers is improved obviously, ZnS:Mn nanoparticles are well dispersed in the nanofiber, the PL peak originated from ⁴T₁→⁶A₁ transition of Mn ions shifts from 605 nm to 599 nm. The existence of orange emission peaks confirms that ZnS:Mn nanoparticles are formed in the fibers.     

Effect of Ni-doping on optical and magnetic properties of solvothermally synthesized ZnS wurtzite nanorods

In this study we have reported the effect of Ni-doping on optical and magnetic properties of ZnS nanorods. The diameter and length of low temperature solvothermally synthesized, high quality nanorods are 10 and 50–300 nm respectively as revealed from transmission electron microscopy. From X-ray diffraction, the structure of Ni-doped nanorods was observed as wurtzite with lattice parameters, a = 3.83 and c = 6.26. The band gap of the undoped and doped samples was found to be blue shifted as compared to the bulk counterpart when analyzed with UV–visible spectroscopy. Quenching in photoluminescence spectra was observed in case of Ni-doped nanorods as compared to undoped counterpart. The magnetization as analyzed from vibrating sample magnetometer was found to increase with 1 and 5 % Ni-doping concentration, and decrease with further increase in Ni-doping concentration, i.e., with 10 % Ni-doping.     

六铝酸盐基荧光粉的发光性能

综述了六铝酸盐基荧光粉的结构，以Mn^2 为例介绍了结构对荧光粉发光性能的影响。β-A12O3结构中，由于存在离敏化剂很近的四面体中心位置，Mn^2 占据此位置，从而存在敏化剂和Mn^2 之间的有效能量传递，Mn^2 发绿色光。磁铅矿结构中，由于四面体中心位置离敏化剂的距离太远，从而Mn^2 不发光；在畸变的磁铅矿结构中，由OMe的存在，产生局部离子位置重排，生成新的离敏化剂很近的四面体中心位置，从而存在敏化剂和Mn^2 之间的有效能量传递，使Mn^2 发光。荧光粉结构对性能影响规律的总结可以指导高效荧光粉的合成。     

Effect of annealing on the structural and optical properties of non-coated and silica-coated ZnS:Mn nanoparticles

The Mn²⁺-doped ZnS nanoparticles stabilized by sodium citrate were synthesized through a simple chemical route. Using the ZnS:Mn nanoparticles as seeds, the silica-coated ZnS:Mn nanocomposites were formed in isopropanol by the controlled hydrolysis of tetraethyl orthosilicate. The photoluminescence spectra confirmed that the Mn²⁺ ions were incorporated into the ZnS nanoparticles. The annealing effect on the structural and optical properties of these particles was studied over a range of 100–400 °C. The results of X-ray diffraction and photoluminescence showed that the silica shell not only improved the thermal stability but also resisted the lattice-deformation and oxidation of the particles. The thermal analysis further confirmed that the non-coated ZnS:Mn nanoparticles were unstable beyond 200 °C.