金属/电介质颗粒复合介质光学双稳的温度效应

应用有效媒质近似，结合自洽平均场理论和谱表示方法，研究了金属电介质颗粒复合介质的光学双稳行为与温度的关系.数值计算了不同的入射频率、体积分数和形状因子下光学双稳的温度效应，结果发现，温度对光学双稳的产生、双稳阈值及阈值宽度有很大影响. 关键词： 复合介质 光学双稳 谱表示 温度     

Electrolytical production of Ni + Mo + Si composite coatings with enhanced content of Si

Ni + Mo + Si composite coatings were prepared by co-deposition of nickel with molybdenum and silicon powders from a nickel solution in which Mo and Si particles were suspended by stirring. The layers have been deposited on a carbon steel substrate (St3S) under galvanostatic conditions. The content of Si in deposited layers was about 2-5 wt.% depending on deposition current density and the value of electric charge. For comparison Ni + Mo composite coatings were obtained under analogous current conditions. Composite coatings of enhanced Si content (15 wt.%) were deposited from an electrolyte in which 40 g/dm³ of Si covered with electroless plated nickel was dispersed. Deposition current density was equal 0.1 A/cm² and the value of electric charge Q = 500 C/cm². The thickness of the coatings was about 100-300 μm depending on their kind, electric charge and the deposition current density. Surface and cross-section morphology were investigated by scanning electron microscope (SEM). All deposited coatings are characterized by great, developed surface area. No internal stresses causing their cracking were observed. Chemical composition of the layers was determined by X-ray fluorescence spectroscopy (XRF) method and quantitative X-ray analysis (QXRD). It was stated, that the content of molybdenum and silicon in Ni + Mo + Si coatings depends on deposition current density and the amount of the powder in bath. The results of structural investigation of the obtained layers by the X-ray diffraction (XRD) method show, that they consist in crystalline Mo or Mo and Si phases built into Ni matrix. Moreover, Ni + Mo + Si composite coatings were modified by thermal treatment. It has been found that the thermal treatment of Ni + Mo + Si composite coatings caused that the new phases (NiSi, Mo₂Ni₃Si and Ni₆Mo₆C_1.06) were obtained.     

Mild synthesis of a Zn(II) metal organic polymer and its hybrid with activated carbon: Application as antibacterial agent and in water treatment by using sonochemistry: Optimization,kinetic and isotherm study

In this work, a room temperature and short method (30 min) for synthesis of nanosized rod-like metal organic polymer (MOP) has been described. Reaction of 1,4-phenylenedioxy diacetic acid with zinc salt leads to the formation of [Zn(C₁₀H₈O₆)(H₂O)₄]_n and subsequently was loaded on activated carbon following sonication and structurally characterized by FTIR, SEM, EDX and XRD analysis. The combination of this new composite with sonication was applied for rapid and efficient adsorption of Bromocresol Purple (BCP). Effects of initial BCP concentration, mass of adsorbent and sonication time on response were investigated and optimized by central composite design (CCD). Analysis of variation (ANOVA) was adapted to experimental data to find best optimum conditions which was set at 15.22 mg L⁻¹, 2.41 min, 0.02 g and 0.009 mg for initial BCP concentration, sonication time and adsorbent mass, respectively. Conduction of similar experiments at specified condition permit achievement of 98.69% removal percentage. 1,4-phenylenedioxy diacetic acid and Zn(NO3)₂.4H₂O which have applied for preparation of MOP are interesting antibacterial properties and accordingly MOP was screened in vitro for their antibacterial actively against Proteus vulgaris bacteria and experimental results reveal this MOP was able to inhibit growth of the tested bacteria. The experimental data were best fitted by pseudo-second order and Langmuir for kinetic model and the adsorption equilibrium isotherm, respectively.     

Microfabrication of stacks of acoustic matching layers for 15 MHz ultrasonic transducers

This paper presents a novel method used to manufacture stacks of multiple matching layers for 15 MHz piezoelectric ultrasonic transducers, using fabrication technology derived from the MEMS industry. The acoustic matching layers were made on a silicon wafer substrate using micromachining techniques, i.e., lithography and etch, to design silicon and polymer layers with the desired acoustic properties. Two matching layer configurations were tested: a double layer structure consisting of a silicon–polymer composite and polymer and a triple layer structure consisting of silicon, composite, and polymer. The composite is a biphase material of silicon and polymer in 2-2 connectivity. The matching layers were manufactured by anisotropic wet etch of a (1 1 0)-oriented Silicon-on-Insulator wafer. The wafer was etched by KOH 40 wt%, to form 83 μm deep and 4.5 mm long trenches that were subsequently filled with Spurr’s epoxy, which has acoustic impedance 2.4 MRayl. This resulted in a stack of three layers: The silicon substrate, a silicon–polymer composite intermediate layer, and a polymer layer on the top. The stacks were bonded to PZT disks to form acoustic transducers and the acoustic performance of the fabricated transducers was tested in a pulse-echo setup, where center frequency, −6 dB relative bandwidth and insertion loss were measured. The transducer with two matching layers was measured to have a relative bandwidth of 70%, two-way insertion loss 18.4 dB and pulse length 196 ns. The transducers with three matching layers had fractional bandwidths from 90% to 93%, two-way insertion loss ranging from 18.3 to 25.4 dB, and pulse lengths 326 and 446 ns. The long pulse lengths of the transducers with three matching layers were attributed to ripple in the passband.     

Preparation, structures and photoluminescent enhancement effect of PbWO4–TiO2 composite nanofilms

A novel route for preparing PbWO₄–TiO₂ nanofilms on a glass substrate is firstly proposed. The collodion is used as a dispersant and film-forming agent. The nanofilms are characterized through SEM, XRD, TG/DTA, PL and IR, respectively. The results of XRD indicate PbWO₄ particles with tetragonal scheelite structure and TiO₂ particles with Anatase phase, and SEM shows they are well dispersed in the substrate. Compared with nanoparticles, when TiO₂ nanoparticles are added in 5% ratio, the PL intensities at 395 nm of PbWO₄ nanofilms are enhanced obviously. IR spectrum reveals a large absorption band between 750 and 870 cm⁻¹, which is the W–O stretching vibration in WO₄ tetrahedron.     

Trace determination of safranin O dye using ultrasound assisted dispersive solid-phase micro extraction: Artificial neural network-genetic algorithm and response surface methodology

In this study, ultrasound assisted dispersive solid-phase micro extraction combined with spectrophotometry (USA-DSPME-UV) method based on activated carbon modified with Fe₂O₃ nanoparticles (Fe₂O₃-NPs-AC) was developed for pre-concentration and determination of safranin O (SO). It is known that the efficiency of USA-DSPME-UV method may be affected by pH, amount of adsorbent, ultrasound time and eluent volume and the extent and magnitude of their contribution on response (in term of main and interaction part) was studied by using central composite design (CCD) and artificial neural network-genetic algorithms (ANN-GA). Accordingly by adjustment of experimental conditions suggested by ANN-GA at pH 6.5, 1.1 mg of adsorbent, 10 min ultrasound and 150 μL of eluent volume led to achievement of best operation performance like low LOD (6.3 ng mL⁻¹) and LOQ (17.5 ng mL⁻¹) in the range of 25–3500 ng mL⁻¹. In following stage, the SO content in real water and wastewater samples with recoveries between 93.27–99.41% with RSD lower than 3% was successfully determined.     

High-power high-stability Q-switched green laser with intracavity frequency doubling of diode-pumped composite ceramic Nd:YAG laser

We successfully obtain high-average-power high-stability Q-switched green laser based on diode-side-pumped composite ceramic Nd:YAG in a straight plano-concave cavity. The temperature distribution in composite ceramic Nd:YAG crystal is numerically analyzed and compared with that of conventional Nd:YAG crystal. By use of a composite ceramic Nd:YAG rod and a type-II high gray track resistance KTP (HGTR-KTP) crystal, a green laser with an average output power of 165 W is obtained at a repetition rate of 25 kHz, with a diode-to-green optical conversion of 14.68%, and a pulse width of 162 ns. To the best of our knowledge, both the output power and optical-to-optical efficiency are the highest values for green laser systems with intracavity frequency doubling of this novel composite ceramic Nd:YAG laser to date. The power fluctuation at around 160 W is lower than 0.3% in 2.5 hours.     

Ni、Co/AAO纳米有序阵列复合结构光吸收特性的比较研究

在多孔阳极氧化铝(AAO)模板中分别沉积金属镍(Ni)、钴(Co),制备了Ni／AAO和Co／AAO纳米有序阵列复合结构,对其光吸收特性进行了比较研究。实验结果表明．相同结构参量的模板中,Ni、Co纳米粒子的表观形状随沉积时间的变化规律基本一致．但Co/AAO及Ni／AAO复合结构的光吸收特性却有较大差异。Ni／AAO复合结构表现出间接带隙半导体的光学特征．而Co／AAO复合结构具有直接带隙半导体的光学特征。同时,随金属沉积量的增加,Ni／AAO吸收边的红移量仅约为13nm．而Co/AAO复合结构的吸收边红移量却超过了80nm。用Maxwell-Garnett(M-G)理论分析了导致二者光吸收特性存在较大差异的主要原因。     

Carbon nanotube-epoxy composites: The role of acid treatment in thermal and electrical conductivity

Wet acid oxidation treatment methods have been widely reported as an effective method to purify and oxidize the surface of industrial multi-walled carbon nanotubes. This work examines the use of a concentrated HNO₃/H₂SO₄ mixture in an attempt to optimize the purification procedure of industrial multi-walled carbon nanotubes with diameter distribution statistics. It is shown that acid treatments of several hours are enough to purify the nanotubes. The electrical and thermal conductivities of epoxy composites containing 0.05–0.25 wt% of an acid-treated multi-walled carbon nanotube have been studied. The electrical conductivity of the composites decreases by more than three orders, whereas the thermal conductivity of the same specimen increases very modestly as a function of the filler content.