Effect of Particle Size and Phase Composition of Titanium Dioxide Nanoparticles on the Photocatalytic Properties

Titanium dioxide (TiO₂) nanoparticles were prepared by the oxidation of titanium tetrachloride (TiCl₄) in a diffusion flame reactor. The average diameter of particles was 15–30 nm and mass fraction of anatase ranged from 40% to 80%. Effects of particle size and phase composition of those TiO₂ nanoparticles on photocatalytic properties such as decomposition of methylene blue, bacteria and ammonia gas were investigated. The degree of decomposition of methylene blue by the TiO₂ nanoparticles under the illumination of the black light was directly proportional to the anatase mass fraction, but inversely to the particle size. The decomposition of bacteria and ammonia gas by the TiO₂ nanoparticles under the illumination of the fluorescent light showed the same trend as in the case of the methylene blue.     

Effect of Pulsed Laser Annealing on Optical Properties of Selenium-Hyperdoped Silicon

Optics and Spectroscopy - Layers of selenium-hyperdoped silicon with dopant concentration of up to (4–6) × 1020 cm–3 that exceeds the limit of equilibrium solubility of this...     

Effect of Processing by Femtosecond Pulsed Laser on Mechanical Properties of Submicrocrystalline Titanium

Effect of femtosecond laser processing on mechanical properties of plates made of submicrocrystalline VT1-0 titanium alloy is studied using active deformation and fatigue testing involving cantilever bending.     

Generation of Soft Ferrite Nanoparticles by Pulsed Laser Ablation in Liquids

We generate Mn–ferrite nanoparticles (NPs) by Nd:YAG (1064 nm) laser irradiation in distilled water. We characterize such NPs in terms of the size distribution, shape and chemical composition using transmission electron microscopy (TEM), energy-dispersive X rays (EDS), and Fourier-transform infrared spectroscopy (FTIR). Using a magnetic force microscope (MFM), we show the magnetic properties of the generated nanoparticles.     

Effects of Gold and Silver Nanoparticles on Optical Bistability of Titanium Dioxide Nanocolloid

Physics of the Solid State - In this study, titanium dioxide (TiO2) nanocolloid was synthesized through sol–gel method, and nonlinear optical properties were studied using z-scan method. The...     

脉冲激光烧蚀过程中靶材表面熔融前温度分布与激光功率密度分布的研究

用较为符合实际的高斯分布表示了脉冲激光输出功率密度分布，讨论了脉冲激光功率密度分布函数形状变化对烧蚀过程中靶材表面熔融前温度分布的影响。建立了考虑热源项的热传导方程，并给出了相应的边界条件。以Si为例，用有限差分方法模拟了温度随时间、位置的变化规律，模拟过程中强调了对边界条件的处理，使整体截断误差保持最小。通过改变脉冲激光功率密度分布函数的形状，分析了温度分布的变化。结果表明，相比恒定脉冲功率密度输出，功率密度高斯分布的激光束与靶材作用时高温阶段的温度变化率变大，靶材表面熔融时刻热扩散距离增加；当激光器上升沿变陡时，在有效作用时间内温度上升得更快，对加工区域周围热效应的影响明显减弱，而热扩散距离变小。     

Effect of Laser Fluence on the Structural and Optical Properties of Tantalum Oxide Films Ablated by Pulsed Laser

The influence of laser fluence on the properties of thin films of tantalum oxide is studied in this paper, varying the laser fluence from 5.7 to 8.3 J/cm². Thin films of tantalum oxide were deposited on glass substrates using pulsed-laser ablation technique. X-ray diffraction studies confirm the amorphous/nanocrystalline nature of all the films irrespective of the laser fluence. The Tauc plot analysis suggests that tantalum oxide is an indirect band gap material, whose band gap decreases with increase in laser fluence. The refractive index of the films is found to decrease with increase in laser fluence but the extinction coefficient of the films increases with increase in laser fluence. Fourier transform infrared studies suggest the use of tantalum oxide thin films as oxygen sensors. Micro-Raman analysis reveals the sensitiveness of Ta-O-Ta and Ta-O vibration modes to laser fluence. Among all the films, the film deposited at a laser fluence of 7 J/cm² is found to be superior in quality.     

Pulsed Laser Ablation for Tin Dioxide: Nucleation,Growth, and Microstructures

Pulsed-laser ablation approaches are being developed for the growth of oxide thin films as versatile platform for advanced applications. Semiconducting SnO ₂ thin film is of fundamental importance in the advancement of microdevices. In this review, SnO ₂ thin films of various microstructures have been made using the pulsed-laser deposition method. The microstructural aspects include tetragonal, porous, and orthorhombic structure characteristics. The quantum-dots and dynamic simulations of SnO ₂ nanocrystals have blossomed into a submonolayer regime devoted to the nucleation and growth for these functional films. SnO ₂ thin films with some of the microstructural features may have great implications for the development of novel prototype gas sensors and transparent conduction electrodes.     

室温条件下脉冲CO激光辐射特性

CO气体分子发射激光需要在低温(液氮温度附近)时才容易实现。为在常温条件下实现CO的激光输出,采用横向激励大气压(TEA)脉冲放电的方式对CO气体分子在室温条件下的红外发光辐射性能进行了实验研究。在实验所限定的参数条件下,没有获得FO波段激光辐射,仅实现了FB波段的激光输出。典型的指标为:电光转换效率1%,中心波长5.3μm,辐射能量0.22 J,辐射脉宽(FWHM)700 ns,相当于辐射的峰值功率达到0.3 mW左右;当以500 Hz放电脉冲重复频率运转时,常温条件下还获得了大于百瓦量级的高平均功率辐射输出。     

激光刻蚀法制备Pd纳米颗粒及其光谱特性初探

用Nd:YAG脉冲激光器1 064 nm激发光在二次去离子水中制备了Pd胶体.此体系中Pd颗粒表面不存在杂质离子,为"化学纯净".刻蚀后将Pd胶体沉积在铝基底上形成一层Pd岛膜.紫外-可见吸收光谱表明Pd胶体在200～800 nm测量范围内没有出现特征吸收峰,说明Pd胶体的吸收光谱并不能反映Pd胶体中Pd颗粒的粒径分布等信息.SEM显示Pd岛膜由Pd纳米颗粒组成,其平均粒径在200 nm左右.以101-3mo/·L-1的4-巯基吡啶(4MPY)为探针分子对Pd胶体和Pd岛膜的表面增强拉曼散射(SERS)进行了研究.结果显示,在Pd胶体中没有获得4MPY的SERS信号;Pd岛膜是一种非常高效的活性增强基底,从实验数据估算得出其增强因子约为8.7×104.SERS光谱分析显示4MPY分子通过S原子以倾斜的方式吸附于Pd岛膜表面;与Pd岛膜表面相比,4MPY分子在Ag岛膜上更趋于采用垂直于表面的吸附取向.     

Effect of Different Substrate Temperature on Sb-Doped ZnO Thin Films Prepared by Pulsed Laser Deposition on Sapphire Substrates

Sb-doped ZnO thin films are deposited on c-plane sapphire substrates by pulsed laser deposition. Hall results indicate that the conductivity of the Sb-doped ZnO thin films is strongly dependent on the substrate temperature. The sample deposited at the temperature of 550°C exhibits p-type conductivity. It gives a resistivity of 15.25Ω＆#12539;cm, with a Hall mobility of 1.79cm2V-1s-1 and a carrier concentration of 2.290×1017cm-3 at room temperature. The x-ray diffraction indicates that the Sb-doped ZnO thin films deposited in the range of 450-650°C are high c-axis oriented. Low-temperature photoluminescence spectra indicate that the sample deposited at 550°C shows the strong acceptor-bound exciton （A0X） emission.     

Properties of Ferrofluid Nanoparticles Prepared by Coprecipitation and Acid Treatment

A new stable acid water-based CoFe₂O₄ ferrofluid is prepared by coprecipitation and acid treatment. The properties of the nanoparticles forming the ferrofluid are examined by means of X-ray diffraction, vibrating sample magnetometer, scanning tunneling microscopy, transmission electron microscopy and annihilation technique. The results show that the particles are cubic CoFe₂O₄ nanoparticles, which have an average diameter of 12.2nm and are coated with a low density porous amorphous layer. The CoFe₂O₄ particles in an acid aqueous medium exist in two kinds of forms, one is a single spherical particle and another is an aggregation of several spherical particles.     

Evaluation of Morphology and Size Distribution of Silicon and Titanium Oxide Nanoparticles Generated by Laser Ablation

Nanometer-sized particles of silicon and titanium oxide were generated by irradiating solid targets using a nanosecond pulsed-Nd : YAG laser in a low pressure atmosphere. A low pressure differential mobility analyzer (LP-DMA) was used to classify the size of the generated particles. The LP-DMA and electron microscopes (SEM and TEM) were used to measure the change in the size distribution and morphology of the generated particles with laser power density and system pressure. The size distribution of both silicon and titanium oxide ranged from two to one hundred nanometers in diameter depending on the laser power density and pressure. From the high resolution TEM observation and electron diffraction, it was found that the generated titanium oxide nanoparticles were composed of a core of faceted metallic single crystals with an oxide layer 'shell.     

脉冲激光诱导Cu靶产生发光羽的特性分析

通过在不同的环境气压下拍摄脉冲激光烧蚀金属Cu诱导产生的发光羽,获取了不同区域具有不同颜色特征的发光羽照片.结果发现:发光羽的颜色随环境气压的改变而变化.采用空间分辨光谱技术,测定了激光诱导金属Cu靶产生发光羽辐射强度的空间分布,以及不同烧蚀环境气压对发光羽辐射强度的影响.研究了脉冲激光烧蚀Cu表面诱导发光的动力学过程,建立了可能的发光羽分区模型,对发光羽的不同区域发光粒子的激发机理进行了探讨,并用之定性地解释了所观察的实验现象.结果分析表明:脉冲激光诱导Cu产生的发光羽可以分为三个区域,不同区域的发光机理不同,Cu原子和Cu离子的激发机理不完全相同.     

退火温度及退火气氛对ZnO薄膜的结构及发光性能的影响

采用脉冲激光沉积技术在Si/蓝宝石衬底上制备了ZnO薄膜,结合快速退火设备研究了不同退火温度(500~900℃)及退火气氛(N2,O2)对薄膜的结构及其发光性能的影响。并优化条件得到具有最小半峰全宽及最大晶粒尺寸的薄膜。X射线衍射(XRD)结果表明:氮气氛下退火的ZnO薄膜最佳退火温度为900℃;氧气氛下退火的ZnO薄膜最佳退火温度为800℃。红外(IR)光谱中,退火后Zn-O特征振动峰红移,说明在退火过程中,原子重新排布后占据较低能量位置;同样的退火温度下,氮气氛下退火的薄膜质量更优。同步辐射光电子能谱(synchrotron-based XPS)分别表征了未退火及N2,O2下900℃退火的ZnO薄膜,分峰拟合结果表明氧气氛下退火产生更多的氧空位。结构表征结合光致发光(PL)谱表明绿光的发光峰与氧空位有关。     

Laser Ablation of Titanium in Cryogenic and Room-Temperature Liquids

The results of processing of an OT4-0 titanium plate surface in media of C₂H₅OH + H₂O and liquid argon by radiation of a pulse-periodic Nd:YAG laser with subnanosecond pulses are presented. A change in current-carrying properties of structures synthesized in C₂H₅OH + H₂O is studied. The effect of subsequent influence of HNO₃ + HF acid solution on laser-induced structures is considered.     

飞秒激光烧蚀合成Y_2O_3∶Pr~(3+),Yb~(3+)上转换发光材料

利用飞秒激光烧蚀方法合成了Y2O3∶Pr3+,Yb3+纳米颗粒并对其上转换发光性质进行了研究。对合成产物的形貌分析显示,在一定的激光烧蚀功率密度下,即可制备出小尺寸的纳米颗粒,提高激光功率密度可以得到更高的纳米颗粒产量,所获得的纳米颗粒尺寸小于50 nm。荧光测试结果表明,Y2O3∶Pr3+,Yb3+纳米颗粒具有510 nm为中心的上转换发光带,上转换发光随纳米颗粒数量的增加而增强。