Dynamics of ions produced by laser ablation of ceramic Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and Al at 193 nm

We study the dynamics of ions produced upon ablation of Al and ceramic Al₂O₃ targets using nanosecond laser pulses at 193 nm (6.4 eV) as a function of the laser fluence from threshold up to 12 J cm⁻². An electrical (Langmuir) probe located at 40 mm from the target surface has been used for determining the ion yield and calculating the kinetic energy distributions. The results for both targets show the existence of a significant amount of ions having kinetic energies >200 eV (≈20% around threshold fluence), and kinetic energies are up to >1.5 keV. The results are related with the existence of direct photonionization processes caused by the photon energy of the laser being higher than the ionization potential of Al (5.98 eV). Comparison of the ion yield when ablating the two types of targets for fluences above threshold to data reported in the literature suggests that the magnitude of the yield and its threshold are parameters depending on the thermal properties of the target rather than on the laser wavelength. Around threshold, the different behavior of ion yield when ablating Al and Al₂O₃ targets suggests that the threshold for neutral aluminium and ion species in the case of ablation of the Al₂O₃ target must be similar.     

Synthesis and characterization of platinum nano sized particles by laser ablation in C<Subscript>2</Subscript>H<Subscript>6</Subscript>O<Subscript>2</Subscript> solution

Platinum nano sized particles (Pt NPs) are superior catalysts for many intentions, such as glucose sensors, cancer therapy, gas sensors, etc. Here, Pt NPs were produced by pulsed laser ablation in C₂H₆O₂ solution using Q-switched Nd:YAG laser, for the first time. Then, the influence of the laser fluence during synthesis of them was investigated; and they were characterized by UV–vis spectroscopy, TEM, FE-SEM, XRD, FT-IR, and Raman spectroscopy. The results showed that with increasing laser fluence, the mean particle size of the spherical NPs enhanced. Meanwhile, they had a polycrystalline cubic structure. Correspondingly, the plasmon peak position of generated NPs in the absorption spectra shifted from 257 to 266 nm, with a rise of laser fluence. The IR and Raman spectroscopy was used to achieve the information about the surface state of Pt NPs. We propose that the optimum adjusted laser fluence is an important factor to increase the ablation efficiency.     

丙烯酰胺聚合物与氧化铝晶体相互作用的分子动力学模拟

将丙烯酰胺单体分别与丙烯酸(AA)、阳离子单体丙烯酰氧乙基二甲基乙基溴化铵(DMB)、疏水性单体丙烯酸十八酯(OA)共聚,分别得到阴离子聚丙烯酰胺P(AA-co-AM)、阳离子聚丙烯酰胺P(DMB-co-AM)、非离子聚丙烯酰胺P(AM)和疏水性聚丙烯酰 胺P(OA-co-AM)等四种丙烯酰胺高分子絮凝剂. 用分子动力学方法,模拟计算了四种聚丙烯酰胺絮凝剂与氧化铝晶体(012)晶面的相互作用,以获得相应的形变能,结合能及理论排序,为阐释四种高分子絮凝剂的絮凝作用机理提供理论依据. 研究结果表明：四种聚合物分子相对Al₂O₃(012)面的初始位置均已贴近Al₂O₃(012)面,且絮凝剂分子中的O原子与Al₂O₃(012)面的Al原子之间存在强烈的相互作用;与Al₂O₃(012)晶面结合的高分子絮凝剂发生扭曲变形,但形变能远小于相应的非键作用能. Al₂O₃(012)晶面结合能的大小排序为P(DMB-co-AM)>P(OA-co-AM)>P(AA-co-AM)>P(AM), 显示四种絮凝剂中P(DMB-co-AM)的絮凝性能最佳,PAM絮凝效果最差.     

Influence of Synthetic Polymer on Aqueous Anionic Surfactant (SDBS) Micelle Investigated by FT-IR and Ultrasonic Study

The ultrasonic velocity, absorption, density and viscosity measurements were used to study the interaction of PEG, PVP and PVA with anionic surfactant — sodium dodecyl benzene sulfonate (SDBS) in aqueous solutions of different concentrations and temperatures, namely, 303, 313 and 323 K. The properties of SDBS with increasing polymer concentration (0.2–1.2%) were investigated. Interaction of SDBS with polymer was found to involve the binding of surfactant with the polymer molecule followed by the usual micellization; from the observed values the related acoustical parameters are calculated and their variation are discussed. The FT-IR spectrum was also used to characterize these samples.     

Generation and characterization of NiO nanoparticles by continuous wave fiber laser ablation in liquid

Pulsed laser ablation in liquid (PLAL) has been widely applied for the generation of nanoparticles (NPs). We report on the generation of NiO NPs using a high-power, high-brightness continuous wave (CW) fiber laser source at a wavelength of 1,070 nm. Characterization of such NPs in terms of size distribution, shape, chemical composition, and phase structure was carried out by transmission electron microscopy (TEM), high-resolution TEM equipped with energy-dispersive X-ray (EDX), and X-ray diffraction (XRD). The results revealed the formation of NiO NPs in water with an average size of 12.6 nm. The addition of anionic surfactant sodium dodecyl sulfate (SDS) reduced the size of NiO NPs down to 10.4 nm. The shape of the NPs was also affected by the SDS, showing the change of shapes from spherical domination in water to tetragonal with increased SDS concentrations. Furthermore, the NiO NPs generated in water and SDS solutions were dual phase containing both cubic and rhombohedral structures. It was also found that the NiO NPs were single crystalline in nature irrespective of the size and shape.     

Spectroscopic characterization approach to study surfactants effect on ZnO2 nanoparticles synthesis by laser ablation process

Zinc peroxide nanoparticles having grain size less than 5 nm were synthesized using pulsed laser ablation in aqueous solution in the presence of different surfactants and solid zinc target in 3% H₂O₂. The effect of surfactants on the optical and structure of ZnO₂ was studied by applying different spectroscopic techniques. Structural properties and grain size of the synthesized nanoparticles were studied using XRD method. The presence of the cubic phase of zinc peroxide in all samples was confirmed with XRD, and the grain sizes were 4.7, 3.7, 3.3 and 2.8 nm in pure H₂O₂, and H₂O₂ mixed with SDS, CTAB and OGM respectively. For optical characterization, FTIR transmittance spectra of ZnO₂ nanoparticles prepared with and without surfactants show a characteristic ZnO₂ absorption at 435-445 cm⁻¹. FTIR spectrum revealed that the adsorbed surfactants on zinc peroxide disappeared in case of CTAB and OGM while it appears in case of SDS. This could be due to high critical micelles SDS concentration comparing with others which is attributed to the adsorption anionic nature of this surfactant. Both FTIR and UV-vis spectra show a red shift in the presence of SDS and blue shift in the presence of CTAB and OGM. The blue shift in the absorption edge indicates the quantum confinement property of nanoparticles. The zinc peroxide nanoparticles prepared in additives-free media was also characterized by Raman spectra which show the characteristic peaks at 830-840 and 420-440 cm⁻¹.     

Influence of the plasma parameters on the properties of aluminum oxide thin films deposited by laser ablation

The plasma produced by the ablation of a high purity Al₂O₃ target, using the fundamental line (1064 nm) of a Nd:YAG laser, was characterized. The laser fluence was varied in order to study its effect on the characteristics of the produced plasma as well as on the properties of the material deposited. Optical emission spectroscopy (OES) was used to determine the type of excited species present in the plasma. The mean kinetic energy of the ions and the maximum plasma density were determined from the time of flight (TOF) curves, obtained with a planar Langmuir probe. The obtained results reveal that the fast peak in the probe curve could be attributed to Al III, while the slow peak corresponds to the Al II. Aluminum oxide thin films were then deposited under the same conditions of the diagnosed plasma, in an attempt to correlate the plasma parameters with the properties of the deposited material. It was found that when Al II ion energies are lower than 461.0 eV the films deposited have structural characteristics similar to that of α-Al₂O₃, whereas at ion energies greater than 461.0 eV amorphous material was obtained.     

Structural, vibrational, thermal, and electrical properties of PVA/PVP biodegradable polymer blend electrolyte with CH3COONH4

A biodegradable solid polymer blend electrolyte was prepared by using polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) polymers with different molecular weight percentages (wt.%) of ammonium acetate, and its structural, thermal, vibrational, and electrical properties were evaluated. The polymer blend electrolyte is prepared using solution casting technique, with water as a solvent. X-ray diffraction shows that the incorporation of ammonium acetate into the polymeric matrix causes decrease in the crystallinity degree of the samples. The Fourier transform infrared spectroscopy and laser Raman studies confirm the complex formation between the polymer and salt. Differential scanning calorimerty shows that the thermal stability of the polymer blend electrolyte and the glass transition temperature decreased as the concentration of ammonium acetate increased. The ionic conductivity of the prepared polymer electrolyte was found by AC impedance spectroscopic analysis. A maximum conductivity of 8.12?×?10^?5 Scm^?1 was observed for the composition of 50 PVA/50 PVP/30 wt.% of CH₃COONH₄.     

Hydrophilic Cu3BiS3 Nanoparticles for Computed Tomography Imaging and Photothermal Therapy

Hydrophilic Cu₃BiS₃ nanoparticles (NPs) have been prepared using the thermal decomposition of precursor complexes in oily‐mixed solvent followed by coating the produced Cu₃BiS₃ NPs with polyvinylpyrrolidone (PVP). The resulting Cu₃BiS₃/PVP NPs remain stable in aqueous solutions over a long period of time, and meanwhile, they show low in vitro cytotoxicity and negligible toxicity to mice in vivo. Cu₃BiS₃/PVP NPs could operate as an efficient dual‐modal contrast agent to simultaneously enhance X‐ray computed tomography imaging and photothermal imaging of tumor model in vivo. Moreover, highly efficient ablation of cancer cells both in vitro and in vivo has been successfully achieved by combining Cu₃BiS₃/PVP NPs with near‐infrared (NIR) laser irradiation. All of the positive results in this study highlight that Cu₃BiS₃/PVP NPs could serve as a promising platform for cancer diagnosis and therapy.     

Magnesium ion conducting polyvinyl alcohol–polyvinyl pyrrolidone-based blend polymer electrolyte

Structural, thermal, electrical and electrochemical behaviour of polymer blend electrolytes comprising polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) as host polymers and Mg(ClO₄)₂ as dopant salt have been investigated. The changes in the structural properties on the incorporation of dopant in the blends were investigated by XRD and FTIR analyses. Thermal properties of pure PVA–PVP blend and their complexes were examined by DSC to measure how the thermal transitions of the prepared films were affected by different concentration of Mg(ClO₄)₂. The ionic conductivity and dielectric behaviour were explored using A.C. impedance spectroscopy. The trend of ionic conductivity increases almost proportionally to the content of magnesium salt and can be related to an increase of amorphous phase at high level of dopant salt. The electrochemical stability of the optimum conducting blend polymer electrolyte is found to be ～3.5 V. The Mg²⁺ transference number for the sample with optimized conductivity was found to be 0.31.     

Sonochemical synthesis of supersaturated Ga–Al liquid-alloy fine particles and Al3+-doped γ-Ga2O3 nanoparticles by direct oxidation at near room temperature

In this study, we investigated the fabrication of supersaturated gallium (Ga)–aluminum (Al) liquid alloy and Al³⁺-doped γ-Ga₂O₃ nanoparticles (NPs) at near room temperature (60 °C) using sonochemical and sonophysical effects. Supersaturated Ga–Al liquid alloy microparticles (D_av = 1.72 µm) were formed and stabilized at 60 °C by the thermal nonequilibrium field provided by sonochemical hot spots. Compared with liquid Ga, supersaturated Ga–Al liquid alloy was rapidly oxidized to a uniform oxide without Al₂O₃ or Al deposition. Thus, ultrafine Al³⁺-doped γ-Ga₂O₃ NPs were obtained after only 1 h of ultrasonic irradiation at 60 °C. The oxidation of liquid Ga was remarkably accelerated by alloying with metallic Al and ultrasonic irradiation, and the time was shortened. The average diameter and surface area of the γ-Ga₂O₃-based NPs were 59 nm and 181 m²/g, respectively. Compared with γ-Ga₂O₃, the optical bandgap of the Al³⁺-doped γ-Ga₂O₃ NPs was broadened, and the thermal stability improved, indicating Al³⁺-doping into the γ-Ga₂O₃ lattice. However, the lattice constant of γ-Ga₂O₃ was almost unchanged with or without Al³⁺-doping. Al³⁺ was introduced into the defect sites of Ga³⁺, which were massively induced in the defective spinel structure during ultrasonic processing. Therefore, sonochemical processing, which provides nonequilibrium reaction fields, is suitable for the synthesis of supersaturated and metastable materials in metals and ceramics fields.     

Vanadium-Al2O3 nanostructured thin films prepared by pulsed laser deposition: Optical switching

The formation and optical response of VO_x nanoparticles embedded in amorphous aluminium oxide (Al₂O₃) thin films by pulsed laser deposition is studied. The thin films have been grown by alternate laser ablation of V and Al₂O₃ targets, which has resulted in a multilayer structure with embedded nanoparticles. The V content has been varied by changing the number of pulses on the V target. It is found that VO_x nanoparticles with dimensions around 5 nm have been formed. The structural analysis shows that the vanadium nanoparticles are oxidized, although probably there is not a unique oxide phase for each sample. The films show a different optical response depending on their vanadium content. Optical switching as a function of temperature has been observed for the two films with the highest vanadium content, at transition temperatures of about −20 °C and 315 °C thus suggesting the presence of nanoparticles with compositions V₄O₇ and V₂O₅, respectively.     

溶胶-凝胶方法制备ZrO2及聚合物掺杂ZrO2单层光学增反射膜

以丙醇锆(Zr(OPr)₄)为原料，乙酸(HAc)为络合剂，聚乙二醇(PEG200)和聚乙烯吡咯烷酮(PVP)为大分子添加剂，在乙醇体系中成功合成了ZrO₂及聚合物掺杂ZrO₂溶胶.用旋涂法在K9玻璃基片上制备单层光学增反射膜.借助小角X射线散射和激光动态光散射技术研究胶体的微结构.采用傅里叶变换红外光谱、差示扫描量热分析、X射线衍射分析、原子力显微镜、紫外/可见/近红外透射光谱以及椭偏仪对薄膜的结构和光学性能进行表征.用输出波长为1064 关键词： 二氧化锆 溶胶-凝胶 增反射膜 激光损伤     

Characterisation of combined positive-negative photoresists by excimer laser ablation

Novel photopolymers containing side groups based on o-methoxycinnamylidenemalonic acid, which undergo selective photo-crosslinking without destruction of the polymer backbone upon irradiation at 5>395 nm, have been developed for potential applications as combined positive-negative resists and multilayer resists. An XeCl excimer laser (5=308 nm, F=20 ns) was used as the irradiation source to study the ablation and microstructuring characteristics of the polymers. The materials were structured before and after crosslinking. The ablation rate was analysed by varying the fluence (0.01-10 J/cm²) and the number of pulses for a given irradiation area. Etch rates of about 2 7m per pulse at a fluence of 9 J/cm² could be achieved for all polymers. The polymer with triazene groups reveals a higher etch rate at low fluences (less than 300 mJ/cm²) than the polymer without a triazene group. The experimentally observed threshold fluence for the triazene-containing polymer is about 30 mJ/cm². Using a Schwarzschild-type reflection objective (152), microstructures with a resolution in the micron range were produced on both polymer films. The quality of the structures was evaluated by scanning electron microscopy. The results indicate that the new polymers could be used as resists for excimer laser ablation lithography.     

Morphology and composition on Al surface irradiated by femtosecond laser pulses

We study the surface chemicals and structures of aluminum plates irradiated by scanning femtosecond laser pulses in air for a wide range of laser fluence from 0.38 to 33.6 J/cm². X-ray photoelectron spectroscopy and X-ray diffraction analyses indicate clearly that crystalline anorthic Al(OH)₃ is formed under femtosecond laser pulse irradiation. Besides aluminum hydroxide, crystalline Al₂O₃ is also found in the samples irradiated at high laser fluence. Field emission scanning electron microscopy demonstrates that the surfaces of the samples irradiated with low laser fluence are colloidal-like and that nanoparticles with a few nanometers in size are embedded in glue-like substances. For high laser fluence irradiated samples, the surfaces are highly porous and covered by nanoparticles with uniform size of less than 20 nm.     

A thermal model for the ablation of polymers by lasers and high intensity ion pulses

The results for the ablation of polymers by High-Intensity Pulsed Ion Beams (HIPIB) as well as by laser pulses of different wavelengths and pulse widths are discussed. A thermal model is proposed that reproduces all available experimental data. An Arrhenius type relation is assumed for the ablation velocityw(T) =w ₀ exp (–T ₁/T). Once the two parametersw ₀ andT ₁ are known for a certain polymer the model allows one to predict the ablation rate as a function of laser wavelength, fluence, and pulse width and for HIPIB pulses.     

Ablation mechanism study on metallic materials with a 10 ps laser under high fluence

Single shot ablation of metallic materials of aluminium, titanium alloy (Ti6Al4V) and gold has been studied with 10 picoseconds (ps) laser pulses experimentally and theoretically. The ablation rate variation at high fluence was explained by a simplified predictive model based on critical-point phase separation (CPPS) theory. A comparison between experimental and numerical results inferred that CPPS may well be the dominant ablation mechanism for high fluence laser ablation at 10 ps laser duration.     

SMA-g-MPEG comb-like polymer as a dispersant for Al2O3 suspensions

SMA-g-MPEG comb-like polymer is first employed as the dispersant of Al₂O₃ suspensions in this paper. The comb-like polymer has anionic polycarboxylate backbone, which makes the polymer easily absorbed on the cationic surface of Al₂O₃ particles; on the other hand, the comb-like polymer has hydrophilic MPEG side chains, which extend into the solution to provide steric repulsion after the comb-like polymer is absorbed on the surface of Al₂O₃ particles. The adsorption behavior, zeta potential, apparent viscosity, granularity and TEM images of the Al₂O₃ suspensions using SMA-g-MPEG as dispersant are investigated. The addition of SMA-g-MPEG improves the dispersibility and decreases the apparent viscosity of the Al₂O₃ suspension observably. The impacts of the length of side chains on the dispersion of Al₂O₃ suspensions are particularly discussed. The adsorbed molecular number of the dispersant decreased by increasing the length of side chains. The zeta potential of Al₂O₃ suspension is more negative by using comb-like polymer with shorter side chains. Based on the steric repulsion and adsorbed molecular number, SMA-g-MPEG with moderate length of side chain is found to have the best dispersibility for Al₂O₃ suspension.     

Synthesis of silver nanoparticles and antimony oxide nanocrystals by pulsed laser ablation in liquid media

Pulsed laser ablation in liquid media (PLALM) is a prominent technique for the controlled fabrication of nanomaterials via rapid reactive quenching of ablated species at the interface between the plasma and liquid. Results on nanoparticles and nanocrystals formed by PLALM of silver (Ag) and antimony (Sb) solid targets in different liquid environments (Sodium Dodecyl Sulfate, distilled water) are presented. These experiments were done by irradiating solid targets of Ag and Sb with a nanosecond pulsed Nd:YAG laser output of wavelength 532 nm. Nanoparticles of silver and nanocrystals of antimony oxide (Sb₂O₃) obtained were characterized using UV-Vis spectrometry, Scanning Electron Microscopy (SEM), transmission electron microscopy (TEM), X-ray Energy Dispersion Analysis (EDAX) and X-ray diffractometry (XRD). The morphology of nanomaterials formed is studied as a function of surfactant environment. The silver nanoparticles obtained were spherical of size in the order of 10–35 nm in solution of SDS having different concentrations. In case of the Sb target, ablation was performed in two different molarities of SDS solution and distilled water. Nanocrystals of Sb₂O₃ in powder form having cubic and orthorhombic phases were formed in SDS solution and as fibers of nanocrystals of cubic Sb₂O₃ in distilled water.     

Laser (a pulsed Nd:YAG) cladding of AZ91D magnesium alloy with Al and Al2O3 powders

The laser surface cladding of an AZ91D magnesium alloy with Al and Al₂O₃ powders was investigated using a pulsed Nd:YAG laser. The optimum ratio of Al to Al₂O₃ and the suitable range of laser processing parameters were identified. The resulting microstructure in the modified surface layer was examined and the wear resistance property was evaluated. The results show that the wear resistance of the laser treated samples was much superior to that of the untreated samples.