Synthesis of Glass Nanofibers Using Femtosecond Laser Radiation Under Ambient Condition

We report the unique growth of nanofibers in silica and borosilicate glass using femtosecond laser radiation at 8 MHz repetition rate and a pulse width of 214 fs in air at atmospheric pressure. The nanofibers are grown perpendicular to the substrate surface from the molten material in laser-drilled microvias where they intertwine and bundle up above the surface. The fibers are few tens of nanometers in thickness and up to several millimeters in length. Further, it is found that at some places nanoparticles are attached to the fiber surface along its length. Nanofiber growth is explained by the process of nanojets formed in the molten liquid due to pressure gradient induced from the laser pulses and subsequently drawn into fibers by the intense plasma pressure. The attachment of nanoparticles is due to the condensation of vapor in the plasma.     

Cutting and Machining Energetic Materials with a Femtosecond Laser

A femtosecond (fs) laser has been used as a tool for solving many problems involving access, machining, disassembly, inspection and avoidance of undesirable hazardous waste streams in systems containing energetic materials. Because of the unique properties of the interaction of ultrashort laser pulses with matter, the femtosecond laser can be used to safely cut these energetic materials in a precise manner without creating an unacceptable waste stream. Many types of secondary high explosives (HE) and propellants have been cut with the laser for a variety of applications ranging from disassembly of aging conventional weapons (demilitarization), inspection of energetic components of aging systems to creating unique shapes of HE for purposes of initiation and detonation physics studies. Hundreds of samples of energetic materials have been cut with the fs laser without ignition and, in most cases, without changing the surface morphology of the cut surfaces. The laser has also been useful in cutting nonenergetic components in close proximity to energetic materials.     

Femtosecond-laser-induced nanostructure formation and surface modification of diamond-like carbon film

This paper reports the pump and probe experiment for in situ reflectivity measurements in the femtosecond laser ablation that brings about nanoscale modification of diamond-like carbon (DLC) film. The characteristic reflectivity changes observed demonstrate that the formation of periodic nanostructure is preceded by a change in bonding structure of DLC in the ablation at low fluences. We have observed a coherent nonlinear wave-mixing signal that can resolve the ultrafast interaction processes for the nanoscale modification on the film surface. Based on the results obtained, a model of the interaction process is proposed.     

Femtosecond laser modification of an array of vertically aligned carbon nanotubes intercalated with Fe phase nanoparticles

Femtosecond lasers (FSL) are playing an increasingly important role in materials research, characterization, and modification. Due to an extremely short pulse width, interactions of FSL irradiation with solid surfaces attract special interest, and a number of unusual phenomena resulted in the formation of new materials are expected. Here, we report on a new nanostructure observed after the interaction of FSL irradiation with arrays of vertically aligned carbon nanotubes (CNTs) intercalated with iron phase catalyst nanoparticles. It was revealed that the FSL laser ablation transforms the topmost layer of CNT array into iron phase nanospheres (40 to 680 nm in diameter) located at the tip of the CNT bundles of conical shape. Besides, the smaller nanospheres (10 to 30 nm in diameter) are found to be beaded at the sides of these bundles. Some of the larger nanospheres are encapsulated into carbon shells, which sometime are found to contain CNTs. The mechanism of creation of such nanostructures is proposed.     

Robust Non-Wetting PTFE Surfaces by Femtosecond Laser Machining

Nature shows many examples of surfaces with extraordinary wettability, which can often be associated with particular air-trapping surface patterns. Here, robust non-wetting surfaces have been created by femtosecond laser ablation of polytetrafluoroethylene (PTFE). The laser-created surface structure resembles a forest of entangled fibers, which support structural superhydrophobicity even when the surface chemistry is changed by gold coating. SEM analysis showed that the degree of entanglement of hairs and the depth of the forest pattern correlates positively with accumulated laser fluence and can thus be influenced by altering various laser process parameters. The resulting fibrous surfaces exhibit a tremendous decrease in wettability compared to smooth PTFE surfaces; droplets impacting the virgin or gold coated PTFE forest do not wet the surface but bounce off. Exploratory bioadhesion experiments showed that the surfaces are truly air-trapping and do not support cell adhesion. Therewith, the created surfaces successfully mimic biological surfaces such as insect wings with robust anti-wetting behavior and potential for antiadhesive applications. In addition, the fabrication can be carried out in one process step, and our results clearly show the insensitivity of the resulting non-wetting behavior to variations in the process parameters, both of which make it a strong candidate for industrial applications.     

Femtosecond pulsed laser deposition of silicon thin films

Optimisation of femtosecond pulsed laser deposition parameters for the fabrication of silicon thin films is discussed. Substrate temperature, gas pressure and gas type are used to better understand the deposition process and optimise it for the fabrication of high-quality thin films designed for optical and optoelectronic applications.     

液膜法制备STM探针研究

本文采用液膜代替传统的电解质溶液,用电化学腐蚀法制备了STM用W探针,细致研究了电压、液膜中电解质浓度和补充滴加电解质的时间间隔的单因素实验和正交实验对探针制备成功率的影响。采用该法得到的探针针尖表面光滑,显示出极好的对称性,在较佳的条件下,曲率半径最小达到48 nm,超过了进口的商业化STM探针的水平,可以进行实际应用。     

Laser damage threshold of Ge8As23S69 films irradiated under single- and multiple-pulse femtosecond laser

In this study, the single- and multiple-pulse laser-induced surface damage characteristics of the Ge₈As₂₃S₆₉ chalcogenide film under the femtosecond laser irradiation were experimentally investigated. The 1-on-1 and S-on-1 methods were utilized to measure the femtosecond laser damage by using single and multiple pulses, respectively. The femtosecond laser-induced damage threshold (LIDT) was obtained using linear regression method by measuring the damage morphology under different pulse energies and pulse numbers of the femtosecond laser. Results show that the LIDT of the film under single-pulse radiation is higher than that under multiple-pulse radiation because of accumulation and defect effects. For the single-pulse radiation, LIDT is attributed to the field enhancement effect, multiphoton ionization, and avalanche ionization. The single-pulse damage threshold of Ge₈As₂₃S₆₉ films is 232.548 mJ/cm². For the multiple-pulse radiation, the LIDT of the film decreases with increasing pulse number due to accumulation and defect effects.     

飞秒激光诱导玻璃功能微结构

玻璃是一种传统材料,通过利用外场对玻璃进行空间选择性的微结构调控,发挥微结构的协同效应、量子效应和干涉效应等,可以赋予玻璃高功能和全新性能.本文阐述了近年来发展迅速的飞秒激光与玻璃相互作用的特征,介绍了我们利用飞秒激光诱导折射率变化直写三维光波导、微光栅和光散射型光纤衰减器,进行活性离子(稀土、过渡和重金属离子)的价态操作及应用和发现的基于飞秒激光与玻璃非线性相互作用的偏振依赖的纳米光栅形成机制.     

Vascularization of Cell-Laden Microfibres by Femtosecond Laser Processing

To face the increasing demand for organ transplantation, currently the development of tissue engineering appears as the best opportunity to effectively regenerate functional tissues and organs. However, these approaches still face the lack of an efficient method to produce an efficient vascularization system. To answer these issues, the formation of an intra-volume channel within a three-dimensional, scaffold free, mature, and cell-covered collagen microfibre is here investigated through laser-induced cavitation. An intra-volume channel was formed upon irradiation with a near-infrared, femtosecond laser beam, focused with a high numerical aperture lens. The laser beam directly crossed the surface of a dense and living-cell bilayer and was focused behind the bilayer to induce channel formation in the hydrogel core while preserving the cell bilayer. Channel formation was assessed through confocal microscopy. Channel generation inside the hydrogel core was enhanced by the formation of voluminous cavitation bubbles with a lifetime longer than 30 s, which also improved intra-volume channel durability. Twenty-four hours after laser processing, cellular viability dropped due to a lack of sufficient hydration for processing longer than 10 min. However, the processing automation could drastically reduce the cellular mortality, this way enabling the formation of hollowed microfibres with a high density of living-cell outer bilayer.     

维生素C催化微波合成乙酰水杨酸

以水杨酸和乙酸酐为原料,采用维生素C作催化剂微波辐射合成乙酰水杨酸。考察了催化剂用量、微波功率、辐射时间对反应产率的影响。优选出的较佳反应条件为:水杨酸6.3 g和新蒸馏乙酸酐9 mL时,用维生素C 0.5 g的催化剂,在400 W的功率下催化40 s。在此条件下,乙酰水杨酸产率达60.60%。     

Femtosecond laser microstructuring of alumina toughened zirconia for surface functionalization of dental implants

The continuous need for high-performance implants that can withstand mechanical loads while promoting implant integration into bone has focused recent research on the surface modification of hard ceramics. Their properties of biocompatibility, high mechanical and fatigue resistance and aesthetic color have contributed to its succefull applications in dentistry. Alumina toughened Zirconia (ATZ) has been gaining attention as a material for dental implants applications due to its advanced mechanical properties and minimal degradation at body temperature. Still, in order to improve tissue response to this bioinert material, additional modifications are desirable. Improving the surface functionality of this ceramic could lead to enhanced implant-tissue interaction and subsequently, a successful implant integration.In this work, microtopographies were developed on the surface of Alumina toughened Zirconia using an ultrafast laser methodology, aiming at improving the cellular response to this ceramic. Microscale grooves and grid-like geometries were produced on ATZ ceramics by femtosecond laser ablation, with a pulse width of 150 fs, wavelength of 800 nm and repetition rate of 1 kHz. The variation of surface topography, roughness, chemistry and wettability with different laser processing parameters was examined.Cell-surface interactions were evaluated for 7 days on both microstructured surfaces and a non-treated control with pre-osteoblasts, MC3T3-E1 cells. Both surface topographies showed to improve cell response, with increased metabolic activity when compared to the untreated control and modulating cell morphology up to 7 days.The obtained results suggest that femtosecond laser texturing may be a suitable non-contact methodology for creating tunable micro-scale surface topography on ATZ ceramics to enhance the biological response.     

羟乙基磺酸钠催化微波合成乙酰水杨酸的研究

以水杨酸和乙酸酐为原料,采用羟乙基磺酸钠作催化剂微波辐射合成乙酰水杨酸。考察了催化剂用量、微波功率、微波辐射时间对反应产率的影响。优选出的较佳反应条件为:取6.3 g水杨酸和9 mL乙酸酐时,催化剂羟乙基磺酸钠用量0.7 g,微波功率400 W,微波辐射时间120 s。在此条件下,乙酰水杨酸产率达79.02%。     

研磨法合成查尔酮

采用研磨法在无溶剂和室温条件下以苯甲醛和苯乙酮为原料合成了查尔酮,讨论了碱性催化剂的筛选,催化剂用量,反应物配比等反应条件。优化后的条件是：室温下研磨20rain,以NaOH／Na2CO,作为催化剂,苯甲醛、苯乙酮和催化剂的最佳摩尔比为6：4：2,选用75％乙醇溶液为重结晶溶剂,查尔酮的产率可以达到80．6％。     

Laser ablation behaviors of vacuum plasma sprayed ZrC-based coatings

ZrC, ZrC-30 vol% SiC, and ZrC-30 vol% TiC coatings were fabricated by vacuum plasma spray and the laser ablation behaviors were evaluated by a CO₂ laser beam under two heat fluxes (15.9 and 25.5 MW/m²). The phase compositions and microstructures of the coatings after ablation were investigated and the effect of SiC and TiC additives was analyzed. The results showed that the ZrC–SiC coating displayed better ablation resistance compared with the ZrC and ZrC–TiC coatings under 15.9 MW/m² heat flux. While the ZrC–TiC coating exhibited the improved ablation resistance under 25.5 MW/m² heat flux. The continuous and integral ZrO₂–SiO₂ scale provided protective effect for the ZrC–SiC coating. A liquid ZrO₂–TiO₂ layer which owned self-healing ability was formed for the ZrC–TiC coating in both heat fluxes. However, the state of the formed liquid, like amount, viscosity, evaporation, and decomposition, was influenced by the environment and was vital for the ablation resistance. This work might give a clue for designing ultrahigh-temperature ceramics as potential laser ablation–resistant coating materials.     

微波辐射法合成葡萄糖苯酚树脂胶黏剂

以葡萄糖代替甲醛合成一种新的环保型酚醛树脂胶黏剂。在碱性条件下以微波加热法合成葡萄糖苯酚树脂胶黏剂、通过正交实验获得最佳反应条件,同时以此方法对树脂的固化条件进行了研究。微波加热条件下合成葡萄糖苯酚树脂胶黏剂的最佳条件是：葡萄糖：苯酚=7：1;pH：12;催化剂用量：1．4％;反应时间：6min。实验证明,微波辐射波法可以成功合成葡萄糖苯酚树脂胶黏剂,且该胶黏剂是一种环保型胶黏剂。     

催化剂对正硅酸乙酯常压合成SiO2气凝胶的研究

以正硅酸乙酯为硅源,分别以 HF 和 HF/氨水为催化剂,通过溶胶-凝胶法常压制备 SiO2 气凝胶.研究表明以 HF 为催化剂能有效地加快反应的速度,当以 HF/氨水为催化剂时对产品的合成和性能产生更大的影响.用热重分析仪(TG-DTA)、比表面(BET)、XRD、傅里叶变换红外光谱仪、激光粒度仪等仪器对两种产品微结构测试结果表明:两种产品都是非晶纳米多孔结构,体积平均粒径小于 20μm,为介孔结构.     

Preparation and Characterization of Mordenite Thin Films via Pulsed Laser Deposition

Zeolite thin films are interesting for their potential application in membrane based separations, catalysis, and molecular sensing. Mordenite is a one-dimensional channel type zeolite that has been used in alcohol/water separations. Pulsed-laser deposition has been used to prepare partially oriented, crystalline mordenite thin films on stainless steel foil, and frits as well as carbon fibers and DAM-1 particles. Preliminary results for pervaporation of isopropanol/H₂O mixtures using mordenite membranes indicate separation factors of 133 and 459 at room temperature and 76°C, respectively.     

Femtosecond Ti: Sa ultra short-pulse laser irradiation effects on the properties and morphology of the zirconia surface after ageing

Femtosecond pulses from a Ti:Sapphire laser were used to irradiate specimens of yttria-stabilised (35% mol) tetragonal zirconia (Y-TZP) with the purpose of studying the effects of the irradiations on their surface properties and morphology after ageing. Zirconia disks were divided into eight groups (n = 32) according to their surface treatment and subsequent ageing: Control: no treatment; sandblasting: Al₂O₃ sandblasting 50 μm; and ultrashort laser pulses irradiation with 25 μJ pulses, considering two different scanning steps based on the width between two grooves. These groups were duplicated and submitted to ageing. The surfaces were analysed using scanning electron microscopy (SEM), and X-ray diffraction. A finite element analysis, a biaxial flexure test, as well as fractographic and Weibull analyses, were performed. The strengths of the disks were statistically different for the treatment factor, and the principal stresses seemed to be concentrated at the centre of the specimens, as predicted by the computer simulations. Ageing decreased the strengths for all groups and increased the Weibull modulus for the laser group with the 40 μm-width between two grooves. The sandblasting group presented the highest monoclinic phase peak. Although the most significant strength was found within the sandblasting group, the phase transformation was favourable to the laser groups. The Weibull modulus was higher for the laser group with the 60 μm-width between two grooves, confirming the highest homogeneity of its failure distribution. Regardless of the surface treatment, strength was decreased with ageing in all groups. The femtosecond Ti:Sa ultra-short pulse laser irradiation can be suggested as an alternative to the gold standard sandblasting in long-term Y-TZP zirconia rehabilitations, such as crowns and veneers.