Laser Irradiation Test Research Articles

Multi-functional and durable anti-corrosion coatings with hydrophobic, freeze time retardation and photothermal properties by means of a simple spraying method

In this study, a composite material consisting of perfluorinated quaternary silane-modified graphene oxide and modified CeO2 nanoparticles was prepared, and a hydrophobic, corrosion-resistant, self-cleaning and anti-icing composite coating was prepared by combining the composite material with polyphenylene sulfide (PPS) through high-temperature curing in a simple spraying method for the protection of iron sheets. The results show that the composite coating has excellent corrosion resistance, strong mechanical properties and certain photothermal properties. When the content of perfluorinated quaternary silane modified CeO2 nanoparticles with graphene oxide (P-GKC) was 10 wt%, the composite coating had a water contact angle of 145.6 ± 3° and a sliding angle of 5 ± 1°, with good hydrophobicity and low surface energy. Meanwhile, the hydrophobic modification of perfluoroquaternary silanes reduced the surface energy of the particles in the composite coatings and greatly improved the hydrophobicity. Surface temperature and laser irradiation tests of the composite coatings showed that the photothermal properties of the composite coatings were better than those of the single PPS and graphene oxide (GO) coatings, with good photothermal cycling stability.The Tafel curves and the EIS results showed that the PPS/10 wt% P-GKC composite coatings had the best corrosion resistance, with a corrosion current density of 5.01 × 10−9A cm−2. After 200 h of salt spray test in 3.5 % NaCl environment, the PPS/10 wt% P-GKC composite coating still has good substrate protection effect, which provides a practical basis for the research of composite coating anticorrosion.

New Biocompatible Technique Based on the Use of a Laser to Control the Whitefly Bemisia tabaci

The whitefly Bemisia tabaci is among the most important agricultural pests in the world and one of the world’s top 10 most invasive insect pests. Bemisia tabaci is associated with severe yield and quality losses, mainly due to the transmission of plant viruses, as in the case of common beans (Phaseolus vulgaris L.). Reducing insecticide applications is a research priority, e.g., developing innovative and clean tools such as electromagnetic waves. The present work aims to determine the effective parameters of laser to reduce the Bemisia tabaci population in common beans. Preliminary assays were conducted by manually irradiating continuous-wave laser beams with different wavelengths (444 nm, 527 nm, and 640 nm) and optical intensities directly on the insects. Among these, the most effective wavelength was 444 nm. Later, we repeated the experiments using a homemade automated system to control the exposure time (t1 = 1 s, t2 = 2 s, t3 = 3 s and t4 = 4 s) of whiteflies to the incident beam at different optical intensities (I1 ≈ 10 Wcm−2, I2 ≈ 4 Wcm−2, I3 ≈ 2 Wcm−2). We have achieved 100% insect mortality by irradiating 454 nm laser wavelength on the 3rd instar nymphs of Bemisia tabaci, with the following parameters: I1(t1), I2(t3) and I3(t4). Moreover, the laser irradiation test did not affect plant yield and development, revealing that our preliminary results present a photonic technique that could control whiteflies without harming the plants’ development.

Energy aggregation properties of TiO2-silica composite aerogel under ultra-high-energy (7 kW·cm-2) continuous-wave laser irradiation

TiO2, a light-shielding agent for silica aerogels, is widely used in optical limiting and photocatalysis, but its application in high-energy lasers is extremely limited. We added TiO2 to silica aerogel in three different ways to get the best resistance to high energy laser. Through microstructure analysis and high energy laser irradiation test results, it is concluded that direct deposition of TiO2 nanoparticles can achieve the best laser resistance synergistic effect with silica aerogel. A thermal barrier temperature difference of 1275 °C was generated with a material thickness of 7.5 mm. Comparing the microscopic pore structure before and after high-energy laser irradiation, it was observed that the phase transition destruction of the TiO2–silica composite aerogel was completely different from that of pure silica aerogel. The TiO2–silica composite aerogel showed no signs of breakdown within 2 min of continuous-wave (CW) laser irradiation with power of 7 kW·cm-2. By changing the amount of TiO2 added, we also obtained the general trend of this synergistic effect, extended the mathematical model “maximum energy transfer radius (METR)”, and advanced the application of this material in the field of high energy laser protection.

Investigation of the effect of nanosecond laser pulses processing on the microstructure and fatigue resistance of commercially pure titanium

The effect has been studied of treatment with nanosecond laser pulses on the fatigue resistance of plate samples of recrystallized (grain size of the order of 2-3 μm) commercially pure titanium (grade VT1-0) under cyclic tensile loading. The results of investigations by scanning and transmission electron microscopy of the subsurface layer microstructure of the alloy under study after exposure to nanosecond laser irradiation and subsequent fatigue tests are presented. Keywords: titanium, surface, pulsed nanosecond laser irradiation, shock-wave action, fatigue properties.

Исследование влияния обработки лазерными импульсами наносекундной длительности на микроструктуру и сопротивление усталости технически чистого титана

The effect of treatment with nanosecond laser pulses on the fatigue resistance of plate samples of recrystallized (grain size of the order of 2-3 µm) commercially pure titanium (grade VT1-0) under cyclic tensile loading is studied. The results of investigations by methods of scanning and transmission electron microscopy of the microstructure of the subsurface layer of the alloy under study after exposure to nanosecond laser irradiation and subsequent fatigue tests are presented.

Thermal shock resistance of 4D-inplane carbon/carbon composite based on micro-structurally informed effective properties

The thermal shock resistance of the 4D-inplane carbon/carbon composite has been predicted using the simulations of the laser irradiation test. Firstly, the effective homogenized temperature dependent properties of the carbon/carbon (c/c) composite have been predicted using realistic unit cell. The meso-scale unit cell has been reconstructed using the reconstructed images of the composite obtained through X-Ray computed tomography. The meso unit cell includes the realistic microstructural features such as fiber bundle distortions and irregular shaped big voids in the geometry. The bundles of the reconstructed unit cell are further considered as a unidirectional composite and micro unit cells are utilized to define their effective behavior. Two-scale asymptotic expansion homogenization method has been used along with finite element method and periodic boundary conditions for the prediction of effective properties. Later, thermo-mechanical transient two-dimensional analysis of a cylindrical specimen has been conducted. The irradiation laser beam parameters e.g. diameters of beam and heat flux have been varied to study the critical values of laser power density (LPD). The maximum shear strength failure criterion is used to define the ultimate state. The obtained trend of the variation of LPD is validated using the data available in the literature for 2D C/C composites. It has been observed that the present results are in good agreement with those existing in the literature. The thermal shock resistant capability of 4DIN C/C composite is found around 10–18 times higher than that of 2D C/C composite.

Magneto-optical Dy2O3 ceramics with optical grade

Optical grade Dy2O3 ceramics was successfully produced by adding a small amount of ZrO2 as a sintering aid and hot isostatic pressing treatment at 1500∘C after pre-sintering at 1550∘C. No residual pores, grain boundary phases, or second phases were detected inside the transparent ceramics. Since birefringence was not observed under the polarizer, the produced Dy2O3 ceramics is an optically isotropic body. There was almost no beam distortion during the laser irradiation test, and the optical loss was extremely small (<0.1%/cm). The Verdet constant was 422radT-1m-1 at a wavelength of 633 nm, and the extinction ratio was 34 dB.

Higher mechanical and thermal properties of Cu-rGO composites

Here, the author fabricated copper-reduced graphene oxide composites by using conventional powder metallurgy technique by varying the amount of reduced graphene oxide. SEM and Raman analysis were used to characterize micro-morphology and disorder in the bulk composites. Tensile, thermal and microhardness testing were conducted to observe the behaviour of Cu-rGO composites. Interesting results were obtained after testing; the materials ultimate tensile strength, ductility, thermal conductivity and hardness were increased significantly compared to pure Cu. An increase in 31% ultimate tensile strength, ~200% ductility, 9.5% thermal conductivity and 90% hardness were noticed by using a very small amount of rGO 0.5 wt%. Laser irradiation test was also proved the good heat dissipation properties of Cu-rGO composites by increasing the amount of rGO. This extraordinary simultaneous increase in mechanical and thermal properties is remarkable and gave us a new way for the fabrication of higher strength-ductility and strength-conductivity based composites.

The Impact of Multiple-Cell Charge Generation on Multiple-Cell Upset in a 20-nm Bulk SRAM

Single-event upsets induced by multiple-cell charge generation are studied in a 20-nm bulk SRAM by performing laser irradiation tests. The single-pulse two-photon absorption is utilized to simulate charge generation over multiple SRAM cells. The analysis of fail bit maps reveals that the physical topology of fail bits strongly depends on data patterns stored in SRAM cells. Our results indicate that potential perturbations in multiple p-wells play a key role in determining fail bit patterns. A novel multiple-cell upset mechanism, named multi-well coupled potential unbalancing, is proposed based on the consideration of the unbalanced activation of parasitic bipolar effects. The dominance of this mechanism is confirmed through multiple-pulse irradiation tests.

High-reflectivity electromagnetic two-axis microscanner using dielectric multi-layer reflective surface

A high-reflectivity electromagnetic two-axis microscanner is presented, which uses dielectric multi-layer coating on the aluminum film at the reflective surface. The microscanner is driven biaxially with the torque generated between the radially directed magnetic field and the current path through a single-turn copper coil patterned on the scanner. To enhance reflectivity, dielectric multi-layers of Al2O3 and TiO2 films are coated on the aluminum reflective surface of the mirror. A reflectance of 96.31% was obtained by using two pairs of dielectric films at a wavelength of 850 nm. Laser irradiation tests were performed to measure the operational reliability of the microscanner. The temporal drift of the optical scan angle for the mirror with two pairs of dielectric layers was measured to be 0.16° during a 6-h operation using a femtosecond pulsed laser irradiation with an average power of 2.3 W and a high repetition rate of 80 MHz. However, for the mirror where the reflection surface was coated with an aluminum layer only, a 1.74° degradation of the tilting angle was observed.

Laser test studies on the single-sided dual-column 3D stripixelsilicon detector

The single-sided full-3D stripixel detector and the laser test system were introduced in this paper. The detector responses to different conditions (including detector bias voltage, laser illumination position, pulse generator parameters setting for driving laser device, etc) were measured and analyzed. Main detector parameters, including the depletion voltage, 2D position sensitivity response, charge collection characteristics with different bias voltages, noise distribution characteristics influenced by the different coupling modes of n+-strips and p+-strips electrodes to the readout chip channels, were obtained with 1060nm laser irradiation tests. The measurement results showed that the detector was position sensitive. Its depletion voltage was about 5V. The measured equivalent noise charge(ENC) of the detector system was about 730±10e.

In situ calibration of the foil detector for an infrared imaging video bolometer using a carbon evaporation technique.

The InfraRed imaging Video Bolometer (IRVB) is a useful diagnostic for the multi-dimensional measurement of plasma radiation profiles. For the application of IRVB measurement to the neutron environment in fusion plasma devices such as the Large Helical Device (LHD), in situ calibration of the thermal characteristics of the foil detector is required. Laser irradiation tests of sample foils show that the reproducibility and uniformity of the carbon coating for the foil were improved using a vacuum evaporation method. Also, the principle of the in situ calibration system was justified.

Enhancement of resistance against high energy laser pulse injection with chevron beam dump

The laser beam dump of the Edge Thomson scattering (ETS) in ITER is being developed and a new type of beam dump called the chevron beam dump was proposed recently. The laser-induced damage on the surface is one of the most severe issues to be overcome. The key concept of the chevron beam dump is to reduce the laser energy absorption per unit area and to absorb the laser beam gradually. The laser irradiation tests onto flat-mirror-molybdenum sample were carried out. It was clarified that the absorbed (rather than incident) energy density of the laser pulses should be the correct figure of merit for the laser-induced damage. Therefore, the concept of the chevron beam dump design, that minimizes the absorbed laser energy density per unit area, was validated experimentally. The chevron beam dump enables us to extend its lifetime drastically relative to conventional beam dumps. Potential methods to improve the laser-induced damage threshold (LIDT) are also discussed in this paper.

A laser irradiation disc test for fracture testing of refractory fine ceramics

Abstract The critical stress intensity factor, tensile strength and crack stability were analysed for a zirconia refractory by parameter identification based on a laser irradiation test and a finite element simulation. Furthermore, the results for the specific fracture energy were determined for different assumed cohesive behaviours. The tests were carried out on notched discs that were irradiated at their centres. During the tests, temperatures are recorded by a thermo vision camera and the crack propagation by an acoustic emission recorder. Acoustic emission allowed for the determination of the onset of crack initiation (time t 1 ) and unstable crack propagation (time t 2 ). A finite element model representing the geometry of the sample was built to determine the fracture mechanical parameters from t 1 and t 2 . This method is believed to be favourable for rather brittle refractory ceramics, whereas for less brittle materials, a wedge splitting procedure according to Tschegg is considered more favourable.

Mechanical Properties and Deformation Of Ceramic Coated Steels Heat-treated By Scanning Laser

A new surface modification method “laser quenching after coating” using a high power diode laser equipped with a 2dimensional galvano-scanner unit was developed to process a larger area of ceramic coated steel uniformly and efficiently. The laser irradiation tests for 3 kinds of ceramic-coated steels: CrAlN, TiAlN and CrN, were carried out with the scanning laser, and the appropriate irradiation conditions to achieve the uniformly quenched substrate without any surface damage were clarified for these ceramic-coated steels. The area of the substrate surface wider than the laser spot size could be easily quenched by the scanning laser. The adhesive strength, the film hardness of the laser-irradiated regions and the deformation caused by laser irradiation were evaluated. Laser quenching with the scanning laser can effectively improve the adhesive strength and substrate hardness without any detrimental effect on the film hardness of the ceramic-coated specimens. In the deformation of the laserirradiated specimens, two features were recognized; one is the bending, and the other is the expansion of laser-irradiated part. It was found that the deformation of ceramic-coated steel by laser irradiation under the same heat input condition does not depend on the kind of ceramic thin film but on the steel type of the substrate. It was concluded that “laser quenching after coating” with scanning laser could easily improve the adhesive strength and substrate hardness without any detrimental effect on the film hardness of large surface areas in the tested all types of ceramic-coated specimens. Copyright © 2014 VBRI press.

Investigation of AE Features in Grinding

This paper presents recent investigation of acoustic emission (AE) behaviours in grinding processes. It demonstrated the acoustic emission features characterized in time and frequency domain are influenced by thermal behaviours of materials. By control laser conditions, the temperature elevation under laser irradiation can be similar to that in a grinding process. Therefore, an innovative concept that grinding process can be monitored by using thermal AE signatures from laser irradiation tests has been proposed. Accordingly, an artificial neural network (ANN), built on laser irradiation tests, was applied to monitor grinding thermal performance. The results showed that grinding performance variation due to wheel wear can be identified by using the ANN. This development could bring great benefits by reducing experimental works in the preparation of an ANN for grinding monitoring.

Grinding Monitoring through Thermal Acoustic Emission Signatures

This paper presents recent development in acoustic emission (AE) technique for grinding process monitoring. It demonstrated the similarity of thermal acoustic emission feature existing in grinding processes and laser irradiation tests. An innovative concept that grinding process can be monitored by using thermal AE signatures from laser irradiation tests has been proposed. Based on such idea, an artificial neural network (ANN) was built and the results showed that grinding performance variation due to wheel wear can be identified by using the ANN. This development could bring great benefits by reducing experimental works in the preparation of an ANN for grinding monitoring.

The effect of Er:YAG laser irradiation on the scanning electron microscopic structure and surface roughness of various implant surfaces: an in vitro study

The purpose of this study was to evaluate the surface roughness (R(a)) and microscopic change to irradiated dental implant surfaces in vitro and ultimately to determine the proper pulse energy power and application time for the clinical use of Er:YAG lasers. Anodic oxidized surface implants and sand-blasted, large-grit, and acid-etched (SLA) surface implants were used. Each experimental group of implant surfaces included ten implants. Nine implants were used for the laser irradiation test groups and one for the control group. Each test group was equally divided into three subgroups by irradiated pulse energy power. Using an Er:YAG laser, each subgroup of anodic oxidized surface implants was split into 60-, 100-, and 140-mJ/pulse groups, with each subgroup of SLA surface implants irradiated with a 100-, 140-, or 180-mJ/pulse. Three implants in every test subgroup were respectively irradiated for 1, 1.5, and 2 min. The R(a) values for each specimen were recorded and every specimen was observed by SEM. Irradiation by Er:YAG laser led to a decrease in implant surface roughness that was not statistically significant. In anodic oxidized surfaces, the oxidized layer peeled off of the surface, and cracks appeared on implant surfaces in the 100- and 140-mJ/pulse subgroups. However, with SLA surfaces, no significant change in surface texture could be found on any implant surface in the 100- and 140-mJ/pulse subgroups. The melting and fusion phenomena of implant surfaces were observed with all application times with 180mJ/pulse irradiation. The SLA implant surfaces are stable with laser intensities of less than 140mJ/pulse and an irradiation time of less than 2 min. The anodic oxidized surfaces were not stable with laser intensities of 100mJ/pulse when an Er:YAG laser was used to detoxify implant surfaces.

Early Diagnosis of Ocular Hypertension Using a Low-Intensity Laser Irradiation Test

We investigated the potential use of low-intensity laser irradiation (LILI) as a diagnostic tool for identifying hypertensive eyes at risk of glaucoma. The diagnosis of early-stage ocular hypertension is particularly difficult to establish. This study of a case series included 123 healthy subjects with normal vision. The intraocular pressure (IOP) was determined before (baseline) and 30 min after a 30-sec irradiation of the limbus area with laser light (780 nm; 7.5 mW; 292 Hz modulation). Baseline IOP was >21 mm Hg in 44 of 211 eyes (20.9%), consistent with ocular hypertension. LILI decreased the mean IOP by 6.2 mm Hg (-25.7%; p < 0.001; paired t test) in these eyes. The remaining 167 eyes (79.1%) exhibited a normotensive IOP <or=21 mm Hg. LILI reduced the mean IOP by 2.9 mm Hg (-17.1%; p < 0.001) in these eyes, but there were different response patterns: 1) the IOP did not change (27.0%); 2) the IOP was reduced by the same extent in both eyes (32.3%); 3) initial IOP differences between left and right eyes became level and the absolute IOP was reduced to a lower level that was identical in both eyes (18.0%); and 4) the initial difference in IOP between the left and right eye persisted despite LILI (22.7%). LILI lowers IOP, even in normotensive eyes. This effect may be useful to determine the individual physiological IOP and to diagnose latent ocular hypertension in eyes with presumably normotensive IOP.

Postfluorination of fluoride films for vacuum-ultraviolet lithography to improve their optical properties

Transmittance of fluoride films prepared by various kinds of deposition methods is not sufficient for a vacuum-ultraviolet (VUV) stepper application. Moreover, moisture penetrates into fluoride films because of porous structures. Then the moisture reacts with the fluoride chemically, and the photoabsorption of the films increases with elapsed time. Postfluorination treatment, in which F-poor areas of fluoride films are sufficiently fluorinated and the film structures are modified to be denser, has been developed. The postfluorination treatment was performed at 0.1 MPa of diluted F2 gas in a special apparatus made of nickel. This treatment reduces photoabsorption of fluoride films and prevents photoabsorption from increasing again with elapsed time. In a long-time F2 laser irradiation test, the transmittance of as-deposited fluoride films remarkably degraded with irradiation. On the other hand, there is no tendency of transmittance degradation in the case of postfluorinated fluoride films. The postfluorination is able to improve the optical performance of fluoride films, promising the highest coating level for VUV lithography.