Angle Laser Research Articles

Effect of laser beam incident angle on welding of Ti6Al4V with fiber lasers

Laser beam welding (LBW) is widely used for welding Ti6Al4V alloys in aerospace applications. LBW has localized high-energy fluence with low-energy input compared to other fusion welding processes, resulting in narrower heat-affected zones. On the other hand, most metals are highly reflective when the laser beam impinges perpendicular to the surface, making the process inefficient. Hence, this work proposes to employ shallow angle incidence to reduce the reflectivity during the welding of Ti6Al4V material. To explore the potential of this idea, the current study focuses on studying the effect of laser incident angle (15°-90°), power (300 W-1500 W), and feed rate (10 mm/s-25 mm/s) on autogenous weld bead geometry. For this purpose, bead-on plate (BOP) LBW is conducted on mill-annealed Ti6Al4V material of dimensions 25 mm × 25 mm × 3 mm by employing a fiber laser source with a maximum power of 3 kW and a wavelength of 1080 nm. It is observed from the results that at a normal incident angle and low laser power (< 600 W), the penetration depth is too low to generate a weld bead. Analyzing the cross-section of the weld bead, obtained from SEM, perpendicular to the weld direction reveals that the increase in laser incident angle up to an optimal angle resulted in increased bead dimensions (width and height), and beyond that, the dimensions decreased. However, the optimal incident angle changed when the laser power was changed. The major finding of this study is that at 600 W and a normal incident angle, the laser could not penetrate and generate a weld bead due to low absorptivity, while at an incident angle of 300, 450, and 600, weld beads are generated because of increased absorptivity. Similarly, the increase in weld dimensions with the increase in laser power is observed. At higher laser power, underfill and oxide formation are observed. The feed rate is less predominant than the incident angle and the power.

Impact of Surface Pretreatment on the Corrosion Resistance and Adhesion of Thin Film Coating on SS316L Bipolar Plates for Proton-Exchange Membrane Fuel Cell Applications.

Coated SS316L is a potential alternative to the graphite bipolar plates (BPPs) used in proton-exchange membrane fuel cells (PEMFCs) owing to their low manufacturing cost and machinability. Due to their susceptibility to corrosion and passivation, which increases PEMFC ohmic resistance, protective and conductive coatings on SS316L have been developed. However, coating adhesion is one of the challenges in the harsh acidic environment of PEMFCs, affecting the performance and durability of BPPs. This study compares mechanical polishing and the frequently adopted chemical etchants for SS316L: Adler's, V2A, and Carpenter's etchant with different etching durations and their impact on the wettability, adhesion, and corrosion resistance of a Nb-coated SS316L substrate. Contact angle measurements and laser microscopy revealed that all etching treatments increased the hydrophobicity and surface roughness of SS316L substrates. Ex situ potentiodynamic and potentiostatic polarization tests and interfacial contact resistance analysis revealed high corrosion resistance, interfacial conductivity, and adhesion of the Nb-coated SS316L substrate pretreated with V2A (7 min) and Adler's (3 min) etchant. Increased hydrophobicity (contact angle = 101°) and surface roughness (Ra = 74 nm) achieved using V2A etchant led to the lowest corrosion rate (3.3 µA.cm-2) and interfacial resistance (15.4 mΩ.cm2). This study established pretreatment with V2A etchant (a solution of HNO3, HCl, and DI water (1:9:23 mole ratio)) as a promising approach for improving the longevity, electrochemical stability, and efficiency of the coated SS316L BPPs for PEMFC application.

Studies on electron acceleration from modulated surface at grazing angle laser interaction

Surface plasmon (SP) based electron acceleration has been investigated during the interaction of short, ultra-intense (I > 1019 W/cm2) laser pulse with periodically modulated solid target. Laser contrast conditions are required to preserve the structural integrity of the target. Two dimensional (2D) particle-in-cell (PIC) simulations report emission of energetic (~ 78 MeV) electron bunches along grating surface for grazing incident of laser pulse at an optimum angle 4° with respect to target surface. The energy and flux of emitted electrons for grazing laser incidence were found to be strongly enhanced as compared to the incident angles satisfying the resonant condition for surface plasma wave’s excitation.

Root surface roughness evaluation following application of different periodontal instruments and Er:YAG laser: A profilometry and SEM study.

The aim of the present study was to evaluate the efficacy of 30°-angled Er:YAG laser tip and different periodontal instruments on root surface roughness and morphology in vitro. Eighteen bovine teeth root without carious lesion were decoronated from the cementoenamel junction and seperated longitidunally. A total of 36 obtained blocks were mounted in resin blocks and polished with silicon carbide papers under water irrigation. These blocks were randomly assigned into 3 treatment groups. In Group 1,30°-angled Er:YAG laser (2.94μm) tip was applied onto the blocks with a 20Hz, 120mJ energy output under water irrigation for 20s. In Groups 2 and 3, the same treatment was applied to the blocks with new generation ultrasonic tip and conventional curette apico-coronally for 20s with a sweeping motion. Surface roughness and morphology were evaluated before and after instrumentation with a profilometer and SEM, respectively. After instrumentation, profilometric analysis revealed significantly higher roughness values compared to baseline in all treatment groups(p < 0.05). Laser group revealed the roughest surface morphology followed by conventional curette and new generation ultrasonic tip treatment groups (p < 0.05). In SEM analysis, irregular surfaces and crater defects were seen more frequently in the laser group. Results of the study showed that the use of new generation ultrasonic tip was associated with smoother surface morphology compared to 30°-angled Er-YAG laser tip and conventional curette. Further in vitro and in vivo studies with an increased sample size are necessary to support the present study findings.

Experimental Demonstration of an Angle Laser Sensor Based on an Optical Thinned Microfiber Mach-Zehnder Interferometer

Experimental Demonstration of an Angle Laser Sensor Based on an Optical Thinned Microfiber Mach-Zehnder Interferometer

Polarization effects on Laser-Inscribed angled Micro-Structures

The polarization of the laser beam exhibits more substantial differences in laser micromachining as the angle of incidence deviates from zero. In the reported work, our focus was to explore the effects of circularly, p- and s-polarized laser on angled ultrashort pulse laser micromachining of micropillar arrays. The examination encompassed laser process factors, including angles of incidence, microstructure dimensions, and inter-pillar spacing. A comparison between the resulting structures demonstrated that p-polarized laser beam was the most efficient in material removal in angled laser micromachining, followed by circularly polarized laser. While the s-polarized beam exhibited the lowest ablation efficiency among the three. Such distinction is mainly attributed to the distinguishing reflectivity of the three states of polarization on tilted planes. The development of structural heights during ablation processes was examined, and potential defects in laser processing methodologies were interpreted. The dependency of structural heights on inter-pillar spacing was analyzed. This study bridges the gap between existing studies on angled ultrashort pulse laser machining and the influences of polarization on laser machining. The comparison between structures produced using laboratory-scale and industrial-scale laser systems also yielded pertinent recommendations for facilitating a smooth transition of angled laser micromachining from laboratory-scale research to industrial applications.

Preparation of epoxy resin elastic particles and their application in oil well cement

AbstractTo solve the problem of high brittleness and easy cracking of cement stone, epoxy resin powder elastic particles (HEEP) were developed to improve the elasticity of cement stone. HEEP was prepared from epoxy resin and trimeric anhydride by solution polymerization. The surface wettability and particle size of HEEP were analyzed by contact angle test and laser particle size analysis respectively. Mechanical performance tests, scanning electron microscope (SEM) analysis and x‐ray diffraction analysis were conducted on the cement stone containing HEEP. The results showed that HEEP was the target product, with a hydrophilic surface and a water contact angle of 75.2° on the HEEP surface. The particle size distribution of HEEP was uniform, and the median particle size was 36.5 μm. The initial decomposition temperature of HEEP was 300°C, indicating a good thermal stability. The stress–strain curve showed that when the HEEP dosage was 3%, 6%, and 9%, the elastic modulus of the cement stone was 6.382, 4.017, and 3.148 GPa, respectively. Compared with the blank cement without HEEP, the elastic modulus was reduced by 28.3%, 54.9%, and 64.6%, respectively. This showed that HEEP could effectively improve the elasticity of cement stone. In addition, the compressive strength and flexural strength of cement stone containing HEEP can meet the requirements of on‐site applications. SEM analysis of cement stone showed that HEEP was well filled in cement stone. When the cement stone was subjected to complex stress, HEEP could effectively buffer and disperse the stress, thereby enhancing the resistance of cement stone to external force impact.

Glycoside hydrolase family 32 enzymes from Bombella spp. catalyze the formation of high-molecular weight fructans from sucrose

Abstract Aims Acetic acid bacteria of the genus Bombella have not been reported to produce exopolysaccharides (EPS). In this study, the formation of fructans by B. apis TMW 2.1884 and B. mellum TMW 2.1889 was investigated. Methods and Results Out of eight strains from four different Bombella species, only B. apis TMW 2.1884 and B. mellum TMW 2.1889 showed EPS formation with 50 g l−1 sucrose as substrate. Both EPS were identified as high-molecular weight (HMW) polymers (106–107 Da) by asymmetric flow field-flow fractionation coupled to multi angle laser light scattering and UV detecors (AF4-MALLS/UV) and high performance size exclusion chromatography coupled to MALLS and refractive index detectors (HPSEC-MALLS/RI) analyses. Monosaccharide analysis via trifluoroacetic acid hydrolysis showed that both EPS are fructans. Determination of glycosidic linkages by methylation analysis revealed mainly 2,6-linked fructofuranose (Fruf) units with additional 2,1-linked Fruf units (10%) and 2,1,6-Fruf branched units (7%). No glycoside hydrolase (GH) 68 family genes that are typically associated with the formation of HMW fructans in bacteria could be identified in the genomes. Through heterologous expression in Escherichia coli Top10, an enzyme of the GH32 family could be assigned to the catalysis of fructan formation. The identified fructosyltransferases could be clearly differentiated phylogenetically and structurally from other previously described bacterial fructosyltransferases. Conclusions The formation of HMW fructans by individual strains of the genus Bombella is catalyzed by enzymes of the GH32 family. Analysis of the fructans revealed an atypical structure consisting of 2,6-linked Fruf units as well as 2,1-linked Fruf units and 2,1,6-Fruf units.

Preparation of chitosan/citral forward osmosis membrane via Schiff base reaction with enhanced anti-bacterial properties

In this study, hydrogels generated by the Schiff base reaction between citral and chitosan (CS) were used for the first time to improve the anti-bacterial property of forward osmosis (FO) membranes. The composite membranes were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR), Water contact angle (WCA), Zeta potential and confocal laser scanning microscopic (CLSM). In the FO filtration experiment, the membrane performance of TFC-1 with 1 M sodium chloride solution as the draw solution and deionized water as the feed solution was the best, with the water flux of 25.54 ± 0.7 L m−2 h−1 and the reverse salt flux of 4.7 ± 0.4 g m−2 h−1. Although the hydrogel coating produced a certain hydraulic resistance, the flux of the modified membrane was only reduced by about 8%, compared with the unmodified membrane. However, the anti-bacterial property (Pseudomonas aeruginosa) and anti-fouling properties (bovine serum protein and lysozyme protein) of the modified membranes were improved, showing good antibacterial properties (99%) and flux recovery rate (over 90%). The modified method has the advantages of easy access to raw materials, simple operation and no risk of secondary pollution, which can effectively reduce the cost of chemical cleaning and extend the service life of the membrane. The modification of membrane by chitosan-based hydrogel is a promising option in the field of membrane anti-bacteria.

GaN Magic Angle Laser in a Merged Moiré Photonic Crystal

GaN Magic Angle Laser in a Merged Moiré Photonic Crystal

88×nm High-Efficiency Narrow Divergence Angle Laser Diodes With Coupled Waveguide Photonic Crystal

88x nm laser diodes with coupled waveguide photonic band crystal (CPBC) are designed and fabricated. By optimizing the optical confinement factor in the lightly doped coupled waveguide, the internal loss reduces to 0.52 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> . The CPBC lasers achieve maximum power conversion efficiency of 65.57% under a continuous wave (CW) mode condition at room temperature, which is the highest reported value to our knowledge at 88x nm. The corresponding vertical divergence angel is 19.8°.

Rethinking Prophylactic Laser Peripheral Iridotomy in Primary Angle-Closure Suspects: A Review

To examine the generalizability, discuss limitations, and critically appraise recommendations on the management of primary angle-closure suspects (PACSs) that emerged as a result of recent randomized clinical trials challenging the widely accepted clinical practice of offering laser peripheral iridotomy (LPI) to PACS patients. To synthetize findings from these and other studies. Narrative review. Patients classified as PACS. The Zhongshan Angle-Closure Prevention (ZAP)-Trial and the Singapore Asymptomatic Narrow Angle Laser Iridotomy Study (ANA-LIS) along with accompanying publications were reviewed. Epidemiologic studies reporting on the prevalence of primary angle-closure glaucoma and other precursor forms of the disease were also analyzed along with publications reporting on the natural course of the disease or studies reporting on outcomes after prophylactic LPI. Incidence of progression to more severe forms of angle closure. Patients recruited in recent randomized clinical trials are asymptomatic, do not have cataracts, may be younger, and have, on average, deeper anterior chambers depth compared with patients treated with LPI in clinics. The ZAP-Trial and ANA-LIS clearly represent the best available data on PACS management, additional parameters however may need to be considered when physicians face patients in clinic. PACS patients encountered at tertiary referral centers may represent more advanced cases with respect to ocular biometric parameters and may be at higher risk for disease progression compared with those recruited through population-based screening. Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Ultra-wideband, polarization-insensitive flexible metamaterial absorber base on laser printed graphene using equivalent circuit design method

In this paper, an ultra-wideband, angle and polarization-insensitive laser assisted graphene metamaterial absorber is presented. The design consists of double graphene resistive layers with the combination of three dielectric substrates. The graphene imbedded nano-magnetic material Fe3O4 has been synthesisedby laser direct writing technology, which demonstrates a high degree of uniformity with deviations less than 6% for different designed values of sheet resistance. Numerical simulation and analytical studies were carried out in order to analyze the absorption mechanism. The measured results confirm that the absorber operates from 1.32 to 17.9 GHz with over 90% absorptivity. The absorber achieves 173% fractional absorption bandwidth with a thickness of 0.068λL.

Modeling spatial variations in co-axial melt pool monitoring signals in laser powder bed fusion

The transition of additive manufacturing from rapid prototyping to large-scale manufacturing is being impeded by the limited repeatability of part quality within and across independent builds. The property variations are a result of process fluctuations, which can be random or systemic, like the location of the part on the build plate. In-situ sensors are employed to measure these process variations to monitor and control the part properties. A priori estimates of the systemic variations in the in-situ signals can enhance the efficiency of such techniques. In this work, custom builds for IN718, along with multiphysics simulations, are employed to probe systemic trends in the signals from the co-axial melt pool monitoring system on laser powder bed fusion based GE Concept Laser M2. Significant spatial variations are observed in the in-situ melt pool area, and intensity signals, and the subsequent analysis suggests that the interplay of the angled laser beam and the shield gas flow is likely a major source of the spatial trends. Machine learning is employed to develop data-driven surrogate models that make accurate predictions for this systemic variation in the melt pool area and intensity, generalizing across independent builds with significantly diverse print parameters. These models are anticipated to inform control algorithms and tune optimal print parameters with the objective of enhancing the repeatability of the part quality for laser powder bed fusion.

Fragmentation and release of pristine and functionalized carbon nanotubes from epoxy-nanocomposites during accelerated weathering.

There is an increasing volume of nano-enabled materials in the market. Once composites containing nano-additives are disposed of, weathering could deteriorate their structures, releasing nanoparticles and risking exposure of humans and aquatic organisms. Composite degradation due to environmental aging continues, including structural deterioration resulting in cracking, fragmentation, and release of microplastics and nano-additives to the environment. This research aims to study the degradation and release of initially embedded nanomaterials (NMs) from composites and their toxicity. The molecular interaction of carbon nanotube (CNT)/polymer composites is critical for modifying the polymer properties. This study investigated the interactions of functional multiwalled carbon nanotube (MWCNT) composites which affect their release during accelerated weathering processes. Different epoxy-MWCNT composites were prepared by filling a polymer with pure MWCNTs and MWCNTs functionalized with acid () and amine () groups. The physical and chemical changes of aged composites were characterized by gravimetric analysis, contact angle measurements, FTIR, SEM, and laser confocal microscopy. A loss of hydrophobicity was observed for composite surfaces long before surface cracks materialized. Released polymer fragments and nanoparticles were analyzed in wash water using TEM, FTIR and Raman spectroscopy. The environmental risks for long-term use of CNT-polymer composites and the influence of fillers on the extent of chemical photodegradation depended on the combination of polymer and fillers. If nanoparticles are released from the matrix, the high surface-to-volume ratio and reactivity of NMs make them highly dynamic in environmental systems. Exposure to these released NMs could negatively affect human health and the environment. This study provides fragmentation and CNT particle release data that could describe how molecular-level interactions between functionalized CNTs and epoxy polymers affect the aging and release of CNTs. A toxicity assessment based on a reactive oxygen species (ROS) formation assay and MTS assay for cell viability and activity of the released polymer and CNT fragments and leachate showed moderate levels of cytotoxicity of released materials as compared to pristine epoxy plates.

APPLICATION OF MATHEMATICAL MODELING AND PHYSICO-CHEMICAL ANALYSIS METHODS IN THE PREDICTION OF BIOLOGICAL ACTIVITY AND QUALITY CONTROL OF GOSSYPOL DERIVATIVES

Objective: The purpose of this work was to evaluate in silico biological activity profiles of real and virtual molecular structures of gossypol derivatives and to develop methods of Physico-chemical analysis to control their quality. Methods: Substance of gossypol-acetic acid (GAA) and 14 virtual derivatives; PASS and ChemicDescript QSAR methods; low angle and dynamic laser light scattering (LALLS, DLS) methods; IR Spectroscopy–Cary 630 Fourier Transform IR Spectrometer, UV spectrometry–Cary-60 spectrophotometer, Optical microscopy (Altami BIO 2 microscope); Spirotox method for a sample’s biological activity. Results: A distance-based topological Balaban index (J) was successfully selected by ChemicDescript analysis; the Pa meaning by PASS Online program showed maximum (from 0.8 to 0.9) variations of antitumor and antiandrogenic and minimum of antiviral activities of GAA derivatives (Pa&lt;0.5) despite the existing literature data. Microscopy and DLS methods demonstrated the values of high powder dispersion d=0.8 nm and weak stability of colloidal particles =-0.9 mV. According to UV data =42.4±0.8 (100 ml·g-1·cm-1) at λmax=380 nm. The LALLS method determined the GAA dissolution rate constant in ethanol: k=0.041±0.004 s-1. The calculated activation energy values of cell biosensor death process in 1 mmol solution of GAA in N,N-DMF: °bsEa=174.36±0.45 kJ·mol-1 in comparison with the solvent medium: °bsEa=213±1.55 kJ·mol-1 Conclusion: The developed approach of chemometric, laser and biotesting methods can be used for the identification of biologically active properties, as well as for qualitative analysis within the development of the standard for the pharmaceutical substance of natural polyphenols.

Promoted liquid-liquid phase separation of PEO/PS blends with very low LiTFSI fraction

Studies on phase behavior of polymer blends with lithium salts can provide a theoretical basis for developing solid polymer electrolytes in lithium-ion battery. In this paper, the liquid-liquid phase separation of PEO/PS/LiTFSI system is characterized by small angle neutron scattering (SANS) and small angle laser light scattering (SALLS). A combination of the Debye-Bueche equation and Ornstein-Zernike scattering function is employed to fit the SANS data in the homogeneous state. The thermodynamic parameters, including the forward scattering intensity I0, correlation length ξ, spinodal temperature Ts, effective interaction parameter χeff and cloud point boundaries, are obtained. The cloud point temperatures increase with LiTFSI concentration, especially at the low PEO fractions. We conclude that even a small amount of lithium salt enhances the liquid-liquid phase separation of PEO/PS blends significantly, and the effect of electrostatic interaction increases with temperature.

PENENTUAN JARAK OBJEK PENGHALANG MENGGUNAKAN METODE PERHITUNGAN JARAK PIKSEL DARI HISTOGRAM PROYEKSI BERPANDUAN LASER GARIS

The rapid advancement of digital image processing technology is expected to facilitate human life in various aspects of life. This study aims to detect and determine the distance of a barrier object based on the detection of lines emitted by a line laser light beam using the Matlab programming language with the pixel distance calculation method. The pixel distance calculation method is used to detect lines in an image that is processed by looking at the consistency of the laser lines. This study uses a box as an object to determine the presence of obstructions from an image captured by a camera. In this study, the parameters of distance, camera angle, and line laser angle are used. Research data collection was carried out in the afternoon in a closed room with a light intensity of 10 lux. An object can be said to be a barrier if in an image there is a laser line that is broken or not at the same pixel position. However, if in an image there are consistent lines or no line changes, then the image can be said to have no barriers. Based on the evaluation of the distance accuracy calculation with data collection, it can actually be concluded that the distance accuracy when taking data is above 85%.

Critical Quality Control Methods for a Novel Anticoagulant Candidate LFG-Na by HPSEC-MALLS-RID and Bioactivity Assays.

A low molecular weight fucosylated glycosaminoglycan sodium (LFG-Na) is a novel anticoagulant candidate from the sea cucumber Holothuria fuscopunctata that selectively inhibits intrinsic tenase (iXase). The molecular weight, molecular weight distribution and bioactivities are the critical quality attributes of LFG-Na. The determination of these quality attributes of such an oligosaccharides mixture drug is challenging but critical for the quality control process to ensure its safety and efficacy in clinical use. Herein, the molecular weight and molecular weight distribution of LFG-Na were successfully determined using high performance size exclusion chromatography coupled with multi angle laser light scattering and refractive index detector (HPSEC-MALLS-RID). Comparing to the conventional method, HPSEC-MALLS-RID based on the refractive index increment (dn/dc) did not require the reference substances to establish the calibration curve. The acceptance criteria of LFG-Na were established, the weight-average molecular weight () should be 4000 to 6000 Da, the polydispersity (/) < 1.40, and the fraction with molecular weights of 1500 to 8000 Da should be no less than 80% of the total. HPSEC-MALLS-RID was also utilized for the determination of the starting material native fucosylated glycosaminoglycan (NFG) to choose a better manufacturing process. Furthermore, APTT assay was selected and the potency of anti-iXase, referring to the parallel line assay (PLA) method, was established to clarify the consistency of its biological activities. The results suggest that HPSEC-MALLS-RID and bioactivity assays are critical quality control methods for multi-component glycosaminoglycan LFG-Na. The methods also provide a feasible strategy to control the quality of other polysaccharide medicines.

Wettability and Surface Roughness of Parylene C on Three-Dimensional-Printed Photopolymers.

The use of poly-(para-chloro-xylylene) (Parylene C) in microelectromechanical systems and medical devices has increased rapidly. However, little research has been conducted on the wettability and surface roughness of Parylene C after being soaked in solutions. In this study, the contact angle and surface roughness (arithmetic average of roughness) of Parylene C on three-dimensional (3D)-printed photopolymer in 10% sodium hydroxide, 10% ammonium hydroxide, and 100% phosphate-buffered saline (PBS) solutions were investigated using a commercial contact angle measurement system and laser confocal microscope, respectively. The collected data indicated that 10% ammonium hydroxide had no major effect on the contact angle of Parylene C on a substrate, with a Shore A hardness of 50. However, 10% sodium hydroxide, 10% ammonium hydroxide, and 100% PBS considerably affected the contact angle of Parylene C on a substrate with a Shore A hardness of 85. Substrates with Parylene C coating exhibited lower surface roughness than uncoated substrates. The substrates coated with Parylene C that were soaked in 10% ammonium hydroxide exhibited high surface roughness. The aforementioned results indicate that 3D-printed photopolymers coated with Parylene C can offer potential benefits when used in biocompatible devices.