Material Processing Applications Research Articles

Photodiode-based process monitoring for the ultrashort-pulsed laser structuring of the diffusion media for fuel cells

In recent years, the incorporation of process monitoring systems has become an integral part across several laser material processing applications. This is due to the feasibility of inline evaluations, which enable the elimination of downstream quality checks that are typically time-consuming and costly. Simultaneous to recent sensor developments, ultrashort-pulsed (USP) laser material processing has become a promising technology for creating complex microstructures in a wide variety of materials due to its high precision and negligible thermal input. So far, process monitoring has yet to be established in USP applications as it is unknown which sensors are suitable, which parameters can be observed, and which process-relevant information can be detected within the data. Within this work, a state-of-the-art photodiode-based process monitoring system was used to collect spectral data from the process zone and extract relevant information from the process. The laser structuring of the two-layered diffusion media used in polymer electrolyte membrane fuel cells was selected as the use case. This structuring process is challenging due to production-related fluctuations in the material thickness and the surface quality. Within this study, information was acquired from a sensor system employing three photodiodes. Through the application of explorative data analysis techniques and machine learning, AI models were created, focusing on determining the focus position of the laser beam and identifying the transition between the two layers. The developed models were capable of determining the initial focus position with varying accuracies. The best performance was achieved by a convolutional neural network using spectrograms as input data, while the worst accuracy was achieved by a ridge regression model using manually selected features. Furthermore, a clustering model was used, demonstrating the capability to detect the layer transitions within a specified tolerance.

On the thermal performance of a three-dimensional cross-ternary hybrid nanofluid over a wedge using a Bayesian regularization neural network approach

Abstract Significance Studying the flow of ternary nanofluids [Ag, Cu, MoS2] holds significant importance in both science and engineering. Ternary nanofluids are vital in advancing thermal management systems, heat exchangers, aerospace, and materials processing applications. Purpose This study investigates the ternary hybrid Carreau nanofluid numerically for thermal proficiency in the inclined magnetized environment. In this study, three distinct nanoparticles of [Ag, Cu, MoS2] and base fluid water over the wedge are used. The velocity of nanofluids is judged under the influence of an inclined magnetic field, and the thermal performance is scrutinized by incorporating the thermal radiation effect. Methodology The physical problem generates partial differential equations, which are transformed into ordinary differential equations (ODEs) through similarity variables. These ODEs are linearized into a system of ODEs and then passed under the bvp4c Matlab program to get the solution. This solution is again trained by an artificial neural network, and further results are obtained with both schemes and compared. Findings The most rapid heat transport analysis is found for ternary hybrid nanofluids compared to bi-hybrid nanofluids. The thermal radiation parameters and the magnetic environment augment the rate of heat transport.

Far-field sub-diffraction focusing and controlled focus shaping of circularly polarized light using a dielectric phase plate

In recent years, sub-diffraction focusing has received substantial attention due to its versatility. However, achieving a flexible sub-diffraction focusing in the far field remains stimulating. Existing techniques either require complex fabrication facilities or are limited to the short focal length and high numerical aperture (NA) of the imaging system. Here, we introduce an optimization method for sub-diffraction focusing of a circularly polarized beam in the far field with a lens of large focal length. A cost-effective dielectric phase plate serves the purpose. By employing a phase plate composed of a thin layer of dielectric Si3N4, the phase of the propagating beam is modulated in the beam’s cross-section, which is divided into two regions of the opposite phase by the plate. A sub-diffraction focusing is achieved for a proper tunning between the two regions. In addition to sub-diffraction focusing, the phase plate is also capable of shaping the focus into a doughnut-shaped and a flat-top profile in the far field. This design provides a simple solution for sub-diffraction focusing and focus shaping that will find potential applications in optical imaging, optical trapping, and material processing.

Thermohaline convection in MHD Casson fluid over an exponentially stretching sheet

Abstract This study investigates the thermohaline convection in MHD Casson fluid over an exponentially stretching sheet. This study has practical significance in industrial processes, materials processing, energy systems, and environmental applications. The governing equations describing the conservation for an electrically conducting fluid flow, thermal and concentration transports are considered based on the principles of mass, momentum, energy and concentration equations. Our first step involves transforming the governing nonlinear partial differential equations into a coupled nonlinear ordinary differential equations with the help of suitable similarity transformations. Second step, infinite domain [0, ∞) of the problem to a finite domain [0, 1] through a coordinate transformations. This specific choice is motivated by the wavelet's significance in the finite domain of [0, 1]. Third step, we effectively solve the resulting coupled nonlinear ordinary differential equations using the numerical Hermite wavelet method (HWM). This approach proves to be a valuable technique for obtaining significant results and insights in our study. Finally, the effect of known physical parameters on velocity, temperature and concentration are analysed through tables and graphs.

Vectorial manipulation of twisted vector vortex optical fields in strongly nonlocal nonlinear media

Abstract We theoretically investigate the propagation properties and vectorial manipulation of twisted vector vortex beams (TVVB) with a cross-phase in a strongly nonlocal nonlinear medium (SNNM). The root mean square beam-width (RMS-BW) and the critical power required to retain the invariant RMS-BM of the TVVB in an SNNM are derived using the coupled nonlocal nonlinear Schrödinger equation. Numerical calculations reveal novel characteristics of the evolution of the state of polarization (SoP) and the optical intensity distributions during the TVVB propagating in an SNNM. It is found that mode conversions between a Laguerre Gaussian and a Hermite Gaussian mode take place during propagation in an SNNM, and the topological charge of the TVVB can be accurately measured by observing the interference intensity structure in the cross-section. Manipulation of the beam shape, SoP, and rotation of the TVVB is achieved by controlling factors such as the initial power, twisting coefficient, initial beam-width, and topological charge. These findings hold promise for applications in optical micro-manipulation, optical communication, and material processing.

A kinetic comparison between in situ hybrid microwave and conventional magnetising roasting of low-grade iron ore composite pellet

This article aims to comprehensively summarise the essential aspects of reduction kinetics in magnetising roasting of low-grade iron ore–coal composite pellets in the hybrid microwave and conventional furnace. The influence of crucial process parameters like temperature, time, and heating methods, including traditional and hybrid microwave heating, is explored. Investigating the impact of low-grade iron ore and coal quality on reduction kinetics is conducted to identify optimal heating methods for upgrading low-grade iron ore to blast furnace grade through magnetising roasting. The study uses diverse gas–solid reaction models to assess the reduction mechanism (Fe2O3 to Fe3O4). Results indicate the success of the contracting volume model for microwave heating, while conventional heating transitions from phase-boundary chemical control to diffusion control. XRD confirms magnetite dominance post-reduction, while scanning electron microscopy analysis establishes microwave crack-assisted efficiency over conventional heating for ease of reduction. A comparative study of apparent activation energy reveals the hybrid microwave method's four-fold lower (36.71 kJ/mol) than conventional resistance heating (156.19 kJ/mol). This underscores the potential of microwave heating for enhanced reduction kinetics and low-grade iron ore material processing applications.

Finite Element Analysis of the Structure and Working Principle of Solid-State Shear Milling (S3M) Equipment.

Solid-state shear milling (S3M) equipment is an evolution from traditional stone mills, enabling the processing of polymer materials and fillers through crushing, mixing, and mechanochemical reactions at ambient temperature. Due to the complex structure of the mill-pan, empirical data alone are insufficient to give a comprehensive understanding of the physicochemical interactions during the milling process. To provide an in-depth insight of the working effect and mechanism of S3M equipment, finite element method (FEM) analysis is employed to simulate the milling dynamics, which substantiates the correlation between numerical outcomes and experimental observations. A model simplification strategy is proposed to optimize calculation time without compromising accuracy. The findings in this work demonstrate the S-S bond breakage mechanism behind stress-induced devulcanization and suggest the structural optimizations for enhancing the devulcanization and pulverization efficiency of S3M equipment, thereby providing a theoretical foundation for its application in material processing.

Design solutions and characterization of a small scale and very high concentration solar furnace using a Fresnel lens

The use of Fresnel lenses for solar energy concentration technology dates back to the 1950 s. These lenses feature a plano-convex optical design with a series of discontinuous convex grooves. Typically made from materials like polymethyl methacrylate, Fresnel lenses are lightweight, resistant to sunlight, thermally stable, and cost-effective.This study presents a novel Fresnel lens-based solar furnace configuration installed at the Eduardo Torroja Institute for Construction Science in Madrid, Spain. The novelty of this work lies in the exceptional performance and operability of the facility. Experimental characterization revealed a record peak irradiance over 7 MW m−2 for an incident target power exceeding 800 W. Comparison with ray tracing simulations shows good agreement with experimental results. This setup enables high temperature experiments up to 2000 °C with rapid execution times. A fixed receiver, a shutter system and a closed-loop heliostat tracking control system allow for flexible operation up to 5000 suns and straightforward maintenance. The concentrator element costs less than 300 USD (2022) m−2, offering an economical solution to solar-powered high concentration and temperature applications. This innovative design overcomes previous operational challenges, providing a robust and economical method for high-temperature material processing and other industrial applications.

Recent Advancements and Challenges in High‐Power Thulium‐Doped Laser

AbstractHigh‐power all‐fiber thulium lasers have gained considerable interest in recent times due to their distinct characteristics and versatile applications in the medical and industrial sectors. This review article presents a comprehensive examination of the advancements and challenges in this field. It begins with an overview of thulium‐doped silica fiber, which is a critical component for high‐power lasers operating at the 2 µm (micrometer) wavelength band. The research progress of essential high‐power thulium laser sources, including continuous‐wave (CW), quasi‐continuous wave (QCW), and pulsed lasers, is then thoroughly analyzed, highlighting their respective strengths and limitations. Additionally, the diverse applications of high‐power thulium fiber lasers in medical and industrial domains are summarized. Furthermore, the article emphasizes the current challenges in the advancement of high‐power thulium‐doped fiber lasers (TDFLs) and outlines potential avenues for future development. Despite TDFLs being the predominant laser source in lithotripsy and material processing applications, optimizing their performance and expediting further progress in thulium laser technology remain crucial objectives. This review article aims to provide valuable insights for researchers, engineers, and professionals working in the field of high‐power fiber lasers operating at 2 µm.

Ozone production by an He+O2 radio-frequency atmospheric pressure plasma jet driven by tailored voltage waveforms

Atmospheric pressure plasma jets are efficient sources of reactive oxygen and nitrogen species with potential applications in medicine, materials processing, green industry and agriculture. However, selective control over the production of reactive species presents an ongoing challenge and a barrier to the widespread uptake of these devices in applications. This study therefore investigates the production of ozone by a radio-frequency plasma jet driven with tailored voltage waveforms composed of up to five consecutive harmonics, with a fundamental frequency of 13.56 MHz. The plasma is supplied with helium with small admixtures (0.1%–1.0%) of oxygen gas. The ozone density in the far effluent is measured with Fourier transform infrared spectroscopy and the gas temperature in the plasma channel is determined with optical emission spectroscopy. Voltage waveform tailoring is found to enhance the ozone density in the far effluent of the plasma jet in comparison to operation with single-frequency voltage waveforms. Increasing the number of applied harmonics in the driving voltage waveform for a fixed peak-to-peak voltage enhances the ozone density but significantly increases the gas temperature within the plasma channel. Meanwhile, increasing the number of applied harmonics while maintaining a constant RF power deposition allows the density of ozone in the effluent to be increased by up to a factor of 4 relative to single-frequency operation, up to a maximum density of 5.7 ×1014 cm−3, without any significant change to the gas temperature. This work highlights that tailored voltage waveforms can be used to control the density of ozone delivered through the plasma effluent, marking an important step towards realising the potential of these plasmas for applications.

Sub-megahertz compact self-pulsed Raman laser

Broadband self-pulsed Raman laser operating at sub-megahertz (sub-MHz) has been widely used in optical sensing, high-spectral-resolution lidar, frequency-division multiplexing, and optical communication. However, it is a big challenge for achieving stable self-pulsed Raman laser oscillation in a wide pump power range. Here, we construct a compact Yb:YAG/YVO4 Raman laser for generating broadband self-pulsed laser operating at high repetition rate. The effects of cavity length (LC) and Raman crystal length (LR) on the performance of self-pulsed Raman laser have been investigated. By utilizing a 1.5 mm-thick YVO4 crystal as a Raman crystal, the repetition rate increases dramatically from 62 to 280 kHz when the LC decreases from 10 to 4 mm. Meanwhile, the pulse width of 0.66 μs and peak power of 1.1 W are achieved for the self-pulsed Raman laser with LC = 4 mm. For the 4 mm-long Raman laser cavity constructed with a 2 mm-thick YVO4 crystal, the pump power range enable for self-pulsed Raman laser oscillation extends from 1.8 to 3.9 W, the repetition rate has been further increased from 258 to 467 kHz. While the peak power and pulse width are 0.6 W and 0.98 μs, respectively. The Yb:YAG/YVO4 self-pulsed Raman laser oscillates in broadband multi-longitudinal-mode, the spectral bandwidth is 27.4 nm covering from 1051.1 to 1078.5 nm. Utilization of a tilted 2 mm-thick YVO4 crystal as output coupler to construct compact Yb:YAG/YVO4 self-pulsed Raman laser dramatically expands the pump power range for generating high repetition rate self-pulsed Raman laser. Sub-MHz self-pulsed Raman lasers with a wide spectral bandwidth have potential applications in materials processing, quantum information processing, and optical communications.

Catalytic Thermocuring and Synergistic Photothermocuring of Single-Component Acrylate-Grafted Liquid Oligosilazanes.

A novel thermosetting preceramic resin called acrylate-grafted liquid polysilazane (ALSZ) was readily synthesized. The curing behaviors of ALSZ were investigated by the techniques of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and rheological tests. The catalytic thermocuring process was controlled by the addition of a polymerization accelerator composed of a radical initiator (cumene hydroperoxide) and a transition metal catalyst (nickel naphthenate or cobalt naphthenate). Photocuring at room temperature can proceed readily by the addition of photosensitizer 819 (phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide). By combining a radical initiator, a transition metal catalyst, and a photosensitizer, synergistic photothermocuring was achieved, demonstrating advantages such as material shaping at room temperature and low weight loss during curing. The ceramization of the solidified ceramic precursors in an Ar atmosphere was studied using TGA and tube furnace pyrolysis. ALSZs exhibited comparatively high ceramic transformation yields (71-75% at 800 °C). The resulting pyrolytic ceramics maintained their original shape without deformation or foaming expansion. Polysilazanes containing acrylate groups can directly form casting bodies, showing a high static glass transition temperature (>380 °C) by thermomechanical analysis (TMA). FT-IR analyses revealed that multiple reactions are involved in the curing of ALSZ. The results in this paper showed that ALSZ might find prospective applications in material processing, such as additive manufacturing and ceramic-matrix composites.

Enhancing machining accuracy of banana fiber-reinforced composites with ensemble machine learning

Through innovative predictive modeling, this study advances Abrasive Water Jet Machining (AWJM) for banana fiber-reinforced biocomposites. Utilizing Artificial Neural Network (ANN) and Long Short-Term Memory (LSTM) models, hyperparameters are meticulously tuned for predicting Surface Roughness (Ra), Material Removal Rate (MRR), and Kerf Angle (Ka). Optimal configurations are identified, such as 3–6-6–4-1, 3–5-5–4-1, and 3–5–4–4-1 for ANN models, and 250, 100, and 50 units for LSTM models. Beyond individual models, the study explores stacking ensemble models, merging ANN and LSTM strengths with a Linear Regression final estimator, showcasing robust performance validated with high R-squared values. Regression models from Design Expert 13 contribute to understanding process parameter-outcome relationships. Optimized input parameters offer insights into minimizing surface roughness and kerf angle while maximizing MRR. This holistic approach, integrating advanced machine learning and ensemble learning, enhances predictive accuracy for banana-reinforced biocomposites, providing a versatile framework for diverse materials processing applications.

Consequences of Thermal Diffusion and Chemical Reaction on Mixed Convection MHD Casson Fluid through Porous Media with Inclined Plates

In this present article, we analyzed the effects of Thermal diffusion and chemical reaction on nonlinear mixed convection MHD flow of viscous, incompressible and electrically conducting fluid past an inclined porous channel under the influence of thermal radiation and chemical reaction. The transformed conservation equations are solved analytically subject to physically appropriate boundary conditions by using two term perturbation technique. The numerical values of fluid velocity, fluid temperature and species concentration are displayed graphically whereas those of skin friction coefficient, rate of heat transfer and rate of mass transfer at the plate are presented in tabular form for various values of pertinent flow parameters. It is observed that the velocity is decreased with increasing magnetic field parameter. The resultant velocity and concentration has enhances with increasing thermal diffusion parameters. The study is relevant to chemical materials processing applications.

Thermal energy transport in stratified 2D-Casson fluid flow over an inclined exponentially stretching surface with Soret/Dufour effects: Numerical simulations and applications in energy harvesting

Significance: The thermal energy transfer in nanofluid flow over an exponentially stretching surface has crucial practical configurations in various industrial processes, and it has potential applications in heat exchangers, chemical engineering, energy harvesting, and material processing. Purpose: This study is devoted to exploring the features of free convection in the thermally stratified, unsteady flow of Casson fluid over an inclined, exponentially stretching surface. Moreover, the implications of nonlinear thermal radiation, activation energy, and thermal/salute stratification effects are examined over the thermal energy transport distributions. Diffusion-thermo and thermo diffusion impressions are also taken into consideration. Methodology: By introducing reasonable transformations, partial differential equations are altered into ordinary differential equations. A nonlinear system of differential equations is solved numerically by employing the Midrich numerical technique. Findings: The impacts of diverse fluid parameters like the Soret/Dufour number, temperature difference parameter, radiation parameter, thermal/salute stratification parameter, magnetic parameter, and Prandtal number are assessed and depicted in plots by explaining the physical justifications of each parameter. Also, numerical values of sink friction and local Nusselt and Sherwood numbers are computed and examined for different values of pertinent variables involved in the problems. It is found that the rate of thermal energy transport is significantly enhanced by the larger estimation of the radiation parameter. Furthermore, it is perceived that the escalation in the temperature ratio constant leads to increased thermal convection in the fluid, while the larger thermal stratification constant decays the rate of heat transport in the fluid. Additionally, the rate of thermal transport is de-escalated due to the escalation in the intensity of thermal stratification parameter.

Creating spatial doughnut-spot arrays and double-helix focal fields with prescribed characteristics

Spatially controllable focal fields play a pivotal role in light manipulation and provide significant opportunities for precisely manipulating light–matter interactions in a wide range of applications. In particular, the double-helix focal field—characterized by a distinctive helical structure—exhibits exceptional optical properties, thus differentiating it apart from conventional focal fields. However, the rapid construction of a double-helix focal field with controllable characteristics and a uniform intensity remains a challenging task. Based on the theory of pattern synthesis of an antenna array, we propose and realize the generation of three-dimensional doughnut-spot arrays and double-helix focal fields with specified characteristics in a 4π system by reverse-solving the radiation field of the virtual antenna. Numerical examples indicate that the desired novel focal fields, including features such as shape, orientation, length, and period, could be rapidly, conveniently, and flexibly customized by selecting appropriate parameters for the magnetic dipole array antennas. This method could reveal an avenue for enhanced light manipulation for applications in materials processing, optical lithography, and optical communications.

Elimination of Low-Angle Grain Boundary Networks in FeCrAl Alloys with the Electron Wind Force at a Low Temperature

Low-angle grain boundaries (LAGBs) accommodate residual stress through the rearrangement and accumulation of dislocations during cold rolling. This study presents an electron wind force-based annealing approach to recover cold-rolling induced residual stress in FeCrAl alloy below 100 °C in 1 min. This is significantly lower than conventional thermal annealing, which typically requires temperatures around 750 °C for about 1.5 h. A key feature of our approach is the athermal electron wind force effect, which promotes dislocation movement and stress relief at significantly lower temperatures. The electron backscattered diffraction (EBSD) analysis reveals that the concentration of low-angle grain boundaries (LAGBs) is reduced from 82.4% in the cold-rolled state to a mere 47.5% following electropulsing. This level of defect recovery even surpasses the pristine material’s initial state, which exhibited 54.8% LAGBs. This reduction in LAGB concentration was complemented by kernel average misorientation (KAM) maps and X-ray diffraction (XRD) Full Width at Half Maximum (FWHM) measurements, which further validated the microstructural enhancements. Nanoindentation tests revealed a slight increase in hardness despite the reduction in dislocation density, suggesting a balance between grain boundary refinement and dislocation dynamics. This proposed low-temperature technique, driven by athermal electron wind forces, presents a promising avenue for residual stress mitigation while minimizing undesirable thermal effects, paving the way for advancements in various material processing applications.

Impact of Moving Walls and Entropy Generation on Doubly Diffusive Mixed Convection of Casson Fluid in Two-Sided Driven Enclosure.

In this study, numerical simulations are conducted with the goal of exploring the impact of the direction of the moving wall, solute and thermal transport, and entropy production on doubly diffusive convection in a chamber occupied by a Casson liquid. Wall movement has a significant impact on convective flow, which, in turn, affects the rate of mass and heat transfer; this sparked our interest in conducting further analysis. The left and right (upright) walls are preserved with constant (but different) thermal and solutal distributions, while the horizontal boundaries are impermeable to mass transfer and insulated from heat transfer. Numerical solutions are acquired using the control volume technique. Outcomes under a variety of Casson fluid parameters, including Ri, Gr, buoyancy ratio, and direction of the moving wall(s), are explored, and the influences of entropy generation are comprehensively investigated. While the flow field consists of a single cell in case I, it is dual-cellular in case III for all values of the considered parameters. Comparing the three cases, the average heat and mass transport presented lower values in case III due to the movement of an isothermal (left) wall against the buoyant force, while these values are enhanced in case I. The obtained results are expected to be useful in thermal engineering, material, food, and chemical processing applications.

Efficient Pulsed Raman Laser with Wavelength above 2.1 μm Pumped by Noise‐Like Pulse

Herein, the efficiently high‐power pulsed Raman lasers with wavelength above 2.1 μm are experimentally demonstrated relying on the stimulated Raman scattering. A tailored high‐power noise‐like pulse (NLP) fiber laser system centered at ≈1953 nm with a maximum output power of ≈10.9 W is served as the pump source. By directly pumping a section of highly Ge‐doped silica fiber, the first pulsed Raman laser (centered at≈2139 nm) and the second pulsed Raman laser (centered at ≈2353 nm) with maximum output powers of ≈3.8 and ≈0.25 W are obtained, respectively, which represent the highest output powers of NLP at these wavelength regions, to the best of knowledge. Moreover, a high spectral purity of ≈94.3% of the first Raman laser is obtained, which indicates the significantly potential application of NLP in pulsed Raman laser. The midinfrared NLP fiber laser source will have potential applications in transparent polymer materials processing and midinfrared spectroscopy.

Direct generation of multicolor Bessel beams from a Pr3+: WPFG fiber laser.

Multicolor visible high-order Bessel (Bessel-vortex) beams which have a helical wavefront and a long confocal length have garnered significant interest for applications in materials processing and biomedical technologies. In this paper, we demonstrate the direct generation of multicolor (523, 605 and 637 nm) Bessel-vortex beams from a Pr3+-doped water-proof fluoro-aluminate glass (Pr3+: WPFG) fiber laser with an intracavity lens which induces chromatic and spherical aberration. The handedness of the generated Bessel-vortex beam is selectively controlled through lateral displacement of the intra-cavity lens.