Laser Processing Parameters Research Articles

Prediction of Femtosecond Laser Etching Parameters Based on a Backpropagation Neural Network with Grey Wolf Optimization Algorithm.

Investigating the optimal laser processing parameters for industrial purposes can be time-consuming. Moreover, an exact analytic model for this purpose has not yet been developed due to the complex mechanisms of laser processing. The main goal of this study was the development of a backpropagation neural network (BPNN) with a grey wolf optimization (GWO) algorithm for the quick and accurate prediction of multi-input laser etching parameters (energy, scanning velocity, and number of exposures) and multioutput surface characteristics (depth and width), as well as to assist engineers by reducing the time and energy require for the optimization process. The Keras application programming interface (API) Python library was used to develop a GWO-BPNN model for predictions of laser etching parameters. The experimental data were obtained by adopting a 30 W laser source. The GWO-BPNN model was trained and validated on experimental data including the laser processing parameters and the etching characterization results. The R2 score, mean absolute error (MAE), and mean squared error (MSE) were examined to evaluate the prediction precision of the model. The results showed that the GWO-BPNN model exhibited excellent accuracy in predicting all properties, with an R2 value higher than 0.90.

Machining of Ox-Ox (Al2O3/Al2O3) ceramics matrix composites by ultrafast laser

High-performance Ox-Ox ceramics material composites (CMC) are a strategic building block in the aerospace industry and high-temperature applications. The ceramics material composites are hard to machine due to high hardness, fracture toughness, and heterogeneous structures. Furthermore, it is prone to brittle fracture during the machining process. In this study, we successfully demonstrate ultrafast laser machining technology to machine Ox-Ox CMCs. A picosecond laser has been used to machine slots to understand the impact of laser process parameters on the material removal mechanism by performing deep machining. Different scan rates and a number of over-scans have been employed to understand the material removal mechanism, which is dominated by laser ablation and aided by melting due to the residual surface temperature. The maximum material removal rate of 21.75 mm3/min has been achieved for the scan rate of 300 mm/s. This can be related to the reduction in the ablation threshold and the critical balance between the material removal mechanism by ablation and melting. It was found that, the surface roughness of the cut surface has decreased due to melting and solidification. The cross-sectional examination reveals two distinct surface structures, which are entirely resolidified and thermally eroded regions.

Finite element simulation and experimental validation of thermal damage to isolated porcine skin tissue by femtosecond laser welding.

The welding effect of the laser on skin tissue is reduced by thermal damage to skin tissue, and greater thermal damage to skin tissue caused by the laser is prevented by predicting thermal damage. In this paper, a finite element model is established for the temperature field of skin tissue scanned by a femtosecond laser to obtain the influence of laser process parameters and scanning path on the thermal damage parameters of skin tissue and the thermal damage area, and verified experimentally. The results show that the established finite element model is accurate and can accurately reflect the temperature distribution during the process of femtosecond laser welding of porcine skin tissues; used to predict the thermal damage parameters of the skin tissues and the thermal damage area; and provide guidance for the study of the femtosecond laser welding of the skin tissues process to obtain the optimal process parameters.

Predictive modelling of laser powder bed fusion of Fe-based nanocrystalline alloys based on experimental data using multiple linear regression analysis

This study harnessed bivariate correlational analysis, multiple linear regression analysis and tree-based regression analysis to examine the relationship between laser process parameters and the final material properties (bulk density, saturation magnetization (Ms), and coercivity (Hc)) of Fe-based nano-crystalline alloys fabricated via laser powder bed fusion (LPBF). A dataset comprising of 162 experimental data points served as the foundation for the investigation. Each data point encompassed five independent variables: laser power (P), laser scan speed (v), hatch spacing (h), layer thickness (t), and energy density (E), along with three dependent variables: bulk density, Ms, and Hc. The bivariate correlational analysis unveiled that bulk density exhibited a significant correlation with P, v, h, and E, whereas Ms and Hc displayed significant correlations exclusively with v and P, respectively. This divergence may stem from the strong influence of microstructure on magnetic properties, which can be impacted not only by the laser process parameters explored in this study but also by other factors such as oxygen levels within the build chamber. Furthermore, our statistical analysis revealed that bulk density increased with rising P, h, and E, while decreased with higher v. Regarding the magnetic properties, a high Ms was achievable through low v, while low Hc resulted from high P. It was concluded that P and v were considered as the primary laser process parameters, influencing h and t due to their control over the melt-pool size. The application of multiple linear regression analysis allowed the prediction of the bulk density by using both laser process parameters and energy density. This approach offered a valuable alternative to time-consuming and costly trial-and-error experiments, yielding a low error of less than 1 % between the mean predicted and experimental values. Although a slightly higher error of approximately 6 % was observed for Ms, a clear association was established between Ms and v, with lower v values corresponding to higher Ms values. Additionally, a further comparison was conducted between multiple linear regression and three tree-based regression models to explore the effectiveness of these approaches.

Laser-based functionalization for superhydrophobic silicon carbide with mechanical durability, anti-icing and anti-fouling properties

The further applications of silicon carbide (SiC) are limited due to the ease of being contaminated and tendency for icing at low temperature caused by its intrinsically hydrophilicity. In recent years, superhydrophobic surface has been widely employed due to the potential value in anti-fouling and passive anti-icing. In this work, a novel laser ablation-silicone oil heat treatment (LASH) composite process is proposed to fabricate superhydrophobic SiC surface. Many microscale “fence” structures and nanoscale “broccoli” fragmental structures are successfully obtained, which can be adjusted by using different laser processing parameters. Besides, the X-ray photoelectron spectroscopy analysis demonstrates that the effective deposition of low surface energy chemical functional groups is the key to realize the superhydrophobic properties of SiC surface. The coupling effect between the micro/nano structures and low surface energy is confirmed to be important for the stability of Cassie-Baxter state at low temperature. In addition, the freezing process of water droplets on the LASH surface at low temperature and the mechanism of the rapid transition from Wenzel state to Cassie-Baxter state are analyzed. The experimental results indicate that the LASH surface possesses a longer static icing time and keeps good hydrophobicity at −5 °C. The icing temperature of the LASH surface decreases to −17.6 °C while the temperature of the untreated surface is −3.7 °C. Moreover, the LASH surface possesses a lower ice adhesion strength which means it is easier for the ice droplets to break away from the surface. After 20 cycles of icing-deicing experiments, the WCA of the LASH surface is still higher than 150° and its ice adhesion strength slightly increases to 240 kPa. Finally, the mechanical robustness of the LASH surface is studied through the abrasive belt and tape stripping tests, and the anti-fouling property is also evaluated. The change of ice adhesion strength on the LASH surface under cyclic icing experiment is analyzed. The experimental results show that the LASH surface has great mechanical durability and anti-fouling property, which is expected to further expand the application prospects of SiC in different fields.

Colloidal Titanium Nitride Nanoparticles by Laser Ablation in Solvents for Plasmonic Applications.

Titanium nitride (TiN) is a candidate material for several plasmonic applications, and pulsed laser ablation in liquids (PLAL) represents a rapid, scalable, and environmentally friendly approach for the large-scale production of nanomaterials with customized properties. In this work, the nanosecond PLAL process is developed, and we provide a concise understanding of the process parameters, such as the solvent and the laser fluence and pulse wavelength, to the size and structure of the produced TiN nanoparticles (NPs). TiN films of a 0.6 μm thickness developed by direct-current (DC) magnetron sputtering were used as the ablation targets. All laser process parameters lead to the fabrication of spherical NPs, while the laser pulse fluence was used to control the NPs' size. High laser pulse fluence values result in larger TiN NPs (diameter around 42 nm for 5 mJ and 25 nm for 1 mJ), as measured from scanning electron microscopy (SEM). On the other hand, the wavelength of the laser pulse does not affect the mean size of the TiN NPs (24, 26, and 25 nm for 355, 532, and 1064 nm wavelengths, respectively). However, the wavelength plays a vital role in the quality of the produced TiN NPs. Shorter wavelengths result in NPs with fewer defects, as indicated by Raman spectra and XPS analysis. The solvent type also significantly affects the size of the NPs. In aqueous solutions, strong oxidation of the NPs is evident, while organic solvents such as acetone, carbides, and oxides cover the TiN NPs.

Prediction and optimization of joint quality in laser transmission welding using serial artificial neural networks and their integration with Markov decision process

Laser transmission welding is a highly accurate method for joining plastics, but its diverse process parameters require effective modeling for optimal results. Traditional artificial neural networks (ANNs) typically establish predictive models between laser processing parameters and welding strength, neglecting the crucial role of welding morphology in feature extraction, thus diminishing accuracy. To address this, we developed a serial ANN model based on statistically evident correlations, which predicts joint morphology and strength sequentially, resulting in a 47% improvement in predictive accuracy and a mean error of just 7.13%. This two-layered approach effectively reduces the stepwise propagation of errors in ANNs, allowing the first layer to provide a refined data representation for the second layer to predict welding strength. Furthermore, finding the optimal laser parameter set is time-consuming and computationally demanding with traditional ANN-based optimization methods. To address this, we integrated the Markov decision process with the serial ANN for the first time and proposed a novel varying step strategy for the model, enabling a balance of swift convergence and avoidance of suboptimal solutions. Notably, the Markov-serial ANN model attained enhanced optimization results using only 15.5% of the computational resources required by a standard parameter interval optimization methodology. Welding experiments verified the reliability of the Markov-serial ANN, achieving a mean error of 4.54% for welding strength.

Effect of Laser Parameters on Surface Texture of Polyformaldehyde and Parameter Optimization

This research aimed to investigate the influence of laser process parameters on the surface texture of Polyformaldehyde (POM) and to improve its processability and process predictability. A comparative experiment and analysis involving multiple processing parameters, including laser power, scanning speed, and pulse width, were conducted on POM. Statistical prediction models of laser processing POM were established among the laser power, scanning speed, pulse width, texture depth, surface roughness at the bottom of texture, and multi-objective optimization and experimental verification of process parameters were carried out based on the grey-Taguchi analysis method. Experimental results show that the laser power and scanning speed significantly affect the texture depth. Higher laser power and lower scanning speed are conducive to forming depth. The surface roughness at the bottom of the texture increases with the increase in scanning speed and shows a tendency to rise and then fall as the laser power increases. The surface roughness and texture depth obtained under the optimal process parameters(A5B1C1) are 1.373 μm and 466.891 μm, respectively, which were reduced by 10.08 % and increased by 3.42 % compared with the minimum surface roughness and maximum depth in the orthogonal experiments. The validation experiments of the prediction model show that it can meet the reliability requirements, and the errors of the predicted values of depth and surface roughness are 1.86 % and 7.60 %, respectively. The above research provides theoretical and experimental support for the precise control of surface texture prepared by laser processing POM.

One-step fabrication of a self-driven point-of-care chip by femtosecond laser direct writing and its application in cancer cell H2O2 detection via semiconductor-based SERS

Self-driven microfluidic systems have attracted significant attention and demonstrated great potential in the field of point-of-care (POC) testing due to their device simplicity, low power consumption, increased portability, and reduced sample consumption. To develop POC detection chips with diverse characteristics that meet different requirements, there is a strong demand for feasible strategies that enable easy operation and reduce processing time. Here, a one-step processing approach using femtosecond laser direct writing technology was proposed to fabricate a capillary-actuated POC microfluidic chip. The driving force of the chip is highly dependent on its surface wettability, which can be easily adjusted by changing the laser processing parameters. This POC microfluidic chip allowed for the detection of intracellular H2O2 through a catalytic reaction system that incorporated 5-aminosalicylic acid -sensitized colloidal TiO2 nanoparticles and horse radish peroxidase, with integrating semiconductor-based surface-enhanced Raman scattering (SERS) quantitative technique. The concentration of H2O2 was determined by the SERS signal of the catalytic products in the microfluidic chip, resulting in rapid detection with minimal sample consumption. Our method provides a simple, feasible, and alternative strategy for POC testing of H2O2, with a linear range of 10−2∼10−6 M and a limit of detection of 0.55 μM. This approach was successfully applied to rapid detection of intracellular H2O2 in MCF-7 breast cancer cells with high sensitivity and minimal sample consumption. Additionally, this study not only demonstrates the exceptional advantages of femtosecond laser processing technology in fabricating diverse microfluidic chips for various applications, but also presents an efficient POC testing strategy for detecting cell signaling molecules.

Structural and chemical study of complex silver patterns additively manufactured by multi-photon reduction

Multi-photon reduction (MPR) based on femtosecond laser makes rapid prototyping and molding in micro-nano scale feasible, but is limited in material selectivity due to lack of the understanding of the reaction mechanism in MPR process. In this paper, additively manufacturing of complex silver-based patterns through MPR is demonstrated. The effects of laser parameters, including laser pulse energies and scanning speeds, on the structural and chemical characteristics of the printed structures are systematically investigated. The results show that the geometric size of printed cubes deviates from the designed size further by increasing laser pulse energy or decreasing scanning speed. The reaction mechanism of MPR is revealed by studying the elemental composition and chemical structures of printed cubes. The evolution of Raman spectra upon the laser processing parameters suggests that the MPR process mainly includes two processes: reduction and decomposition. In the MPR process, silver ions are reduced and grow into particles by accepting the electrons from ethonal molecules; meanwhile carboxyl groups in polyvinylpyrrolidone are decomposed and form amorphous carbon that is attached on the surface of silver particles. The conductivity of silver wires fabricated by MPR reaches 2 × 105 S m−1 and stays relatively constant as varying their cross section area, suggesting excellent electrical conduction. The understanding of the MPR process would accelerate the development of MPR technology and the implementation of MPR in micro-electromechanical systems could therefore be envisioned.

A Pressure and Proximity Sensor Based on Laser-Induced Graphene.

Smart wearable devices are extensively utilized across diverse domains due to their inherent advantages of flexibility, portability, and real-time monitoring. Among these, flexible sensors demonstrate exceptional pliability and malleability, making them a prominent focus in wearable electronics research. However, the implementation of flexible wearable sensors often entails intricate and time-consuming processes, leading to high costs, which hinder the advancement of the entire field. Here, we report a pressure and proximity sensor based on oxidized laser-induced graphene (oxidized LIG) as a dielectric layer sandwiched by patterned LIG electrodes, which is characterized by high speed and cost-effectiveness. It is found that in the low-frequency range of fewer than 0.1 kHz, the relative dielectric constant of the oxidized LIG layer reaches an order of magnitude of 104. The pressure mode of this bimodal capacitive sensor is capable of detecting pressures within the range of 1.34 Pa to 800 Pa, with a response time of several hundred milliseconds. The proximity mode involves the application of stimulation using an acrylic probe, which demonstrates a detection range from 0.05 mm to 37.8 mm. Additionally, it has a rapid response time of approximately 100 ms, ensuring consistent signal variations throughout both the approach and withdrawal phases. The sensor fabrication method proposed in this project effectively minimizes expenses and accelerates the preparation cycle through precise control of laser processing parameters to shape the electrode-dielectric layer-electrode within a single substrate material. Based on their exceptional combined performance, our pressure and proximity sensors exhibit significant potential in practical applications such as motion monitoring and distance detection.

Ex-vivo parametric study of laser ablation-based drilling of cortical bone.

Frequently orthopedic surgeries require mechanical drilling processes especially for inserted biodegradable screws or removing small bone lesions. However mechanical drilling techniques induce large number of forces as well as have substantially lower material removal rates resulting in prolong healing times. This study focuses on analyzing the impact of quasi-continuous laser drilling on the bone's surface as well as optimizing the drilling conditions to achieve high material removal rates. An ex-vivo study was conducted on the cortical region of desiccated bovine bone. The laser-based drilling on the bovine bine specimens was conducted in an argon atmosphere using a number of laser pulses ranging from 100 to 15,000. The morphology of the resulting laser drilled cavities was characterized using Energy dispersive Spectroscopy (EDS) and the width and depth of the drills were measured using a laser based Profilometer. Data from the profilometer was then used to calculate material removal rates. At last, the material removal rates and laser processing parameters were used to develop a statistical model based on Design of Experiments (DOE) approach to predict the optimal laser drilling parameters. The main outcome of the study based on the laser drilled cavities was that as the number of laser pulses increases, the depth and diameter of the cavities progressively increase. However, the material removal rates revealed a decrease in value at a point between 4000 and 6000 laser pulses. Therefore, based on the sequential sum of square method, a polynomial curve to the 6th power was fit to the experimental data. The predicted equation of the curve had a p-value of 0.0010 indicating statistical significance and predicted the maximum material removal rate to be 32.10 mm3/s with 95%CI [28.3,35.9] which was associated with the optimum number of laser pulses of 4820. Whereas the experimental verification of bone drilling with 4820 laser pulses yielded a material removal rate of 33.37 mm3/s. Therefore, this study found that the carbonized layer formed due to laser processing had a decreased carbon content and helped in increasing the material removal rate. Then using the experimental data, a polymetric equation to the sixth power was developed which predicted the optimized material removal rate to occur at 4820 pulses.

Spray mist-assisted drilling of through silicon vias (TSV) using nanosecond laser: Influence of CNT nanofluid

Through Silicon Vias (TSV) are crucial in semiconductor technology for vertically connecting multiple stacks in 3D packaging. High aspect ratio, smooth and slightly tapered TSVs enhance layout efficiency and void-free filling. Being contact-less and dry-etching process, laser machining is a promising technique to fabricate TSVs. A percussion laser drilling approach was used to fabricate TSVs on a 500 μm thick silicon wafer with a 1064 nm ns laser. Four environments such as air, compressed air jet, water mist, carbon nanotube (CNT) fluid mist were employed to assess laser machining effects on TSV performance in terms of entrance and exit diameters, recast layer, side wall damage, and taper angle. Optimized process parameters (laser pulse energy and pulse number) were derived from an ANN prediction model. Laser drilling under CNT mist produced relatively circular (entrance diameter), straight, and clean TSVs. Reduced debris redeposition was observed under air jet, water mist, and CNT mist compared to air. Minimal sidewall damage occurred under water mist and CNT mist as compared to those machined in air and air jet. CNT mist yielded TSVs with less recast layer (∼7 μm), taper angle (∼1.05 deg.), and heat affected zone (HAZ) thickness (∼50 μm). Enhanced machining quality may be attributed to increased thermal conductivity of CNT nanofluid and pressurized mist flow rate, improving cooling and debris removal. Furthermore, a detailed investigation of TSV using SEM was performed and the findings were compared to those of other research groups.

Influence of Laser Process Parameters on the Forming Quality and Discharge Performance of 3D-Printed Porous Anodes for Al-Air Batteries.

Aluminum-air (Al-air) batteries are considered one of the most promising next-generation energy storage devices. In this paper, we carry out an orthogonal experimental study on the SLM printing process parameters in 3D-printed Al-air battery anodes. The surface roughness, densification, and discharge performance of the electrodes under different process parameters are observed to reveal the effects of different process parameters on the forming quality and discharge performance of aluminum-air battery anodes. The results show that the laser power is the most important factor affecting the surface roughness of the porous aluminum anode, and the scanning spacing is the most important factor affecting the densification. The best printing parameters for the porous aluminum anode can be obtained when the laser power is 325 W, the scanning speed is 1000 mm/s, the scanning spacing is 0.12 mm, and the thickness of the powder spread is 0.03 mm. At this time, the surface roughness of the porous aluminum anode obtained by this process parameter is 15.01 μm, the densification is 94.97%, and the discharge is stable with a high value. In addition, we also carry out data validation to ensure that the data we obtain are optimal and valid.

The effect of laser textured resin surface on the adhesion of supersonic plasma sprayed Al2O3/PF composite coating

Polymer composite materials have rapidly developed due to their unique properties and economic advantages. Despite their prominent physical and mechanical properties, they are unable to meet the higher performance targets in certain exceptional circumstances. Thermal sprayed ceramic/resin composite coating is a feasible solution. Prioritizing the mechanical properties of coating is significant theoretical and scientific value in practical engineering applications. In the article, Al2O3/phenolic resin composite coatings on the textured and sandblasted surface of the glass fiber reinforced polyester are prepared by supersonic plasma spraying. The damage of laser processing periods on resin substrate was discussed. The effect of pit depth and pattern interval on the bonding strength of coating was deeply explored. The results reveal that the highest bonding strength of the coating on textured surface is 28.4 MPa, which is double that of the coating on sandblasted surface. The textured surface can be effectively created with appropriate laser process parameters while avoiding the damage of fiber. On the premise that the glass fiber is not damaged, deeper pits and smaller pattern interval are beneficial for increasing the contact rate between the coating and the substrate. The research provides an effective way to dramatically increase the adhesion of the ceramic/resin composite coating.

Laser-induced color reversal on metal surfaces in acetic acid solution

Laser coloring for decoration and visual attraction has been widely used in daily life. To fulfill the requirements of timely correction or modification of colors, color erasure has also become an important part in marking technology. The thickness of the oxide layer and the concentration of oxygen elements are key factors affecting the quality of color erasing. The conventional method is to erase the color in air, which is difficult to remove the oxide film. Acetic acid, as an environment-friendly solution, which provides a low oxygen environment and can undergo chemical reactions with titanium dioxide under laser heating, is selected as a liquid environment for laser-induced color erasure. Oxygen concentration in the erased area decreases from more than 50% to 10%. The color difference ΔEab* between the erased area and original metal surface is around 1.4, which shows almost no difference to the naked eyes. Furthermore, the color difference ΔEab* between laser re-coloring and laser coloring before the erasure is around 1.5, which means that the re-coloring under the same laser processing parameters after the erasure maintains a high level of consistency with the colors initially drawn. Here we successfully realize the reversal process from laser coloring to laser erasure and laser re-coloring on metal surfaces. This technology has considerable applications in the field of anti-counterfeiting and information storage. Meanwhile, acetic acid assisted laser color erasing as a safe and green method greatly improves the erasure quality and enhances the development of laser color marking technology.

Preparation and Wettability Analysis of Metal Biofunctional Surfaces Based on the Microquadrangular Structure.

Improving the hydrophobic properties of aluminum alloys is crucial for industry. In previous reports, researchers prepared superhydrophobic surfaces by fabricating micro-nanostructures on the metal surface with a nanosecond laser. However, no researchers have formed microquadrangular groove structures on the metal surface. In this article, inspired by the bamboo leaf, a microquadrangular structure is designed and processed using nanosecond laser technology to form a superhydrophobic functional surface. The effects of laser processing parameters, such as laser power, scanning speed, scanning time, defocus and fill spacing on the size, surface morphology features, and wettability of the microquadrangular structure, are investigated by a single-factor experimental method. The experimental results show the optimal size of the processed microquadrangular structure obtained from the experiment with an error of 1.28% from the design size, where the fill spacing has the greatest effect on the size and the scanning time, defocus, and fill spacing have great influence on the surface morphology. The contact angle of water drops on the surface can reach 154.7°, and the power has the greatest influence on the wettability. Laser parameters have distinct effects on the properties of the materials. Therefore, by regulation of the laser parameters, the formation of the microstructure can be availably controlled and the result of hydrophobicity can be achieved.

Experimental Parametric Investigation of Nanosecond Laser-Induced Surface Graphitization of Nano-Crystalline Diamond.

While nano-crystalline diamond (NCD) is a promising engineering composite material for its unique mechanical properties, achieving the ultrahigh surface quality of NCD-based components through conventional grinding and polishing is challenging due to its exceptional hardness and brittleness. In the present work, we experimentally investigate the nanosecond laser ablation-induced graphitization characteristics of NCD, which provides a critical pretreatment method of NCD for realizing its superlative surface finish. Specifically, systematic experimental investigations of the nanosecond pulsed laser ablation of NCD are carried out, in which the characteristics of graphitization are qualitatively characterized by the Raman spectroscopy detection of the ablated area of the microhole and microgroove. Subsequently, the influence of laser processing parameters on the degree and morphological characteristics of graphitization is evaluated based on experimental data and related interpretation, from which optimized parameters for maximizing the graphitization of NCD are then identified. The findings reported in the current work provide guidance for promoting the machinability of NCD via laser irradiation-induced surface modification.

Research on Extrusion Forming Process of Micro Internal Thread for Nickel-plated Aluminum Alloy Parts

Abstract With the development of electronic products in the direction of miniaturization and lightweight, the specifications of thread gradually become minor, and the high-precision forming of micro threads has become an urgent problem to be solved. In this paper, the extrusion forming process of the micro internal thread was mainly studied on the nickel-plated aluminum alloy parts. The process route suitable for the internal thread forming on electroplated parts was designed, and the key parameters of thread bottom hole diameter and thread tapping speed were determined by experiment. Aiming at the typical problem of internal thread blocked by a broken tap, a thread repair method based on laser ablation was proposed and the laser processing parameters were optimized. Eventually, the manufacturing of M1 micro internal thread on nickel-plated aluminum alloy parts was successfully realized.

A FeCrAl-Al2O3 Composite Produced Via Laser Powder Bed Fusion of a Mixed Powder for Porous Catalyst Scaffolds

Abstract This study proposes a novel approach for synthesizing and etching bicontinuous FeCrAl-Al2O3 composites as a means for replacing FeCrAl foams as catalyst scaffolds in biodriven alcohol reactors for jet-fuel production. Conventional FeCrAl foams suffer from poor availability and consequent high costs. New additive manufacturing techniques provide an opportunity to produce tailored foams at reasonable times and at acceptable costs. This research aimed to generate a porous FeCrAl structure by etching a bicontinuous FeCrAl-Al2O3 composite produced by laser powder bed fusion of amalgamated FeCrAl and Al2O3 powders. The composite powder for laser powder bed fusion is created by ball-milling FeCrAl and Al2O3 powders. This research focuses on achieving a bi-continuous FeCrAl-Al2O3 structure, essential for the selective removal of the ceramic phase. The influence of laser processing parameters on the microstructure was examined across a range of laser powers (60–120 W) and scan speeds (100–400 mm/s), showing that higher powers and speeds produce finer metal struts. A bi-continuous microstructure was consistently obtained, marking a key achievement. The Al2O3 removal process involved a two-step etching method using hydrochloric and phosphoric acids, tested across various etching times. The alumina phase was reduced from 36 vol% to 17 vol% (corresponding to an increase in porosity from 24 vol% to 43 vol%), showing the potential for use as a porous catalyst scaffold. This research demonstrates the potential for using additive manufacturing to produce porous FeCrAl structures capable of replacing hard-to-source FeCrAl foams.