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2021 Vol. 3, No. 1

Helium-ion-beam nanofabrication: extreme processes and applications
Shixuan He, Rong Tian, Wei Wu, Wen-Di Li, Deqiang Wang
2021, 3(1) doi: 10.1088/2631-7990/abc673

Helium ion beam (HIB) technology plays an important role in the extreme fields of nanofabrication. This paper reviews the latest developments in HIB technology as well as its extreme processing capabilities and widespread applications in nanofabrication. HIB-based nanofabrication includes direct-write milling, ion beam-induced deposition, and direct-write lithography without resist assistance. HIB nanoscale applications have also been evaluated in the areas of integrated circuits, materials sciences, nano-optics, and biological sciences. This review covers four thematic applications of HIB: (1) helium ion microscopy imaging for biological samples and semiconductors; (2) HIB milling and swelling for 2D/3D nanopore fabrication; (3) HIB-induced deposition for nanopillars, nanowires, and 3D nanostructures; (4) additional HIB direct writing for resist, graphene, and plasmonic nanostructures. This paper concludes with a summary of potential future applications and areas of improvement for HIB extreme nanofabrication technology.

Recent progress in laser texturing of battery materials: a review of tuning electrochemical performances, related material development, and prospects for large-scale manufacturing
Wilhelm Pfleging
2021, 3(1) doi: 10.1088/2631-7990/abca84

Traditional electrode manufacturing for lithium-ion batteries is well established, reliable, and has already reached high processing speeds and improvements in production costs. For modern electric vehicles, however, the need for batteries with high gravimetric and volumetric energy densities at cell level is increasing; and new production concepts are required for this purpose. During the last decade, laser processing of battery materials emerged as a promising processing tool for either improving manufacturing flexibility and product reliability or enhancing battery performances. Laser cutting and welding already reached a high level of maturity and it is obvious that in the near future they will become frequently implemented in battery production lines. This review focuses on laser texturing of electrode materials due to its high potential for significantly enhancing battery performances beyond state-of-the-art. Technical approaches and processing strategies for new electrode architectures and concepts will be presented and discussed with regard to energy and power density requirements. The boost of electrochemical performances due to laser texturing of energy storage materials is currently proven at the laboratory scale. However, promising developments in high-power, ultrafast laser technology may push laser structuring of batteries to the next technical readiness level soon. For demonstration in pilot lines adapted to future cell production, process upscaling regarding footprint area and processing speed are the main issues as well as the economic aspects with regards to CapEx amortization and the benefits resulting from the next generation battery. This review begins with an introduction of the three-dimensional battery and thick film concept, made possible by laser texturing. Laser processing of electrode components, namely current collectors, anodes, and cathodes will be presented. Different types of electrode architectures, such as holes, grids, and lines, were generated; their impact on battery performances are illustrated. The usage of high-energy materials, which are on the threshold of commercialization, is highlighted. Battery performance increase is triggered by controlling lithium-ion diffusion kinetics in liquid electrolyte filled porous electrodes. This review concludes with a discussion of various laser parameter tasks for process upscaling in a new type of extreme manufacturing.

An overview of laser-based multiple metallic material additive manufacturing: from macro- to micro-scales
Chao Wei, Zhizhou Zhang, Dongxu Cheng, Zhe Sun, Menghui Zhu, Lin Li
2021, 3(1) doi: 10.1088/2631-7990/abce04

Additive manufacturing (AM) is an emerging customized three-dimensional (3D) functional product fabrication technology. It provides a higher degree of design freedom, reduces manufacturing steps, cost and production cycles. However, existing metallic component 3D printing techniques are mainly for the manufacture of single material components. With the increasing commercial applications of AM technologies, the need for 3D printing of more than one type of dissimilar materials in a single component increases. Therefore, investigations on multi-material AM (MMAM) emerge over the past decade. Lasers are currently widely used for the AM of metallic components where high temperatures are involved. Here we report the progress and trend in laser-based macro- and micro-scale AM of multiple metallic components. The methods covered in this paper include laser powder bed fusion, laser powder directed energy deposition, and laser-induced forward transfer for MMAM applications. The principles and process/material characteristics are described. Potential applications and challenges are discussed. Finally, future research directions and prospects are proposed.

Feasibility study of wave-motion milling of carbon fiber reinforced plastic holes
Deyuan Zhang, Zhenyu Shao, Daxi Geng, Xinggang Jiang, Yihang Liu, Zehua Zhou, Shaomin Li
2021, 3(1) doi: 10.1088/2631-7990/abc675

Carbon fiber reinforced plastic (CFRP) has been applied in aeronautics, aerospace, automotive and medical industries due to its superior mechanical properties. However, due to its difficult-to-cut characteristic, various damages in twist drilling and chip removal clog in core drilling could happen, inevitably reducing hole quality and hole-manufacturing efficiency. This paper proposes the wave-motion milling (WMM) method for CFRP hole-manufacturing to improve hole quality. This paper presents a motion path model based on the kinematics of the WMM method. The wave-motion cutting mode in WMM was analyzed first. Then, comparison experiments on WMM and conventional helical milling (CHM) of CFRP were carried out under dry conditions. The results showed that the hole surface quality of the CFRP significantly improved with a decrease of 18.1%–36% of Ra value in WMM compared to CHM. WMM exerted a significantly weaker thrust force than that of CHM with a reduction of 12.0%–24.9% and 3%–7.7% for different axial feed per tooth and tangential feed per tooth, respectively. Meanwhile, the hole exit damages significantly decreased in WMM. The average tear length at the hole exit in WMM was reduced by 3.5%–29.5% and 35.5%–44.7% at different axial feed per tooth and tangential feed per tooth, respectively. Moreover, WMM significantly alleviated tool wear. The experimental results suggest that WMM is an effective and promising strategy for CFRP hole-manufacturing.

Challenges in laser-assisted milling of titanium alloys
Matthew S Dargusch, Tharmalingam Sivarupan, Michael Bermingham, Rizwan Abdul Rahman Rashid, Suresh Palanisamy, Shoujin Sun
2021, 3(1) doi: 10.1088/2631-7990/abc26b

Several detailed studies have comprehensively investigated the benefits and limitations of laser-assisted machining (LAM) of titanium alloys. These studies have highlighted the positive impact of the application of laser preheating on reducing cutting forces and improving productivity but have also identified the detrimental effect of LAM on tool life. This paper seeks to evaluate a series of the most common cutting tools with different coating types used in the machining of titanium alloys to identify whether coating type has a dramatic effect on the dominant tool wear mechanisms active during the process. The findings provide a clear illustration that the challenges facing the application of LAM are associated with the development of new types of cutting tools which are not subjected to the diffusion-controlled wear processes that dominate the performance of current cutting tools.

Laser metal deposition of refractory high-entropy alloys for high-throughput synthesis and structure-property characterization
Henrik Dobbelstein, Easo P George, Evgeny L Gurevich, Aleksander Kostka, Andreas Ostendorf, Guillaume Laplanche
2021, 3(1) doi: 10.1088/2631-7990/abcca8

Progress in materials development is often paced by the time required to produce and evaluate a large number of alloys with different chemical compositions. This applies especially to refractory high-entropy alloys (RHEAs), which are difficult to synthesize and process by conventional methods. To evaluate a possible way to accelerate the process, high-throughput laser metal deposition was used in this work to prepare a quinary RHEA, TiZrNbHfTa, as well as its quaternary and ternary subsystems by in-situ alloying of elemental powders. Compositionally graded variants of the quinary RHEA were also analyzed. Our results show that the influence of various parameters such as powder shape and purity, alloy composition, and especially the solidification range, on the processability, microstructure, porosity, and mechanical properties can be investigated rapidly. The strength of these alloys was mainly affected by the oxygen and nitrogen contents of the starting powders, while substitutional solid solution strengthening played a minor role.

3D printed fiber sockets for plug and play micro-optics
Parvathi S Nair, Jonathan Trisno, Hongtao Wang, Joel K W Yang
2021, 3(1) doi: 10.1088/2631-7990/abc674

Integrating micro-optical components at the end facet of an optical fiber enables compact optics to shape the output beam (e.g. collimating, focusing, and coupling to free space elements or photonic integrated circuits). However, the scalability of this approach is a longstanding challenge as these components must be aligned onto individual fiber facets. In this paper, we propose a socket that enables easy slotting of fibers, self-alignment, and coupling onto micro-optical components. This integrated socket can be detached from the substrate upon fiber insertion to create a stand-alone optical system. Fabrication is done using nanoscale 3D printing via two-photon polymerization lithography onto glass substrates, which allows multiple sockets to be patterned in a single print. We investigated variations in socket design and evaluated the performance of optical elements for telecom wavelengths. We obtained an alignment accuracy of ~3.5 µm. These socket designs can be customized for high efficiency chip to fiber coupling and extended to other spectral ranges for free-form optics.