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2020 Vol. 2, No. 1

Reviews
A critical review on the chemical wear and wear suppression of diamond tools in diamond cutting of ferrous metals
Guo Jiang, Zhang Jianguo, Pan Yanan, Kang Renke, Namba Yoshiharu, Shore Paul, Yue Xiaobin, Wang Baorui, Guo Dongming
2020, 2(1) doi: 10.1088/2631-7990/ab5d8f
Abstract:
Diamond tools play a critical role in ultra-precision machining due to their excellent physical and mechanical material properties, such as that cutting edge can be sharpened to nanoscale accuracy. However, abrasive chemical reactions between diamond and non-diamond-machinable metal elements, including Fe, Cr, Ti, Ni, etc, can cause excessive tool wear in diamond cutting of such metals and most of their alloys. This paper reviews the latest achievements in the chemical wear and wear suppression methods for diamond tools in cutting of ferrous metals. The focus will be on the wear mechanism of diamond tools, and the typical wear reduction methods for diamond cutting of ferrous metals, including ultrasonic vibration cutting, cryogenic cutting, surface nitridation and plasma assisted cutting, etc. Relevant commercially available devices are introduced as well. Furthermore, future research trends in diamond tool wear suppression are discussed and examined.
A review of processing of Cu/C base plate composites for interfacial control and improved properties
Jean-François Silvain, Jean-Marc Heintz, Amélie Veillere, Loic Constantin, Yong Feng Lu
2020, 2(1) doi: 10.1088/2631-7990/ab61c5
Abstract:

Metal matrix composite (MMC) materials have attracted tremendous interest since the early 2000s because of their superior physical, mechanical, thermal, and electrical properties compared to pure metals or alloys. The interest in developing MMCs can be explained by their unique features but especially by the fact that the properties can be tailored depending on the nature and concentration of the reinforcements. MMCs have found applications in a vast number of industries, such as aerospace, automotive, electronics which are the focus here.

The constant increase of power and packing densities in power electronic devices has led to heat dissipation issues. Significant demand for developing an efficient heat-dissipating material with a high thermal conductivity (TC) and a low coefficient of thermal expansion (CTE) has appeared in the past decades. To meet this demand, it is necessary to fabricate a material compatible with the electronic chip while ensuring the reliability of the power modules. Among the large number of MMCs, copper (Cu) and aluminum (Al) are the most advanced composites for thermal management applications (i.e., base plate, heat sink, and exchanger). Often carbon materials (C) such as carbon fibers, diamond, graphene or carbon nanotubes are added to the metal matrix because of their high TC and low CTE values. Cu/C and Al/C composites materials have already demonstrated their superior properties compare to current electronic packaging. Lower and tailorable CTE were observed depending on the volume fraction of reinforcement (e.g., CTE decreases when C concentration increases). High heat dissipation capability was shown, which surpass commercial heat exchangers. The addition of a lightweight reinforcement lowered the density of the material, making them attractive for aeronautics applications. Finally, high stiffness at elevated temperatures was tested and resulted in dimensional stability for high-temperature applications. Also, it is worth to note that the final properties of MMCs depend not only on the primary constituent of the materials but also on the fabrication methods.

In this paper, the Cu/C composites fabricated by powder metallurgy and hot uniaxial pressing are reviewed. Thermal analyses indicate that interfacial treatment is required to achieve high thermal and thermomechanical properties for all processing methods. An in-depth review of the interface control through novel surface treatments is presented such as interphase creation and unique processing methods. The review also focuses on the thermal transfer between the matrix and reinforcement. It is shown that proper control of the interfaces will form the right chemical/mechanical bonding, which enhances thermal and thermomechanical properties of the Cu/C composites.

Additive manufacturing in radiation oncology: a review of clinical practice, emerging trends and research opportunities
Rance Tino, Martin Leary, Adam Yeo, Elizabeth Kyriakou, Tomas Kron, Milan Brandt
2020, 2(1) doi: 10.1088/2631-7990/ab70af
Abstract:
The additive manufacturing (AM) process plays an important role in enabling cross-disciplinary research in engineering and personalised medicine. Commercially available clinical tools currently utilised in radiotherapy are typically based on traditional manufacturing processes, often leading to non-conformal geometries, time-consuming manufacturing process and highcosts. An emerging application explores the design and development of patient-specific clinical tools using AM to optimise treatment outcomes among cancer patients receiving radiation therapy. In this review, we:

• highlight the key advantages of AM in radiotherapy where rapid prototyping allows for patient-specific manufacture

• explore common clinical workflows involving radiotherapy tools such as bolus,compensators, anthropomorphic phantoms, immobilisers, and brachytherapy moulds; and

• investigate how current AM processes are exploited by researchers to achieve patient tissue-like imaging and dose attenuations.

Finally, significant AM research opportunities in this space are highlighted for their future advancements in radiotherapy for diagnostic and clinical research applications.

Surface modification and functionalization by electrical discharge coating: a comprehensive review
Pay Jun Liew, Ching Yee Yap, Jingsi Wang, Tianfeng Zhou, Jiwang Yan
2020, 2(1) doi: 10.1088/2631-7990/ab7332
Abstract:
Hard coatings are extensively required in industry for protecting mechanical/structural parts that withstand extremely high temperature, stress, chemical corrosion, and other hostile environments. Electrical discharge coating (EDC) is an emerging surface modification technology to produce such hard coatings by using electrical discharges to coat a layer of material on workpiece surface to modify and enhance the surface characteristics or create new surface functions. This paper presents a comprehensive overview of EDC technologies for various materials, and summarises the types and key parameters of EDC processes as well as the characteristics of resulting coatings. It provides a systematic summary of the fundamentals and key features of the EDC processes, as well as its applications and future trends.
The recent development of soft x-ray interference lithography in SSRF
Jun Zhao, Shumin Yang, Chaofan Xue, Liansheng Wang, Zhaofeng Liang, Lei Zhang, Yong Wang, Yanqing Wu, Renzhong Tai
2020, 2(1) doi: 10.1088/2631-7990/ab70ae
Abstract:

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This paper introduces the recent progress in methodologies and their related applications based on the soft x-ray interference lithography beamline in the Shanghai synchrotron radiation facility. Dual-beam, multibeam interference lithography and Talbot lithography have been adopted as basic methods in the beamline. To improve the experimental performance, a precisereal-time vibration evaluation system has been established; and the lithography stability has been greatly improved. In order to meet the demands for higher resolution and practical application, novel experimental methods have been developed, such as high-order diffraction interference exposure, high-aspect-ratio and large-area stitching exposure, and parallel direct writing achromatic Talbot lithography. As of now, a 25 nm half-pitch pattern has been obtained; and a cmexposure area has been achieved in practical samples. The above methods have been applied to extreme ultraviolet photoresist evaluation, photonic crystal and surface plasmonic effect research, and so on.

Deformation and removal of semiconductor and laser single crystals at extremely small scales
Yueqin Wu, Dekui Mu, Han Huang
2020, 2(1) doi: 10.1088/2631-7990/ab7a2a
Abstract:

Semiconductor and laser single crystals are usually brittle and hard, which need to be ground to have satisfactory surface integrity and dimensional precision prior to their applications. Improvement of the surface integrity of a ground crystal can shorten the time of a subsequent polishing process, thus reducing the manufacturing cost. The development of cost-effective grinding technologies for those crystals requires an in-depth understanding of their deformation and removal mechanisms. As a result, a great deal of research efforts were directed towards studying this topic in the past two or three decades. In this review, we aimed to summarize the deformation and removal characteristics of representative semiconductor and laser single crystals in accordance with the scale of mechanical loading, especially at extremely small scales. Their removal mechanisms were critically examined based on the evidence obtained from high-resolution TEM analyses. The relationships between machining conditions and removal behaviors were discussed to provide a guidance for further advancing of the grinding technologies for those crystals.

Research
Underwater persistent bubble-assisted femtosecond laser ablation for hierarchical micro/nanostructuring
Dongshi Zhang, Bikas Ranjan, Takuo Tanaka, Koji Sugioka
2020, 2(1) doi: 10.1088/2631-7990/ab729f
Abstract:
Laser offers ability of performing surface processing and synthesis of nanomaterials at the same time, so called “two birds with one stone”, which is beneficial for a large variety of practical applications. Prof. Sugioka’s team aims at research and development of extreme manufacturing techniques based on lasers which can realize low environmental load, high quality, high efficiency fabrication of materials using ultrafast lasers such as femtosecond and picosecond lasers. The developed techniques include three-dimensional (3D) micro/nanofabrication, hierarchical micro/nanostructuring, high aspect ratio machining, and synthesis of new materials. In this paper, a new processing technique termed underwater persistent bubble assisted femtosecond laser ablation in liquids (UPB-fs-LAL) is presented, which can produce concentric circular macrostructures with millimeter-scale tails on silicon substrates. Long-tailed macrostructures are composed of layered fan-shaped (central angles of 45°–141°) hierarchical micro/nanostructures, which are produced by fan-shaped beams refracted at the mobile bubble interface (≥50° light tilt, referred to as the vertical incident direction) during UPB-fs-LAL with a line-by-line scanning scheme. Centric circular macrostructures contain low/high/ultrahigh spatial frequency laser-induced periodic surface structures (LSFLs/HSFLs/UHSFLs) with periods of 550–900, 100–200, 40–100 nm, which are produced by fs-LAL with the aid of stationary bubbles in water. A period of 40 nm, less than 1/25th of the laser wavelength (1030 nm), is the finest laser-induced periodic surface structures (LIPSS) among ever created on silicon. This research opens up new possibilities for laser materials processing, since it enables template-free cost-effective laser structuring of arrays of hierarchical micro/nanostructures. Such bubble-based laser processing may further increase versatility of the laser processing.
A high quality surface finish grinding process to produce total reflection mirror for x-ray fluorescence analysis
Hitoshi Ohmori, Shinjiro Umezu, Yunji Kim, Yoshihiro Uehara, Hiroshi Kasuga, Teruko Kato, Nobuhide Itoh, Syuhei Kurokawa, Takayuki Kusumi, Yugo Sugawara, Shinsuke Kunimura
2020, 2(1) doi: 10.1088/2631-7990/ab7a29
Abstract:

Total reflection x-ray fluorescence analysis is applied to trace element detection in liquid for effective environmental monitoring. This analytical approach requires x-ray total reflection mirrors. In order to achieve high sensitivity element detection, the mirrors require high surface quality for high x-ray reflectivity. Surface finishing for x-ray mirrors is typically conducted through a series of abrasive processes, such as grinding and polishing, and is thus time consuming. The purpose of this study is to streamline and enhance the surface finishing process based on unique high quality grinding techniques for the production of x-ray total reflection mirrors.

Periodic energy decomposition analysis for electronic transport studies as a tool for atomic scale device manufacturing
Paven Thomas Mathew, Fengzhou Fang
2020, 2(1) doi: 10.1088/2631-7990/ab5d8a
Abstract:
With the increasing technological growth, the need for more precise and accurate level of manufacturing is inevitable. This enhanced precision helps to reduce the size of transistors and other integrated circuit components for improved functionality of devices. Atomic/close-to-atomic scale manufacturing (ACSM) is a necessity to achieve this size reduction. Prof. Fengzhou Fang’s team at the Centre of Micro/Nano Manufacturing Technology (MNMT) aims in developing fundamental aspects and perspectives to realise ACSM. Since this research is in its early stage, a relevant study is performed both in theoretical, with the aid of Density Functional Theory (DFT) and experimentation using Atomic Force Microscope (AFM). For developing atomic scale devices, the use of molecules are important since they are defect free and can reduce the device size considerably. However, the difficult of attaching molecules to the electrodes is a daunting task. For this, the effect of interactions taking place at the electrode-molecule junction need to be explored. Periodic Energy Decomposition Analysis (pEDA) is a recently modified method to find the bonding interactions happening between two fragments. This provides information on different types of bonding, which can be repulsive or attractive, when two fragments are brought together. A novel idea of combining pEDA and electronic transport studies to improve the development of molecular devices is presented in this paper. Moreover, this study can lead to the following aspects of molecular device fabrication. Firstly, the importance of electronic transport and conduction across the molecular junction largely depends on the bonding between electrode material and the molecule. Secondly, the selection of molecule and the electrode material is crucial for a stable and robust connection for the device functionality and finally. The point of attachment should be a single atom so that the influence of neighbouring atoms in interfering with the smooth flow of current can be reduced. This paper provides detailed information on the former two and urges the researchers to find ways to achieve the latter by atomic scale material removal. Hence, a link between pEDA and electronic transport not only helps in molecular device development, but also, pave ways for realising ACSM methods.