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Ultrafast laser technology has moved from ultrafast to ultra-strong due to the development of chirped pulse amplification technology. Ultrafast laser technology, such as femtosecond lasers and picosecond lasers, has quickly become a flexible tool for processing brittle and hard materials and complex micro-components, which are widely used in and developed for medical, aerospace, semiconductor applications and so on. However, the mechanisms of the interaction between an ultrafast laser and brittle and hard materials are still unclear. Meanwhile, the ultrafast laser processing of these materials is still a challenge. Additionally, highly efficient and high-precision manufacturing using ultrafast lasers needs to be developed. This review is focused on the common challenges and current status of the ultrafast laser processing of brittle and hard materials, such as nickel-based superalloys, thermal barrier ceramics, diamond, silicon dioxide, and silicon carbide composites. Firstly, different materials are distinguished according to their bandgap width, thermal conductivity and other characteristics in order to reveal the absorption mechanism of the laser energy during the ultrafast laser processing of brittle and hard materials. Secondly, the mechanism of laser energy transfer and transformation is investigated by analyzing the interaction between the photons and the electrons and ions in laser-induced plasma, as well as the interaction with the continuum of the materials. Thirdly, the relationship between key parameters and ultrafast laser processing quality is discussed. Finally, the methods for achieving highly efficient and high-precision manufacturing of complex three-dimensional micro-components are explored in detail.

An auxetic design is proposed by soft–hard material integration and demonstrate negative Poisson's ratio (NPR) can be achieved by leveraging unique rotation features of non-connected hard particles in a soft matrix. A theoretical mechanics framework that describes rotation of hard particles in a soft matrix under a mechanical loading is incorporated with overall Poisson's ratio of the soft–hard integrated metamaterials. The theoretical analysis shows that the auxetic behaviour of the soft–hard integrated structures not only relies critically on geometry of particles, but also depends on their periodic arrangements in the soft matrix. Extensive finite-element analyses (FEA) are performed and validate the theoretical predictions of hard-particle rotation and overall Poisson's ratio of soft–hard integrated structures. Furthermore, uniaxial tensile tests are carried out on three-dimensional printed soft–hard integrated structures and confirm auxetic behaviour of soft–hard integrated structures enabled by the rotation of hard particles. Besides, Poisson's ratio varies nonlinearly with the thickness of specimens and reaches a maximum NPR far out of the bounds of plane stress and plane strain situations, which agrees well with FEA. This work provides a theoretical foundation for the design of mechanical metamaterials enabled by soft–hard material integration with auxetic deformation behaviour.

Throughout human history, any society’s capacity to fabricate and refine new materials to satisfy its demands has resulted in advances to its performance and worldwide standing. Life in the twenty-first century cannot be predicated on tiny groupings of materials; rather, it must be predicated on huge families of novel elements dubbed “advanced materials”. While there are several approaches and strategies for fabricating advanced materials, mechanical milling (MM) and mechanochemistry have garnered much interest and consideration as novel ways for synthesizing a diverse range of new materials that cannot be synthesized by conventional means. Equilibrium, nonequilibrium, and nanocomposite materials can be easily obtained by MM. This review article has been addressed in part to present a brief history of ball milling’s application in the manufacture of a diverse variety of complex and innovative materials during the last 50 years. Furthermore, the mechanism of the MM process will be discussed, as well as the factors affecting the milling process. Typical examples of some systems developed at the Nanotechnology and Applications Program of the Kuwait Institute for Scientific Research during the last five years will be presented in this articles. Nanodiamonds, nanocrystalline hard materials (e.g., WC), metal-matrix and ceramic matrix nanocomposites, and nanocrystalline titanium nitride will be presented and discussed. The authors hope that the article will benefit readers and act as a primer for engineers and researchers beginning on material production projects using mechanical milling.

The cold spray or Supersonic Particle Deposition technique has great potential for producing ceramic nanostructured coatings. This technique operates at a processing temperature that is low enough to preserve the initial feedstock materials’ microstructure. Nevertheless, depositing ceramic powders using a cold spray can be challenging because of the materials’ brittle nature. The interaction between substrate and particles is significantly influenced by substrate attributes, including hardness, material nature, degree of oxidation and temperature. In this study, the effect of the substrate’s remaining oxide composition on the adhesion strength of an agglomerated nano-TiO2 coating was investigated. The results showed that the coating adhesion strength increased for hard materials such as stainless steel and pure chromium as the annealed substrate temperature also increased from room temperature to 700 °C, indicating thicker oxide on the substrate surface. TiO2 particles mainly bond with SUS304 substrates through oxide bonding, which results from a chemical reaction involving TiO2-OH−. Chromium oxide (Cr2O3) is thermodynamically preferred in SUS304 and provides the OH− component required for the reaction. SUS304 shows a thermodynamic preference for chromium oxide (Cr2O3), and this enables Cr2O3 to provide the necessary OH− component for the reaction.

High quality, highly efficient finishing processes are required for finishing difficult-to-machine materials. Magnetic abrasive finishing (MAF) process is a finishing method that can obtain a high accuracy surface using fine magnetic particles and abrasive particles, but has poor finishing efficiency. On the contrary, fixed abrasive polishing (FAP) is a polishing process can obtain high material removal efficiency but often cannot provide a high-quality surface at the nano-scale. Therefore, this work proposes a new finishing process, which combines the magnetic abrasive finishing process and the fixed abrasive polishing process (MAF-FAP). To verify the proposed methodology, a finishing device was developed and finishing experiments on alumina ceramic plates were performed. Furthermore, the mechanism of the MAF-FAP process was investigated. In addition, the influence of process parameters on finishing characteristics is discussed. According to the experimental results, this process can achieve high-efficiency finishing of brittle hard materials (alumina ceramics) and can obtain nano-scale surfaces. The surface roughness of the alumina ceramic plate is improved from 202.11 nm Ra to 3.67 nm Ra within 30 min.

The strain γ processing at high-pressure torsion (HPT) deformation for many hard materials is really much smaller than expected. This is a result of slippage of sample surface and surface of anvils. In this context, the authors develop a new method- “accumulative high-pressure torsion” (ACC HPT). This method enables producing much higher true strains in metallic and alloys than the traditional HPT method. HPT and ACC HPT were applied to β-Ti-alloys Ti-18Zr-15Nb. As TEM studies showed, the size of grains after HPT n = 10 revolutions is about 40 nm while the size of grains after ACC HPT with n = 10 revolutions (in total) is about 20 nm.

The paper discusses abrasive water-jet cutting of hard-to-cut materials represented by high carbon steel DIN norm No.1.2436 (CSN EN 19437) plate 61–mm-thick and high-strength concrete cube sized 150 mm. Four relatively hard minerals with different densities not commonly used in water-jet technology were tested and their cutting results compared to those of three types of almandine garnets: Ukraine, Australian, and sorted Australian. Cutting efficiency was evaluated utilizing declination angle. Dependence of cutting efficiency on abrasive density and hardness was investigated. High density of abrasive appeared to be disadvantageous in our experiment. Cutting efficiency dependence on hardness exhibited nearly linear course, the increase was much more significant for concrete than for steel. Evaluation of experimental results led to the conclusion that cutting mechanism in case of very thick samples is different from common abrasive waterjet cutting. The limit declination angle for thick samples is significantly smaller, it was found to be approximately 22°. This result represents entirely new finding. The most promising finding from the economical point of view appears to be behavior of corundum, when cutting concrete. Our experimental results promise 20 % increase in cutting speed for brittle materials.

Titanium and its alloys have been widely used as biomedical implant materials due to their low density, good mechanical properties, superior corrosion resistance and biocompatibility when compared with other metallic biomaterials such as Co–Cr alloys and

First-principles calculations of the relative stability, structure, and physical properties of carbon nitride polymorphs predict a cubic form of C$_3$N$_4$ with a zero-pressure bulk modulus exceeding that of diamond. Like diamond, this new phase could potentially be synthesized at high pressure and quenched to ambient pressure for use as a superhard material. The calculations also predict that α-C$_3$N$_4$ and graphite-C$_3$N$_4$ are energetically favored relative to β-C$_3$N$_4$ and that published diffraction data can be re-indexed as α-C$_3$N$_4$ with lower error.

The properties of organic solids depend on their structure and morphology, yet direct imaging using conventional electron microscopy methods is hampered by the complex internal structure of these materials and their sensitivity to electron beams. Here, we manage to observe the nanocrystalline structure of two organic molecular thin-film systems using transmission electron microscopy by employing a scanning nanodiffraction method that allows for full access to reciprocal space over the size of a spatially localized probe (~2 nm). The morphologies revealed by this technique vary from grains with pronounced segmentation of the structure—characterized by sharp grain boundaries and overlapping domains—to liquid-crystal structures with crystalline orientations varying smoothly over all possible rotations that contain disclinations representing singularities in the director field. The results show how structure–property relationships can be visualized in organic systems using techniques previously only available for hard materials such as metals and ceramics.Scanning electron nanobeam diffraction is used to monitor the morphology of organic thin films with nanometre resolution, revealing information on the arrangement of crystalline domains useful for structure–property relationship understanding.