Investigations and Applications in Advanced Materials Processing

Advanced structural materials have been widely used in modern industries, such as mining, building, aerospace, chip manufacturing and surface engineering. High-precision materials handling results in prolonged tool life, damage free-surfaces, artificial implants, etc. Therefore, a comprehensive understanding of material mechanisms and behaviors is a necessity, facilitating the extraordinary performance of such materials in industrial applications.

Material processing problems are encountered in a myriad of experimental analyses and testing situations. For instance, when polishing the silicon wafer, damage-free surfaces and high polishing efficiency are essential in the post-processing stage. Specifically, an extremely planarized surface is the solid ground of applying lithography to fabricate the wafers [1,2]. The most commonly used handling method is chemical mechanical polishing (CMP), which is a wear-based, surface flattening process involving the addition of chemicals and mechanical actions [3]. CMP has been widely exploited when polishing various kinds of advanced materials, such as aluminum [4], crystal [5], ceramics [6], and silicon [7]. During the planarization process, the friction force generated by the abrasive particles removes the chemical reacted surface. Then, processing parameters such as the chemical content, the size of the particles, the speed of rotation, etc., contribute to the efficient material removal rate (MRR) in the planarization process [8,9]. Xie et al. [10] developed a novel slurry by employing the potassium ions to facilitate the MRR of silicon wafers, with excellent stability and dispersity for colloidal silica. Kim et al. [11] pointed out that the increase in rotation speed, down force, and back pressure potentially improve the MRR. They also demonstrated that the pad conditioning parameters further consolidated the MRR during polishing. Zhang et al. [12] found that the increasing frictional force between the sapphire substrate and the pad majorly improved the MRR. Another study conducted by Zhang et al. [13] confirmed that the oxidation behavior of chemical slurry determines the MRR efficiency. Both chemical and mechanical parameters determine the efficiency and planarization during polishing. Therefore, such parametric analyses of the processing mechanism provide practical identification guidance, helping engineers and researchers optimize the machining process.

Besides the polishing of semi-conductive materials, the toughening of advance structural ceramics, such as alumina and zirconia, is of key significance for industrial applications due to its high hardness, high strength, super temperature and erosion resistance, etc. However, the high brittleness induced by the ceramic polycrystalline structures leads to the lack of slip system, resulting in the appearance of micro-cracks around the surface [14]. When the surface is subjected to the impact load, catastrophic failure occurs. Therefore, investigations on toughening the ceramics have been conducted, such as weak interface ceramic system setup [15], composite and laminated ceramics fabrication [16,17], and nano ceramic and additive ceramic manufacturing [18,19]. Thus, accurate measurement of ceramic toughness is critical for determining the toughening results. Miyazaki et al. [20] conducted a single-edge V-notch plate experiments to successfully evaluate the fracture toughness of Al₂O₃, AlN, and Si₃N₄. The lengths of both the pre-notch and the crack are key factors to confirm the fracture toughness. Roy [21] exploited the crack opening displacement method via indentation cracks to evaluate the fracture toughness of sintered ZnO ceramics. The crack length during indentation is involved in calculating the toughness. D’Andrea [22] also acquired the elastic properties and fracture toughness of silicate bioactive glass-ceramics through nano-indentation and pointed out the tensile strength is affected by the flaw size by using fracture mechanics. Hence, all such toughness measurement methods rely on the critical parameters, such as crack length and flaw size, to efficiently describe the ceramic fracture-resistant behaviors.

Moreover, in mining practices, the tool life extension is one of the most imperative topics. The life of a tool is significantly affected by the cutter material. Polycrystalline diamond composites (PDC) refer to the tungsten carbide (WC) base coated by polycrystalline diamond, with high temperature and wear resistance [23]. Compared with the traditional WC cutters, the PDC coated mining cutters show a dramatically increased wear resistance. Myriad investigations have been conducted, focusing on how the PDC pick behaviors during cutting and affects the wear process. In drilling practices, the PDC drag cutter formed two processes: cutting and frictional contact, and the frictional force is the main source of the tool wear [24]. Rostamsowlat et al. [25] conducted a comprehensive series of experiments to demonstrate that the normal frictional force is closely related to the depth of the cut. Witt-Doerring et al. [26] experimentally demonstrated that the high wear rate is mainly caused by the high cutter temperature during drilling. More specifically, Glowka et al. [27] indicated that 350 °C is the threshold temperature leading to the cutter wear. Besides the temperature effects, Sinor et al. [28] found that the increment in the rotation speed in RPM (revolutions per minute) results in the acceleration of cutter wear. A prominent experimental report conducted by Yahiaoui et al. [29] found that the increased content of cobalt element in the cutter materials brings about the wear seriousness. The extensive investigations of affectation factors on PDC cutters in mining practices provide an efficient guidance for tool wear conditions, setting up a quantitative understanding of such rock drilling mechanisms.

In summary, parameter investigations in advanced material processing, could be exploited to explore the nature of such material mechanisms. Mathematical methods, such as gradient-based optimization, machine learning, deep learning, multiscale analysis, image processing, etc., can also be exerted in the corresponding investigations. Hence, the Special Issue focuses on a collection of review and original research articles relating to recent materials processing problems in all aspects of engineering practices, including ingenious and initiative applications.