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Diamond-like amorphous carbon (DLC) coatings are promising materials for tribological applications and tremendous efforts have been devoted to improving their tribological properties under various environments and conditions. Nevertheless, the buried nature of the tribological interface makes it difficult to monitor interfacial phenomena and structures in situ, thereby hindering the understanding of the underlying microscopic mechanisms. Atomistic simulations such as molecular dynamics and first-principles calculations are highly effective to model tribological processes occurring at the nanoscale. This article reviews results of atomistic simulations that have revealed tribochemical reactions of lubricants with solid surfaces and detailed mechanisms underlying superlubricity and wear of DLC coatings in boundary lubrication.

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This article presents the author’s academic background and research activities, focusing on tribological studies using atomic force microscopy (AFM) and neutron reflectometry. The research aims to elucidate lubrication mechanisms from nano- to macroscale, in particular the dynamic behaviour of additive-derived films at sliding interfaces. AFM has been used to visualise the formation, thickness and mechanical response of interfacial films, while environmental factors such as humidity and dissolved gases have been controlled to elucidate their influence on film formation. In addition, an operando system combining a narrow gap sliding tribometer with neutron reflectometry was used to evaluate changes in film thickness and density under shear conditions. Neutron reflectometry was also used to investigate the interactions and competitive mechanisms between different lubricant additives, including polymer-based additives, fatty acids and ZDDP, under different thermal conditions. These results contribute to a better understanding of interfacial phenomena and provide valuable insights for the design of high performance, environmentally friendly lubricants. The article also discusses the author’s educational philosophy, which emphasises the importance of developing independent thinking and perseverance through research activities during the student years. The author believes that such experiences not only cultivate fundamental research skills, but also shape the resilience and mindset essential for future challenges in diverse career fields.

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Tapered roller bearings are designed to support loads even on the sliding contact surface, which is why they generate more heat and torque than other rolling bearing. The bearing generates heat, which causes the bearing and surrounding parts to expand. Generally, tapered roller bearing is used with a fixed position preload, so this thermal expansion causes the amount of preload to change during the operation. This change in preload can result in the fatigue life of the bearing being shorter than the design life, so accurate prediction of preload changes is required, for example, by FEM analysis. Moreover, one effective method for reducing the heat generation is to provide grooves on the end surface of the roller.

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This article reflects on the 12-year journey (2013-2025) of Takumi Ishikawa in the field of tribology. His career is divided into two major phases: six formative years as a student and six subsequent years as a university faculty member. During his student years, his research primarily focused on the frictional behavior of hydrogenated amorphous carbon (a-C:H) films. As a faculty member at Tottori University, he shifted his focus to the investigation of surface forces and their role in interfacial phenomena. The article also explores the motivations that led him to pursue an academic path, including influential experiences during his master’s and doctoral studies, as well as pivotal moments that shaped his identity as a researcher. This retrospective aims to provide an overview of the author’s research and to offer insights that may be of value to those involved in the field of tribology.

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In this article, the author reflected on his student days and introduced the background circumstances that led to his enrollment in a doctoral program. The research conducted during the doctoral studies, which focused on developing a diagnosis technique for deterioration of lubricating oil by the membrane patch color, was also introduced. In addition, the research currently being carried out at the University of Fukui was presented. This article was intended to provide useful information for those who are considering pursuing a doctoral program in their academic careers.

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This paper introduces the author’s research on polymer tribology, conducted in various environments, including biological and hydrogen gas environments. Initially, some results related to the tribological behavior of natural and artificial joints are presented. This research focused on synovial constituents, biological molecules such as proteins, hyaluronic acid, and phospholipids. As a result, proteins showed a dominant effect on the friction and wear properties of artificial materials. However, other molecules also showed a synergistic effect; for instance, a mixture of hyaluronic acid and phospholipids induced the lowest friction coefficient between hydrogel and glass sliding pairs. In the next section, the current research work, tribological experiments in high-purity hydrogen gas, are presented. Through the evaluation, the differences of transfer film composition were observed by hydrogen gas pressure. These differences were thought to cause due to metal surface reduction by hydrogen gas, which induced different frictional behavior.

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This paper reviews research conducted during the author’s graduate studies on the development of carbon-based materials. The work includes studies on the tribological properties of doped diamond-like carbon (DLC) coatings at high temperatures, as well as the synthesis and structural characterization of one-dimensional SWCNT-BNNT heteronanotubes. A key focus was the continuous deposition of boron- and chromium-co-doped DLC coatings using a filtered cathodic vacuum arc (FCVA) system, followed by systematic ball-on-disk friction testing. These tests elucidated the mechanisms responsible for achieving an ultralow friction coefficient of 0.02 and high wear resistance at 300 °C. In parallel, the synthesis of SWCNT-BNNT heteronanotubes on TEM grids demonstrated that increasing the precursor concentration improved BNNT growth efficiency. A quantitative evaluation approach was established by combining TEM-based statistical analysis with Raman mapping. Furthermore, this review outlines a research proposal aimed at enhancing the oxidation resistance of DLC coatings through the integration of low-dimensional carbon materials. Lastly, based on the author’s cumulative research experience, suggestions are provided for senior students pursuing doctoral-level studies in this field.

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Scraping texturing has been applied to slide guideways of machine tools and is effective in preventing adhesion between sliding surfaces. In recent years, it has been revealed that the use of lubricating oil with acid phosphate ester additives that exhibit high viscosity in the surface layer can convert solid friction in the mixed and boundary lubrication regimes to fluid friction. In this study, the scraped texture was modeled by sum of taper-land-taper bearings (TLTB) and adjacent land surfaces, and the friction coefficient and flying height were theoretically analyzed using a pressure solution of the one-dimensional modified Reynolds equation that includes the effects of high-viscosity surface layer. It was shown that by appropriately selecting the geometrical dimensions of the TLTB and the three parameters for the high-viscosity layer, the friction coefficient and flying height for lubricant B with a viscosity of 0.1 Pa･s can be theoretically obtained in the wide region of the sliding velocity. The friction characteristics for lubricant E with a viscosity of 0.03 Pa･s agreed with the calculated result when the ratio of the viscosity at the solid surface to the base viscosity is assumed to be constant. Furthermore, the calculated friction coefficient when the load pressure was doubled was found in good agreement with the experimental value.

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本会記事，次号予告，特集号企画主旨，コーヒーブレイク

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