The reach of tribology has expanded in diverse fields and tribology related research activities have seen immense growth during the last decade. This review takes stock of the recent advances in research pertaining to different aspects of tribology within the last 2 to 3 years. Different aspects of tribology that have been reviewed including lubrication, wear and surface engineering, biotribology, high temperature tribology, and computational tribology. This review attempts to highlight recent research and also presents future outlook pertaining to these aspects. It may however be noted that there are limitations of this review. One of the most important of these is that tribology being a highly multidisciplinary field, the research results are widely spread across various disciplines and there can be omissions because of this. Secondly, the topics dealt with in the field of tribology include only some of the salient topics (such as lubrication, wear, surface engineering, biotribology, high temperature tribology, and computational tribology) but there are many more aspects of tribology that have not been covered in this review. Despite these limitations it is hoped that such a review will bring the most recent salient research in focus and will be beneficial for the growing community of tribology researchers.

China is the largest mercury emitter in the world and coal combustion is the most important mercury source in China. This paper updates the coal quality database of China and evaluates the mercury removal efficiency of air pollution control devices (APCDs) based on 112 on-site measurements. A submodel was developed to address the relationship of mercury emission factor to the chlorine content of coal. The mercury emissions from coal-fired power plants (CFPPs) in China were estimated using deterministic mercury emission factor model, nonchlorine-based and chlorine-based probabilistic emission factor models, respectively. The national mercury emission from CFPPs in 2008 was calculated to be 113.3 t using the deterministic model. The nonchlorine-based probabilistic emission factor model, which addresses the log-normal distribution of the mercury content of coal, estimates that the mercury emission from CFPPs is 96.5 t (P50), with a confidence interval of 57.3 t (P10) to 183.0 t (P90). The best estimate by the chlorine-based probabilistic emission factor model is 102.5 t, with a confidence interval of 71.7 to 162.1 t. The chlorine-based model addresses the influence of chlorine and reduces the uncertainties of mercury emission estimates.

Abstract. China is the largest anthropogenic mercury emitter in the world, where primary nonferrous metal smelting is regarded as one of the most significant emission sources. In this study, atmospheric mercury emissions from primary zinc, lead and copper smelters in China between 2000–2010 were estimated using a technology-based methodology with comprehensive consideration of mercury concentration in concentrates, smelting processes, mercury removal efficiencies of air pollution control devices (APCDs) and the application percentage of a certain type of APCD combinations. Our study indicated that atmospheric mercury emissions from nonferrous metal smelters in 2000, 2003, 2005, 2007 and 2010 were 67.6, 100.1, 86.7, 80.6 and 72.5 t, respectively. In 2010, the amounts of mercury emitted into atmosphere were 39.4 ± 31.5, 30.6 ± 29.1, and 2.5 ± 1.1 t from primary zinc, lead and copper smelters, respectively. The largest amount of mercury was emitted from the Gansu province, followed by Henan, Yunnan, Hunan, Inner Mongolia and Shaanxi provinces. Hg2+, Hg0 and Hgp emissions from zinc smelters were 25.6, 11.8 and 1.97 t, respectively. The emissions percentages of Hg2+ and Hg0 were almost the same from lead and copper smelters. The average mercury removal efficiency was 90.5 ± 52.5%, 71.2 ± 63.7% and 91.8 ± 40.7% in zinc, lead, and copper smelters, respectively.

Intelligent self-assembly of nanobuilding blocks during the formation of Ni(OH)(2) single crystals with concave polyhedron structure was studied. The nickel hydroxide nanoplates pile up together with the aid of hydrazine molecules and grow along the [001] direction to form the brand-new geometry of concave polyhedrons. The novel nanostructure looks like a regularly twisted triangular prism wringed smoothly in the middle and could be attributed to the inherent spatial asymmetry of the nickel hydroxide crystal structure and the hydrogen bonds linked with the added hydrazine molecules. On the basis of the putative mechanism, polyhedrons with different longitudinal sizes (0.3-1 mum) were synthesized by adjusting the quantities of hydrazine. We also obtained NiO polyhedron crystals with similarly piled plates by calcinations of the Ni(OH)(2) polyhedrons. Our preliminary electrochemical experiments show that the Ni(OH)(2) polyhedrons have potential applications in electrochemical storage.

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Gecko adhesion has inspired the fabrication of various dry adhesive surfaces, most of which are developed to be used under atmospheric conditions. However, applications of gecko-inspired surfaces can be expanded to vacuum and even space environment due to the characteristics of van der Waals interactions, which are always present between materials regardless of the surrounding environment. In this paper, a controllable, anisotropic dry adhesion in vacuum is demonstrated with gecko-inspired wedged dry adhesive surfaces fabricated using an ultraprecision diamond cutting mold. The adhesion and friction properties of the wedge-structured surfaces are systematically characterized in loading-pulling mode and loading-dragging-pulling mode. The surfaces show significant anisotropic adhesion (P ad ≈ 10.5 kPa vs P ad ≈ 0.7 kPa) and friction (P f ≈ 50 kPa vs P f ≈ 30 kPa) when actuated in gripping and releasing direction, respectively. The wedge-structured surfaces in vacuum show comparable properties as exposed in atmosphere. A three-legged gripper is designed to pick up, hold, and release a patterned silicon wafer in vacuum. The study demonstrates a green, high-yield, and low-cost method to fabricate a reliable and durable mold for gecko inspired anisotropic dry adhesive surfaces and the potential application of dry adhesive surface in vacuum.

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Gecko-inspired surfaces are smart dry adhesive surfaces that have attracted much attention because of their wide range of potential applications. However, strong frictional force, rather than adhesive force, is frequently targeted in most of research in this area. In this study, the interfacial adhesive and frictional properties of a gecko-inspired mushroom-shaped polyurethane pillar array surface have been systematically characterized to design and control the interfacial adhesion of the surface by considering the nanoscale interfacial adhesion, the microscale structural compliance and deformation, and the macro-scale actuation. Matching the movement of the leg springs and the interfacial adhesive characteristics between the pillar array surfaces and substrates, a three-legged clamp prototype has been designed and fabricated to successfully pick up and release light and fragile objects with a smooth upper surface, such as a silicon wafer. These results provide a new insight into not only the theoretical understanding of the integrating adhesion mechanisms, but also the practical applications of utilizing and controlling the adhesive and frictional forces of gecko-inspired surfaces.