The replacement of current petroleum-based plastics with sustainable alternatives is a crucial but formidable challenge for the modern society. Catalysis presents an enabling tool to facilitate the development of sustainable polymers. This review provides a system-level analysis of sustainable polymers and outlines key criteria with respect to the feedstocks the polymers are derived from, the manner in which the polymers are generated, and the end-of-use options. Specifically, we define sustainable polymers as a class of materials that are derived from renewable feedstocks and exhibit closed-loop life cycles. Among potential candidates, aliphatic polyesters and polycarbonates are promising materials due to their renewable resources and excellent biodegradability. The development of renewable monomers, the versatile synthetic routes to convert these monomers to polyesters and polycarbonate, and the different end-of-use options for these polymers are critically reviewed, with a focus on recent advances in c...

Catalysis as an Enabling Science for Sustainable Polymers

The multifunctional and advanced semiconductor titania with superior physicochemical and opto-electronic properties is extensively investigated in wastewater purification mainly due to its non-toxicity, favorable band edge positions, water insolubility, multifaceted electronic properties, surface acid–base properties, super hydrophilicity and so on. However, large band gap and massive photogenerated charge carrier recombination hinders its wide application under natural solar light. Thus, altering the surface-bulk structure of titania is a major goal in the area of both materials and environmental chemistry for its better applications. The substitution of p block elements (B, C, N, F, S, P, and I) either at Ti 4+ and O 2− sites is a promising approach to overcome the aforementioned drawbacks. This review focuses on the photocatalytic activity of non metal doped titania for a wide variety of pollutants degradation under UV/visible light, with special emphasis on nitrogen doped TiO 2 . Further improvement in photoactivity of N–TiO 2 is achieved via depositing with noble metals, co-doping with foreign ions, sensitization, surface modifications and heterostructuring with other semiconductors. The mechanism governing the photocatalytic reactions is discussed in the light of charge carrier generation–separation–transfer–recombination dynamics together with pollutant adsorption and their reactions with reactive oxygenated species in liquid or gaseous regime. We are positive that this review article will further stimulate our research interest on this intriguing hot topic.

A review on non metal ion doped titania for the photocatalytic degradation of organic pollutants under UV/solar light: Role of photogenerated charge carrier dynamics in enhancing the activity

Layered Machinable and Electrically Conductive Ti2AlC and Ti3AlC2 Ceramics: a Review

Heterogeneous catalysis is a promising technology for the valorization of renewable biomass to sustainable advanced fuels and fine chemicals. Porosity and nanostructure are the most versatile features of heterogeneous solid catalysts, which can greatly determine the accessibility of specific active sites, reaction mechanisms, and the selectivity of desirable products. Hence, the precise tuning of porosity and nanostructure has been a potential strategy towards developing novel solid catalysts with indispensable characteristics for efficient biomass valorization. Herein, we present a timely and comprehensive review of the recent advances in catalytic biomass conversions over microporous zeolites, mesoporous silicas, and nanostructured metals/metal oxides. This review covers the catalytic processing of both edible (lipids and starch) and non-edible (lignocellulose) biomass as well as their derived compounds, along with a systematic evaluation of catalyst reusability/kinetic/mechanistic aspects in the relevant processes. The key parameters essential for tailoring particle size, morphology, porosity, acid–base, and redox properties of solid catalysts are emphasized, while discussing the ensuing catalytic effects towards the selective conversion of biomass into desirable chemicals. Special attention has been drawn to understand the role of water in liquid phase biomass conversions as well as the hydrothermal stability and the deactivation of nanoporous catalysts. We believe this comprehensive review will provide new insights towards developing state-of-the-art solid catalysts with well-defined porosity and nanoscale properties for viable biomass conversion.

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Advances in porous and nanoscale catalysts for viable biomass conversion.

Tribocorrosion is an irreversible transformation of a material resulting from simultaneous physico-chemical and mechanical surface interactions in a tribological contact. Electrochemical methods are well suited for the study of tribocorrosion phenomena because they allow one to simulate the corrosive effect of the environment by imposing a fixed potential. Furthermore, the measurement of the anodic current permits one to determine the amount of material removed by oxidation as opposed to mechanical wear. In the present paper, experimental and theoretical aspects of applying electrochemical methods in tribology are discussed and recent results obtained with passivating metals in the authors' laboratory are presented. The importance of controlling the mechanical parameters and the contact geometry is stressed, and it is shown that these parameters can significantly affect the electrochemical response of a tribocorrosion system.

Electrochemical methods in tribocorrosion: a critical appraisal

To improve the tribological performance of sea frictional components, TiN and TiCN coatings, were used for surface protection of the components. The coatings were deposited on stainless steel and WC cemented carbides by arc ion plating. The coating topography was observed using scanning electron microscopy (SEM), and the composition and structure were analyzed by energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Hardness and adhesion force were tested by nanoindentation and scratch tester, respectively. The friction and wear properties of the TiN and TiCN coatings were investigated by ball-on-disk tribometer in air, distilled water and artificial seawater. The results showed that both the TiCN and TiN coatings had a strong (111) preferred orientation. The friction coefficients of the coatings in distilled water and artificial seawater were lower than those in air. This indicates the influence of aqueous solutions on the friction coefficient due to the lubricative film formed on the coatings. However, the wear loss of the coatings in artificial seawater was larger than those in air and distilled water, this demonstrates a positive synergism between corrosion and wear in artificial seawater. The TiCN coating shows the best wear resistance in the artificial seawater.

Jinlong Li

Papers

Tribological behaviours of PVD TiN and TiCN coatings in artificial seawater

Doping carbon to improve the tribological performance of CrN coatings in seawater

An analysis on tribological performance of CrCN coatings with different carbon contents in seawater

Structure, mechanical and tribological properties of self-toughening TiSiN/Ag multilayer coatings on Ti6Al4V prepared by arc ion plating

Improving tribological performance of CrN coatings in seawater by structure design