The key way of achieving sustainability of a product is to design a manufacturing process that increases the mechanical properties of traditional materials, e.g. steel, whilst also increasing processing efficiency, and diminishing energy consumption. A novel process has been developed that allows for a traditional spring steel (60Si2Mn) to be produced with a high level of strength (tensile strength is over 2100 MPa, bending strength is 4100 MPa, yield strength is 1700 MPa as well as hardness of 59 HRC), also retaining reasonable ductility on an industrial scale. It is shown that a triple-phase microstructure comprising lenticular prior martensite, nano-scaled needle/lath-like bainitic ferrite and film retained austenite, is obtained. The excellent combination of strength and ductility is attributed to a synergistic multi-phase strengthening effect. The nano-scaled structure exhibits a good balance between strength and toughness. The presence of prior martensite provides the kinetics of subsequent nano-scaled bainitic transformation by bainitic laths nucleating at the martensite-austenite interfaces. This design methodology potentially broadens the application of spring steel to components that experience more demanding service environments, such as heavy loads.

In this research, a one-step hydrothermal method is used to prepare Cu-doped, N-doped and Cu/N co-doped titanium dioxide (TiO 2 ) composites, and the doping effects on the structures, absorption and photocatalytic performance are investigated. All the products are in anatase structure. The substitution of Cu atoms in TiO 2 and distribution of N in the crystal lattice have been identified by X-ray diffraction, which lead to the decrease of grain size. Hollow micro-nanospheres of Cu-TiO 2 samples, which make them have strong dark adsorption properties, can be observed. Cu/N co-doped samples exhibit the maximum light absorption in the visible light region, and a red-shift which is responsible for narrow band gap energy owing to the presence of N-atoms and Cu-atoms in the TiO 2 lattice. The synergistic effect of Cu and N results in the enhanced photocatalytic activity for degradation of methyl orange under visible light irradiation.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

In this work, an one-step solvothermal synthesis method is used to prepare TiO2-reduced graphene oxide (RGO)-CuO/Fe2O3 ternary composite photocatalysts with TiO2 and CuO/Fe2O3 nanoparticles coated RGO, while the structures and photocatalytic performance of these synthesized ternary composite photocatalysts are studied. It is found that Cu2+ and Fe3+ are substituted for Ti4+ into the crystal lattice of anatase TiO2 in these prepared ternary composite photocatalysts. TiO2 and CuO/Fe2O3 nanoparticles are uniformly coated on the surface of RGO and closely contact with each other. The Cu/Fe doping has obviously improved the absorption ability on the visible light, and the bandgap of the ternary composite can be reduced. Under visible light irradiation, by increasing the Cu/Fe doping amount, the photocatalytic performance can be improved until the Cu and Fe contents reached 0.075 wt.% and 0.1 wt.%, respectively. The prepared products can be reused for eight cycles to degrade the methyl orange solution, and it retains over 93% photocatalytic efficiency.

In(OH) 3 /InOOH nanocrystals are synthesized using InCl 3 •4H 2 O as the indium source in the presence of ethylenediamine by a one-step hydrothermal process, and the e ect of synthesis temperature on the morphology, crystallization, structure, and photocatalytic properties of the photocatalysts is investigated. The results show that all the synthesized In(OH) 3 /InOOH samples have granular nanoparticles with a size of 20-30 nm. When the synthesis temperature is lower than 150°C, only the In(OH) 3 phase exists. With increasing synthesis temperature, In(OH) 3 gradually dehydrates to form InOOH to achieve a phase equilibrium between InOOH and In(OH) 3 . The concentration of InOOH is the maximum at 180°C and decreases at 210°C. The photocatalytic activity is evaluated from the degradation of a Rhodamine B solution under ultraviolet light irradiation, which follows the rst-order reaction kinetics. The increase in synthesis temperature can signi cantly improve the photocatalytic performance of In(OH) 3 /InOOH because of the formation of a large number of natural heterojunctions in the nanocrystals, which can enhance ultraviolet light absorption and facilitate charge transfer and separation. The rst-order kinetic constant of the nanocrystals synthesized at 180°C is almost 2.5 times that of the nanocrystals synthesized at 150°C. The active species capture experiments demonstrate that holes and superoxide radicals are the main active species in the photocatalytic systems.

A disc spring, also known as a Belleville spring, is a conical shell which can be loaded along its axis either statically or dynamically. It can generate a high force in a very short spring length with minimal movement when compressed. A novel multi-step austempering heat treatment process is developed to improve both the hardness and strength of a conventional 60Si2Mn disc spring. In this case, the disc spring is austenitized at 900°C for 0.5 h, control-quenched to a temperature below Ms (the starting temperature of martensite transformation) for a very short time, subsequently heated to the Ms point and holding for a specific time, and finally air cooled to the room temperature. It is found that the resulting multiphase microstructure consists mainly of prior lenticular martensite formed during controlled quenching (PM), needle bainitic ferrite (BF), and high carbon enriched retained austenite (RA). Further observation shows that a nanostructured (BF+RA)nano phase including lath BF and film RA with a width of about 100 nm nucleates around the PM. Such a microstructure results in uniform compression behavior, and significantly higher strength and hardness than for a conventional 60Si2Mn disc spring. This controlled multi-step austempering process is a promising solution for enhancing the disc spring properties for those applications involving higher loading and fatigue conditions.