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• Energy-saving and environmentally friendly DC plasma sintering process. • Isothermal and non-isothermal sintering cycles from room to maximum temperature. • Comparison between commercial and in-house synthesized nano-TiO 2 powders. • Effect of sintering temperature on densification, phase content and grain growth. • Obtaining dense TiO 2 specimens in rapid sintering cycles. In this work, Plasma-Assisted Rapid Sintering (PARS), a pulsed DC plasma system in a hollow cathode regime, is presented as a novel technology to sinter nanoceramics. Nano-TiO 2 powders are used as proof of concept and submitted to thermal treatment using several PARS conditions and sintering schedules. PARS heating process induced solely by the hollow cathode effect is consistent and affordable, providing a homogeneous temperature distribution to the compact. Furthermore, the heating rate and the maximum temperature are easily tunable by the discharge current applied in the plasma source and can go safely from room to maximum temperature in a matter of seconds with heating speed comparable with other reported rapid sintering techniques. Using 1-min of non-isothermal PARS cycles up to 1000 °C, porous nanostructured samples were obtained; reaching 80 % relative density while the grains remained at the nanoscale. Adding dwell times, the relative density was increased up to 96 % using a temperature plateau for up to 10 min, but the TiO 2 grains grow intensively when temperatures exceeded 1000 °C. The results indicate that the developed process is a promising new alternative technology for sintering nanoceramics. [ABSTRACT FROM AUTHOR]

Consistent and concise literature about self-lubricating metallic composites containing MoS 2 is very scarce in particular those analyzing the possible reactions during processing, which are often neglected or even unknown in a variety of publications. In some situations, the composites present a poor lubricating behavior not related to environmental parameters or surface properties, but due to the simple fact that the solid lubricant added is not there anymore, i.e. it has reacted with the matrix or other additives. This review compiled publications from 1945 up to 2017 about the research developments in metal matrix self-lubricating composites containing MoS 2 . Information on the tribological properties of such composites according to the varied matrixes, contents, processing conditions, testing temperatures and atmospheres are presented. [ABSTRACT FROM AUTHOR]

Stoichiometric NiS shows two crystallographic phases, the low-temperature r-NiS and a high-temperature h-NiS – the later undergoes a first-order metal-to-semiconductor and paramagnetic-antiferromagnetic transition at the same temperature. Doping of nanostructured materials has gathered the attention of several researchers worldwide due to its effectiveness for adjusting the properties of materials. However, h-NiS doping reports in literature were performed mainly with samples not in nanocrystalline form. This paper describes a novel seed induced polyol synthesis of Pd doped h-NiS nanoparticles using sodium sulfide and thiourea as sulfur sources (for seeding and growing stages, respectively) at low temperatures (190 °C). The seed amounts allowed to produce well-dispersed, pure h-NiS nanoparticles with hexagonal habit – which was not possible without seeds at the same conditions. We suggest an effective diffusion of the Pd atoms through the h-NiS lattice via a substitutional-interstitial mechanism, thanks to the control and separation of the nucleation and growth processes during the syntheses. [ABSTRACT FROM AUTHOR]

• This work presents a novel high carbon yield process to synthesize 2D turbostratic graphite particles based on the solid-state reaction between carbide particles. • The carbon yield with the system B 4 C Cr 3 C 2 was ∼30 mol%. • The CDC particles obtained presented a porous nanostructured 2D turbostratic structure. • These particles have an excellent dispersibility in POE oil, opening a wide range of applications as a lubricant additive. • They are able to reduce friction and wear of metal-metal pairs under dry and oil-lubricated sliding conditions. In this work, a novel synthesis method of nanostructured carbon derived from carbides was developed. From phase diagram calculations, the boron and chromium carbides system was defined. The process developed consisted of the solid-state reaction between the carbides followed by a stage of chemical dissolution using hydrochloric acid. From this process, it was possible to recover practically all the carbon present in the system (∼15 wt.%) and a mechanism for the formation of nanostructure carbon during the reaction was proposed. The carbon produced by this method presented a 2D nanostructured turbostratic structure. As a result, they were able to reduce friction and wear of metal-metal pairs under dry and oil-lubricated sliding conditions. These particles also showed excellent dispersibility in the lubricant oil, opening a wide range of applications for this material as a lubricant additive. [Display omitted] [ABSTRACT FROM AUTHOR]