Sintering of Refractory Compound Nanocrystalline Powders. Part 1. Storage and Preliminary Heat Treatment of Titanium Nitride Nanocrystalline Powders

Several approaches are considered for storing and processing finely-dispersed oxygen-free refractory compound powders using the example of titanium nitride nanopowder. The change in composition of nanopowders protected by a surfactant and without protection from oxidation during storage in air, and also during processing in gas atmospheres (nitrogen, hydrogen) and in a vacuum is studied.     

Express method for determining the presence of defects of the surface of oxide-ceramic coatings

Using a multiresolution relevance function for the localization and subsequent segmentation of surface objects of oxide-ceramic coatings, we propose an express method for determining their number and sizes.     

Sintering of Refractory Compounds Nanocrystalline Powders. Part 2. Non-Isothermal Sintering of Titanium Nitride Powder

New approaches to the sintering of nanocrystalline powders of refractory compounds are proposed. Titanium nitride-based ceramics with a grain size of 50 nm and nanohardness 28.8 ± 2.47 GPa was obtained by sintering at a controlled rate of densification. Investigation of evolution of the block structure in the material during sintering enabled further optimization of the procedure and reduction of the sintering temperature to 1150°C.     

Spark plasma sintering of TiCN nanopowders in non-linear heating and loading regimes

Consolidation of commercially available nanostructured titanium carbonitride (TiCN) powder has been performed by Spark Plasma Sintering (SPS) in the temperature range from 1300 to 1600 °C. The effect of non-linear heating and loading regimes on consolidation of high melting point nanocomposites has been investigated. SPS consolidated TiCN material has demonstrated near fully dense and fine homogeneous microstructure with average grains size about 150 nm. Nanohardness and fracture toughness of the TiCN nanocomposite have been measured as 33 ± 0.9 GPa and 3.2 MPa m^1/2 respectively.     

The mineralogy of bauxite for producing smelter-grade alumina

Aluminum-producing companies rely on low-cost, high-purity, smelter-grade alumina (aluminum oxide), and alumina production utilizes the bulk of bauxites mined world-wide. The mineralogy of the bauxites has a significant impact on the operation of the Bayer process for alumina production. Typically, the Bayer process produces smelter-grade alumina of 99.5% Al₂O₃, starting from bauxite containing 30% to 60% Al₂O₃. The main objective of the Bayer process is to extract the maximum amount of aluminum from the bauxite at as high an aluminate concentration in solution as possible, while limiting any troublesome side reactions. Only with a better understanding of the chemistry of the mineral species and a strict control of the operating/processing conditions can the Bayer process produce efficiently, a low cost, high-quality alumina with minimum detrimental environmental impact. For more information, contact M. Authier-Martin, Raw Materials R&D, Arvida Research and Development Centre, Alcan International Limited, Jonquiere, Quebec, Canada G7S 4K8; monique.authier@alcan.com.     

Index of environmental awareness through the MIMIC approach

This paper addresses the issue of environmental awareness in the regions of the Russian Federation. For this purpose, an index of environmental awareness at regional level is derived as a latent variable from various categories of search entries in Yandex, the prominent Russian search engine, during two periods in the years 2014 and 2015. The frequency of these search requests presumably depends on certain economic and socio-economic causes, which are integrated into the model for further investigation. The relation between regional wealth and environmental awareness is thereby of particular interest. The multiple indicators-multiple (MIMIC) causes model allows us to estimate an index of environmental awareness and to rank the Russian regions according to this index.     

Sintering of Refractory Compounds Nanocrystalline Powders. Part 2. Non-Isothermal Sintering of Titanium Nitride Powder

New approaches to the sintering of nanocrystalline powders of refractory compounds are proposed. Titanium nitride-based ceramics with a grain size of 50 nm and nanohardness 28.8 ± 2.47 GPa was obtained by sintering at a controlled rate of densification. Investigation of evolution of the block structure in the material during sintering enabled further optimization of the procedure and reduction of the sintering temperature to 1150°C.