Influence of Sampling and Storage Protocol on Fractal Morphology of Soot Studied by Transmission Electron Microscopy

The aim of this work was to compare the fractal characteristics, D_f and k_f, the primary particle diameter, D_pp, the gyration diameter of aggregates, D_g, and the overlap coefficient, C_ov, of carbon nanoparticle aggregates produced by an ethylene diffusion flame and sampled by means of four commonly used techniques. The first method involves a thermophoretic piston probe (TPP) which inserts a TEM grid into the flame. Three other methods were applied at the outlet of a dilution device, also inserted in the flame. The first of these used a nuclepore filtration sampler (NFS), and is based on filtration of particles onto a polycarbonate membrane. The second, post dilution method, the insertion particle sampler (IPS), inserts a TEM grid, perpendicular to the aerosol flow. Similar to TPP, the last method is a thermophoretic particle sampler (TPS) sampling directly onto a TEM grid. After collection, the samples are stored in the dark either, (1) in a nitrogen filled cell at low humidity or, (2) in ambient air for studying atmospheric ageing. Good agreement was observed between TPP, TPS, and IPS indicating that the dilution induced for TPS and IPS does not significantly change the morphology of soot. On the other hand, the NFS protocol tended to overestimate the overlap coefficient and the size of primary particles and aggregates. Finally, with regard to the aging effect, we found that k_f and D_pp evolve slowly during storage in the atmosphere while D_f, was insensitive to the storage conditions. However, the overlap coefficient increased and the gyration diameter decreased as a function of storage duration, while storage under nitrogen tended to reduce these changes.     

Erosion of atmospheric plasma sprayed rare earth oxide coatings under air suspended corundum particles

Atmospheric plasma sprayed (APS) zirconium oxide based coatings are used widely in aero engine components for providing thermal insulation, improving the corrosion and oxidation resistance. Despite its wide spread industrial use, little is known about the basic erosion behaviour and the mechanisms by which such coatings erode. In this paper, the erosive wear behaviours of Yttria Stabilized Zirconia (YSZ) coatings; Lanthanum Zirconate (LZ) coatings and Inconel 738 base material (BM) were studied and compared under air jet erosion conditions with corundum particles as erodent material. The erosion behaviour was studied with respect to the different porosity volume percentages of the coatings and the changes in velocity of erodent, impact angle of erodent and erodent particle flux. It was found that in solid particle erosion, the wear resistances of YSZ and LZ coatings were the best at their lowest porosity volume and it decreased with the increase in the percentage volume of porosity. There was a linear increase in the wear resistance with the increase in hardness. Further, relationships among the erosion parameters with respect to erosive wear loss were derived by using the response surface methodology and the erosion mechanisms were discussed adequately.     

The PZT system (PbZr1-xTixO3, 0.0≤x≤1.0): Specific features of recrystallization sintering and microstructures of solid solutions (Part 1)

This work is concerned with the specific features of sintering of solid solutions of the PZT system (PbZr_1?xTi_xO₃, 0.0≤x≤1.0) depending on composition. The microstructure of the solid-solution ceramics has been found to be a fairly homogeneous, mosaic, sufficiently close packing of isometric crystallites with a range of section from 3 to 11 μm, but there exists a number of special features related to the component and phase composition of the objects. It has been found that the changes in multifractal parameters of grain structure of these ceramics reflect with high sensitivity the processes of phase transformations in the solid solutions. The obtained results are useful in developing piezoelectric materials based on the PZT system.     

Designing the morphology of ceria particles by precursor complexes

Ceria-based materials are widely used as catalysts, catalyst supports and electrolytes in many industrial applications. The morphological requirements of ceria particles vary depending on their applications. Here we show that complex morphologies of ceria particles can be achieved by using precursor complexes in the spray pyrolysis (SP) method. Three precursor complexes have been investigated: the complex of cerium acetate hydrate (CeA) and cerium nitrate hydrate (CeN); CeA and cerium ammonium nitrate (CeAN); and CeN and CeAN. Our results suggest that the morphological formation mechanism is highly correlated with the factors of precursor solubilities, solvent evaporation rates and precursor melting temperatures.     

The PZT system (PbTixZr1–xO3, 0≤x≤1.0): The real phase diagram of solid solutions (room temperature) (Part 2)

The sequence of phase transformations in the ceramic system PbTi_xZr_1?xO₃ (0≤x≤1.0) is determined and the real phase diagram of solid solutions is built. The observed periodicity of phase formation processes in the rhombohedral and tetragonal regions is explained by the real (defective) structure of PZT system ceramics, which is in many respects related to the variable valence of Ti ions and, as a result, to formation, accumulation, and ordering of point defects (oxygen vacancies) and their elimination by crystallographic shifts. The obtained results are useful in interpretation of the macroscopic properties of ceramics based on the PZT system.     

DRYING OF PADDY IN A BED DRYER

The experimental results of a bed dryer (at Ludhiana) have been analyzed. The experimental results are well predicted by the small scale laboratory experiments on a spouted bed dryer.     

Nanoindentation of nano-Al/Si3N4 multilayers with Vickers and Brinell indenters

The mechanical properties of ceramics films at the sub-micron, even nanometer length scale have attracted increased attention due to the high-speed development of microelectronic technology. In this work, nano-indentation hardness as a function of the different individual layer thickness has been measured and investigated in the sputtered Al/Si₃N₄ multilayers with different indenters (Vickers and Brinell). For this ceramics/metal multilayers system, the hardness of the multilayers increases with decreasing individual layer thickness from 500 nm to 100 nm and from 50 nm to 10 nm, indicating a significant size effect. At the same time, changes in the deformation behavior may be controlled by different deformation mechanisms for submicron scale and nanometer scale.     

DYNAMICS OF SEDIMENT-ASSOCIATED METALS IN A HIGHLY URBANISED CATCHMENT: BRADFORD, WEST YORKSHIRE

Urban watercourses are potential hazards because of their rapid flow changes, poor water quality and contaminated sediments. This study is a preliminary field investigation into fine sediment-associated metal contamination and its transport dynamics in a highly urbanised catchment in West Yorkshire, UK. Spatial and temporal changes in the concentration of channel-bed sediment-associated metals are investigated, and the fluxes of selected suspended sediment-associated metals, during an extreme high flow event, are determined. Channel-bed sediments were more contaminated at the most heavily urbanised sites. Data suggest that contaminated bed sediments could accumulate and possibly become increasingly contaminated between high-flow events, prior to being flushed from the system. Fluxes of contaminated suspended sediments were very high at the peak of the high flow event. The spatial and temporal dynamics of contaminated fine sediment which were identified in this study could inform planners with regard to future monitoring strategies.     

Effect of Deviation from Coaxiality between the Directions of Magnetization and Mechanical Strain on the Results of Magnetic Testing of Elastic Strain in Steels

The magnetoelastic effect in steels that are in the states of coercive force and residual magnetization in the saturation hysteresis loop is studied. The regularities of changes in the residual magnetization and coercive force under uniaxial tensioning and compression of specimens of 30KhGSA steel magnetized along the direction of strain application are established. It is shown that a variation in the direction of magnetization and complication of the strain pattern result in considerable deviations in the character of changes in the magnetic forces determined by a ferroprobe-type coercive force meter for elastically strained plates from St3 and R6M5 steels and for an St3 beam.