Grain Size Distribution Of Material Research Articles

Statistical Analysis of Histograms of Grain Size Distribution in Nanostructured Materials Processed by Severe Plastic Deformation

Analysis of histograms of grain size distribution of materials nanostructured by severe plastic deformation has been carried out using statistical analysis methods. It has been established that in materials with quite homogeneous nanostructure, the fitting of histograms of grain size distribution by using a logarithmic standard distribution is not accurate enough. It is proposed to compensate for the observed imprecision by including into the model the additional component – normal distribution. It is shown that this approach is applicable to nanostructured materials with both the deformation-origin nanostructure and the grain structure formed during annealing.

The Elovich equation as a predictor of lead and cadmium sorption rates on contaminant barrier minerals

Contaminant sorption reactions in soils are generally heterogeneous, multi-steps solid–liquid reactions that compliment transport processes. For contaminant barrier materials, reaction heterogeneity is promoted by variability in the mineralogy and grain size distribution of materials required in mix proportions to satisfy various design functions. The adsorption/desorption of contaminants in barrier systems is necessary for performance assessments. In this paper, the sorption/desorption rates of Pb2+ and Cd2+ on Na-montmorillonite ((OH)4Si8Al4O20nH2ONa) and kaolinite ((OH)8Si4Al4O10) were investigated by varying nature of aqueous contaminants and clay. Heavy metals including Pb2+ and Cd2+ were adsorbed/desorbed on the clays at pH levels of 2, 3, 4, and 7 for 48h. Sorption/desorption of these heavy metals was found to be influenced by point of zero charge, cation exchange capacity, particle size, pH of the system, complexation of metals, and hydrated ionic radius of metals. As a result, Elovich equation was found to adequately explain the kinetics of Pb2+ and Cd2+ on two clay minerals with the squared correlation coefficients (R2) that range from 0.70 to 0.99. At pH 2, removal rate were 36.3% for Pb2+ and 64.5% for Cd2+ from Na-montmorillonite while 67.1% for Pb2+ and 75.0% Cd2+ from kaolinite, respectively. The results obtained from the Elovich equation could be useful for assessing the sorption equilibrium for the metals potentially attained in soil barrier systems.

The Effect of Grain Size Distribution on the Mechanical Properties of Nanometals

Predicting the properties of a material from knowledge of the internal microstructures is attracting significant interest in the fields of materials design and engineering. The most commonly used expression, known as Hall-Petch Relationship (HPR), reports on the relationship between the flow stress and the average grain size. However, there is much evidence that other statistical information that the grain size distribution in materials may have significant impact on the mechanical properties. These could even be more pronounced in the case of grains of the nanometer size, where the HPR is no longer valid and the Reverse-HPR is more applicable. This paper proposes a statistical model for the relationship between flow stress and grain size distribution. The model considered different deformation mechanisms and was used to predict mechanical properties of aluminium and copper. The results obtained with the model shows that the dispersion of grain size distribution plays an important role in the design of desirable mechanical properties. In particular, it was found that that the dependence of a material’s mechanical properties on grain size dispersion also follows the HPR to Inverse-HPR type of behaviour. The results also show that copper is more sensitive to changes in grain size distribution than aluminium.

Grain Growth in Nanocrystalline Nickel

AbstractIn this study, the effect of grain size distribution on the thermal stability of electrodeposited nanocrystalline nickel was investigated by pre-annealing material such that a limited amount of abnormal grain growth was introduced. This work was done in an effort to understand the previously reported, unexpected effect, of increasing thermal stability with decreasing grain size seen in some nanocrystalline systems. Pre-annealing produced a range of grain size distributions in materials with relatively unchanged crystallographic texture and total solute content. Subsequent thermal analysis of the pre-annealed samples by differential scanning calorimetry showed that the activation energy of further grain growth was unchanged from the as-deposited nanocrystalline nickel.