Insight into Debye Hückel length (κ−1): smart gravimetric and swelling techniques reveals discrepancy of diffuse double layer theory at high ionic concentrations

Smart gravimetric and swelling techniques were utilized in this work to examine the validity of the Debye Hückel length (κ−1) equation when shale interacts with highly concentrated salt solutions. The swelling and shrinkage behavior of two different shales, when exposed to monovalent and divalent ionic solutions (NaCl, KCl and CaCl2) at concentrations ranging from 2 to 22%w/w was observed and measured. Shale swelling and shrinkage results show that Debye Hückel length (κ−1) equation seems to work adequately at low ionic concentrations where osmotic water flow out of shale plays a major role in decreasing the diffuse double layer thickness by withdrawing water out and thereby shrinking κ−1. At high ionic concentration levels, the flow of associated water into the diffuse double layer negates the withdrawal of osmotic water out of the diffuse double layer which could maintain κ−1 or possibly increase it. Data on measured ionic uptake into shale suggests that excessive ionic diffusion into shale, especially at high concentrations, leads to higher electrical repulsion between alike ions in the diffuse layer which could lead to the expansion of the diffuse double layer thickness. Furthermore, swelling and shrinkage data analysis for shale suggests the existence of a ‘critical concentration’ below which the Debye Hückel length equation works. Above the critical concentration, the validity of the Debye Hückel length equation might be in question. The critical concentration is different for all ions and depends on ionic valence, hydrated ion diameter, and clay type.

A Review on Terrazyme as Pavement Enhancement Approach

During construction, Engineers often face difficulty related to the stability of soil with or on which the structure is being constructed as the unstable soil cannot not withstand the loads imposed over it. Since the layers of pavements distributes the load evenly over the subgrade, the design of pavement layer is very much dependent on the strength of the subgrade soil over which they are to be laid. So, there is an urgent need to improve the properties of subgrade. An effort to treat the earth with an enzyme that proves very much advantageous for engineering purposes. It is a natural solution which is generated by the enzymatic action on fruits, edibles, saccharine and water by means of fermentation. In this research, a bio-enzyme labelled as Terrazyme is being utilized that significantly improves the properties of soil. Terrazyme being cost effective, efficient, non-toxic, non-inflammable increases the stability by accelerating the enzymatic reactions between the argil and cations(organic) and accelerates the cationic interchange operation to lower down the diffused double layer thickness. The paper deals with all the information about terrazyme including its working mechanism and different properties of soil. It has been investigated that on incrementing the dosage of terrazyme in test sample, notable improvement in the value of UCS and CBR value of soil is observed.

Enhanced Magnetoelectric Coupling in BaTiO3-BiFeO3 Multilayers—An Interface Effect

Combining various (multi-)ferroic materials into heterostructures is a promising route to enhance their inherent properties, such as the magnetoelectric coupling in BiFeO3 thin films. We have previously reported on the up-to-tenfold increase of the magnetoelectric voltage coefficient α ME in BaTiO3-BiFeO3 multilayers relative to BiFeO3 single layers. Unraveling the origin and mechanism of this enhanced effect is a prerequisite to designing new materials for the application of magnetoelectric devices. By careful variations in the multilayer design we now present an evaluation of the influences of the BaTiO3-BiFeO3 thickness ratio, oxygen pressure during deposition, and double layer thickness. Our findings suggest an interface driven effect at the core of the magnetoelectric coupling effect in our multilayers superimposed on the inherent magnetoelectric coupling of BiFeO3 thin films, which leads to a giant α ME coefficient of 480 Vc m − 1 Oe − 1 for a 16 × (BaTiO3-BiFeO3) superlattice with a 4.8 nm double layer periodicity.