Influence Of Chemical Heterogeneity Research Articles

Lead-Free BiFeO3-Based Piezoelectrics: A Review of Controversial Issues and Current Research State.

Lead-free electroceramics represent an emerging area of research that has the potential to enable new green advances in electronics. Research has mainly focused on the development of new piezoelectric materials for replacing lead containing oxides exhibiting superior electromechanical behavior. Lead-free BiFeO3-based materials are not only the promising candidates to replace lead-based materials but also show intriguing properties which may inspire innovative material design for the next generation of lead-free piezoceramics. This review aims to highlight the current state of research and overlooked aspects in lead-free BiFeO3-based ceramics, which could be insightful in elucidating certain controversial issues. Current strategies to reduce high conductivity, influence of chemical heterogeneity on both functional properties and crystal structure, effective heat treatment procedures, and the role of pseudo-cubic structures on the enhancement of piezoelectric properties are subjects of highlighted within this review as they have a significant impact on the quality of BiFeO3-based lead-free piezoelectrics (but are often disregarded).

Identifying nonadditive contributions to the hydrophobicity of chemically heterogeneous surfaces via dual-loop active learning.

Hydrophobic interactions drive numerous biological and synthetic processes. The materials used in these processes often possess chemically heterogeneous surfaces that are characterized by diverse chemical groups positioned in close proximity at the nanoscale; examples include functionalized nanomaterials and biomolecules, such as proteins and peptides. Nonadditive contributions to the hydrophobicity of such surfaces depend on the chemical identities and spatial patterns of polar and nonpolar groups in ways that remain poorly understood. Here, we develop a dual-loop active learning framework that combines a fast reduced-accuracy method (a convolutional neural network) with a slow higher-accuracy method (molecular dynamics simulations with enhanced sampling) to efficiently predict the hydration free energy, a thermodynamic descriptor of hydrophobicity, for nearly 200 000 chemically heterogeneous self-assembled monolayers (SAMs). Analysis of this dataset reveals that SAMs with distinct polar groups exhibit substantial variations in hydrophobicity as a function of their composition and patterning, but the clustering of nonpolar groups is a common signature of highly hydrophobic patterns. Further molecular dynamics analysis relates such clustering to the perturbation of interfacial water structure. These results provide new insight into the influence of chemical heterogeneity on hydrophobicity via quantitative analysis of a large set of surfaces, enabled by the active learning approach.

Influence of chemical heterogeneity and microstructure on the corrosion resistance of biodegradable WE43 magnesium alloys.

Magnesium-yttrium-rare earth element alloys such as WE43 are potential candidates for future bioabsorbable orthopedic implant materials due to their biocompatibility, mechanical properties similar to human bone, and the ability to completely degrade in vivo. Unfortunately, the high corrosion rate of WE43 Mg alloys in physiological environments and subsequent loss of structural integrity limit the wide applications of these materials. In this study, the effect of chemical heterogeneity and microstructure on the corrosion resistance of two alloys with different metallurgical states was investigated: cast (as in traditional preparation) and as-deposited produced by magnetron sputtering. The corrosion behavior was studied by potentiodynamic polarization and electrochemical impedance spectroscopy tests in blood bank buffered saline solution. It was found that the as-deposited alloy showed more than one order of magnitude reduction in corrosion current density compared to the cast alloy, owing to the elimination of micro-galvanic coupling between the Mg matrix and the precipitates. The microstructure and formation mechanism of corrosion products formed on both alloys were discussed based on immersion tests and direct measurements of X-ray photoelectron spectrometry (XPS) and cross-sectional transmission electron microscopy (TEM) analysis.

The influence of chemical heterogeneities on the local mechanical behavior of a high-entropy alloy: A micropillar compression study

The effect of the chemical inhomogeneities on the local mechanical behavior was studied in a CoCrFeMnNi high-entropy alloy. Micropillar compression revealed that, despite the difference in the chemical composition, the stress-strain behaviors in the two regions were almost identical. The size effect was negligible in the micropillar compression experiments.

Influence of Chemical Heterogeneity and Nanoscale Roughness on the DLVO Energy Interaction by Spherical Coordinates

In this work, the influence of chemical heterogeneity on the stability of nanocolloidal systems is surveyed with a new method. Zone of influence as a very important parameter for chemical patch surveying is modeled for sphere and flat surface. Surface chemical heterogeneity with specified properties, size, and position are created by spherical coordinate integration method. Rippled sphere model is used to create roughness and the flat surface is created by changing two sphere radius ratio. Using the spherical coordinate system for modeling of surface roughness and chemical heterogeneity is very accurate and fast. Results show that the patches could destabilize the colloidal system at very small sizes. Surface roughness reduces the effect of chemical patches for destabilizing the colloidal system, and with increasing the size of roughness the total DLVO energy interaction increases.

The influence of chemical heterogeneity among cloud drop populations on processing of chemical species in winter clouds

Drop size-resolved measurements of winter cloud composition in the Rocky Mountains of northern Colorado revealed significant variations of cloud drop pH, ion (SO 4 2−, NO 3 −, NH 4 +, and Ca 2+) concentrations, and concentrations of trace metal catalysts (Fe and Mn) with drop size. Simultaneous measurements of snow chemical composition and the degree of cloud drop capture by snow crystals (riming) revealed a positive correlation between snow composition and the extent of ice crystal riming in two of four cases studied. Observations indicate that the size-dependent chemical composition of the clouds tends to enhance aqueous phase sulfate production rates when the primary oxidant is ozone. Enrichment of accumulation mode aerosol species in small cloud drops, which are inefficiently scavenged by ice crystals, appears to cause small (typically less than 15%) reductions in the efficiency with which these species are scavenged by precipitation during accretional ice crystal growth.

Influence of chemical heterogeneity on structure and properties of emulsion copolymers

AbstractWhen comonomers of different hydrophilicity are copolymerized in emulsion polymerization, a heterogeneous distribution of the polar groups in the resulting latex can occur which is mainly caused by differences in the solubilities of the monomers as well as the polymerization products in the water and the polymer phase. By a combination of various methods, analytical ultracentrifugation of the latices, mechanical spectroscopy, tensile tests and electron microscopy of the latex films, the distribution of the polar groups in the latex, the structure of the latex particles, and the morphology and mechanical behaviour of the latex films have been studied. Films of emulsion copolymers in many cases show a very pronounced two‐phase morphology consisting of the main polymer within the particles and a second hard phase which is concentrated in the interfaces and wedges between the original particles, forming a honeycomb‐like continuous structure throughout the film which has a strong influence on the mechanical properties of the films. When emulsion copolymers are cross‐linked via reactive monomers with a higher degree of hydrophilicity than the main monomers, structurized networks may result with a spatially inhomogeneous distribution of cross‐links. Structure and properties of films from emulsion copolymers are determined by the polymer bulk properties as well as the multiphase structure.

Tensiometric studies on wetting. II. Some effects of surface roughness (experimental)

The wetting of regularly rough solid bodies was investigated by means of capillarography. In this technique solid probes are immersed and withdrawn from liquid–fluid interfaces with steady velocities. Continuous observation of the three phase contact line (TPL) motion and recording of the capillary force are possible simultaneously. The effect of regular axisymmetric grooves on cylindrical rods on wetting hysteresis was found to follow theoretical predictions closely at large roughness dimensions (∼86 µm) in which case the TPL makes jumps from one equilibrium position to another while advancing. At lower rugosities (∼1 µm) the effect of regular roughness for a given concentric groove geometry is complicated by effects attributed to the dominant influence of chemical heterogeneity of the solid surface.

A contribution to the study of the effects of chemical heterogeneity on the ultimate properties of copolymer blends

Blends of statistical copolymers of styrene and 2-methoxyethyl methacrylate differing in their chemical heterogeneity were subjected to slow stress-strain experiments. The chemical heterogeneity of blends was chosen so as to be comparable with the chemical heterogeneity of the common high-conversion random copolymers. No pronounced influence of chemical heterogeneity on the copolymer properties under investigation could be observed, if the variance of chemical composition wasD(w)<10−2.

Influence of chemical heterogeneity on the distortion of carbon steel during thermal cycling

Influence of chemical heterogeneity on the distortion of carbon steel during thermal cycling