Epitaxial Strain Control of Relaxor Ferroelectric Phase Evolution

Understanding and ultimately controlling the large electromechanical effects in relaxor ferroelectrics requires intimate knowledge of how the local‐polar order evolves under applied stimuli. Here, the biaxial‐strain‐induced evolution of and correlations between polar structures and properties in epitaxial films of the prototypical relaxor ferroelectric 0.68PbMg_1/3Nb_2/3O₃–0.32PbTiO₃ are investigated. X‐ray diffuse‐scattering studies reveal an evolution from a butterfly‐ to disc‐shaped pattern and an increase in the correlation‐length from ≈8 to ≈25 nm with increasing compressive strain. Molecular‐dynamics simulations reveal the origin of the changes in the diffuse‐scattering patterns and that strain induces polarization rotation and the merging of the polar order. As the magnitude of the strain is increased, relaxor behavior is gradually suppressed but is not fully quenched. Analysis of the dynamic evolution of dipole alignment in the simulations reveals that, while, for most unit‐cell chemistries and configurations, strain drives a tendency toward more ferroelectric‐like order, there are certain unit cells that become more disordered under strain, resulting in stronger competition between ordered and disordered regions and enhanced overall susceptibilities. Ultimately, this implies that deterministic creation of specific local chemical configurations could be an effective way to enhance relaxor performance.     

Rapid formation of the sigma phase in 304 stainless steel during friction stir welding

Rapid formation of sigma phase occurred in 304 stainless steel during friction stir welding. A possibility was suggested that the sigma formation can be accelerated by the emergence of delta-ferrite at high temperature and the subsequent decomposition of the ferrite under the high strain and recrystallization induced by friction stirring.     

Effect of slaking on direct shear behaviour of crushed mudstones

This study investigates the effects of wetting and drying cycles, known as slaking, on the strength-displacement characteristics of crushed mudstone. A series of direct shear tests was conducted by simulating cyclic wetting and drying under different stress conditions using a modified direct shear apparatus. The effects of the stress ratio, the density of specimen, the initial water content before wetting, the slaking index, and the number of wetting and drying cycles on the test results was investigated. Experiments were also performed on less-slakable materials, including crushed sand stone, silica sand and glass beads, to compare the results with the crushed mudstone. Considerable creep displacement on the crushed mudstones was observed during both drying and wetting phases under the constant shear stress conditions. The creep displacement during the drying was more significant than during the wetting phase. The creep displacement accumulated with progressive wetting and drying cycles. The drying-induced displacement was observed when the water content became smaller than the amount of water absorption of the mudstone specimens. Correspondingly, a gradual decrease of the peak stress ratio was observed with the number of wetting and drying cycles. In contrast to the mudstones, the influence of cyclic wetting and drying on the crushed sand stone, silica sand and glass beads is almost negligible. A higher slaking index, a lower water content before wetting, and lower initial density accelerate the slaking of mudstones.     

Size selective continuous flow filtration method for detection of Cryptosporidium and Giardia

We describe a size selective continuous flow filtration method for detecting Cryptosporidium oocyst and Giardia cyst in finished water. Twenty liters of finished water spiked with Cryptosporidium oocysts (110) and Giardia cysts (60) were filtered through macro (5.0–10.0 μm) and micro (3.0 μm) pore-sized polycarbonate-track-etch (PCTE) membrane filters housed into two separate 47 mm diameter filter holders joined with a stainless steel nipple. The macro-pore-sized filters removed larger unwanted particles while allowing the Cryptosporidium oocysts and Giardia cysts to pass through, these being subsequently captured on the micro-pore-sized filter. The eluted oocysts and cysts were transferred onto the well-slide, stained by IFA and examined microscopically. The mean recovery efficiencies obtained for Cryptosporidium oocysts using the filter pairs of macro 5 μm and micro 3 μm, macro 8 μm and micro 3 μm, and macro 10 μm and micro 3 μm were 67.3%, 77.2–85.0% and 76.9–82.2%, respectively. Whereas the recovery rates for Giardia cysts using the same filter pairs were 0, 55 and 77.1%. The filter pair having the pore size of macro 10 μm and micro 3 μm was found to be most efficient in the simultaneous detection of Cryptosporidium and Giardia in the finished water. This method is simple, easy, rapid and economical.     

Chelating resin: Pyridine derivatives attached to poly(styrene) beads with spacer group

The pyridine derivatives were combined to poly(styrene) beads with spacer groups or a graft chain. These spacer-type and graft-type pyridine beads formed their Cu complexes with high rates and large stability constants; they act as an effective chelating resin. The pyridine residues were more mobile due to the spacer group and the graft chain, compared with the poly(4-vinylpyridine) powder.     

Intraparticle mass transfer in bidispersed porous ion exchanger part II: Mutual ion exchange

Intraparticle mass transfer of mutual ion exchange in MR-type resin was analyzed based on the assumption of parallel diffusion of counter ions in the solid phase and the macropore. Local equilibrium was also assumed between the concentration of counter ions in the solid phase and in the macropore, and the mass action law was applied. The Nernst-Planck equation was applied to the fluxes of ions diffusing through the solid phase and the macropore. The derived equations were solved numerically by using macropore and solid phase diffusivities obtained earlier by isotopic ion exchange. The theoretical lines agreed fairly well with the experimental uptake curves of R-H-NaCl, R-Na-HCl, R-Na-Zn(NO₃)₂, R-Zn-NaNO₃ and R-H-ZnCl₂ systems. The lower the concentration of bulk solution C_o is, the smaller the effect of C_o on the ion exchange rate becomes. The experimental uptake curves of C_o ≤ 0.01 (mmole/cm³) were not affected by C_o but agreed fairly well with the theoretical line for solid phase diffusion control. An approximate estimation method for obtaining the uptake curve was also proposed. This method gave fairly good approximation for equal valence ion exchange and for R-Na-Zn(NO₃)₂ systems.