The nature of the distinctive microscopic features in R5(Si[subscript x]Ge[subscript 1-x])4 magnetic refrigeration materials

Magnetic refrigeration is a promising technology that offers a potential for high energy efficiency. The giant magnetocaloric effect of the R5(Six,Ge1-x)4 alloys (where R=rare-earth and 0≤x≤1), which was discovered in 1997, make them perfect candidates for magnetic refrigeration applications. In this study the microstructures of Gd5(SixGe1-x)4 alloys have been characterized using electron microscopy techniques, with the focus being on distinctive linear features first examined in 1999. These linear features have been observed in R5(Six,Ge1-x) 4 alloys prepared from different rare-earths (Gd, Tb, Dy and Er) with different crystal structures (Gd5Si4-type orthorhombic, monoclinic and Gd5Ge4-type orthorhombic). Systematic scanning electron microscope studies revealed that these linear features are actually thin-plates, which grow along specific directions in the matrix material. The crystal structure of the thin-plates has been determined as hexagonal with lattice parameters a=b=8.53A and c=6.40A, using selected area diffraction (SAD). Energy dispersive spectroscopy analysis, carried out in both scanning and transmission electron microscopes, showed that the features have a composition approximating to R5(Six,Ge1-x )3.phase. Orientation relationship between the matrix and the thin-plates has been calculated as [-1010](1-211)p//[010](10-2) m. The growth direction of the thin plates are calculated as (22 0 19) and (-22 0 19) by applying the Deltag approach of Zhang and Purdy to the SAD patterns of this system. High Resolution TEM images of the Gd5Ge4 were used to study the crystallographic relationship. A terrace-ledge structure was observed at the interface and a 7° rotation of the reciprocal lattices with respect to each other, consistent with the determined orientation relationship, was noted. Both observations are consistent with the stated hypothesis that the growth direction of the thin-plates is parallel to an invariant line direction. Based on the terrace-ledge structure of the thin-plate interface a displacive-diffusional growth mechanism has been proposed to explain the rapid formation of the R 5(Six,Ge1-x)3 plates

The Nature of the Distinctive Microscopic Features in R5(SixGe1-x)4 Magnetic Refrigeration Materials

Magnetic refrigeration is a promising technology that offers a potential for high energy efficiency. The giant magnetocaloric effect of the R{sub 5}(Si{sub x}, Ge{sub 1-x}){sub 4} alloys (where R=rare-earth and O {le} x {le} 1), which was discovered in 1997, make them perfect candidates for magnetic refrigeration applications. In this study the microstructures of Gd{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4} alloys have been characterized using electron microscopy techniques, with the focus being on distinctive linear features first examined in 1999. These linear features have been observed in R{sub 5}(Si{sub x}, Ge{sub 1-x}){sub 4} alloys prepared from different rare-earths (Gd, Tb, Dy and Er) with different crystal structures (Gd{sub 5}Si{sub 4}-type orthorhombic, monoclinic and Gd{sub 5}Ge{sub 4}-type orthorhombic). Systematic scanning electron microscope studies revealed that these linear features are actually thin-plates, which grow along specific directions in the matrix material. The crystal structure of the thin-plates has been determined as hexagonal with lattice parameters a=b=8.53 {angstrom} and c=6.40 {angstrom} using selected area diffraction (SAD). Energy dispersive spectroscopy analysis, carried out in both scanning and transmission electron microscopes, showed that the features have a composition approximating to R{sub 5}(Si{sub x},Ge{sub 1-x}){sub 3}.phase. Orientation relationship between the matrix and the thin-plates has been calculated as [- 1010](1-211){sub p}//[010](10-2){sub m}. The growth direction of the thin plates are calculated as (22 0 19) and (-22 0 19) by applying the Ag approach of Zhang and Purdy to the SAD patterns of this system. High Resolution TEM images of the Gd{sub 5}Ge{sub 4} were used to study the crystallographic relationship. A terrace-ledge structure was observed at the interface and a 7{sup o} rotation of the reciprocal lattices with respect to each other, consistent with the determined orientation relationship, was noted. Both observations are consistent with the stated hypothesis that the growth direction of the thin-plates is parallel to an invariant line direction. Based on the terrace-ledge structure of the thin-plate interface a displacive-diffusional growth mechanism has been proposed to explain the rapid formation of the R{sub 5}(Si{sub x},Ge{sub 1-x}){sub 3} plates

Development of a Versatile Methodology for the Synthesis of Poly(2,5-benzophenone) Containing Coil−Rod−Coil Triblock Copolymers

A short, simple, versatile methodology was developed for the synthesis of poly(2,5-benzophenone) containing coil−rod−coil triblock copolymers. After a model study, poly(2,5-benzophenone) macroinitiators were synthesized via end-capping poly(2,5-dichlorobenzophenone) synthesized by Ni(0)-catalyzed polymerization and functionalization of the chain ends utilizing phase transfer chlorination. Varying molecular weights of polystyrene-b-poly(2,5-benzophenone)-b-polystyrene were synthesized using the macroinitiators in the atom transfer radical polymerization of styrene. The materials were characterized by gel permeation chromatography, nuclear magnetic resonance, differential scanning calorimetry, and transmission electron microscopy. Applications were explored through dynamic mechanical analysis and the construction of a distributed junction photovoltaic device

Microstructural Evolution of Secondary Phases in the Cast Duplex Stainless Steels CD3MN and CD3MWCuN

The isothermal formation behavior of secondary phases in two types of duplex stainless steels (DSS), CD3MN and CD3MWCuN, was characterized. Samples were heat treated from 1 minute to 30 days at temperatures from 700°C to 900°C. Small carbide (M23C6) and nitride (Cr2N) precipitates, together with the intermetallic phases sigma and chi, were observed using scanning electron microscopy (SEM) and confirmed by transmission electron microscopy (TEM) analyses. Based on SEM analysis, time-temperature-transformation (TTT) curves for the sigma and chi phases were determined by measuring their volume fractions from backscattered electron micrographs of heat-treated and quenched sample cross sections. Resulting TTT curves showed that the maximum formation temperature for chi is lower than that for sigma, while the time to reach 1 vol pct formation is much less for sigma than it is for chi. The thermodynamic driving forces associated with the sigma and chi formation were assessed using Thermo-Calc

The nature of the distinctive microscopic features in R5(Si[subscript x]Ge[subscript 1-x])4 magnetic refrigeration materials

Magnetic refrigeration is a promising technology that offers a potential for high energy efficiency. The giant magnetocaloric effect of the R5(Six,Ge1-x)4 alloys (where R=rare-earth and 0≤x≤1), which was discovered in 1997, make them perfect candidates for magnetic refrigeration applications. In this study the microstructures of Gd5(SixGe1-x)4 alloys have been characterized using electron microscopy techniques, with the focus being on distinctive linear features first examined in 1999. These linear features have been observed in R5(Six,Ge1-x) 4 alloys prepared from different rare-earths (Gd, Tb, Dy and Er) with different crystal structures (Gd5Si4-type orthorhombic, monoclinic and Gd5Ge4-type orthorhombic). Systematic scanning electron microscope studies revealed that these linear features are actually thin-plates, which grow along specific directions in the matrix material. The crystal structure of the thin-plates has been determined as hexagonal with lattice parameters a=b=8.53A and c=6.40A, using selected area diffraction (SAD). Energy dispersive spectroscopy analysis, carried out in both scanning and transmission electron microscopes, showed that the features have a composition approximating to R5(Six,Ge1-x )3.phase. Orientation relationship between the matrix and the thin-plates has been calculated as [-1010](1-211)p//[010](10-2) m. The growth direction of the thin plates are calculated as (22 0 19) and (-22 0 19) by applying the Deltag approach of Zhang and Purdy to the SAD patterns of this system. High Resolution TEM images of the Gd5Ge4 were used to study the crystallographic relationship. A terrace-ledge structure was observed at the interface and a 7° rotation of the reciprocal lattices with respect to each other, consistent with the determined orientation relationship, was noted. Both observations are consistent with the stated hypothesis that the growth direction of the thin-plates is parallel to an invariant line direction. Based on the terrace-ledge structure of the thin-plate interface a displacive-diffusional growth mechanism has been proposed to explain the rapid formation of the R 5(Six,Ge1-x)3 plates.</p

Electromagnetic shielding efficiency of nonwoven insulation panels designed with recycled textiles and copper wires

Insulation applications of nonwovens has become increasingly important in the construction and automotive industries since the late 1990s. Besides, recycling and reusing fibrous waste becomes one of the most important raw materials of nonwovens to promote effective use of resources recently. On the other hand, metals are now being increasingly replaced by thermoplastics for housing commercial equipment, due to flexibility, light weight, and low cost for electromagnetic shielding purposes. In this study, we design nonwoven insulation panels containing copper wires with different intensity and length to provide electromagnetic wave protection by using recycled textiles. The method is simple, the material is cheaper, and more importantly, the whole material can be produced by using only waste materials. The electromagnetic shielding characteristics of the panels were measured and discussed. The experimental results indicated that the variation in wire length and amount affects the electromagnetic (EM) shielding property. With this method, the products with electromagnetic shielding effect in certain areas can be developed. In particular, there is a big potential for electromagnetic shielding applications in wide bandwidth, such as 1125-2925 MHz

Production and characterization of boron nanoparticles synthesized with a thermal plasma system

Abstract A new method for the production of boron nanoparticles is described. Boron trichloride is dissociated through injection into thermal plasma followed by a nucleation process producing boron nanoparticles. The ambient oxidation of the as-produced nanoparticles is also investigated. The nanoparticles were characterized with scanning transmission electron microscopy, electron energy loss spectroscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy to investigate their purity and stability under ambient conditions

Electromagnetic Shielding Properties of Plain Knitted Fabrics Containing Conductive Yarns

WOS: 000316641600012In this study, stainless steel conductive yarns with 500 tex fineness and 14 Omega/m linear resistances were inserted into the reverse side of the knitted fabrics made from acrylic yarns. Six types of knitted fabrics with conductive yarns were produced on an E=7 gauge electronic flat bed knitting machine. Then the electromagnetic shielding efficiency (EMSE) of the sample fabrics were measured in the frequency range of 750 MHz - 3000 MHz. The EMSE variations of the sample fabrics having conductive yarns with respect to fabric structure and polarization type (vertical and horizontal) were also investigated. It was observed that the same samples showed different behaviors and have dissimilar EMSE values in different polarization conditions. When compared to horizontal polarization measurements, the vertical measurement results gave better EMSE values