scholarly journals Spin stress contribution to the lattice dynamics of FePt

2020 ◽  
Vol 6 (28) ◽  
pp. eaba1142 ◽  
Author(s):  
A. von Reppert ◽  
L. Willig ◽  
J.-E. Pudell ◽  
S. P. Zeuschner ◽  
G. Sellge ◽  
...  
Keyword(s):  
Mechanical Response ◽  
Materials Science ◽  
Negative Thermal Expansion ◽  
X Ray Diffraction ◽  
Poisson Effect ◽  
Continuous Film ◽  
Spin Disorder ◽  
Granular Microstructure ◽  
Out Of Plane ◽  
Spin Contribution

Invar-behavior occurring in many magnetic materials has long been of interest to materials science. Here, we show not only invar behavior of a continuous film of FePt but also even negative thermal expansion of FePt nanograins upon equilibrium heating. Yet, both samples exhibit pronounced transient expansion upon laser heating in femtosecond x-ray diffraction experiments. We show that the granular microstructure is essential to support the contractive out-of-plane stresses originating from in-plane expansion via the Poisson effect that add to the uniaxial contractive stress driven by spin disorder. We prove the spin contribution by saturating the magnetic excitations with a first laser pulse and then detecting the purely expansive response to a second pulse. The contractive spin stress is reestablished on the same 100-ps time scale that we observe for the recovery of the ferromagnetic order. Finite-element modeling of the mechanical response of FePt nanosystems confirms the morphology dependence of the dynamics.

scholarly journals Negative X-Ray Expansion in Cadmium Cyanide

2020 ◽  
Author(s):  
Chloe Coates ◽  
Claire A. Murray ◽  
Hanna Boström ◽  
Emily Reynolds ◽  
Andrew Goodwin
Keyword(s):  
Mechanical Response ◽  
Local Heating ◽  
Negative Thermal Expansion ◽  
Functional Materials ◽  
Temperature Phase ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cadmium Cyanide ◽  
Temperature Phase Transition

Cadmium cyanide, Cd(CN)<sub>2</sub>, is a flexible coordination polymer best studied for its strong and isotropic negative thermal expansion (NTE) effect. Here we show that this NTE is actually X-ray exposure dependent: Cd(CN)<sub>2</sub> contracts not only on heating but also on irradiation by X-rays. This behaviour contrasts that observed in other beam-sensitive materials, for which X-ray exposure drives lattice expansion. We call this effect ‘negative X-ray expansion’ (NXE) and suggest its origin involves an interaction between X-rays and cyanide ‘flips’; in particular, we rule out local heating as a possible mechanism. Irradiation also affects the nature of a low-temperature phase transition. Our analysis resolves discrepancies in NTE coefficients reported previously on the basis of X-ray diffraction measurements, and we establish the ‘true’ NTE behaviour of Cd(CN)<sub>2</sub> across the temperature range 150–750 K. The interplay between irradiation and mechanical response in Cd(CN)<sub>2</sub> highlights the potential for exploiting X-ray exposure in the design of functional materials.

scholarly journals Synthesis, PtS-Type Structure, and Anomalous Mechanics of the Cd(CN)2 Precursor Cd(NH3)2[Cd(CN)4]

2018 ◽  
Author(s):  
Andrew Goodwin ◽  
Chloe Coates ◽  
Joshua Makepeace ◽  
Andrew Seel ◽  
Mia Baise ◽  
...  
Keyword(s):  
Density Functional ◽  
Mechanical Response ◽  
Variable Temperature ◽  
Negative Thermal Expansion ◽  
Process Variable ◽  
X Ray Diffraction ◽  
Prolonged Heating ◽  
X Ray ◽  
Cadmium Metal ◽  
Nonaqueous Synthesis

We report the nonaqueous synthesis of Cd(CN)<sub>2</sub> by oxidation of cadmium metal with Hg(CN)<sub>2</sub> in liquid ammonia. The reaction proceeds <i>via</i> an intermediate of composition Cd(NH<sub>3</sub>)<sub>2</sub>[Cd(CN)<sub>4</sub>], which converts to Cd(CN)<sub>2</sub> on prolonged heating. Powder X-ray diffraction measurements allow us to determine the crystal structure of the previously-unreported Cd(NH<sub>3</sub>)<sub>2</sub>[Cd(CN)<sub>4</sub>], which we find to adopt a twofold interpenetrating PtS topology. We discuss the effect of partial oxidation on the Cd/Hg composition of this intermediate, as well as its implications for the reconstructive nature of the deammination process. Variable-temperature X-ray diffraction measurements allow us to characterise the anisotropic negative thermal expansion (NTE) behaviour of Cd(NH<sub>3</sub>)<sub>2</sub>[Cd(CN)<sub>4</sub>] together with the effect of Cd/Hg substitution; <i>ab initio</i> density functional theory (DFT) calculations reveal a similarly anomalous mechanical response in the form of both negative linear compressibility (NLC) and negative Poisson's ratios.

scholarly journals Negative X-Ray Expansion in Cadmium Cyanide

2020 ◽  
Author(s):  
Chloe Coates ◽  
Claire A. Murray ◽  
Hanna Boström ◽  
Emily Reynolds ◽  
Andrew Goodwin
Keyword(s):  
Mechanical Response ◽  
Local Heating ◽  
Negative Thermal Expansion ◽  
Functional Materials ◽  
Temperature Phase ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cadmium Cyanide ◽  
Temperature Phase Transition

Cadmium cyanide, Cd(CN)<sub>2</sub>, is a flexible coordination polymer best studied for its strong and isotropic negative thermal expansion (NTE) effect. Here we show that this NTE is actually X-ray exposure dependent: Cd(CN)<sub>2</sub> contracts not only on heating but also on irradiation by X-rays. This behaviour contrasts that observed in other beam-sensitive materials, for which X-ray exposure drives lattice expansion. We call this effect ‘negative X-ray expansion’ (NXE) and suggest its origin involves an interaction between X-rays and cyanide ‘flips’; in particular, we rule out local heating as a possible mechanism. Irradiation also affects the nature of a low-temperature phase transition. Our analysis resolves discrepancies in NTE coefficients reported previously on the basis of X-ray diffraction measurements, and we establish the ‘true’ NTE behaviour of Cd(CN)<sub>2</sub> across the temperature range 150–750 K. The interplay between irradiation and mechanical response in Cd(CN)<sub>2</sub> highlights the potential for exploiting X-ray exposure in the design of functional materials.

scholarly journals Facile investigation of reversible nanostructure changes in flexible crystals

2020 ◽  
Author(s):  
Shotaro Hayashi
Keyword(s):  
Structural Changes ◽  
Materials Science ◽  
Organic Crystals ◽  
Bending Stress ◽  
X Ray Diffraction ◽  
Poisson Effect ◽  
X Ray ◽  
Novel Approach ◽  
Quantitative Monitoring ◽  
Macroscopic Deformation

Abstract Detailed investigation of macroscopic deformation and nanoscopic structural changes in flexible organic crystals pose challenges for investigators. Herein, applied stress and subsequent relaxation of elastic organic crystals resulted in reversible macroscopic crystal deformation. X-ray diffraction with a curved jig revealed reversible nanoscopic structural changes in the crystal structure under the bending stress and relaxation. The crystal lattice changed quantitatively under the applied macroscopic stress-strain (%). This method enables quantitative monitoring of the dynamic nanoscopic structural changes in detail associated with crystal deformation through the use of standard laboratory X-ray diffraction analysis. Importantly, the developed method offers a way of quantitatively measuring reversible structural changes, without synchrotron X-ray analysis. Moreover, the analysis derives Poisson’s ratio, i.e., the ratio of the change in the width per unit width of materials. It is important in materials science, normally has a positive value in the range of 0.2–0.5. However, the crystals show not only the "Poisson effect" but also the unusual "negative Poisson effect". This novel approach for investigation generates unprecedented opportunities for understanding dynamic nanostructure changes in flexible organic crystals.

scholarly journals Synthesis, PtS-Type Structure, and Anomalous Mechanics of the Cd(CN)2 Precursor Cd(NH3)2[Cd(CN)4]

2018 ◽  
Author(s):  
Andrew Goodwin ◽  
Chloe Coates ◽  
Joshua Makepeace ◽  
Andrew Seel ◽  
Mia Baise ◽  
...  
Keyword(s):  
Density Functional ◽  
Mechanical Response ◽  
Variable Temperature ◽  
Negative Thermal Expansion ◽  
Process Variable ◽  
X Ray Diffraction ◽  
Prolonged Heating ◽  
X Ray ◽  
Cadmium Metal ◽  
Nonaqueous Synthesis

We report the nonaqueous synthesis of Cd(CN)<sub>2</sub> by oxidation of cadmium metal with Hg(CN)<sub>2</sub> in liquid ammonia. The reaction proceeds <i>via</i> an intermediate of composition Cd(NH<sub>3</sub>)<sub>2</sub>[Cd(CN)<sub>4</sub>], which converts to Cd(CN)<sub>2</sub> on prolonged heating. Powder X-ray diffraction measurements allow us to determine the crystal structure of the previously-unreported Cd(NH<sub>3</sub>)<sub>2</sub>[Cd(CN)<sub>4</sub>], which we find to adopt a twofold interpenetrating PtS topology. We discuss the effect of partial oxidation on the Cd/Hg composition of this intermediate, as well as its implications for the reconstructive nature of the deammination process. Variable-temperature X-ray diffraction measurements allow us to characterise the anisotropic negative thermal expansion (NTE) behaviour of Cd(NH<sub>3</sub>)<sub>2</sub>[Cd(CN)<sub>4</sub>] together with the effect of Cd/Hg substitution; <i>ab initio</i> density functional theory (DFT) calculations reveal a similarly anomalous mechanical response in the form of both negative linear compressibility (NLC) and negative Poisson's ratios.

X-ray microprobe for materials science

1994 ◽  
Vol 52 ◽  
pp. 56-57
Author(s):  
G.E. Ice
Keyword(s):  
Crystallographic Orientation ◽  
Local Structure ◽  
Materials Science ◽  
Chemical Information ◽  
X Ray Diffraction ◽  
Ray Optics ◽  
X Ray ◽  
Novel Materials ◽  
New Information ◽  
Elemental Sensitivity

The increasing availability of synchrotron x-ray sources has stimulated the development of advanced hard x-ray (E≥5 keV) microprobes. With new x-ray optics these microprobes can achieve micron and submicron spatial resolutions. The inherent elemental and crystallographic sensitivity of an x-ray microprobe and its inherently nondestructive and penetrating nature will have important applications to materials science. For example, x-ray fluorescent microanalysis of materials can reveal elemental distributions with greater sensitivity than alternative nondestructive probes. In materials, segregation and nonuniform distributions are the rule rather than the exception. Common interfaces to whichsegregation occurs are surfaces, grain and precipitate boundaries, dislocations, and surfaces formed by defects such as vacancy and interstitial configurations. In addition to chemical information, an x-ray diffraction microprobe can reveal the local structure of a material by detecting its phase, crystallographic orientation and strain.Demonstration experiments have already exploited the penetrating nature of an x-ray microprobe and its inherent elemental sensitivity to provide new information about elemental distributions in novel materials.

Large anisotropic negative thermal expansion in Cu-TDPAT metal-organic framework: A combined in situ X-ray diffraction and DRIFTS study

Nano Research ◽  
2020 ◽  
Vol 14 (2) ◽  
pp. 404-410 ◽  
Author(s):  
Mehrdad Asgari ◽  
Ilia Kochetygov ◽  
Hassan Abedini ◽  
Wendy L. Queen
Keyword(s):  
Thermal Expansion ◽  
Metal Organic Framework ◽  
Negative Thermal Expansion ◽  
X Ray Diffraction ◽  
X Ray ◽  
Metal Organic ◽  
Organic Framework

Self Assembling Nanostructured Delivery Vehicles for Biochemically Reactive Pairs

1994 ◽  
Vol 351 ◽  
Author(s):  
Nir Kossovsky ◽  
A. Gelman ◽  
H.J. Hnatyszyn ◽  
E. Sponsler ◽  
G.-M. Chow
Keyword(s):  
Physical Properties ◽  
Self Assembly ◽  
Materials Science ◽  
Technology Development ◽  
Biological Behavior ◽  
X Ray Diffraction ◽  
Self Assembling ◽  
Transmission Electron ◽  
Carbon Ceramic

ABSTRACTIntrigued by the deceptive simplicity and beauty of macromolecular self-assembly, our laboratory began studying models of self-assembly using solids, glasses, and colloidal substrates. These studies have defined a fundamental new colloidal material for supporting members of a biochemically reactive pair.The technology, a molecular transportation assembly, is based on preformed carbon ceramic nanoparticles and self assembled calcium-phosphate dihydrate particles to which glassy carbohydrates are then applied as a nanometer thick surface coating. This carbohydrate coated core functions as a dehydroprotectant and stabilizes surface immobilized members of a biochemically reactive pair. The final product, therefore, consists of three layers. The core is comprised of the ceramic, the second layer is the dehydroprotectant carbohydrate adhesive, and the surface layer is the biochemically reactive molecule for which delivery is desired.We have characterized many of the physical properties of this system and have evaluated the utility of this delivery technology in vitro and in animal models. Physical characterization has included standard and high resolution transmission electron microscopy, electron and x-ray diffraction and ζ potential analysis. Functional assays of the ability of the system to act as a nanoscale dehydroprotecting delivery vehicle have been performed on viral antigens, hemoglobin, and insulin. By all measures at present, the favorable physical properties and biological behavior of the molecular transportation assembly point to an exciting new interdisciplinary area of technology development in materials science, chemistry and biology.

Structural Properties Of Co/Re Superlattices

1991 ◽  
Vol 238 ◽  
Author(s):  
Y. Huai ◽  
R. W. Cochrane ◽  
Y. Shi ◽  
H. E. Fischer ◽  
M. Sutton
Keyword(s):  
Structural Disorder ◽  
Multilayer Films ◽  
Film Plane ◽  
X Ray Diffraction ◽  
X Ray ◽  
Bilayer Films ◽  
Out Of Plane ◽  
Reflectivity Data ◽  
Sharp Interfaces ◽  
Good Agreement

ABSTRACTThe structures of equal-thickness Co/Re multilayer films and several Co/Re bilayer films have been investigated by X-ray diffraction at low and high angles. Analysis of low-angle reflectivity data from bilayer films indicates that interfacial intermixing is limited to three monolayers and that the two interfacial configurations are different. The high-angle X-ray diffraction data show that multilayer films have coherent interfaces and a highly textured structure with hep [002] orientations normal to the film plane for periods 21 Å ≤ Λ ≤220 Å. Detailed structures have been determined by fitting the X-ray spectra to calculated ones using a trapezoidal model. The results indicate that samples with 42 Å≤ Λ ≤220 Å have relatively sharp interfaces, in good agreement with the bilayer results. In addition, an out-of-plane expansion of the Co (002) layer is observed in samples with large Λ and results from structural disorder leading to a reduced atomic density. For Λ <21 Å the interfaces arise from the rougher surfaces of the deposited layers.

scholarly journals Filling of Mater-Bi with Nanoclays to Enhance the Biofilm Rigidity

2018 ◽  
Vol 9 (4) ◽  
pp. 60 ◽  
Author(s):  
Giuseppe Cavallaro ◽  
Giuseppe Lazzara ◽  
Lorenzo Lisuzzo ◽  
Stefana Milioto ◽  
Filippo Parisi
Keyword(s):  
Tensile Properties ◽  
Food Packaging ◽  
Mechanical Response ◽  
Materials Science ◽  
Traction Force ◽  
Tensile Tests ◽  
Mechanical Analysis ◽  
Nanocomposite Films ◽  
Preliminary Study ◽  
Mechanical Performances

We investigated the efficacy of several nanoclays (halloysite, sepiolite and laponite) as nanofillers for Mater-Bi, which is a commercial bioplastic extensively used within food packaging applications. The preparation of Mater-Bi/nanoclay nanocomposite films was easily achieved by means of the solvent casting method from dichloroethane. The prepared bio-nanocomposites were characterized by dynamic mechanical analysis (DMA) in order to explore the effect of the addition of the nanoclays on the mechanical behavior of the Mater-Bi-based films. Tensile tests found that filling Mater-Bi with halloysite induced the most significant improvement of the mechanical performances under traction force, while DMA measurements under the oscillatory regime showed that the polymer glass transition was not affected by the addition of the nanoclay. The tensile properties of the Mater-Bi/halloysite nanotube (HNT) films were competitive compared to those of traditional petroleum plastics in terms of the elastic modulus and stress at the breaking point. Both the mechanical response to the temperature and the tensile properties make the bio-nanocomposites appropriate for food packaging and smart coating purposes. Here, we report a preliminary study of the development of sustainable hybrid materials that could be employed in numerous industrial and technological applications within materials science and pharmaceutics.

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