Structural Changes of Liquid Pb-Bi Eutectic Alloy

2012 ◽  
Vol 706-709 ◽  
pp. 878-883 ◽  
Author(s):  
Paolo Deodati ◽  
Franco Gauzzi ◽  
Roberto Montanari ◽  
Alessandra Varone
Keyword(s):  
Dynamic Modulus ◽  
Structural Changes ◽  
Distribution Functions ◽  
X Ray Diffraction ◽  
Mechanical Spectroscopy ◽  
Neutron Spallation Source ◽  
Driven System ◽  
Spallation Source ◽  
Accelerator Driven System ◽  
Diffraction Patterns

Liquid Pb–Bi eutectic (LBE) alloy has been selected as coolant and neutron spallation source for the development of MYRRHA, an accelerator driven system (ADS). The alloy has been characterized in liquid state from melting (125 °C) to 750 °C by mechanical spectroscopy, i.e. internal friction (IF) and dynamic modulus measurements. The experiments have been carried out using hollow reeds of austenitic stainless steel filled with Pb-Bi alloy and sealed at the extremities. Dynamic modulus showed a remarkable drop in the range 350-520 °C. In the same temperature range radial distribution functions (RDFs), determined from X-ray diffraction patterns, evidenced variations of the mean distance between the 1st nearest neighbour atoms. The phenomenon has been explained as a structural re-arrangement of atoms in the liquid metal.

Mechanical Spectroscopy Investigation of Liquid Pb-Bi Alloys

2012 ◽  
Vol 184 ◽  
pp. 434-439 ◽  
Author(s):  
Roberto Montanari ◽  
Alessandra Varone
Keyword(s):  
Distribution Functions ◽  
X Ray Diffraction ◽  
Mechanical Spectroscopy ◽  
X Ray ◽  
Neutron Spallation Source ◽  
Driven System ◽  
Spallation Source ◽  
Accelerator Driven System ◽  
The Mean ◽  
Diffraction Patterns

Liquid Pb–Bi eutectic alloy has been selected as coolant and neutron spallation source for the development of MYRRHA, an accelerator driven system. The alloy has been characterized in liquid state from melting (125 °C) to 650 °C by mechanical spectroscopy. Experiments have been carried out using hollow reeds of austenitic stainless steel filled with the Pb-Bi alloy and sealed at the extremities. From 350 °C to 520 °C modulus shows a remarkable drop accompanied by a broad internal friction maximum. In the same temperature range radial distribution functions, determined from X-ray diffraction patterns, evidenced variations of the mean distance between the 1st nearest neighbour atoms. The anelastic phenomena have been attributed to a structural re-arrangement of liquid metal. For comparison, other alloys of the Pb-Bi system with hypo-eutectic composition have been investigated.

High-temperature phases of NaNbO3 and NaTaO3

1999 ◽  
Vol 55 (1) ◽  
pp. 24-30 ◽  
Author(s):  
C. N. W. Darlington ◽  
K. S. Knight
Keyword(s):  
High Temperature ◽  
Structural Changes ◽  
Single Phase ◽  
Phenomenological Theory ◽  
Single Temperature ◽  
Neutron Spallation Source ◽  
Structure Determinations ◽  
Spallation Source ◽  
Diffraction Patterns ◽  
First Time

The high-temperature phases of the perovskites sodium niobate, NaNbO3, and sodium tantalate, NaTaO3, have been re-examined using the high-resolution powder diffractometer HRPD at the ISIS neutron spallation source; the two materials show the same sequence of phases with tilted octahedra. Diffraction patterns were measured every 5 K allowing structural changes with temperature within a single phase to be determined for the first time. Previous structure determinations within one phase had been performed at a single temperature only. The octahedra are tilted about pseudocubic \langle100\rangle directions and are also deformed; the magnitude of the deformation is shown to be proportional to the square of the angle of tilt as expected from a phenomenological theory applied to such transitions. The structures of NaNbO3 between 753 and 793 K and of NaTaO3 below 758 K are not as reported in the literature.

Metal-insulator transition in highly disordered carbon fibers

1992 ◽  
Vol 7 (4) ◽  
pp. 940-945 ◽  
Author(s):  
K. Kuriyama ◽  
M.S. Dresselhaus
Keyword(s):  
Carbon Fibers ◽  
Structural Changes ◽  
Dark Conductivity ◽  
Activated Carbon Fibers ◽  
X Ray Diffraction ◽  
Metal Insulator ◽  
Heat Treated ◽  
Insulator Metal Transition ◽  
Disordered Carbon ◽  
Diffraction Patterns

The electronic transition from localized to delocalized states of carriers in a disordered carbon material is investigated by photoconductivity measurements. Phenol-derived activated carbon fibers, where the carriers are strongly localized due to disorder, are heat treated in the range 300–2500 °C to give rise to the insulator-metal transition. Dark conductivity, Raman spectra, and x-ray diffraction patterns are also measured to characterize their structural changes. As a result, the transition temperature was determined to be rather low, around 1000 °C, considering the rapid decrease in the photoconductivity above this temperature. This decrease was ascribed to a fast recombination between the photoexcited carriers and the delocalized carriers generated by heat treatment.

Influence of Aging Time on the Structural Changes of Cassava Thermoplastic Starch

2012 ◽  
Vol 1372 ◽  
Author(s):  
José H. Mina ◽  
Alex Valadez ◽  
Pedro J. Herrera-Franco ◽  
Tanit Toledano
Keyword(s):  
Yield Stress ◽  
Amorphous Phase ◽  
Structural Changes ◽  
Thermoplastic Starch ◽  
X Ray Diffraction ◽  
X Ray ◽  
Second Stage ◽  
Diffraction Patterns ◽  
Type V ◽  
Stress Drops

ABSTRACTIn this work the change in the structural properties of cassava (manihot sculenta Crantz) thermoplastic starch (TPS) under controlled environment (humidity and temperature) was studied. Fourier Transform Infrared spectroscopy (FTIR) and X-ray diffraction (XRD) results showed an evident increasing in the amorphous phase of the TPS regarding the native starch. There was a relative decrease of the band at 1047 cm-1 associated to crystalline structure of starch compared to the amorphous peak at 1022 cm-1. The X-ray diffraction patterns confirmed the increment of the amorphous phase in the TPS samples. Likewise the X-ray diffraction patterns shows evidence of residual type C crystallinity and the formation of a new crystalline phase type VH due to the orientation induced in plasticization process. In first stage of conditioning the tensile yield stress drops from 7.5 drops to 0.5 MPa and the break strain increases 1000%. At the same time it seems that the crystallinity of the samples increases as was evidenced by the gradually increasing of the FTIR band at 1047 cm-1. In a second stage, the yield stress increases, the break strain drops and the crystallinity continue growing steadily. These findings suggest that coexist two phenomena simultaneously in the samples. A phenomenon of re-crystallization (retrogradation) that tends to make the material more stiff and a process of plasticization that tends to softening it. It seems that the latter mechanism predominates in the first stage, at short times, and the former in the second stage, at older times.

Physical Phenomena Leading to Melting of Metals

2017 ◽  
Vol 884 ◽  
pp. 3-17 ◽  
Author(s):  
Roberto Montanari ◽  
Alessandra Varone
Keyword(s):  
Dynamic Modulus ◽  
X Ray Diffraction ◽  
Mechanical Spectroscopy ◽  
Sharp Drop ◽  
X Ray ◽  
Novel Method ◽  
Diffraction Peaks ◽  
Pure Metals ◽  
Physical Phenomena ◽  
Specific Metal

Precursor phenomena of melting in pure metals and alloys have been investigated by means of Mechanical Spectroscopy (MS) and High Temperature X-ray Diffraction (HT-XRD). The examined materials were the pure metals In, Sn, Pb and Bi, and some alloys of the systems In-Sn and Pb-Bi with different compositions.MS tests have been carried out by means of a novel method developed by us that permits to operate in resonance conditions and employs hollow reeds of stainless steel containing the liquid metal. In all the metals a sharp drop of dynamic modulus and a Q-1 maximum were observed in a temperature range ΔT before melting that depends on the specific metal and its structure. Such anelastic behaviour is consistent with an increase of the interstitialcies concentration as predicted by the Granato’s theory.Moreover, HT-XRD evidenced that sudden grain re-orientation, shift and broadening of diffraction peaks occur just before the formation of the first liquid, therefore self-interstitials and vacancies seem to play a synergic role in melting. The increase of self-interstitials over ΔT has the effect of weakening interatomic bonds that favours the successive vacancy avalanche leading to the collapse of crystal lattice (melting).

Elemental Clustering and Structure of Liquid LBE

2014 ◽  
Vol 922 ◽  
pp. 785-790
Author(s):  
Santosh Balijepalli ◽  
Saulius Kaciulis ◽  
Matteo Amati ◽  
Roberto Montanari ◽  
Alessandra Varone
Keyword(s):  
Cluster Size ◽  
X Ray Diffraction ◽  
Progressive Change ◽  
Driven Systems ◽  
X Ray ◽  
Nearest Neighbours ◽  
Neutron Spallation Source ◽  
Different Temperatures ◽  
Spallation Source ◽  
Accelerator Driven Systems

Liquid Pb–Bi eutectic (LBE) alloy is of great interest as coolant and neutron spallation source for the accelerator driven systems (ADS). Scanning Photoemission Microscopy (SPEM) at the ELETTRA synchrotron radiation facility of Trieste was carried out on samples quenched from melt at different temperatures. SPEM analyses show that the two components (Pb and Bi) are not homogeneously distributed in the range of temperature from melting up to 518 °C, in particular they form clusters enriched in Pb and Bi. The cluster size decreases as temperature increases hence diffusion occurs between clusters and matrix leading to the progressive disgregation of clusters that is almost completed at 518 °C. Such micro-chemical evolution is accompanied by a structural change of the liquid evidenced by the results of High-temperature X-ray Diffraction (HT-XRD). In particular, radial distribution function (RDF) curves show a progressive change of the ratio between the shell radii of 1st and 2nd nearest neighbours.

Structure of Molten Mg, Ca, Sr, and Ba by X-ray Diffraction

1975 ◽  
Vol 30 (6-7) ◽  
pp. 801-805 ◽  
Author(s):  
Y. Waseda ◽  
K. Yokoyama ◽  
K. Suzuki
Keyword(s):  
Structural Information ◽  
Distribution Functions ◽  
X Ray Diffraction ◽  
Interatomic Distances ◽  
X Ray ◽  
Coordination Numbers ◽  
Structure Factors ◽  
Atomic Radial Distribution ◽  
Electron Transport Properties ◽  
Diffraction Patterns

Abstract X-ray diffraction patterns have been measured on molten alkaline earth metals (Mg, Ca, Sr, and Ba) in the temperature range from the melting points to 880 °C. In all cases the structure factors obtained were temperature insensitive. By the usual Fourier transformation of the structure factors, the atomic radial distribution functions were evaluated. From these the interatomic distances and coordination numbers were estimated. The structural information was applied to a discussion of the electron-transport properties using the Ziman theory.

Rapid small-angle X-ray diffraction of a tonically contracting molluscan smooth muscle recorded with imaging plates

1989 ◽  
Vol 22 (1) ◽  
pp. 72-74 ◽  
Author(s):  
Y. Tajima ◽  
K. Okada ◽  
O. Yoshida ◽  
T. Seto ◽  
Y. Amemiya
Keyword(s):  
Small Angle ◽  
Structural Changes ◽  
High Sensitivity ◽  
Imaging Plate ◽  
Layer Line ◽  
X Ray Diffraction ◽  
Thin Filaments ◽  
X Ray ◽  
Area Detector ◽  
Diffraction Patterns

Small-angle X-ray diffraction patterns from the anterior byssus retractor muscles of Mytilus edulis contracting tonically in response to stimulation with acetylcholine were recorded in a 30 s exposure with synchrotron radiation and a high-sensitivity X-ray area detector called an imaging plate. The 190 Å layer line from the thin filaments increased in intensity with increase in tonic tension up to 6 x 104 kg m−2. Above this value, the layer-line intensity remained almost constant and comparable to that for a contracting skeletal muscle, indicating that the same structural changes of the thin filaments occur in both muscles.

Abstract P505: Rv Sarcomeres From Lv-hfref Patients With Low Papi Have Abnormal Rv Thick Filament Structure

2021 ◽  
Vol 129 (Suppl_1) ◽  
Author(s):  
Vivek Jani ◽  
Mohammed I Aslam ◽  
Weikang Ma ◽  
Henry Gong ◽  
Anthony Cammarato ◽  
...  
Keyword(s):  
Structural Changes ◽  
Thick Filament ◽  
X Ray Diffraction ◽  
Left Heart Failure ◽  
Global Function ◽  
Reduced Ejection Fraction ◽  
Filament Structure ◽  
Myocyte Function ◽  
Band Spacing ◽  
Diffraction Patterns

Patients with left heart failure and reduced ejection fraction (HFrEF) have variable RV failure that, if present, drastically worsens outcomes. In a cohort of 21 HFrEF patients from two hospital sites, we have previously shown (Aslam et al, Eur J HF; 2020: volume 23, pages 339-341) that like global function, RV myocyte maximum calcium-activated myocyte tension (T max ) is quite variable (COV 27%). To determine if a relationship between RV myocyte function and indices of RV chamber function exists, we trained a random forest classifier based on 41 clinical variables, including hemodynamic, laboratory, and echocardiographic data, and queried the importance of each. This revealed that the most predictive model for reduced T max was based on the pulmonary artery pulsatility index (PAPi), an established clinical index of RV failure. To gain insight into potential mechanisms for depressed T max in HFrEF patients with a low PAPi, we obtained small angle x-ray diffraction patterns in 5 HFrEF patients with depressed PAPi and T max and compared this to 5 non-failing (NF) controls. The equatorial intensity ratio I(1,1)/I(1,0) was reduced in low T max RV muscle fibers vs. controls (0.250.06 vs. 0.180.02, P<0.0001), suggesting myosin heads are more associated with the thick filament backbone. In meridional reflections, we find a significant decrease in M3 band spacing (14.340.03 nm in NF vs. 14.300.01 nm in HFrEF; P=0.0013) suggesting more myosin heads are in the “OFF” configuration. The latter may underly tension reduction in RV myocytes from failing RV HFrEF patients. Ongoing studies will examine these structural changes in HFrEF patients with a broader range of PAPi and T max to test if this association applies. These findings focus attention on thick filament structural and configuration abnormalities as potential culprits underlying RV disease in HFrEF. Further studies using novel sarcomere enhancers will test if these changes can be remedied, and if so, in which patients.

scholarly journals The growth of decagonal Al–Co–Ni single crystals as a function of chemical composition

1997 ◽  
Vol 12 (9) ◽  
pp. 2274-2280 ◽  
Author(s):  
B. Zhang ◽  
M. Estermann ◽  
W. Steurer
Keyword(s):  
Single Crystals ◽  
Structural Changes ◽  
Ternary Systems ◽  
X Ray Diffraction ◽  
X Ray ◽  
Decagonal Phase ◽  
Different Types ◽  
Diffraction Patterns ◽  
The Stability ◽  
Diagram Analysis

Decaprismatic single crystals taken from a series of alloys of nominal compositions within Al65–77Co3–22Ni3–22 have been studied by means of x-ray diffraction techniques. The substitution of Co by Ni in increasing amounts changes the (pseudo)decagonal diffraction patterns drastically and indicates structural changes which range from a single-crystalline approximant via orientationally ordered nanodomain structures and quasiperiodic phases with different types of ordering phenomena, to a basic decagonal phase. A quantum phase diagram analysis shows a clear separation of the stability regions of the ternary systems described in this study and other decagonal phases.

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