scholarly journals Corelation between the crystallisation process and change in thermoelectromotive force for the amorphous alloy Fe89.8Ni1.5Si5.2B3C0.5

2003 ◽  
Vol 35 (1) ◽  
pp. 31-36 ◽  
Author(s):  
Aleksa Maricic ◽  
Momcilo Ristic
Keyword(s):  
Amorphous Alloy ◽  
Atomic Structure ◽  
Structural Changes ◽  
Amorphous State ◽  
Isothermal Heating ◽  
Scanning Calorimetry ◽  
Free Electron Density ◽  
Thermoelectromotive Force ◽  
Temperature Range ◽  
Crystallisation Process

Thermal and kinetic analyses of the structural changes for the amorphous alloy Fe89.8Ni1.5Si5.2B3C0.5, during the processes of non-isothermal heating and isothermal annealing, have been performed. The crystallisation process has been investigated using the method of differential scanning calorimetry (DSC). It is determined that this alloy crystalizes through three different stages. Changes in the electronic structure of the amorphous tape, for the temperature range 20 to 700?C have been studied. This was achieved by measuring the thermoelectromotive force (TEMS), of the thermo pair made of two tapes with same chemical structure of the alloy FeNiSiBC, but different atomic structure: one is in the crystal state (CL) and the other is in the amorphous state (AM). Analysis of the temperature dependence of the electromotive force has shown the following: the investigated alloy is thermically stable up to 450?C and changes in the atomic structure as well as equalising of the free electron density in both parts of the thermo pair AM-CL, take place in the temperature range from 450 to 550?C. Kinetic parameters of the process were determined by measuring time dependence of the TEMS in isothermic conditions at the temperatures 450, 480 and 510?C.

Lattice Relaxation in Ni-P Amorphous Alloy Accompanied with Growth of Ni3P Nanocrystals

2007 ◽  
Vol 558-559 ◽  
pp. 1363-1366 ◽  
Author(s):  
Shunichiro Tanaka ◽  
Jun Takioto ◽  
Sang Koo Kwon ◽  
Kozo Shinoda ◽  
Shigeru Suzuki
Keyword(s):  
High Temperature ◽  
Amorphous Alloy ◽  
Structural Changes ◽  
Exothermic Reaction ◽  
Amorphous State ◽  
Lattice Relaxation ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Exafs Analysis

Studies on lattice change of a nickel-phosphorus amorphous alloy were carried out using not only high temperature X-ray diffraction but also extended X-ray absorption fine structure (EXAFS) analysis. Their thermal properties were characterized by differential scanning calorimetry (DSC). Since the results suggested that lattice relaxation occurred in the amorphous state by annealing, EXAFS measurements were carefully performed for characterizing the local structure of the amorphous alloys. The EXAFS analysis showed that the local structures around Ni atoms, which may be the Ni-Ni and Ni-P correlation, were changed by annealing. High temperature X-ray diffraction showed that small amount of crystal phase appeared by annealing up to 820 K, while clear diffraction peaks of Ni3P were observed above 1100 K. These micro/nanoscale structural changes did not correspond to that obtained by DSC which showed an exothermic reaction of atomistic reordering at 630 K. We need analysis of the nanostructures by small angle X-ray scattering or a high resolution transmission electron microscope.

scholarly journals Influence of structural changes on electrical and magnetic properties of the Co84Fe5,3Si8,5B2,2 amorphous alloy

2005 ◽  
Vol 37 (3) ◽  
pp. 231-235 ◽  
Author(s):  
S.R. Djukic ◽  
Radojko Simeunovic ◽  
Aleksa Maricic
Keyword(s):  
Activation Energy ◽  
Amorphous Alloy ◽  
Relaxation Process ◽  
Structural Changes ◽  
Crystallization Process ◽  
State Density ◽  
Annealing Process ◽  
Scanning Calorimetry ◽  
Electrical And Magnetic Properties ◽  
Electronic State Density

The crystallization process of the Co84Fe5.3Si8.5B2.2 amorphous alloy examined by differential scanning calorimetry (DSC) exhibits three exothermal steps at Tcr1=649K, Tcr2=800K, and Tcr3=838K. The rate constants of the first relaxation process (determined at 598K and 623K) are k1=5*10-4 s and k2=8*10-4 s and the corresponding activation energy Ea1=26.23 kJ/mol. The data for the relaxation process before the second crystallization step (determined at 683K and 713K) are k3=14.5*10-4 s and k4=17.5*10-4 s and the corresponding activation energy Ea2=60.0 kJ/mol. The process of structural relaxation in non-isothermal and isothermal conditions was studied by analysis of the results of measurements of the thermo electromotive force (TEMF). From the change of the temperature coefficient of TEMF that follows each annealing process, the relative electronic state density changes at the Fermi level were determined: ?N21/N2=5,45%, ?N22/N2=5,76%, ?N23/N2=7,57% and ?N24/N2=9,85%.

Characterization of Amorphous, Magnetic Fe-Si-B Ribbons

2013 ◽  
Vol 543 ◽  
pp. 476-478
Author(s):  
Eirini Varouti
Keyword(s):  
Structural Changes ◽  
Amorphous State ◽  
Barkhausen Noise ◽  
Chemical Compositions ◽  
Magnetic Barkhausen Noise ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Noise Measurements ◽  
Shed Light

The aim of this study is to contribute to a better understanding of the properties, structure and crystallization process of the amorphous Fe-based ribbon with the following chemical compositions: Fe80SixB20-x (x=5,6,8) and Fe75Si15B10. Thermal analysis, including Differential Scanning Calorimetry and Magnetic-Thermogravimetric Analysis, were used to shed light in the thermal stability and structural changes taking place during the transformation from the amorphous state to the crystalline state. The arising microstructure was observed via X-ray diffraction. Finally, Magnetic Barkhausen Noise measurements took place so as conclusions to be derived relevant to the dependence between the parameters of the Magnetic Barkhausen Noise and the chemical composition of the amorphous ribbons.

A Transmission Electron Microscopical Investigation of Phase Transformations in TiNi

1980 ◽  
Vol 38 ◽  
pp. 340-341
Author(s):  
P. Moine ◽  
G. M. Michal ◽  
R. Sinclair
Keyword(s):  
Electron Microscopy ◽  
Phase Transformations ◽  
Applied Stress ◽  
Structural Changes ◽  
Microscopical Investigation ◽  
Temperature Range ◽  
Transmission Electron ◽  
Electron Microscopical ◽  
Diffraction Effects ◽  
Microscopy Images

Premartensitic effects in near equiatomic TiNi have been pointed out by several authors(1-5). These include anomalous contrast in electron microscopy images (mottling, striations, etc. ),diffraction effects(diffuse streaks, extra reflections, etc.), a resistivity peak above Ms (temperature at which a perceptible amount of martensite is formed without applied stress). However the structural changes occuring in this temperature range are not well understood. The purpose of this study is to clarify these phenomena.

The effect of cooling rate on crystallization behavior and tensile properties of CF/PEEK composites

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Guangming Dai ◽  
Lihua Zhan ◽  
Chenglong Guan ◽  
Minghui Huang
Keyword(s):  
Cooling Rate ◽  
Crystallization Temperature ◽  
Crystallization Behavior ◽  
Crystalline Polymer ◽  
Scanning Calorimetry ◽  
Nonisothermal Crystallization ◽  
Cooling Rates ◽  
Control Range ◽  
Temperature Range ◽  
Transverse Tensile

Abstract In this study, the differential scanning calorimetry (DSC) tests were performed to measure the nonisothermal crystallization behavior of carbon fiber reinforced polyether ether ketone (CF/PEEK) composites under different cooling rates. The characteristic parameters of crystallization were obtained, and the nonisothermal crystallization model was established. The crystallization temperature range of the material at different cooling rates was predicted by the model. The unidirectional laminates were fabricated at different cooling rates in the crystallization temperature range. The results showed that the crystallization temperature range shifted to a lower temperature with the increase of cooling rate, the established nonisothermal crystallization model was consistent with the DSC test results. It is feasible to shorten the cooling control range from the whole process to the crystallization range. The crystallinity and transverse tensile strength declined significantly with the increase of the cooling rate in the crystallization temperature range. The research results provided theoretical support for the selection of cooling conditions and temperature control range, which could be applied to the thermoforming process of semi-crystalline polymer matrixed composites to improve the manufacturing efficiency.

scholarly journals Dynamic Single-Fiber Pull-Out of Polypropylene Fibers Produced with Different Mechanical and Surface Properties for Concrete Reinforcement

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 722
Author(s):  
Enrico Wölfel ◽  
Harald Brünig ◽  
Iurie Curosu ◽  
Viktor Mechtcherine ◽  
Christina Scheffler
Keyword(s):  
Tensile Strength ◽  
Dynamic Loading ◽  
Melt Spinning ◽  
Structural Changes ◽  
High Surface ◽  
Single Fiber ◽  
Scanning Calorimetry ◽  
Matrix Interaction ◽  
Pull Out ◽  
Fiber Matrix

In strain-hardening cement-based composites (SHCC), polypropylene (PP) fibers are often used to provide ductility through micro crack-bridging, in particular when subjected to high loading rates. For the purposeful material design of SHCC, fundamental research is required to understand the failure mechanisms depending on the mechanical properties of the fibers and the fiber–matrix interaction. Hence, PP fibers with diameters between 10 and 30 µm, differing tensile strength levels and Young’s moduli, but also circular and trilobal cross-sections were produced using melt-spinning equipment. The structural changes induced by the drawing parameters during the spinning process and surface modification by sizing were assessed in single-fiber tensile experiments and differential scanning calorimetry (DSC) of the fiber material. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle measurements were applied to determine the topographical and wetting properties of the fiber surface. The fiber–matrix interaction under quasi-static and dynamic loading was studied in single-fiber pull-out experiments (SFPO). The main findings of microscale characterization showed that increased fiber tensile strength in combination with enhanced mechanical interlocking caused by high surface roughness led to improved energy absorption under dynamic loading. Further enhancement could be observed in the change from a circular to a trilobal fiber cross-section.

scholarly journals Comparative Study of Structural Changes of Polylactide and Poly(ethylene terephthalate) in the Presence of Trichoderma viride

2021 ◽  
Vol 22 (7) ◽  
pp. 3491
Author(s):  
Grażyna B. Dąbrowska ◽  
Zuzanna Garstecka ◽  
Ewa Olewnik-Kruszkowska ◽  
Grażyna Szczepańska ◽  
Maciej Ostrowski ◽  
...  
Keyword(s):  
Structural Changes ◽  
Ethylene Terephthalate ◽  
Molecular Mechanisms ◽  
Blot Hybridization ◽  
Trichoderma Viride ◽  
Cost Effective ◽  
Plastic Pollution ◽  
Scanning Calorimetry ◽  
Poly Ethylene Terephthalate ◽  
Poly Ethylene

Plastic pollution is one of the crucial global challenges nowadays, and biodegradation is a promising approach to manage plastic waste in an environment-friendly and cost-effective way. In this study we identified the strain of fungus Trichoderma viride GZ1, which was characterized by particularly high pectinolytic activity. Using differential scanning calorimetry, Fourier-transform infrared spectroscopy techniques, and viscosity measurements we showed that three-month incubation of polylactide and polyethylene terephthalate in the presence of the fungus lead to significant changes of the surface of polylactide. Further, to gain insight into molecular mechanisms underneath the biodegradation process, western blot hybridization was used to show that in the presence of poly(ethylene terephthalate) (PET) in laboratory conditions the fungus produced hydrophobin proteins. The mycelium adhered to the plastic surface, which was confirmed by scanning electron microscopy, possibly due to the presence of hydrophobins. Further, using atomic force microscopy we demonstrated for the first time the formation of hydrophobin film on the surface of aliphatic polylactide (PLA) and PET by T. viride GZ1. This is the first stage of research that will be continued under environmental conditions, potentially leading to a practical application.

scholarly journals Metastable Intermediates as Stepping Stones on the Maturation Pathways of Viral Capsids

mBio ◽  
2014 ◽  
Vol 5 (6) ◽  
Author(s):  
Giovanni Cardone ◽  
Robert L. Duda ◽  
Naiqian Cheng ◽  
Lili You ◽  
James F. Conway ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Large Scale ◽  
Structural Changes ◽  
Energy Landscape ◽  
Potential Hazard ◽  
Stepping Stones ◽  
Scanning Calorimetry ◽  
Conformational Effects ◽  
Capsid Maturation ◽  
Capsid Integrity

ABSTRACT As they mature, many capsids undergo massive conformational changes that transform their stability, reactivity, and capacity for DNA. In some cases, maturation proceeds via one or more intermediate states. These structures represent local minima in a rich energy landscape that combines contributions from subunit folding, association of subunits into capsomers, and intercapsomer interactions. We have used scanning calorimetry and cryo-electron microscopy to explore the range of capsid conformations accessible to bacteriophage HK97. To separate conformational effects from those associated with covalent cross-linking (a stabilization mechanism of HK97), a cross-link-incompetent mutant was used. The mature capsid Head I undergoes an endothermic phase transition at 60°C in which it shrinks by 7%, primarily through changes in its hexamer conformation. The transition is reversible, with a half-life of ~3 min; however, >50% of reverted capsids are severely distorted or ruptured. This observation implies that such damage is a potential hazard of large-scale structural changes such as those involved in maturation. Assuming that the risk is lower for smaller changes, this suggests a rationalization for the existence of metastable intermediates: that they serve as stepping stones that preserve capsid integrity as it switches between the radically different conformations of its precursor and mature states. IMPORTANCE Large-scale conformational changes are widespread in virus maturation and infection processes. These changes are accompanied by the release of conformational free energy as the virion (or fusogenic glycoprotein) switches from a precursor state to its mature state. Each state corresponds to a local minimum in an energy landscape. The conformational changes in capsid maturation are so radical that the question arises of how maturing capsids avoid being torn apart. Offering proof of principle, severe damage is inflicted when a bacteriophage HK97 capsid reverts from the (nonphysiological) state that it enters when heated past 60°C. We suggest that capsid proteins have been selected in part by the criterion of being able to avoid sustaining collateral damage as they mature. One way of achieving this—as with the HK97 capsid—involves breaking the overall transition down into several smaller steps in which the risk of damage is reduced.

Thermo-Optical Properties of Perfluorinated Sulfonic Acid Membranes: An Investigation of Hydration Based on Absorption Spectra

2017 ◽  
Vol 71 (11) ◽  
pp. 2504-2511 ◽  
Author(s):  
Daniele T. Dias ◽  
Guy Lopes ◽  
Tales Ferreira ◽  
Ivanir L. Oliveira ◽  
Caroline D. Rosa
Keyword(s):  
Sulfonic Acid ◽  
Room Temperature ◽  
Water Retention ◽  
Structural Changes ◽  
Optical Characterization ◽  
Scanning Calorimetry ◽  
Experimental Procedure ◽  
Nafion Membranes ◽  
Perfluorinated Sulfonic Acid

The Nafion membranes are widely used in electrochemical applications such as fuel cells, chlor-alkali cells, and actuators–sensors. In this work, the thermal-optical characterization of Nafion in acid form was performed by photoacoustic spectroscopy, thermogravimetry, and differential scanning calorimetry. In the experimental procedure three distinct hydration levels were considered: (1) pristine membrane (λ ≅ H2O/–SO3H ≅ 5.6); (2) swelling process (λ ≅ 17.4); and (3) drying at controlled room temperature after swelling process (λ ≅ 6.5). The discovered behaviors showed significant irreversible structural changes induced by water retention in the membrane. These structural changes depend on the water population present in the clusters and also affect the directional thermal diffusivity of the membrane irreversibly.

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