scholarly journals Direct measurement of X-ray-induced heating of microcrystals

2019 ◽  
Vol 26 (4) ◽  
pp. 991-997 ◽  
Author(s):  
Anna J. Warren ◽  
Danny Axford ◽  
Robin L. Owen
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Direct Measurement ◽  
Temperature Control ◽  
Macromolecular Crystallography ◽  
Temperature Changes ◽  
X Ray ◽  
Dose Rates ◽  
Validation Tool

Temperature control is a key aspect of macromolecular crystallography, with the technique of cryocooling routinely being used to mitigate X-ray-induced damage. Beam-induced heating could cause the temperature of crystals to rise above the glass transition temperature, greatly increasing the rate of damage. X-ray-induced heating of ruby crystals of 20–40 µm in size has been quantified non-invasively by monitoring the emission wavelengths of X-ray-induced fluorescence during exposure to the X-ray beam. For the beam sizes and dose rates typically used in macromolecular crystallography, the temperature rises are of the order of 20 K. The temperature changes observed are compared with models in the literature and can be used as a validation tool for future models.

scholarly journals Direct measurement of X-ray induced heating of microcrystals

2019 ◽  
Author(s):  
Anna J Warren ◽  
Danny Axford ◽  
Robin L Owen
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Temperature Control ◽  
Macromolecular Crystallography ◽  
Temperature Dependent ◽  
Temperature Changes ◽  
X Ray ◽  
Dose Rates ◽  
Validation Tool

AbstractTemperature control is a key aspect of macromolecular crystallography, with the technique of cryocooling routinely used to mitigate X-ray induced damage. Beam induced heating could cause the temperature of crystals to rise above the glass transition temperature, greatly increasing the rate of damage. X-ray induced heating of ruby crystals 20-40 microns in size has been quantified non-invasively by monitoring the emission wavelengths of X-ray induced fluorescence during exposure to the X-ray beam. For beamsizes and dose-rates typically used in macromolecular crystallography the temperature rises are of order 20 K. The temperature changes observed are compared with models in the literature and can be used as a validation tool for future models.SynopsisX-ray induced heating of micro-crystals is quantified through the temperature-dependent shift in X-ray induced fluorescence from ruby crystals.

Glass transition temperature control by poly(norbornene-dicarboximide) copolymers

2014 ◽  
Vol 72 (3) ◽  
pp. 503-521 ◽  
Author(s):  
Andrew M. Spring ◽  
Daisuke Maeda ◽  
Masaaki Ozawa ◽  
Keisuke Odoi ◽  
Feng Qiu ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Temperature Control

PREPARATION AND PROPERTIES OF A NOVEL EPOXIDIZED CASTOR OIL/CLAY NANOCOMPOSITES

2004 ◽  
Vol 03 (04n05) ◽  
pp. 663-669 ◽  
Author(s):  
S.-J. PARK ◽  
F.-L. JIN ◽  
J.-R. LEE
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Mechanical Analysis ◽  
Clay Nanocomposites ◽  
X Ray Diffraction ◽  
X Ray ◽  
Tearing Energy ◽  
And Storage ◽  
Epoxidized Castor Oil

A novel nanocomposites of modified clay in a glassy epoxy were prepared using a direct melt intercalation technique. The contents of oganoclay were varied with 0, 1, 2, and 3 wt% and N-benzylpyrazinium hexafluoroantimonate (BPH) was used for curing of epoxy matrix as a cationic latent catalyst. Dynamic mechanical analysis (DMA) measurement was performed to examine the glass transition temperature of the nanocomposites. As a result, X-ray diffraction indicated the intercalation of the epoxy chains happening inside the gallery of clay. The nanocomposites showed a higher glass transition temperature and storage modulus than those of the pristine epoxy. The mechanical interfacial properties of the nanocomposites were also investigated and the improvement in tearing energy of 160% over pristine epoxy was obtained.

scholarly journals X-ray reflectivity study of the glass transition temperature of thin films

2014 ◽  
Vol 70 (a1) ◽  
pp. C885-C885
Author(s):  
Krassimir Stoev ◽  
Kenji Sakurai
Keyword(s):  
Thin Films ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Amorphous Materials ◽  
Bulk Material ◽  
Grazing Incidence ◽  
X Ray ◽  
Surface And Interface

The glass transition takes place in amorphous materials (like polymers) during heating or cooling, and can be described as reversible transition from a hard and brittle state into a rubber-like state. Although physical properties of the material change significantly during the glass transition, this is not a phase transition of the material. The temperature at which the transition between the glassy and rubbery state occurs is called the glass transition temperature, and this temperature is always lower than the melting temperature. Thermodynamically, the glass transition is associated with transfer of heat between the system and its surrounding and with an abrupt volume change. Previously it was shown that the glass transition temperature of nano-films is different from that of bulk materials [1], which signifies the importance of determining this parameter for such systems. In the current work, we use quick X-ray reflectivity (qXRR) measurements to determine the glass transition temperature of polyvinyl acetate (PVAc). PVAc is rubbery synthetic polymer with the formula (C4H6O2), a density of 1.18 g/cm3, and a glass transition temperature for bulk material of 30oC [2]. Regular X-ray reflectivity measurements are based on θ/2θ scans at grazing incidence and typically require 0.5-1.5 h for a single scan. The qXRR technique is based on simultaneous measurement of the whole angular x-ray reflectivity profile and is suitable for in-situ measurement without moving the sample and/or the x-ray optics. Thus, the qXRR technique allows for very fast measurement of the x-ray reflectivity curves (duration of each scan is typically 0.1–20 sec [3]), which permits studying the time evolution of chemical, thermal, and mechanical changes at the surface and interface of different materials. X-ray reflectivity measurements give information about both density and thickness of thin films, and are suitable for studying glass transition phenomena. Nano-thickness PVAc layers on a Si substrate were examined with the qXRR technique, with x-ray reflectivity scans (each 10-seconds in duration) being recorded while temperature was changed from 20 to 50oC (total of 331 scans over 7 hours and 46 minutes). In the current paper, the experimental setup, the data-processing, and the analysis of the results from the qXRR measurements will be presented.

scholarly journals Study of selected thermoplastics using dynamic mechanical analysis

2018 ◽  
Vol 157 ◽  
pp. 07002
Author(s):  
Marcel Kohutiar ◽  
Mariana Pajtášová ◽  
Róbert Janík ◽  
Iveta Papučová ◽  
Jana Pagáčová ◽  
...  
Keyword(s):  
Glass Transition ◽  
Infrared Spectroscopy ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Dynamic Mechanical Analysis ◽  
Mechanical Analysis ◽  
Stress And Strain ◽  
Analysis Method ◽  
X Ray ◽  
Dynamic Mechanical

The aim of given paper is to study selected polymers using dynamic mechanical analysis method (DMA). DMA is one of the most useful techniques for the study of the viscoelastic behaviour of thermoplastic polymers. In relation to DMA, an oscillatory stress and strain is applied to the material at specific frequencies and temperatures and based on this mentioned fact hereinbefore, the resulting changes after the loading in the material are measured. This technique allows detecting the melting temperature and the glass transition temperature of the thermoplastic materials. Furthermore, some spectroscopy techniques, such as energy dispersive X-ray spectroscopy (EDX) and infrared spectroscopy (IR), were also used for the investigation of the thermoplastics. The thermoplastics used for examination, namely polyethylene, polystyrene, polypropylene and polyethylene terephthalate, were gained from the waste of the packaging.

scholarly journals Crystal Structure and Mechanical Properties of Uniaxially Stretched PA612/SiO2 Films

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 711
Author(s):  
Yichao Wu ◽  
Anmin Huang ◽  
Shuhong Fan ◽  
Yuejun Liu ◽  
Xiaochao Liu
Keyword(s):  
Mechanical Properties ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Interplanar Spacing ◽  
Wide Angle ◽  
Sio2 Films ◽  
X Ray ◽  
Α Phase ◽  
Transmission Electron

Stretching has a significant effect on the microstructure and ultimate performance of semi-crystalline polymers. To investigate the effect of stretching on structure and mechanical properties of uniaxial stretched PA612/SiO2, PA612 and PA612/SiO2 films were prepared at four temperatures close to the glass transition temperature at various strain. The samples were characterized by a transmission electron microscope (TEM), wide-angle X-ray diffractometer (WAXD), Two-dimensional wide-angle X-ray Scattering (2D-WAXS), differential scanning calorimeter (DSC), dynamic mechanical analyzer (DMA), and stretching tests. The results showed that the α phase was the dominant phase in PA612 casting film, no obvious γ phase was observed, while both stretching and the presence of SiO2 can induce the generation of α phase and improve the crystallinity of PA612. Crystals were oriented along the stretching direction and the b axis was parallel to the equatorial direction after stretching. The interplanar spacing of (010/110) decreased with the increasing stretching temperature and expanded with the increasing strain, while stretching temperature and strain present negligible effect on the interplanar spacing of (100). The grain size increased with the stretching temperature while decreased with strain. The presence of SiO2 led to reduce the yield stress and the stress drop beyond yielding of the composite. Uniaxial stretching gave rise to a significant improvement in the fracture stress and the glass transition temperature.

Study of the Glass Transition Temperature of (Se100-xBix)90Te10 (x = 0, 0.5, 1, 1.5, 2, 2.5, 3) Alloys

2011 ◽  
Vol 316-317 ◽  
pp. 55-58 ◽  
Author(s):  
Deepshikha Sharma ◽  
Saneel K. Thakur
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Heating Rate ◽  
Network Model ◽  
Differential Analysis ◽  
X Ray Diffraction ◽  
Glass Transition Temperatures ◽  
X Ray ◽  
Xrd Studies

Alloys of (Se100-xBix)90Te10 (x =0, 0.5, 1, 1.5, 2, 2.5, 3 at.%) were prepared by using a conventional melt-quench technique. The samples under investigation were characterized using X-ray diffraction (XRD) and differential analysis (DTA) at a heating rate of 10K/min. It was found, from the XRD studies, that the alloys were amorphous in nature. The glass transition temperatures of the alloys were found to increase with increasing bismuth content. This increase in the glass transition temperature was explained on the basis of a chemically ordered network model.

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