Miloš Janeček; Peter Minárik; Tomáš Krajňák; Kristína Bartha; Josef Straskuy; Jakub Cizek
Abstract
Mg22Gd alloy was processed by high pressure torsion (HPT) at room temperature and the pressure of 2 GPa. A series of specimens with different number of rotations N (N = 0-15) was prepared from the initial coarse grained as cast material. Mechanical properties were investigated by microhardness mapping. ...
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Mg22Gd alloy was processed by high pressure torsion (HPT) at room temperature and the pressure of 2 GPa. A series of specimens with different number of rotations N (N = 0-15) was prepared from the initial coarse grained as cast material. Mechanical properties were investigated by microhardness mapping. The microhardness was found to increase with increasing strain imposed by HPT and tend to saturate at about HV = 145. The microstructure (phase morphology and composition, etc.) evolution with strain was investigated by scanning electron microscopy and EDS. High Gd content in the alloy resulted in the precipitation of stable Mg5Gd phase. This phase exhibited apparently higher hardness than the magnesium matrix. During straining the phase was continuously fragmented and only tiny particles were found in heavily strained material. Electron back scatter diffraction (EBSD) and automated crystallographic orientation mapping in transmission electron (ACOM-TEM) were employed to characterize the fragmentation of the grain structure. HPT was found to result in strong grain refinement by the factor of approximately 1000. The dislocation density was determined by positron annihilation spectroscopy. Significant twinning was found in the initial stages of HPT straining. At high strains twin formation was suppressed and only dislocation storage in the material occurs.
K. K. Bamzai; Rashmi Gupta; Shivani Suri; Vishal Singh
Abstract
Magnesium hydrogen phosphate (MHP) and transition metal doped cadmium magnesium hydrogen phosphate (CdMHP) was synthesized in the form of crystalline material by room temperature solution technique known as gel encapsulation technique. The synthesized crystals were then characterized for their structural, ...
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Magnesium hydrogen phosphate (MHP) and transition metal doped cadmium magnesium hydrogen phosphate (CdMHP) was synthesized in the form of crystalline material by room temperature solution technique known as gel encapsulation technique. The synthesized crystals were then characterized for their structural, mechanical and electrical investigations using various chemical and physical methods. X - ray diffraction analysis (XRD) establishes magnesium hydrogen phosphate and cadmium magnesium hydrogen phosphate belonging to orthorhombic crystal system with space group Pbca. The mechanical behaviour of these crystals was studied by calculating Vicker’s hardness number. The behaviour of microhardness with applied load was observed to be complex. The electrical behaviour was carried out by calculating dielectric constant at different temperatures and for different frequencies. The dielectric constant (ε/) was found to be strongly dependent on temperature and frequency. The transition metal doping of cadmium in magnesium hydrogen phosphate remarkably decrease the value of dielectric constant from 68 to 23. The transition temperature also decreases from 330ËšC in case of magnesium hydrogen phosphate to 310ËšC in case of cadmium magnesium hydrogen phosphate.
R. K. Goyal; J.N. Sahu
Abstract
High performance polymer nanocomposites based on poly(etheretherketone) (PEEK) as matrix and modified clay as reinforcement were fabricated using hot pressing at 380 °C and 45 MPa. The clay was varied from 0 to 5 wt%. Nanocomposites were characterized by X-ray diffraction (XRD), Vickers hardness ...
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High performance polymer nanocomposites based on poly(etheretherketone) (PEEK) as matrix and modified clay as reinforcement were fabricated using hot pressing at 380 °C and 45 MPa. The clay was varied from 0 to 5 wt%. Nanocomposites were characterized by X-ray diffraction (XRD), Vickers hardness tester, high resistivity meter, and impedance analyzer to get information about morphology, microhardness, electrical conductivity and dielectric properties of nanocomposites, respectively. The experimental density was very close to the theoretical density. XRD showed exfoliation of clay up to 3 wt% and intercalation for 5 wt% nanocomposite. The water absorption decreased by 38 % at 1 wt% clay content. The microhardness increased up to 12 % for 2 wt% clay nanocomposite. Electrical conductivity was increased two orders of magnitude higher than pure PEEK. Dielectric constant was increased slightly with increasing clay content. The significant improvement in properties at lower clay loading might be attributed to the exfoliation of clay in the matrix.
