Sumit Sharma; Pramod Kumar; Ajay Kumar Diwakar
Abstract
Nowadays there is a requirement of material that has high thermal conductivity as well as suitable electric insulating properties. Such materials are required in industries where thermal management is desirable but electrical conductivity is not required, such as substrates for electronic components ...
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Nowadays there is a requirement of material that has high thermal conductivity as well as suitable electric insulating properties. Such materials are required in industries where thermal management is desirable but electrical conductivity is not required, such as substrates for electronic components and solar panels. In this study, the multi-scale modeling of epoxy (bisphenol-A) reinforced alumina composite has been performed using BIOVIA Materials Studio and Abaqus. Modeling has been done for varying volume fraction (Vf) of alumina. The properties predicted are the thermal conductivity and Young’s modulus. Heat transfer analysis has been done using Abaqus/Explicit. It was found that the thermal conductivity first increased till Vf = 20% and then decreased. When the concentration of alumina was increased further after Vf = 20%, the orientation of alumina particles changed from being in-plane to random, resulting in a fall in the values of thermal conductivity. In the silicon/insulator plate system, there was found to be an accumulation of heat resulting in a decrease in temperature on the bottom surface of the insulator plate. Thus, more time was taken for the heat to conduct through this system. Whereas, when the heat was transferred through the system of silicon/composite plate, no accumulation of heat in the system was observed.
Faizan Ahmad; Rashmi Singh; Rachana Kumar; Mukesh Jewariya; Chandra Shekhar; Naresh Kumar; Pramod Kumar
Abstract
The wavelength and time delay dependent reflection spectra of nano crystals Bi2Se3, Bi2Te3 and Bi2Te2Se were studied for ultrafast dynamics, using pump and probe spectroscopy. We observed only one transient peak for Bi2Se3 below 600nm, which decreases linearly with time delay. Three transient ...
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The wavelength and time delay dependent reflection spectra of nano crystals Bi2Se3, Bi2Te3 and Bi2Te2Se were studied for ultrafast dynamics, using pump and probe spectroscopy. We observed only one transient peak for Bi2Se3 below 600nm, which decreases linearly with time delay. Three transient sharp peaks were observed for Bi2Te3 for wavelength dependent graph, which reveals about the ultrafast dynamics of charge carrier. We also observed oscillations in Bi2Se3 crystal above 600 nm which was absent in Bi2Te3 sample. Bi2Te2Se showed a single transient spectrum peak at 482 nm with the highest peak for 103ps time delay. The curve fitted Time resolve (TR) trace for both Bi2Se3 and Bi2Te3 crystals at 492 nm wavelength, revealed almost the same results for rise and decay time.
Pramod Kumar; Rashmi Singh; L. D. Sanjeewa; Rachana Kumar
Abstract
In this paper, structural, magnetic and heat capacity of M2Fe2O(AsO4)2 compounds have been reported. Most interestingly, the magnetization at very low fields a complete negative magnetization was observed in both field cooling and zero field cooling in K2Fe2O(AsO4)2 and Rb2Fe2O(AsO4)2 compounds ...
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In this paper, structural, magnetic and heat capacity of M2Fe2O(AsO4)2 compounds have been reported. Most interestingly, the magnetization at very low fields a complete negative magnetization was observed in both field cooling and zero field cooling in K2Fe2O(AsO4)2 and Rb2Fe2O(AsO4)2 compounds whereas field cooled is positive in KCsFe2O(AsO4)2. A possible mechanism for the observed peculiar magnetic behavior is discussed, related to the competition of the single-ion magnetic anisotropy and the antisymmetric magnetization behavior in two crystallographically different FeO6 centers. We estimated the gap (D) opening at low temperature K2Fe2O (AsO4)2 KCs2Fe2O (AsO4)2 and Rb2Fe2O (AsO4)2, are 23.6 K, 23.9 K and 25 K respectively from heat capacity. Magnetic part of heat capacity at low temperatures follows the T 3 dependence, indicates that the low temperature magnetic state in all these compounds are antiferromagnetic.
Rashmi Singh; Puneet Jain; Rachana Kumar; Pramod Kumar
Abstract
Magnetic properties of TbRu2Ge2 were studied. TbRu2Ge2 shows unusual magnetism, i.e. at low field it shows frustration (like spin glass) and at high field, this frustration starts to disappear. It has been found that TbRu2Ge2 has a TN of 37K. To confirm the frustration in TbRu2Ge2, AC susceptibility ...
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Magnetic properties of TbRu2Ge2 were studied. TbRu2Ge2 shows unusual magnetism, i.e. at low field it shows frustration (like spin glass) and at high field, this frustration starts to disappear. It has been found that TbRu2Ge2 has a TN of 37K. To confirm the frustration in TbRu2Ge2, AC susceptibility and normalized magnetization calculations were also performed .
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