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Open Access
Study for the thermodynamic properties of nanomaterials under varying conditions of size, shape, pressure and temperature
(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2017-07) Bhatt, Sandhya; Munish Kumar
Present thesis is an attempt to develop a unified theoretical model based on thermodynamic theory of solids to study the thermodynamic properties of nanomaterials under varying conditions of state parameters like pressure and temperature as well as on size and shape. We extended the bond energy model to study the effects of size and shape on melting and superheating for free-standing and embedded nanomaterials. Melting temperature of free standing nanomaterials decreases with the reduction of particle size whereas a reverse trend was found for embedded nanomaterials. A single model was found sufficient to explain both the phenomena. Then, the model was used to explain the specific heat and thermal conductivity of different nanomaterials for spherical as well as polyhedral shapes. Debye temperature and Raman frequency have been predicted successfully for different nanomaterials with spherical, wire and film shapes. Debye temperature, Raman frequency and thermal conductivity decrease with decreasing size whereas specific heat increases. Different models proposed for compression of solids have been modified. The effects of size, shape and temperature have been studied for density of nanoscale materials. Density decreases with the effect of size and shape. However, these effects were found obvious in low size range. A Model has also been developed to study the thermodynamic and elastic properties of nanominerals with the incorporation of size and shape which is also applicable for their bulk counterparts. The results obtained were found in fair agreement with the available experimental and simulation data thereby supporting the validity and applicability of formulations developed. To explain different cases using single model is the dream of researchers and in this thesis we made an attempt to make this dream true. The model predictions may be useful for future studies on nanomaterials.
Open Access
Studies on graphite based magnetic nano-composites
(G.B. Pant University of Agriculture and Technology, Pantnagar (Uttarakhand), 2016-12) Versha Rani; Srivastava, R.C.
Synthesis of composite systems with superparamagnetic and graphitic nanostructures is highly demanding due to their extensive applications in various fields. In the present work graphite (G) and graphene-oxide (GO) were used as fillers and magnetite (Fe3O4) NPs were used as matrix to form the graphite based magnetic nano-composites. All the samples were synthesized via the chemical coprecipitation method. Samples were characterized by XRD, FTIR, SEM, TGA/DTG, UV-Vis and VSM. The DC electrical conductivities, as a function of temperature were measured by using four probe method for various voltage compliances (1 V, 10 V and 100 V). Dielectric measurements were performed for the frequency range 500Hz-1MHz. The co-existence of both phases of G/GO and ferrite NPs were confirmed by XRD diffraction and FTIR. The addition of G and GO induced a surprising reduction in the crystallite size of ferrite NPs ranging 17.50 to 12 nm with retained cubic structure. The surface morphology of the samples were investigated by SEM. Fe3O4 NPs were found spherical in shape with a narrow particle size distribution. The grains could not be appeared clearly for the composites. TGA/DTG analysis indicated that all the samples showed the one step thermal decomposition behavior except G and GO. The thermal stability of the composite samples was found to increase with the addition of ferrite NPs into it. All the samples exhibited superparamagnetism at the room temperature. By the addition of G/GO into the ferrite NPs, the saturation magnetization was found to be reduced. The dielectric constant (ε’), loss tangent (tanδ) and loss factor (ε’’) rapidly decreased for the lower frequency range and reached a constant value for the high frequency range. The dielectric constant for composites get enhanced with the ferrite NPs. DC electrical conductivities for all the samples were found to increase with the increasing temperature. Composite samples showed the semiconducting nature. By adding G/GO, optical band gap of the samples were found to decrease. These results remark that graphitic nanocomposites have great potential for magnetic, capacitive and microwave absorption applications.
Open Access
Study for the effect of size, shape and pressure on thermophysical properties
(G.B. Pant University of Agriculture and Technology, Pantnagar (Uttarakhand), 2016-12) Arora, Neha; Joshi, Deepika P.
Present study is an effort to understand the effect of size, shape and pressure on thermophysical properties of nanomaterials. Thermodynamic properties like melting temperature, cohesive energy, vacancy formation energy and Debye temperature of nano metals for spherical and non spherical nanoparticles with different size have been studied. Effect of cross-sectional shape on melting temperature of metallic nanowires has also been observed. It was found that these thermal properties show decreasing trend with decrement in size of the nanomaterial. The obtained results also revealed that shape of the nanomaterial plays a vital role to affect the thermodynamic properties. We have extended our model for investigating effect of size and pressure on bulk modulus and melting of the nanometals, a general equation for melting has been derived. It is found that as the pressure increases there is the elevation in the melting temperature of nanometals. Under pressure melting temperature of small sized nanoparticles increases with the decrement of size. We have not only provided a pathway to study the thermophysical properties of nanometals but also studied some important properties of semiconductors at nanorange. A quantitative thermodynamic model for thermal conductivity and diffusivity of semiconductors was established considering surface scattering effects and atomic thermal vibrations with different size and dimension. Thermal conductivity and diffusivity of semiconducting nanomaterials with partially smooth and partially rough surfaces of different sizes and dimension have been calculated. Besides this a fresh approach has been proposed to study band gap of nanowires by incorporating shape effect with size. The results obtained are compared with the available simulated and experimental data. It is concluded that computed results are in close agreement with the experimental data, which supports the validity of present work.
Open Access
Study of thermo-elastic properties of nanomaterials under high pressure and high temperature
(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2008-05) Jeewan Chandra; Gupta, B.R.K.
T he study based on the EOS at high-pressure and high temperature is of fundamental interest because they permit interpolation and extrapolation in to the regions in which the experimental data are not available adequately. The Present work describes the theoretical study of thermo-elastic properties especially compression, thermal expansion, bulk modulus, thermal expansion coefficient of some of the nanomaterials by making use of Equation of State. For different class of solids a lot of numbers of equation of states are available. Among the number of isothermal and isobaric EOS described earlier, we prefer isothermal Usual Tait’s Equation of State (UTE) and isobaric Singh and Gupta Integral form of Equation of State (IFEOS) because of their simple and straightforward applications in high pressure and high temperature physics. We have reported the results obtained for thermo physical properties of nanomaterials i.e. n-SnO2, n-CeO2, n-PbS, n-MgO, nCuO, n-AlN, n-ZnO, n-NiO, n-TiO2, n-Ni, n-Ti, n-(Ni+Fe), n-Mo, individual single wall carbon nanotube (SWCNT), under effect of high temperatures and high pressures. The variation of compression (V/V0), isothermal bulk modulus (KT) and relative isothermal expansion coefficient ǂ(P)/ǂ0) with pressure have plotted and shown in tables, for nanocrystalline n-SnO2 with three particle sizes 3nm, 8nm and 14nm, n-CeO2, nanocrystalline MgO ( 100nm and 200nm), n-CuO, n-PbS ( 2.6nm, 5.4nm and 8.8nm), n-Ni(20nm and 62nm), n-Mo and n-AlN n-TiO2( 35nm and 6nm) and nZnO using Usual Tait’s equation of state. We have also calculated temperature dependence of thermal expansivity (ǂT), relative volume thermal expansion (V/V0) and bulk modulus (KT) of nanomaterials { n-ZnO, n-TiO2 anatase, n-NiO, n-Ni, n(Ni+Fe), n-Ti, and SWCNT(armchair CNT (5, 5), and zig-zag CNT (9, 0); both in axial as well as radial directions)}using IFEOS at different temperature and atmospheric pressure. The Integral form of Equation of State( IFEOS) is entirely free from the use of potentials and need only three input parameters such as Anderson Gruneisen parameter( 0 Tǅ ), volume thermal expansion coefficient(ǂ0) at zero pressure, reference temperature, and the thermo-elastic parameter k which can be calculated from the slope of the graph between log(ǅT) and log(T/T0). The calculated values are plotted with temperature and compared to available experimental data in order to compare the present results. All the results have been presented graphically. It may be noted here that the calculated values are in close agreement to the experimental data. Thus it is emphasized here that the Integral form of Equation of State (IFEOS) and Usual Taits Equation of State(UTE) successfully explains the thermo-elastic properties nanomaterials.
Open Access
Influence of the third dimension on the electronic spectra and out-of-plane transport behaviour in bilayered high Tc cuprates in normal state
(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2008-01) Tewari, Bhagya Sindhu; Ajay
Open Access
Study of thermophysical properties of different class of solids under high pressure and high temperature
(G.B. Pant University of Agriculture and Technology, Pantnagar (Uttarakhand), 2005) Devlal, Kamal; Gupta, B.R.K.
Open Access
Heavy ion irradiation induced effects on MgB2 thin films
(Govind Ballabh Pant University of Agriculture and Technology;Pantnagar, 2006) Ravindra Kumar; Agrawal, H.M.
Open Access
Study of mechanical properties of nanomaterials under high temperature and high pressure
(Govind Ballabh Pant University of Agriculture and Technology;Pantnagar, 2006) Srivastava, Ajeet Kumar; Gupta, B.R.K.
Open Access
Study of the spectral properties of layered high Tc Cuprate superconductors
(G.B.Pant University Of Agriculture And Technology Pantnagar : Uttaranchal, 2005) Pathak, Kumar Pradeep; Ajay

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