Sandra Afflerbach; Reinhard Trettin
Abstract
A major scientific challenge for carbon neutral, environmental friendly future energy production is the development of renewable energy production to technological readiness. One example are solar thermal power plants. Since their energy generation is intermittent, they demand for a feasible storage ...
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A major scientific challenge for carbon neutral, environmental friendly future energy production is the development of renewable energy production to technological readiness. One example are solar thermal power plants. Since their energy generation is intermittent, they demand for a feasible storage solution for which thermochemical reaction systems are considered. The present work subjects the thermochemical reaction system CaO / Ca(OH)2 and its structural-mechanical correlations impacting the powder bulk performance upon thermochemical cycling. On exemplified Ca(OH)2 crystals is shown, that during the first de- and rehydration process, the entire crystal morphology is disintegrated. The underlying mechanism is evaluated by theoretical considerations on the layered structure of Ca(OH)2 and validated by scanning electron microscopy (SEM) on the probed material before and after dehydration as well as after rehydration. The obtained findings are transferred to the technically relevant powdery storage material, where they are capable to explain the phenomenon of agglomeration, which is proven by measurement of secondary particle size distribution over a number of ten thermochemical reaction cycles. From SEM imaging performed on the samples it is found, that agglomerates consist of cohering smaller particles. The inferred insights can help to deduce necessary amendments of reactor design or material modification also for other thermochemical reaction systems.
R. Tholkappiyan; Fathalla Hamed; K. Vishista
Abstract
Lanthanum (La3+) ion doped zinc ferrite nanoparticles were synthesized by combustion method using glycine as fuel. The as-synthesized ZnFe1.96La0.04O4 nanoparticles were subjected to annealing temperature of 900 oC for time intervals of 2 h, 6 h, 12 h, 24 h and 48 h. The as-synthesized and annealed ZnFe1.96La0.04O4 nanoparticles ...
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Lanthanum (La3+) ion doped zinc ferrite nanoparticles were synthesized by combustion method using glycine as fuel. The as-synthesized ZnFe1.96La0.04O4 nanoparticles were subjected to annealing temperature of 900 oC for time intervals of 2 h, 6 h, 12 h, 24 h and 48 h. The as-synthesized and annealed ZnFe1.96La0.04O4 nanoparticles were characterized as a single phase with normal spinel structure. The surface morphology of these nanoparticles were found to be non–uniform and agglomerated with fine pores/voids. The induced strain and dislocation density were reduced with increasing annealing time which enhanced crystallinity and increased grain size. The values of optical band gap calculated from UV/Vis/NIR spectra of the as-synthesized and annealed ZnFe1.96La0.04O4 nanoparticles were found to decrease with increasing annealing time. They range from 2.48 to 2.19 eV from the simple method and 2.42–2.12 eV for direct and 1.87–1.71 eV for indirect from Kubelka–Munk function method. The optical band gap in ZnFe1.96La0.04O4 nanoparticles can be tuned as function of varying annealing time and it seems to correlate with induced strains in the nano-crystallites. Therefore, the tuning of optical band gap with just changing the heating treatment of ZnFe1.96La0.04O4 nanoparticles may make them suitable photocatalysis.
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 .
Shweta Thakur; Seema Sharma;Ashutosh Tiwari; Radheshyam Rai
Abstract
Polycrystalline samples of (K0.45Na0.45Li0.1NbO3)1-x-(Ba0.96La0.04Ti0.815Mn0.0025 Nb0.0025Zr0.18 O3)x ceramics (where x = 0.1, 0.3, 0.5, 0.7 and 0.9) were prepared by using a high temperature solid state reaction technique. The XRD patterns of the BLTMNZ doped KNLN at room temperature with x = 0.7 have ...
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Polycrystalline samples of (K0.45Na0.45Li0.1NbO3)1-x-(Ba0.96La0.04Ti0.815Mn0.0025 Nb0.0025Zr0.18 O3)x ceramics (where x = 0.1, 0.3, 0.5, 0.7 and 0.9) were prepared by using a high temperature solid state reaction technique. The XRD patterns of the BLTMNZ doped KNLN at room temperature with x = 0.7 have pure pervoskite phase with tetragonal structure at room temperature and have maximum value of dielectric constant at x = 0.9. Detailed studies of dielectric and impedance properties of the materials in a wide range of frequency (100Hz–1MHz) and temperatures (30 – 500 o C) showed that properties are strongly temperature and frequency dependent. The plots of Zʹʹ and Mʹʹ versus frequency at various temperatures show peaks in the higher temperature range (>300 o C). The compounds show dielectric relaxation, which is found to be of non-Debye type and the relaxation frequency shifted to higher side with increase in temperature. The Nyquist plot and conductivity studies showed the NTCR character of samples.
S. Subbarayudu; V. Madhavi;S. Uthanna
Abstract
MoO3 films were deposited on Corning glass and silicon substrates held at room temperature (303 K) by RF magnetron sputtering of metallic molybdenum target at a fixed oxygen partial pressure of 4x10 -4 mbar and sputter pressure of 4x10 -2 mbar. The as deposited films were annealed in air at different ...
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MoO3 films were deposited on Corning glass and silicon substrates held at room temperature (303 K) by RF magnetron sputtering of metallic molybdenum target at a fixed oxygen partial pressure of 4x10 -4 mbar and sputter pressure of 4x10 -2 mbar. The as deposited films were annealed in air at different temperatures in the range 473 – 673 K. X-ray diffraction studies suggest that the as-deposited and the films annealed at 473 K were amorphous in nature, while those annealed at 573 and 673 K were polycrystalline with mixed phases of α- orthorhombic and β- monoclinic MoO3. Scanning electron microscope images of the films annealed at 573 and 673 K exhibited nanoflower like and nanodisk like structures due to improvement in the crystallinity. Fourier transform infrared studies showed the characteristic vibrations of MoO3 with shift in the vibrational modes of Mo = O and Mo – O – Mo with increase of annealing temperature. The optical absorption edge of the films shifted towards lower wavelengths side with increase of annealing temperature. Optical band gap of as-deposited films was 2.98 eV with refractive index 2.01, while those annealed at 673 K showed the optical band gap of 3.15 eV and refractive index of 2.08. The MoO3 films annealed at 673 K were of nanocrystalline with crystallite size of 39 nm with optical band gap of 3.15 eV and refractive index of 2.08 were favorable for electron blocking and hole-selective layers in bulk-heterojuction solar cells.
S.P. Dalawai; A.B. Gadkari; T.J. Shinde; P.N. Vasambekar
Abstract
Cadmium ferrite was prepared by standard ceramic method and characterized by XRD, IR and SEM techniques. The X-ray analysis confirms the formation of single phase cubic spinel structure. The lattice constant decreases slightly and porosity increases with increase in sintering temperature. The crystallite ...
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Cadmium ferrite was prepared by standard ceramic method and characterized by XRD, IR and SEM techniques. The X-ray analysis confirms the formation of single phase cubic spinel structure. The lattice constant decreases slightly and porosity increases with increase in sintering temperature. The crystallite size of the samples lies in the range of 22.83 to 24.44 nm. The IR study shows two absorption bands around 400 cm -1 and 600 cm -1 corresponding to octahedral and tetrahedral sites respectively. The grain size increases and switching field decreases with increases in sintering temperature.
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