Thermoelectric properties of co-doped (Bi0.98In0.02)2Te2.7Se0.3 / reduced graphene oxide composites prepared by solid-state reaction

The thermoelectric properties of co-doped (Bi0.98In0.02)2Te2.7Se0.3/reduced graphene oxide composites between 10 - 325 K are presented. X-ray diffraction confirms that the composites adopt a rhombohedral structure with space group R3¯m. Field emission scanning electron microscopy reveals an interface structure of reduced graphene oxide (rGO). N-type conducting behaviour is observed for all the samples, as ascertained by Hall effect and Seebeck coefficient measurements, with a carrier concentration of 1025/m3. The thermal conductivity and electrical resistivity of (Bi0.98In0.02)2Te2.7Se0.3/0.02 wt% reduced graphene oxide composite is found to decrease by 1.6 and 10 times respectively in comparison with that of (Bi0.98In0.02)2Te2.7Se0.3. The power factor is enhanced by 7 times for (Bi0.98In0.02)2Te2.7Se0.3/0.01 wt% rGO compared to that of (Bi0.98In0.02)2Te2.7Se0.3

Structural and optical characterization of novel nitro substituted D-pi-A-pi-A type chalcone single crystal showing second-order and third-order nonlinear optical properties

In this report, nonlinear optical crystal has both second-order and third-order nonlinear optical properties, and crystal is grown by using a slow solvent evaporation technique. The functional groups are identified through spectroscopic technique, and crystal structure is obtained from the refinement and analysis of the single crystal elucidated from single-crystal X-ray diffraction study. Furthermore, the study of linear absorbance has been carried out by using UV/VIS/NIR spectroscopic technique. The presence of defect states were analyzed through photoluminescence study. The electronic contribution parameters of the first order and second-order hyperpolarizability have been calculated from the theoretical approach at the DFT level. The second harmonic generation efficiency (SHG) of (2E)-1-(-3-chlorophenyl)-3-(-4-nitrophenyeprop-2-en-1-one (3CP4NP) has been calculated and compared with the standard material like KDP. Laser damage threshold studies has been performed at 532 nm. Even more, third-order nonlinear optical properties (nonlinear absorption and nonlinear refraction) of 3CP4NP have been carried out from simple and effective Z-scan technique using Q-switched Nd: YAG laser with 532 nm. The optical limiting properties, second-order hyperpolarizability and corresponding third-order nonlinear optical susceptibility of the crystal have been studied in the present investigation

Investigation of thermal conductivity and thermal performance of heat pipes by structurally designed copolymer stabilized ZnO nanofluid

Abstract The present study concentrated on estimating the thermal conductivity, stability, efficiency, and resistance of a heat pipe for heat exchangers, which were essential for many industrial applications. To achieve this, copolymer of amphiphilic poly (styrene-co-2-Acrylamido-2-methylpropane sulfonic acid) poly (STY-co-AMPS) was synthesized by free radical polymerisation technique. The dispersant were used for homogeneous solution and stabilization of ZnO nanofluids. The effect of dispersant on the thermal conductivity of nanofluids was analysed using a KD2 pro thermal property analyser. There is a significant increase in fluid conductivity had a nonlinear relationship with the volume fraction. The maximum enhancement was observed at an optimized concentration of dispersant at 1.5 vol%. Same time, the influence of dispersant agent on the thermal conductivity of nanofluids were compared with linear polyelectrolytes. Further, the experimental values were compared to the existing classical models based on the reasonable aggrement, the prepared nanofluids were employed as a working medium. The conventional screen mesh heat pipe and the temperature distribution to the thermal resistance of the heat pipe was investigated experimentally. The result shows, optimum concentration of dispersants on nanoparticles exhibits an enhanced heat efficiency as compared with the base fluids. Further, the thermal resistance and temperature distribution show decreased behaviour by increasing the particle volume fraction and dispersant concentration

A third-order nonlinear optical single crystal of 3,4-dimethoxy-substituted chalcone derivative with high laser damage threshold value: a potential material for optical power limiting

Third-order nonlinear optical material 4-(1E)-3-(3,4-dimethoxyphenyl)-3-oxoprop-1-en-1-yl]phenyl 4-methylbenzene-1-sulfonate (DMPMS) is crystallized by slow solvent evaporation technique. The crystal has inversion symmetry and belongs to monoclinic system with P2(1)/c space group. The C-H.O/C-H.p intermolecular interactions will be large complementarity for molecular density/crystal packing. A comprehensive investigation for absorbance and emission properties has been performed. Thermal stability is up to 258 degrees C without any weight loss and calculated value of laser damage threshold is approximate to 12 GW/cm(2). The DMPMS shows low dielectric constant value, about 4.42 at 1 MHz and electronic polarizability values in the order of 10(-23) -cm(3). Furthermore, theoretical calculation has been performed using B3LYP and M06-2X functional. The static first-order hyperpolarizability parameter is 55 (B3LYP) and 34 (M06-2X) times that of urea. The total contribution of second-order hyperpolarizability is -37.9 x10(-40) esu (in B3LYP functional) and -25.77 x10(-40) esu (in M06-2X functional), respectively. Here, two-photon absorption mechanism is responsible for nonlinear absorption and co-efficient is found to be 28.3 x 10(-12) m/W. In optical limiting study, limiting threshold is found to be 65 mu J. The real and imaginary third-order nonlinear optical susceptibility is of the order 10(-12) esu

A long-chain based bromo and methyl substituted chalcone derivatives; experimental and theoretical approach on nonlinear optical single crystals

In the present work, growth of single crystals of chalcone derivatives {4-(1E)-3-(4-methylphenyl)-3-oxoprop-1-en-1-yl]phenyl4-methylbenzene -1-sulfonate} ( 4M1PMS) and {4-(1E)-3-(4-bromophenyl)-3-oxoprop-1-en-1-yl]phenyl4-methylbenzene- 1-sulfonate} (4BPMS), at room temperature is reported. The spectroscopic techniques are used to identify the presence of functional groups in the materials. The single-crystal XRD and powder XRD analysis reveals that 4M1PMS belongs to non-centrosymmetric (P2(1)2(1)2(1)) and 4BPMS belongs to centrosymmetric (P2(1)/n) crystalline system. The molecular structures exhibit C-H center dot center dot center dot O and pi center dot center dot center dot pi intermolecular interactions. From UV/VIS/NIR spectroscopic studies, it is found that both samples have bathochromic shifts in linear absorbance (cut-off region) spectra. The broad emission region involved in several sharp emission peaks in blue region, exhibits a blue light emission property, as observed from photoluminescence study, in both the samples. The thermal stability of the materials were studied by TGA/DTA techniques and crystals were thermally stable until the melting point. In NLO study, 4M1PMS crystal has shown SHG efficiency 2.2 times that of KDP crystal. In addition, electronic contribution in hyperpolarizability (first order and second order) tensors of both the compounds were computed theoretically by M06-2X functional at DFT level. The open/closed aperture Z-scan technique were performed to evaluate third order nonlinear optical materials by measuring experimental parameters such as nonlinear absorption/refraction and calculate second-order hyperpolarizability with corresponding third-order nonlinear optical susceptibility (chi((3))) of 4M1PMS and 4BPMS. The surface damage threshold studies of 4M1PMS and 4BPMS were performed by Q-switched Nd:YAG laser at 532 nm