This work demonstrates the Electromagnetic interference shielding(EMI) & corrosion resistance of ... more This work demonstrates the Electromagnetic interference shielding(EMI) & corrosion resistance of conducting polyaniline (PANI)-Magnetic nanoparticles like Ni ferrite and Fe3O4 composite was investigated and this study shows that efficient and lightweight polymer film materials.The EMI shielding effectiveness was analyzed in the X-band (8.2-12.4GHz), among this composite Ni ferrite shows better corrosion resistance and shielding effectiveness (10dB).
Abstract High-energy mechanical milling was used to prepare Cu and W nanopowders. Cylindrical pre... more Abstract High-energy mechanical milling was used to prepare Cu and W nanopowders. Cylindrical preforms with initial theoretical density of 86% were prepared using a die and punch assembly. The preforms were sintered in a muffle furnace and subsequently furnace cooled and then the hot specimens were extruded to attain 93% theoretical density. Differential Scanning Calorimetry and Thermal Gravimetric Analyzer, four point probe tester, Scanning Electron Microscope and pin on-disc system were used to evaluate the thermal, electrical conductivity, characterization and tribological property of Cu–W composite respectively and using curve fitting method the respective polynomial and power law model were developed. The results indicated that the wear rate decreased with increasing applied load and sliding distance. The composites were tested at high sliding speed which exhibited high value of coefficient of friction.
Spectrally selective Al x O y /Al/Al x O y multilayer absorber coatings were deposited on copper ... more Spectrally selective Al x O y /Al/Al x O y multilayer absorber coatings were deposited on copper (Cu) and molybdenum (Mo) substrates using a pulsed sputtering system. The Al targets were sputtered using asymmetric bipolar-pulsed DC generators in Ar+O 2 and Ar plasmas to deposit an Al x O y /Al/Al x O y coating. The compositions and thicknesses of the individual component layers were optimized to achieve high solar absorptance (a ¼ 0.950-0.970) and low thermal emittance (e ¼ 0.05-0.08). The X-ray diffraction data in thin film mode showed an amorphous structure of the Al x O y /Al/Al x O y coating. The X-ray photoelectron spectroscopy data of the Al x O y /Al/Al x O y multilayer absorber indicated that the Al x O y layers present in the coating were non-stoichiometric. The optical constants (n and k) of the multilayer absorber were determined from the spectroscopic ellipsometric data. Drude's free-electron model was used for generating the theoretical dispersion of optical constants for Al films, while the Tauc-Lorentz model was used for modeling optical properties of the dielectric Al x O y layers. In order to study the thermal stability of the Al x O y /Al/Al x O y coatings, they were subjected to heat treatment (in air and vacuum) at different temperatures and durations. The multilayer absorber deposited on Cu substrates exhibited high solar selectivity (a/e) of 0.901/0.06 even after heat-treatment in air up to 400 1C for 2 h. At 450 1C, the solar selectivity decreased significantly on Cu substrates (e.g., a/e ¼ 0.790/0.07). The coatings deposited on Mo substrates were thermally stable up to 800 1C in vacuum with a solar selectivity of 0.934/0.05. The structural stability of the absorber coatings heat treated in air (up to 400 1C) and vacuum (up to 800 1C) was confirmed by micro-Raman spectroscopy measurements. Studies on the accelerated aging tests suggested that the absorber coatings on Cu were stable in air up to 75 h at 300 1C and the service lifetime of the multilayer absorber was predicted to be more than 25 years. Further, the activation energy for the degradation of the multilayer absorber heat treated for longer durations in air is of the order of 64 kJ/mol.
Solar selective coatings of HfO x /Mo/HfO 2 were deposited on copper (Cu) and stainless steel (SS... more Solar selective coatings of HfO x /Mo/HfO 2 were deposited on copper (Cu) and stainless steel (SS) substrates using a magnetron sputtering system. The HfO x and HfO 2 layers were deposited from the sputtering of Hf target in Ar+O 2 plasma using an asymmetric bipolar-pulsed direct current generator. Whereas, the Mo layer was deposited from the sputtering of Mo target in the Ar plasma. The optimized HfO x /Mo/HfO 2 multilayer absorber on Cu substrate exhibited high solar absorptance (α = 0.905-0.923) and low thermal emittance (ε = 0.07-0.09). Similarly, on SS substrates the optimized coatings exhibited α and ε in the ranges of 0.902-0.917 and 0.15-0.17, respectively. The X-ray diffraction data showed that the HfO x /Mo/HfO 2 coating consists of tetragonal and monoclinic phases of HfO 2 , which was confirmed by micro-Raman spectroscopy data. The bonding structure of the HfO x and the HfO 2 layers were confirmed using X-ray photoelectron spectroscopy data. The optical constants (n and k), measured using spectroscopic ellipsometry, showed that the top HfO 2 layer acts as an antireflection coating and the bottom two layers (HfO x and Mo) are the main absorber layers. The analysis of the spectroscopic a)
ABSTRACT A new HfMoN(H)/HfMoN(L)/HfON/Al2O3 tandem absorber is designed and developed for high te... more ABSTRACT A new HfMoN(H)/HfMoN(L)/HfON/Al2O3 tandem absorber is designed and developed for high temperature solar thermal applications. The first absorber layer, HfMoN(H) is designed to have higher metallic content than the second HfMoN(L) layer. By varying the nitrogen flow rate, two different HfMoN layers with different refractive indices were deposited on SS substrates. The optical constants (n and k) measured using spectroscopic ellipsometry showed that HfMoN(H) and HfMoN(L) are the main absorber layers and HfON/Al2O3 acts as a double layer antireflection coating. The gradual decrease in the refractive indices from the substrate to the top resulted in increase in the absorptance, which was confirmed by the ellipsometric measurements. The optimized four layer tandem absorber exhibited high absorptance (α=0.94–0.95) and low thermal emittance (ε82 °C=0.13–0.14). The four layer tandem absorber was thermally stable up to 600 °C for 450 h and 650 °C for 100 h in vacuum. Whereas, coatings heat-treated in air were thermally stable up to 475 °C for 34 h.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
A number of carbon substituents possessing various functional groups could be introduced onto aro... more A number of carbon substituents possessing various functional groups could be introduced onto aromatic nitro compounds using dimethyl malonate as a one-carbon source and linker. Decarboxylation of both the ester groups originating from dimethyl malonate in this methodology is particularly significant.
Furan derivatives R 0060 Synthesis of Substituted Butenolides by the Ring Closing Metathesis of T... more Furan derivatives R 0060 Synthesis of Substituted Butenolides by the Ring Closing Metathesis of Two Electron Deficient Olefins: A General Route to the Natural Products of Paraconic Acids Class.-Ring-closing metathesis of highly electron-deficient dienes derived from Baylis-Hillman adducts gives butenolides in good yields. Derivative (IIc) serves as starting material for the synthesis of racemic phaseolinic acid (III).
2-Arylpropenoic acids signify a medicinally important class of non-steroidal anti-inflammatory ag... more 2-Arylpropenoic acids signify a medicinally important class of non-steroidal anti-inflammatory agents. 1 2-Arylpropenoic acids possessing nitro groups in their aromatic rings such as 2 are potential starting materials for the preparation of several analgesic and anti-inflammatory ...
Carbazole derivatives Carbazole derivatives R 0150 An Efficient Total Synthesis of 9-Methoxycarba... more Carbazole derivatives Carbazole derivatives R 0150 An Efficient Total Synthesis of 9-Methoxycarbazole-3-carbaldehyde Based on a Novel Methodology for the Preparation of Methoxyindoles.-The synthesis of the naturally occurring aldehyde (X), based on a recently reported methodology for the preparation of 1-methoxyindoles, is reported. Furthermore, a benzannulation strategy is employed using ring-closing metathesis as the key step.
... 207257. 6. RM Acheson, PG Hunt, DM Littlewood, BA Murrer and HE Rosenberg, J. Chem. Soc., Pe... more ... 207257. 6. RM Acheson, PG Hunt, DM Littlewood, BA Murrer and HE Rosenberg, J. Chem. Soc., Perkin Trans. ... Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (47). 9. N Selvakumar, B Yadi Reddy, G Sunil Kumar and J Iqbal, Tetrahedron Lett. ...
A new spectrally selective NbAlN/NbAlON/Si 3 N 4 tandem absorber was deposited on copper substrat... more A new spectrally selective NbAlN/NbAlON/Si 3 N 4 tandem absorber was deposited on copper substrates using a reactive direct current magnetron sputtering system. A high solar absorptance (0.956) and a low emittance (0.07) were achieved by gradually decreasing the refractive index from the substrate to the surface. The tandem absorber was characterized using solar spectrum reflectometer and emissometer, X-ray photoelectron spectroscopy, phase-modulated spectroscopic ellipsometry, atomic force microscopy and micro-Raman spectroscopy techniques. In order to study the thermal stability of the tandem absorbers, they were subjected to heat treatment (in air and vacuum) at different durations and temperatures. The tandem absorber deposited on copper substrate exhibited high solar selectivity in the order of 13-15 even after heat treatment in air up to 500 1C for 2 h. These tandem absorbers also exhibited high thermal stability (450 1C) in air for longer durations (116 h). The onset of oxidation for the tandem absorber deposited on silicon substrates was 650 1C, indicating a high oxidation resistance. The results of the present study indicate the importance of NbAlN/NbAlON/Si 3 N 4 tandem absorber for high-temperature solar selective applications.
Spectrally selective TiAlN/AlON tandem absorbers were deposited on copper and stainless steel sub... more Spectrally selective TiAlN/AlON tandem absorbers were deposited on copper and stainless steel substrates using a reactive DC/RF magnetron sputtering system. The compositions and thicknesses of the individual component layers were optimized to achieve high absorptance (a ¼ 0.931-0.942) and low emittance (e ¼ 0.05-0.06) on copper substrate. The experimental spectroscopic ellipsometric data have been fitted with the theoretical models to derive the dispersion of the optical constants (n and k). In order to study the thermal stability of the tandem absorbers, they were subjected to heat treatment (in air and vacuum) for different durations and temperatures. The tandem absorber deposited on Cu substrates exhibited high solar selectivity (a/e) of 0.946/0.07 even after heat treatment in air up to 600 1C for 2 h. At 625 1C, the solar selectivity decreased significantly on Cu substrates (e.g., a/e ¼ 0.924/ 0.30). The tandem absorber on Cu substrates was also stable in air up to 100 h at 400 1C with a solar selectivity of 0.919/0.06. Studies on the accelerated aging tests indicated that the activation energy for the degradation of the tandem absorber is of the order of 100 kJ/mol.
Thin films of TiO 2 were grown on n-type Si substrate by thermal oxidation of Ti films deposited ... more Thin films of TiO 2 were grown on n-type Si substrate by thermal oxidation of Ti films deposited by dc sputtering. The phase purity of TiO 2 was confirmed by Raman spectroscopy, and secondary ion mass spectroscopy was used to analyze the interfacial and chemical composition of ...
Approximately 1.8 m thick nanolayered multilayer coatings of TiN/CrN (also known as superlattice... more Approximately 1.8 m thick nanolayered multilayer coatings of TiN/CrN (also known as superlattices) were deposited on silicon (100) substrates at different modulation wavelengths (4.6-12.8 nm), substrate temperatures (50-400 °C) and substrate bias voltages (-50 to-200 V) using a reactive direct current magnetron sputtering system. X-ray reflectivity (XRR) technique was employed to determine various properties of the multilayers such as interface roughness, surface roughness, electron density, critical angle and individual layer thicknesses. The modulation wavelengths of the TiN/CrN superlattice coatings were calculated using modified Bragg's law. Furthermore, the experimental X-ray reflectivity patterns were simulated using theoretically generated patterns and a good fit was obtained for a three layer model, i.e., (1) top surface roughness layer, (2) TiN/CrN multilayer coating (approximately 1.8 m) and (3) Ti interlayer (~ 0.5 m) at the film-substrate interface. For the superlattice coatings prepared at a modulation wavelength of 9.7 nm, a substrate bias of-200 V and a substrate temperature of 400 C the XRR patterns showed Bragg reflections up to 5 th order, indicating well-defined a)
We have designed and developed an indigenous ultra high vacuum (UHV) sputtering system which can ... more We have designed and developed an indigenous ultra high vacuum (UHV) sputtering system which can deposit magnetic thin films with high purity and good uniformity. The equipment consists of state-of the-art technologies and sophistication. With this system it is possible to deposit coatings of various materials on a sample size of 3"3" 3". The Ni 81 Fe 19 ferromagnetic thin films, with Tantalum (Ta) as a buffer and cap layers have been deposited on silicon substrates using this ultra high vacuum (UHV) sputtering system. The magneto transport measurement study indicated a significant variation in the AMR values of the films for varying thicknesses of tantalum and NiFe layers.
Some novel oxazolidinone derivatives with benzotriazole as pendant have been synthesized and test... more Some novel oxazolidinone derivatives with benzotriazole as pendant have been synthesized and tested for antibacterial activity. Linearly attached benzotriazole derivative showed more potency compared to angular one in vitro. Out of E/Z-isomers of angularly attached derivatives E-isomer was found to be more potent than Z-isomer. Either less active or inactive molecules were obtained, when benzotriazole was replaced with benzimidazole, benzthiazole, or benzoxazole. Finally, thioacetamide analogue of linear compound gave a lead having activity similar to linezolid in vitro.
A series of conformationally constrained analogues of Linezolid were synthesised by employing a t... more A series of conformationally constrained analogues of Linezolid were synthesised by employing a tandem SN(2) and SNAr reaction as the key step and tested for antibacterial activity. While the hexahydroazolo-quinoxaline compounds were inactive, the tetrahydroazolo-benzothiazine compounds exhibited interesting antibacterial activity. The introduction of fluorine in the aromatic ring further made the compounds more potent in acetamide compounds resulting in an interesting analogue 32. However, the introduction of fluorine (analogue 34) on the already potent non-fluorine thiocarbamate 21 did not have any influence on the activity.
The syntheses of a number of novel oxazolidinone analogues possessing an urea functionality are r... more The syntheses of a number of novel oxazolidinone analogues possessing an urea functionality are reported. While the urea derivatives possessing aliphatic and aromatic groups were prepared by the more conventional isocyanate method, the derivatives possessing heterocyclic rings were synthesized by a relatively uncommon but otherwise efficient carbamate chemistry. Though the SAR resulted in novel compounds possessing in vitro activity equivalent to Linezolid, the compounds possess a range of substituents that are amenable for altering physicochemical properties of the resultant drug. The antibacterial activity was found to be not sensitive to the functional groups attached to the urea site regardless of the size and electronic characteristics. Based on in vivo results, one molecule has been identified as a candidate and additional work such as salt selection, scale-up, etc., are currently underway to take the molecule further through development.
This work demonstrates the Electromagnetic interference shielding(EMI) & corrosion resistance of ... more This work demonstrates the Electromagnetic interference shielding(EMI) & corrosion resistance of conducting polyaniline (PANI)-Magnetic nanoparticles like Ni ferrite and Fe3O4 composite was investigated and this study shows that efficient and lightweight polymer film materials.The EMI shielding effectiveness was analyzed in the X-band (8.2-12.4GHz), among this composite Ni ferrite shows better corrosion resistance and shielding effectiveness (10dB).
Abstract High-energy mechanical milling was used to prepare Cu and W nanopowders. Cylindrical pre... more Abstract High-energy mechanical milling was used to prepare Cu and W nanopowders. Cylindrical preforms with initial theoretical density of 86% were prepared using a die and punch assembly. The preforms were sintered in a muffle furnace and subsequently furnace cooled and then the hot specimens were extruded to attain 93% theoretical density. Differential Scanning Calorimetry and Thermal Gravimetric Analyzer, four point probe tester, Scanning Electron Microscope and pin on-disc system were used to evaluate the thermal, electrical conductivity, characterization and tribological property of Cu–W composite respectively and using curve fitting method the respective polynomial and power law model were developed. The results indicated that the wear rate decreased with increasing applied load and sliding distance. The composites were tested at high sliding speed which exhibited high value of coefficient of friction.
Spectrally selective Al x O y /Al/Al x O y multilayer absorber coatings were deposited on copper ... more Spectrally selective Al x O y /Al/Al x O y multilayer absorber coatings were deposited on copper (Cu) and molybdenum (Mo) substrates using a pulsed sputtering system. The Al targets were sputtered using asymmetric bipolar-pulsed DC generators in Ar+O 2 and Ar plasmas to deposit an Al x O y /Al/Al x O y coating. The compositions and thicknesses of the individual component layers were optimized to achieve high solar absorptance (a ¼ 0.950-0.970) and low thermal emittance (e ¼ 0.05-0.08). The X-ray diffraction data in thin film mode showed an amorphous structure of the Al x O y /Al/Al x O y coating. The X-ray photoelectron spectroscopy data of the Al x O y /Al/Al x O y multilayer absorber indicated that the Al x O y layers present in the coating were non-stoichiometric. The optical constants (n and k) of the multilayer absorber were determined from the spectroscopic ellipsometric data. Drude's free-electron model was used for generating the theoretical dispersion of optical constants for Al films, while the Tauc-Lorentz model was used for modeling optical properties of the dielectric Al x O y layers. In order to study the thermal stability of the Al x O y /Al/Al x O y coatings, they were subjected to heat treatment (in air and vacuum) at different temperatures and durations. The multilayer absorber deposited on Cu substrates exhibited high solar selectivity (a/e) of 0.901/0.06 even after heat-treatment in air up to 400 1C for 2 h. At 450 1C, the solar selectivity decreased significantly on Cu substrates (e.g., a/e ¼ 0.790/0.07). The coatings deposited on Mo substrates were thermally stable up to 800 1C in vacuum with a solar selectivity of 0.934/0.05. The structural stability of the absorber coatings heat treated in air (up to 400 1C) and vacuum (up to 800 1C) was confirmed by micro-Raman spectroscopy measurements. Studies on the accelerated aging tests suggested that the absorber coatings on Cu were stable in air up to 75 h at 300 1C and the service lifetime of the multilayer absorber was predicted to be more than 25 years. Further, the activation energy for the degradation of the multilayer absorber heat treated for longer durations in air is of the order of 64 kJ/mol.
Solar selective coatings of HfO x /Mo/HfO 2 were deposited on copper (Cu) and stainless steel (SS... more Solar selective coatings of HfO x /Mo/HfO 2 were deposited on copper (Cu) and stainless steel (SS) substrates using a magnetron sputtering system. The HfO x and HfO 2 layers were deposited from the sputtering of Hf target in Ar+O 2 plasma using an asymmetric bipolar-pulsed direct current generator. Whereas, the Mo layer was deposited from the sputtering of Mo target in the Ar plasma. The optimized HfO x /Mo/HfO 2 multilayer absorber on Cu substrate exhibited high solar absorptance (α = 0.905-0.923) and low thermal emittance (ε = 0.07-0.09). Similarly, on SS substrates the optimized coatings exhibited α and ε in the ranges of 0.902-0.917 and 0.15-0.17, respectively. The X-ray diffraction data showed that the HfO x /Mo/HfO 2 coating consists of tetragonal and monoclinic phases of HfO 2 , which was confirmed by micro-Raman spectroscopy data. The bonding structure of the HfO x and the HfO 2 layers were confirmed using X-ray photoelectron spectroscopy data. The optical constants (n and k), measured using spectroscopic ellipsometry, showed that the top HfO 2 layer acts as an antireflection coating and the bottom two layers (HfO x and Mo) are the main absorber layers. The analysis of the spectroscopic a)
ABSTRACT A new HfMoN(H)/HfMoN(L)/HfON/Al2O3 tandem absorber is designed and developed for high te... more ABSTRACT A new HfMoN(H)/HfMoN(L)/HfON/Al2O3 tandem absorber is designed and developed for high temperature solar thermal applications. The first absorber layer, HfMoN(H) is designed to have higher metallic content than the second HfMoN(L) layer. By varying the nitrogen flow rate, two different HfMoN layers with different refractive indices were deposited on SS substrates. The optical constants (n and k) measured using spectroscopic ellipsometry showed that HfMoN(H) and HfMoN(L) are the main absorber layers and HfON/Al2O3 acts as a double layer antireflection coating. The gradual decrease in the refractive indices from the substrate to the top resulted in increase in the absorptance, which was confirmed by the ellipsometric measurements. The optimized four layer tandem absorber exhibited high absorptance (α=0.94–0.95) and low thermal emittance (ε82 °C=0.13–0.14). The four layer tandem absorber was thermally stable up to 600 °C for 450 h and 650 °C for 100 h in vacuum. Whereas, coatings heat-treated in air were thermally stable up to 475 °C for 34 h.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
A number of carbon substituents possessing various functional groups could be introduced onto aro... more A number of carbon substituents possessing various functional groups could be introduced onto aromatic nitro compounds using dimethyl malonate as a one-carbon source and linker. Decarboxylation of both the ester groups originating from dimethyl malonate in this methodology is particularly significant.
Furan derivatives R 0060 Synthesis of Substituted Butenolides by the Ring Closing Metathesis of T... more Furan derivatives R 0060 Synthesis of Substituted Butenolides by the Ring Closing Metathesis of Two Electron Deficient Olefins: A General Route to the Natural Products of Paraconic Acids Class.-Ring-closing metathesis of highly electron-deficient dienes derived from Baylis-Hillman adducts gives butenolides in good yields. Derivative (IIc) serves as starting material for the synthesis of racemic phaseolinic acid (III).
2-Arylpropenoic acids signify a medicinally important class of non-steroidal anti-inflammatory ag... more 2-Arylpropenoic acids signify a medicinally important class of non-steroidal anti-inflammatory agents. 1 2-Arylpropenoic acids possessing nitro groups in their aromatic rings such as 2 are potential starting materials for the preparation of several analgesic and anti-inflammatory ...
Carbazole derivatives Carbazole derivatives R 0150 An Efficient Total Synthesis of 9-Methoxycarba... more Carbazole derivatives Carbazole derivatives R 0150 An Efficient Total Synthesis of 9-Methoxycarbazole-3-carbaldehyde Based on a Novel Methodology for the Preparation of Methoxyindoles.-The synthesis of the naturally occurring aldehyde (X), based on a recently reported methodology for the preparation of 1-methoxyindoles, is reported. Furthermore, a benzannulation strategy is employed using ring-closing metathesis as the key step.
... 207257. 6. RM Acheson, PG Hunt, DM Littlewood, BA Murrer and HE Rosenberg, J. Chem. Soc., Pe... more ... 207257. 6. RM Acheson, PG Hunt, DM Littlewood, BA Murrer and HE Rosenberg, J. Chem. Soc., Perkin Trans. ... Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (47). 9. N Selvakumar, B Yadi Reddy, G Sunil Kumar and J Iqbal, Tetrahedron Lett. ...
A new spectrally selective NbAlN/NbAlON/Si 3 N 4 tandem absorber was deposited on copper substrat... more A new spectrally selective NbAlN/NbAlON/Si 3 N 4 tandem absorber was deposited on copper substrates using a reactive direct current magnetron sputtering system. A high solar absorptance (0.956) and a low emittance (0.07) were achieved by gradually decreasing the refractive index from the substrate to the surface. The tandem absorber was characterized using solar spectrum reflectometer and emissometer, X-ray photoelectron spectroscopy, phase-modulated spectroscopic ellipsometry, atomic force microscopy and micro-Raman spectroscopy techniques. In order to study the thermal stability of the tandem absorbers, they were subjected to heat treatment (in air and vacuum) at different durations and temperatures. The tandem absorber deposited on copper substrate exhibited high solar selectivity in the order of 13-15 even after heat treatment in air up to 500 1C for 2 h. These tandem absorbers also exhibited high thermal stability (450 1C) in air for longer durations (116 h). The onset of oxidation for the tandem absorber deposited on silicon substrates was 650 1C, indicating a high oxidation resistance. The results of the present study indicate the importance of NbAlN/NbAlON/Si 3 N 4 tandem absorber for high-temperature solar selective applications.
Spectrally selective TiAlN/AlON tandem absorbers were deposited on copper and stainless steel sub... more Spectrally selective TiAlN/AlON tandem absorbers were deposited on copper and stainless steel substrates using a reactive DC/RF magnetron sputtering system. The compositions and thicknesses of the individual component layers were optimized to achieve high absorptance (a ¼ 0.931-0.942) and low emittance (e ¼ 0.05-0.06) on copper substrate. The experimental spectroscopic ellipsometric data have been fitted with the theoretical models to derive the dispersion of the optical constants (n and k). In order to study the thermal stability of the tandem absorbers, they were subjected to heat treatment (in air and vacuum) for different durations and temperatures. The tandem absorber deposited on Cu substrates exhibited high solar selectivity (a/e) of 0.946/0.07 even after heat treatment in air up to 600 1C for 2 h. At 625 1C, the solar selectivity decreased significantly on Cu substrates (e.g., a/e ¼ 0.924/ 0.30). The tandem absorber on Cu substrates was also stable in air up to 100 h at 400 1C with a solar selectivity of 0.919/0.06. Studies on the accelerated aging tests indicated that the activation energy for the degradation of the tandem absorber is of the order of 100 kJ/mol.
Thin films of TiO 2 were grown on n-type Si substrate by thermal oxidation of Ti films deposited ... more Thin films of TiO 2 were grown on n-type Si substrate by thermal oxidation of Ti films deposited by dc sputtering. The phase purity of TiO 2 was confirmed by Raman spectroscopy, and secondary ion mass spectroscopy was used to analyze the interfacial and chemical composition of ...
Approximately 1.8 m thick nanolayered multilayer coatings of TiN/CrN (also known as superlattice... more Approximately 1.8 m thick nanolayered multilayer coatings of TiN/CrN (also known as superlattices) were deposited on silicon (100) substrates at different modulation wavelengths (4.6-12.8 nm), substrate temperatures (50-400 °C) and substrate bias voltages (-50 to-200 V) using a reactive direct current magnetron sputtering system. X-ray reflectivity (XRR) technique was employed to determine various properties of the multilayers such as interface roughness, surface roughness, electron density, critical angle and individual layer thicknesses. The modulation wavelengths of the TiN/CrN superlattice coatings were calculated using modified Bragg's law. Furthermore, the experimental X-ray reflectivity patterns were simulated using theoretically generated patterns and a good fit was obtained for a three layer model, i.e., (1) top surface roughness layer, (2) TiN/CrN multilayer coating (approximately 1.8 m) and (3) Ti interlayer (~ 0.5 m) at the film-substrate interface. For the superlattice coatings prepared at a modulation wavelength of 9.7 nm, a substrate bias of-200 V and a substrate temperature of 400 C the XRR patterns showed Bragg reflections up to 5 th order, indicating well-defined a)
We have designed and developed an indigenous ultra high vacuum (UHV) sputtering system which can ... more We have designed and developed an indigenous ultra high vacuum (UHV) sputtering system which can deposit magnetic thin films with high purity and good uniformity. The equipment consists of state-of the-art technologies and sophistication. With this system it is possible to deposit coatings of various materials on a sample size of 3"3" 3". The Ni 81 Fe 19 ferromagnetic thin films, with Tantalum (Ta) as a buffer and cap layers have been deposited on silicon substrates using this ultra high vacuum (UHV) sputtering system. The magneto transport measurement study indicated a significant variation in the AMR values of the films for varying thicknesses of tantalum and NiFe layers.
Some novel oxazolidinone derivatives with benzotriazole as pendant have been synthesized and test... more Some novel oxazolidinone derivatives with benzotriazole as pendant have been synthesized and tested for antibacterial activity. Linearly attached benzotriazole derivative showed more potency compared to angular one in vitro. Out of E/Z-isomers of angularly attached derivatives E-isomer was found to be more potent than Z-isomer. Either less active or inactive molecules were obtained, when benzotriazole was replaced with benzimidazole, benzthiazole, or benzoxazole. Finally, thioacetamide analogue of linear compound gave a lead having activity similar to linezolid in vitro.
A series of conformationally constrained analogues of Linezolid were synthesised by employing a t... more A series of conformationally constrained analogues of Linezolid were synthesised by employing a tandem SN(2) and SNAr reaction as the key step and tested for antibacterial activity. While the hexahydroazolo-quinoxaline compounds were inactive, the tetrahydroazolo-benzothiazine compounds exhibited interesting antibacterial activity. The introduction of fluorine in the aromatic ring further made the compounds more potent in acetamide compounds resulting in an interesting analogue 32. However, the introduction of fluorine (analogue 34) on the already potent non-fluorine thiocarbamate 21 did not have any influence on the activity.
The syntheses of a number of novel oxazolidinone analogues possessing an urea functionality are r... more The syntheses of a number of novel oxazolidinone analogues possessing an urea functionality are reported. While the urea derivatives possessing aliphatic and aromatic groups were prepared by the more conventional isocyanate method, the derivatives possessing heterocyclic rings were synthesized by a relatively uncommon but otherwise efficient carbamate chemistry. Though the SAR resulted in novel compounds possessing in vitro activity equivalent to Linezolid, the compounds possess a range of substituents that are amenable for altering physicochemical properties of the resultant drug. The antibacterial activity was found to be not sensitive to the functional groups attached to the urea site regardless of the size and electronic characteristics. Based on in vivo results, one molecule has been identified as a candidate and additional work such as salt selection, scale-up, etc., are currently underway to take the molecule further through development.
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