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Covalent grafting of polydimethylsiloxane over surface-modified alumina nanoparticles / Satyajit Gupta in Industrial & engineering chemistry research, Vol. 50 N° 11 (Juin 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 11 (Juin 2011) . - pp 6585–6593 Titre : Covalent grafting of polydimethylsiloxane over surface-modified alumina nanoparticles Type de document : texte imprimé Auteurs : Satyajit Gupta, Auteur ; Praveen C. Ramamurthy, Auteur ; Giridhar Madras, Auteur Année de publication : 2011 Article en page(s) : pp 6585–6593 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Polymer  nanocomposites Résumé : The synthesis of “smart structured” conducting polymers and the fabrication of devices using them are important areas of research. However, conducting polymeric materials that are used in devices are susceptible to degradation due to oxygen and moisture. Thus, protection of such devices to ensure long-term stability is always desirable. Polymer nanocomposites are promising materials for the encapsulation of such devices. Therefore, it is important to develop suitable polymer nanocomposites as encapsulation materials to protect such devices. This work presents a technique based on grafting between surface-decorated γ-alumina nanoparticles and polymer to make nanocomposites that can be used for the encapsulation of devices. Alumina was functionalized with allyltrimethoxysilane and used to conjugate polymer molecules (hydride-terminated polydimethylsiloxane) through a platinum-catalyzed hydrosilylation reaction. Fourier transform infrared spectroscopy, X-ray-photoelectron spectroscopy, and Raman spectroscopy were used to characterize the surface chemistry of the nanoparticles after surface modification. The grafting density of alkene groups on the surface of the modified nanoparticles was calculated using CHN and thermogravimetric analyses. The thermal stability of the composites was also evaluated using thermogravimetric analysis. The nanoindentation technique was used to analyze the mechanical characteristics of the composites. The densities of the composites were evaluated using a density gradient column, and the morphology of the composites was evaluated by scanning electron microscopy. All of our studies reveal that the composites have good thermal stability and mechanical flexibility and, thus, can potentially be used for the encapsulation of organic photovoltaic devices. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie200283w [article] Covalent grafting of polydimethylsiloxane over surface-modified alumina nanoparticles [texte imprimé] / Satyajit Gupta, Auteur ; Praveen C. Ramamurthy, Auteur ; Giridhar Madras, Auteur . - 2011 . - pp 6585–6593. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 11 (Juin 2011) . - pp 6585–6593 Mots-clés : Polymer  nanocomposites Résumé : The synthesis of “smart structured” conducting polymers and the fabrication of devices using them are important areas of research. However, conducting polymeric materials that are used in devices are susceptible to degradation due to oxygen and moisture. Thus, protection of such devices to ensure long-term stability is always desirable. Polymer nanocomposites are promising materials for the encapsulation of such devices. Therefore, it is important to develop suitable polymer nanocomposites as encapsulation materials to protect such devices. This work presents a technique based on grafting between surface-decorated γ-alumina nanoparticles and polymer to make nanocomposites that can be used for the encapsulation of devices. Alumina was functionalized with allyltrimethoxysilane and used to conjugate polymer molecules (hydride-terminated polydimethylsiloxane) through a platinum-catalyzed hydrosilylation reaction. Fourier transform infrared spectroscopy, X-ray-photoelectron spectroscopy, and Raman spectroscopy were used to characterize the surface chemistry of the nanoparticles after surface modification. The grafting density of alkene groups on the surface of the modified nanoparticles was calculated using CHN and thermogravimetric analyses. The thermal stability of the composites was also evaluated using thermogravimetric analysis. The nanoindentation technique was used to analyze the mechanical characteristics of the composites. The densities of the composites were evaluated using a density gradient column, and the morphology of the composites was evaluated by scanning electron microscopy. All of our studies reveal that the composites have good thermal stability and mechanical flexibility and, thus, can potentially be used for the encapsulation of organic photovoltaic devices. DEWEY : 660 ISSN : 0888-5885 En ligne : http://pubs.acs.org/doi/abs/10.1021/ie200283w

Effect of oxidizers on microwave-assisted oxidative degradation of poly(alkyl acrylates) / A. Marimuthu in Industrial & engineering chemistry research, Vol. 47 N°20 (Octobre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N°20 (Octobre 2008) . - P. 7538-7544 Titre : Effect of oxidizers on microwave-assisted oxidative degradation of poly(alkyl acrylates) Type de document : texte imprimé Auteurs : A. Marimuthu, Editeur scientifique ; Giridhar Madras, Editeur scientifique Année de publication : 2008 Article en page(s) : P. 7538-7544 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Effect  of  oxidizers  Microwave-assisted  oxidative  Poly(methyl  acrylate)  (PMA)  Poly(ethyl  acrylate)  (PEA) Résumé : The effect of oxidizers on the microwave-assisted oxidative degradation kinetics of poly(alkyl acrylates), namely, poly(methyl acrylate) (PMA), poly(ethyl acrylate) (PEA), and poly(butyl acrylate) (PBA), was studied. The molecular weight distributions were measured by gel permeation chromatography, and continuous distribution kinetic models were used to determine the degradation rate coefficients. The effect of alkyl group substituents on the microwave-assisted oxidative degradation of poly(alkyl acrylates) was also investigated. The degradation rate of poly(alkyl acrylates) decreased with an increase in the number of carbon atoms of the alkyl substituents and thus followed the order PMA > PEA > PBA, while the activation energy increased with the length of alkyl group substituents. The rate coefficients of hydrogen abstraction and oxidative random chain scission were found to be independent of the oxidizer and dependent only on the nature of the polymer. The differences in the overall degradation rate of poly(ethyl acrylate) in the presence of different oxidizing agents were only dependent on the rate of oxidizer dissociation. This is the first study that shows that the degradation rate of the polymer in the presence of any oxidizer can be predicted by knowing only the thermal dissociation rate constant values of the oxidizer, which can be easily obtained from existing literature. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie7017349 [article] Effect of oxidizers on microwave-assisted oxidative degradation of poly(alkyl acrylates) [texte imprimé] / A. Marimuthu, Editeur scientifique ; Giridhar Madras, Editeur scientifique . - 2008 . - P. 7538-7544. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N°20 (Octobre 2008) . - P. 7538-7544 Mots-clés : Effect  of  oxidizers  Microwave-assisted  oxidative  Poly(methyl  acrylate)  (PMA)  Poly(ethyl  acrylate)  (PEA) Résumé : The effect of oxidizers on the microwave-assisted oxidative degradation kinetics of poly(alkyl acrylates), namely, poly(methyl acrylate) (PMA), poly(ethyl acrylate) (PEA), and poly(butyl acrylate) (PBA), was studied. The molecular weight distributions were measured by gel permeation chromatography, and continuous distribution kinetic models were used to determine the degradation rate coefficients. The effect of alkyl group substituents on the microwave-assisted oxidative degradation of poly(alkyl acrylates) was also investigated. The degradation rate of poly(alkyl acrylates) decreased with an increase in the number of carbon atoms of the alkyl substituents and thus followed the order PMA > PEA > PBA, while the activation energy increased with the length of alkyl group substituents. The rate coefficients of hydrogen abstraction and oxidative random chain scission were found to be independent of the oxidizer and dependent only on the nature of the polymer. The differences in the overall degradation rate of poly(ethyl acrylate) in the presence of different oxidizing agents were only dependent on the rate of oxidizer dissociation. This is the first study that shows that the degradation rate of the polymer in the presence of any oxidizer can be predicted by knowing only the thermal dissociation rate constant values of the oxidizer, which can be easily obtained from existing literature. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie7017349

Microwave synthesis and photocatalytic activity of nano lanthanide (Ce, Pr, and Nd) orthovanadates / Sudarshan Mahapatra in Industrial & engineering chemistry research, Vol. 47 N°17 (Septembre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N°17 (Septembre 2008) . - p. 6509–6516 Titre : Microwave synthesis and photocatalytic activity of nano lanthanide (Ce, Pr, and Nd) orthovanadates Type de document : texte imprimé Auteurs : Sudarshan Mahapatra, Auteur ; Susanta K. Nayak, Auteur ; Giridhar Madras, Auteur Année de publication : 2008 Article en page(s) : p. 6509–6516 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Lanthanide  orthovanadates  Photocatalytic  activities  Crystal  structure  X-ray  diffraction Résumé : Lanthanide orthovanadates, CeVO4, PrVO4, and NdVO4, of nanodimensions were synthesized under microwave exposure, and the photocatalytic activities of these compounds were investigated. These compounds exhibit a tetragonal zircon structure, crystallizing in the space group I41/amd with a = 7.3733(4) and c = 6.4909(4) Å with Z = 4. The crystal structure was analyzed by powder X-ray diffraction, and the band gap was analyzed by UV−visible spectroscopy. Particle sizes were in the range of 25−30 nm, as observed by transmission electron microscopy. While the energy dispersive X-ray analysis indicates the formation of LnVO4, thermal analysis of these solids shows stability of the phase up to 1000 °C. The photocatalytic activity of all these orthovanadates has been investigated by degrading various dyes like methylene blue (MB), Orange G (OG), Rhodamine B (RB), Rhodamine Blue (RBL), and Remazol brilliant blue (RBBR) under UV irradiation. Further, these compounds were also used to degrade organic pollutants like phenol, 2,4-dinitrophenol and 2,4-dichlorophenol. The degradation rates of dyes and organics in presence of microwave-synthesized orthovanadates are higher compared to that observed with orthovanadates synthesized by the solid state technique. The microwave-synthesized orthovandates also show chloro-specificity, with the rate of degradation of 2,4-dichlorophenol significantly higher than that observed in presence of Degussa P-25 titania. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8003094 [article] Microwave synthesis and photocatalytic activity of nano lanthanide (Ce, Pr, and Nd) orthovanadates [texte imprimé] / Sudarshan Mahapatra, Auteur ; Susanta K. Nayak, Auteur ; Giridhar Madras, Auteur . - 2008 . - p. 6509–6516. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N°17 (Septembre 2008) . - p. 6509–6516 Mots-clés : Lanthanide  orthovanadates  Photocatalytic  activities  Crystal  structure  X-ray  diffraction Résumé : Lanthanide orthovanadates, CeVO4, PrVO4, and NdVO4, of nanodimensions were synthesized under microwave exposure, and the photocatalytic activities of these compounds were investigated. These compounds exhibit a tetragonal zircon structure, crystallizing in the space group I41/amd with a = 7.3733(4) and c = 6.4909(4) Å with Z = 4. The crystal structure was analyzed by powder X-ray diffraction, and the band gap was analyzed by UV−visible spectroscopy. Particle sizes were in the range of 25−30 nm, as observed by transmission electron microscopy. While the energy dispersive X-ray analysis indicates the formation of LnVO4, thermal analysis of these solids shows stability of the phase up to 1000 °C. The photocatalytic activity of all these orthovanadates has been investigated by degrading various dyes like methylene blue (MB), Orange G (OG), Rhodamine B (RB), Rhodamine Blue (RBL), and Remazol brilliant blue (RBBR) under UV irradiation. Further, these compounds were also used to degrade organic pollutants like phenol, 2,4-dinitrophenol and 2,4-dichlorophenol. The degradation rates of dyes and organics in presence of microwave-synthesized orthovanadates are higher compared to that observed with orthovanadates synthesized by the solid state technique. The microwave-synthesized orthovandates also show chloro-specificity, with the rate of degradation of 2,4-dichlorophenol significantly higher than that observed in presence of Degussa P-25 titania. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8003094

Photocatalytic activity of combustion synthesized ZrO2 and ZrO2 – TiO2 mixed oxides / Sneha Polisetti in Industrial & engineering chemistry research, Vol. 50 N° 23 (Décembre 2011) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 50 N° 23 (Décembre 2011) . - pp. 12915-12924 Titre : Photocatalytic activity of combustion synthesized ZrO2 and ZrO2 – TiO2 mixed oxides Type de document : texte imprimé Auteurs : Sneha Polisetti, Auteur ; Parag A. Deshpande, Auteur ; Giridhar Madras, Auteur Année de publication : 2012 Article en page(s) : pp. 12915-12924 Note générale : Chimie industrielle Langues : Anglais (eng) Mots-clés : Titanium  oxide  Combustion  Photocatalysis Résumé : Tetragonal ZrO2, synthesized by solution combustion technique, was found to be photocatalytically active for the degradation of anionic dyes. The compound was characterized by FT-Raman spectroscopy, X-ray photoelectron spectroscopy, FT-infrared spectroscopy, UV―vis spectroscopy, BET surface area analysis, and zero point charge pH measurement. A high concentration of surface hydroxyl groups was observed over the catalyst, as confirmed by XPS and FTIR. The photocatalytic degradation of orange G, amido black, remazol brilliant blue R, and alizarin cyanine green (ACG) was carried out with this material. The effect of pH, inorganic salts, and H2O2 on the activity of the catalyst was also studied, and it was found that the catalyst maintained its activity at a wide range of pH and in the presence of inorganic salts. Having established that ZrO2 was photocatalytically active, mixed oxide catalysts of TiO2―ZrO2 were also tested for the photocatalytic degradation of ACG, and the 50% ZrO2―TiO2 mixed oxides showed activity that was comparable to the activity of TiO2. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=25267449 [article] Photocatalytic activity of combustion synthesized ZrO2 and ZrO2 – TiO2 mixed oxides [texte imprimé] / Sneha Polisetti, Auteur ; Parag A. Deshpande, Auteur ; Giridhar Madras, Auteur . - 2012 . - pp. 12915-12924. Chimie industrielle Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 50 N° 23 (Décembre 2011) . - pp. 12915-12924 Mots-clés : Titanium  oxide  Combustion  Photocatalysis Résumé : Tetragonal ZrO2, synthesized by solution combustion technique, was found to be photocatalytically active for the degradation of anionic dyes. The compound was characterized by FT-Raman spectroscopy, X-ray photoelectron spectroscopy, FT-infrared spectroscopy, UV―vis spectroscopy, BET surface area analysis, and zero point charge pH measurement. A high concentration of surface hydroxyl groups was observed over the catalyst, as confirmed by XPS and FTIR. The photocatalytic degradation of orange G, amido black, remazol brilliant blue R, and alizarin cyanine green (ACG) was carried out with this material. The effect of pH, inorganic salts, and H2O2 on the activity of the catalyst was also studied, and it was found that the catalyst maintained its activity at a wide range of pH and in the presence of inorganic salts. Having established that ZrO2 was photocatalytically active, mixed oxide catalysts of TiO2―ZrO2 were also tested for the photocatalytic degradation of ACG, and the 50% ZrO2―TiO2 mixed oxides showed activity that was comparable to the activity of TiO2. DEWEY : 660 ISSN : 0888-5885 En ligne : http://cat.inist.fr/?aModele=afficheN&cpsidt=25267449

Photocatalytic and thermal degradation of poly(methyl methacrylate), poly(butyl acrylate), and their copolymers / Vinod Kumar Konaganti in Industrial & engineering chemistry research, Vol. 48 N°4 (Février 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N°4 (Février 2009) . - pp. 1712–1718 Titre : Photocatalytic and thermal degradation of poly(methyl methacrylate), poly(butyl acrylate), and their copolymers Type de document : texte imprimé Auteurs : Vinod Kumar Konaganti, Auteur ; Giridhar Madras, Auteur Année de publication : 2009 Article en page(s) : pp. 1712–1718 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Poly(methyl  methacrylate)  Poly(butyl  acrylate)  Photocatalytic  degradation  Thermal  degradation  o-dichlorobenzene  Copolymers Résumé : The photocatalytic and thermal degradations of poly(methyl methacrylate), poly(butyl acrylate), and their copolymers of different compositions were studied. The photocatalytic degradation was investigated in o-dichlorobenzene in the presence of two different catalysts, namely, Degussa P-25 and combustion synthesized nanotitania (CSN-TiO2). The samples were analyzed by using gel permeation chromatography (GPC) to obtain the molecular weight distributions (MWDs) as a function of reaction time. Experimental data indicated that the photodegradation of these polymers occurs by both random and chain end scission. A continuous distribution kinetic model was used to determine the degradation rate coefficients by fitting the experimental data with the model. Both the random and specific rate coefficients of the copolymers decreased with increasing percentage of butyl acrylate (BA). Thermal degradation of the copolymers was investigated by thermogravimetry. The normalized weight loss profiles for the copolymers showed that the thermal stability of the copolymers increased with mole percentage of BA in the copolymer (PMMABA). The Ozawa method was used to determine the activation energies at different conversions. At low acrylate content in the copolymer, the activation energy depends on conversion, indicating multiple degradation mechanisms. At high acrylate content in the copolymer, the activation energy is independent of conversion, indicating degradation by a one-step mechanism. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801646y [article] Photocatalytic and thermal degradation of poly(methyl methacrylate), poly(butyl acrylate), and their copolymers [texte imprimé] / Vinod Kumar Konaganti, Auteur ; Giridhar Madras, Auteur . - 2009 . - pp. 1712–1718. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N°4 (Février 2009) . - pp. 1712–1718 Mots-clés : Poly(methyl  methacrylate)  Poly(butyl  acrylate)  Photocatalytic  degradation  Thermal  degradation  o-dichlorobenzene  Copolymers Résumé : The photocatalytic and thermal degradations of poly(methyl methacrylate), poly(butyl acrylate), and their copolymers of different compositions were studied. The photocatalytic degradation was investigated in o-dichlorobenzene in the presence of two different catalysts, namely, Degussa P-25 and combustion synthesized nanotitania (CSN-TiO2). The samples were analyzed by using gel permeation chromatography (GPC) to obtain the molecular weight distributions (MWDs) as a function of reaction time. Experimental data indicated that the photodegradation of these polymers occurs by both random and chain end scission. A continuous distribution kinetic model was used to determine the degradation rate coefficients by fitting the experimental data with the model. Both the random and specific rate coefficients of the copolymers decreased with increasing percentage of butyl acrylate (BA). Thermal degradation of the copolymers was investigated by thermogravimetry. The normalized weight loss profiles for the copolymers showed that the thermal stability of the copolymers increased with mole percentage of BA in the copolymer (PMMABA). The Ozawa method was used to determine the activation energies at different conversions. At low acrylate content in the copolymer, the activation energy depends on conversion, indicating multiple degradation mechanisms. At high acrylate content in the copolymer, the activation energy is independent of conversion, indicating degradation by a one-step mechanism. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie801646y

Reversible swelling / deswelling characteristics of ethylene glycol dimethacrylate cross - linked poly (acrylic acid - co - sodium acrylate - co - acrylamide) superabsorbents / Neelesh Bharti Shukla in Industrial & engineering chemistry research, Vol. 50 N° 19 (Octobre 2011) 

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Solution combustion synthesis of nanosized copper chromite and its use as a burn rate modifier in solid propellants / P. S. Sathiskumar in Industrial & engineering chemistry research, Vol. 51 N° 30 (Août 2012) 

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Swelling and Dye-Adsorption Characteristics of an Amphoteric Superabsorbent Polymer / Neelesh Bharti Shukla in Industrial & engineering chemistry research, Vol. 51 N° 46 (Novembre 2012) 

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Thermal and photocatalytic degradation of poly(methyl methacrylate), poly(butyl methacrylate), and their copolymers / Nagu Daraboina in Industrial & engineering chemistry research, Vol. 47 N°18 (Septembre 2008) 

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