Himansulal Nayak | OUAT, Bhubaneswar (original) (raw)
Papers by Himansulal Nayak
Results in Chemistry, Nov 30, 2023
International Journal of Recent Advances in Multidisciplinary Research, 2023
This work describes a novel green and ecofriendly technique for manufacture of pure and metal dop... more This work describes a novel green and ecofriendly technique for manufacture of pure and metal doped zinc oxide nanoparticles utilising aloe vera plant extract. The microwave approach was used to biosynthesize pure and 1.5 wt% Mg doped nanostructured zinc oxide utilising high purity metal nitrates and aloe vera plant extract. Diffuse reflectance spectroscopy (DRS), X-ray diffraction method (XRD), Fourier transform infrared spectroscopy (FT-IR), High resolution scanning electron microscope (HR-SEM), and Photoluminescence (PL) spectroscopy were used to characterise the synthesized doped zinc oxide nanoparicles. XRD analyses supported the formation of the hexagonal wurtzite structure in zinc oxide. The FT-IR method also supported the creation of the zinc oxide phase. DRS and PL were used to determine the optical characteristics. The band gap of 1.5 wt% Mg doped zinc oxide was found to be greater than that of pure zinc oxide.
Asian journal of chemical sciences, Apr 21, 2023
The data for the nonisothermal and isothermal thermal decompositions of lanthanum oxalate have be... more The data for the nonisothermal and isothermal thermal decompositions of lanthanum oxalate have been analysed using the model-free and model-fitting kinetic techniques. When applied to nonisothermal data using the Coat-Redfern(CR) equation, the widely used model-fitting approach that results excellent fitting for both isothermal and nonisothermal data but produces very ambiguous values of the Arrhenius parameters. These values cannot be compared to those obtained from isothermal experiments. On the other hand, the model-free strategy represented by the iso-conversional method, such as Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose
Asian Journal of Applied Chemistry Research
The Photocatalytic performance of the Calcium doped lanthanum manganite nanocomposite for photode... more The Photocatalytic performance of the Calcium doped lanthanum manganite nanocomposite for photodegradation of Methylene Blue(MB) dye as an Organic water pollutant,was evaluated over visible light irradiation, at a pH of 4, at constant dose for several hours. The result showed La0.75Ca0.25MnO3 having Perovskite structure shows high degree of catalytic efficiency of 69% within 100 min illumination time, for the removal of Methylene Blue organic dye from its aqueous solution. The sample powder(LCMO) was prepared through sol-gel technique and was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Inductively coupled plasma- atomic emission spectroscopy (ICP-AES), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX) and UV-Vis spectroscopy (UV-Vis). The XRD data revealed the formation of single phase crystallinity.SEM images shows that the micro sized La0.75Ca0.25MnO3 powder has nanocrystalline structure with average diame...
Transactions of Nonferrous Metals Society of China, 2016
Nanostructured zinc–copper mixed ferrite was synthesized using sol–gel method. Different composit... more Nanostructured zinc–copper mixed ferrite was synthesized using sol–gel method. Different compositions of ferrite, Zn(1–x)CuxFe2O4 (x=0.0, 0.25, 0.50, 0.75), characterized by XRD, reveal single phase inverse spinel in all the samples. With increasing copper content, the crystallite size increases. The surface morphology of all the samples, studied by SEM, shows porous structure of particles. The prepared samples were also analyzed by FT-IR and TEM. Catalytic activity of the samples was studied on lanthanum oxalate decomposition by thermogravimety. The rate constant k has the highest value with x=0.75 and 5% (mole fraction) of the catalyst and is attributed to high copper content, the mixed sites Cu2+−Fe + and/or Cu+−Fe2+ ion pairs besides the one component sites Cu2+−Cu+, Fe3+−Fe2+, as a result of mutual charge interaction. In other words, the increasing activity of mixed oxides is attributed to increase in the content of active sites via creation of new ion pairs. With increasing Zn content, particle size increases. Variation of catalytic activity of ferrite powders is due to the changes of the valence state of catalytically active components of the ferrites, which oxidizes the carbon monoxide released from lanthanum oxalate.
IOSR Journal of Applied Chemistry, 2014
A study on the thermal decomposition of the mixtures of lanthanum oxalate hydrate and transition ... more A study on the thermal decomposition of the mixtures of lanthanum oxalate hydrate and transition metal nano oxide compounds(TMNOCs) viz. CuO, Fe2O3, TiO2 and Cr2O3 of 5 mole% ratio has been carried out employing Thermogravimetry, Differential Thermal Analysis and chemical analysis. The results reveal that other than CuO the oxides have a retarding effect on the decomposition rate. There is a competition of rate between Fe2O3 and TiO2 mixture up to 696K after which the trend is reversed and Fe2O3 becomes relatively more catalytic than TiO2. The best explanation for catalytic activities of the oxides is made by taking the former as a function of electronic configuration of the metal rather than the electronic properties of the oxides. Abnormal behaviour of Cr2O3 may be attributed to an irreversible change in oxidation state of Cr 3+ during which it is oxidised to Cr 6+ prior to decomposition. The kinetic and thermodynamic parameters are evaluated in the light of F 3 mechanism in two d...
Thermochimica Acta, 2002
ABSTRACT A study on the thermal decomposition of mixtures of lanthanum oxalate hydrate and magnes... more ABSTRACT A study on the thermal decomposition of mixtures of lanthanum oxalate hydrate and magnesium chromite spinel, MgCr2O4 of different molar ratios has been carried out employing thermogravimetry, differential thermal analysis, chemical analysis, infrared spectroscopy and X-ray diffraction analysis. It is evident from the data that lanthanum oxalate in the presence of mixed oxide starts to decompose at a temperature higher than the pure salt. The results reveal that chromium oxide has a retarding effect on the decomposition rate and addition of magnesium oxide leads to an observable increase in the catalytic behaviour of Cr2O3 towards the decomposition below 440 °C, above which it increases significantly with increasing percentage of MgCr2O4. The induced defects during the formation of solid solution alters the conductive properties of the oxide, due to generation of more holes within the catalyst, consequently increasing its, activity towards decomposition. The kinetic and thermogravimetric parameters are evaluated in the light of D3 mechanism. The reaction occurs through three different stages and the rate constant, k is found to follow the order: and LO1>LO2>LO3 (653–713 K), LO1<LO2<LO3 (713–753 K), where LO1, LO2 and LO3 stand for different mole percentage mixtures of MgCr2O4 with lanthanum oxalate.
Lanthanum Oxalate decahydrate and Copper ferrites were prepared by chemical and sintering process... more Lanthanum Oxalate decahydrate and Copper ferrites were prepared by chemical and sintering process respectively and the detailed investigation of their properties was carried out successfully at room temperature by FTIR,XRD,SEM ,TEM as well as by chemical methods. Catalytic activity of copper ferrite over the decomposition of lanthanum oxalate was studied non isothermally by TG-DTA after mixing the former with the later in varying mole ratios. Also a physical mixture of CuO and Fe2O3 was prepared for comparative study. It is found that CuO has catalytic activity whereas Fe2O3 behaves as negative catalyst for the entire process. But the physical mixture enhances the rate of reaction at the low temperature and as the temperature becomes high the solid solution of copper ferrite is expected to be formed by valence induction generating ntype semi conduction in Fe2O3 resulting in a ferrite having inverse spinel structure and having high rate constant. There is no appreciable change in act...
Nanostructured zinc-copper mixed ferrite was synthesized using sol-gel method. XRD patterns of di... more Nanostructured zinc-copper mixed ferrite was synthesized using sol-gel method. XRD patterns of different compositions of zinc copper ferrite, Zn (1−) Cu Fe 2 O 4 (x = 0.0, 0.25, 0.50, 0.75), revealed single phase inverse spinel ferrite in all the samples. With increasing copper concentration, the crystallite size increases from 28 nm to 47 nm. The surface morphology of all the samples studied by the Scanning Electron Microscopy showing porous structure of particles throughout the sample. The prepared samples were also analysed by XRD,FTIR,TEM. Catalytic activity of the prepared samples were studied on lanthanum oxalate decomposition by Thermogravimetric methods(TGA).The rate constant 'k' has got the highest value with x=0.75 and 5 mol% concentration and highest value is attributed to high copper concentration and also due to the fact that, beside the one component sites Cu 2+-Cu + , Fe 3+-Fe 2+ , there will be also the mixed sites Cu 2+-Fe + and/or Cu +-Fe 2+ ion pairs as a result of mutual charge interaction.In other words, the increasing activity of mixed oxides might be attributed to increase in the concentration of active sites via creation of new ion pairs. With increasing Zn content increases particle size thereby providing comparatively less surface area for the catalytic activities due to large ionic radii of Zinc.Variation of catalytic activity of ferrite powders are probably due to the changes of the valence state of catalytically active components of the ferrite powders that oxidises the carbon monoxide released from Lanthanum oxalate
Research Paper, 2002
A study on the thermal decomposition of mixtures of lanthanum oxalate hydrate and magnesium chrom... more A study on the thermal decomposition of mixtures of lanthanum oxalate hydrate and magnesium chromite spinel, MgCr 2 O 4 of different molar ratios has been carried out employing thermogravimetry, differential thermal analysis, chemical analysis, infrared spectroscopy and X-ray diffraction analysis. It is evident from the data that lanthanum oxalate in the presence of mixed oxide starts to decompose at a temperature higher than the pure salt. The results reveal that chromium oxide has a retarding effect on the decomposition rate and addition of magnesium oxide leads to an observable increase in the catalytic behaviour of Cr 2 O 3 towards the decomposition below 440 8C, above which it increases signi®cantly with increasing percentage of MgCr 2 O 4. The induced defects during the formation of solid solution alters the conductive properties of the oxide, due to generation of more holes within the catalyst, consequently increasing its, activity towards decomposition. The kinetic and thermogravimetric parameters are evaluated in the light of D 3 mechanism. The reaction occurs through three different stages and the rate constant, k is found to follow the order: stage I > stage II < stage III and LO1 > LO2 > LO3 (653±713 K), LO1 < LO2 < LO3 (713±753 K), where LO1, LO2 and LO3 stand for different mole percentage mixtures of MgCr 2 O 4 with lanthanum oxalate.
A study on the thermal decomposition of mixtures of lanthanum oxalate hydrate and magnesium chrom... more A study on the thermal decomposition of mixtures of lanthanum oxalate hydrate and magnesium chromite spinel, MgCr 2 O 4 of different molar ratios has been carried out employing thermogravimetry, differential thermal analysis, chemical analysis, infrared spectroscopy and X-ray diffraction analysis. It is evident from the data that lanthanum oxalate in the presence of mixed oxide starts to decompose at a temperature higher than the pure salt. The results reveal that chromium oxide has a retarding effect on the decomposition rate and addition of magnesium oxide leads to an observable increase in the catalytic behaviour of Cr 2 O 3 towards the decomposition below 440 8C, above which it increases signi®cantly with increasing percentage of MgCr 2 O 4. The induced defects during the formation of solid solution alters the conductive properties of the oxide, due to generation of more holes within the catalyst, consequently increasing its, activity towards decomposition. The kinetic and thermogravimetric parameters are evaluated in the light of D 3 mechanism. The reaction occurs through three different stages and the rate constant, k is found to follow the order: stage I > stage II < stage III and LO1 > LO2 > LO3 (653±713 K), LO1 < LO2 < LO3 (713±753 K), where LO1, LO2 and LO3 stand for different mole percentage mixtures of MgCr 2 O 4 with lanthanum oxalate.
A study on the thermal decomposition of the mixtures of lanthanum oxalate hydrate and transition ... more A study on the thermal decomposition of the mixtures of lanthanum oxalate hydrate and transition metal nano oxide compounds(TMNOCs) viz. CuO, Fe 2 O 3 , TiO 2 and Cr 2 O 3 of 5 mole% ratio has been carried out employing Thermogravimetry, Differential Thermal Analysis and chemical analysis. The results reveal that other than CuO the oxides have a retarding effect on the decomposition rate. There is a competition of rate between Fe 2 O 3 and TiO 2 mixture up to 696K after which the trend is reversed and Fe 2 O 3 becomes relatively more catalytic than TiO 2. The best explanation for catalytic activities of the oxides is made by taking the former as a function of electronic configuration of the metal rather than the electronic properties of the oxides. Abnormal behaviour of Cr 2 O 3 may be attributed to an irreversible change in oxidation state of Cr 3+ during which it is oxidised to Cr 6 + prior to decomposition. The kinetic and thermodynamic parameters are evaluated in the light of F 3 mechanism in two different regions of α's and the rate follows the order:
Nanostructured zinc-copper mixed ferrite was synthesized using sol-gel method. XRD patterns of di... more Nanostructured zinc-copper mixed ferrite was synthesized using sol-gel method. XRD patterns of different compositions of zinc copper ferrite, Zn (1−) Cu Fe 2 O 4 (x = 0.0, 0.25, 0.50, 0.75), revealed single phase inverse spinel ferrite in all the samples. With increasing copper concentration, the crystallite size increases from 28 nm to 47 nm. The surface morphology of all the samples studied by the Scanning Electron Microscopy showing porous structure of particles throughout the sample. The prepared samples were also analysed by XRD,FTIR,TEM. Catalytic activity of the prepared samples were studied on lanthanum oxalate decomposition by Thermogravimetric methods(TGA).The rate constant 'k' has got the highest value with x=0.75 and 5 mol% concentration and highest value is attributed to high copper concentration and also due to the fact that, beside the one component sites Cu 2+-Cu + , Fe 3+-Fe 2+ , there will be also the mixed sites Cu 2+-Fe + and/or Cu +-Fe 2+ ion pairs as a result of mutual charge interaction.In other words, the increasing activity of mixed oxides might be attributed to increase in the concentration of active sites via creation of new ion pairs. With increasing Zn content increases particle size thereby providing comparatively less surface area for the catalytic activities due to large ionic radii of Zinc.Variation of catalytic activity of ferrite powders are probably due to the changes of the valence state of catalytically active components of the ferrite powders that oxidises the carbon monoxide released from Lanthanum oxalate
Research Paper, 2016
Nanostructured zinc−copper mixed ferrite was synthesized using sol−gel method. Different composit... more Nanostructured zinc−copper mixed ferrite was synthesized using sol−gel method. Different compositions of ferrite, Zn (1−x) Cu x Fe 2 O 4 (x=0.0, 0.25, 0.50, 0.75), characterized by XRD, reveal single phase inverse spinel in all the samples. With increasing copper content, the crystallite size increases. The surface morphology of all the samples, studied by SEM, shows porous structure of particles. The prepared samples were also analyzed by FT-IR and TEM. Catalytic activity of the samples was studied on lanthanum oxalate decomposition by thermogravimety .The rate constant k has the highest value with x=0.75 and 5% (mole fraction) of the catalyst and is attributed to high copper content, the mixed sites Cu 2+ −Fe + and/or Cu + −Fe 2+ ion pairs besides the one component sites Cu 2+ −Cu + , Fe 3+ −Fe 2+ , as a result of mutual charge interaction. In other words, the increasing activity of mixed oxides is attributed to increase in the content of active sites via creation of new ion pairs. With increasing Zn content, particle size increases. Variation of catalytic activity of ferrite powders is due to the changes of the valence state of catalytically active components of the ferrites, which oxidizes the carbon monoxide released from lanthanum oxalate.
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Results in Chemistry, Nov 30, 2023
International Journal of Recent Advances in Multidisciplinary Research, 2023
This work describes a novel green and ecofriendly technique for manufacture of pure and metal dop... more This work describes a novel green and ecofriendly technique for manufacture of pure and metal doped zinc oxide nanoparticles utilising aloe vera plant extract. The microwave approach was used to biosynthesize pure and 1.5 wt% Mg doped nanostructured zinc oxide utilising high purity metal nitrates and aloe vera plant extract. Diffuse reflectance spectroscopy (DRS), X-ray diffraction method (XRD), Fourier transform infrared spectroscopy (FT-IR), High resolution scanning electron microscope (HR-SEM), and Photoluminescence (PL) spectroscopy were used to characterise the synthesized doped zinc oxide nanoparicles. XRD analyses supported the formation of the hexagonal wurtzite structure in zinc oxide. The FT-IR method also supported the creation of the zinc oxide phase. DRS and PL were used to determine the optical characteristics. The band gap of 1.5 wt% Mg doped zinc oxide was found to be greater than that of pure zinc oxide.
Asian journal of chemical sciences, Apr 21, 2023
The data for the nonisothermal and isothermal thermal decompositions of lanthanum oxalate have be... more The data for the nonisothermal and isothermal thermal decompositions of lanthanum oxalate have been analysed using the model-free and model-fitting kinetic techniques. When applied to nonisothermal data using the Coat-Redfern(CR) equation, the widely used model-fitting approach that results excellent fitting for both isothermal and nonisothermal data but produces very ambiguous values of the Arrhenius parameters. These values cannot be compared to those obtained from isothermal experiments. On the other hand, the model-free strategy represented by the iso-conversional method, such as Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose
Asian Journal of Applied Chemistry Research
The Photocatalytic performance of the Calcium doped lanthanum manganite nanocomposite for photode... more The Photocatalytic performance of the Calcium doped lanthanum manganite nanocomposite for photodegradation of Methylene Blue(MB) dye as an Organic water pollutant,was evaluated over visible light irradiation, at a pH of 4, at constant dose for several hours. The result showed La0.75Ca0.25MnO3 having Perovskite structure shows high degree of catalytic efficiency of 69% within 100 min illumination time, for the removal of Methylene Blue organic dye from its aqueous solution. The sample powder(LCMO) was prepared through sol-gel technique and was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Inductively coupled plasma- atomic emission spectroscopy (ICP-AES), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX) and UV-Vis spectroscopy (UV-Vis). The XRD data revealed the formation of single phase crystallinity.SEM images shows that the micro sized La0.75Ca0.25MnO3 powder has nanocrystalline structure with average diame...
Transactions of Nonferrous Metals Society of China, 2016
Nanostructured zinc–copper mixed ferrite was synthesized using sol–gel method. Different composit... more Nanostructured zinc–copper mixed ferrite was synthesized using sol–gel method. Different compositions of ferrite, Zn(1–x)CuxFe2O4 (x=0.0, 0.25, 0.50, 0.75), characterized by XRD, reveal single phase inverse spinel in all the samples. With increasing copper content, the crystallite size increases. The surface morphology of all the samples, studied by SEM, shows porous structure of particles. The prepared samples were also analyzed by FT-IR and TEM. Catalytic activity of the samples was studied on lanthanum oxalate decomposition by thermogravimety. The rate constant k has the highest value with x=0.75 and 5% (mole fraction) of the catalyst and is attributed to high copper content, the mixed sites Cu2+−Fe + and/or Cu+−Fe2+ ion pairs besides the one component sites Cu2+−Cu+, Fe3+−Fe2+, as a result of mutual charge interaction. In other words, the increasing activity of mixed oxides is attributed to increase in the content of active sites via creation of new ion pairs. With increasing Zn content, particle size increases. Variation of catalytic activity of ferrite powders is due to the changes of the valence state of catalytically active components of the ferrites, which oxidizes the carbon monoxide released from lanthanum oxalate.
IOSR Journal of Applied Chemistry, 2014
A study on the thermal decomposition of the mixtures of lanthanum oxalate hydrate and transition ... more A study on the thermal decomposition of the mixtures of lanthanum oxalate hydrate and transition metal nano oxide compounds(TMNOCs) viz. CuO, Fe2O3, TiO2 and Cr2O3 of 5 mole% ratio has been carried out employing Thermogravimetry, Differential Thermal Analysis and chemical analysis. The results reveal that other than CuO the oxides have a retarding effect on the decomposition rate. There is a competition of rate between Fe2O3 and TiO2 mixture up to 696K after which the trend is reversed and Fe2O3 becomes relatively more catalytic than TiO2. The best explanation for catalytic activities of the oxides is made by taking the former as a function of electronic configuration of the metal rather than the electronic properties of the oxides. Abnormal behaviour of Cr2O3 may be attributed to an irreversible change in oxidation state of Cr 3+ during which it is oxidised to Cr 6+ prior to decomposition. The kinetic and thermodynamic parameters are evaluated in the light of F 3 mechanism in two d...
Thermochimica Acta, 2002
ABSTRACT A study on the thermal decomposition of mixtures of lanthanum oxalate hydrate and magnes... more ABSTRACT A study on the thermal decomposition of mixtures of lanthanum oxalate hydrate and magnesium chromite spinel, MgCr2O4 of different molar ratios has been carried out employing thermogravimetry, differential thermal analysis, chemical analysis, infrared spectroscopy and X-ray diffraction analysis. It is evident from the data that lanthanum oxalate in the presence of mixed oxide starts to decompose at a temperature higher than the pure salt. The results reveal that chromium oxide has a retarding effect on the decomposition rate and addition of magnesium oxide leads to an observable increase in the catalytic behaviour of Cr2O3 towards the decomposition below 440 °C, above which it increases significantly with increasing percentage of MgCr2O4. The induced defects during the formation of solid solution alters the conductive properties of the oxide, due to generation of more holes within the catalyst, consequently increasing its, activity towards decomposition. The kinetic and thermogravimetric parameters are evaluated in the light of D3 mechanism. The reaction occurs through three different stages and the rate constant, k is found to follow the order: and LO1>LO2>LO3 (653–713 K), LO1<LO2<LO3 (713–753 K), where LO1, LO2 and LO3 stand for different mole percentage mixtures of MgCr2O4 with lanthanum oxalate.
Lanthanum Oxalate decahydrate and Copper ferrites were prepared by chemical and sintering process... more Lanthanum Oxalate decahydrate and Copper ferrites were prepared by chemical and sintering process respectively and the detailed investigation of their properties was carried out successfully at room temperature by FTIR,XRD,SEM ,TEM as well as by chemical methods. Catalytic activity of copper ferrite over the decomposition of lanthanum oxalate was studied non isothermally by TG-DTA after mixing the former with the later in varying mole ratios. Also a physical mixture of CuO and Fe2O3 was prepared for comparative study. It is found that CuO has catalytic activity whereas Fe2O3 behaves as negative catalyst for the entire process. But the physical mixture enhances the rate of reaction at the low temperature and as the temperature becomes high the solid solution of copper ferrite is expected to be formed by valence induction generating ntype semi conduction in Fe2O3 resulting in a ferrite having inverse spinel structure and having high rate constant. There is no appreciable change in act...
Nanostructured zinc-copper mixed ferrite was synthesized using sol-gel method. XRD patterns of di... more Nanostructured zinc-copper mixed ferrite was synthesized using sol-gel method. XRD patterns of different compositions of zinc copper ferrite, Zn (1−) Cu Fe 2 O 4 (x = 0.0, 0.25, 0.50, 0.75), revealed single phase inverse spinel ferrite in all the samples. With increasing copper concentration, the crystallite size increases from 28 nm to 47 nm. The surface morphology of all the samples studied by the Scanning Electron Microscopy showing porous structure of particles throughout the sample. The prepared samples were also analysed by XRD,FTIR,TEM. Catalytic activity of the prepared samples were studied on lanthanum oxalate decomposition by Thermogravimetric methods(TGA).The rate constant 'k' has got the highest value with x=0.75 and 5 mol% concentration and highest value is attributed to high copper concentration and also due to the fact that, beside the one component sites Cu 2+-Cu + , Fe 3+-Fe 2+ , there will be also the mixed sites Cu 2+-Fe + and/or Cu +-Fe 2+ ion pairs as a result of mutual charge interaction.In other words, the increasing activity of mixed oxides might be attributed to increase in the concentration of active sites via creation of new ion pairs. With increasing Zn content increases particle size thereby providing comparatively less surface area for the catalytic activities due to large ionic radii of Zinc.Variation of catalytic activity of ferrite powders are probably due to the changes of the valence state of catalytically active components of the ferrite powders that oxidises the carbon monoxide released from Lanthanum oxalate
Research Paper, 2002
A study on the thermal decomposition of mixtures of lanthanum oxalate hydrate and magnesium chrom... more A study on the thermal decomposition of mixtures of lanthanum oxalate hydrate and magnesium chromite spinel, MgCr 2 O 4 of different molar ratios has been carried out employing thermogravimetry, differential thermal analysis, chemical analysis, infrared spectroscopy and X-ray diffraction analysis. It is evident from the data that lanthanum oxalate in the presence of mixed oxide starts to decompose at a temperature higher than the pure salt. The results reveal that chromium oxide has a retarding effect on the decomposition rate and addition of magnesium oxide leads to an observable increase in the catalytic behaviour of Cr 2 O 3 towards the decomposition below 440 8C, above which it increases signi®cantly with increasing percentage of MgCr 2 O 4. The induced defects during the formation of solid solution alters the conductive properties of the oxide, due to generation of more holes within the catalyst, consequently increasing its, activity towards decomposition. The kinetic and thermogravimetric parameters are evaluated in the light of D 3 mechanism. The reaction occurs through three different stages and the rate constant, k is found to follow the order: stage I > stage II < stage III and LO1 > LO2 > LO3 (653±713 K), LO1 < LO2 < LO3 (713±753 K), where LO1, LO2 and LO3 stand for different mole percentage mixtures of MgCr 2 O 4 with lanthanum oxalate.
A study on the thermal decomposition of mixtures of lanthanum oxalate hydrate and magnesium chrom... more A study on the thermal decomposition of mixtures of lanthanum oxalate hydrate and magnesium chromite spinel, MgCr 2 O 4 of different molar ratios has been carried out employing thermogravimetry, differential thermal analysis, chemical analysis, infrared spectroscopy and X-ray diffraction analysis. It is evident from the data that lanthanum oxalate in the presence of mixed oxide starts to decompose at a temperature higher than the pure salt. The results reveal that chromium oxide has a retarding effect on the decomposition rate and addition of magnesium oxide leads to an observable increase in the catalytic behaviour of Cr 2 O 3 towards the decomposition below 440 8C, above which it increases signi®cantly with increasing percentage of MgCr 2 O 4. The induced defects during the formation of solid solution alters the conductive properties of the oxide, due to generation of more holes within the catalyst, consequently increasing its, activity towards decomposition. The kinetic and thermogravimetric parameters are evaluated in the light of D 3 mechanism. The reaction occurs through three different stages and the rate constant, k is found to follow the order: stage I > stage II < stage III and LO1 > LO2 > LO3 (653±713 K), LO1 < LO2 < LO3 (713±753 K), where LO1, LO2 and LO3 stand for different mole percentage mixtures of MgCr 2 O 4 with lanthanum oxalate.
A study on the thermal decomposition of the mixtures of lanthanum oxalate hydrate and transition ... more A study on the thermal decomposition of the mixtures of lanthanum oxalate hydrate and transition metal nano oxide compounds(TMNOCs) viz. CuO, Fe 2 O 3 , TiO 2 and Cr 2 O 3 of 5 mole% ratio has been carried out employing Thermogravimetry, Differential Thermal Analysis and chemical analysis. The results reveal that other than CuO the oxides have a retarding effect on the decomposition rate. There is a competition of rate between Fe 2 O 3 and TiO 2 mixture up to 696K after which the trend is reversed and Fe 2 O 3 becomes relatively more catalytic than TiO 2. The best explanation for catalytic activities of the oxides is made by taking the former as a function of electronic configuration of the metal rather than the electronic properties of the oxides. Abnormal behaviour of Cr 2 O 3 may be attributed to an irreversible change in oxidation state of Cr 3+ during which it is oxidised to Cr 6 + prior to decomposition. The kinetic and thermodynamic parameters are evaluated in the light of F 3 mechanism in two different regions of α's and the rate follows the order:
Nanostructured zinc-copper mixed ferrite was synthesized using sol-gel method. XRD patterns of di... more Nanostructured zinc-copper mixed ferrite was synthesized using sol-gel method. XRD patterns of different compositions of zinc copper ferrite, Zn (1−) Cu Fe 2 O 4 (x = 0.0, 0.25, 0.50, 0.75), revealed single phase inverse spinel ferrite in all the samples. With increasing copper concentration, the crystallite size increases from 28 nm to 47 nm. The surface morphology of all the samples studied by the Scanning Electron Microscopy showing porous structure of particles throughout the sample. The prepared samples were also analysed by XRD,FTIR,TEM. Catalytic activity of the prepared samples were studied on lanthanum oxalate decomposition by Thermogravimetric methods(TGA).The rate constant 'k' has got the highest value with x=0.75 and 5 mol% concentration and highest value is attributed to high copper concentration and also due to the fact that, beside the one component sites Cu 2+-Cu + , Fe 3+-Fe 2+ , there will be also the mixed sites Cu 2+-Fe + and/or Cu +-Fe 2+ ion pairs as a result of mutual charge interaction.In other words, the increasing activity of mixed oxides might be attributed to increase in the concentration of active sites via creation of new ion pairs. With increasing Zn content increases particle size thereby providing comparatively less surface area for the catalytic activities due to large ionic radii of Zinc.Variation of catalytic activity of ferrite powders are probably due to the changes of the valence state of catalytically active components of the ferrite powders that oxidises the carbon monoxide released from Lanthanum oxalate
Research Paper, 2016
Nanostructured zinc−copper mixed ferrite was synthesized using sol−gel method. Different composit... more Nanostructured zinc−copper mixed ferrite was synthesized using sol−gel method. Different compositions of ferrite, Zn (1−x) Cu x Fe 2 O 4 (x=0.0, 0.25, 0.50, 0.75), characterized by XRD, reveal single phase inverse spinel in all the samples. With increasing copper content, the crystallite size increases. The surface morphology of all the samples, studied by SEM, shows porous structure of particles. The prepared samples were also analyzed by FT-IR and TEM. Catalytic activity of the samples was studied on lanthanum oxalate decomposition by thermogravimety .The rate constant k has the highest value with x=0.75 and 5% (mole fraction) of the catalyst and is attributed to high copper content, the mixed sites Cu 2+ −Fe + and/or Cu + −Fe 2+ ion pairs besides the one component sites Cu 2+ −Cu + , Fe 3+ −Fe 2+ , as a result of mutual charge interaction. In other words, the increasing activity of mixed oxides is attributed to increase in the content of active sites via creation of new ion pairs. With increasing Zn content, particle size increases. Variation of catalytic activity of ferrite powders is due to the changes of the valence state of catalytically active components of the ferrites, which oxidizes the carbon monoxide released from lanthanum oxalate.
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