This work involved the development of alumina/hydroxyapatite (Al2O3/HAp) composites for use as bo... more This work involved the development of alumina/hydroxyapatite (Al2O3/HAp) composites for use as bone graft material in maxillofacial reconstruction. The effect of introducing 20 and 30 wt% of hydroxyapatite into the alumina matrix was also investigated. The composites were produced from hydroxyapatite synthesized by the precipitation method, using commercial alumina as a matrix. Samples of the composite material were compacted under 260 MPa of isostatic pressure, followed by sintering at 1200°C/2h and characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), and diametral compression. The XRD results confirmed the presence of Al2O3 and Ca10(PO4)6(OH)2 – HAp crystalline phases in all composites. The addition of HAp to the alumina matrix inhibited alumina grain growth, reducing intergranular porosity and thus promoting greater densification and mechanical strength of the composites.
Evaluation of the catalytic effect of ZnO as a secondary phase in the Ni 0.5 Zn 0.5 Fe 2 O 4 syst... more Evaluation of the catalytic effect of ZnO as a secondary phase in the Ni 0.5 Zn 0.5 Fe 2 O 4 system and of the stirring mechanism on biodiesel production reaction,
Modo de acesso: World Wide Web Inclui bibliografia 1. Engenharia 2. Educação.I. Título. CDD-620 O... more Modo de acesso: World Wide Web Inclui bibliografia 1. Engenharia 2. Educação.I. Título. CDD-620 O conteúdo dos artigos e seus dados em sua forma, correção e confiabilidade são de responsabilidade exclusiva dos seus respectivos autores.
The aim of this work is to evaluate the esterification activity of ZnAl 2 O 4 catalysts obtained ... more The aim of this work is to evaluate the esterification activity of ZnAl 2 O 4 catalysts obtained by different ways of heating (plate, muffle furnace and microwave oven) during the combustion synthesis using urea as reducing agent, and nitrates of zinc and aluminum as oxidants. All samples were characterized by XRD, particle size distribution, nitrogen adsorption (BET/BJH) and SEM, and then, they were forwarded to the catalytic tests on the biodiesel esterification. XRD results showed that all catalysts presented the formation of a cubic structure of ZnAl 2 O 4 spinel. The heating way had a great influence on the structural and textural features of ZnAl 2 O 4 , such as crystallite size and surface area, whose values were of 27, 35 and 16 nm, and15, 9 and 57 m 2 /g for the catalysts I, II and III, respectively. All catalysts presented morphology in irregular plates shape (SEM) and formation of particle agglomerates with a narrow size distribution. For all catalysts tested, very low reactions profits were observed.
Abstract The synthesis of the Ni0.5-xZn0.5-xCu2xFe2O4 (x = 0; 0.10 and 0.15) ferrite with the dif... more Abstract The synthesis of the Ni0.5-xZn0.5-xCu2xFe2O4 (x = 0; 0.10 and 0.15) ferrite with the differential of pilot-scale production by the combustion reaction method was investigated for RAM application purposes. Combustion temperatures ranging from 682 °C to 738 °C were observed. All ferrites were sintered at 1200 °C for 1 h. A comprehensive study of the influence of substitution with Cu2+ in a partial and proportional way to the Ni2+ and Zn2+ ions, doping mode little reported in the literature, and also of the sintering process over the structural, textural, morphological, magnetic and electromagnetic properties of NiZnCu ferrites was performed. The XRD patterns of the ferrites as synthesized revealed the formation of the cubic structure of the inverse spinel as majoritary phase, and traces of hematite and zinc oxide as segregated phases. After sintering, it was proven the single-phase formation of cubic spinel ferrite structure. The introduction of Cu led to a reduction in the lattice parameter, whose values ranged from 8.337 to 8.385 A. The EDX results confirm the composition of oxides. The textural and morphological analyses confirmed the densest characteristic, with increase of particle size and reducing of surface area and pore volume after Cu-doping. All ferrites showed characteristics of soft ferrimagnetic material, where the increase in Cu content contributed to a slight reduction in saturation magnetization, whose values were of ~22–29 emu/g for the as synthesized ferrites and ~71–85 emu/g for the sintered ones. The best result of electromagnetic absorption in X-band was presented by the sintered ferrite with 0.3 mol of Cu, reaching an attenuation of 99.8% at 11.5 GHz frequency, thus confirming the efficiency of the pilot-scale combustion synthesis in obtaining a ferrite with great potential for RAM application.
Biodiesel is a biodegradable fuel derived from renewable biomass, such as soybean and cottonseed ... more Biodiesel is a biodegradable fuel derived from renewable biomass, such as soybean and cottonseed oil, which may be obtained by different processes and requires a material to catalyze the obtaining reactions. The irons spinel comes overlapping as excellent materials to catalyze the biodiesel production reactions. Thus, the purpose of this work was the use of Ni0.5Zn0.5Fe2O4 nanoferrite as a catalyst in esterification reactions. The nanoferrite was synthesized by combustion in large scale, 200g/batch, where time and the temperature of the reactions were measured, and characterized by XRD and measuring its surface area. The biodiesel was obtained from methyl and ethyl esterification of acidified soybean oil and cottonseed, at a temperature of 160°C for 1 hour, molar ratio 1:15, 3% of catalyst and analyzed by chromatography. The nanoferrite has shown peaks of greater intensity corresponding to a majority crystal phase of the spinel and a surface area of 64.17m2/g. The conversion resul...
Radar-absorbing materials (RAMs) have been used in military applications for several decades to r... more Radar-absorbing materials (RAMs) have been used in military applications for several decades to reduce radar detection of vessels and aircrafts. In the present work, the performance of Ni0.35Zn0.35Cu0.3Fe2O4 ferrite as a RAM is investigated. The ferrite was firstly synthesized by combustion reaction and then calcinated at 1200 °C for 1 h. Composites were prepared with 80:20, 70:30 and 60:40 concentrations in weight of ferrite:polychloroprene. The X-ray diffraction (XRD) analysis showed a single phase ferrite formation and the scanning electron microscopy (SEM) analysis of the composites showed a good dispersion of the ferrite in the polychloroprene matrix. The electromagnetic (EM) characterization of the composites revealed that the EM attenuation is mainly attributed to magnetic losses observed in the material. The 80:20 composite achieved the best performance and presented a reflectivity of -26.7 dB at 10.2 GHz.
Modo de acesso: World Wide Web Inclui bibliografia 1. Engenharia 2. Educação.I. Título CDD-620 O ... more Modo de acesso: World Wide Web Inclui bibliografia 1. Engenharia 2. Educação.I. Título CDD-620 O conteúdo dos artigos e seus dados em sua forma, correção e confiabilidade são de responsabilidade exclusiva dos seus respectivos autores.
Abstract This research proposes to obtain iron spinels MFe2O4, and their hybrids MFe2O4@SiO2 and ... more Abstract This research proposes to obtain iron spinels MFe2O4, and their hybrids MFe2O4@SiO2 and MFe2O4@SiO2/chitosan (M = Cu, Ni, Co, Mn e Fe) from the surface modification with (3-aminopropyl)trimethoxysilane agent and functionalization with chitosan, and then evaluate them as to their structure, morphology, magnetism and cytotoxicity, towards obtaining biocompatible hybrids for biological applications. The samples were analyzed by XRD, FTIR, SEM, TEM, magnetic measurements and in vitro cytotoxicity. XRD results showed that all samples presented the formation of the desired spinel major phase, with a crystallite size between 12 and 45 nm. According to the morphology and FTIR spectra of the samples, it was possible to confirm the formation of the hybrids. All samples presented soft magnetic material characteristics, exception given to the iron spinels CoFe2O4, which showed characteristic of hard magnetic material. The best results of cell viability were obtained by the CoFe2O4, MnFe2O4 e Fe3O4 MNPs and their hybrids.
Abstract It was proposed in this work to investigate the Cu 2+ ions doping influence in the struc... more Abstract It was proposed in this work to investigate the Cu 2+ ions doping influence in the structure, morphology and magnetic properties of nanoferrites Ni 0.5 Zn 0.5 Fe 2 O 4 for their application in methyl transesterification of soybean oil to biodiesel production. The nanoferrites with Ni 0.5−x Cu x Zn 0.5 Fe 2 O 4 composition (0.0 ⩽ x ⩽ 0.4) were synthesized by combustion reaction using a conical reactor with production of 10 g per batch and characterized by X-ray diffraction, textural analysis by N 2 adsorption, magnetic measurements, thermal analysis by temperature-programmed desorption, and biodiesel analysis by gas chromatography. All compositions resulted in the single phase of the inverse spinel type B(AB) 2 O 4 and adsorption/desorption isotherms of the same profile, classified as type V, with hysteresis loop type 3 (H3). However, the increase of Cu ions doping from 0.0 to 0.4 mol caused a reduction of 37% in the surface area values and 36.4% in the saturation magnetization value. However, this reduction remained the ferrimagnetic characteristic and that is still strongly attracted by a magnet. The Cu ions presence has also facilitated an increase of 5.5–85% in the conversion values in methyl esters obtained from soybean oil transesterification. These results indicate the potential application of NiZn nanoferrite compositions doped with Cu 2+ as heterogeneous nanocatalysts to produce biodiesel.
This work aims to evaluate the immobilization of glucose oxidase (GOx) with CoFe2O4 nanoparticles... more This work aims to evaluate the immobilization of glucose oxidase (GOx) with CoFe2O4 nanoparticles and hybrids CoFe2O4/APTS. The nanoparticles were synthesized by combustion reaction and silanized using 3-aminopropyltrimethoxysilane (APTS). The samples were characterized by XRD, FTIR, magnetic measurements and immobilization of GOx. The results indicated single phase of spinel CoFe2O4 and the addition of APTS did not alter the structure of the ferrite. The characteristic bands of spinel and characteristic bands were observed in the silane silanized sample proving the silanization of nanoparticles of CoFe2O4. The CoFe2O4 nanoparticles and the hybrid had saturation magnetization of 58.0 and 53.0 emu/g and coercivity of 1.14 kOe and 1.15, indicating that the silanization does not interfere with the magnetism of the particles. The immobilized GOx was obtained with values of 0.047 and 0.050 mg/g efficiency of 84.86 and 80.30% for CoFe2O4/APTS and CoFe2O4.
This work involved the development of alumina/hydroxyapatite (Al2O3/HAp) composites for use as bo... more This work involved the development of alumina/hydroxyapatite (Al2O3/HAp) composites for use as bone graft material in maxillofacial reconstruction. The effect of introducing 20 and 30 wt% of hydroxyapatite into the alumina matrix was also investigated. The composites were produced from hydroxyapatite synthesized by the precipitation method, using commercial alumina as a matrix. Samples of the composite material were compacted under 260 MPa of isostatic pressure, followed by sintering at 1200°C/2h and characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), and diametral compression. The XRD results confirmed the presence of Al2O3 and Ca10(PO4)6(OH)2 – HAp crystalline phases in all composites. The addition of HAp to the alumina matrix inhibited alumina grain growth, reducing intergranular porosity and thus promoting greater densification and mechanical strength of the composites.
Evaluation of the catalytic effect of ZnO as a secondary phase in the Ni 0.5 Zn 0.5 Fe 2 O 4 syst... more Evaluation of the catalytic effect of ZnO as a secondary phase in the Ni 0.5 Zn 0.5 Fe 2 O 4 system and of the stirring mechanism on biodiesel production reaction,
Modo de acesso: World Wide Web Inclui bibliografia 1. Engenharia 2. Educação.I. Título. CDD-620 O... more Modo de acesso: World Wide Web Inclui bibliografia 1. Engenharia 2. Educação.I. Título. CDD-620 O conteúdo dos artigos e seus dados em sua forma, correção e confiabilidade são de responsabilidade exclusiva dos seus respectivos autores.
The aim of this work is to evaluate the esterification activity of ZnAl 2 O 4 catalysts obtained ... more The aim of this work is to evaluate the esterification activity of ZnAl 2 O 4 catalysts obtained by different ways of heating (plate, muffle furnace and microwave oven) during the combustion synthesis using urea as reducing agent, and nitrates of zinc and aluminum as oxidants. All samples were characterized by XRD, particle size distribution, nitrogen adsorption (BET/BJH) and SEM, and then, they were forwarded to the catalytic tests on the biodiesel esterification. XRD results showed that all catalysts presented the formation of a cubic structure of ZnAl 2 O 4 spinel. The heating way had a great influence on the structural and textural features of ZnAl 2 O 4 , such as crystallite size and surface area, whose values were of 27, 35 and 16 nm, and15, 9 and 57 m 2 /g for the catalysts I, II and III, respectively. All catalysts presented morphology in irregular plates shape (SEM) and formation of particle agglomerates with a narrow size distribution. For all catalysts tested, very low reactions profits were observed.
Abstract The synthesis of the Ni0.5-xZn0.5-xCu2xFe2O4 (x = 0; 0.10 and 0.15) ferrite with the dif... more Abstract The synthesis of the Ni0.5-xZn0.5-xCu2xFe2O4 (x = 0; 0.10 and 0.15) ferrite with the differential of pilot-scale production by the combustion reaction method was investigated for RAM application purposes. Combustion temperatures ranging from 682 °C to 738 °C were observed. All ferrites were sintered at 1200 °C for 1 h. A comprehensive study of the influence of substitution with Cu2+ in a partial and proportional way to the Ni2+ and Zn2+ ions, doping mode little reported in the literature, and also of the sintering process over the structural, textural, morphological, magnetic and electromagnetic properties of NiZnCu ferrites was performed. The XRD patterns of the ferrites as synthesized revealed the formation of the cubic structure of the inverse spinel as majoritary phase, and traces of hematite and zinc oxide as segregated phases. After sintering, it was proven the single-phase formation of cubic spinel ferrite structure. The introduction of Cu led to a reduction in the lattice parameter, whose values ranged from 8.337 to 8.385 A. The EDX results confirm the composition of oxides. The textural and morphological analyses confirmed the densest characteristic, with increase of particle size and reducing of surface area and pore volume after Cu-doping. All ferrites showed characteristics of soft ferrimagnetic material, where the increase in Cu content contributed to a slight reduction in saturation magnetization, whose values were of ~22–29 emu/g for the as synthesized ferrites and ~71–85 emu/g for the sintered ones. The best result of electromagnetic absorption in X-band was presented by the sintered ferrite with 0.3 mol of Cu, reaching an attenuation of 99.8% at 11.5 GHz frequency, thus confirming the efficiency of the pilot-scale combustion synthesis in obtaining a ferrite with great potential for RAM application.
Biodiesel is a biodegradable fuel derived from renewable biomass, such as soybean and cottonseed ... more Biodiesel is a biodegradable fuel derived from renewable biomass, such as soybean and cottonseed oil, which may be obtained by different processes and requires a material to catalyze the obtaining reactions. The irons spinel comes overlapping as excellent materials to catalyze the biodiesel production reactions. Thus, the purpose of this work was the use of Ni0.5Zn0.5Fe2O4 nanoferrite as a catalyst in esterification reactions. The nanoferrite was synthesized by combustion in large scale, 200g/batch, where time and the temperature of the reactions were measured, and characterized by XRD and measuring its surface area. The biodiesel was obtained from methyl and ethyl esterification of acidified soybean oil and cottonseed, at a temperature of 160°C for 1 hour, molar ratio 1:15, 3% of catalyst and analyzed by chromatography. The nanoferrite has shown peaks of greater intensity corresponding to a majority crystal phase of the spinel and a surface area of 64.17m2/g. The conversion resul...
Radar-absorbing materials (RAMs) have been used in military applications for several decades to r... more Radar-absorbing materials (RAMs) have been used in military applications for several decades to reduce radar detection of vessels and aircrafts. In the present work, the performance of Ni0.35Zn0.35Cu0.3Fe2O4 ferrite as a RAM is investigated. The ferrite was firstly synthesized by combustion reaction and then calcinated at 1200 °C for 1 h. Composites were prepared with 80:20, 70:30 and 60:40 concentrations in weight of ferrite:polychloroprene. The X-ray diffraction (XRD) analysis showed a single phase ferrite formation and the scanning electron microscopy (SEM) analysis of the composites showed a good dispersion of the ferrite in the polychloroprene matrix. The electromagnetic (EM) characterization of the composites revealed that the EM attenuation is mainly attributed to magnetic losses observed in the material. The 80:20 composite achieved the best performance and presented a reflectivity of -26.7 dB at 10.2 GHz.
Modo de acesso: World Wide Web Inclui bibliografia 1. Engenharia 2. Educação.I. Título CDD-620 O ... more Modo de acesso: World Wide Web Inclui bibliografia 1. Engenharia 2. Educação.I. Título CDD-620 O conteúdo dos artigos e seus dados em sua forma, correção e confiabilidade são de responsabilidade exclusiva dos seus respectivos autores.
Abstract This research proposes to obtain iron spinels MFe2O4, and their hybrids MFe2O4@SiO2 and ... more Abstract This research proposes to obtain iron spinels MFe2O4, and their hybrids MFe2O4@SiO2 and MFe2O4@SiO2/chitosan (M = Cu, Ni, Co, Mn e Fe) from the surface modification with (3-aminopropyl)trimethoxysilane agent and functionalization with chitosan, and then evaluate them as to their structure, morphology, magnetism and cytotoxicity, towards obtaining biocompatible hybrids for biological applications. The samples were analyzed by XRD, FTIR, SEM, TEM, magnetic measurements and in vitro cytotoxicity. XRD results showed that all samples presented the formation of the desired spinel major phase, with a crystallite size between 12 and 45 nm. According to the morphology and FTIR spectra of the samples, it was possible to confirm the formation of the hybrids. All samples presented soft magnetic material characteristics, exception given to the iron spinels CoFe2O4, which showed characteristic of hard magnetic material. The best results of cell viability were obtained by the CoFe2O4, MnFe2O4 e Fe3O4 MNPs and their hybrids.
Abstract It was proposed in this work to investigate the Cu 2+ ions doping influence in the struc... more Abstract It was proposed in this work to investigate the Cu 2+ ions doping influence in the structure, morphology and magnetic properties of nanoferrites Ni 0.5 Zn 0.5 Fe 2 O 4 for their application in methyl transesterification of soybean oil to biodiesel production. The nanoferrites with Ni 0.5−x Cu x Zn 0.5 Fe 2 O 4 composition (0.0 ⩽ x ⩽ 0.4) were synthesized by combustion reaction using a conical reactor with production of 10 g per batch and characterized by X-ray diffraction, textural analysis by N 2 adsorption, magnetic measurements, thermal analysis by temperature-programmed desorption, and biodiesel analysis by gas chromatography. All compositions resulted in the single phase of the inverse spinel type B(AB) 2 O 4 and adsorption/desorption isotherms of the same profile, classified as type V, with hysteresis loop type 3 (H3). However, the increase of Cu ions doping from 0.0 to 0.4 mol caused a reduction of 37% in the surface area values and 36.4% in the saturation magnetization value. However, this reduction remained the ferrimagnetic characteristic and that is still strongly attracted by a magnet. The Cu ions presence has also facilitated an increase of 5.5–85% in the conversion values in methyl esters obtained from soybean oil transesterification. These results indicate the potential application of NiZn nanoferrite compositions doped with Cu 2+ as heterogeneous nanocatalysts to produce biodiesel.
This work aims to evaluate the immobilization of glucose oxidase (GOx) with CoFe2O4 nanoparticles... more This work aims to evaluate the immobilization of glucose oxidase (GOx) with CoFe2O4 nanoparticles and hybrids CoFe2O4/APTS. The nanoparticles were synthesized by combustion reaction and silanized using 3-aminopropyltrimethoxysilane (APTS). The samples were characterized by XRD, FTIR, magnetic measurements and immobilization of GOx. The results indicated single phase of spinel CoFe2O4 and the addition of APTS did not alter the structure of the ferrite. The characteristic bands of spinel and characteristic bands were observed in the silane silanized sample proving the silanization of nanoparticles of CoFe2O4. The CoFe2O4 nanoparticles and the hybrid had saturation magnetization of 58.0 and 53.0 emu/g and coercivity of 1.14 kOe and 1.15, indicating that the silanization does not interfere with the magnetism of the particles. The immobilized GOx was obtained with values of 0.047 and 0.050 mg/g efficiency of 84.86 and 80.30% for CoFe2O4/APTS and CoFe2O4.
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