The series of Cr-Zn nano ferrites having the general composition Cr<sub>x</sub>ZnFe<sub>2-x</sub>O<sub>4</sub> (0 ≤ x ≤ 0.5) have been synthesized successfully in the nanocrystall...The series of Cr-Zn nano ferrites having the general composition Cr<sub>x</sub>ZnFe<sub>2-x</sub>O<sub>4</sub> (0 ≤ x ≤ 0.5) have been synthesized successfully in the nanocrystalline form using the sol-gel method. The samples were sintered at 900°C for 3 hours. The effect of chromium substitution on dielectric properties of Zn-ferrites is reported in this paper. The analysis of XRD patterns revealed the formation of single phase cubic spinel structure for all the Cr-Zn ferrite samples. The FTIR spectra show two strong absorption bands in the range of 400 - 600 cm<sup>-1</sup>, which corroborate the spinel structure of the samples. The average grain size was found to be in the nanometer range and of the order of 43 - 63 nm obtained using TEM images. The lattice parameter and crystallite size decrease with increase in Cr concentration (x). The investigation on dielectric constant (ε'), dissipation factor (D) and ac conductivity (σ<sub>ac</sub>) was carried out at a fixed frequency 1 kHz and in the frequency range of 100 Hz to 1 MHz at room temperature using LCR meter. The plots of dielectric constant (ε') versus frequency show the normal dielectric behavior of spinel ferrites. The value of ac conductivity (σ<sub>ac</sub>) increases with increase in frequency for all the compositions. The appearance of the peak for each composition in the dissipation factor versus frequency curve suggests the presence of relaxing dipoles in the Cr-Zn nano ferrite samples. It is also found that the shifting of the relaxation peak towards lower frequency side with an increase in chromium content (x) is due to the strengthening of dipole-dipole interactions. The composition and frequency dependence of the dielectric constant, dielectric loss and ac-conductivity are explained based on the Koop’s two-layer model, Maxwell-Wagner polarization process, and Debye relaxation theory.展开更多
Bismuth substituted cobalt nano ferrites with the chemical composition Co Bi<sub>x</sub> Fe<sub>2-x</sub> O<sub>4</sub> (x = 0.00, 0.05, 0.10, 0.15, 0.20 & 0.25) were prepared b...Bismuth substituted cobalt nano ferrites with the chemical composition Co Bi<sub>x</sub> Fe<sub>2-x</sub> O<sub>4</sub> (x = 0.00, 0.05, 0.10, 0.15, 0.20 & 0.25) were prepared by sol-gel combustion method. The phase identification of prepared samples is characterised by X-ray powder diffraction (XRD) method, which confirms the formation of a single phase fcc spinal structure. The mean crystallite sizes of all prepared samples were obtained within the range of 21 (±5) nm. Transmission Electron Microscopy (TEM) images also confirmed the crystallite size of all the synthesised samples was in nano range. With the effect of Bi<sup>3+</sup> ion substitution on spinal cobalt ferrite, the magnetic properties were investigated by using Vibration Sample Magnetometer (VSM). The obtained hysteresis (M-H) curves of all the samples were analysed under the applied magnetic field of range ± 10 K Oe at 300 K. The magnetic properties such as saturation magnetisation (M<sub>s</sub>), remnant magnetization (M<sub>r</sub>) and coercivity (H<sub>c</sub>) values are tabulated, which show a decrease in trend as the bismuth ion concentration increases. This is due to the addition of Bi<sup>3+</sup> ion in the place of Fe<sup>3+</sup> ion (octahedral site) and hence the Bi<sup>3+</sup>-Fe<sup>3+</sup> ion interaction predominates as compared with the Fe<sup>2+</sup>-Fe<sup>3+</sup> ion interaction. The data obtained from magnetic studies, the variation among the magnetic properties have been investigated for all the prepared samples.展开更多
In this study, nano ferrite materials were produced to replace costive industrial materials<span style="font-family:;" "=""> </span><span style="font-family:Verdana;"&...In this study, nano ferrite materials were produced to replace costive industrial materials<span style="font-family:;" "=""> </span><span style="font-family:Verdana;"><span style="font-size:10.0pt;font-family:" color:#943634;"=""><span style="font-family:Verdana;white-space:normal;">[1]</span></span><span style="font-size:10.0pt;font-family:;" "=""></span><span style="font-size:10.0pt;font-family:" times="" new="" roman","serif";"=""><span></span></span></span><span></span><span><span></span></span><span style="font-family:Verdana;">.</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">Ferrite nanoparticles are the interesting material due to their rich and unique physical and chemical properties. They find applications in catalysis, bio-processing, medicine, magnetic recording, adsorption, devices etc.</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">Using co-participation method, five nano ferrite samples Zn</span><sub><span style="font-family:Verdana;">0.5</span></sub><span style="font-family:Verdana;">Mg</span><sub><span style="font-family:Verdana;">0.5-x</span></sub><span style="font-family:Verdana;">Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> (x = 0.00, 0.10, 0.20, 0.30 and 0.40) were prepared. The electrical and optical properties of the Zn</span><sub><span style="font-family:Verdana;">0.5</span></sub><span style="font-family:Verdana;">Mg</span><sub><span style="font-family:Verdana;">0.5-x</span></sub><span style="font-family:Verdana;">Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> samples were studied using the Ultraviolet-visible (UV-Vis) spectroscopy. The results verified that the formation of the absorption coefficient of the five samples of Zn</span><sub><span style="font-family:Verdana;">0.5</span></sub><span style="font-family:Verdana;">Mg</span><sub><span style="font-family:Verdana;">0.5-x</span></sub><span style="font-family:Verdana;">Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> increased with the increase of Lithium (Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">). The energy band gap of the Zn</span><sub><span style="font-family:Verdana;">0.5</span></sub><span style="font-family:Verdana;">Mg</span><sub><span style="font-family:Verdana;">0.5-x</span></sub><span style="font-family:Verdana;">Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> samples ranged </span></span><span style="font-family:Verdana;">from</span><span style="font-family:Verdana;"> 3.28 to 3.12</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">eV</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">[1]</span><span style="font-family:;" "=""></span><span style="font-family:" minion="" pro="" capt","serif";"=""><span></span></span><span style="font-family:Verdana;">.</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">The extinction coefficient (K) for five samples of Zn</span><sub><span style="font-family:Verdana;">0.5</span></sub><span style="font-family:Verdana;">Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">Mg</span><sub><span style="font-family:Verdana;">0.5-x</span></sub><span style="font-family:Verdana;">Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> increased with the increase of Lithium (Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">) at 338 nm f</span></span><span style="font-family:Verdana;">ro</span><span style="font-family:Verdana;">m 0.074 to 0.207. The high magnitude of optical conductivity is (1.34</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">×</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">10</span><sup><span style="font-family:Verdana;">12</span></sup><span style="font-family:Verdana;"> sec<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;">) and the maximum value of electrical conductivity is 42</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">(Ω<sup>.</sup></span><span style="font-family:;" "=""><span><span style="font-family:Verdana;">cm)<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;">. This may due to the electrical and optical properties of lithium.</span></span></span>展开更多
Co-precipitation is an important issue in chemical analysis, where it is often undesirable, but in some cases, it can be exploited. The Zn0.5Mn0.5−xLi2xFe2O4 nanomaterials (x = 0.0, 0.1, 0.2, 0.3 and 0.4) wa...Co-precipitation is an important issue in chemical analysis, where it is often undesirable, but in some cases, it can be exploited. The Zn0.5Mn0.5−xLi2xFe2O4 nanomaterials (x = 0.0, 0.1, 0.2, 0.3 and 0.4) was afforded by utilizing co-precipitation method. The structural and optical characteristics were analyzed for the samples employing X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR) and Ultraviolet-visible spectrophotometer (UV-Vis). XRD revealed that the structure of certain nanoparticles is a cubic spinel with space group (Fd-3m) and crystallite size in the scale 124 - 150 nm. Lattice parameter was determined to increments with Li+1 and that may occur due to the larger ionic radius of the Li1+ ion. FTIR spectroscopy confirmed the form of spinel ferrite and explicated the properties of absorption bands approximately 593, 1111, 1385, 1640, 2922 and 3430. The energy band gap was estimated for all samples with diverse ratios and was observed in the range of 2.58 - 2.52 eV.展开更多
A simple, multi component, one-pot method has been reported for the synthesis of poly substituted imidazoles in presence of magnetically separable and recyclable spinel nano copper ferrite as heterogeneous catalyst by...A simple, multi component, one-pot method has been reported for the synthesis of poly substituted imidazoles in presence of magnetically separable and recyclable spinel nano copper ferrite as heterogeneous catalyst by the cyclo-condensation of benzil, aromatic aldehyde, ammonium acetate and substituted amines under ultrasonic irradiation. This method of preparation has many advantages compared to those methods which are previously reported in the literature. This methodology offers simple experimental procedure, milder reaction conditions and environmentally benign approach.展开更多
A microwave irradiated magnetically separable nano cobalt ferrite catalyzed green method for the synthesis of 4-phenyl-4H-pyrano[3,2-h]quinolin-2-amine and 2-amino-4-phenyl-4H-pyrano[3,2-h] quinoline-3-carbonitrile de...A microwave irradiated magnetically separable nano cobalt ferrite catalyzed green method for the synthesis of 4-phenyl-4H-pyrano[3,2-h]quinolin-2-amine and 2-amino-4-phenyl-4H-pyrano[3,2-h] quinoline-3-carbonitrile derivatives through cyclization of aromatic aldehyde, acetonitrile/malononitrile and 8-hydoxyquinoline is developed and presented in this paper. The cubic magnetic cobalt ferrite nano particles were synthesized by sol-gel citrate precursor method and characterized by FT-IR, XRD, SEM and TEM techniques and the structures of the synthesized pyranoquinoline derivatives were assigned by IR, MASS and 1</sup>H NMR techniques. The reaction is carried out in a domestic microwave oven with a heat-resistant microwave safe glass container with a lid.展开更多
A detailed investigation on the effect of preparation method on the structural,magnetic,and acidic properties of cobalt ferrite nanoparticles prepared by sol-gel and co-precipitation is presented.Citric acid and ethyl...A detailed investigation on the effect of preparation method on the structural,magnetic,and acidic properties of cobalt ferrite nanoparticles prepared by sol-gel and co-precipitation is presented.Citric acid and ethylene glycol were used as gelling agents,while sodium hydroxide and aqueous ammonia were used as precipitating agents.The resulting ferrites were calcined at 450℃ and 750℃.Sharper X-ray diffraction(XRD)peaks were observed for the samples calcined at 750℃,indicating greater crystallinity of the samples calcined at higher temperature.Average crystallite sizes fell in the ranges of 7.1-21.1 nm and 30.4-42.1 nm for the samples calcined at 450℃ and 750℃,respectively.The infrared spectra revealed two main absorption bands,the high frequency bandν1 around 600 cm^(-1) and the low frequency bandν2 around 400 cm^(-1) arising from stretching vibrations of the oxygen bond with the metal in the tetrahedral(A)and octahedral(B)sites in the spinel lattice.Agglomeration of particles was observed in the scanning electron microscopy(SEM)images.Magnetic parameters of CoFe_(2)O_(4) nanoparticles greatly depended on calcination temperature and preparation techniques.Ammonia temperature programmed desorption(TPD)measurements indicated that weak acid sites predominate medium strength sites,while the number of strong acid sites is the least.Cumulative acidity decreased for the samples calcined at higher temperature.The results underline the effect of preparation conditions on the morphology,crystallite size,and magnetic properties of nano ferrites.展开更多
文摘The series of Cr-Zn nano ferrites having the general composition Cr<sub>x</sub>ZnFe<sub>2-x</sub>O<sub>4</sub> (0 ≤ x ≤ 0.5) have been synthesized successfully in the nanocrystalline form using the sol-gel method. The samples were sintered at 900°C for 3 hours. The effect of chromium substitution on dielectric properties of Zn-ferrites is reported in this paper. The analysis of XRD patterns revealed the formation of single phase cubic spinel structure for all the Cr-Zn ferrite samples. The FTIR spectra show two strong absorption bands in the range of 400 - 600 cm<sup>-1</sup>, which corroborate the spinel structure of the samples. The average grain size was found to be in the nanometer range and of the order of 43 - 63 nm obtained using TEM images. The lattice parameter and crystallite size decrease with increase in Cr concentration (x). The investigation on dielectric constant (ε'), dissipation factor (D) and ac conductivity (σ<sub>ac</sub>) was carried out at a fixed frequency 1 kHz and in the frequency range of 100 Hz to 1 MHz at room temperature using LCR meter. The plots of dielectric constant (ε') versus frequency show the normal dielectric behavior of spinel ferrites. The value of ac conductivity (σ<sub>ac</sub>) increases with increase in frequency for all the compositions. The appearance of the peak for each composition in the dissipation factor versus frequency curve suggests the presence of relaxing dipoles in the Cr-Zn nano ferrite samples. It is also found that the shifting of the relaxation peak towards lower frequency side with an increase in chromium content (x) is due to the strengthening of dipole-dipole interactions. The composition and frequency dependence of the dielectric constant, dielectric loss and ac-conductivity are explained based on the Koop’s two-layer model, Maxwell-Wagner polarization process, and Debye relaxation theory.
文摘Bismuth substituted cobalt nano ferrites with the chemical composition Co Bi<sub>x</sub> Fe<sub>2-x</sub> O<sub>4</sub> (x = 0.00, 0.05, 0.10, 0.15, 0.20 & 0.25) were prepared by sol-gel combustion method. The phase identification of prepared samples is characterised by X-ray powder diffraction (XRD) method, which confirms the formation of a single phase fcc spinal structure. The mean crystallite sizes of all prepared samples were obtained within the range of 21 (±5) nm. Transmission Electron Microscopy (TEM) images also confirmed the crystallite size of all the synthesised samples was in nano range. With the effect of Bi<sup>3+</sup> ion substitution on spinal cobalt ferrite, the magnetic properties were investigated by using Vibration Sample Magnetometer (VSM). The obtained hysteresis (M-H) curves of all the samples were analysed under the applied magnetic field of range ± 10 K Oe at 300 K. The magnetic properties such as saturation magnetisation (M<sub>s</sub>), remnant magnetization (M<sub>r</sub>) and coercivity (H<sub>c</sub>) values are tabulated, which show a decrease in trend as the bismuth ion concentration increases. This is due to the addition of Bi<sup>3+</sup> ion in the place of Fe<sup>3+</sup> ion (octahedral site) and hence the Bi<sup>3+</sup>-Fe<sup>3+</sup> ion interaction predominates as compared with the Fe<sup>2+</sup>-Fe<sup>3+</sup> ion interaction. The data obtained from magnetic studies, the variation among the magnetic properties have been investigated for all the prepared samples.
文摘In this study, nano ferrite materials were produced to replace costive industrial materials<span style="font-family:;" "=""> </span><span style="font-family:Verdana;"><span style="font-size:10.0pt;font-family:" color:#943634;"=""><span style="font-family:Verdana;white-space:normal;">[1]</span></span><span style="font-size:10.0pt;font-family:;" "=""></span><span style="font-size:10.0pt;font-family:" times="" new="" roman","serif";"=""><span></span></span></span><span></span><span><span></span></span><span style="font-family:Verdana;">.</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">Ferrite nanoparticles are the interesting material due to their rich and unique physical and chemical properties. They find applications in catalysis, bio-processing, medicine, magnetic recording, adsorption, devices etc.</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">Using co-participation method, five nano ferrite samples Zn</span><sub><span style="font-family:Verdana;">0.5</span></sub><span style="font-family:Verdana;">Mg</span><sub><span style="font-family:Verdana;">0.5-x</span></sub><span style="font-family:Verdana;">Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> (x = 0.00, 0.10, 0.20, 0.30 and 0.40) were prepared. The electrical and optical properties of the Zn</span><sub><span style="font-family:Verdana;">0.5</span></sub><span style="font-family:Verdana;">Mg</span><sub><span style="font-family:Verdana;">0.5-x</span></sub><span style="font-family:Verdana;">Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> samples were studied using the Ultraviolet-visible (UV-Vis) spectroscopy. The results verified that the formation of the absorption coefficient of the five samples of Zn</span><sub><span style="font-family:Verdana;">0.5</span></sub><span style="font-family:Verdana;">Mg</span><sub><span style="font-family:Verdana;">0.5-x</span></sub><span style="font-family:Verdana;">Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> increased with the increase of Lithium (Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">). The energy band gap of the Zn</span><sub><span style="font-family:Verdana;">0.5</span></sub><span style="font-family:Verdana;">Mg</span><sub><span style="font-family:Verdana;">0.5-x</span></sub><span style="font-family:Verdana;">Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> samples ranged </span></span><span style="font-family:Verdana;">from</span><span style="font-family:Verdana;"> 3.28 to 3.12</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">eV</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">[1]</span><span style="font-family:;" "=""></span><span style="font-family:" minion="" pro="" capt","serif";"=""><span></span></span><span style="font-family:Verdana;">.</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">The extinction coefficient (K) for five samples of Zn</span><sub><span style="font-family:Verdana;">0.5</span></sub><span style="font-family:Verdana;">Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">Mg</span><sub><span style="font-family:Verdana;">0.5-x</span></sub><span style="font-family:Verdana;">Fe</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;">O</span><sub><span style="font-family:Verdana;">4</span></sub><span style="font-family:Verdana;"> increased with the increase of Lithium (Li</span><sub><span style="font-family:Verdana;">2x</span></sub><span style="font-family:Verdana;">) at 338 nm f</span></span><span style="font-family:Verdana;">ro</span><span style="font-family:Verdana;">m 0.074 to 0.207. The high magnitude of optical conductivity is (1.34</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">×</span><span style="font-family:;" "=""> </span><span style="font-family:;" "=""><span style="font-family:Verdana;">10</span><sup><span style="font-family:Verdana;">12</span></sup><span style="font-family:Verdana;"> sec<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;">) and the maximum value of electrical conductivity is 42</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">(Ω<sup>.</sup></span><span style="font-family:;" "=""><span><span style="font-family:Verdana;">cm)<span style="font-size:10px;"><sup>-1</sup></span></span><span style="font-family:Verdana;">. This may due to the electrical and optical properties of lithium.</span></span></span>
文摘Co-precipitation is an important issue in chemical analysis, where it is often undesirable, but in some cases, it can be exploited. The Zn0.5Mn0.5−xLi2xFe2O4 nanomaterials (x = 0.0, 0.1, 0.2, 0.3 and 0.4) was afforded by utilizing co-precipitation method. The structural and optical characteristics were analyzed for the samples employing X-ray diffraction (XRD), Fourier transforms infrared spectroscopy (FTIR) and Ultraviolet-visible spectrophotometer (UV-Vis). XRD revealed that the structure of certain nanoparticles is a cubic spinel with space group (Fd-3m) and crystallite size in the scale 124 - 150 nm. Lattice parameter was determined to increments with Li+1 and that may occur due to the larger ionic radius of the Li1+ ion. FTIR spectroscopy confirmed the form of spinel ferrite and explicated the properties of absorption bands approximately 593, 1111, 1385, 1640, 2922 and 3430. The energy band gap was estimated for all samples with diverse ratios and was observed in the range of 2.58 - 2.52 eV.
文摘A simple, multi component, one-pot method has been reported for the synthesis of poly substituted imidazoles in presence of magnetically separable and recyclable spinel nano copper ferrite as heterogeneous catalyst by the cyclo-condensation of benzil, aromatic aldehyde, ammonium acetate and substituted amines under ultrasonic irradiation. This method of preparation has many advantages compared to those methods which are previously reported in the literature. This methodology offers simple experimental procedure, milder reaction conditions and environmentally benign approach.
文摘A microwave irradiated magnetically separable nano cobalt ferrite catalyzed green method for the synthesis of 4-phenyl-4H-pyrano[3,2-h]quinolin-2-amine and 2-amino-4-phenyl-4H-pyrano[3,2-h] quinoline-3-carbonitrile derivatives through cyclization of aromatic aldehyde, acetonitrile/malononitrile and 8-hydoxyquinoline is developed and presented in this paper. The cubic magnetic cobalt ferrite nano particles were synthesized by sol-gel citrate precursor method and characterized by FT-IR, XRD, SEM and TEM techniques and the structures of the synthesized pyranoquinoline derivatives were assigned by IR, MASS and 1</sup>H NMR techniques. The reaction is carried out in a domestic microwave oven with a heat-resistant microwave safe glass container with a lid.
文摘A detailed investigation on the effect of preparation method on the structural,magnetic,and acidic properties of cobalt ferrite nanoparticles prepared by sol-gel and co-precipitation is presented.Citric acid and ethylene glycol were used as gelling agents,while sodium hydroxide and aqueous ammonia were used as precipitating agents.The resulting ferrites were calcined at 450℃ and 750℃.Sharper X-ray diffraction(XRD)peaks were observed for the samples calcined at 750℃,indicating greater crystallinity of the samples calcined at higher temperature.Average crystallite sizes fell in the ranges of 7.1-21.1 nm and 30.4-42.1 nm for the samples calcined at 450℃ and 750℃,respectively.The infrared spectra revealed two main absorption bands,the high frequency bandν1 around 600 cm^(-1) and the low frequency bandν2 around 400 cm^(-1) arising from stretching vibrations of the oxygen bond with the metal in the tetrahedral(A)and octahedral(B)sites in the spinel lattice.Agglomeration of particles was observed in the scanning electron microscopy(SEM)images.Magnetic parameters of CoFe_(2)O_(4) nanoparticles greatly depended on calcination temperature and preparation techniques.Ammonia temperature programmed desorption(TPD)measurements indicated that weak acid sites predominate medium strength sites,while the number of strong acid sites is the least.Cumulative acidity decreased for the samples calcined at higher temperature.The results underline the effect of preparation conditions on the morphology,crystallite size,and magnetic properties of nano ferrites.
