The compatibility between direct coal liquefaction residue(DCLR) and five kinds of pure bitumen(Shell-90,SK-90, ZSY-70, DM-70 and KLMY-50) was evaluated in this study. The rheological characteristics, glass transition...The compatibility between direct coal liquefaction residue(DCLR) and five kinds of pure bitumen(Shell-90,SK-90, ZSY-70, DM-70 and KLMY-50) was evaluated in this study. The rheological characteristics, glass transition temperatures(T_g), solubility parameters(SP) and SARA(saturates, aromatics, resins, and asphaltenes) fractions of DCLR,five kinds of pure bitumen and their blends(named as DCLR modified bitumen) were measured using the dynamic shear rheometer(DSR), differential scanning calorimetry(DSC), viscosity, and SARA tests, respectively. And the compatibility between DCLR and pure bitumen was characterized with three approaches, viz. the Cole-Cole plot,T_g, and the solubility parameter difference(SPD) method. Since each method has its own working mechanism, the compatibility ranking for the DCLR and five kinds of pure bitumen is slightly different according to the three approaches. However, the difference is pretty close and sometimes can be ignored. The general compatibility ranking decreases in the following order: Shell-90≈SK-90>DM-70≈ZSY-70>KLMY-50, which is affected by the asphaltenes content and the colloid index(I_c) value in the pure bitumen. Pure bitumen with lower asphaltenes content and colloid index(I_c) value has better compatibility with DCLR.展开更多
Frequency-dependent dielectric constant,dielectric loss,AC conductivity values and complex impedance spectra of V_(2)O_(5)-added Ni-Co-Zn ferrites(Ni_(0.62)Co_(0.03)Zn_(0.35)Fe_(2)O_(4)+xV_(2)O_(5),where x=0,0.5,1 and...Frequency-dependent dielectric constant,dielectric loss,AC conductivity values and complex impedance spectra of V_(2)O_(5)-added Ni-Co-Zn ferrites(Ni_(0.62)Co_(0.03)Zn_(0.35)Fe_(2)O_(4)+xV_(2)O_(5),where x=0,0.5,1 and 1.5 wt.%)have been investigated at room tempera-ture.The dielectric properties of the samples follow the Maxwell-Wagner polarization model.An inverse relationship was found between dielectric constant and AC electrical resistivity for all the samples.The dielectric constants decreased with the addition of V_(2)O_(5),while the electrical resistivities of V_(2)O_(5)-added Ni-Co-Zn ferrites are found to be larger than that of pure Ni-Co-Zn ferrite.The AC conductivity was reduced with the addition of V_(2)O_(5)to Ni-Co-Zn ferrite at lower-frequency region.However,AC conductivity shows a sharp increase at higher-frequency region,which could be attributed to the enhancement of electron hopping between the Fe2+and Fe3+ions in the ferrite matrix due to the activity of the grains.The complex impedance spectroscopy results through Cole-Cole/Nyquist plot have demonstrated a single semicircular arc.It indicates that conduction mechanism takes place predominantly through the grain/bulk property,which could be ascribed to the larger grain size of V_(2)O_(5)-added Ni-Co-Zn ferrites.展开更多
The nanoparticles of Co1＋xMnxFe2-xO4 （0≤x ≤ 0.5） ferrite system are synthesized by solid-state reaction route using planetary ball milling technique to investigate structural, electrical and magnetic properties. ...The nanoparticles of Co1＋xMnxFe2-xO4 （0≤x ≤ 0.5） ferrite system are synthesized by solid-state reaction route using planetary ball milling technique to investigate structural, electrical and magnetic properties. The X-ray diffraction patterns confirm the inverse spinel structure with residual oxide phases. Three distinct regions of frequency response on dielectric constant are observed Co1.2sMn0.5Fe1.75O4 as determined by the Wayne Kerr Impedance Analyzer. The first two regions of frequency response 1.13-4.5 MHz and 4.5-6.5 MHz exhibit the normal behavior but the last region 6.5-10.5 MHz indicates its anomalous behavior due to concurrent contribution of O^2-, Fe^3＋, Co^2＋ and Mn^3＋ ions in the relaxation process for sintering effects （sintered at 700℃）. This anomalous behavior is found to be pronounced and significant for the sample of composition Co1.25Mn0.25Fe1.75O4, which may be suitable to be used in the frequency band filter over wide range of frequencies. The single peak of imaginary part of dielectric constant （ε＂） indicates that the conduction process in this sample is due to the grain boundary resistance. The pronounced increase of capacitance （C） as observed from 100 ℃ to 125 ~C in temperature dependent measurement （30-125℃） is expected to eause from the change of polarization across the grain boundary due to redistribution of ions by the thermal agitation. The variation of resistance （R） with temperature （30-125 ℃） is found to exhibit semieonducting behavior that resulted from the p-type carriers （Co^2＋/Co^3＋）. A significant increase of Z from 105 ℃ with the increase of temperature indicates the signature of phase transition from ferrimagnetic-to-ferromagnetic, which may be ascribed to the increase of Co content. The appearance of the single semicircular arc in the Cole-Cole plot may be attributed to the contribution of grain boundary resistance and correspond to the parallel equivalent circuit of resistor-capacitor （R-C） combination with展开更多
We supercooled fresh-cut onion at−5℃ for 12 h.After supercooling,the electric impedance properties of the samples were evaluated by electrical impedance spectroscopy over the frequency range of 42 Hz−5 MHz.The time-t...We supercooled fresh-cut onion at−5℃ for 12 h.After supercooling,the electric impedance properties of the samples were evaluated by electrical impedance spectroscopy over the frequency range of 42 Hz−5 MHz.The time-temperature profiles of samples indicated that the freezing point and supercooling point were−2.3℃±0.7℃ and−6.9℃±1.0℃,respectively.The results indicated that 34 of the 36 supercooled samples exhibited a definite circular arc in the Cole-Cole plot,which suggested that the cell membrane remained intact during supercooling.In the other two samples which did not exhibit a definite circular arc,the cell membrane had sustained serious damage during supercooling.Furthermore,there was large difference in drip loss percentage between supercooled samples exhibited a definite circular arc in the Cole-Cole plot and samples not exhibiting a definite circular arc.Our results suggest that fresh-cut onions can be supercooled at−5℃.展开更多
M-type barium hexaferrites with chemical composition Ba1-xDyxFe12-yCryO19(x = 0.0, 0.1, 0.2, and y =0.0, 0.4, 0.5) were synthesized via sol–gel auto-combustion method. The samples were pre-sintered at 400℃ for 3 h a...M-type barium hexaferrites with chemical composition Ba1-xDyxFe12-yCryO19(x = 0.0, 0.1, 0.2, and y =0.0, 0.4, 0.5) were synthesized via sol–gel auto-combustion method. The samples were pre-sintered at 400℃ for 3 h and sintered at 950℃ for 5 h. The changes in the structural, dielectric, and optical properties were studied after the substitution of Dy3+and Cr3+ions. X-ray diffraction(XRD) analysis confirms the formation of single phase hexaferrites with the absence of secondary phase. FTIR analysis gives an idea of the formation of hexaferrites with the appearance of two peaks at 438 cm-1and 589 cm-1. The field emission scanning electron micrographs(FESEM) show a combination of crystallites with large shapes close to hexagonal platelet-like shape and others with rice or rod-like shapes, whereas EDX and elemental analysis confirm the stoichiometry of prepared samples. The calculated band gap from UV-vis NIR spectroscopy spectra was found to decreases with increase in Dy3+–Cr3+substitution. The dielectric properties were explained on the basis of Maxwell–Wagner model. Enhancement of dielectric constant at higher frequencies was observed in all the samples. Low dielectric loss is also observed in all the samples and Cole–Cole plot shows that grain boundary resistance(Rgb) contribute most to the dielectric properties. The prepared samples exhibit properties that could be useful for optoelectronics and high frequency application.展开更多
基金sponsored by the National Natural Science Foundation of China (51478028 and 51778038)the Program for Changjiang Scholars and Innovative Research Team in Universities(IRT-17R06)
文摘The compatibility between direct coal liquefaction residue(DCLR) and five kinds of pure bitumen(Shell-90,SK-90, ZSY-70, DM-70 and KLMY-50) was evaluated in this study. The rheological characteristics, glass transition temperatures(T_g), solubility parameters(SP) and SARA(saturates, aromatics, resins, and asphaltenes) fractions of DCLR,five kinds of pure bitumen and their blends(named as DCLR modified bitumen) were measured using the dynamic shear rheometer(DSR), differential scanning calorimetry(DSC), viscosity, and SARA tests, respectively. And the compatibility between DCLR and pure bitumen was characterized with three approaches, viz. the Cole-Cole plot,T_g, and the solubility parameter difference(SPD) method. Since each method has its own working mechanism, the compatibility ranking for the DCLR and five kinds of pure bitumen is slightly different according to the three approaches. However, the difference is pretty close and sometimes can be ignored. The general compatibility ranking decreases in the following order: Shell-90≈SK-90>DM-70≈ZSY-70>KLMY-50, which is affected by the asphaltenes content and the colloid index(I_c) value in the pure bitumen. Pure bitumen with lower asphaltenes content and colloid index(I_c) value has better compatibility with DCLR.
文摘Frequency-dependent dielectric constant,dielectric loss,AC conductivity values and complex impedance spectra of V_(2)O_(5)-added Ni-Co-Zn ferrites(Ni_(0.62)Co_(0.03)Zn_(0.35)Fe_(2)O_(4)+xV_(2)O_(5),where x=0,0.5,1 and 1.5 wt.%)have been investigated at room tempera-ture.The dielectric properties of the samples follow the Maxwell-Wagner polarization model.An inverse relationship was found between dielectric constant and AC electrical resistivity for all the samples.The dielectric constants decreased with the addition of V_(2)O_(5),while the electrical resistivities of V_(2)O_(5)-added Ni-Co-Zn ferrites are found to be larger than that of pure Ni-Co-Zn ferrite.The AC conductivity was reduced with the addition of V_(2)O_(5)to Ni-Co-Zn ferrite at lower-frequency region.However,AC conductivity shows a sharp increase at higher-frequency region,which could be attributed to the enhancement of electron hopping between the Fe2+and Fe3+ions in the ferrite matrix due to the activity of the grains.The complex impedance spectroscopy results through Cole-Cole/Nyquist plot have demonstrated a single semicircular arc.It indicates that conduction mechanism takes place predominantly through the grain/bulk property,which could be ascribed to the larger grain size of V_(2)O_(5)-added Ni-Co-Zn ferrites.
文摘The nanoparticles of Co1＋xMnxFe2-xO4 （0≤x ≤ 0.5） ferrite system are synthesized by solid-state reaction route using planetary ball milling technique to investigate structural, electrical and magnetic properties. The X-ray diffraction patterns confirm the inverse spinel structure with residual oxide phases. Three distinct regions of frequency response on dielectric constant are observed Co1.2sMn0.5Fe1.75O4 as determined by the Wayne Kerr Impedance Analyzer. The first two regions of frequency response 1.13-4.5 MHz and 4.5-6.5 MHz exhibit the normal behavior but the last region 6.5-10.5 MHz indicates its anomalous behavior due to concurrent contribution of O^2-, Fe^3＋, Co^2＋ and Mn^3＋ ions in the relaxation process for sintering effects （sintered at 700℃）. This anomalous behavior is found to be pronounced and significant for the sample of composition Co1.25Mn0.25Fe1.75O4, which may be suitable to be used in the frequency band filter over wide range of frequencies. The single peak of imaginary part of dielectric constant （ε＂） indicates that the conduction process in this sample is due to the grain boundary resistance. The pronounced increase of capacitance （C） as observed from 100 ℃ to 125 ~C in temperature dependent measurement （30-125℃） is expected to eause from the change of polarization across the grain boundary due to redistribution of ions by the thermal agitation. The variation of resistance （R） with temperature （30-125 ℃） is found to exhibit semieonducting behavior that resulted from the p-type carriers （Co^2＋/Co^3＋）. A significant increase of Z from 105 ℃ with the increase of temperature indicates the signature of phase transition from ferrimagnetic-to-ferromagnetic, which may be ascribed to the increase of Co content. The appearance of the single semicircular arc in the Cole-Cole plot may be attributed to the contribution of grain boundary resistance and correspond to the parallel equivalent circuit of resistor-capacitor （R-C） combination with
基金This work was supported by JSPS KAKENHI,grant number JP16H05001[Grant-in-Aid for Scientific Research(B)]JP16K15010[Grant-in-Aid for Exploratory Research].
文摘We supercooled fresh-cut onion at−5℃ for 12 h.After supercooling,the electric impedance properties of the samples were evaluated by electrical impedance spectroscopy over the frequency range of 42 Hz−5 MHz.The time-temperature profiles of samples indicated that the freezing point and supercooling point were−2.3℃±0.7℃ and−6.9℃±1.0℃,respectively.The results indicated that 34 of the 36 supercooled samples exhibited a definite circular arc in the Cole-Cole plot,which suggested that the cell membrane remained intact during supercooling.In the other two samples which did not exhibit a definite circular arc,the cell membrane had sustained serious damage during supercooling.Furthermore,there was large difference in drip loss percentage between supercooled samples exhibited a definite circular arc in the Cole-Cole plot and samples not exhibiting a definite circular arc.Our results suggest that fresh-cut onions can be supercooled at−5℃.
文摘M-type barium hexaferrites with chemical composition Ba1-xDyxFe12-yCryO19(x = 0.0, 0.1, 0.2, and y =0.0, 0.4, 0.5) were synthesized via sol–gel auto-combustion method. The samples were pre-sintered at 400℃ for 3 h and sintered at 950℃ for 5 h. The changes in the structural, dielectric, and optical properties were studied after the substitution of Dy3+and Cr3+ions. X-ray diffraction(XRD) analysis confirms the formation of single phase hexaferrites with the absence of secondary phase. FTIR analysis gives an idea of the formation of hexaferrites with the appearance of two peaks at 438 cm-1and 589 cm-1. The field emission scanning electron micrographs(FESEM) show a combination of crystallites with large shapes close to hexagonal platelet-like shape and others with rice or rod-like shapes, whereas EDX and elemental analysis confirm the stoichiometry of prepared samples. The calculated band gap from UV-vis NIR spectroscopy spectra was found to decreases with increase in Dy3+–Cr3+substitution. The dielectric properties were explained on the basis of Maxwell–Wagner model. Enhancement of dielectric constant at higher frequencies was observed in all the samples. Low dielectric loss is also observed in all the samples and Cole–Cole plot shows that grain boundary resistance(Rgb) contribute most to the dielectric properties. The prepared samples exhibit properties that could be useful for optoelectronics and high frequency application.
