Both the band filling effect and Fe/Mo disorder have a close correlation with the physical properties of the double perovskite Ca2FeMoO6. Two series of Ca2FeMoO6and Nd0.3Ca1.7FeMoO6ceramics sintered at(1050℃, 1200℃,...Both the band filling effect and Fe/Mo disorder have a close correlation with the physical properties of the double perovskite Ca2FeMoO6. Two series of Ca2FeMoO6and Nd0.3Ca1.7FeMoO6ceramics sintered at(1050℃, 1200℃, and 1300℃) were specially designed to comparatively investigate the band-filling effect and Fe/Mo disorder on the physical properties of Ca2FeMoO6. The x-ray diffraction indicates that Fe/Mo disorder is sensitive to the sintering temperature. The magnetization behavior is mainly controlled by the Fe/Mo disorder not by the band filling effect, manifested by a close correlation of saturated magnetization(Ms) with the Fe/Mo disorder. Interestingly, magnetoresistance(MR) property of the same composition is dominantly contributed by the grain boundary strength, which can be expressed by the macroscopic resistivity values. However, the band filling effect caused by the Nd-substitution can decrease the spin polarization, and thus suppress the MR performance fundamentally. Contrary to the MR response, the Curie temperature(TC) shows an obvious optimization due to the band filling effect, which increases the carrier density near the Fermi level responsible for the ferromagnetic coupling interaction strengthen. Maybe, our work can provoke further research interests into the correlation of the band-filling effects and Fe/Mo disorder with the physical properties of other Fe/Mo-based double perovskites.展开更多
Multi-walled carbon nanotubes (MWCNTs) have been successfully modified with TiO2 nanoparticles via wet chemical method. For this purpose tetra chloride titanium (TiCl4) was used as titanium source. MWCNTs were exposed...Multi-walled carbon nanotubes (MWCNTs) have been successfully modified with TiO2 nanoparticles via wet chemical method. For this purpose tetra chloride titanium (TiCl4) was used as titanium source. MWCNTs were exposed at different amount of TiCl4 (0.25 and 0.1 ml) and different soaking times. The modified MWCNTs have been characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). TEM results showed that the MWCNTs were fully decorated with TiO2 at short term immersion. Increasing soaking time caused to fill the MWCNTs with TiO2 nanoparticles. The results showed that the amount of precursor had a significant role on quantity of decoration. The decoration of outer surface of MWCNTs with TiO2 was more noticeable at large amount of TiCl4. XRD results revealed that the crystalline structure of TiO2 on the surface and inner of MWCNTs was rutile. The average size of TiO2 nanoparticles which modified MWCNTs were 20 nm.展开更多
The pozzolanic activity of nano-SiO2 and silica fume was comparatirely stndied by X-ray diffraction （ XRD ） , differential scanning calorimetry （DSC）, scanning electron micrascopy （SEM） and the compressive , bon...The pozzolanic activity of nano-SiO2 and silica fume was comparatirely stndied by X-ray diffraction （ XRD ） , differential scanning calorimetry （DSC）, scanning electron micrascopy （SEM） and the compressive , bond and bending streugths of hardened paste and concrete were also measured. Results indicate that the compressive strength development of the paste made from Ca（OH）2 and nano-SiO2, the reaction rate of Ca（ OH）2 with nano- SiO2 and the velocity of C-S-H gel formation from Ca （ OH）2 with nano-SiO2 showed marked increases over those of Ca（ OH）2 with silica fume. Furthermore, the bond strength at the interface between aggregate and hardened cement paste, and the bending strength of concrete incorporated with 3% .NS increased more than those with SF, especially at early ages. To sum up, the pozzolanic activity of nano-SiO2 was much greater than that of silica fume. The results suggest that with a small amount of nano-SiO2, the Ca（ OH）2 crystal at the interface between hardened cement paste and aggregate at early ages may be effectively absorbed in high performance concrete.展开更多
We put forward a large-area and cost-effective method to fabricate superhydrophobic coating by introducing in-situ functionalized nano-SiO2 into side-amino modified hydroxy-terminated polydimethylsiloxane （SA-HTPDMS...We put forward a large-area and cost-effective method to fabricate superhydrophobic coating by introducing in-situ functionalized nano-SiO2 into side-amino modified hydroxy-terminated polydimethylsiloxane （SA-HTPDMS） curing system. With the characterization using water contact angle （WCA） tester, Fourier transform infrared spectroscopy （FTIR）, scanning electron microscope （SEM）, atomic force microscopy （AFM） and simultaneous thermal analysis, the as-prepared coating displayed a tremendous WCA of 154.8±1°, sliding angle （SA） about 3.5° and stable self-cleaning property range from -10 to 80 ℃. It was also found that the synergistic effect of surface micro-nano hierarchical structure and chemical hydrophobicity, stability from matrix had made contributions to the superhydrophobicity and excellent heat resistance up to 300 ℃.展开更多
A series of nano silica/silicone modified waterborne polyurethane(WPU) have been synthesized from polytetramethylene glycol and isophorone diisocyanate, dihydroxymethyl propionic acid and triethylamine, ethylenediamin...A series of nano silica/silicone modified waterborne polyurethane(WPU) have been synthesized from polytetramethylene glycol and isophorone diisocyanate, dihydroxymethyl propionic acid and triethylamine, ethylenediamine, trimethylolpropane, nano-SiO2 and the silane coupling agent KH550. The effect of the dosage of nano-SiO2 on the WPU-Si membrane and the coated RDX(cyclotrimethylenetrinitramine) particles have been studied in terms of their surface properties, mechanical properties, and thermal stability. The results showed that with the increase of Si content, the stability of the emulsion reduced gradually. The material with more Si content displayed an increased thermodynamic stability, an increased high temperature resistance, an increased tensile strength and a decreased elongation at break. With the increase of Si content, the surface tension of the material decreased, the bibulous rate reduced, and the contact angle increased gradually, so that the surface tension of the polyurethane and RDX are close to each other which could improve the performance of coating.展开更多
The influences of different nano-SiO2（NS） contents on the mechanical properties and rheological behavior of sulfoaluminate cement（SAC） based composite materials were studied.Results show that with increasing conte...The influences of different nano-SiO2（NS） contents on the mechanical properties and rheological behavior of sulfoaluminate cement（SAC） based composite materials were studied.Results show that with increasing content of NS,the apparent viscosity,and shearing strength of fresh paste gradually increase but the fluidity decreases.With a dosage of 3.0%NS,the tensile and flexural strengths of mortars at 56 days were increased by 87.0%and 84.6%,respectively,compared with that in the absence of NS,indicating that the toughness of hardened mortars is significantly improved.Besides,the exothermic peaks of hydration are obviously increased and will earlier occur,and the second and the third peaks appear 2.61 hours and 2.56 hours earlier,respectively than that in the absence of NS,and the hydration of SAC before 8 hours is accelerated.The forming mechanism of strengths was revealed by scanning electron microscopy（SEM）,hydration heat,X-ray diffraction（XRD） and derivative thermogravimetry（DTG）.The micro-aggregate filling effect and nucleation effect at early age and weak pozzolanic effect at late age of NS make the microstructure more compact,which obviously enhances the strength of SAC mortars.展开更多
The test of fast-freezing method is employed to research the freezing resistance of C60 and C80 high-performance concrete with nanometer-SiO2, and XRD and SEM are employed to analyze the mechanism of its influence. Th...The test of fast-freezing method is employed to research the freezing resistance of C60 and C80 high-performance concrete with nanometer-SiO2, and XRD and SEM are employed to analyze the mechanism of its influence. The experimental results show that the freezing resistance of high-performance concrete has been effectively improved. The compressive strength of C60, C70 and C80 high-performance concrete added with nano-SiO2 can be improved by 8%, 6% and 5% respectively, the weight loss can be reduced by 1%, 0.6% and 0.3% respectively and the relative dynamic elastic modulus can be improved by 7%, 4% and 6% respectively after the 300 times freeze-thaw cycle.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.U1504107)the Doctoral Scientific Research Foundation(Grant No.qd15214)
文摘Both the band filling effect and Fe/Mo disorder have a close correlation with the physical properties of the double perovskite Ca2FeMoO6. Two series of Ca2FeMoO6and Nd0.3Ca1.7FeMoO6ceramics sintered at(1050℃, 1200℃, and 1300℃) were specially designed to comparatively investigate the band-filling effect and Fe/Mo disorder on the physical properties of Ca2FeMoO6. The x-ray diffraction indicates that Fe/Mo disorder is sensitive to the sintering temperature. The magnetization behavior is mainly controlled by the Fe/Mo disorder not by the band filling effect, manifested by a close correlation of saturated magnetization(Ms) with the Fe/Mo disorder. Interestingly, magnetoresistance(MR) property of the same composition is dominantly contributed by the grain boundary strength, which can be expressed by the macroscopic resistivity values. However, the band filling effect caused by the Nd-substitution can decrease the spin polarization, and thus suppress the MR performance fundamentally. Contrary to the MR response, the Curie temperature(TC) shows an obvious optimization due to the band filling effect, which increases the carrier density near the Fermi level responsible for the ferromagnetic coupling interaction strengthen. Maybe, our work can provoke further research interests into the correlation of the band-filling effects and Fe/Mo disorder with the physical properties of other Fe/Mo-based double perovskites.
文摘Multi-walled carbon nanotubes (MWCNTs) have been successfully modified with TiO2 nanoparticles via wet chemical method. For this purpose tetra chloride titanium (TiCl4) was used as titanium source. MWCNTs were exposed at different amount of TiCl4 (0.25 and 0.1 ml) and different soaking times. The modified MWCNTs have been characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). TEM results showed that the MWCNTs were fully decorated with TiO2 at short term immersion. Increasing soaking time caused to fill the MWCNTs with TiO2 nanoparticles. The results showed that the amount of precursor had a significant role on quantity of decoration. The decoration of outer surface of MWCNTs with TiO2 was more noticeable at large amount of TiCl4. XRD results revealed that the crystalline structure of TiO2 on the surface and inner of MWCNTs was rutile. The average size of TiO2 nanoparticles which modified MWCNTs were 20 nm.
基金Funded bythe Center of Science Research, Zhejiang Universityof Technology of China
文摘The pozzolanic activity of nano-SiO2 and silica fume was comparatirely stndied by X-ray diffraction （ XRD ） , differential scanning calorimetry （DSC）, scanning electron micrascopy （SEM） and the compressive , bond and bending streugths of hardened paste and concrete were also measured. Results indicate that the compressive strength development of the paste made from Ca（OH）2 and nano-SiO2, the reaction rate of Ca（ OH）2 with nano- SiO2 and the velocity of C-S-H gel formation from Ca （ OH）2 with nano-SiO2 showed marked increases over those of Ca（ OH）2 with silica fume. Furthermore, the bond strength at the interface between aggregate and hardened cement paste, and the bending strength of concrete incorporated with 3% .NS increased more than those with SF, especially at early ages. To sum up, the pozzolanic activity of nano-SiO2 was much greater than that of silica fume. The results suggest that with a small amount of nano-SiO2, the Ca（ OH）2 crystal at the interface between hardened cement paste and aggregate at early ages may be effectively absorbed in high performance concrete.
基金Supported by National High Technology Research and Development ProgramofChina(863Program)(No.2003AA305920)
文摘We put forward a large-area and cost-effective method to fabricate superhydrophobic coating by introducing in-situ functionalized nano-SiO2 into side-amino modified hydroxy-terminated polydimethylsiloxane （SA-HTPDMS） curing system. With the characterization using water contact angle （WCA） tester, Fourier transform infrared spectroscopy （FTIR）, scanning electron microscope （SEM）, atomic force microscopy （AFM） and simultaneous thermal analysis, the as-prepared coating displayed a tremendous WCA of 154.8±1°, sliding angle （SA） about 3.5° and stable self-cleaning property range from -10 to 80 ℃. It was also found that the synergistic effect of surface micro-nano hierarchical structure and chemical hydrophobicity, stability from matrix had made contributions to the superhydrophobicity and excellent heat resistance up to 300 ℃.
基金the financial support by the National Natural Science Foundation of China(No.20973022 and No.11472048)
文摘A series of nano silica/silicone modified waterborne polyurethane(WPU) have been synthesized from polytetramethylene glycol and isophorone diisocyanate, dihydroxymethyl propionic acid and triethylamine, ethylenediamine, trimethylolpropane, nano-SiO2 and the silane coupling agent KH550. The effect of the dosage of nano-SiO2 on the WPU-Si membrane and the coated RDX(cyclotrimethylenetrinitramine) particles have been studied in terms of their surface properties, mechanical properties, and thermal stability. The results showed that with the increase of Si content, the stability of the emulsion reduced gradually. The material with more Si content displayed an increased thermodynamic stability, an increased high temperature resistance, an increased tensile strength and a decreased elongation at break. With the increase of Si content, the surface tension of the material decreased, the bibulous rate reduced, and the contact angle increased gradually, so that the surface tension of the polyurethane and RDX are close to each other which could improve the performance of coating.
基金Funded by the Fundamental Research Funds for the Central Universities(No.2013-YB-25)the National Natural Science Foundation of China(No.51378408)
文摘The influences of different nano-SiO2（NS） contents on the mechanical properties and rheological behavior of sulfoaluminate cement（SAC） based composite materials were studied.Results show that with increasing content of NS,the apparent viscosity,and shearing strength of fresh paste gradually increase but the fluidity decreases.With a dosage of 3.0%NS,the tensile and flexural strengths of mortars at 56 days were increased by 87.0%and 84.6%,respectively,compared with that in the absence of NS,indicating that the toughness of hardened mortars is significantly improved.Besides,the exothermic peaks of hydration are obviously increased and will earlier occur,and the second and the third peaks appear 2.61 hours and 2.56 hours earlier,respectively than that in the absence of NS,and the hydration of SAC before 8 hours is accelerated.The forming mechanism of strengths was revealed by scanning electron microscopy（SEM）,hydration heat,X-ray diffraction（XRD） and derivative thermogravimetry（DTG）.The micro-aggregate filling effect and nucleation effect at early age and weak pozzolanic effect at late age of NS make the microstructure more compact,which obviously enhances the strength of SAC mortars.
文摘The test of fast-freezing method is employed to research the freezing resistance of C60 and C80 high-performance concrete with nanometer-SiO2, and XRD and SEM are employed to analyze the mechanism of its influence. The experimental results show that the freezing resistance of high-performance concrete has been effectively improved. The compressive strength of C60, C70 and C80 high-performance concrete added with nano-SiO2 can be improved by 8%, 6% and 5% respectively, the weight loss can be reduced by 1%, 0.6% and 0.3% respectively and the relative dynamic elastic modulus can be improved by 7%, 4% and 6% respectively after the 300 times freeze-thaw cycle.
