为了制备具有远程可控变形且性能优越的形状记忆聚合物,采用巯基-烯点击化学法制备了PCL/CB复合材料,并用FTIR、DSC、1 H NMR和DMA对复合材料的结构、热性能以及形状记忆特性等进行表征。结果表明:交联复合材料薄膜的热转变温度为50℃,...为了制备具有远程可控变形且性能优越的形状记忆聚合物,采用巯基-烯点击化学法制备了PCL/CB复合材料,并用FTIR、DSC、1 H NMR和DMA对复合材料的结构、热性能以及形状记忆特性等进行表征。结果表明:交联复合材料薄膜的热转变温度为50℃,且当预拉伸的复合材料薄膜受到100 mW/cm^(2)强度的激光照射时,CB颗粒吸收激光光子而产生光热转换且由于各向异性链松弛和应变能释放,致使上层薄膜在受到激光照射时,结晶熔融发生形状记忆效应而收缩,与此同时下层薄膜仍然处于玻璃态,上层薄膜的收缩力使PCL/CB复合材料薄膜朝着激光照射方向发生弯曲变形。同时,弯曲角度可以通过薄膜预拉伸应变量、激光照射时间以及薄膜厚度3个参数进行调控;当预拉伸应变为300%、薄膜厚度为0.4 mm时,最大弯曲角为164°。这种具备局部可编程行为的PCL/CB复合薄膜可为光响应SMP的变形模式提供新思路。展开更多
DMPP （3,4-dimethylpyrazole phosphate） has been used to reduce nitrogen （N） loss from leaching or denitrification and to improve N supply in agricultural land. However, its impact on soil nitrifying organisms and e...DMPP （3,4-dimethylpyrazole phosphate） has been used to reduce nitrogen （N） loss from leaching or denitrification and to improve N supply in agricultural land. However, its impact on soil nitrifying organisms and enzyme activities involved in N cycling is largely unknown. Therefore, an on-farm experiment, for two years, has been conducted, to elucidate the effects of DMPP on mineral N （NH4^＋- N and NO3^--N） leaching, nitrifying organisms, and denitrifying enzymes in a rice-oilseed rape cropping system. Three treatments including urea alone （UA）, urea ＋ 1% DMPP （DP）, and no fertilizer （CK）, have been carded out. The results showed that DP enhanced the mean NH4^＋-N concentrations by 19.1%-24.3%, but reduced the mean NO3^--N concentrations by 44.9%-56.6% in the leachate, under a two-year rice-rape rotation, compared to the UA treatment. The population of ammonia oxidizing bacteria, the activity of nitrate reductase, and nitrite reductase in the DP treatment decreased about 24.5%-30.9%, 14.9%-43.5%, and 14.7%-31.6%, respectively, as compared to the UA treatment. However, nitrite oxidizing bacteria and hydroxylamine reductase remained almost unaffected by DMPP. It is proposed that DMPP has the potential to either reduce NO3^--N leaching by inhibiting ammonia oxidization or N losses from denitrification, which is in favor of the N conversations in the rice-oilseed rape cropping system.展开更多
An undisturbed heavy clay soil column experiment was conducted to examine the influence of the new nitrification inhibitor, 3,4- dimethylpyrazole phosphate （DMPP）, on nitrogen and soil salt-ion leaching. Regular ure...An undisturbed heavy clay soil column experiment was conducted to examine the influence of the new nitrification inhibitor, 3,4- dimethylpyrazole phosphate （DMPP）, on nitrogen and soil salt-ion leaching. Regular urea was selected as the nitrogen source in the soil. The results showed that the cumulative leaching losses of soil nitrate-N under the treatment of urea with DMPP were from 57.5% to 63.3% lower than those of the treatment of urea without DMPP. The use of nitrification inhibitors as nitrate leaching retardants may be a proposal in regulations to prevent groundwater contaminant. However, there were no great difference between urea and urea with DMPP treatments on ammonium-N leaching. Moreover, the soil salt-ion leaching losses of Ca^2＋, Mg^2＋, K^＋, and Na^＋ were reduced from 26.6% to 28.8%, 21.3% to 27.8%, 33.3% to 35.5%, and 21.7% to 32.1%, respectively. So, the leaching losses of soil salt-ion were declined for nitrification inhibitor DMPP addition, being beneficial to shallow groundwater protection and growth of crop. These results indicated the possibility of ammonium or ammonium producing compounds using nitrification inhibitor DMPP to control the nitrate and nutrient cation leaching losses, minimizing the risk of nitrate pollution in shallow groundwater.展开更多
The spatially controllable shape-shifting behaviors of a planar two-dimensional(2D)film to three-dimensional(3D)shapes upon external stimuli are of paramount significance for the development of smart materials.Herein,...The spatially controllable shape-shifting behaviors of a planar two-dimensional(2D)film to three-dimensional(3D)shapes upon external stimuli are of paramount significance for the development of smart materials.Herein,the present work focuses on fabricating plain film whose shape can be remotely and spatially transformed into various 3D configurations via the formation of a laser-induced temperature gradient;when subjected to laser irradiation,the prestretched hybrid films exhibit out-of-plane bending behavior owing to anisotropic chain relaxation and strain energy release.On this basis,various sophisticated shape transformations can be achieved by site-specific irradiations of laser with a controllable magnitude.Meanwhile,shape morphing involving reversible bending transformations can also be realized by employing the laser on the corresponding opposite side of the hybrid films.Remarkably,under a 160 mW/cm^(2) simulated sunlight illumination,the transformation of flat 2D film into 3D chiral actuators is driven by material anisotropy and geometrical heterogeneity of a bilayer strip design,and it yields right and left-handed helix,the morphologies of the helix shape can be precisely tailored by the strip angles and strain values.展开更多
文摘为了制备具有远程可控变形且性能优越的形状记忆聚合物,采用巯基-烯点击化学法制备了PCL/CB复合材料,并用FTIR、DSC、1 H NMR和DMA对复合材料的结构、热性能以及形状记忆特性等进行表征。结果表明:交联复合材料薄膜的热转变温度为50℃,且当预拉伸的复合材料薄膜受到100 mW/cm^(2)强度的激光照射时,CB颗粒吸收激光光子而产生光热转换且由于各向异性链松弛和应变能释放,致使上层薄膜在受到激光照射时,结晶熔融发生形状记忆效应而收缩,与此同时下层薄膜仍然处于玻璃态,上层薄膜的收缩力使PCL/CB复合材料薄膜朝着激光照射方向发生弯曲变形。同时,弯曲角度可以通过薄膜预拉伸应变量、激光照射时间以及薄膜厚度3个参数进行调控;当预拉伸应变为300%、薄膜厚度为0.4 mm时,最大弯曲角为164°。这种具备局部可编程行为的PCL/CB复合薄膜可为光响应SMP的变形模式提供新思路。
文摘DMPP （3,4-dimethylpyrazole phosphate） has been used to reduce nitrogen （N） loss from leaching or denitrification and to improve N supply in agricultural land. However, its impact on soil nitrifying organisms and enzyme activities involved in N cycling is largely unknown. Therefore, an on-farm experiment, for two years, has been conducted, to elucidate the effects of DMPP on mineral N （NH4^＋- N and NO3^--N） leaching, nitrifying organisms, and denitrifying enzymes in a rice-oilseed rape cropping system. Three treatments including urea alone （UA）, urea ＋ 1% DMPP （DP）, and no fertilizer （CK）, have been carded out. The results showed that DP enhanced the mean NH4^＋-N concentrations by 19.1%-24.3%, but reduced the mean NO3^--N concentrations by 44.9%-56.6% in the leachate, under a two-year rice-rape rotation, compared to the UA treatment. The population of ammonia oxidizing bacteria, the activity of nitrate reductase, and nitrite reductase in the DP treatment decreased about 24.5%-30.9%, 14.9%-43.5%, and 14.7%-31.6%, respectively, as compared to the UA treatment. However, nitrite oxidizing bacteria and hydroxylamine reductase remained almost unaffected by DMPP. It is proposed that DMPP has the potential to either reduce NO3^--N leaching by inhibiting ammonia oxidization or N losses from denitrification, which is in favor of the N conversations in the rice-oilseed rape cropping system.
文摘An undisturbed heavy clay soil column experiment was conducted to examine the influence of the new nitrification inhibitor, 3,4- dimethylpyrazole phosphate （DMPP）, on nitrogen and soil salt-ion leaching. Regular urea was selected as the nitrogen source in the soil. The results showed that the cumulative leaching losses of soil nitrate-N under the treatment of urea with DMPP were from 57.5% to 63.3% lower than those of the treatment of urea without DMPP. The use of nitrification inhibitors as nitrate leaching retardants may be a proposal in regulations to prevent groundwater contaminant. However, there were no great difference between urea and urea with DMPP treatments on ammonium-N leaching. Moreover, the soil salt-ion leaching losses of Ca^2＋, Mg^2＋, K^＋, and Na^＋ were reduced from 26.6% to 28.8%, 21.3% to 27.8%, 33.3% to 35.5%, and 21.7% to 32.1%, respectively. So, the leaching losses of soil salt-ion were declined for nitrification inhibitor DMPP addition, being beneficial to shallow groundwater protection and growth of crop. These results indicated the possibility of ammonium or ammonium producing compounds using nitrification inhibitor DMPP to control the nitrate and nutrient cation leaching losses, minimizing the risk of nitrate pollution in shallow groundwater.
基金supported by the National Natural Science Foundation of China (Grant No.22105152)。
文摘The spatially controllable shape-shifting behaviors of a planar two-dimensional(2D)film to three-dimensional(3D)shapes upon external stimuli are of paramount significance for the development of smart materials.Herein,the present work focuses on fabricating plain film whose shape can be remotely and spatially transformed into various 3D configurations via the formation of a laser-induced temperature gradient;when subjected to laser irradiation,the prestretched hybrid films exhibit out-of-plane bending behavior owing to anisotropic chain relaxation and strain energy release.On this basis,various sophisticated shape transformations can be achieved by site-specific irradiations of laser with a controllable magnitude.Meanwhile,shape morphing involving reversible bending transformations can also be realized by employing the laser on the corresponding opposite side of the hybrid films.Remarkably,under a 160 mW/cm^(2) simulated sunlight illumination,the transformation of flat 2D film into 3D chiral actuators is driven by material anisotropy and geometrical heterogeneity of a bilayer strip design,and it yields right and left-handed helix,the morphologies of the helix shape can be precisely tailored by the strip angles and strain values.
