为了解有机改性对碳酸钙颗粒在水介质中聚团的影响及其机理,进而为调控其聚团行为创造前提,以硬脂酸钠改性碳酸钙为对象,从改性影响碳酸钙表面自由能、影响颗粒聚团的热力学趋势和影响颗粒间相互作用能方面对改性碳酸钙颗粒在水介质中...为了解有机改性对碳酸钙颗粒在水介质中聚团的影响及其机理,进而为调控其聚团行为创造前提,以硬脂酸钠改性碳酸钙为对象,从改性影响碳酸钙表面自由能、影响颗粒聚团的热力学趋势和影响颗粒间相互作用能方面对改性碳酸钙颗粒在水介质中的聚团机理进行了研究。结果表明,碳酸钙经硬脂酸钠改性,导致碳酸钙颗粒聚团前后的能量变化由5.62 m J/m2增大至71.98 m J/m2,说明改性使碳酸钙颗粒在水介质中聚团趋势增大;另外,水介质中,改性碳酸钙作用能在颗粒间距大于6 nm范围为排斥性质,在约8 nm处出现能垒,在颗粒间距小于5 nm范围因疏水作用能为主导而呈强烈吸引性质。推断改性碳酸钙颗粒在外部能量作用下越过能垒,再通过疏水相互作用聚集是聚团的内在机制。展开更多
Population correlation function P(t) has been used to examine the mechanism of breakage and coalescence of clusters at steady-state under shear, the results are in qualitative a greement with exPeriments. The research...Population correlation function P(t) has been used to examine the mechanism of breakage and coalescence of clusters at steady-state under shear, the results are in qualitative a greement with exPeriments. The research indicates that with a weak potential the mechanism of breakage and coalescence of clusters at steady-state under shear is predomnately controlled by the paticle-particle model, but that with a strong potential the mechanism shifts to that of clustercluster for large clusters; for small clusters, however, the mechanism of particle-particle model seems still to remain predondnate, further work needs to be done.展开更多
To compare the development of physical crusts in three typical cultivated soils of China, a black soil （Luvic Phaeozem）, a loess soil （Haplic Luvisol）, and a purple soil （Calcaric Regosol） were packed in splash ...To compare the development of physical crusts in three typical cultivated soils of China, a black soil （Luvic Phaeozem）, a loess soil （Haplic Luvisol）, and a purple soil （Calcaric Regosol） were packed in splash plates with covered and uncovered treatments, and exposed to simulated rainfall. Meshes covered above the surfaces of half of soil samples to simulate the effects of crop residue on crusting. The results indicated a progressive breakdown of aggregates on the soil surface as rainfall continued. The bulk density and shear strength on the surface of the three soil types increased logarithmically as rainfall duration increased. During the first 30 min of simulated rainfall, the purple soil developed a 7-8 mm thick crust and the loess soil developed a 3-4 mm thick crust. The black soil developed a distinguishable, but still unstable, crust after 80 rain of simulated rainfall. Soil organic matter （SOM） content, the mean weight diameter （MWD） of soil aggregates, and soil clay content were negatively correlated with the rate of crust formation, whereas the percentage of aggregate dispersion （PAD）, the exchangeable sodium percentage （ESP）, and the silt and sand contents were positively correlated with crusting. Mechanical breakdown caused by raindrop impact was the primary mechanism of crust formation in the black soil with more stable aggregates （MWD 25.0 mm, PAD 3.1%） and higher SOM content （42.6 g kg-1）. Slaking and mechanical eluviation were the primary mechanisms of crust formation in the purple soil with low clay content （103 g kg-1）, cation exchange capacity （CEC, 228 mmol kg-1）, ESP （0.60%）, and SOM （17.2 g kg-1）. Mechanical breakdown and slaking were the most important in the loess soil with low CEC （80.6 mmol kg-1）, ESP （1.29%）, SOM （9.82 g kg-1）, and high PAD （71.7%） and MWD （4.6 mm）. Simulated residue cover reduced crust formation in black and loess soils, but increased crust formation in purple soil.展开更多
文摘为了解有机改性对碳酸钙颗粒在水介质中聚团的影响及其机理,进而为调控其聚团行为创造前提,以硬脂酸钠改性碳酸钙为对象,从改性影响碳酸钙表面自由能、影响颗粒聚团的热力学趋势和影响颗粒间相互作用能方面对改性碳酸钙颗粒在水介质中的聚团机理进行了研究。结果表明,碳酸钙经硬脂酸钠改性,导致碳酸钙颗粒聚团前后的能量变化由5.62 m J/m2增大至71.98 m J/m2,说明改性使碳酸钙颗粒在水介质中聚团趋势增大;另外,水介质中,改性碳酸钙作用能在颗粒间距大于6 nm范围为排斥性质,在约8 nm处出现能垒,在颗粒间距小于5 nm范围因疏水作用能为主导而呈强烈吸引性质。推断改性碳酸钙颗粒在外部能量作用下越过能垒,再通过疏水相互作用聚集是聚团的内在机制。
文摘Population correlation function P(t) has been used to examine the mechanism of breakage and coalescence of clusters at steady-state under shear, the results are in qualitative a greement with exPeriments. The research indicates that with a weak potential the mechanism of breakage and coalescence of clusters at steady-state under shear is predomnately controlled by the paticle-particle model, but that with a strong potential the mechanism shifts to that of clustercluster for large clusters; for small clusters, however, the mechanism of particle-particle model seems still to remain predondnate, further work needs to be done.
基金Supported by the National Natural Science Foundation of China (Nos. 41071192 and 40701096)the West Light Foundation of Chinese Academy of Sciences (No. B2008132)the Chinese Universities Scientific Fund (No. QN2009085)
文摘To compare the development of physical crusts in three typical cultivated soils of China, a black soil （Luvic Phaeozem）, a loess soil （Haplic Luvisol）, and a purple soil （Calcaric Regosol） were packed in splash plates with covered and uncovered treatments, and exposed to simulated rainfall. Meshes covered above the surfaces of half of soil samples to simulate the effects of crop residue on crusting. The results indicated a progressive breakdown of aggregates on the soil surface as rainfall continued. The bulk density and shear strength on the surface of the three soil types increased logarithmically as rainfall duration increased. During the first 30 min of simulated rainfall, the purple soil developed a 7-8 mm thick crust and the loess soil developed a 3-4 mm thick crust. The black soil developed a distinguishable, but still unstable, crust after 80 rain of simulated rainfall. Soil organic matter （SOM） content, the mean weight diameter （MWD） of soil aggregates, and soil clay content were negatively correlated with the rate of crust formation, whereas the percentage of aggregate dispersion （PAD）, the exchangeable sodium percentage （ESP）, and the silt and sand contents were positively correlated with crusting. Mechanical breakdown caused by raindrop impact was the primary mechanism of crust formation in the black soil with more stable aggregates （MWD 25.0 mm, PAD 3.1%） and higher SOM content （42.6 g kg-1）. Slaking and mechanical eluviation were the primary mechanisms of crust formation in the purple soil with low clay content （103 g kg-1）, cation exchange capacity （CEC, 228 mmol kg-1）, ESP （0.60%）, and SOM （17.2 g kg-1）. Mechanical breakdown and slaking were the most important in the loess soil with low CEC （80.6 mmol kg-1）, ESP （1.29%）, SOM （9.82 g kg-1）, and high PAD （71.7%） and MWD （4.6 mm）. Simulated residue cover reduced crust formation in black and loess soils, but increased crust formation in purple soil.
