The wettability of rocks affects the balance between capillary and viscous forces during multiphase flow through porous media,which in turn determines the fluid displacement process governing the recovery of oil from ...The wettability of rocks affects the balance between capillary and viscous forces during multiphase flow through porous media,which in turn determines the fluid displacement process governing the recovery of oil from subsurface formations.In this work,the mechanism of wettability reversal of aged synthetic sandstones by metal oxide nanoparticles(SiO_(2) and Al_(2)O_(3))was investigated with particular focus on the impact of surface roughness,zeta potential,and temperature.The synthetic surfaces were prepared from powders of Berea sandstone with known grain size ranges and their average roughness and roughness ratio were obtained from the 3D surface reconstruction of their microscope images.Each surface was subsequently aged in Permian crude oil to alter its wettability.For surfaces with larger grain sizes and lower surface roughness ratios,the lower capillary pressure allowed stronger oil/surface interactions,leading to enhanced oil-wetness.The wettability alteration effects of nanoparticles were then examined through real-time top view imaging and dynamic front view contact angle experiments.The negatively charged SiO_(2) nanoparticles rapidly reversed the sandstone wettability,indicating their potential applicability as wettability alteration agents.By contrast,the positively charged Al_(2)O_(3) counterpart caused no wettability reversal.The mechanism of wettability alteration was further studied by microscale interaction analyses and nanoscale transmission electron microscopy.Because nanoparticles were only a few nanometers large,the microscale roughness had a negligible effect on the wettability reversal.Instead,the combined effect of van der Waals dispersion forces and surface-charge-induced electrostatic forces were recognized as the two key factors affecting the wettability of sandstone particles.Such interactions may be curbed at elevated temperatures due to a decrease in the zeta potential and colloidal stability of the particles.展开更多
Background: The accuracy of the final prosthesis is affected by the final impression technique and master cast production. The aim of the present study was to evaluate the effect of the functional impression technique...Background: The accuracy of the final prosthesis is affected by the final impression technique and master cast production. The aim of the present study was to evaluate the effect of the functional impression technique with various impression materials on the surface characteristic of dental stone casts and their clinical effect on the retention of complete dentures. Method: Specimens of three impression materials/stone casts were fabricated. The specimens of the impression materials/stone casts were divided into three equal groups (I, II, and III). The impression materials used were as follows: tissue conditioner group (I), zinc oxide (ZEO) (group II) and poly (vinyl siloxane) (PVS) (group III). Cylindrical split aluminium moulds were designed to receive the impression materials and the stone mixture. The surface roughness of the stone cast specimens of the three groups (I, II, and III) was measured with a surface profilometer and analyzed by a scanning electron microscope. A clinical study included five severely resorbed mandibular edentulous alveolar ridges and edentulous maxillary arches. Each subject received three heat-cured acrylic resin dentures, fabricated using the functional impression technique. The three dentures were identical except for the different impression materials used from Groups I, II and III. The retentive force of each denture for each subject was measured. Result: The results of this study revealed that the mean value of surface roughness of the stone cast surface of group I was higher than group II and group III. A statistically significant difference was observed in surface roughness and the retentive dislodging force between the three studied groups. Although using a tissue conditioner as a functional impression material led to a high level of surface roughness and good retention, it could not produce the same smooth surface quality of PVS or ZEO. These data were supported by SEM analysis. The complete dentures for these patients require important oral and denture hygiene care. Conclusion: Complete dentures made using functional impression technique with PVC as a final impression material are more comfortable, retentive and stable.展开更多
Here we presented a novel technology to achieve a Super-hydrophobic coating with microscopic roughness on copper surface. First, make a layer of verdigris grow on the fresh pure copper surface. Gain it by exposing the...Here we presented a novel technology to achieve a Super-hydrophobic coating with microscopic roughness on copper surface. First, make a layer of verdigris grow on the fresh pure copper surface. Gain it by exposing the copper to air and the mist of acetic acid solution. The green coating is a mixture of basic copper（II） carbonate and copper（II） acetate. Second heat the coating and make it decompose to CuO. Lastly, form an n-octadecanethiol self-assembled monolayers coating on the outermost surface. Contact angle test, scanning electron microscope analysis and electrochemical testing were carded out to characterize the surface, and a heat transfer experiment for dropwise condensation of steam was performed also. Results show that the modified surface bears a few Super-hydrophobic features, the static contact angle is higher than that in literatures, reaching 153.1±1.7°. The microscopic roughness can be seen in SEM images, differing much from H2O2 etched surface and bare copper surface. The condensation of steam on the surface is a typical form of dropwise condensation, in the measured range of temperature difference, under 0.1 MPa, the average convection heat transfer coefficients of the vertical surface are 1.7-2.1 times for those of film condensation. At the same time, the inhibition efficiency of surface is improved to some extent comparing with the same kind of SAMs, which suggests that the lifetime of maintenance dropwise condensation would have the possibility to surpass the existing record.展开更多
目的采用原子力显微镜(AFM)检测常见口腔链球菌属与不同表面粗糙度的光固化复合树脂及玻璃离子水门汀(GIC)之间的黏附力。方法将光固化复合树脂和GIC样本表面梯度抛光,根据最终表面粗糙度不同分为300、200、100和10 nm组,使用AFM观察其...目的采用原子力显微镜(AFM)检测常见口腔链球菌属与不同表面粗糙度的光固化复合树脂及玻璃离子水门汀(GIC)之间的黏附力。方法将光固化复合树脂和GIC样本表面梯度抛光,根据最终表面粗糙度不同分为300、200、100和10 nm组,使用AFM观察其表面形貌。采用先锋菌(血链球菌、缓症链球菌)和致龋菌(变异链球菌、表兄链球菌)制作细菌改性探针,通过AFM获得力—距曲线测量细菌与树脂和GIC样本表面的黏附力。对材料表面粗糙度测量值进行方差分析,细菌黏附力进行Kruskal-Wallis非参数检验,同时采用Dunn’s进行组间两两比较,并对表面粗糙度与细菌黏附力进行相关性分析。结果随材料表面粗糙度增加,细菌的黏附力增大,4种细菌的黏附力均在300 nm的材料表面达到最大值;在10和300 nm组的GIC表面,变异链球菌的黏附力由0.578 n N增加到2.876 n N。4种细菌在树脂表面的黏附力略大于GIC,先锋菌的黏附力略大于致龋菌,组间差异均在200和300 nm组时较明显。结论材料表面粗糙度对细菌黏附力的影响较大,二者有明显的相关性;GIC对细菌的黏附性较复合树脂低;材料表面粗糙度对致龋菌的影响小于先锋菌。展开更多
原子力显微镜(Atomic Force Microscope,AFM)是纳米科技研究领域的一种重要工具。作为一种近场成像仪器,参数的选择对样品成像的效果有着很大的影响,不当的参数甚至可能造成样品的损坏。通过采用控制变量法,并以均方根粗糙度作为评判标...原子力显微镜(Atomic Force Microscope,AFM)是纳米科技研究领域的一种重要工具。作为一种近场成像仪器,参数的选择对样品成像的效果有着很大的影响,不当的参数甚至可能造成样品的损坏。通过采用控制变量法,并以均方根粗糙度作为评判标准,改变AFM各项扫描参数,研究了AFM中不同参数的调整对于样品扫描图像的影响。结果表明,振幅阈值、扫描速率、积分增益三项参数对于测量样品表面粗糙度均有较大影响,通过适当改变扫描参数,可以有效提升AFM的样品扫描质量。展开更多
基金the financial support from Baker Hughes Company and the U.S.National Science Foundation(NSF CAREER Award 1351296).
文摘The wettability of rocks affects the balance between capillary and viscous forces during multiphase flow through porous media,which in turn determines the fluid displacement process governing the recovery of oil from subsurface formations.In this work,the mechanism of wettability reversal of aged synthetic sandstones by metal oxide nanoparticles(SiO_(2) and Al_(2)O_(3))was investigated with particular focus on the impact of surface roughness,zeta potential,and temperature.The synthetic surfaces were prepared from powders of Berea sandstone with known grain size ranges and their average roughness and roughness ratio were obtained from the 3D surface reconstruction of their microscope images.Each surface was subsequently aged in Permian crude oil to alter its wettability.For surfaces with larger grain sizes and lower surface roughness ratios,the lower capillary pressure allowed stronger oil/surface interactions,leading to enhanced oil-wetness.The wettability alteration effects of nanoparticles were then examined through real-time top view imaging and dynamic front view contact angle experiments.The negatively charged SiO_(2) nanoparticles rapidly reversed the sandstone wettability,indicating their potential applicability as wettability alteration agents.By contrast,the positively charged Al_(2)O_(3) counterpart caused no wettability reversal.The mechanism of wettability alteration was further studied by microscale interaction analyses and nanoscale transmission electron microscopy.Because nanoparticles were only a few nanometers large,the microscale roughness had a negligible effect on the wettability reversal.Instead,the combined effect of van der Waals dispersion forces and surface-charge-induced electrostatic forces were recognized as the two key factors affecting the wettability of sandstone particles.Such interactions may be curbed at elevated temperatures due to a decrease in the zeta potential and colloidal stability of the particles.
文摘Background: The accuracy of the final prosthesis is affected by the final impression technique and master cast production. The aim of the present study was to evaluate the effect of the functional impression technique with various impression materials on the surface characteristic of dental stone casts and their clinical effect on the retention of complete dentures. Method: Specimens of three impression materials/stone casts were fabricated. The specimens of the impression materials/stone casts were divided into three equal groups (I, II, and III). The impression materials used were as follows: tissue conditioner group (I), zinc oxide (ZEO) (group II) and poly (vinyl siloxane) (PVS) (group III). Cylindrical split aluminium moulds were designed to receive the impression materials and the stone mixture. The surface roughness of the stone cast specimens of the three groups (I, II, and III) was measured with a surface profilometer and analyzed by a scanning electron microscope. A clinical study included five severely resorbed mandibular edentulous alveolar ridges and edentulous maxillary arches. Each subject received three heat-cured acrylic resin dentures, fabricated using the functional impression technique. The three dentures were identical except for the different impression materials used from Groups I, II and III. The retentive force of each denture for each subject was measured. Result: The results of this study revealed that the mean value of surface roughness of the stone cast surface of group I was higher than group II and group III. A statistically significant difference was observed in surface roughness and the retentive dislodging force between the three studied groups. Although using a tissue conditioner as a functional impression material led to a high level of surface roughness and good retention, it could not produce the same smooth surface quality of PVS or ZEO. These data were supported by SEM analysis. The complete dentures for these patients require important oral and denture hygiene care. Conclusion: Complete dentures made using functional impression technique with PVC as a final impression material are more comfortable, retentive and stable.
基金supports of the National Natural Seience Foundation of China (Grant No.50706053)the National High Teelmology Research and Development Program of China(863 Prograrn,Grant No.2007AA052259) are gratefully acknowledged.
文摘Here we presented a novel technology to achieve a Super-hydrophobic coating with microscopic roughness on copper surface. First, make a layer of verdigris grow on the fresh pure copper surface. Gain it by exposing the copper to air and the mist of acetic acid solution. The green coating is a mixture of basic copper（II） carbonate and copper（II） acetate. Second heat the coating and make it decompose to CuO. Lastly, form an n-octadecanethiol self-assembled monolayers coating on the outermost surface. Contact angle test, scanning electron microscope analysis and electrochemical testing were carded out to characterize the surface, and a heat transfer experiment for dropwise condensation of steam was performed also. Results show that the modified surface bears a few Super-hydrophobic features, the static contact angle is higher than that in literatures, reaching 153.1±1.7°. The microscopic roughness can be seen in SEM images, differing much from H2O2 etched surface and bare copper surface. The condensation of steam on the surface is a typical form of dropwise condensation, in the measured range of temperature difference, under 0.1 MPa, the average convection heat transfer coefficients of the vertical surface are 1.7-2.1 times for those of film condensation. At the same time, the inhibition efficiency of surface is improved to some extent comparing with the same kind of SAMs, which suggests that the lifetime of maintenance dropwise condensation would have the possibility to surpass the existing record.
文摘目的采用原子力显微镜(AFM)检测常见口腔链球菌属与不同表面粗糙度的光固化复合树脂及玻璃离子水门汀(GIC)之间的黏附力。方法将光固化复合树脂和GIC样本表面梯度抛光,根据最终表面粗糙度不同分为300、200、100和10 nm组,使用AFM观察其表面形貌。采用先锋菌(血链球菌、缓症链球菌)和致龋菌(变异链球菌、表兄链球菌)制作细菌改性探针,通过AFM获得力—距曲线测量细菌与树脂和GIC样本表面的黏附力。对材料表面粗糙度测量值进行方差分析,细菌黏附力进行Kruskal-Wallis非参数检验,同时采用Dunn’s进行组间两两比较,并对表面粗糙度与细菌黏附力进行相关性分析。结果随材料表面粗糙度增加,细菌的黏附力增大,4种细菌的黏附力均在300 nm的材料表面达到最大值;在10和300 nm组的GIC表面,变异链球菌的黏附力由0.578 n N增加到2.876 n N。4种细菌在树脂表面的黏附力略大于GIC,先锋菌的黏附力略大于致龋菌,组间差异均在200和300 nm组时较明显。结论材料表面粗糙度对细菌黏附力的影响较大,二者有明显的相关性;GIC对细菌的黏附性较复合树脂低;材料表面粗糙度对致龋菌的影响小于先锋菌。
文摘原子力显微镜(Atomic Force Microscope,AFM)是纳米科技研究领域的一种重要工具。作为一种近场成像仪器,参数的选择对样品成像的效果有着很大的影响,不当的参数甚至可能造成样品的损坏。通过采用控制变量法,并以均方根粗糙度作为评判标准,改变AFM各项扫描参数,研究了AFM中不同参数的调整对于样品扫描图像的影响。结果表明,振幅阈值、扫描速率、积分增益三项参数对于测量样品表面粗糙度均有较大影响,通过适当改变扫描参数,可以有效提升AFM的样品扫描质量。
