The main objective of this research is to study the effect of fiber weight ratio and chemical fiber modification on flexural properties of composites reinforced with Posidonia fiber. An unsaturated polyester matrix re...The main objective of this research is to study the effect of fiber weight ratio and chemical fiber modification on flexural properties of composites reinforced with Posidonia fiber. An unsaturated polyester matrix reinforced with untreated and treated Posidonia fibers was fabricated under various fiber weight ratios. Results showed that the combined chemical treatment provided better mechanical properties of composites in comparison with untreated fiber. The fiber weight ratio influenced the flexural properties of composites. Indeed, a maximum value of flexural modulus was observed for 10% fiber weight ratio for composites reinforced with treated fibers. SEM photographs revealed a different fracture surface between Posidonia fibers reinforced polyester composites.展开更多
Morphology of hydraulic fracture surface has significant effects on oil and gas flow,proppant migration and fracture closure,which plays an important role in oil and gas fracturing stimulation.In this paper,we analyze...Morphology of hydraulic fracture surface has significant effects on oil and gas flow,proppant migration and fracture closure,which plays an important role in oil and gas fracturing stimulation.In this paper,we analyzed the fracture surface characteristics induced by supercritical carbon dioxide(SC-CO_(2))and water in open-hole and perforation completion conditions under triaxial stresses.A simple calculation method was proposed to quantitatively analyze the fracture surface area and roughness in macro-level based on three-dimensional(3D)scanning data.In micro-level,scanning electron micrograph(SEM)was used to analyze the features of fracture surface.The results showed that the surface area of the induced fracture increases with perforation angle for both SC-CO_(2)and water fracturing,and the surface area of SC-CO_(2)-induced fracture is 6.49%e58.57%larger than that of water-induced fracture.The fractal dimension and surface roughness of water-induced fractures increase with the increase in perforation angle,while those of SC-CO_(2)-induced fractures decrease with the increasing perforation angle.A considerable number of microcracks and particle peeling pits can be observed on SC-CO_(2)-induced fracture surface while there are more flat particle surfaces in water-induced fracture surface through SEM images,indicating that fractures tend to propagate along the boundary of the particle for SC-CO_(2)fracturing while water-induced fractures prefer to cut through particles.These findings are of great significance for analyzing fracture mechanism and evaluating fracturing stimulation performance.展开更多
The glass series<span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span s...The glass series<span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span style="font-family:;" "="">50P<sub>2</sub>O<sub>5</sub>-25CaO-(25</span></span><span style="white-space:normal;"><span style="font-family:;" "="">-</span></span><span style="white-space:normal;"><span style="font-family:;" "="">x)Na<sub>2</sub>O-xCoO (with (0 ≤ x ≤ 25;mol%)</span></span><span style="white-space:normal;"><span style="font-family:;" "="">, has been prepared by direct melting at 1080<span style="white-space:nowrap;">°</span>C</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span style="font-family:;" "="">±</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span style="font-family:;" "="">20<span style="white-space:nowrap;">°</span>C</span></span><span style="white-space:normal;"><span style="font-family:;" "="">. The introduction</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span style="font-family:;" "="">of cobalt in calcium phosphate glasses is use</span></span><span style="white-space:normal;"><span style="font-family:;" "="">d</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> to compare its</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span style="font-family:;" "="">effect with calcium in inhibition corrosion. The dissolution rate has been investigated. It indicated an improvement of chemical durability when the cobalt oxide increases in the network glass at the expense of Na<sub>2</sub>O content. Both, IR spectroscopy and X-ray diffraction have confirmed the structure changes when the CoO content increases in the glass. This change results in the disappearance of isolated orthophosphate groups follow</span></span><span style="white-space:normal;"><span style="font-family:;" "="">ed</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span style="font-family:;" "="">of a polymerizing of the structure from isolated orthophosphate towards pyrophosphate chains (Q<sup>1</sup>) by promoting the formation of olygophosphates</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span style="font-family:;" "="">(mixed</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span style="font-family:;" "="">Q<sup>1</sup>-Q<sup>2</sup>) </span></span><span style="white-space:normal;"><span style="font-family:;" "="">rich in pyrophosphates. Analysis of the density values, showed an increase of density with the increase CoO content. The covalent radius values of oxygen</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><i><span style="font-family:;" "="">r</span></i></span><span style="white-space:normal;"><sub><span style="font-family:;" "="">cal</span></sub></span><span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span style="font-family:;" "="">(O<sup>2-</sup>) indicate a significant decrease and therefore a relatively high reinforcement of the metal-oxygen-phosphorus (Co-O-P) bonds. SEM micrograph confirms the evolution of the glass structural morphology. The sample having a maximum CoO content confirms a homogeneous glass phase with quite crystalline particles.</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span style="font-family:;" "="">This property is prerequisite for many interesting industrial applications.</span></span>展开更多
Transparentγ-LiAlO2 single crystal has been grown by Temperature Gradient technique.The surface of the wafer annealed in O2-atmosphere at 1100°C for 70 h became opaque and Li-poor phase(LiAl5O8);while,that annea...Transparentγ-LiAlO2 single crystal has been grown by Temperature Gradient technique.The surface of the wafer annealed in O2-atmosphere at 1100°C for 70 h became opaque and Li-poor phase(LiAl5O8);while,that annealed in Li-rich atmosphere kept transparent and smooth.The full-width at half maximum value dropped to 30 arcsecs when the wafer was annealed in Li-rich atmosphere.That annealed in O2-atmosphere increased to 78 arcsec.Compared with absorption spectra,we can conclude that the 196 nm absorption peak was caused by Li vacancies and the 736 nm peak was caused by O vacancies.展开更多
An experimental procedure is conducted to investigate the mechanism of the non-monotonic characteristic between curing temperature and mechanical behaviors of the Kevlar/epoxy composite in macro and micro levels. Diff...An experimental procedure is conducted to investigate the mechanism of the non-monotonic characteristic between curing temperature and mechanical behaviors of the Kevlar/epoxy composite in macro and micro levels. Different specimens are fabricated at four different curing temperatures and tested with ±45° off-axis tensile loading on a universal test machine coupled with digital image correlation(DIC). Moreover, the environmental scanning electron microscope(SEM) was used to obtain the micrographs and reveal their mechanism. The tested results show that the tensile mechanical behaviors are sensitive to the curing temperature and the relationship is non-monotonic. Also, as the temperature increases, the thicknesses of the specimens are significantly enlarged. By analyzing the SEM micrographs of the matrix grooves in the damage zone and DIC strain contours, it is concluded that the non-monotonic relationship is dominated by the properties of the Kevlar/epoxy interfaces and deformation of the distorted fibers.展开更多
文摘The main objective of this research is to study the effect of fiber weight ratio and chemical fiber modification on flexural properties of composites reinforced with Posidonia fiber. An unsaturated polyester matrix reinforced with untreated and treated Posidonia fibers was fabricated under various fiber weight ratios. Results showed that the combined chemical treatment provided better mechanical properties of composites in comparison with untreated fiber. The fiber weight ratio influenced the flexural properties of composites. Indeed, a maximum value of flexural modulus was observed for 10% fiber weight ratio for composites reinforced with treated fibers. SEM photographs revealed a different fracture surface between Posidonia fibers reinforced polyester composites.
基金National Natural Science Foundation of China(Grant No.51804318)the China Postdoctoral Science Foundation Founded Project(Grant No.2019M650963)National Key Basic Research and Development Program of China(Grant No.2014CB239203).
文摘Morphology of hydraulic fracture surface has significant effects on oil and gas flow,proppant migration and fracture closure,which plays an important role in oil and gas fracturing stimulation.In this paper,we analyzed the fracture surface characteristics induced by supercritical carbon dioxide(SC-CO_(2))and water in open-hole and perforation completion conditions under triaxial stresses.A simple calculation method was proposed to quantitatively analyze the fracture surface area and roughness in macro-level based on three-dimensional(3D)scanning data.In micro-level,scanning electron micrograph(SEM)was used to analyze the features of fracture surface.The results showed that the surface area of the induced fracture increases with perforation angle for both SC-CO_(2)and water fracturing,and the surface area of SC-CO_(2)-induced fracture is 6.49%e58.57%larger than that of water-induced fracture.The fractal dimension and surface roughness of water-induced fractures increase with the increase in perforation angle,while those of SC-CO_(2)-induced fractures decrease with the increasing perforation angle.A considerable number of microcracks and particle peeling pits can be observed on SC-CO_(2)-induced fracture surface while there are more flat particle surfaces in water-induced fracture surface through SEM images,indicating that fractures tend to propagate along the boundary of the particle for SC-CO_(2)fracturing while water-induced fractures prefer to cut through particles.These findings are of great significance for analyzing fracture mechanism and evaluating fracturing stimulation performance.
文摘The glass series<span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span style="font-family:;" "="">50P<sub>2</sub>O<sub>5</sub>-25CaO-(25</span></span><span style="white-space:normal;"><span style="font-family:;" "="">-</span></span><span style="white-space:normal;"><span style="font-family:;" "="">x)Na<sub>2</sub>O-xCoO (with (0 ≤ x ≤ 25;mol%)</span></span><span style="white-space:normal;"><span style="font-family:;" "="">, has been prepared by direct melting at 1080<span style="white-space:nowrap;">°</span>C</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span style="font-family:;" "="">±</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span style="font-family:;" "="">20<span style="white-space:nowrap;">°</span>C</span></span><span style="white-space:normal;"><span style="font-family:;" "="">. The introduction</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span style="font-family:;" "="">of cobalt in calcium phosphate glasses is use</span></span><span style="white-space:normal;"><span style="font-family:;" "="">d</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> to compare its</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span style="font-family:;" "="">effect with calcium in inhibition corrosion. The dissolution rate has been investigated. It indicated an improvement of chemical durability when the cobalt oxide increases in the network glass at the expense of Na<sub>2</sub>O content. Both, IR spectroscopy and X-ray diffraction have confirmed the structure changes when the CoO content increases in the glass. This change results in the disappearance of isolated orthophosphate groups follow</span></span><span style="white-space:normal;"><span style="font-family:;" "="">ed</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span style="font-family:;" "="">of a polymerizing of the structure from isolated orthophosphate towards pyrophosphate chains (Q<sup>1</sup>) by promoting the formation of olygophosphates</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span style="font-family:;" "="">(mixed</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span style="font-family:;" "="">Q<sup>1</sup>-Q<sup>2</sup>) </span></span><span style="white-space:normal;"><span style="font-family:;" "="">rich in pyrophosphates. Analysis of the density values, showed an increase of density with the increase CoO content. The covalent radius values of oxygen</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><i><span style="font-family:;" "="">r</span></i></span><span style="white-space:normal;"><sub><span style="font-family:;" "="">cal</span></sub></span><span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span style="font-family:;" "="">(O<sup>2-</sup>) indicate a significant decrease and therefore a relatively high reinforcement of the metal-oxygen-phosphorus (Co-O-P) bonds. SEM micrograph confirms the evolution of the glass structural morphology. The sample having a maximum CoO content confirms a homogeneous glass phase with quite crystalline particles.</span></span><span style="white-space:normal;"><span style="font-family:;" "=""> </span></span><span style="white-space:normal;"><span style="font-family:;" "="">This property is prerequisite for many interesting industrial applications.</span></span>
基金supported by the program of Hundreds of Talents"of CASand the National 863"Project(Grant No.2004AA311080).
文摘Transparentγ-LiAlO2 single crystal has been grown by Temperature Gradient technique.The surface of the wafer annealed in O2-atmosphere at 1100°C for 70 h became opaque and Li-poor phase(LiAl5O8);while,that annealed in Li-rich atmosphere kept transparent and smooth.The full-width at half maximum value dropped to 30 arcsecs when the wafer was annealed in Li-rich atmosphere.That annealed in O2-atmosphere increased to 78 arcsec.Compared with absorption spectra,we can conclude that the 196 nm absorption peak was caused by Li vacancies and the 736 nm peak was caused by O vacancies.
基金supported by the National Natural Science Foundation of China(Grant Nos.11672105,11232004)Natural Science Foundation of Hunan Province(Grant No.2016JJ1009)
文摘An experimental procedure is conducted to investigate the mechanism of the non-monotonic characteristic between curing temperature and mechanical behaviors of the Kevlar/epoxy composite in macro and micro levels. Different specimens are fabricated at four different curing temperatures and tested with ±45° off-axis tensile loading on a universal test machine coupled with digital image correlation(DIC). Moreover, the environmental scanning electron microscope(SEM) was used to obtain the micrographs and reveal their mechanism. The tested results show that the tensile mechanical behaviors are sensitive to the curing temperature and the relationship is non-monotonic. Also, as the temperature increases, the thicknesses of the specimens are significantly enlarged. By analyzing the SEM micrographs of the matrix grooves in the damage zone and DIC strain contours, it is concluded that the non-monotonic relationship is dominated by the properties of the Kevlar/epoxy interfaces and deformation of the distorted fibers.
