This paper is to study the influence of composition, microstructure and pore characteristics on the rock mechanical properties. Five kinds of sandstone compositions were analyzed by using X-ray diffraction instrument....This paper is to study the influence of composition, microstructure and pore characteristics on the rock mechanical properties. Five kinds of sandstone compositions were analyzed by using X-ray diffraction instrument. And the microstructure was observed by using scanning electron microscope. Then the pore distribution characteristic was investigated by using the low field nuclear magnetic resonance equipment. Finally, the uniaxial compression test was carried out to investigate the mechanical characteristics by using RMT150C mechanics experimental system and the uniaxial compressive strength, Poisson's ratio and elastic modulus were obtained. Compared to the analysis of the composition, structure and pore distribution and mechanical properties of the five kinds of sandstones, the relationship among composition,structure, pore distribution and mechanical properties was obtained. The results show that the composition, microstructure, pore distribution and mechanical properties of sandstone are closely related.With the decrease of feldspar and quartz particles, the compressive strength and elastic modulus increase, while the porosity decreases.展开更多
Electrochemical measurement, optical microscopy, and scanning electron microscopy were employed to investigate the corrosion behavior of some low alloy steels. The steels were held under a thin liquid film of 0.5wt% N...Electrochemical measurement, optical microscopy, and scanning electron microscopy were employed to investigate the corrosion behavior of some low alloy steels. The steels were held under a thin liquid film of 0.5wt% NaCl aqueous solution. It is found that the steels with the same chemical composition but different micmstructures exhibit obviously different corrosion behaviors. However, the corrosion behavior of the steels with different compositions but the same microstructnres may be similar in the present investigation. The corrosion rate of bainite is slower than that of ferrite and pearlite. The corrosion products of bainite are uniform and fine. The size of carbon-rich phases produces a great impact on the corrosion of the steels, whether in the initial stage or in the long tenn. It is easy to induce large pitting for carbon-rich phases with large size, which damages the compactness of the rust layer.展开更多
Wood anatomical structures of various tree species help identify the wood. The characteristics and composition of these structures affect their utilisation. In this work, the microstructure of Blighia sapida a lesser-...Wood anatomical structures of various tree species help identify the wood. The characteristics and composition of these structures affect their utilisation. In this work, the microstructure of Blighia sapida a lesser-known Ghanaian hardwood species using light microscope and scanning electron microscope (SEM) was studied. The relationship between the microstructure and some physical properties such as density, and bending strength were also studied. The anatomical features studied were fibre length, double fibre wall thickness, fibre proportion, vessel diameter and proportion, rays and axial parenchyma proportions. It was observed that the use of SEM in studying the anatomical or ultra-structural aspects of wood gives a clearer understanding of the features and structures found in wood. Anatomical features such as presence of crystals and absence of axial parenchyma in Blighia sapida are reported in the work. The study also established that Blighia sapida had a low water uptake even though it had vessel distribution of 12 vessels/mm<sup>2</sup>. Having not very distinct axial parenchyma may have accounted for the low water uptake. The presence of occluded pits could also account for the low water uptake and the fibre wall thickness may also account for a medium bending strength of 62.8 N/mm<sup>2</sup> at 12% moisture content.展开更多
Coir fiber is derived from the coconut shells and considered to be an economical and natural material. In order to further extend its application fields,the geometry and microstructure of the coir fiber were thoroughl...Coir fiber is derived from the coconut shells and considered to be an economical and natural material. In order to further extend its application fields,the geometry and microstructure of the coir fiber were thoroughly investigated in this research. The single fiber length measurement was carried out,and it was revealed that the length of the coir fiber was between 8 and 337 mm. Length distribution of the coir fiber was simulated by using the computer technology,and was found to be in coincidence with that of most natural fibers. The grouping measurement analysis was used to study the length-weight distribution and length-linear density distribution of the fiber. It was found that the average linear density was 27.89 tex and the linear density was between 18.265 and 70.442 tex. The length-weight distribution of the coir fiber showed a Poisson pattern,and the weight of fibers with the length between 50 and 230 mm accounted for 85.28% of the total fibers measured. In this research,scanning electron microscope (SEM) was applied to observe the morphological changes of coir fiber before and after alkali treatment;and the result shows that alkali treatment leads to the removal of lignin and pectin from both the cuticle and the inside walls,which is beneficial for the interfacial adhesion with polymer matrix in composite fabrication.展开更多
This paper examines the effect of the microstructure and electrical conductivity(EC)on the swelling ratio and pressure in red-bed mudstone sampled from arid areas in the Xining region in the northeastern Tibetan Plate...This paper examines the effect of the microstructure and electrical conductivity(EC)on the swelling ratio and pressure in red-bed mudstone sampled from arid areas in the Xining region in the northeastern Tibetan Plateau.A series of laboratory tests,including swelling experiments,X-ray diffraction(XRD),and scanning electron microscope(SEM),was carried out for mechanical and microstructural analysis.The coupled influence of the EC and microstructural parameters on the expansion ratio and pressure was investigated,and the weight coefficients were discussed by the entropy weight method.The results revealed an increasing exponential trend in EC,and the maximum swelling speed occurred at an EC of approximately 10 mS/cm.In addition,a method for predicting the expansion potential is proposed based on the microstructure,and its reliability is verified by comparing with swelling experimental results.In addition,according to the image analysis results,the ranges of the change in the clay minerals content(CMC),the fractal dimension(FD),the average diameter(AD)of pores,and the plane porosity(PP)are 23.75%e53%,1.08e1.17,7.53e22.45 mm,and 0.62%e1.25%,respectively.Moreover,mudstone swelling is negatively correlated with the plane porosity,fractal dimension and average diameter and is linearly correlated with the clay mineral content.Furthermore,the weight values prove that the microstructural characteristics,including FD,AD,and PP,are the main factors influencing the expansion properties of red-bed mudstones in the Xining region.Based on the combination of macro and micro-analyses,a quantitative analysis of the swelling process of mudstones can provide a better reference for understanding the mechanism of expansion behavior.展开更多
The microstructure of Fe-Ni metallic phases in Dong Ujimqin mesosiderite was studied using the field emission SEM. Taenite is characterized by a zoned structure, consisting of outer clear taenite and inner cloudy zone...The microstructure of Fe-Ni metallic phases in Dong Ujimqin mesosiderite was studied using the field emission SEM. Taenite is characterized by a zoned structure, consisting of outer clear taenite and inner cloudy zone (CZ). CZ has a typical 'island-honeycomb' microstructure. The average size of the island phase is about 358 nm, suggesting a cooling rate of~0.5℃/Ma at low temperature (【400℃). The Ni concentration profiles across kamacite and zoned taenite were also measured by electron probe microscope analysis (EPMA). Formation of the Fe-Ni metallic phases, microstructure in Dong Ujimqin mesosiderite was discussed based on the new low-temperature Fe-Ni phase diagram.展开更多
Loess soils are characterized by metastable microstructure, high porosity and water-sensitivity. These soils have always been problematic soils and attracted attention from researchers all over the world. In the prese...Loess soils are characterized by metastable microstructure, high porosity and water-sensitivity. These soils have always been problematic soils and attracted attention from researchers all over the world. In the present study, three loess soils extracted at various depths from the Loess Plateau of China, i.e. Malan(Q_3), upper Lishi(Q_2~2) and lower Lishi(Q_2~1) loess soils, were studied. Single oedometer-collapse tests were performed on intact loess specimens to investigate the collapse behavior of three loess soils. The microstructure and chemical composition of each loess before and after collapse test were characterized using scanning electron microscopy(i.e. SEM) and energy dispersive spectroscopy(i.e. EDS) techniques. The microstructural evolution due to wetting collapse was interpreted qualitatively and quantitatively in terms of the pore morphology properties. The results suggest that:(1) the collapse potential of each loess may rise again after a round of rise and drop, which could be failure of the new-developed stable structure under quite high vertical pressure. It implies that loess may collapse even if it has collapsed.(2) Q_3, Q_2~2 and Q_2~1 loess have different types of microstructure, namely, granule, aggregate and matrix type of microstructure, respectively.(3) The microstructural evolution due to loading and wetting is observed from a granule type to an aggregate type and finally to a matrix type of structure. The variations in distributions of pore morphology properties indicate that collapse leads to a transformation of large-sized pores into small-sized pores, re-orientation and remolding of soil pores due to particle rearrangement.(4) A porous structure is essential for loess collapse; however, the non-water-stability of bonding agents promotes the occurrence of collapse under the coupling effect of loading and wetting.展开更多
The coarse pore system, interfacial transition zone (ITZ) between aggregate and paste matrix and volume fraction of unhydrated cement in concrete (w/c=0.3) containing mineral admixtures were quantitatively charact...The coarse pore system, interfacial transition zone (ITZ) between aggregate and paste matrix and volume fraction of unhydrated cement in concrete (w/c=0.3) containing mineral admixtures were quantitatively characterized by the scanning electron microscope-backscattered electron (SEM-BSE) image analysis technique. The experimental results show that compound addition of slag and fly ash decreases the coarse porosity from 10.17% to 3.74% and the threshold diameter of coarse pore size from 345 μm to 105 μm compared with concrete (w/c=0.30) without mineral admixtures; Moreover with compound addition of fly ash and slag, the volume proportion of unhydrated cement in paste matrix is reduced by 30%, the maximum amount of coarse pores in the ITZ between aggregate and paste decreases from 13.11% to 5.57% and the thickness of ITZ is reduced by 37% , compared with concrete without mineral admixtures.展开更多
基金provided by the National Natural Science Foundation of China (No. U1261207)
文摘This paper is to study the influence of composition, microstructure and pore characteristics on the rock mechanical properties. Five kinds of sandstone compositions were analyzed by using X-ray diffraction instrument. And the microstructure was observed by using scanning electron microscope. Then the pore distribution characteristic was investigated by using the low field nuclear magnetic resonance equipment. Finally, the uniaxial compression test was carried out to investigate the mechanical characteristics by using RMT150C mechanics experimental system and the uniaxial compressive strength, Poisson's ratio and elastic modulus were obtained. Compared to the analysis of the composition, structure and pore distribution and mechanical properties of the five kinds of sandstones, the relationship among composition,structure, pore distribution and mechanical properties was obtained. The results show that the composition, microstructure, pore distribution and mechanical properties of sandstone are closely related.With the decrease of feldspar and quartz particles, the compressive strength and elastic modulus increase, while the porosity decreases.
基金supported by the Major State Basic Research and Development Program of China (No.2004CB619102)
文摘Electrochemical measurement, optical microscopy, and scanning electron microscopy were employed to investigate the corrosion behavior of some low alloy steels. The steels were held under a thin liquid film of 0.5wt% NaCl aqueous solution. It is found that the steels with the same chemical composition but different micmstructures exhibit obviously different corrosion behaviors. However, the corrosion behavior of the steels with different compositions but the same microstructnres may be similar in the present investigation. The corrosion rate of bainite is slower than that of ferrite and pearlite. The corrosion products of bainite are uniform and fine. The size of carbon-rich phases produces a great impact on the corrosion of the steels, whether in the initial stage or in the long tenn. It is easy to induce large pitting for carbon-rich phases with large size, which damages the compactness of the rust layer.
文摘Wood anatomical structures of various tree species help identify the wood. The characteristics and composition of these structures affect their utilisation. In this work, the microstructure of Blighia sapida a lesser-known Ghanaian hardwood species using light microscope and scanning electron microscope (SEM) was studied. The relationship between the microstructure and some physical properties such as density, and bending strength were also studied. The anatomical features studied were fibre length, double fibre wall thickness, fibre proportion, vessel diameter and proportion, rays and axial parenchyma proportions. It was observed that the use of SEM in studying the anatomical or ultra-structural aspects of wood gives a clearer understanding of the features and structures found in wood. Anatomical features such as presence of crystals and absence of axial parenchyma in Blighia sapida are reported in the work. The study also established that Blighia sapida had a low water uptake even though it had vessel distribution of 12 vessels/mm<sup>2</sup>. Having not very distinct axial parenchyma may have accounted for the low water uptake. The presence of occluded pits could also account for the low water uptake and the fibre wall thickness may also account for a medium bending strength of 62.8 N/mm<sup>2</sup> at 12% moisture content.
基金Tianjin Universities Science and Technology Development Fund Project ,China (No.20041401)
文摘Coir fiber is derived from the coconut shells and considered to be an economical and natural material. In order to further extend its application fields,the geometry and microstructure of the coir fiber were thoroughly investigated in this research. The single fiber length measurement was carried out,and it was revealed that the length of the coir fiber was between 8 and 337 mm. Length distribution of the coir fiber was simulated by using the computer technology,and was found to be in coincidence with that of most natural fibers. The grouping measurement analysis was used to study the length-weight distribution and length-linear density distribution of the fiber. It was found that the average linear density was 27.89 tex and the linear density was between 18.265 and 70.442 tex. The length-weight distribution of the coir fiber showed a Poisson pattern,and the weight of fibers with the length between 50 and 230 mm accounted for 85.28% of the total fibers measured. In this research,scanning electron microscope (SEM) was applied to observe the morphological changes of coir fiber before and after alkali treatment;and the result shows that alkali treatment leads to the removal of lignin and pectin from both the cuticle and the inside walls,which is beneficial for the interfacial adhesion with polymer matrix in composite fabrication.
基金the funding support from National Natural Science Foundation of China(Grant No.42077271)Sichuan Science and Technology Program,China(Grant No.2023YFS0364)Chengdu Science and Technology Program(Grant No.2022-YF05-00340-SN).
文摘This paper examines the effect of the microstructure and electrical conductivity(EC)on the swelling ratio and pressure in red-bed mudstone sampled from arid areas in the Xining region in the northeastern Tibetan Plateau.A series of laboratory tests,including swelling experiments,X-ray diffraction(XRD),and scanning electron microscope(SEM),was carried out for mechanical and microstructural analysis.The coupled influence of the EC and microstructural parameters on the expansion ratio and pressure was investigated,and the weight coefficients were discussed by the entropy weight method.The results revealed an increasing exponential trend in EC,and the maximum swelling speed occurred at an EC of approximately 10 mS/cm.In addition,a method for predicting the expansion potential is proposed based on the microstructure,and its reliability is verified by comparing with swelling experimental results.In addition,according to the image analysis results,the ranges of the change in the clay minerals content(CMC),the fractal dimension(FD),the average diameter(AD)of pores,and the plane porosity(PP)are 23.75%e53%,1.08e1.17,7.53e22.45 mm,and 0.62%e1.25%,respectively.Moreover,mudstone swelling is negatively correlated with the plane porosity,fractal dimension and average diameter and is linearly correlated with the clay mineral content.Furthermore,the weight values prove that the microstructural characteristics,including FD,AD,and PP,are the main factors influencing the expansion properties of red-bed mudstones in the Xining region.Based on the combination of macro and micro-analyses,a quantitative analysis of the swelling process of mudstones can provide a better reference for understanding the mechanism of expansion behavior.
文摘The microstructure of Fe-Ni metallic phases in Dong Ujimqin mesosiderite was studied using the field emission SEM. Taenite is characterized by a zoned structure, consisting of outer clear taenite and inner cloudy zone (CZ). CZ has a typical 'island-honeycomb' microstructure. The average size of the island phase is about 358 nm, suggesting a cooling rate of~0.5℃/Ma at low temperature (【400℃). The Ni concentration profiles across kamacite and zoned taenite were also measured by electron probe microscope analysis (EPMA). Formation of the Fe-Ni metallic phases, microstructure in Dong Ujimqin mesosiderite was discussed based on the new low-temperature Fe-Ni phase diagram.
基金the National Key Research and Development Program of China (2017YFD0800501)the National Natural Science Foundation of China (Grant No. 41772323)+2 种基金the Shaanxi Science and Technology Bureau (Grant No.2016KW-030)the Geological Survey Bureau of China (DD20189270)the Key Laboratory for Geohazard in Loess Area, Ministry of Land and Resources (Grant No. KLGLAMLR201502)
文摘Loess soils are characterized by metastable microstructure, high porosity and water-sensitivity. These soils have always been problematic soils and attracted attention from researchers all over the world. In the present study, three loess soils extracted at various depths from the Loess Plateau of China, i.e. Malan(Q_3), upper Lishi(Q_2~2) and lower Lishi(Q_2~1) loess soils, were studied. Single oedometer-collapse tests were performed on intact loess specimens to investigate the collapse behavior of three loess soils. The microstructure and chemical composition of each loess before and after collapse test were characterized using scanning electron microscopy(i.e. SEM) and energy dispersive spectroscopy(i.e. EDS) techniques. The microstructural evolution due to wetting collapse was interpreted qualitatively and quantitatively in terms of the pore morphology properties. The results suggest that:(1) the collapse potential of each loess may rise again after a round of rise and drop, which could be failure of the new-developed stable structure under quite high vertical pressure. It implies that loess may collapse even if it has collapsed.(2) Q_3, Q_2~2 and Q_2~1 loess have different types of microstructure, namely, granule, aggregate and matrix type of microstructure, respectively.(3) The microstructural evolution due to loading and wetting is observed from a granule type to an aggregate type and finally to a matrix type of structure. The variations in distributions of pore morphology properties indicate that collapse leads to a transformation of large-sized pores into small-sized pores, re-orientation and remolding of soil pores due to particle rearrangement.(4) A porous structure is essential for loess collapse; however, the non-water-stability of bonding agents promotes the occurrence of collapse under the coupling effect of loading and wetting.
文摘The coarse pore system, interfacial transition zone (ITZ) between aggregate and paste matrix and volume fraction of unhydrated cement in concrete (w/c=0.3) containing mineral admixtures were quantitatively characterized by the scanning electron microscope-backscattered electron (SEM-BSE) image analysis technique. The experimental results show that compound addition of slag and fly ash decreases the coarse porosity from 10.17% to 3.74% and the threshold diameter of coarse pore size from 345 μm to 105 μm compared with concrete (w/c=0.30) without mineral admixtures; Moreover with compound addition of fly ash and slag, the volume proportion of unhydrated cement in paste matrix is reduced by 30%, the maximum amount of coarse pores in the ITZ between aggregate and paste decreases from 13.11% to 5.57% and the thickness of ITZ is reduced by 37% , compared with concrete without mineral admixtures.