Development of microstructure of early cement paste (0–6 h) was investigated with 1H low-field NMR. It was found that T 2 (transverse relaxation time) distributions of fresh cement paste were bimodal and two peaks we...Development of microstructure of early cement paste (0–6 h) was investigated with 1H low-field NMR. It was found that T 2 (transverse relaxation time) distributions of fresh cement paste were bimodal and two peaks were ‘long component’ and ‘short component’. Separation degree of two peaks was a sign of exchange of water within flocculation and outside flocculation. Factors such as water cement ratio, specific surface area and dosage of superplasticizer had influences on the separation degree: the separation degree increased with the water cement ratio; the separation degree of cement paste prepared with cement with a high specific surface area was zero; dosage of superplasticizer will decrease separation degree. Results also suggested that T 2 distribution gradually moved to the left and T 2 of long component and initial fluidity were linearly correlated.展开更多
Organic ionic plastic crystals(OIPCs)are emerging as an important material family for solid-state electrolytes and many other applications.They have significant advantages over conventional electrolyte materials,such ...Organic ionic plastic crystals(OIPCs)are emerging as an important material family for solid-state electrolytes and many other applications.They have significant advantages over conventional electrolyte materials,such as high ionic conductivity,non-flammability,and plasticity.Various nuclear magnetic resonance(NMR)spectroscopy techniques including solid-state NMR,pulsed-field gradient(PFG)NMR,and magnetic resonance imaging(MRI)etc.,provide us a versatile toolkit to understand the fundamental level structures,molecular dynamics,and ionic interactions in these materials.This article reviews the commonly used NMR methods including solid-and solution-state NMR,PFG-NMR,dynamic nuclear polarization(DNP)and the application of these methods in revealing the microscopic level structures and ion-transport mechanisms in OIPC materials.展开更多
We built a three-dimensional irregular network model which can adequately describe reservoir rock pore-throat structures. We carried out numerical simulations to study the NMR T2 distribution of water-saturated rocks....We built a three-dimensional irregular network model which can adequately describe reservoir rock pore-throat structures. We carried out numerical simulations to study the NMR T2 distribution of water-saturated rocks. The results indicate that there is a good correlation between T2 distribution and the pore radius frequency histogram. The total T2 distribution can be partitioned into pore body and pore throat parts. The effect of parameters including throat radius, pore-throat ratio, and coordination number of the micro- pore structure on the T2 distribution can be evaluated individually. The result indicates that： 1 ） with the increase of the pore throat radius, the T2 distribution moves toward longer relaxation times and its peak intensity increases; 2） with the increase of the pore-throat ratio, the T2 distribution moves towards longer T2 with the peak intensity increasing and the overlap between pore body T2 and pore throat T2 decreasing; 3） With the increase of connectivity, the short T2 component increases and peak signal intensity decreases slightly.展开更多
The composition and the microstructures of isoprene-methyl methacrylate copolymers havebeen quantitatively studied by 250 MHz 1H-NMR spectra. Applying two lanthanide shiftreagents, by examining the separation of reson...The composition and the microstructures of isoprene-methyl methacrylate copolymers havebeen quantitatively studied by 250 MHz 1H-NMR spectra. Applying two lanthanide shiftreagents, by examining the separation of resonance peaks of the 1,4-isoprene olefin proton,I-centred triad distributions, and even I-cectred pentad fractions are measured. It is con-firmed that there is a penultimate of effect in this free radical copolymerization and the reac-tivity ratios established corresponding to Second-order Markov chain model are r11=0.48,rMI=0.86, rMM=0.51 and rIM=0.43, respectively. The observed I-centred pentad fraetions andM-centred triad distributions agree with the above results.展开更多
Permeability is a major indicator of concrete durability,and depends primarily on the microstructure characteristics of concrete,including its porosity and pore size distribution.In this study,a variety of concrete sa...Permeability is a major indicator of concrete durability,and depends primarily on the microstructure characteristics of concrete,including its porosity and pore size distribution.In this study,a variety of concrete samples were prepared to investigate their microstructure characteristics via nuclear magnetic resonance(NMR),mercury intrusion porosimetry(MIP),and X-ray computed tomography(X-CT).Furthermore,the chloride diffusion coefficient of concrete was measured to explore its correlation with the microstructure of the concrete samples.Results show that the proportion of pores with diameters<1000 nm obtained by NMR exceeds that obtained by MIP,although the difference in the total porosity determined by both methods is minimal.X-CT measurements obtained a relatively small porosity;however,this likely reflcts the distribution of large pores more accurately.A strong correlation is observed between the chloride diffusion coefficient and the porosity or contributive porosity of pores with sizes<1000 nm.Moreover,microstructure parameters measured via NMR reveal a lower correlation coefficient R2 versus the chloride diffusion coefficient relative to the parameters determined via MIP,as NMR can measure non-connected as well as connected pores.In addition,when analyzing pores with sizes>50 um,X-CT obtains the maximal contributive porosity,followed by MIP and NMR.展开更多
Development of microstructure of early cement paste （0-6 h） was investigated with 1H low- field NMR. It was found that T2 （transverse relaxation time） distributions of fresh cement paste were bimodal and two peaks...Development of microstructure of early cement paste （0-6 h） was investigated with 1H low- field NMR. It was found that T2 （transverse relaxation time） distributions of fresh cement paste were bimodal and two peaks were ＇long component＇ and ＇short component＇. Separation degree of two peaks was a sign of exchange of water within flocculation and outside flocculation. Factors such as water cement ratio, specific surface area and dosage of superplasticizer had influences on the separation degree： the separation degree increased with the water cement ratio; the separation degree of cement paste prepared with cement with a high specific surface area was zero; dosage of superplasticizer will decrease separation degree. Results also suggested that T2 distribution gradually moved to the left and T2 of long component and initial fluidity were linearly correlated.展开更多
The properties and structures of thermotropical liquid crystalline copolyesters based on p-hydroxybenzoic acid (PHBA), terephthalic acid (TPR) and bisphenol A (BPA) were studied by DSC, WAXD, hot stage polarized micro...The properties and structures of thermotropical liquid crystalline copolyesters based on p-hydroxybenzoic acid (PHBA), terephthalic acid (TPR) and bisphenol A (BPA) were studied by DSC, WAXD, hot stage polarized microscopy and NMR. It was found that most of the copolyesters were soluble in many common organic solvents. The copolyesters had low T-m/T-f values and a broad range of liquid crystal phase, making the polymers readily melt-processable. The effects of annealing at different temperatures on the copolyester containing 33% PHBA were also discussed. It was noted that annealing at ca. 200 degrees C (below Tc - n) could lead to the increasing of the crystallinity of the copolyester while the microstructure and sequence structure had not changed. Annealing at ca. 280 degrees C (near Tc - n) could bring a change of crystal and sequence structure and simultaneously made the microdomains be ordered more perfectly.展开更多
基金Funded by the National Natural Science Foundation of China(No.51178339)the National Basic Research Program(No.2009CB623104-5)
文摘Development of microstructure of early cement paste (0–6 h) was investigated with 1H low-field NMR. It was found that T 2 (transverse relaxation time) distributions of fresh cement paste were bimodal and two peaks were ‘long component’ and ‘short component’. Separation degree of two peaks was a sign of exchange of water within flocculation and outside flocculation. Factors such as water cement ratio, specific surface area and dosage of superplasticizer had influences on the separation degree: the separation degree increased with the water cement ratio; the separation degree of cement paste prepared with cement with a high specific surface area was zero; dosage of superplasticizer will decrease separation degree. Results also suggested that T 2 distribution gradually moved to the left and T 2 of long component and initial fluidity were linearly correlated.
基金Guangdong Basic and Applied Basic Research Found ation(Guangdong Province,China)general project for the financial support。
文摘Organic ionic plastic crystals(OIPCs)are emerging as an important material family for solid-state electrolytes and many other applications.They have significant advantages over conventional electrolyte materials,such as high ionic conductivity,non-flammability,and plasticity.Various nuclear magnetic resonance(NMR)spectroscopy techniques including solid-state NMR,pulsed-field gradient(PFG)NMR,and magnetic resonance imaging(MRI)etc.,provide us a versatile toolkit to understand the fundamental level structures,molecular dynamics,and ionic interactions in these materials.This article reviews the commonly used NMR methods including solid-and solution-state NMR,PFG-NMR,dynamic nuclear polarization(DNP)and the application of these methods in revealing the microscopic level structures and ion-transport mechanisms in OIPC materials.
文摘We built a three-dimensional irregular network model which can adequately describe reservoir rock pore-throat structures. We carried out numerical simulations to study the NMR T2 distribution of water-saturated rocks. The results indicate that there is a good correlation between T2 distribution and the pore radius frequency histogram. The total T2 distribution can be partitioned into pore body and pore throat parts. The effect of parameters including throat radius, pore-throat ratio, and coordination number of the micro- pore structure on the T2 distribution can be evaluated individually. The result indicates that： 1 ） with the increase of the pore throat radius, the T2 distribution moves toward longer relaxation times and its peak intensity increases; 2） with the increase of the pore-throat ratio, the T2 distribution moves towards longer T2 with the peak intensity increasing and the overlap between pore body T2 and pore throat T2 decreasing; 3） With the increase of connectivity, the short T2 component increases and peak signal intensity decreases slightly.
文摘The composition and the microstructures of isoprene-methyl methacrylate copolymers havebeen quantitatively studied by 250 MHz 1H-NMR spectra. Applying two lanthanide shiftreagents, by examining the separation of resonance peaks of the 1,4-isoprene olefin proton,I-centred triad distributions, and even I-cectred pentad fractions are measured. It is con-firmed that there is a penultimate of effect in this free radical copolymerization and the reac-tivity ratios established corresponding to Second-order Markov chain model are r11=0.48,rMI=0.86, rMM=0.51 and rIM=0.43, respectively. The observed I-centred pentad fraetions andM-centred triad distributions agree with the above results.
基金Thanks to the financial supports provided by the Natural Science Foundation of Zhejiang Province(LY17E090007,LQ18G010007,and LY19E90006)the National Natural Science Foundation of China(Grant No.51279181).
文摘Permeability is a major indicator of concrete durability,and depends primarily on the microstructure characteristics of concrete,including its porosity and pore size distribution.In this study,a variety of concrete samples were prepared to investigate their microstructure characteristics via nuclear magnetic resonance(NMR),mercury intrusion porosimetry(MIP),and X-ray computed tomography(X-CT).Furthermore,the chloride diffusion coefficient of concrete was measured to explore its correlation with the microstructure of the concrete samples.Results show that the proportion of pores with diameters<1000 nm obtained by NMR exceeds that obtained by MIP,although the difference in the total porosity determined by both methods is minimal.X-CT measurements obtained a relatively small porosity;however,this likely reflcts the distribution of large pores more accurately.A strong correlation is observed between the chloride diffusion coefficient and the porosity or contributive porosity of pores with sizes<1000 nm.Moreover,microstructure parameters measured via NMR reveal a lower correlation coefficient R2 versus the chloride diffusion coefficient relative to the parameters determined via MIP,as NMR can measure non-connected as well as connected pores.In addition,when analyzing pores with sizes>50 um,X-CT obtains the maximal contributive porosity,followed by MIP and NMR.
基金Funded by the National Natural Science Foundation of China （No. 51178339）, and the National Basic Research Program （No. 2009CB623104-5）
文摘Development of microstructure of early cement paste （0-6 h） was investigated with 1H low- field NMR. It was found that T2 （transverse relaxation time） distributions of fresh cement paste were bimodal and two peaks were ＇long component＇ and ＇short component＇. Separation degree of two peaks was a sign of exchange of water within flocculation and outside flocculation. Factors such as water cement ratio, specific surface area and dosage of superplasticizer had influences on the separation degree： the separation degree increased with the water cement ratio; the separation degree of cement paste prepared with cement with a high specific surface area was zero; dosage of superplasticizer will decrease separation degree. Results also suggested that T2 distribution gradually moved to the left and T2 of long component and initial fluidity were linearly correlated.
文摘The properties and structures of thermotropical liquid crystalline copolyesters based on p-hydroxybenzoic acid (PHBA), terephthalic acid (TPR) and bisphenol A (BPA) were studied by DSC, WAXD, hot stage polarized microscopy and NMR. It was found that most of the copolyesters were soluble in many common organic solvents. The copolyesters had low T-m/T-f values and a broad range of liquid crystal phase, making the polymers readily melt-processable. The effects of annealing at different temperatures on the copolyester containing 33% PHBA were also discussed. It was noted that annealing at ca. 200 degrees C (below Tc - n) could lead to the increasing of the crystallinity of the copolyester while the microstructure and sequence structure had not changed. Annealing at ca. 280 degrees C (near Tc - n) could bring a change of crystal and sequence structure and simultaneously made the microdomains be ordered more perfectly.
