The microfibril angle of fiber walls is an ultra-mieroscopic feature affecting the performance of wood products. It is therefore essential to get more definitive information to improve selection and utilization. X-ray...The microfibril angle of fiber walls is an ultra-mieroscopic feature affecting the performance of wood products. It is therefore essential to get more definitive information to improve selection and utilization. X-ray diffraction is a rapid method for measuring microfibril angles. In this paper, the variability of microfibril angle in plantation-grown Masson pine was investigated by peak-fitting method. This method was compared with the traditional hand-drawn method, 40% peak height method and half peak height method. X-ray diffraction measurements indicated that the microfibril angle changed as a function of the position in the tree. The mean microfibril angle decreased more gradually as the distance increased from the pith and reached the same level in mature wood. The microfibril angle also seemed to decrease clearly from the base upward. Differences of angle-intensity curves between heartwood and sapwood were also examined.展开更多
Glancing Angle X-ray Diffraction (GAXRD) is introduced as a direct, non-destructive, surface-sensitive technique for analysis of thin films. The method was applied to polycrystalline thin films (namely, titanium oxide...Glancing Angle X-ray Diffraction (GAXRD) is introduced as a direct, non-destructive, surface-sensitive technique for analysis of thin films. The method was applied to polycrystalline thin films (namely, titanium oxide, zinc selenide, cadmium selenide and combinations thereof) obtained by electrochemical growth, in order to determine the composition of ultra-thin surface layers, to estimate film thickness, and perform depth profiling of multilayered heterostructures. The experimental data are treated on the basis of a simple absorption-diffraction model involving the glancing angle of X-ray incidence.展开更多
The microfibril angle of seven poplar clones was determined by using X-ray diffraction technique. Microfibril angle, wood basic density, fiber length, fiber width and cellulose content were assessed for every growth r...The microfibril angle of seven poplar clones was determined by using X-ray diffraction technique. Microfibril angle, wood basic density, fiber length, fiber width and cellulose content were assessed for every growth ring at breast height for all sample trees. Significant variation in microfibril angle was observed among growth rings. Mean microfibril angle (MFA) at breast height varied from 7.8?to 28?between growth rings with cambial age and showed a consistent pith-to-bark trend of decline an-gles. Analysis of variance also indicated that there were significant differences in wood basic density, fiber length, fiber width and cellulose content between the growth rings, which had an increasing tendency from pith to bark. Correlations between MFA and examined wood properties were predominantly large and significant negative (?0.01), and the coefficients were -0.660 for cellulose content, -0.586 for fiber length, -0.516 for fiber width and -0.450 for wood basic density, respectively. Regression analysis with linear and curve estimation indicated that a quadratic function showed the largest R2 and the least standard error for describing the relationships between microfibril angle and measured wood properties, and the correlation coefficients were over -0.45 (n=125). The results from this study suggested that microfibril angle would be a good characteristic for improvement in the future breeding program of poplars.展开更多
Acetanilide, adipic acid and potassium hydrogen phthalate were chosen as nucleating agents of polyvinyl chloride（PVC）, and their effects on PVC crystallization were studied by differential scanning calorimetry, wide...Acetanilide, adipic acid and potassium hydrogen phthalate were chosen as nucleating agents of polyvinyl chloride（PVC）, and their effects on PVC crystallization were studied by differential scanning calorimetry, wide angle X-ray diffraction and fourier transform infrared spectroscopy. The experimental results indicate that all of the three additives are compatible with PVC to some extent, but adipic acid＇s compatibility with PVC is less satisfactory. The three additives can improve PVC crystallinity, and acetanilide can decrease PVC glass transition temperature（T）and narrow PVC melting range, while adipic acid and potassium hydrogen phthalate rise T of PVC and widen its melting range. All additives do not affect PVC crystal system and all g samples are in orthorhombic system. All additives can improve （200）, （110）, （210） and （201, 111） planes growing. Moreover, acetanilide and adipic acid can shrink PVC spacings and improve the crystal perfection of PVC, but potassium hydrogen phthalate swells spacings and reduces the perfection of PVC crystal.展开更多
Polypropylene copolymers (CPP) containing β-nucleating agent were investigated by differential scanningcalorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarizing light microscopy (PLM). The results show th...Polypropylene copolymers (CPP) containing β-nucleating agent were investigated by differential scanningcalorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarizing light microscopy (PLM). The results show thathigh content of β-phase crystals can also be formed for CPPs. Like PP homopolymers, the CPPs also have a most favorabletemperature near 132℃ for β-phase crystal growth. The crystallization rate of CPPs containing β-nucleating agent (β-CPP) ismuch greater than that of PP homopolymer containing β-nucleating agent (β-PP homopolymer). The observation ofspherulite morphology of β-CPP and β-PP homopolymer shows that the spherulites of β-CPP are more imperfect than thoseof β-PP homopolymer.展开更多
The mechanical properties of fibers were notably improved by incorporating 2,2＇-bis（trifluoromethyl）benzidine（TFMB） into 3,3＇,4,4＇-biphenyltetracarboxylic dianhydride（s-BPDA） and p-phenylenediamine（PPD） bac...The mechanical properties of fibers were notably improved by incorporating 2,2＇-bis（trifluoromethyl）benzidine（TFMB） into 3,3＇,4,4＇-biphenyltetracarboxylic dianhydride（s-BPDA） and p-phenylenediamine（PPD） backbone.The best strength and modulus of BPDA/PPD/TFMB polyimide（PI） fiber（diamine molar ratio of PPD/TFMB= 90/10） were 1.60 and 90 GPa,respectively,which was over two times that of BPDA/PPD PI fiber.SEM image showed that the cross-section of fibers at each stage was round and voids free.Besides,the ＂skin-core＂ and microfibrillar structure were not observed.The thermal properties of PI fibers were also investigated.The results showed that the fibers owned excellent thermal stability,moreover,the structural homogeneity of fibers were significantly improved by heat-drawn stage.The T g values were found to be around 300 °C by dynamic mechanical analysis（DMA）.Wide angle X-ray diffraction（WAXD） and small angle X-ray scattering（SAXS） experiments indicated that the order degree of longitudinal and lateral stacks,the molecular orientation and the structural homogeneity of fibers were improved in the preparation process of fibers.展开更多
Crystal structure of a novel aryl ether ketone polymer \{poly(aryl\} ether ketone ether ketone ketone containing meta phenyl \{linkage)(PEKEK m K)\} was determined by means of WAXD and ED. An orthorhombic unit cell is...Crystal structure of a novel aryl ether ketone polymer \{poly(aryl\} ether ketone ether ketone ketone containing meta phenyl \{linkage)(PEKEK m K)\} was determined by means of WAXD and ED. An orthorhombic unit cell is proposed containing two chains with a= 0.772 nm, b =0.604 nm and \{ c =\}2\^572 nm. According to the orthorhombic system, the 10 reflections of this polymer were indexed. [WT5HZ]展开更多
基金This study was financially supported by the National Natural Science Foundation of China （Grant Nos. 30371125 and 30400337）.
文摘The microfibril angle of fiber walls is an ultra-mieroscopic feature affecting the performance of wood products. It is therefore essential to get more definitive information to improve selection and utilization. X-ray diffraction is a rapid method for measuring microfibril angles. In this paper, the variability of microfibril angle in plantation-grown Masson pine was investigated by peak-fitting method. This method was compared with the traditional hand-drawn method, 40% peak height method and half peak height method. X-ray diffraction measurements indicated that the microfibril angle changed as a function of the position in the tree. The mean microfibril angle decreased more gradually as the distance increased from the pith and reached the same level in mature wood. The microfibril angle also seemed to decrease clearly from the base upward. Differences of angle-intensity curves between heartwood and sapwood were also examined.
文摘Glancing Angle X-ray Diffraction (GAXRD) is introduced as a direct, non-destructive, surface-sensitive technique for analysis of thin films. The method was applied to polycrystalline thin films (namely, titanium oxide, zinc selenide, cadmium selenide and combinations thereof) obtained by electrochemical growth, in order to determine the composition of ultra-thin surface layers, to estimate film thickness, and perform depth profiling of multilayered heterostructures. The experimental data are treated on the basis of a simple absorption-diffraction model involving the glancing angle of X-ray incidence.
基金This research was supported by National Natural Science Foundation of China (Grant No. 30070616).
文摘The microfibril angle of seven poplar clones was determined by using X-ray diffraction technique. Microfibril angle, wood basic density, fiber length, fiber width and cellulose content were assessed for every growth ring at breast height for all sample trees. Significant variation in microfibril angle was observed among growth rings. Mean microfibril angle (MFA) at breast height varied from 7.8?to 28?between growth rings with cambial age and showed a consistent pith-to-bark trend of decline an-gles. Analysis of variance also indicated that there were significant differences in wood basic density, fiber length, fiber width and cellulose content between the growth rings, which had an increasing tendency from pith to bark. Correlations between MFA and examined wood properties were predominantly large and significant negative (?0.01), and the coefficients were -0.660 for cellulose content, -0.586 for fiber length, -0.516 for fiber width and -0.450 for wood basic density, respectively. Regression analysis with linear and curve estimation indicated that a quadratic function showed the largest R2 and the least standard error for describing the relationships between microfibril angle and measured wood properties, and the correlation coefficients were over -0.45 (n=125). The results from this study suggested that microfibril angle would be a good characteristic for improvement in the future breeding program of poplars.
基金Scientific and Technological Project of Hubei Province(No.2002AA105A01)
文摘Acetanilide, adipic acid and potassium hydrogen phthalate were chosen as nucleating agents of polyvinyl chloride（PVC）, and their effects on PVC crystallization were studied by differential scanning calorimetry, wide angle X-ray diffraction and fourier transform infrared spectroscopy. The experimental results indicate that all of the three additives are compatible with PVC to some extent, but adipic acid＇s compatibility with PVC is less satisfactory. The three additives can improve PVC crystallinity, and acetanilide can decrease PVC glass transition temperature（T）and narrow PVC melting range, while adipic acid and potassium hydrogen phthalate rise T of PVC and widen its melting range. All additives do not affect PVC crystal system and all g samples are in orthorhombic system. All additives can improve （200）, （110）, （210） and （201, 111） planes growing. Moreover, acetanilide and adipic acid can shrink PVC spacings and improve the crystal perfection of PVC, but potassium hydrogen phthalate swells spacings and reduces the perfection of PVC crystal.
文摘Polypropylene copolymers (CPP) containing β-nucleating agent were investigated by differential scanningcalorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarizing light microscopy (PLM). The results show thathigh content of β-phase crystals can also be formed for CPPs. Like PP homopolymers, the CPPs also have a most favorabletemperature near 132℃ for β-phase crystal growth. The crystallization rate of CPPs containing β-nucleating agent (β-CPP) ismuch greater than that of PP homopolymer containing β-nucleating agent (β-PP homopolymer). The observation ofspherulite morphology of β-CPP and β-PP homopolymer shows that the spherulites of β-CPP are more imperfect than thoseof β-PP homopolymer.
基金Supported by the Science & Technology Development Program of Jilin Province,China(No.20100537)
文摘The mechanical properties of fibers were notably improved by incorporating 2,2＇-bis（trifluoromethyl）benzidine（TFMB） into 3,3＇,4,4＇-biphenyltetracarboxylic dianhydride（s-BPDA） and p-phenylenediamine（PPD） backbone.The best strength and modulus of BPDA/PPD/TFMB polyimide（PI） fiber（diamine molar ratio of PPD/TFMB= 90/10） were 1.60 and 90 GPa,respectively,which was over two times that of BPDA/PPD PI fiber.SEM image showed that the cross-section of fibers at each stage was round and voids free.Besides,the ＂skin-core＂ and microfibrillar structure were not observed.The thermal properties of PI fibers were also investigated.The results showed that the fibers owned excellent thermal stability,moreover,the structural homogeneity of fibers were significantly improved by heat-drawn stage.The T g values were found to be around 300 °C by dynamic mechanical analysis（DMA）.Wide angle X-ray diffraction（WAXD） and small angle X-ray scattering（SAXS） experiments indicated that the order degree of longitudinal and lateral stacks,the molecular orientation and the structural homogeneity of fibers were improved in the preparation process of fibers.
文摘Crystal structure of a novel aryl ether ketone polymer \{poly(aryl\} ether ketone ether ketone ketone containing meta phenyl \{linkage)(PEKEK m K)\} was determined by means of WAXD and ED. An orthorhombic unit cell is proposed containing two chains with a= 0.772 nm, b =0.604 nm and \{ c =\}2\^572 nm. According to the orthorhombic system, the 10 reflections of this polymer were indexed. [WT5HZ]
