A new kind of nano-crysta cellulose (NCC) prepared from natural cotton fiber has been obtained by the method ofacid hydrolysis. Compared to most other nanophase materials that derive from inorganic materials, our prod...A new kind of nano-crysta cellulose (NCC) prepared from natural cotton fiber has been obtained by the method ofacid hydrolysis. Compared to most other nanophase materials that derive from inorganic materials, our products are preparedfrom natural cotton fibers. The products are of spherical shape with mixed crystal forms of cellulose I and II. The preparationconditions determine the properties of the products. Prior treatment is a critical procedure. The properties of the products arealso strongly affected by such conditions as the kinds of acids used, the ratio of the acid mixture, the acid concentration, theultrasonic agitation time and hydrolysis temperature. The number average molecular weight of NCC is determined by gelpermeation chromatography (GPC). The particle size and shape were determined by transmission electron microscopy(TEM). X-ray diffraction was used to detect the crystallinity and average crystallite size of the panicle.展开更多
The CeO_2-ZrO_2 solid solutions were prepared by a reverse microemulsion method. The effect of preparation parameters on the surface area and crystalline form of the solid solutions were studied by the BET surface are...The CeO_2-ZrO_2 solid solutions were prepared by a reverse microemulsion method. The effect of preparation parameters on the surface area and crystalline form of the solid solutions were studied by the BET surface area and XRD analysis. The studies indicate that the separation of the microemulsion phase during the preparation procedure can decrease the specific surface area of sample, adding hydrogen peroxide in the matrix solution can increase the specific surface area and stability of sample. The surface area of sample calcined at 550 ℃ for 5 h is 149 m^2·g^(-1), and that calcined at 900 ℃ for 6 h is 88 m^2·g^(-1). The sample with tetragonal symmetry Ce_(0.5)Zr_(0.5)O_2 phase has a higher stability.展开更多
SiC powder was rapidly synthesized in an induction furnace with crystalline silicon cutting waste and active carbon as raw materials,and then SiC porous ceramics were prepared at 1600 t for 4 h with carbon embedded us...SiC powder was rapidly synthesized in an induction furnace with crystalline silicon cutting waste and active carbon as raw materials,and then SiC porous ceramics were prepared at 1600 t for 4 h with carbon embedded using the powder as raw material,the starch and the graphite as pore-forming agents.Effects of additions of different pore-forming agents on the phase composition,microstructures,physical properties,and cold crushing strength of the porous ceramics were investigated.The results show that the main crystalline phases of the synthetic powder areα-S iC(6H-SiC)andβ-SiC(3C-SiC).The phase composition of the porous ceramics includesα-S iC(6H-SiC),β-SiC(3C-SiC),FeSi,quartz and Si2N20.The apparent porosity and closed porosity of the porous ceramics prepared by adding starch are higher,and the cold compressive strength of the porous ceramics added with graphite is higher.As increasing the additions of the starch,the apparent porosity,closed porosity and linear shrinkage ratio of the porous ceramics increase,and the bulk density decreases correspondingly.When 20 mass%starch is added,the apparent porosity,closed porosity,linear shrinkage ratio and cold compressive strength are 57.05%,2.03%,5.10%and 10.20 MPa,respectively.展开更多
Isotactic polypropylene (iPP) with high content of ~ crystalline form was prepared by adding a series of new p form nucleators. The spherulites and morphology of//farm iPP (//-iPP) were investigated by wide-angle X-ra...Isotactic polypropylene (iPP) with high content of ~ crystalline form was prepared by adding a series of new p form nucleators. The spherulites and morphology of//farm iPP (//-iPP) were investigated by wide-angle X-ray diffraction(WAXD), polarizing microscope (PLM), scanning electron microscope (SEM) and small-angle light scattering (SALS). WAXD experimental results indicate that the amount of p form in iPP (K_x) increases with increasing /~ nucleator content from zero to 0.07 wt% or crystallization temperature T_c from 20 to 120℃ and that the highest K_x value is up to 0.95. PLM observations suggest that p spherulites exhibit bright color and that their Maltese Crosses display some concentric banding of a rather spiky, jagged character. Their !amellae are smooth and relaxed layer-plate like structure by SEM and their SALS H_v patterns arc four-petalled.展开更多
SiC porous ceramics were prepared at 1 400 ℃ for4 h with crystalline silicon cutting waste and activated carbon as main starting materials and NH4HCO3 as the pore-forming agent. Effects of NH4HCO3 additions( 0,20%,30...SiC porous ceramics were prepared at 1 400 ℃ for4 h with crystalline silicon cutting waste and activated carbon as main starting materials and NH4HCO3 as the pore-forming agent. Effects of NH4HCO3 additions( 0,20%,30%,40%,by mass) on the phase composition,microstructure,sintering properties,cold compressive strength and thermal shock resistance of as-prepared Si C porous ceramics were investigated. The results show that:( 1) addition of NH4HCO3 remarkably influences the apparent porosity and cold compressive strength of specimens. The apparent porosity achieves its maximum value( 63. 40%) when 40% NH4HCO3 is added,while the minimum cold compressive strength is 4. 77 MPa;( 2) the specimen with 40% NH4HCO3 has the best thermal shock resistance. The thermal cycling times between1 000 ℃ to room temperature reach 62;( 3) the addition of NH4HCO3 does not remarkably affect the phase composition of the specimens;( 4) the specimens include a large number of SiC particles and a small amount of SiC whiskers.展开更多
The molecular chain structure and crystalline structure of PB-ET copolyester made by con-densation polymerization are studied by means of <sup>13</sup>C nuclear magnetic resonance spectroscopy(<sup>1...The molecular chain structure and crystalline structure of PB-ET copolyester made by con-densation polymerization are studied by means of <sup>13</sup>C nuclear magnetic resonance spectroscopy(<sup>13</sup>C NMR),dynamic mechanical analysis （DMA）,wide angle X-ray scattering （WAXS）,depolarized light intensity （DLI） and stress-strain measurement（S-S）.It is shown that PB-ETcopolyester is a random copolymer.Because of different ratios of EG（ethylene glycol）to BD（butane diol）in the copolyester,its crystalline forms and mechanical properties vary remarkably.With the increasing amount of BD,its crystallization kinetic parameters n,k and t<sub>1/2</sub><sup>-1</sup> increaserapidly.When EG/BD equals 25/75 （mole ratio）,the copolyester has αβ transition as PBTdoes.展开更多
Natural cellulose with the crystal form of cellulose Ⅰ, when treated with condensed lye (e.g. 18%NaOH), can change into new crystal form of cellulose Ⅱ. But the nano-crystalline cellulose (NCC) can do it when only t...Natural cellulose with the crystal form of cellulose Ⅰ, when treated with condensed lye (e.g. 18%NaOH), can change into new crystal form of cellulose Ⅱ. But the nano-crystalline cellulose (NCC) can do it when only treated with dilute lye (e.g. 1%NaOH) at room temperature and even can dissolve into slightly concentrated lye (e.g. 4%NaOH).展开更多
通过酰胺化合物(NA-BW)引导等规聚丙烯(iPP)制备高水平β晶型聚丙烯(β-iPP),借助广角X射线衍射(WAXD),差示扫描量热仪(DSC)及偏光显微镜(POM)研究其结晶形态及结晶行为,并研究了β型成核剂对iPP力学性能的影响。结果表明:加入β型成核...通过酰胺化合物(NA-BW)引导等规聚丙烯(iPP)制备高水平β晶型聚丙烯(β-iPP),借助广角X射线衍射(WAXD),差示扫描量热仪(DSC)及偏光显微镜(POM)研究其结晶形态及结晶行为,并研究了β型成核剂对iPP力学性能的影响。结果表明:加入β型成核剂NA-BW后,iPP的晶型和球晶形态均发生变化;等温结晶研究表明聚丙烯的半结晶时间(t1/2)明显降低,即结晶速度加快,非等温结晶研究表明iPP的结晶温度提高;iPP的冲击强度大大提高,拉伸和弯曲性能却略有下降。当成核剂用量为3 m g/g时,悬臂梁缺口冲击强度达到最大值,提高达3.5倍,由49.35J/m提高到176.23 J/m。热稳定性实验表明β型成核剂对聚丙烯成核效果的热稳定性良好。展开更多
目的:研究盐酸乐卡地平Ⅰ、Ⅱ晶型及无定型对制剂制备的影响,为其制剂开发及一致性评价提供理论基础。方法:采用X-射线粉末衍射(XRD)、红外分光光度(IR)和差式扫描量热(DSC)法鉴定盐酸乐卡地平的3种晶型;采用XRD法比较粉粹、研磨、加压...目的:研究盐酸乐卡地平Ⅰ、Ⅱ晶型及无定型对制剂制备的影响,为其制剂开发及一致性评价提供理论基础。方法:采用X-射线粉末衍射(XRD)、红外分光光度(IR)和差式扫描量热(DSC)法鉴定盐酸乐卡地平的3种晶型;采用XRD法比较粉粹、研磨、加压工艺,湿法制粒中黏合剂溶剂(水、乙醇)和干燥温度(50、60、70℃)对盐酸乐卡地平3种晶型稳定性的影响;比较3种晶型盐酸乐卡地平片在水、盐酸、p H 4.5醋酸盐缓冲液、p H 6.8磷酸盐缓冲液4种介质中的体外溶出度。结果:XRD显示,Ⅰ、Ⅱ晶型均有特征衍射峰,且2θ值不一致,无定型无特征衍射峰;IR显示,3种晶型具有不同的吸收强度和吸收峰数目;DSC显示,Ⅰ、Ⅱ晶型分别在194.6、207.3℃有明显吸热峰,无定型在86.1℃有明显吸热峰、299.8℃有放热峰。粉粹、研磨、加压及干燥温度对3种晶型转变均无影响;湿法制粒时水对晶型转变无影响,乙醇会引起Ⅰ晶型的晶型转变。除在盐酸中Ⅰ晶型与Ⅱ晶型片比较f_2=68外,4种介质中3种晶型盐酸乐卡地平片溶出度两两比较的f_2均小于50。结论:XRD、IR、DSC法均能鉴定盐酸乐卡地平的3种晶型。用Ⅰ晶型制备盐酸乐卡地平片时,湿法制粒应避免使用乙醇作为黏合剂溶剂,建议使用水。不同晶型会影响所制盐酸乐卡地平片的体外溶出度。展开更多
基金This work was supported by the Special Funds for Major State Basic Research Projects (95-12 and G1999064800).
文摘A new kind of nano-crysta cellulose (NCC) prepared from natural cotton fiber has been obtained by the method ofacid hydrolysis. Compared to most other nanophase materials that derive from inorganic materials, our products are preparedfrom natural cotton fibers. The products are of spherical shape with mixed crystal forms of cellulose I and II. The preparationconditions determine the properties of the products. Prior treatment is a critical procedure. The properties of the products arealso strongly affected by such conditions as the kinds of acids used, the ratio of the acid mixture, the acid concentration, theultrasonic agitation time and hydrolysis temperature. The number average molecular weight of NCC is determined by gelpermeation chromatography (GPC). The particle size and shape were determined by transmission electron microscopy(TEM). X-ray diffraction was used to detect the crystallinity and average crystallite size of the panicle.
文摘The CeO_2-ZrO_2 solid solutions were prepared by a reverse microemulsion method. The effect of preparation parameters on the surface area and crystalline form of the solid solutions were studied by the BET surface area and XRD analysis. The studies indicate that the separation of the microemulsion phase during the preparation procedure can decrease the specific surface area of sample, adding hydrogen peroxide in the matrix solution can increase the specific surface area and stability of sample. The surface area of sample calcined at 550 ℃ for 5 h is 149 m^2·g^(-1), and that calcined at 900 ℃ for 6 h is 88 m^2·g^(-1). The sample with tetragonal symmetry Ce_(0.5)Zr_(0.5)O_2 phase has a higher stability.
文摘SiC powder was rapidly synthesized in an induction furnace with crystalline silicon cutting waste and active carbon as raw materials,and then SiC porous ceramics were prepared at 1600 t for 4 h with carbon embedded using the powder as raw material,the starch and the graphite as pore-forming agents.Effects of additions of different pore-forming agents on the phase composition,microstructures,physical properties,and cold crushing strength of the porous ceramics were investigated.The results show that the main crystalline phases of the synthetic powder areα-S iC(6H-SiC)andβ-SiC(3C-SiC).The phase composition of the porous ceramics includesα-S iC(6H-SiC),β-SiC(3C-SiC),FeSi,quartz and Si2N20.The apparent porosity and closed porosity of the porous ceramics prepared by adding starch are higher,and the cold compressive strength of the porous ceramics added with graphite is higher.As increasing the additions of the starch,the apparent porosity,closed porosity and linear shrinkage ratio of the porous ceramics increase,and the bulk density decreases correspondingly.When 20 mass%starch is added,the apparent porosity,closed porosity,linear shrinkage ratio and cold compressive strength are 57.05%,2.03%,5.10%and 10.20 MPa,respectively.
文摘Isotactic polypropylene (iPP) with high content of ~ crystalline form was prepared by adding a series of new p form nucleators. The spherulites and morphology of//farm iPP (//-iPP) were investigated by wide-angle X-ray diffraction(WAXD), polarizing microscope (PLM), scanning electron microscope (SEM) and small-angle light scattering (SALS). WAXD experimental results indicate that the amount of p form in iPP (K_x) increases with increasing /~ nucleator content from zero to 0.07 wt% or crystallization temperature T_c from 20 to 120℃ and that the highest K_x value is up to 0.95. PLM observations suggest that p spherulites exhibit bright color and that their Maltese Crosses display some concentric banding of a rather spiky, jagged character. Their !amellae are smooth and relaxed layer-plate like structure by SEM and their SALS H_v patterns arc four-petalled.
文摘SiC porous ceramics were prepared at 1 400 ℃ for4 h with crystalline silicon cutting waste and activated carbon as main starting materials and NH4HCO3 as the pore-forming agent. Effects of NH4HCO3 additions( 0,20%,30%,40%,by mass) on the phase composition,microstructure,sintering properties,cold compressive strength and thermal shock resistance of as-prepared Si C porous ceramics were investigated. The results show that:( 1) addition of NH4HCO3 remarkably influences the apparent porosity and cold compressive strength of specimens. The apparent porosity achieves its maximum value( 63. 40%) when 40% NH4HCO3 is added,while the minimum cold compressive strength is 4. 77 MPa;( 2) the specimen with 40% NH4HCO3 has the best thermal shock resistance. The thermal cycling times between1 000 ℃ to room temperature reach 62;( 3) the addition of NH4HCO3 does not remarkably affect the phase composition of the specimens;( 4) the specimens include a large number of SiC particles and a small amount of SiC whiskers.
文摘The molecular chain structure and crystalline structure of PB-ET copolyester made by con-densation polymerization are studied by means of <sup>13</sup>C nuclear magnetic resonance spectroscopy(<sup>13</sup>C NMR),dynamic mechanical analysis （DMA）,wide angle X-ray scattering （WAXS）,depolarized light intensity （DLI） and stress-strain measurement（S-S）.It is shown that PB-ETcopolyester is a random copolymer.Because of different ratios of EG（ethylene glycol）to BD（butane diol）in the copolyester,its crystalline forms and mechanical properties vary remarkably.With the increasing amount of BD,its crystallization kinetic parameters n,k and t<sub>1/2</sub><sup>-1</sup> increaserapidly.When EG/BD equals 25/75 （mole ratio）,the copolyester has αβ transition as PBTdoes.
文摘Natural cellulose with the crystal form of cellulose Ⅰ, when treated with condensed lye (e.g. 18%NaOH), can change into new crystal form of cellulose Ⅱ. But the nano-crystalline cellulose (NCC) can do it when only treated with dilute lye (e.g. 1%NaOH) at room temperature and even can dissolve into slightly concentrated lye (e.g. 4%NaOH).
文摘通过酰胺化合物(NA-BW)引导等规聚丙烯(iPP)制备高水平β晶型聚丙烯(β-iPP),借助广角X射线衍射(WAXD),差示扫描量热仪(DSC)及偏光显微镜(POM)研究其结晶形态及结晶行为,并研究了β型成核剂对iPP力学性能的影响。结果表明:加入β型成核剂NA-BW后,iPP的晶型和球晶形态均发生变化;等温结晶研究表明聚丙烯的半结晶时间(t1/2)明显降低,即结晶速度加快,非等温结晶研究表明iPP的结晶温度提高;iPP的冲击强度大大提高,拉伸和弯曲性能却略有下降。当成核剂用量为3 m g/g时,悬臂梁缺口冲击强度达到最大值,提高达3.5倍,由49.35J/m提高到176.23 J/m。热稳定性实验表明β型成核剂对聚丙烯成核效果的热稳定性良好。
文摘目的:研究盐酸乐卡地平Ⅰ、Ⅱ晶型及无定型对制剂制备的影响,为其制剂开发及一致性评价提供理论基础。方法:采用X-射线粉末衍射(XRD)、红外分光光度(IR)和差式扫描量热(DSC)法鉴定盐酸乐卡地平的3种晶型;采用XRD法比较粉粹、研磨、加压工艺,湿法制粒中黏合剂溶剂(水、乙醇)和干燥温度(50、60、70℃)对盐酸乐卡地平3种晶型稳定性的影响;比较3种晶型盐酸乐卡地平片在水、盐酸、p H 4.5醋酸盐缓冲液、p H 6.8磷酸盐缓冲液4种介质中的体外溶出度。结果:XRD显示,Ⅰ、Ⅱ晶型均有特征衍射峰,且2θ值不一致,无定型无特征衍射峰;IR显示,3种晶型具有不同的吸收强度和吸收峰数目;DSC显示,Ⅰ、Ⅱ晶型分别在194.6、207.3℃有明显吸热峰,无定型在86.1℃有明显吸热峰、299.8℃有放热峰。粉粹、研磨、加压及干燥温度对3种晶型转变均无影响;湿法制粒时水对晶型转变无影响,乙醇会引起Ⅰ晶型的晶型转变。除在盐酸中Ⅰ晶型与Ⅱ晶型片比较f_2=68外,4种介质中3种晶型盐酸乐卡地平片溶出度两两比较的f_2均小于50。结论:XRD、IR、DSC法均能鉴定盐酸乐卡地平的3种晶型。用Ⅰ晶型制备盐酸乐卡地平片时,湿法制粒应避免使用乙醇作为黏合剂溶剂,建议使用水。不同晶型会影响所制盐酸乐卡地平片的体外溶出度。
