The phase transition of two kinds of solvent-induced crystalline syndiotactic polystyrene (sPS). gamma-sPS and delta(c)-sPS, has been studied via WAXD and DSC. gamma-sPS transform to a-sPS at 195-225 degrees C before ...The phase transition of two kinds of solvent-induced crystalline syndiotactic polystyrene (sPS). gamma-sPS and delta(c)-sPS, has been studied via WAXD and DSC. gamma-sPS transform to a-sPS at 195-225 degrees C before melt during heating, whereas delta(e)-sPS transform to first gamma-sPS and then a-sPS at 100-200 degrees C and 200-215 degrees C, respectively. The transition of delta(e)-gamma and gamma-a occurs for below melting point of sPS indicates they are all solid-solid transition.展开更多
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
In a previous paper, we have reported the relationship between the crystallite orientation of the evaporated film of copper phthalacyanine （PcCu） （α-form） and the incident angle of molecular beam at 10-5 torr. In...In a previous paper, we have reported the relationship between the crystallite orientation of the evaporated film of copper phthalacyanine （PcCu） （α-form） and the incident angle of molecular beam at 10-5 torr. In this paper, we shall show some research results about vacuum effects on the crystal forms and the morphology of the evaporat-展开更多
Cefazolin sodium can form both - and -form crystals. It also can form dehydrated crystalline and amorphous products through different production processes. Because different polymorphic medicines usually have differen...Cefazolin sodium can form both - and -form crystals. It also can form dehydrated crystalline and amorphous products through different production processes. Because different polymorphic medicines usually have different physical and chemical properties, it is critical to emphasize the crystallization control of polymorphic medicines. Near-infrared (NIR) analysis, which incorporates a combination of NIR spectroscopic techniques and multivariate chemometric methods, is considered a powerful tool for the determination of the crystallinity of polymorphic drugs. The selection of optimal spectral ranges that correlate with the lattice specificity and content specificity is crucial to obtaining a specific NIR model. In the present work, near-infrared (NIR) spectra of cefazolin sodium with different crystal forms created through different processes were studied. The results suggest that wavelengths within the range of 9102.7-8597.5 cm-1 is related to the specificity of the cefazolin sodium crystal lattice and that the range of 6001.6-5496.4 cm-1 is associated with the quantitative content of cefazolin sodium. The two ab- sorptions are caused by the second overtone of the C-H stretching band (3υC-H) and the first overtone of C-H stretching band (2υC-H), respectively. Using these results, we established a suitable method of constructing a universal quantitative model by using mixed samples in different crystal forms as a calibration set, selecting a content-specific range (6001.6-5496.4 cm-1 ), and adding lattice-related spectral ranges where appropriate. This may provide a framework for the construction of prediction models for polymorphic medicines.展开更多
The metallic Zr65Ni25Ti10（mole fraction, %） glass has been fabricated by a single roller melt-spinning method. The glass forming ability（GFA） and thermal stability of the Zr65Ni25Ti10 melt-spun ribbons were invest...The metallic Zr65Ni25Ti10（mole fraction, %） glass has been fabricated by a single roller melt-spinning method. The glass forming ability（GFA） and thermal stability of the Zr65Ni25Ti10 melt-spun ribbons were investigated by using X-ray diffraction（XRD） and differential scanning calorimetry（DSC） in the mode of continuous heating. It is shown that the reduced glass transition temperature (Trg) is 0.506 and the supercooled liquid region （ΔTx） is 30 K. Two exothermic peaks were observed in the DSC curves of the as-quenched ribbon, which indicates that the crystallization process undergoes two different stages. The phase transformation during the isothermal annealing was investigated by X-ray diffraction（XRD） and transmission electronic microscope（TEM）. It is observed that the metastable FCC Zr2Ni（Fd3m, a=12.27 ） precipitated while annealing in the suppercooled region（615 K） and the stable BCT Zr2Ni（I4/mcm, a=6.499 , c=5.270 ） precipitated while annealing at higher temperature（673 K or 723 K）. The crystallines are on nanoscale, with grain size of 1530 nm. The reason for the precipitation of the different structural Zr2Ni from the glassy matrix under different annealing conditions was discussed based on the concept of multi-component chemical short range order（MCSRO）.展开更多
Two polymorphic forms （forms I and IV） of antidepressant bupropion hydrobro- mides were prepared and characterized by powder X-ray single-crystal diffractometer. Lots of commercial substances may consist of form I. ...Two polymorphic forms （forms I and IV） of antidepressant bupropion hydrobro- mides were prepared and characterized by powder X-ray single-crystal diffractometer. Lots of commercial substances may consist of form I. Form I crystallizes in the triclinic system, space group P1^- with Z= 2, a = 7.6943（8）, b = 7.9347（9）, c = 13.8558（15） A, a = 85.971（3）, β = 85.619（2）, γ = 65.974（3）°, V = 769.66（14） A^3, Dc= 1.384 g/cm^3, formula C13H19C1NOBr, F（000） = 328, p = 2.83 mm^-1, the final R = 0.0579 and wR = 0.1282 for 1756 observed reflections with I 〉 2σ（I）. Another polymorphic form, IV, belongs to the orthorhombic system, space group Pbca with a = 8.6365（3）, b = 12.4167（4）, c = 27.7299（9） A, Z = 8, V= 2973.67（17） A^3, Dc= 1.432 g/cm^3, formula C13H19CINOBr, F（000） = 1312,μ = 2.93 mm^-1, the final R = 0.044 and wR = 0.1093 for 2018 observed reflections with I 〉 2σ（I）. In the crystal structure of the two polymorphic forms, expected proton transfer from HBr to amino group of bupropion molecule occurs and intramolecular and intermolecular hydrogen bonds N-H…Br are formed. These interactions result in hydrogen-bond dimers in these two forms. The bupropion molecule adopts different conformations in the two investigated solid state modifications.展开更多
The thermal stability and the kinetics of glass transition and crystallization for Zr75-xNi25Alx （x = 8-15） metallic glasses were investigated using differential scanning calorimetry （DSC） under continuous heating...The thermal stability and the kinetics of glass transition and crystallization for Zr75-xNi25Alx （x = 8-15） metallic glasses were investigated using differential scanning calorimetry （DSC） under continuous heating conditions. The apparent activation energy of glass transition rises monotonously with the A1 content increasing; the activation energy of crystallization increases with A1 changing from 8at% to 15at%, and then decreases with A1 further up to 24at%, which exhibits a good correlation to the thermal stability and the glass-forming ability （GFA）. The Zr60Ni25A115 metallic glass with the largest supercooled liquid region and GFA possesses the highest activation energy of crystallization. The relation between the thermal stability, GFA and activation energy of crystallization was discussed in terms of the primary precipitated phases.展开更多
Ti 61.67 Zr 17.15 Ni 14.80 Cu 6.38 (atom fraction, %) metallic glass has applications in brazing. Using the hammer and anvil technique, Ti 61.67 Zr 17.15 Ni 14.80 Cu 6.38 metallic glass was prepared. The crystallizati...Ti 61.67 Zr 17.15 Ni 14.80 Cu 6.38 (atom fraction, %) metallic glass has applications in brazing. Using the hammer and anvil technique, Ti 61.67 Zr 17.15 Ni 14.80 Cu 6.38 metallic glass was prepared. The crystallization behavior for this metallic glass was investigated by differential scanning calorimetry(DSC), X ray diffractometry(XRD) and transmission electron microscopy(TEM). There are three stages in DSC curves of crystallization. The reduced glass temperature T rg is 0.42. The kinetic parameters of crystallization were calculated by a set of equations of the maximum crystallization rate. The crystalline phase formed in the MSI(Metastable stage I) is Zr 2Cu, in the MSII is α Ti and in the MSIII is Ti 2Ni. This kind of alloy has lower glass forming ability, and the Ti 61.67 Zr 17.15 Ni 14.80 Cu 6.38 metallic glass has lower thermal stability.展开更多
New Fe-based multicomponent amorphous alloys have been developed recently based on empirical rules for large glass forming ability(GFA). In the present investigation, the master alloy ingot with the nominal compositio...New Fe-based multicomponent amorphous alloys have been developed recently based on empirical rules for large glass forming ability(GFA). In the present investigation, the master alloy ingot with the nominal composition of Fe 61Co 7Zr 10Mo 5W 2B 15(mole fraction, %) was prepared by arc-melting under Ti-gettered Ar atmosphere. The Fe-based buttons with different transverse cross sections were fabricated by arc-melting method, and the d 2.5 mm Fe-based rods were manufactured by injection technique. Characterization of the ingots and the parameters associated with the thermal stability were carried out by X-ray diffractometry(XRD) and high temperature differential scanning calorimeter(DSC), respectively. The interval of the supercooled liquid region is 39 K for the Fe-based alloy. The GFA of Fe-based alloys is relatively lower, to the buttons obtained are all crystallized. The Fe-based rod exhibites a high Vickers hardness up to HV 1 329. In addition, an amorphous-crystalline transition layers are observed in the rod. This transition zone is caused by unhomogeneous temperature distribution and relatively lower GFA for Fe-based alloys.展开更多
Syndiotactic polypropylene （sPP） as-spun fiber （sPP1） and drawn fiber （sPP2） were prepared by melt-spinning and melt-spinning/hot-drawing, respectively. The structure transition of the two fibers induced by anne...Syndiotactic polypropylene （sPP） as-spun fiber （sPP1） and drawn fiber （sPP2） were prepared by melt-spinning and melt-spinning/hot-drawing, respectively. The structure transition of the two fibers induced by annealing at different temperatures and the corresponding mechanical properties were subsequently investigated by the combination of Fourier transform infrared spectroscopy （FTIR）, wide-angle X-ray diffraction （WAXD） and tensile testing. The results indicate that the chain conformation and crystal forms of the two sPP fibers are not obviously changed at low annealing temperature （40℃）. With increasing the annealing temperature, the trans-planar conformation and mesophase in sPP1 and sPP2 fibers can be completely transformed to helical conformation and crystal form I under tension. Upon removing the tension, a small amount of mesophase and trans-planar conformation will be regained. The mechanical properties of the annealed fibers are manifestly dependent on their initial structure and the annealing temperature.展开更多
基金the open laboratory funds of Chinese Academy of Sciences.
文摘The phase transition of two kinds of solvent-induced crystalline syndiotactic polystyrene (sPS). gamma-sPS and delta(c)-sPS, has been studied via WAXD and DSC. gamma-sPS transform to a-sPS at 195-225 degrees C before melt during heating, whereas delta(e)-sPS transform to first gamma-sPS and then a-sPS at 100-200 degrees C and 200-215 degrees C, respectively. The transition of delta(e)-gamma and gamma-a occurs for below melting point of sPS indicates they are all solid-solid transition.
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In a previous paper, we have reported the relationship between the crystallite orientation of the evaporated film of copper phthalacyanine （PcCu） （α-form） and the incident angle of molecular beam at 10-5 torr. In this paper, we shall show some research results about vacuum effects on the crystal forms and the morphology of the evaporat-
基金the National Key New Drug R&D Program Foundation of China (2010ZX09401-403) for the financial support
文摘Cefazolin sodium can form both - and -form crystals. It also can form dehydrated crystalline and amorphous products through different production processes. Because different polymorphic medicines usually have different physical and chemical properties, it is critical to emphasize the crystallization control of polymorphic medicines. Near-infrared (NIR) analysis, which incorporates a combination of NIR spectroscopic techniques and multivariate chemometric methods, is considered a powerful tool for the determination of the crystallinity of polymorphic drugs. The selection of optimal spectral ranges that correlate with the lattice specificity and content specificity is crucial to obtaining a specific NIR model. In the present work, near-infrared (NIR) spectra of cefazolin sodium with different crystal forms created through different processes were studied. The results suggest that wavelengths within the range of 9102.7-8597.5 cm-1 is related to the specificity of the cefazolin sodium crystal lattice and that the range of 6001.6-5496.4 cm-1 is associated with the quantitative content of cefazolin sodium. The two ab- sorptions are caused by the second overtone of the C-H stretching band (3υC-H) and the first overtone of C-H stretching band (2υC-H), respectively. Using these results, we established a suitable method of constructing a universal quantitative model by using mixed samples in different crystal forms as a calibration set, selecting a content-specific range (6001.6-5496.4 cm-1 ), and adding lattice-related spectral ranges where appropriate. This may provide a framework for the construction of prediction models for polymorphic medicines.
文摘The metallic Zr65Ni25Ti10（mole fraction, %） glass has been fabricated by a single roller melt-spinning method. The glass forming ability（GFA） and thermal stability of the Zr65Ni25Ti10 melt-spun ribbons were investigated by using X-ray diffraction（XRD） and differential scanning calorimetry（DSC） in the mode of continuous heating. It is shown that the reduced glass transition temperature (Trg) is 0.506 and the supercooled liquid region （ΔTx） is 30 K. Two exothermic peaks were observed in the DSC curves of the as-quenched ribbon, which indicates that the crystallization process undergoes two different stages. The phase transformation during the isothermal annealing was investigated by X-ray diffraction（XRD） and transmission electronic microscope（TEM）. It is observed that the metastable FCC Zr2Ni（Fd3m, a=12.27 ） precipitated while annealing in the suppercooled region（615 K） and the stable BCT Zr2Ni（I4/mcm, a=6.499 , c=5.270 ） precipitated while annealing at higher temperature（673 K or 723 K）. The crystallines are on nanoscale, with grain size of 1530 nm. The reason for the precipitation of the different structural Zr2Ni from the glassy matrix under different annealing conditions was discussed based on the concept of multi-component chemical short range order（MCSRO）.
基金supported by the Natural Science Foundation of Zhejiang Province (J200801)
文摘Two polymorphic forms （forms I and IV） of antidepressant bupropion hydrobro- mides were prepared and characterized by powder X-ray single-crystal diffractometer. Lots of commercial substances may consist of form I. Form I crystallizes in the triclinic system, space group P1^- with Z= 2, a = 7.6943（8）, b = 7.9347（9）, c = 13.8558（15） A, a = 85.971（3）, β = 85.619（2）, γ = 65.974（3）°, V = 769.66（14） A^3, Dc= 1.384 g/cm^3, formula C13H19C1NOBr, F（000） = 328, p = 2.83 mm^-1, the final R = 0.0579 and wR = 0.1282 for 1756 observed reflections with I 〉 2σ（I）. Another polymorphic form, IV, belongs to the orthorhombic system, space group Pbca with a = 8.6365（3）, b = 12.4167（4）, c = 27.7299（9） A, Z = 8, V= 2973.67（17） A^3, Dc= 1.432 g/cm^3, formula C13H19CINOBr, F（000） = 1312,μ = 2.93 mm^-1, the final R = 0.044 and wR = 0.1093 for 2018 observed reflections with I 〉 2σ（I）. In the crystal structure of the two polymorphic forms, expected proton transfer from HBr to amino group of bupropion molecule occurs and intramolecular and intermolecular hydrogen bonds N-H…Br are formed. These interactions result in hydrogen-bond dimers in these two forms. The bupropion molecule adopts different conformations in the two investigated solid state modifications.
基金supported by the Fundamental Research Funds for the Central Universities(Nos.DUT11RC(3)70 and DUT11RC(3)29)the National Natural Science Foundation of China(No.51171034)the China Postdoctoral Science Foundation Funded Project(No.2012M510802)
文摘The thermal stability and the kinetics of glass transition and crystallization for Zr75-xNi25Alx （x = 8-15） metallic glasses were investigated using differential scanning calorimetry （DSC） under continuous heating conditions. The apparent activation energy of glass transition rises monotonously with the A1 content increasing; the activation energy of crystallization increases with A1 changing from 8at% to 15at%, and then decreases with A1 further up to 24at%, which exhibits a good correlation to the thermal stability and the glass-forming ability （GFA）. The Zr60Ni25A115 metallic glass with the largest supercooled liquid region and GFA possesses the highest activation energy of crystallization. The relation between the thermal stability, GFA and activation energy of crystallization was discussed in terms of the primary precipitated phases.
文摘Ti 61.67 Zr 17.15 Ni 14.80 Cu 6.38 (atom fraction, %) metallic glass has applications in brazing. Using the hammer and anvil technique, Ti 61.67 Zr 17.15 Ni 14.80 Cu 6.38 metallic glass was prepared. The crystallization behavior for this metallic glass was investigated by differential scanning calorimetry(DSC), X ray diffractometry(XRD) and transmission electron microscopy(TEM). There are three stages in DSC curves of crystallization. The reduced glass temperature T rg is 0.42. The kinetic parameters of crystallization were calculated by a set of equations of the maximum crystallization rate. The crystalline phase formed in the MSI(Metastable stage I) is Zr 2Cu, in the MSII is α Ti and in the MSIII is Ti 2Ni. This kind of alloy has lower glass forming ability, and the Ti 61.67 Zr 17.15 Ni 14.80 Cu 6.38 metallic glass has lower thermal stability.
文摘New Fe-based multicomponent amorphous alloys have been developed recently based on empirical rules for large glass forming ability(GFA). In the present investigation, the master alloy ingot with the nominal composition of Fe 61Co 7Zr 10Mo 5W 2B 15(mole fraction, %) was prepared by arc-melting under Ti-gettered Ar atmosphere. The Fe-based buttons with different transverse cross sections were fabricated by arc-melting method, and the d 2.5 mm Fe-based rods were manufactured by injection technique. Characterization of the ingots and the parameters associated with the thermal stability were carried out by X-ray diffractometry(XRD) and high temperature differential scanning calorimeter(DSC), respectively. The interval of the supercooled liquid region is 39 K for the Fe-based alloy. The GFA of Fe-based alloys is relatively lower, to the buttons obtained are all crystallized. The Fe-based rod exhibites a high Vickers hardness up to HV 1 329. In addition, an amorphous-crystalline transition layers are observed in the rod. This transition zone is caused by unhomogeneous temperature distribution and relatively lower GFA for Fe-based alloys.
基金supported by the National Natural Science Foundation of China(No.50603029)the Innovation Foundation of Center for Molecular Science,Chinese Academy of Sciences(CMS-Y200724)
文摘Syndiotactic polypropylene （sPP） as-spun fiber （sPP1） and drawn fiber （sPP2） were prepared by melt-spinning and melt-spinning/hot-drawing, respectively. The structure transition of the two fibers induced by annealing at different temperatures and the corresponding mechanical properties were subsequently investigated by the combination of Fourier transform infrared spectroscopy （FTIR）, wide-angle X-ray diffraction （WAXD） and tensile testing. The results indicate that the chain conformation and crystal forms of the two sPP fibers are not obviously changed at low annealing temperature （40℃）. With increasing the annealing temperature, the trans-planar conformation and mesophase in sPP1 and sPP2 fibers can be completely transformed to helical conformation and crystal form I under tension. Upon removing the tension, a small amount of mesophase and trans-planar conformation will be regained. The mechanical properties of the annealed fibers are manifestly dependent on their initial structure and the annealing temperature.
