Bulk metallic glasses with up to 72 mm critical section thickness have been obtained by conventional casting techniques and the properties of these materials, particularly the mechanical and magnetic properties have b...Bulk metallic glasses with up to 72 mm critical section thickness have been obtained by conventional casting techniques and the properties of these materials, particularly the mechanical and magnetic properties have been studied. These materials have been demonstrated to have novel properties which are fundamentally different from their crystalline counterparts. The recent status of research and development in formation, structure and properties of bulk metallic glasses is reviewed. The techniques to produce such bulk glasses are summarized and the glass forming ability and the critical cooling rate of these materials are discussed. Further consideration of the development and application of this new class of materiaIs will be proposed.展开更多
The polybutylaldehyde obtained by plasma polymerization was investigated by means of IR, X-ray diffraction, GC-MS, elementary analysis, TEM, electron diffraction and contact angle measurements etc. The results showed ...The polybutylaldehyde obtained by plasma polymerization was investigated by means of IR, X-ray diffraction, GC-MS, elementary analysis, TEM, electron diffraction and contact angle measurements etc. The results showed that the polymer formed in plasma is amorphous crosslinked polymer, and its backbone is made of carbon atoms. The surface energy of the polymer film is independent of the polymerization conditions. No addition reaction has taken place in the carbonyl group of butylaldehyde in the plasma condition. The result of the wettability measurements showed that the polymer film is generally hydrophobic and the surface energy of the film is about 41 dyn/cm, in which the dispersion force contribution is the majority. The electron diffraction proved that some crystal substance, even the single crystals were present in the polymer. X-ray diffraction also proved the presence of crystal and showed about 15% crystaUinity fraction.展开更多
Conductive polymer composites based on crystalline polymer matrix have been prepared by using an in-situ polymerization process of pyrrole in amorphous poly （ethylene terephthalate） （PET） film. The DSC and WAXD me...Conductive polymer composites based on crystalline polymer matrix have been prepared by using an in-situ polymerization process of pyrrole in amorphous poly （ethylene terephthalate） （PET） film. The DSC and WAXD measurement and SEM observation show that liquid-induced crystallization of PET matrix has occurred during the preparation of composite films. Depending upon the equilibrium degree of swelling and crystallinity, the limited depth of penetration of pyrrole molecules results in a skin-core structure of the composite film. The skin layer containing charge transfer intercalated polypyrrole has a surface resistance of 3.5×10;Ω. Rigid and heat-resistant polypyrrole molecules formed in PET film increase the tensile modulus and, especially, the rigidity of PET at elevated temperatures. However, they decrease the tensile strength and elongation at break, and impair the thermal ductility of PET.展开更多
A cobalt complex with mixed valence state [Co( Ⅰ ) (dppe)2CO]2 [Co2 ( Ⅱ )(dppe) Cl]6O2] (dppe = 1,2 - bis(diphenylphosphino) ethane) has been prepared. The compound crystallizes in triclinic space group P1 with unit...A cobalt complex with mixed valence state [Co( Ⅰ ) (dppe)2CO]2 [Co2 ( Ⅱ )(dppe) Cl]6O2] (dppe = 1,2 - bis(diphenylphosphino) ethane) has been prepared. The compound crystallizes in triclinic space group P1 with unit cell parameters: a=1. 1763(3) nm, b = 1. 2943(6) nm, c=2. 1507(9) nm, a=81. 44(4)°? ,β=82. 58(3)°, r = 79. 82(3)°, V = 3. 1691 nm3 and Z=1. The structure was solved by direct method according to ALPHA criterion and was refined by a block diagonal matrix least-squares procedure to final R= 0.084, Moreover, infared spectra, electronic reflection spectra and cyclic voltammetry curve were mearsured.展开更多
The synthesis,crystal structure and properties of the first Mn(III)-disulfide complex(Et_4N)[Mn(mp-mp)_2]were reported with the Mn(III) ion in a S_2O_4 octahedron distorted due to Jahn-Teller effect.Spectroscopic data...The synthesis,crystal structure and properties of the first Mn(III)-disulfide complex(Et_4N)[Mn(mp-mp)_2]were reported with the Mn(III) ion in a S_2O_4 octahedron distorted due to Jahn-Teller effect.Spectroscopic data revealed its paramagnetic properties.展开更多
The future intelligent era that will be brought about by 5G technology can be well predicted.For example,the connection between humans and smart wearable devices will become increasingly more intimate.Flexible wearabl...The future intelligent era that will be brought about by 5G technology can be well predicted.For example,the connection between humans and smart wearable devices will become increasingly more intimate.Flexible wearable pressure sensors have received much attention as a part of this process.Nevertheless,there is a lack of complete and detailed discussion on the recent research status of capacitive pressure sensors composed of polymer composites.Therefore,this article will mainly discuss the key concepts,preparation methods and main performance of flexible wearable capacitive sensors.The concept of a processing“toolbox”is used to review the developmental status of the dielectric layer as revealed in highly cited literature from the past five years.The preparation methods are categorized into types of processing:primary and secondary.Using these categories,the preparation methods and structure of the dielectric layer are discussed.Their influence on the final capacitive sensing behavior is also addressed.Recent developments in the electrode layer are also systematically reviewed.Finally,the results of the above discussion are summarized and future development trends are discussed.展开更多
The optical properties of substituted fluorenones with diverse structures have been analyzed using molecular orbital calculations in order to understand the structure-property relations. Based on theoretical predictio...The optical properties of substituted fluorenones with diverse structures have been analyzed using molecular orbital calculations in order to understand the structure-property relations. Based on theoretical predictions, synthesis of some model compounds has been attempted. The experimentally obtained optical properties are in close agreement with the theoretically obtained results.展开更多
The geometries, electronic structures and related properties of SimN8-m（0 〈 m 〈 8） clusters are studied using density functional theory （DFT） with hybrid functional B3LYP. The calculated results reveal several t...The geometries, electronic structures and related properties of SimN8-m（0 〈 m 〈 8） clusters are studied using density functional theory （DFT） with hybrid functional B3LYP. The calculated results reveal several trends. For any stoichiometric clusters, the lowest energy isomers with an alteration of N and Si atoms are favourable in energy if the numbers of Si and N atoms are large enough to form ... Si N-Si-N... alternative chains. The bond lengths of single Si-N bonds are very close to the corresponding values of the bulk and other SiN clusters. The geometries for N-rich and Si4N4 clusters are planar structures, but three-dimensional structures are favourable in energy for Si-rich clusters. With the increase of m, the isotropic polarizability and average polarizability increase, the total binding energies generally decrease, the HOMO-LUMO gap and vertical ionization potential oscillate with increasing number of valence electrons, and their values with even valence electrons are larger than those with odd valence electrons. The atomic charges, IR and Raman properties are also reported.展开更多
A new imidazolate bridged Cu^(2+),Zn^(2+)binuclear complex[(dtma) CulmZn (dtma)]ClO_4· 2.5H_2O taken as active site model for Cu,Zn-SOD has been synthesized and its crystal structure determined.All the bond lengt...A new imidazolate bridged Cu^(2+),Zn^(2+)binuclear complex[(dtma) CulmZn (dtma)]ClO_4· 2.5H_2O taken as active site model for Cu,Zn-SOD has been synthesized and its crystal structure determined.All the bond lengths, bond angles and the distance between Cu and Zn atoms in Cu-Im- Zn core of the model complex are close to those in Cu,Zn-SOD.ESR parameters of the model complex as a function of pH show that the imidazolate bridge is stable in pH range 10—12,and is broken on Zn side at pH～9.With decreasing pH,the imidazole is released at pH～4 and the dtma ligand dissociates from the Cu containing fragment at pH～2.4.展开更多
In this article, the quenched Nd_4.5Fe_75Co_1Si_l B_18.5 ribbons were prepared, and the structures and properties were investigated. The results show that the change of structures of Nd_4.5 Fe_75 Co_1 Si_1 B_18.5 qu...In this article, the quenched Nd_4.5Fe_75Co_1Si_l B_18.5 ribbons were prepared, and the structures and properties were investigated. The results show that the change of structures of Nd_4.5 Fe_75 Co_1 Si_1 B_18.5 quenched amorphous ribbons is Am→Am'+Fe_3B+Nd_2Fe_23B_3+Nd_2Fe_14B→Nd_2- Fe_14B when it is heated. The effect of crystallizing treatment temperature and time on the magnetic properties of the quenched alloy was studied. The magnetic properties of 16 m/s quenched ribbons for 710℃×1200 s crystallizing treatment reach _iH_c=238.6 hA/m, B_r=0.8987 T and (BH)max=51.39 kJ/m^3. The grain size is about DFe3=32 nm and DNd2Fe14B=22 nm.展开更多
Structures and properties of the blends of thermotropic liquid crystallinepolymer(LC70)and poly(ethylene terephthalate) (PET) were investigated by usingWAXD,DSC,SEM and mechanical test.The results revealed that Wc,x m...Structures and properties of the blends of thermotropic liquid crystallinepolymer(LC70)and poly(ethylene terephthalate) (PET) were investigated by usingWAXD,DSC,SEM and mechanical test.The results revealed that Wc,x markdly decreased withLC70/PET>30%,and at about LC70/PET=10%, this blend can yield better mechanicalproperties.In these blends LC70 can play the role of the nuclear agent for PET.SEMphoto showed that LC70/PET in in-situ composites possessed 'core-shell' structure andwas immiscible, but at LC70/PST=10%, the LC70 can be uniformly dispersed into matrix PET.展开更多
The traditional high-temperature preparation process of polyimide can cause many problems and limits the wider application in extreme conditions.An important challenge to be solved urgently is the reduction of imidiza...The traditional high-temperature preparation process of polyimide can cause many problems and limits the wider application in extreme conditions.An important challenge to be solved urgently is the reduction of imidization temperature.In this work,twelve kinds of polyimide films with different chain rigidity were prepared at low temperature of 200℃,in the absence or presence of imidazole used as the catalyst.The molecular rigidity and free volume were theoretically calculated,and relationship between structure and properties were systematically studied.The results show that imidization reaction under low temperatures is significantly affected by the rigidity of molecula r chains.The rigid structure of polyimide is not conducive to the low-temperature imidization,but this adverse effect can be eliminated by adding catalyst,resulting the notably increased imidization degree.The optical and thermal properties can be improved to a certain extent for the chemically catalyzed system,resulting in relatively higher heat resistance and thermal stability.While the mechanical performance could be determined by com plicating factors,greatly different from polyimide films prepa red by high temperature method.To investigate aggregation structures of film s,the effect of chain rigidity and catalyst on the stacking or orientation of molecular chains was further elaborated.This wo rk can contribute to the understanding of chemically catalyzed imidization that is rarely reported in the existing research,and will provide guidance for the low-temperature preparation of high-performance polyimides.展开更多
Conducting nanocomposites of poly （methyl methacrylate） （PMMA） and antimony doped tin oxide （ATO） were prepared by solution blending. The influences of ATO content on the electrical conductivity, thermal stabili...Conducting nanocomposites of poly （methyl methacrylate） （PMMA） and antimony doped tin oxide （ATO） were prepared by solution blending. The influences of ATO content on the electrical conductivity, thermal stability, and mechanical properties of the nanocomposites were investigated. A homogeneous dispersion of silane coupling agent modified ATO was achieved in PMMA matrix as evidenced by scanning electron microscopy. The resultant PMMA/silane-ATO nanocomposites were electrically conductive with significant conductivity enhancement at 4 wt pct. It was found that the composition at 4 wt pct ATO gave the higher tensile strength. Furthermore, it gave the largest elongation at break value among all the compositions. Thermal stability of the nanocomposites was remarkably enhanced by the incorporation of silane-ATO.展开更多
Direct current metal filtered cathodic vacuum arc （FCVA） and acetylene gas （C2H2） were wielded to synthesize Ti-containing amorphous carbon films on Si （100）. The influence of substrate bias voltage and acetylen...Direct current metal filtered cathodic vacuum arc （FCVA） and acetylene gas （C2H2） were wielded to synthesize Ti-containing amorphous carbon films on Si （100）. The influence of substrate bias voltage and acetylene gas on the microstructure and mechanical properties of the films were investigated. The results show that the phase of TiC in the （111） preferential crystallographic orientation exists in the film,and the main existing pattern of carbon is sp2. With increasing the acetylene flow rate,the contents of Ti and TiC phase of the film gradually reduce; however,the thickness of the film increases. When the substrate bias voltage reaches -600 V,the internal stress of the film reaches 1.6 GPa. The micro-hardness and elastic modulus of the film can reach 33.9 and 237.6 GPa,respectively,and the friction coefficient of the film is 0.25.展开更多
The TiO2-Co-TiO2 sandwich films were successfully grown on glass and silicon substrata making alternate use of radio frequency reactive magnetron sputtering and direct current magnetron sputtering. The structures and ...The TiO2-Co-TiO2 sandwich films were successfully grown on glass and silicon substrata making alternate use of radio frequency reactive magnetron sputtering and direct current magnetron sputtering. The structures and properties of these films were identified with X-ray diffraction （XRD）, Raman spectra and X-ray photoemission spectra （XPS）. It is shown that the sandwich film consists of two anatase TiO2 films with an embedded Co nano-film. The fact that, when the Co nano-film thickens, varied red shifts appear in optical absorption spectra may well be explained by the quantum confinement and tunnel effects. As for magnetic properties, the saturation magnetization, remnant magnetic induction and coercivity vary with the thickness of the Co nano-films. Moreover, the Co nano-film has a critical thickness of about 8.6 mn, which makes the coercivity of the composite film reach the maximum of about 1413 Oe.展开更多
The equilibrium geometries and electronic properties of CumSin （2 ≤m ＋ n ≤ 7） clusters have been studied by using density functional theory at the B3LYP/6-311＋G （d） level. Our results indicate that the structu...The equilibrium geometries and electronic properties of CumSin （2 ≤m ＋ n ≤ 7） clusters have been studied by using density functional theory at the B3LYP/6-311＋G （d） level. Our results indicate that the structure of CuSin （n 〈6） keeps the frame of the corresponding Sin cluster unchanged, while for CunSi clusters, the rectangular pyramid structure of Cu4Si is shown to be a building block in many structures of larger CunSi clusters. The growth patterns of CumSin clusters become more complicated as the number of Cu atoms increases. Both the binding energies and the fragmentation energies indicate that the Si-Si bond is stronger than the Cu-Si bond, and the latter is stronger than the Cu-Cu bond. Combining the fragmentation energies in the process CumSin →Cu＋Cum-l Sin and the second-order difference △2E（m） against the number of Cu atoms of CumSin, we conclude that CumSin clusters with even number of Cu atoms have higher stabilities than those with odd rn. According to frontier orbital analyses, there exists a mixed ionic and covalent bonding picture between Cu and Si atoms, and the Cud orbitals contribute little to the Cu-Si bonding. For a certain cluster size （m ＋ n = 3, 4, 5, 6, 7）, the energy gaps of the most stable CumSin clusters show odd-even oscillation with changing m, the clusters with odd m exhibit stronger chemical reactivity than those with even m.展开更多
Bamboo shoot shell（BSS）,a by-product from bamboo shoot processing industries,is a natural resource of cellulose. In this study,high-pressure homogenization assisted with acidolysis treatment was employed to produce ...Bamboo shoot shell（BSS）,a by-product from bamboo shoot processing industries,is a natural resource of cellulose. In this study,high-pressure homogenization assisted with acidolysis treatment was employed to produce BSS cellulose nanofiber（CNF）,and the structure was characterized by powder X-ray diffraction（XRD）,Fourier-transform infrared（FT-IR） spectroscopy,atomic force microscopy（AFM）,high resolution transmission electron microscopy（HTTEM）,thermogravimetric analysis（TGA）,and ^13 C nuclear magnetic resonance（NMR）. Moreover,the structure and properties of CNF were compared with those of BSS insoluble dietary fiber（IDF）. The results showed that CNF was in the form of a grid-like micro fiber,and its particle size was obviously reduced,while the crystallinity,thermal stability and solubility were increased. The results indicated that high-pressure homogenization assisted with acidolysis treatment was an effective method to prepare the BSS CNF,which could be a promising biopolymer reinforced material.展开更多
New descriptors were constructed and structures of some oxygen-containing organic compounds were parameterized. The multiple linear regression（MLR） and partial least squares regression（PLS） methods were employed t...New descriptors were constructed and structures of some oxygen-containing organic compounds were parameterized. The multiple linear regression（MLR） and partial least squares regression（PLS） methods were employed to build two relationship models between the structures and octanol/water partition coefficients（LogP） of the compounds. The modeling correlation coefficients（R） were 0.976 and 0.922, and the ＂leave one out＂ cross validation correlation coefficients（R（CV）） were 0.973 and 0.909, respectively. The results showed that the structural descriptors could well characterize the molecular structures of the compounds; the stability and predictive power of the models were good.展开更多
The recent developments in the photoinitiated cross-linking of polyethylene and the significant breakthrough of its industrial application are reviewed. The enhanced photo-initiation system, the dynamics of photoiniti...The recent developments in the photoinitiated cross-linking of polyethylene and the significant breakthrough of its industrial application are reviewed. The enhanced photo-initiation system, the dynamics of photoinitiated crosslinking, the optimum conditions, the crystal morphological structures and related properties, and the photo- and thermo-oxidation stability of photocrosslinked polyethylene (XLPE) materials have been elucidated systematically. A new technique for producing photocrosslinked XLPE-insulated wire and cable is described in detail. It can be expected that the future applications of photocrosslinking technique of polyolefins will be very promising.展开更多
A novel high performance MgCl2/TiCl4 catalyst with tetrabutyloxsilicane as electron donor was pre-pared for ethylene slurry polymerization process. The properties of the catalyst such as particle size distribution, ca...A novel high performance MgCl2/TiCl4 catalyst with tetrabutyloxsilicane as electron donor was pre-pared for ethylene slurry polymerization process. The properties of the catalyst such as particle size distribution, catalytic activity, hydrogen responsibility and copolymerization performance were investigated and compared with commercial catalyst (imported catalyst). Copolymerization of ethylene and 1-butylene using the catalyst was stud-ied in a pilot plant. The composition, structure and property of the copolymer were characterized by 13C nuclear magnetic resonance (13C NMR) and gel permeation chromatography-Infrared (GPC-IR), and compared with those of the copolymer obtained from a commercial catalyst. In comparison with the commercial catalyst, the novel cata-lyst had a higher activity (up to 34.6 kg·g-1) and a better particle size distribution (PSD), and produced polymers having higher bulk density (up to 0.37 g·cm-3) with less fine resin. Meanwhile, the novel catalyst showed a higher hydrogen responsibility and better copolymerization performance. The results indicated that the copolymer obtained from the novel catalyst has a higher branch in the high molecular weight fraction and lower branch in the low mo-lecular weight fraction.展开更多
文摘Bulk metallic glasses with up to 72 mm critical section thickness have been obtained by conventional casting techniques and the properties of these materials, particularly the mechanical and magnetic properties have been studied. These materials have been demonstrated to have novel properties which are fundamentally different from their crystalline counterparts. The recent status of research and development in formation, structure and properties of bulk metallic glasses is reviewed. The techniques to produce such bulk glasses are summarized and the glass forming ability and the critical cooling rate of these materials are discussed. Further consideration of the development and application of this new class of materiaIs will be proposed.
基金Project sponsored by the National Natural Science Foundation of China.
文摘The polybutylaldehyde obtained by plasma polymerization was investigated by means of IR, X-ray diffraction, GC-MS, elementary analysis, TEM, electron diffraction and contact angle measurements etc. The results showed that the polymer formed in plasma is amorphous crosslinked polymer, and its backbone is made of carbon atoms. The surface energy of the polymer film is independent of the polymerization conditions. No addition reaction has taken place in the carbonyl group of butylaldehyde in the plasma condition. The result of the wettability measurements showed that the polymer film is generally hydrophobic and the surface energy of the film is about 41 dyn/cm, in which the dispersion force contribution is the majority. The electron diffraction proved that some crystal substance, even the single crystals were present in the polymer. X-ray diffraction also proved the presence of crystal and showed about 15% crystaUinity fraction.
文摘Conductive polymer composites based on crystalline polymer matrix have been prepared by using an in-situ polymerization process of pyrrole in amorphous poly （ethylene terephthalate） （PET） film. The DSC and WAXD measurement and SEM observation show that liquid-induced crystallization of PET matrix has occurred during the preparation of composite films. Depending upon the equilibrium degree of swelling and crystallinity, the limited depth of penetration of pyrrole molecules results in a skin-core structure of the composite film. The skin layer containing charge transfer intercalated polypyrrole has a surface resistance of 3.5×10;Ω. Rigid and heat-resistant polypyrrole molecules formed in PET film increase the tensile modulus and, especially, the rigidity of PET at elevated temperatures. However, they decrease the tensile strength and elongation at break, and impair the thermal ductility of PET.
文摘A cobalt complex with mixed valence state [Co( Ⅰ ) (dppe)2CO]2 [Co2 ( Ⅱ )(dppe) Cl]6O2] (dppe = 1,2 - bis(diphenylphosphino) ethane) has been prepared. The compound crystallizes in triclinic space group P1 with unit cell parameters: a=1. 1763(3) nm, b = 1. 2943(6) nm, c=2. 1507(9) nm, a=81. 44(4)°? ,β=82. 58(3)°, r = 79. 82(3)°, V = 3. 1691 nm3 and Z=1. The structure was solved by direct method according to ALPHA criterion and was refined by a block diagonal matrix least-squares procedure to final R= 0.084, Moreover, infared spectra, electronic reflection spectra and cyclic voltammetry curve were mearsured.
文摘The synthesis,crystal structure and properties of the first Mn(III)-disulfide complex(Et_4N)[Mn(mp-mp)_2]were reported with the Mn(III) ion in a S_2O_4 octahedron distorted due to Jahn-Teller effect.Spectroscopic data revealed its paramagnetic properties.
基金The authors gratefully acknowledge the financial support of this work by National Natural Science Foundation of China(51773139,51922071).
文摘The future intelligent era that will be brought about by 5G technology can be well predicted.For example,the connection between humans and smart wearable devices will become increasingly more intimate.Flexible wearable pressure sensors have received much attention as a part of this process.Nevertheless,there is a lack of complete and detailed discussion on the recent research status of capacitive pressure sensors composed of polymer composites.Therefore,this article will mainly discuss the key concepts,preparation methods and main performance of flexible wearable capacitive sensors.The concept of a processing“toolbox”is used to review the developmental status of the dielectric layer as revealed in highly cited literature from the past five years.The preparation methods are categorized into types of processing:primary and secondary.Using these categories,the preparation methods and structure of the dielectric layer are discussed.Their influence on the final capacitive sensing behavior is also addressed.Recent developments in the electrode layer are also systematically reviewed.Finally,the results of the above discussion are summarized and future development trends are discussed.
文摘The optical properties of substituted fluorenones with diverse structures have been analyzed using molecular orbital calculations in order to understand the structure-property relations. Based on theoretical predictions, synthesis of some model compounds has been attempted. The experimentally obtained optical properties are in close agreement with the theoretically obtained results.
基金supported by the National Natural Science Foundation of China (Grant Nos 10647006 and 10547007)the Natural Science Foundation of Gansu Province of China (Grant No 3ZS042-B25-023)the Prominent Youth Foundation (Grant No Q200704) of LUT and the Scientific Developmental Foundation of LUT
文摘The geometries, electronic structures and related properties of SimN8-m（0 〈 m 〈 8） clusters are studied using density functional theory （DFT） with hybrid functional B3LYP. The calculated results reveal several trends. For any stoichiometric clusters, the lowest energy isomers with an alteration of N and Si atoms are favourable in energy if the numbers of Si and N atoms are large enough to form ... Si N-Si-N... alternative chains. The bond lengths of single Si-N bonds are very close to the corresponding values of the bulk and other SiN clusters. The geometries for N-rich and Si4N4 clusters are planar structures, but three-dimensional structures are favourable in energy for Si-rich clusters. With the increase of m, the isotropic polarizability and average polarizability increase, the total binding energies generally decrease, the HOMO-LUMO gap and vertical ionization potential oscillate with increasing number of valence electrons, and their values with even valence electrons are larger than those with odd valence electrons. The atomic charges, IR and Raman properties are also reported.
文摘A new imidazolate bridged Cu^(2+),Zn^(2+)binuclear complex[(dtma) CulmZn (dtma)]ClO_4· 2.5H_2O taken as active site model for Cu,Zn-SOD has been synthesized and its crystal structure determined.All the bond lengths, bond angles and the distance between Cu and Zn atoms in Cu-Im- Zn core of the model complex are close to those in Cu,Zn-SOD.ESR parameters of the model complex as a function of pH show that the imidazolate bridge is stable in pH range 10—12,and is broken on Zn side at pH～9.With decreasing pH,the imidazole is released at pH～4 and the dtma ligand dissociates from the Cu containing fragment at pH～2.4.
基金Commission of Science and Technology of Province Liaoning !(No.962154).
文摘In this article, the quenched Nd_4.5Fe_75Co_1Si_l B_18.5 ribbons were prepared, and the structures and properties were investigated. The results show that the change of structures of Nd_4.5 Fe_75 Co_1 Si_1 B_18.5 quenched amorphous ribbons is Am→Am'+Fe_3B+Nd_2Fe_23B_3+Nd_2Fe_14B→Nd_2- Fe_14B when it is heated. The effect of crystallizing treatment temperature and time on the magnetic properties of the quenched alloy was studied. The magnetic properties of 16 m/s quenched ribbons for 710℃×1200 s crystallizing treatment reach _iH_c=238.6 hA/m, B_r=0.8987 T and (BH)max=51.39 kJ/m^3. The grain size is about DFe3=32 nm and DNd2Fe14B=22 nm.
文摘Structures and properties of the blends of thermotropic liquid crystallinepolymer(LC70)and poly(ethylene terephthalate) (PET) were investigated by usingWAXD,DSC,SEM and mechanical test.The results revealed that Wc,x markdly decreased withLC70/PET>30%,and at about LC70/PET=10%, this blend can yield better mechanicalproperties.In these blends LC70 can play the role of the nuclear agent for PET.SEMphoto showed that LC70/PET in in-situ composites possessed 'core-shell' structure andwas immiscible, but at LC70/PST=10%, the LC70 can be uniformly dispersed into matrix PET.
基金financially supported by the National Key Research and Development Program of China(No.2022YFB3603105)Key Programs of the Chinese Academy of Sciences(No.ZDRW-CN-2023-3-2)+1 种基金the National Natural Science Foundation of China(No.51803221)Natural Science Foundation of Beijing Municipality(No.2202068)。
文摘The traditional high-temperature preparation process of polyimide can cause many problems and limits the wider application in extreme conditions.An important challenge to be solved urgently is the reduction of imidization temperature.In this work,twelve kinds of polyimide films with different chain rigidity were prepared at low temperature of 200℃,in the absence or presence of imidazole used as the catalyst.The molecular rigidity and free volume were theoretically calculated,and relationship between structure and properties were systematically studied.The results show that imidization reaction under low temperatures is significantly affected by the rigidity of molecula r chains.The rigid structure of polyimide is not conducive to the low-temperature imidization,but this adverse effect can be eliminated by adding catalyst,resulting the notably increased imidization degree.The optical and thermal properties can be improved to a certain extent for the chemically catalyzed system,resulting in relatively higher heat resistance and thermal stability.While the mechanical performance could be determined by com plicating factors,greatly different from polyimide films prepa red by high temperature method.To investigate aggregation structures of film s,the effect of chain rigidity and catalyst on the stacking or orientation of molecular chains was further elaborated.This wo rk can contribute to the understanding of chemically catalyzed imidization that is rarely reported in the existing research,and will provide guidance for the low-temperature preparation of high-performance polyimides.
文摘Conducting nanocomposites of poly （methyl methacrylate） （PMMA） and antimony doped tin oxide （ATO） were prepared by solution blending. The influences of ATO content on the electrical conductivity, thermal stability, and mechanical properties of the nanocomposites were investigated. A homogeneous dispersion of silane coupling agent modified ATO was achieved in PMMA matrix as evidenced by scanning electron microscopy. The resultant PMMA/silane-ATO nanocomposites were electrically conductive with significant conductivity enhancement at 4 wt pct. It was found that the composition at 4 wt pct ATO gave the higher tensile strength. Furthermore, it gave the largest elongation at break value among all the compositions. Thermal stability of the nanocomposites was remarkably enhanced by the incorporation of silane-ATO.
文摘Direct current metal filtered cathodic vacuum arc （FCVA） and acetylene gas （C2H2） were wielded to synthesize Ti-containing amorphous carbon films on Si （100）. The influence of substrate bias voltage and acetylene gas on the microstructure and mechanical properties of the films were investigated. The results show that the phase of TiC in the （111） preferential crystallographic orientation exists in the film,and the main existing pattern of carbon is sp2. With increasing the acetylene flow rate,the contents of Ti and TiC phase of the film gradually reduce; however,the thickness of the film increases. When the substrate bias voltage reaches -600 V,the internal stress of the film reaches 1.6 GPa. The micro-hardness and elastic modulus of the film can reach 33.9 and 237.6 GPa,respectively,and the friction coefficient of the film is 0.25.
基金Aeronautical Science Foundation of China (03G51069)Items of Engineering Research Institute, Peking University (ERIPKU-204031)
文摘The TiO2-Co-TiO2 sandwich films were successfully grown on glass and silicon substrata making alternate use of radio frequency reactive magnetron sputtering and direct current magnetron sputtering. The structures and properties of these films were identified with X-ray diffraction （XRD）, Raman spectra and X-ray photoemission spectra （XPS）. It is shown that the sandwich film consists of two anatase TiO2 films with an embedded Co nano-film. The fact that, when the Co nano-film thickens, varied red shifts appear in optical absorption spectra may well be explained by the quantum confinement and tunnel effects. As for magnetic properties, the saturation magnetization, remnant magnetic induction and coercivity vary with the thickness of the Co nano-films. Moreover, the Co nano-film has a critical thickness of about 8.6 mn, which makes the coercivity of the composite film reach the maximum of about 1413 Oe.
文摘The equilibrium geometries and electronic properties of CumSin （2 ≤m ＋ n ≤ 7） clusters have been studied by using density functional theory at the B3LYP/6-311＋G （d） level. Our results indicate that the structure of CuSin （n 〈6） keeps the frame of the corresponding Sin cluster unchanged, while for CunSi clusters, the rectangular pyramid structure of Cu4Si is shown to be a building block in many structures of larger CunSi clusters. The growth patterns of CumSin clusters become more complicated as the number of Cu atoms increases. Both the binding energies and the fragmentation energies indicate that the Si-Si bond is stronger than the Cu-Si bond, and the latter is stronger than the Cu-Cu bond. Combining the fragmentation energies in the process CumSin →Cu＋Cum-l Sin and the second-order difference △2E（m） against the number of Cu atoms of CumSin, we conclude that CumSin clusters with even number of Cu atoms have higher stabilities than those with odd rn. According to frontier orbital analyses, there exists a mixed ionic and covalent bonding picture between Cu and Si atoms, and the Cud orbitals contribute little to the Cu-Si bonding. For a certain cluster size （m ＋ n = 3, 4, 5, 6, 7）, the energy gaps of the most stable CumSin clusters show odd-even oscillation with changing m, the clusters with odd m exhibit stronger chemical reactivity than those with even m.
文摘Bamboo shoot shell（BSS）,a by-product from bamboo shoot processing industries,is a natural resource of cellulose. In this study,high-pressure homogenization assisted with acidolysis treatment was employed to produce BSS cellulose nanofiber（CNF）,and the structure was characterized by powder X-ray diffraction（XRD）,Fourier-transform infrared（FT-IR） spectroscopy,atomic force microscopy（AFM）,high resolution transmission electron microscopy（HTTEM）,thermogravimetric analysis（TGA）,and ^13 C nuclear magnetic resonance（NMR）. Moreover,the structure and properties of CNF were compared with those of BSS insoluble dietary fiber（IDF）. The results showed that CNF was in the form of a grid-like micro fiber,and its particle size was obviously reduced,while the crystallinity,thermal stability and solubility were increased. The results indicated that high-pressure homogenization assisted with acidolysis treatment was an effective method to prepare the BSS CNF,which could be a promising biopolymer reinforced material.
基金supported by the Youth Foundation of Education Bureau,Sichuan Province(13ZB0003)
文摘New descriptors were constructed and structures of some oxygen-containing organic compounds were parameterized. The multiple linear regression（MLR） and partial least squares regression（PLS） methods were employed to build two relationship models between the structures and octanol/water partition coefficients（LogP） of the compounds. The modeling correlation coefficients（R） were 0.976 and 0.922, and the ＂leave one out＂ cross validation correlation coefficients（R（CV）） were 0.973 and 0.909, respectively. The results showed that the structural descriptors could well characterize the molecular structures of the compounds; the stability and predictive power of the models were good.
基金The project was successively supported by the National Natural Science Foundation of China(No. 5880104, No. 59543002 and No. 59773030).
文摘The recent developments in the photoinitiated cross-linking of polyethylene and the significant breakthrough of its industrial application are reviewed. The enhanced photo-initiation system, the dynamics of photoinitiated crosslinking, the optimum conditions, the crystal morphological structures and related properties, and the photo- and thermo-oxidation stability of photocrosslinked polyethylene (XLPE) materials have been elucidated systematically. A new technique for producing photocrosslinked XLPE-insulated wire and cable is described in detail. It can be expected that the future applications of photocrosslinking technique of polyolefins will be very promising.
文摘A novel high performance MgCl2/TiCl4 catalyst with tetrabutyloxsilicane as electron donor was pre-pared for ethylene slurry polymerization process. The properties of the catalyst such as particle size distribution, catalytic activity, hydrogen responsibility and copolymerization performance were investigated and compared with commercial catalyst (imported catalyst). Copolymerization of ethylene and 1-butylene using the catalyst was stud-ied in a pilot plant. The composition, structure and property of the copolymer were characterized by 13C nuclear magnetic resonance (13C NMR) and gel permeation chromatography-Infrared (GPC-IR), and compared with those of the copolymer obtained from a commercial catalyst. In comparison with the commercial catalyst, the novel cata-lyst had a higher activity (up to 34.6 kg·g-1) and a better particle size distribution (PSD), and produced polymers having higher bulk density (up to 0.37 g·cm-3) with less fine resin. Meanwhile, the novel catalyst showed a higher hydrogen responsibility and better copolymerization performance. The results indicated that the copolymer obtained from the novel catalyst has a higher branch in the high molecular weight fraction and lower branch in the low mo-lecular weight fraction.
