Microstructure and mechanical properties of poly (vinyl chloride) modified by silica fume / acrylic core-shell impact modifier blends

This research explored replacing acrylic core-shell impact modifier (AIM) by silica fume to toughen PVC. 100%, 75%, 50% and 25% of AIM (8 phr) were substituted by silica fume in PVC respectively, and then processed by dry blending and twin-screw extrusion. Severe silica fume agglomeration was observed by scanning electron microscope (SEM) in the PVC matrix when 8 phr pure silica fume was used and processed by screw speed of 20 rpm. Its tensile strength was thereby reduced by 38% comparing to unmodified PVC. The silica fume was successfully dispersed while the screw speed was slowed down to 10 rpm to give a stronger screw torque and a longer melt residential time in the extruder. The tensile strength was ’recovered’ to a level comparable to unmodified PVC. Impact test were performed on all formulations extruded at 10 rpm screw speed and synergetic toughening effect was found with 50% substitution and it had the impact strength that was comparable to 8 phr pure AIM toughened PVC.     

Effect of B2O3 on the Structure and Photoluminescence Properties of Sol-gel Glass Doped with Terbium Organic Complex

Both silica and boron-silica glass materials doped with terbium organic complex were prepared by in situ sol-gel method respectively. XRD and SEM measurements were performed to verify the non-crystalline structure of the glass. The influence of the glass contents on the structure of the glass and the erwrgy level of the doped Tb （Ⅲ） ions was analyzed by the emission spectra and IR spectra. The effect of B2O3 on the photolumirwscence properties of rare earth organic complex in silica- based glass was investigated. The IR spectra indicate that the in situ sylthesized rare earth complex molecule was confined to the micropores of the bost and the vibration of the ligands was frozen. When B2O3 was added into the silica host gel, B2O3 had little influence on the noncrystallirw structure of the glass, and BO3 triangle, which had a layer structure different from the silica framework, could form. So the silica network became more inhomogenous, and the luminescence of terbium complexes was quenched with the increase of the B2O23 amount.     

Synthesis,structure, DNA binding and cleavage activity of a new copper(II) complex of bispyridylpyrrolide

A copper-bispyridylpyrrolide complex [Cu(PDPH)Cl](PDPH = 2,5-bis(2′-pyridyl)pyrrole) was synthesized and characterized. The complex crystallizes in the orthorhombic system with space group Pccn, a = 0.9016(3) nm, b = 1.0931(4) nm, c =2.5319(8) nm, and V = 2.4951(15) nm3. The copper center is situated in a square planar geometry. The interaction of the copper(II)complex with calf thymus DNA(CT-DNA) was investigated by electronic absorption, circular dichroism(CD) and fluorescence spectra. It is proposed that the complex binds to CT-DNA through groove binding mode. Nuclease activity of the complex was also studied by gel electrophoresis method. The complex can efficiently cleave supercoiled p BR322 DNA in the presence of ascorbate(H2A) via oxidative pathway. The preliminary mechanism of DNA cleavage by the complex with different inhibiting reagents indicates that the hydroxyl radicals were involved as the active species in the DNA cleavage process.     

Syntheses and applications of Eu（Ⅲ） complexes of 2-thienyltrifluoroacetonate, terephthalic acid and phenanthroline as light conversion agents

A series of europium(Ⅲ) complexes of 2-thienyltrifluoroacetonate (HTTA), terephthalic acid (TPA) and phenanthroline (Phen) were synthesized. The new complexes Eu(TPA)(TTA)Phen and Eu2(TPA)(TTA)4Phen2 were characterized by elemental analysis, IR spectrum, scanning electron microscope and thermal stability analysis. The results show that the thermal stability of the Eu( Ⅲ ) complexes increases in the following order: the mononuclear complex Eu(TTA)3Phen, the binuclear complex Eu2(TPA)(TTA)4Phen2, the chain polynuclear complex Eu(TPA)(TTA)Phen. And the formation of the binuclear/polynuclear structure of the new complexes appears to be responsible for the enhancement of their thermal and optical stability. In addition, The fluorescence excitation spectra of these new complexes show more broad excitation bands than that of the complex Eu(TTA)3Phen corresponding to their formation. The enhancement of Eu3 fluorescence in the new complexes can be observed by the addition of Gd3 . The bright red luminescent plastics can be obtained when the complex EuGd(TPA)(TTA)4Phen2 is added above 0.5% (mass fraction).     

The Setting Chemistry of Glass Ionomer Cement

The setting chemistry of glass ionomer cement was imestigated by using mechanical determination of compressive strength at predetermined intervals,and measurement of structure changes of correspondling fracture sample by means of IR spectra and differential scanning calorimetry（DSC）.Zinc polycarboxylate cement was used as a comparison sample.The compressive strength of glass ionomer cement（GIC） increases with aging.IR spectra and DSC of corresponding fracture sample show the structure changes of the matrix and interface layer comprising of silica gel during the predetermined intervals studied.however,no significant changes occur in the zinc polycarxyolate cement.Hence the structure changes of the matrix and/or interface layer are responsible for compressive strength increasing with aging.The structure changes include the crosslink density,the ratio of complex form to ionic form,the content ratio of Al-PAA to Ca-PAA,the forming and maturing process of the interface layer comprising of silica gel.     

Rheological behavior of novel polyamide 6/silica nanocomposites containing epoxy resins

A novel polyamide 6/silica nanocomposite containing epoxy resins(EPA6N) was prepared via in situ polymerization using tetraethoxysilane(TEOS) as the precursor of silica.The dynamic rheological properties of pure PA6 and EPA6N at temperatures of 225 and 235 ℃ were investigated.The results of transmission electron microscopy(TEM) and atomic force microscopy(AFM) indicate that the silica particles are well dispersed in the polyamide 6 matrix on about 30 nm in diameter,which demonstrates that this method can effectively avoid agglomeration of the inorganic particles.The rheological results suggest that pure PA6 shows Newtonian behavior.However,the novel EPA6N exhibits a solid-like rheological behavior,which is due to the small size,large surface of silica particles and the stronger polyamide 6-silica chemical bond formed through the reactions of epoxy resins with end groups of PA6 molecular chains.The EPA6N also exhibits higher melt viscosity,storage modulus and loss modulus than those of pure PA6.     

Fluorescence properties and application of doping complexes Eu1-xLx (TTA)3Phen as light conversion agents

Light conversion agents Eu1-x Lx (TTA)3 Phen (L denotes La3+ , Gd3+ , Y3+ ) complexes were prepared,and the influence of doping ions on fluorescence properties was investigated by elementary analysis, FTIR and fluorescent spectra. The results show that FTIR spectra of Eu1_x Lx (TTA)3 Phen complex system are identical with that of EuTTA3 Phen, which indicates that the complexes Eu1 xLx(TTA)3Phen are similar in structure to Eu (TTA)3Phen. For the above doping elements, co-fluorescence enhancement has the following order: Gd3+ ＞Y3+ ＞La3+ , and the optimum mole fractions of doping elements are 0.4, 0.2 and 0.5 respectively for Gd3+ , Y3+ ,La3+. Among all the complexes, Eu0.6 Gd0.4 (TTA)3 Phen complex has the strongest fluorescent intensity. Applying Eu0.6 Gd0.4 (TTA)3 Phen complex to plastic and printing inks, bright red fluorescence plastic and printing inks are obtained when the content of europium reaches 0.1% (mass fraction).     

Determination of volatile components in cut tobacco with gas chromatography-mass spectrometry and chemometric resolution

Chromatography-mass spectrometry(GC-MS)was used to analyze the volatile components of cut tobacco samples with the help of heuristic evolving latent projections(HELP).After extracting with simultaneous distillation and extraction method,the volatile components in cut tobacco were detected by GC-MS.Then the obtained original two-dimensional data were resolved into pure mass spectra and chromatograms.The qualitative analysis was performed by similarity searches in the national institute of standards and technology(NIST)mass database with the obtained pure mass spectrum of each component and the quantitative results were obtained by calculating the volume of total two-way response.The accuracy of qualitative and quantitative results were greatly improved by using the two-dimensional comprehensive information of chromatograms and mass spectra.107 of 141 separated constituents in the total ion chromatogram of the volatile components were identified and quantified,accounting for about 88.01% of the total content.The result proves that the developed method is powerful for the analysis of complex cut tobacco samples.     

Fabrication of copper (Ⅰ) nitride nanorods within SBA-15 by metal organic chemical vapor deposition

Copper (Ⅰ) nitride nanorods grown in channels of mesoporous silica SBA-15 by chemical vapor deposition method has been synthesized. The morphology and microstructure of the resulting product were characterized by XRD patters, TEM images, EDS analysis and Raman spectra. The XRD and TEM revealed that the Cu3N phase was confined in channels of SBA-15 forming continuous nanowires with 6 nm around and hundreds of nanometers in length. Raman spectra of the final product and pure Cu3N showed peaks shift due to the quantum confinement effect of the nanowires. This preparation methodology only requires a mild working condition and is capable of template synthesis of other binary nitride nanostructures with controlled morphology inside the channels of mesoporous materials.     

Processing and performance of 2D fused-silica fiber reinforced porous Si_3N_4 matrix composites

Two-dimension(2D)fused-silica fiber reinforced porous silicon nitride matrix composites were fabricated using slurry impregnation and cyclic infiltration with colloidal silica sol.The microstructure and fracture surface were characterized by SEM,the mechanical behavior was investigated by three-point bending test,and the dielectric constant was also measured by impedance analy- sis.The microstructure showed that the fiber and the matrix had a physical bonding,forming a clearance interface.The mechanical behavior suggested that the porous matrix acted as crack deflection,and the fracture surface had a lot of fiber pull-out.However,the interlaminar shear strength was not so good.The dielectric constant of the composites at room temperature was about 2.8-3.1.The relatively low dielectric constant and non-catastrophic failure indicated the potential application in the radome materials field.     

Preparation of BN／SiO2 ceramics by PIP method

The precursor infiltration and pyrolysis(PIP) method for preparation of BN/SiO2 composites was used to improve mechanical properties, dielectric properties and feasibility of high temperature dielectric parts with large dimensions and complex shapes. In the processing procedure, the porous BN ceramic matrix was first successfully prepared by compacting the mixed powders of B and BN and then sintering them at a certain temperature under normal pressure of N2. The polycarbosilane(PCS) solution was vacuum infiltrated into porous BN ceramics at the room temperature and then at 800℃ in the air to depolimerize out amorphous SiO2, and sintered further at 1 300℃ in N2 to get BN/SiO2 composites. The microstructure of materials was studied by means of X-ray diffraction and electron probe micro analysis. The thermo-decomposition mechanism of PCS was investigated by a TG-DTA and infrared (IR) spectrum analysis. The flexural strengths were measured by the three-point bending method. The dielectric constant and the loss tangent were measured by the wave-guide method. The results show BN/SiO2 composites were fabricated. The obtained composites posses a flexural strength of 61.96 - 93.31 MPa, the dielectric constant in the range of 3.50 - 3.78 and the order of magnitude of the loss tangent at 10^-3 , which are good for the high tempera turedielectric parts with large size and complex shapes.     

Effects of silica aerogel content on microstructural and mechanical properties of poly(methyl methacrylate)/silica aerogel dual-scale cellular foams processed in supercritical carbon dioxide

A novel poly(methyl-methacrylate)/silica aerogel(PMMA/SA) dual-scale cellular foam was synthesized with internal mixing followed by the supercritical carbon dioxide foaming process.The effects of silica aerogel content on the microstructural and mechanical performance of the foams were investigated by SEM,TEM analysis,and mechanical tests.The experimental results suggest that the employment of silica aerogel granule as addictive can distinctly improve the morphological feature as well as the mechanical performance in comparison to neat PMMA foam by uniformizing cell size distribution,decreasing cell size and increasing cell density.And dual-scale cells including micrometric cells of 3-10 μm and nanometric cells of about 50 nm existed in the structure of foams resulting from the retained original framework structure of silica aerogel,which has not been described in other studies with the addition of various fillers.Furthermore,the mechanical strength was significantly elevated even with a small amount of silica aerogel resulting from the unique microstructure,decreased cell size and enhanced cell walls.The compressive strength was 18.12 MPa and the flexural strength was 18.90 MPa by adding 5wt% and 2wt% silica aerogel,respectively.These results demonstrate the potential to synthesize PMMA/SA dual-scale cellular foams to be used as structural materials with the advantages of low density and high strength.     

Sol-gel-derived hybrid conductive films for electromagnetic interference (EMI) shielding

The conductive nano-sized zinc particles were embedded in an insulating amorphous silica matrix,and the hybrid films were obtained by a sol-gel method.The stable hybrid sol solution was prepared by hydrolysis and condensation of Methyltrimethoxysilane (MTMS) with a one-step acidic catalyst process.Hybrid films were dip-coated on silicon wafer and cured at 120℃ for 60minutes.The structural characterization of hybrid films were investigated by means of attenuated total reflection infrared (ATR-IR) spectroscop...     

Effect of low temperature on hydration performance of the complex binder of silica fume-portland cement

By analyzing the mechanical properties, composition of hydrates, content of Ca(OH)2 and microstructure of the complex binder of silica fume-Portland cement, which cured at constant low temperatures (+5--10 ℃), the effect of different low temperatures on hydration performance of the complex binder at the age of 3, 7 days and 14 days was researched. Experimental results show that hydration processes of the complex binder can be restricted by low temperature. Reducing the curing temperature could cause compressive strength and flexural strength of the complex binder to decrease significantly. The gradient difference between strength diminishes, content of Ca(OH)2 in hydrates reduces, and compactness of the microstructure weakens. Therefore mixing with silica fume can modify various performance indicators of the complex blinder, but reducing the curing temperature restricts the pozzolanic activity of silicon fume.     

Characterization of band sawing dusts generated in cutting of multi-crystalline silicon ingots

Physical-chemical characteristics of the band sawing dusts regarding to recovery of pure silicon from them were investigated.The experimental results show 50vol%-60vol% amorphous phases exist in the dusts,which is mostly amorphous silica.The as-received saw dusts are found to form hard agglomerates of larger than 50 microns in diameter.The iron-based inclusions collected by magnets are found to match well with the band saw material in XRD patterns.Weight loss in heating was observed by thermal gravity tests,up to 900 ℃,presumably due to reaction of the amorphous silica with carbon contaminant in the dusts.The saw dusts were variously treated to examine their physical-chemical responses,and the results were also presented.     

The micro-structural studies of Ni-BaTiO<Subscript>3</Subscript> nanocomposite films by TEM and EELS

Epitaxial BaTiO3 films with embedded metallic Ni nanocrystal (Ni-BaTiO3) were successfully fabricated on SrTiO3 (001) single-crystalline substrate through the laser molecular beam epitaxial (L-MBE) technique.High resolution transmission electron microscopy (HRTEM) and electron energy loss spectrum (EELS) with Kramers-Kronig analysis methods were employed to characterize the microstructures,elementary distribution and the electron structure of these films.HRTEM results suggested that the structure of BaTiO3 was tetragonal with lattice parameters of a=0.399 nm and c=0.403 nm.Energy dispersive X-Ray spectroscopy (EDX) confirmed metallic Ni nanocrystal embedded successfully in BaTiO3 epitaxial films.The Ni-BaTiO3 composite films were compound of the epitaxial BaTiO3 (110) layers alternating with Ni NCs array (111) layers.Furthermore,the existence of the misfit dislocations induced by the embedding of Ni nanoparticles was also clearly demonstrated by the HRTEM images.The Ni L2,3 edges of EELS revealed that Ni NCs in their metallic state were embedded uniformly in the BaTiO3 matrix.A chemical shift of about 7 eV regarding L3 edges in the Ni EELS was also observed.The optical band gap of BaTiO3 in these films was about 3.84 eV,higher than 3.55 eV for pure BaTiO3 films at room temperature.     

Enhanced dielectric permittivity of graphite oxide/polyimide composite films

Graphite oxide(GO) was prepared by the pressurized oxidation method and incorporated into polyimide(PI) matrix to fabricate high-k composite films by in-situ polymerization and subsequent thermal treatment. The results show that the as-prepared GO had good dispersion and compatibility in PI matrix due to the introduction of abundant oxygen-containing functional groups during the oxidation. The residual graphitic domains and the thermal treatment induced reduction of GO further enhanced the dielectric permittivity of the resulting GO–PI composites. The dielectric permittivity of the GO–PI composites exhibited a typical percolation behavior with a percolation threshold of 0.0347 of volume ratio and a critical exponent of 0.837. Near the percolation threshold, the dielectric permittivity of the GO–PI composite increased to 108 at 10~2 Hz and was 26 times that of the pure PI.     

Structrue and Characteristics of Mesoporous Silica Synthesized in Acid Medium and Its Reaction Mechanism

Structrue and pore characteristics of the mesoporous silica synthesized in acid medium were studied by means of XRD, HRTEM, BET, FT-IR, DSC-TGA, and the reaction mechanism was also investigated deeply. The results show that mesopores in the sample possess hexagonal arrays obviously, whereas the structure of silica matrix is amorphous. The results also show that the acting mode of silica and CTMA^ inside the mesopores was chemical bonding force. The structure of rnesoporous silica was mainly dependent on the aggregational condition of micelle of CTMA^ as well as their liquid- crystallized status. In addition, condensation and dehydration of silicate radicals were accompanied in the process of calcination, which resulted in the mesoporous structure ordered in local range and the pore sizes largening.     

Processing and performance of 2D fused-silica fiber reinforced porous Si3N4 matrix composites

Two-dimension （2D） fused-silica fiber reinforced porous silicon nitride matrix composites were fabricated using slurry impregnation and cyclic infiltration with colloidal silica sol. The microstructure and fracture surface were characterized by SEM, the mechanical behavior was investigated by three-point bending test, and the dielectric constant was also measured by impedance analysis. The microstructure showed that the fiber and the matrix had a physical bonding, forming a clearance interface. The mechanical behavior suggested that the porous matrix acted as crack deflection, and the fracture surface had a lot of fiber pull-out. However, the interlaminar shear strength was not so good. The dielectric constant of the composites at room temperature was about 2.8-3.1. The relatively low dielectric constant and non-catastrophic failure indicated the potential application in the radome materials field. 2008 University of Science and Technology Beijing. All rights reserved.     

Sensitization and intra-molecular energy transfer of Eu<Superscript>3+</Superscript> by Tb<Superscript>3+</Superscript> in Eu-Tb binuclear complexes/PMMA

A series of Eu0.5Tb0.5(TTA)3Phen/PMMA (TTA=thenoyltrifluoroacetone,Phen=phenanthroline) and Eu0.5Tb0.5(TTA)3Dipy/PMMA (Dipy=2,2’-dipyridyl) were prepared by in-situ polymerization.The structures of the composites were characterized by IR spectra and electron spectrum.Photoluminescence properties were investigated by UV-Vis spectra and fluorescence spectra.Meanwhile,the energy transfer models were set up.The results indicated that polymer parts were attached with the rare-earth molecular parts in the composi...