A novel microwave absorber — BaAl2Fe10O19/poly(m-toluidine) composite: Preparation and electromagnetic properties

BaFe10Al2O19 /poly(m-toluidine)(BFA/PMT) composites were synthesized by in-situ polymerization of m-toluidine in the presence of BaFe10Al2O19 particles.The structure,composition and morphology of the obtained samples were characterized by using XRD,FT-IR,UV-visible spectroscopy,SEM and TEM techniques.Their electrical conductivity,magnetic property and microwave absorbing property were measured by the four-probe meter,the vibrating sample magnetometer and the vector network analyzer,respectively.The results indicated that BFA particles were coated effectively by PMT polymer and some interactions between PMT and BFA particles existing in the composites.The conductivity of BFA/PMT composite is smaller than that of pure polymers and its saturation magnetization is a little smaller than that of pure BFA.The influence of the constitution and film thickness of absorbent on its microwave absorbing property is evident.The microwave absorbing properties of the BFA/PMT composites are better than those of pure BFA and PMT.When optimizing the mass rate of BFA/PMT to 0.3,the absorbent with 2 mm film thickness has the minimum reflection loss of 28.26 dB at approximate 14.24 GHz,and the maximum available bandwidth of 8.8 GHz,respectively.The results show that these composites can be used as advancing absorption and shielding materials due to their favorable microwave absorbing property.     

EFFECT 0F INTERFACIAL ADHESION ON CRYSTALLIZATION AND MECHANICAL PROPERTIES OF POLY (ETHYLENE TEREPHTHALATE)/GLASS BEAD COMPOSITES

The interfacial adhesion between poly (ethylene terephthalate) (PET) and glass beadwas investigated by scanning electron microscope and parallel-plate rheometer. Effect ofinterfacial adhesion on the crystallization and mechenical properties of PET/glass beadcomposites was also studied by differential scanning calorimeter and mechanical testers.The results obtained indicate that the glass bead has a heterogeneous nucleation effecton the PET crystallization. Although better interfacial adhesion is advantageous to theincrease of the tensile strength of the composite, yet it is unfavorable to the crystallizationof PET. It should be pointed out that the crystallization rate of filled PET is always higherthan that of pure PET, regardless of the state of interfacial adhesion.     

Crystallization behavior of polylactide on highly oriented polyethylene thin films

The crystalline structure and morphology of the PLA crystallized isothermally from the glassy state on highly oriented PE substrates at 130℃were investigated by means of optical microscopy,AFM and X-ray diffraction.The results indicate that the PE substrate influences the crystallization behavior of PLA remarkably,which leads to the growth of PLA crystals on PE substrate always in edge-on form rather than the twisted lamellar crystals from edge-on to flat-on when crystallizing the PLA on glass surface under the same condition.The edge-on PLA lamellae on the PE substrate are preferentially arranged with their long axes in the chain direction of the PE substrate crystals.It is further demonstrated that except for the different crystal orientation,the PE does not influence the crystalline modification and crystallinity of the PLA.     

Electrooxidation Mechanism of Methanol at Pt-Ru Catalyst Modified GC Electrode in Electrolytes with Different pH Using Electrochemical and SERS Techniques

The electrochemical and in-situ surface-enhanced Raman spectroscopy （SERS） techniques were used to investigate the electrooxidation behavior of methanol in acidic, neutral and alkaline media at a Pt-Ru nanoparticle modified glassy carbon （Pt-Ru/GC） electrode. The results showed that methanol could be dissociated spontaneously at the Pt-Ru/GC electrode to produce a strongly adsorbed intermediate, CO. It was found that CO could be oxidized more easily in the alkaline medium than in the acidic and neutral media. The peak potential of methanol oxidation was shifted from 0.663 and 0.708 V in the acidic and neutral media to -0.030 V in the alkaline medium, which is due to that the adsorption strength of CO on the Pt surface in the alkaline medium is weaker than that in the acidic and neutral media. The final product of the methanol oxidation is CO2. However, in the alkaline medium, CO2 produced would form CO3^2- and HCO3^- resulting in the decrease in the alkaline concentration and then in the decrease in the performance of DMFC. Therefore, the performance of the alkaline DMFC is not Stable.     

Electroactive shape memory cyanate/polybutadiene epoxy composites filled with carbon black

Electroactive shape memory composites were synthesized using polybutadiene epoxy(PBEP) and bisphenol A type cyanate ester(BACE) filled with different contents of carbon black(CB). Dynamic mechanical analysis(DMA), scanning electron microscopy(SEM), electrical performance and electroactive shape memory behavior were systematically investigated. It is found that the volume resistivity decreased due to excellent electrical conductivity of CB, in turn resulting in good electroactive shape memory properties. The content of CB and applied voltage had significant influence on electroactive shape memory effect of developed BACE/PBEP/CB composites. Shape recovery can be observed within a few seconds with the CB content of 5 wt% and voltage of 60 V. Shape recovery time decreased with increasing content of CB and voltage. The infrared thermometer revealed that the temperature rises above the glass transition temperature faster with the increase of voltage and the decrease of resistance.     

THERMAL BEHAVIOR OF THERMOTROPIC HYDROXYETHYL CELLULOSE ACETATE/POLYETHYLENE BLENDS

The thermal behavior of thermotropic hydroxythyl cellulose acetate (HECA)/polyethy-lene (PE) blends has been studied by DSC. It is found that the blends of HECA and PEare immiscible but the crystallization of PE is affected by HECA chains in the blends withmore than 50% HECA, which results in the subordinate crystallization of PE and the for-mation of imperfect structures in the PE crystals. The imperfection of PE crystals in theblends can be eliminated after annealing at 393K.     

Chemical Frequencymetry——Theory and Application

A new theory named "Chemical frequencymetry" is proposed. It is based on chemical reactions followed by piezoelectric monitoring. The frequency shift caused by the chemical reaction is related to the fundamental frequency (f) and overtone order (h) of the crystal, the formula weight (m) and diffusion coefficient (D) of the active chemical species, the diffusion layer thickness (δ), the response time(t), the concentration of the determinant (C_A) and the stoichiometric factor of the chemical reaction (k) according to the formulaThe technique has been applied to the determination of analgin as an example of its application.     

Hydrogen Bonds in Coal -The Influence of Coal Rank and the Recognition of a New Hydrogen Bond in Coal

By means of in-situ diffuse reflectance FTIR.The IR spectra of 6 coals with different ranks were obtained from room temperature to 230℃.A new curve fitting method was used to recognize the different hydrogen bonds in the coals.and the influence of coal ranks on the distribution of hydrogen bonds(HBs) in the coals and their thermal stability were discussed.The results show that there is another new HB(around 2514cm^-1) between the-SH in mercaptans or thiophenols and the nitrogen in the pyridine-like compounds in the coals.and the evidence for that was provided.The controversial band of the HB between hydroxyl and the nitrogen of the pyridine-like compounds was determined in the range of 3028-2984cm^-1,and the result is comsistent with but more specific than that of Painter et al.It was ound that the stability of different HBs in the coals is influenced by both coal rank and temperature,For some HBs.the higher the coal rank,the higher the stability of them.Within the temperature range of our research,the stability of the HB between the hydroxyl and the π bond increases to some extent for some coals at temperatures higher than 110 or 140℃.     

IN-SITU AFM OF POLYMER CRYSTALLIZATION

Atomic force microscopy images taken during the crystallization of polyethylene both from processed andquiescent melts are presented. Crystallization from processed melts provides further evidence of a region in front of agrowing lamella that is influenced by the crystallization process, but extending only 40 nm into the melt. High-resolutionimages of the growing crystal tip, taken during crystallization, show no direct evidence of the existence of intermediatephases. The growing tip is shown to be slightly rounded. In-filling crystallization, occurring after the initial flush of growth,is imaged in polyethylene for the first time, and shown to continue to a temperature 8℃ below the initial crystallizationtemperature.     

IN SITU OBSERVATION OF MELTING AND CRYSTALLIZATION BEHAVIORS OF POLY(ε-CAPROLACTONE) ULTRA-THIN FILMS BY AFM TECHNIQUE

The melting and crystallization behaviors of poly(ε-caprolactone) (PCL) ultra-thin films with thickness from 15 nm to 8 nm were studied by AFM technique equipped with a hot-stage in real-time. It was found that melting can erase the spherulitic structure for polymer film with high thickness. However, annealing above the melting point can not completely erase the tree-like structure for the thinner polymer film. Generally, the structure formation of thin polymer films of PCL is controlled not only by melting and crystallization but also by dewetting during thermal annealing procedures, and dewetting predominates in the structure formation of ultra-thin films. However, the presence of tree-like morphology at 75 °C may be due to the strong interaction between PCL and mica surface, which may stick the PCL chains onto the mica surface during thermal annealing process. Moreover, the growth of the dendrites was investigated and it was found that crystallization is followed from a dewetted sample, and the branches did not grow with the stems. The crystallization of polymer in the ultra-thin films is a diffusion-controlled process. Both melting and crystallization behaviors of PCL in thin films are influenced by film thickness.     

REMOVAL OF MERCURY FROM WATER USING POLYPYRROLE AND ITS COMPOSITES

One of the suitable methods for removing heavy metals from water is by using surface adsorption process. In this paper, the preparation of polypyrrole and its composites as adsorbents are discussed and the capability of separating mercury from water is investigated. The results indicated that the polypyrrole and its composites are able to remove mercury from aqueous media. Furthermore the adsorption percentage is related to the surface morphology, type of additives and its concentration.     

LiCoO_2 electrode/electrolyte interface of Li-ion batteries investigated by electrochemical impedance spectroscopy

The storage behavior and the first delithiation of LiCoO2 electrode in 1 mol/L LiPF6-EC:DMC:DEC elec- trolyte were investigated by electrochemical impedance spectroscopy (EIS). It has found that, along with the increase of storage time, the thickness of SEI film increases, and some organic carbonate lithium compounds are formed due to spontaneous reactions occurring between the LiCoO2 electrode and the electrolyte. When electrode potential is changed from 3.8 to 3.95 V, the reversible breakdown of the resistive SEI film occurs, which is attributed to the reversible dissolution of the SEI film component. With the increase of electrode potential, the thickness of SEI film increases rapidly above 4.2 V, due to overcharge reactions. The inductive loop observed in impedance spectra of the LiCoO2 electrode in Li/LiCoO2 cells is attributed to the formation of a Li1-xCoO2/LiCoO2 concentration cell. Moreover, it has been demonstrated that the lithium-ion insertion-deinsertion in LiCoO2 hosts can be well described by both Langmuir and Frumkin insertion isotherms, and the symmetry factor of charge transfer has been evaluated at 0.5.     

Near—infrared SERS Study of the Adsorption of a PMMA Dip—coated onto Silver Mirror Substrate

The interface between a-PMMA thin film and silver mirror substrate was investigated using surface-enhanced Raman scattering (SERS). It is found that the molecular chain axis of a-PMMA tends to parallel the substrate in the interface. When the sample is annealed at different temperatures, some interesting changes appear in the SERS spectra. The spectra differences and their transition are due to the surface geometry change of the ester group.     

The effect of particle shape on the structure and rheological properties of carbon-based particle suspensions

The structure and rheological properties of carbon-based particle suspensions, i.e., carbon black(CB), multi-wall carbon nanotube(MWNT), graphene and hollow carbon sphere(HCS) suspended in polydimethylsiloxane(PDMS), are investigated. In order to study the effect of particle shape on the structure and rheological properties of suspensions, the content of surface oxygen-containing functional groups of carbon-based particles is controlled to be similar. Original spherical-like CB(fractal filler), rod-like MWNT and sheet-like graphene form large agglomerates in PDMS, while spherical HCS particles disperse relatively well in PDMS. The dispersion state of carbon-based particles affects the critical concentration of forming a rheological percolation network. Under weak shear, negative normal stress differences(ΔN) are observed in CB, MWNT and graphene suspensions, while ΔN is nearly zero for HCS suspensions. It is concluded that the vorticity alignment of CB, MWNT and graphene agglomerates under shear results in the negative ΔN. However, no obvious structural change is observed in HCS suspension under weak shear, and accordingly, the ΔN is almost zero.     

RETINA OF RIVER DOLPHIN LIPOTES VEXILLIFER

The structure of retina of the Lipotes Vexillifer has been studied quantitatively under light microscope. The results obtained are as follows.(ⅰ) The thickness of the retina is 268 μm. The lamination of retina can be clearly distinguished. It consists of 10 layers. The thicknesses of the layers from pigment epithelium to internal limiting membrane are 12 μm, 44 μm, 2 μm, 48 μm, 20 μm, 36 μm, 68 μm, 32 μm, 8 μm and 2 μm respectively.(ⅱ) The number of cells in the outer nuclear layer is larger than that in the inner nuclear layer. Two types of cell can be distinguished in this layer. The number of receptors and ganglion cells is in a ratio of 12 to 1. These results show that the retina type of the Lipotes corresponds to that of nocturnal animals.(ⅲ) The diameters of ganglion cells range 1.5—37 μm with two peaks at 6 μm and 35 μm. This means that the ganglion cells fall into two groups according to size, and this has been proved by the observation on morphology of ganglion cells in the wh     

Quantitative Structure—Property Relationship on Prediction of Surface Tension of Nonionic Surfactants

When a surfactant is solved into a solvent, it will adsorb onto the surface of the solution and reduce the surface free energy to a marked degree. The surface free energy, which is the minimum amount of work required to create that surface, is usually measured by surface tension. The minimum of surface tension 0g is the most useful key for characterizing the activity of surfactant. It is well known that 0g is determined by the molecular structure of surfactant, i.e., the contributions from …     

NUCLEATION MECHANISM OF PEO BLOCK IN DOUBLE-CRYSTALLINE POLY（ETHYLENE-co-BUTENE）-b-POLY（ETHYLENE OXIDE） BLOCK COPOLYMERS

In this paper, we proposed a method to determine the nucleation effect of pre-existing crystals on crystallization of the second block in double crystalline block copolymers, which is usually covered by the suppression effect. The nucleation mechanism of poly（ethylene oxide） （PEO） block from the pre-crystallized polyethylene （PE） block in poly（ethylene-cobutene）-b-poly（ethylene glycol） （EmEOn） diblock copolymers was investigated under variable crystallization environments. The crystallization environment for the PEO block was altered by cooling at different cooling rates or successive selfnucleation （SSN） to the PE block. It was found that the presence of nucleation effect is strongly dependent on composition of the block copolymers. The crystallization temperature （Tc） of PEO block in E174EO90 increases as cooling rate applied to the PE block decreases, indicating that PE block can nucleate the crystallization of PEO block and more perfect PE crystals have stronger nucleation effect. In E182EO41 crystallization of the PEO block is confined, shown by the disappearance of selfnucleation domain, and the PE block has no nucleation effect on the crystallization of PEO block. Double crystallization peaks are observed for the PEO block in E182EO41 and the intensity of the crystallization peak at higher temperature increases as the PE crystals become more perfect. After exclusion of homogeneous nucleation mechanism, the higher temperature crystallization peak of the PEO block in E182EO41 is tentatively ascribed to surface nucleation.     

Wrinkling and Growth Mechanism of CuO Nanowires in Thermal Oxidation of Copper Foil

We report a systematic study on wrinkling and CuO nanowires （NWs） growth in the thermal oxidation of copper foil. Copper foils with thickness of 0.5 mm were thermally oxidized in air at 500℃ for 0.5-10 h. It is found that all the samples have wrinkles and the size of the wrinkles increases with the oxidation time increasing. CuO NWs can grow on both the sidehill and hilltop of wrinkle. The CuO NWs on sidehill are longer and denser than those on hilltop. The growth direction of the CuO NWs on sidehill is not vertical to the substrate but vertical to their growth surfaces. The process of wrinkling and CuO NWs growth can be divided into three stages： undulating, voiding, and cracking. The CuO NWs on both sidehill and hilltop grow at the undulating stage. However, only the CuO NWs on sidehill grow and those on hilltop stop growing at the voiding and cracking stages because of the void in hilltop. The local electric field in a wrinkle at undulating stage was calculated, and it is found that the difference of local electric field strengths between hilltop and sidehill is small, which indicates that the predominant driving force for the diffusion of Cu ion during CuO NWs growth is internal stress.     

STUDIES ON THE RELATIONSHIP BETWEEN IR SPECTRA AND STRUCTURE OF SOME LINEAR Mo—Fe—S CLUSTERS.Ⅱ.LINEAR RELATIONSHIP BETWEEN SOME STRETCHING VIBRATION FREQUENCIES AND BOND DISTANCES

<正> The relationships between stretching vibration frequencies (v) and distances (r) of the bonds Mo-S and Fe-Cl in ten compounds have been investigated- It is found that vMO-S is linearly related to rMo-s. This provides a convenient method to obtained bond distance data for some cluster compounds whose molecular structures could not be determined by X-ray analyses, The linear relationship between vFe-cl and rFe-cl is also discussed. The near-linear relationships of vvs. rFe-Mo and vFe-sb vs. rFe-Mo demons-trate that the formation of Fe-Sb bond has an important influence on the formation of Fe-Mo bond and the Fe-Mo distance may be estimated from v values.     

STUDIES ON THE MECHANICAL PROPERTIES AND CRYSTALLIZATION BEHAVIOR OF POLYETHYLENE COMPOSITES

The effects of inter facial modifier on the mechanical, dynamic mechanical properties andcrystallization behavior of the polyethylene composites were investigated in the present paper.It was found that the interfacial modifer significantly improved the mechanical properties,influenced the dynamic mechanical spectra and slightly changed the crystallization behavior.The results showed that the interfacial modifier changed the dispersion state of dispersedphase of the composites, resulting in different phase structure, which was the major reasonIeading to different mechanical and crystallization properties.