Characterization of phosphorus doped CVD diamond films by cathodoluminescence spectroscopy and topography

A phosphorus doped homoepitaxial diamond film made by a CVD method was investigated by cathodoluminescence spectroscopy and topography. An exciton peak bound to phosphorus at 239 nm was observed from {001} as well as {111}, but the wavelength and width of the peak varied depending on location of the sample. This may be due to the difference of crystal perfection. It was found in the spectra that the slope with an array of weak peaks has a maximum of approximately 270 nm. This broad band may be an indicator of incorporation of phosphorus, although all the phosphorus doped diamonds do not exhibit the band. No other peak expected to be related to phosphorus was found, but several peaks commonly observed from CVD diamond were seen instead. These were also dependent on growth surface. Peaks at 415, 482, 500, 514 and 532 nm were strong on {111} surfaces of the non-epitaxial crystallites, whereas the 575-nm peak and another system of the 532-nm peaks were stronger in {001} epitaxial layers, as reported earlier.     

Influence of forming method of blending versus casting layer-by-layer on structural properties and packing performances of casein-gelatin composite edible film under different appending proportion

In order to obtain casein edible films with great packing performance, gelatin as the reinforcing additive with different ratios were loaded via two methods including layer- by- layer and blending. A comparative study on structure properties between double layers and blending films made from casein and gelatin was obtained by scanning electron microscopy and Fourier transform infrared spectroscopy. The difference between the films' packing characters were conducted by water vapor permeability (WVP), optical property, and mechanical properties (including tensile strength (TS) and elongation (EAB)). The results showed that the degree of films roughness increased and the structural stability decreased as the increase of gelatin additive ratio in both double layers and blending films. Thickness and WVP both displayed a trend of increasing first then decreasing at the dividing of gelatin instead of casein in 50%. Importantly, WVP values in double layers film with a largest value of 6.95 gm⁻¹Pa⁻¹s⁻¹ was higher than blending films, observably (P < 0.05). Additionally, TS in blending film was increased by 23.44% than double layers film under the gelatin additive proportion of 70%, and EAB value in double layers film was larger by 207.65% than blending film under the gelatin additive proportion of 10%.     

A numerical model for current transients during micro-indentation of passive iron surface

During in situ micro-indentation of passive iron in pH 8.4 borate solution, a couple of anodic current peaks emerged; the first peak during loading and the second peak during unloading. The current transients, associated with rupture and repair of the passive film, were influenced by the indentation conditions. For instance, the current peak height, the current peak area and the time required for complete repassivation are strongly dependent on indentation rate. A numerical model was proposed to correlate the current transient during loading with mechanical deformation of the passive surface. The comparison between the current transient measured experimentally and that estimated from the load transient suggested that the ruptured area of passive film was about 10% of the surface area deformed by the contact with the indenter.     

Perchlorate and oxygen reduction during Zn corrosion in a neutral medium

A comparison between the potentiodynamic behaviour of the stationary and the rotating Zn disc electrodes in naturally aerated and de-aerated 0.1 M KClO₄ solution was performed. The voltammograms of the stationary electrode in both solutions exhibited one anodic peak and two cathodic peaks. The anodic peak is replaced by two mass transport controlled O₂ reduction cathodic current plateaus in the forward scan by rotating the electrode in naturally aerated solutions. However, the reverse scan is characterized by only one cathodic peak observed at a potential depends on the experimental conditions. The more cathodic reduction peak was referred to the reduction of the passive layer and split into two peaks at low scan rates. Interpretation of these data was made adopting a multi-path mechanism and a two layer passive film model. A correlation between the ClO₄⁻ and dissolved O₂ reduction and the thickness of the two passive layers was performed. The protective nature of the passive layers formed in different experimental conditions was found to decrease with rotating the electrode and de-aerating the solution. Chrono-potentiometry and electrochemical impedance measurements were also used in this study. Impedance technique showed a change in the ZnO thickness with the experimental conditions as a result of changing the reactions occurring in the electrode vicinity.     

少烟NEPE推进剂的动态力学性能

用动态力学分析方法研究了少烟NEPE推进剂及其黏合剂胶片的黏弹特性。结果表明,PET/N100胶片、PET/N100/NG-TEGDN胶片和推进剂样品在玻璃态的储能模量E′依次增大,PET/N100胶片的损耗模量E″最大,推进剂的E″最小;胶片和推进剂在玻璃化转变区的E′依次显著降低,E″和tanδ(β转变)依次达到最大值后逐渐降低,其中PET/N100胶片、PET/N100/NG-TEGDN胶片和推进剂的Tg分别为-82、-73和-65℃;在橡胶态,PET/N100胶片的E′和E″在-24℃附近出现峰值,PET/N100/NG-TEGDN胶片和推进剂的E′和E″随温度降低显著降低,且PET/N100胶片在-3℃出现明显的α松弛损耗峰,PET/N100/NG-TEGDN胶片和推进剂tanδ的α松弛峰温下降到-24℃。     

SrBi4Ti4O15薄膜的溶胶凝胶制备及其生长行为

以氯化锶、硝酸铋和钛酸丁酯为原料,柠檬酸为络合剂,配制了稳定的SrBi4Ti4O15（SBTi）前驱液.采用层层快速退火工艺,在Pt/Ti/SiO2/Si基片上制备了a轴取向增强的SBTi铁电薄膜,通过场发射扫描电镜、环境扫描电镜及X射线衍射等微观分析手段研究了保温时间和成膜次数对薄膜结晶性、微观结构和生长行为的影响.结果表明：层层快速退火工艺,可有效抑制焦绿石相的形成.随着退火时间的延长,薄膜的结晶性变好;但退火时间延长到30 min以上,薄膜的结晶性变差.由于SBTi晶体生长的各向异性及单层膜厚对晶体沿[119]方向生长的限制,随着涂覆次数的增加,SBTi薄膜（119）峰和（200）峰的强度逐渐增大,而（00l）峰的强度反而略有减少,从而使I（200）/I（119）、I（200）/I（0010）、I（119）/I（0010）逐渐增大.     

Preparation,characterization, antibacterial properties,and hemostatic evaluation of ibuprofen‐loaded chitosan/gelatin composite films

Ibuprofen‐loaded chitosan/gelatin (CS/GE) composite films were fabricated in this work. The morphology of the composite film was investigated using scanning electron microscopy. The functional groups of the composite film before and after crosslinking were characterized using Fourier transform infrared spectroscopy. Meanwhile, the mechanical properties, antibacterial performance, cytocompatibility, and hemostatic activity of the composite films were investigated. The results show that the amount of CS affected the mechanical properties and liquid uptake capacities of the composite films. The composite film showed better bactericidal activity against Staphylococcus aureus than Escherichia coli. In vitro drug‐release evaluations showed that crosslinking could control the drug‐release rate and period in wound healing. Both types of CS/GE and drug‐loaded CS/GE composite films also showed excellent cytocompatibility in cytotoxicity assays. The hemostatic evaluation indicated that the composite film crosslinked by glutaraldehyde in rabbit livers had a dramatic hemostatic efficacy. Therefore, ibuprofen‐loaded CS/GE composite films are potentially applicable as a wound dressing material. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45441.     

Morphology and Properties of Polypropylene Foaming Sheet with Alternating Multilayered Structure

In this work, the foaming sheet was designed as alternating multilayered foam/film structure of foaming layers and film layers. The foaming layer contained polypropylene (PP)/high density polyethylene (HDPE)/Talc ternary composites. The film layer contained PP only. The rheological data showed that the melt elasticity of PP was obviously improved by the addition of HDPE and talc. The results exhibited that the alternating multilayered structure was well kept and hardly influenced by the foaming layers, and then the mechanical properties were obviously improved. The cell in the alternating multilayered sheet with 16 layers was smaller and more homogenous than that in pure PP foaming sheet.     

Origin of the intermediate damping peak in microlayer composites

A comparison of glass transition temperatures measured by differential scaning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) was made using mi9crolayer composites with many alternating layers of two polymers. What appeared to be a third transition at a temperature intermediate between the glass transitions of the two components was observ ed in DMTA but not DSC. The mechanical orgin of this intermediate damping peak in the layered composites was established. The viscoelastic properties of each polymer were modelled by a spring and dashpot in series, and the composite as a parallel arrangement of two Maxwell elements. It was shown that an anomalous damping peak can appear between the glass transition temperatures when the modulus of the composite can not drop below the modulus of the glassy layers, although the viscosity of the composite continues to be defined by the viscosity of the rubbery layers in this temperature range. The intermediate damping peak may be a general feature in the dynamic mechanical behavior of co-continuous multiphase systems including polymer blends and continuous fiber composites.     

TEM structure of (PyC/SiC)n multilayered interphases in SiC/SiC composites

Two generations of multilayered interphases, composed of carbon and silicon carbide, have been developed to act as a mechanical fuse in SiC/SiC composites with improved oxidation resistance. Pyrocarbon is an ideal interfacial material, from the mechanical point of view, whereas SiC has a good oxidation resistance. In the multilayered interphase, the carbon mechanical fuse is split into thin sublayers, each being protected against oxidation by the neighbouring SiC-based glass former layers. A first generation of multilayers as synthesised by means of isobaric-CVI with sublayers with micrometric thickness. Then, in order to push forward the concept, pressure pulsed-CVI was involved to deposit nanometric scale sublayers. In this work, transmission electron microscopy was developed to characterise the two generations of materials. The microstructure of the layers and the influence of the fibrous preforms on the structure of the layers were studied. Examinations were then performed on the loaded samples and damaging mode characterised at nanometric scale.     

Mechano-electrochemistry of a passive surface using an in situ micro-indentation test

Depassivation–repassivation of iron surfaces in boric–borate solutions were investigated by using the micro-indentation test. A pair of current peaks due to repair of the passive film following rupture of the film were observed during a series of indenter drives, i.e., loading and unloading of the indenter. The shape of the current peak depended on environmental conditions (conductivity and pH of the solution) and substrate conditions (mechanical processing history, alloyed element) as well as indentation conditions (repetition, maximum depth, and maximum load). Plastic deformation of the surface was accompanied by surface depassivation, while no depassivation occurred during the elastic deformation, indicating that the passive film on iron has a ductile property. The solution conditions did not affect the scale of depassivation but affected the rate of repassivation. Dislocations in the substrate made surface depassivation difficult but enhanced reactivity during the repassivation. The test also revealed that type-312L stainless steel has high corrosion resistance in a concentrated NaCl solution.     

Film morphology and molecular orientation in oligothiophene-fluorene films

The effects of processing conditions on film morphology and molecular orientation were studied for a novel conjugated fluorene-bithiophene oligomer, oligo(9,9-dioctylfluorene-alt-bithiophene) (OF8T2). Depending on the method of film preparation, OF8T2 molecules adopt different orientations in the films. X-ray diffraction peak at 4.9° of the OF8T2 film deposited from petroleum ether/dichloromethane mixture is attributed to a layering distance between sheets of OF8T2 chains, which are separated by the octyl side chains. Preferred orientation is clearly inferred through the absence of peaks corresponding to π-π stacking. For the spin-coated film after annealing, X-ray diffraction patterns indicate the presence of lamellar structure with the plane of the conjugated backbone normal to the substrate. The molecules were aligned with long axes along the rubbing direction when the spin-coated film was rubbed and then annealed. These results suggest a convenient approach for preparing active layers for organic optoelectronic devices by simple solution methods.     

Miscibility behavior of poly(n‐butyl methacrylate) latex films containing alkali‐soluble resin

The dynamic mechanical properties of poly(n‐butyl methacrylate) (PBMA) latex films postadded with alkali‐soluble resin (ASR) have been studied and compared with those of latex films prepared by emulsion polymerization in the presence of ASR (ASR‐fortified latex). The miscibility between PBMA and ASR, poly(styrene/alpha‐methylstyrene/acrylic acid) (SAA), was found to influence the dynamic mechanical behavior of the films. The dynamic properties of PBMA latex films postadded with SAA show two distinct damping peaks, which correspond to those of PBMA and SAA, respectively, in the phase‐separated state. The SAA migrates onto film surface during film formation and, as a result SAA preserved their domains in the matrix phase, showing two distinct relaxations in the dynamic mechanical spectrum. On the other hand, the ASR‐fortified films exhibit single damping peak. SAA‐fortified latex particles would be core/shell structured, and the miscibility between PBMA and SAA is clearly improved by the grafting reaction between PBMA and SAA. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 639–649, 2000     

Asymmetry of Peak Shapes in Linear Gas—Liquid Chromatography

Abstract

A mathematical model describing axial dispersion, interparticle mass transfer, intraparticle gas diffusion, and diffusion in a uniform thickness liquid film is used systematically to investigate the influence of intraparticle diffusivity, diffusivity in a stationary liquid phase (SLP), partition coefficient, and thickness of liquid film on the shape of the peaks in linear gas—liquid chromatography by converting Laplace transformed equations into time domain. The low diffusivities of intraparticle and/or SLP can cause the asymmetry and long tail in chromatographic peaks. A higher partition coefficient and the film thickness at low diffusivities also give skewed peaks. At a higher mass transfer rate, the peak becomes sharper. From these results a guide can be suggested to avoid the asymmetric condition of long-tailing peaks.     

Multilayer graphene grown by precipitation upon cooling of nickel on diamond

Multilayer graphene is grown by precipitation upon cooling of a thin nickel film deposited by e-beam evaporation on single crystal diamond (0 0 1) oriented substrates. Nickel acts as a strong catalyst inducing the dissolution of carbon from diamond into the metal. Carbon segregation produces multilayers of graphene on the top surface. Characterization by Raman spectroscopy reveals that these thin layers display relatively narrow Raman phonon peaks that are typically associated with graphene. Atomic force microscope measurements reveal a multigrain structure that reproduces small domains in the nickel film. The multilayer graphene is transferred onto a optical microscope glass slide for further analysis. The thickness of the layers estimated from optical transmission measurements is 12 nm. The catalytic reaction found for nickel on diamond is not observed when glassy carbon is used as substrate. This method provides a venue for the fabrication of large area graphene films.     

Cyclic voltammetric studies of electroless cobalt in NaOH

The electrochemical behaviour of electroless cobalt in 1N NaOH was studied at 35, 60 and 85°C by cyclic voltammetry. Three anodic peaks corresponding to the formation of Co(OH)₂/CoO, Co₃O₄, Co OOH were observed. The observed cathodic peaks were due to the reduction of the higher cobalt oxides to Co(OH)₂ and also due to the reduction of Co(OH)₂ to cobalt. The variation of peak potential with sweep rate was found to be appreciable only in the case of anodic peak (I). The total charge Q_T, for the passivation to occur was obtained by estimating the area under the first anodic peak at each sweep rate. It was found that the Q_T value decreases with increase of sweep rate. The increase of peak current with increase of sweep rate has been explained as due to the insufficient time available for the film growth at the reversible potential, and that the dissolution of the metal continues until a potential at which the rate of film growth exceeds that of active dissolution is reached. It has been suggested that the passivating film is CoO while the prepassive film is Co(OH)₂. The shift of the anodic peak (I) potentials to more anodic values compared to that for pure cobalt is probably due to the presence of phosphorus in the cobalt deposit.     

Effects of vacuum ultraviolet on the structure and optical properties of poly(tetrafluoroethylene) films

The effects of vacuum ultraviolet (VUV) at wavelengths of 5–200 nm on the microscopic structure and optical properties of poly(tetrafluoroethylene) (PTFE) films were investigated. X‐ray photoelectron spectroscopy analysis showed that the C_1s spectra changed from a single peak at 292.8 eV to multiplex peaks with binding energies of 284.6, 286.6, 288.6, 290.5, and 293.0 eV after VUV irradiation at 680 esh. With an increasing irradiation dose, the C_1s peaks at 290.5 and 293.0 eV disappeared. After the PTFE film specimens irradiated at 1600 esh were sputtered with argon ions for 3 min, the C_1s peaks at 290.5 and 293.0 eV appeared again, and the height of the peaks at 286.6 and 288.6 eV increased. The content of fluorine decreased after VUV irradiation. The content of fluorine in the film surface layer decreased significantly with the increase in the VUV intensity, but it did not change with the irradiation dose. Fourier transform infrared (FTIR) analysis results indicated that some conjugated bonds, such as ? FC?CF? , were formed during VUV irradiation, but no CH absorption bands were observed in the FTIR spectra; this indicated that the increase in the height of the C_1s peak at 284.6 eV arose mainly from the carbon–carbon bonds, that is, from carbonification. The spectral transmittance of the PTFE film decreased gradually with an increasing VUV irradiation dose, and at a given dose, the lower the intensity was of the VUV irradiation, the greater the change was in the spectral transmittance. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 115–121, 2003     

Nanoparticle reinforced epoxy gelcoats for fiber-plastic composites under multiple load

Novel surface coatings that are load-adapted and suitable for economical manufacturing are required for fiber-plastic composites subjected to complex loads. They must have good wear and chemical resistance compared to conventional thermoset coatings (paints, gelcoats), and high failure strain and adhesive strength compared to metallic or ceramic protection layers. Polymeric nanocomposites offer particular advantages in this respect. Given this background, the main aim of this work is to characterize and evaluate surface-protection layers made of metal oxide nanoparticle reinforced epoxy gelcoats for mechanical, tribological and media loaded fiber-reinforced plastics (FRP). The focus is set on the property characterization of the heterogeneous gelcoat as a function of particle material and filler content, as well as the adjustment of the required rheological properties of the liquid particle-resin dispersion so that nanoparticle reinforced gelcoats can be applied to the anisotropic FRP substrate by spray processing in an economical and variable-geometry manner.     

Tunable Drug Loading and Reinforcement of Polycaprolactone Films by Means of Electrospun Nanofibers of Glycolide Segmented Copolymers

Electrospinning of a segmented copolymer having polyglycolide hard segments is successfully performed from 1,1,1,3,3,3‐hexafluoroisopropanol solutions. During the process, a bactericidal agent, i.e., chlorhexidine (CHX), is effectively loaded, which results in nanofibers with a smaller diameter because of the change in solution conductivity. New fabrics based on molding of alternate layers of poly(ε‐caprolactone) (PCL) films and the electrospun scaffolds of the segmented copolymer are prepared and characterized. The thermal molding process renders a PCL matrix homogeneously reinforced with nanofibers that compensate for the loss of mechanical properties caused by incorporation of CHX. Release of CHX is evaluated in different media. Results vary depending on the layer where the drug is incorporated. Thus, systems with an immediate bacteriostatic effect, as well as systems with a potential long term antimicrobial effect, are obtained. Growth inhibition and adhesion assays demonstrate the fast bactericidal effect of samples with CHX loaded in its outer layers.     

The Additivity and Stability of Carbon Signatures Obtained by Evolved Gas Analysis

Evolved Gas Analysis (EGA) profiles are evaluated as a tool to classify carbonaceous aerosols for source apportionment studies. EGA is a method of characterizing carbonaceous aerosols according to their volatility. In this study the stability and additivity of EGA profiles were examined explicitly for the purpose of determining the applicability of EGA characterization to chemical mass balance techniques. Samples collected in a vehicle tunnel were subsequently exposed to particle-free (filtered) and particle-laden ambient air. The EGA profile did not change for tunnel samples exposed to filtered ambient air. By contrast, for tunnel samples exposed to particle-laden (unfiltered) ambient air, the resultant EGA profile was not the direct sum of the ambient and tunnel profiles. Specifically, the low-volatility carbon peak evolved at a lower temperature than the same peak in the unexposed tunnel samples. The change in evolution temperature was independent of carbon mass loading. Although evolution temperatures of characteristic peaks shifted, both the ambient and the tunnel profiles could be classified into three characteristic peaks, corresponding to high-, intermediate-, and low-volatility carbon. Additivity of ambient samples yielded an uncertainty of 13% within a given peak. Additivity of the tunnel samples subsequently loaded with ambient aerosol yielded an uncertainty of 19% within a given peak.