Derivatographic studies of polyethylene containing a dispersed semiconductor

The tendencies of the changes in the physical-chemical characteristics of high-density polyethylene films and polyethylene composites with a volumetric content of TlInS₂ ferroelectric-semiconductor of up to 10% are investigated with the help of the DTA method. The changes in the thermophysical characteristics of the analyzed composites are shown to be related to the structural changes of the polymer under the effect of the additive particles with different degrees of dispersion. At 5 vol % of TlInS₂, the additive particles act as artificial nuclei of structure formation.     

Thin nanocomposite layers based on a complex of polyaniline and graphene

Two techniques of manufacturing a nanocomposite based on a complex of polyaniline with polymer acid and graphene are proposed. The electric conductivity of thin nanocomposite layers is higher than that of a polymer complex of polyaniline and strongly depends on the degree of oxidation of graphene. An explanation of the effect is suggested that takes into account electron interactions between the graphene planes and polyaniline backbone, as well as the possibility of formation of hydrogen bonds between functional groups of semioxidized graphene and polyacid. The results of surface topography analysis for thin layers of polyaniline and nanocomposite agree well with the regularities of the structure of each layer that are due to the above interactions between graphene and the polymer complex.     

A flexible microwave absorber based on nickel ferrite nanocomposite

Flexible magnetic composite materials were prepared by incorporating precharacterized nickel ferrite nanoparticles in a natural rubber matrix. The complex dielectric permittivity and magnetic permeability of the composites were measured at different microwave frequencies using the cavity perturbation technique. A steady increase in dielectric permittivity was observed with increase in filler concentration. Maxwell-Garnett mixture equations were employed to model the effective permittivity and permeability of the composite. Reflection loss was estimated by employing the model of single layer absorber backed with a perfect conductor. Reflection loss minima of ?5.9 dB at 3.2 GHz for 12 mm thick rubber ferrite composite sheet is obtained in the S-band while a loss up to ?16 dB could be achieved at 9.5 GHz in the X-band.     

Preparation and tribological studies of nanocomposite films fabricated using spin-assisted layer-by-layer assembly

Uniform and smooth composite multilayer films composed of gold nanoparticles and polyelectrolytes ([Au/(PAH-PSS)_nPAH]_m) multilayers were fabricated on a silicon substrate using a time-and cost-efficient spin-assisted layer-by-layer (SA-LbL) self-assembly technique. The microstructure and morphology of the multilayer films were characterized by means of transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The tribological behavior of the composite multilayer films was evaluated using a ball-on-plate tribometer. It was found that the density of the monolayer of gold nanoparticles on the silicon substrate was dependent on the deposition time, but the coverage of the Si substrate by the gold nanoparticle kept almost unchanged at a deposition duration above 30 min. The antiwear life and load-carrying capacity of the [Au/(PAH-PSS)_nPAH]_m composite film substantially increased with increasing number of the polymer bilayers and gold nanoparticles monolayer, which could be attributed to the robust organic-inorganic nanocomposite structure and PAH and PSS fragments transferred onto the counterpart surface.     

Inhibitor of hydrogen sulfide corrosion of steel based on di- and polypropylene polyamines

Several aminoimidazolines and their derivatives are produced from di-and polypropylene polyamines and higher isomeric acids. Varying of the composition and ratio between the components of preparative form enabled us to produce a water-soluble corrosion inhibitor that effectively protects steel against hydrogenation and corrosion in hydrogen sulfide media. Original Russian Text ? G.I. Akhmadeeva, R.N. Zagidullin, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 6, pp. 620–626.     

Antistatic coating and electromagnetic shielding properties of a hybrid material based on polyaniline/organoclay nanocomposite and EPDM rubber

Thermal, mechanical, electrical and microwave radiation absorbing properties of conductive composites based on dodecylbenzenesulfonate doped polyaniline/organoclay nanocomposites and propylene–ethylidene–norbornene rubber have been investigated with special interest on the effect of the nanocomposite concentration. Composites were prepared by melt blending using an internal mixer. Morphology studies by scanning electron microscopy of cryofractured surfaces indicated that the conducting nanocomposites produced heterogeneously distributed aggregates in the continuous elastomeric matrix. The composites exhibit high conductivities, up to 10⁻³ S cm⁻¹ for 40 wt.% of conducting nanocomposite, and good mechanical properties. They also present high microwave attenuation values, in the frequency range of 8–12 GHz. This property depends on the concentration of the conductive nanocomposite and on the film thickness. The composites can be used for antistatic coatings or for electromagnetic shielding.     

NO2 gas sensing based on ordered ultrathin films of conducting polymer and its nanocomposite

The metal oxides films are widely used for CO, aromatic hydrocarbon and NO₂, gas-sensing applications, but such sensors mostly lack selectivity and operate at high temperatures (300–500 °C). We focused on the use of organized ultrathin films of conducting polymers and their nanocomposites, which recognize selectively the NO₂ gases with a very high sensitivity (≤ppb). Polyhexylthiophene (PHTh), poly(ethylene dioxythiophene) (PEDT), PHTh–PEDT copolymer, sulfonated polyaniline, polyaniline (PANI)–SnO₂, polypyrrole (PPy)–SnO₂, PEDT-SnO₂, PHTh–SnO₂ and copolymer (HTh-EDT)–SnO₂ conducting polymer and nanocomposite thin films were fabricated and used for gas sensing applications. The physical properties (UV and FTIR) such films were investigated before and after the NO₂ gas treatment. Regioregular PHTh, its copolymer P(HTh-PEDT), and their metal oxide nanocomposites films detected NO₂ gas with a high sensitivity.     

Synthesis,characterization and spectroscopic studies of CdS/polyaniline core/shell nanocomposite

In this work, CdS/polyaniline (PANI) nanocomposite was synthesized by a novel method. Transmission electron microscope (TEM) images showed that the CdS/PANI nanocomposite had a core/shell structure. The crystal structure was studied using X-ray diffraction (XRD) and the obtained results showed that CdS had cubic structure. Fourier transform infrared (FTIR) spectroscopic measurements confirmed the formation of PANI at the surface of CdS nanoparticle. The prepared samples were further characterized using UV–visible (UV–vis) and fluorescence spectroscopy.     

A study of the structure and dielectric properties of nanocomposites based on polypropylene and zirconia nanoparticles

New nanocomposite structures based on isotactic polypropylene and zirconia nanoparticles are developed; the distribution of the zirconia nanoparticles is studied by optical (Motic AE 30/31) and scanning electron microscopy (Carl Zeiss). It is shown that, during the direct introduction of nanopowders into the polymer matrix, the powder nanoparticles form cluster-like fractal structures in the form of dendrites even at the first stage of mixing of the components. The electron microscopy study of the samples shows that the developed technique for preparing nanocomposites makes it possible to obtain a homogeneous distribution of zirconia nanoparticles in the matrix of polypropylene. The dielectric characteristics of nanocomposites based on polypropylene and zirconia are studied. It is found that the dielectric permeability in PP + ZrO₂ nanocomposites varies as a function of the frequency owing to the low-frequency polarization.     

脉冲电沉积SiC/TiN颗粒增强Ni-Mo纳米复合镀层研究

米用脉冲电沉积技术在6061铝合金表面制备SiC/TiN颗粒增强Ni-Mo纳米复合镀层.通过在镀层中引入SiC、TiN纳米颗粒并改变电沉积的平均电流密度和占空比,调控复合镀层的微结构,探讨纳米颗粒增强涂层的成膜过程与晶粒细化机理,研究复合镀层的组织结构与耐蚀性、耐磨性的关系.结果表明:双纳米颗粒的加入使镀层结构由锥状向...     

Thermal decomposition kinetics of in situ reinforcing composite based on polypropylene and liquid crystalline polymer

A thermotropic liquid crystalline polymer (TLCP), a copolyester with a 80/20 molar ratio of p-hydroxy benzoic acid (HBA) and poly(ethylene terephthalate (PET), known as Rodrun LC5000, was melt blended with polypropylene (PP) using a twin-screw extruder. The thermal degradation of the blends containing various TLCP contents was investigated using thermogravimetry (TG). In nitrogen and in air, the TG profiles of PP revealed a single weight-loss step, whereas TLCP showed two and three major weight-loss steps in nitrogen and in air, respectively. In air, more complex TG curves were observed for the blends with TLCP loading. Simultaneous DSC thermograms revealed that the degradation processes for all neat polymers and the blends were endothermic in nitrogen and exothermic in air. The kinetic parameters (E_a, ln A, and n) calculated using isoconversional method indicated that the thermal stability of PP was significantly improved by in situ reinforcing with TLCP. Addition of SEBS-g-MA compatibilizer slightly enhanced the thermal resistance of blend.     

Electrical properties and applications of carbon based nanocomposite materials: An overview

The allotropic forms of carbon (amorphous and polycrystalline graphite, carbon black, fullerenes, nanotubes, graphene) exhibit a large variety of charge transport properties which have been stimulating fundamental and applied research for the development of new devices based on micro and nano-sized electronic systems. Carbon based nanocomposites offer the possibility to improve the device performances and to develop novel multifunctional material systems by combining the properties of each individual phase. In this paper we review the electrical properties of carbon materials and some of the most exciting carbon based nanocomposites, as well as their potential technological applications. First, the electrical properties of amorphous and polycrystalline graphitic materials and those of their related nanocomposites materials are discussed. Second, an overview of the state-of-art on research and applications of carbon nanotube-based composites is presented. Third, we discuss briefly the emerging area of research related to graphene materials. Finally, the electrical properties and applications of conducting carbon black aggregates and carbon black/polymer composites are overviewed.     

Structural and Mössbauer studies on mechanical milled SmCo5/α-Fe nanocomposite magnetic powders

The SmCo₅/α-Fe nanocomposite powders were prepared by high energy ball milling and the inter-diffusion reaction between the SmCo₅ and α-Fe magnetic phases were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM) and ⁵⁷Fe Mössbauer spectroscopy. While structural and magnetic measurements could reveal only the presence of SmCo₅ and α-Fe phases, Mössbauer studies could clearly specify the extent of alloying between Fe and Co atoms in terms of evolution of α-Fe(Co) phase as a function of milling time. It has been found that the fractional volume of α-Fe(Co) solid solution tends to increase at the expense of the initial α-Fe phase upon progressive milling.     

DK7725A型电火花线切割机操作技巧及加工工艺分析

针对DK7725A型高速走丝线切割机床在加工特殊工件时存在的一些问题进行了分析,从工件的装夹,加工参数、加工速度的设置,操作规范的应用,以及降低断丝几率等加工技巧方面进行了详细的讨论,提出了相应的改进措施,从而有利于提高加工质量和加工的稳定性.     

基于模糊综合评价的DK77系列电火花线切割机床可靠性评估

针对目前系统可靠性综合评估普遍使用的加权综合评价法反映信息不全面的问题,结合DK77系列电火花线切割机床可靠性数据,利用模糊评价法对DK77系列电火花线切割机床可靠性进行综合评估.评估结果表明:DK77系列电火花线切割机床可靠性水平远远低于国内数控机床可靠性水平,需要尽快提高其可靠性水平.     

The effect of the temperature-time mode of crystallization on the morphology and properties of nanocomposites based on polypropylene and cadmium sulfide

In this work, we describe the results of studying the effect of the temperature-time modes of crystallization on the structure and properties of nanocomposites based on polypropylene and cadmium sulfide prepared via electrical discharge treatment in an air medium above the breakdown strength of the air. The temperature-time modes of the crystallization and other treatment factors change the supramolecular structure of the polymer, the interfacial interactions between the components of the composites, and the thickness of the interfacial layer.     

Molybdenum disulfide as a lubricant and catalyst in adaptive nanocomposite coatings

Nanocomposite YSZ-Ag-Mo-MoS₂ coatings with different MoS₂ additions (0-100 at.%) were deposited with a hybrid pulsed laser/magnetron sputtering/filtered cathodic arc process. Wear testing was performed from 25 to 700 °C for each of the coatings. Electron microscopy and other characterization techniques were used to examine the surfaces and wear tracks of the coatings and to determine the mechanisms resulting in the measured tribological properties. Adaptive coatings containing 8 at.% MoS₂ demonstrated a friction coefficient of 0.2 throughout the temperature range examined here, compared to 0.4 for YSZ-Ag-Mo with no MoS₂. Characterization of the YSZ-Ag-Mo-8% MoS₂ coating revealed that MoS₂ and silver provided lubrication at temperatures ≤ 300 °C, while silver molybdate phases and MoO₃ were effective lubricants at higher temperatures. Silver molybdate was not observed in the coatings containing 0% MoS₂. The role of sulfur in the formation of silver molybdate is briefly discussed.