Preparation of conducting silver paste with Ag nanoparticles prepared by e-beam irradiation

Conducting silver paste was prepared by using Ag nanoparticles which were synthesized by e-beam irradiation method (from KAERI); its conductivity was comparatively determined with Ag nanoparticles which were prepared by thermolysis method (commercial). The silver nanoparticles with the diameter of approximately 150 nm size prepared by e-beam irradiation were mixed with glass frit and sintered for 1 h at 500 °C. It is presumably concluded that the wt% of silver nanoparticle, size distribution and homogenous dispersibility of Ag nanoparticles in the pastes are the critical factors for the high conductivity of the paste. Among the various wt% of silver nanoparticle in the conducting silver pastes, silver paste with 90 wt% of silver nanoparticle has the highest conductivity as 1.6×10⁴ S cm^?1. This conductivity value is 1.6 times higher than the Ag pastes which were prepared with silver nanoparticles obtained by thermolysis method.     

Influence of Cu6PS5І superionic nanoparticles on the dielectric properties of 6СВ liquid crystal

Influence of Cu₆PS₅? nanoparticles on the dielectric properties of planarly oriented 6СВ liquid crystal (LC) is studied in the 10–10⁶-Hz frequency range. Introduction of the nanoparticles is shown to result in an increase of the electric conductivity. Contrary to 6СНВТ LC, the conductivity monotonously depends on the nanoparticles’ concentration. The main reason of the much greater influence of Cu₆PS₅? nanoparticles on the 6СВ conductivity in comparison with 6СНВТ is related to a greater dissociation coefficient of Cu₆PS₅? in 6СВ than in 6СНВТ. This is confirmed by the fact that the dipole moment of the 6СВ molecules is greater than that of the 6СНВТ molecules.     

Influence of thermal history and humidity on the ionic conductivity of nanoparticle‐filled solid polymer electrolytes

The crystallinity and conductivity of nanoparticle‐filled solid polymer electrolytes (SPEs) are investigated as a function of thermal history and water content. Our objective is to evaluate how performance is affected by the conditions under which the SPEs are handled and tested. The samples consist of polyethylene oxide (PEO), LiClO₄, and Al₂O₃ nanoparticles. At low humidity, SPEs at ether oxygen to lithium ratios of 8:1 do not crystallize immediately; instead, 3 days are required for crystallization to occur, and this does not depend strongly on the presence of nanoparticles. The conductivity is improved by the addition of nanoparticles at low humidity, but only at an ether oxygen to lithium ratio of 10:1, which corresponds to the eutectic concentration. At high humidity, the recrystallization time is delayed for 3 weeks, and the conductivity increases in both filled and unfilled SPEs beyond that of the low humidity samples. Although we observe that water amplifies the influence of nanoparticles on conductivity, we also find that nanoparticles inhibit water uptake—but only in the presence of lithium. Because Li⁺ strongly absorbs water, this result suggests that nanoparticles may interact directly with Li⁺ ions to prevent water uptake. In filled samples at the eutectic concentration (10:1), more water is absorbed compared to the nanoparticle‐filled 8:1 samples, even though less lithium is present. This suggests that nanoparticles may segregate to lithium‐poor regions in the 10:1 samples, and this scenario is supported by the morphology that would be expected at the eutectic concentration. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1496–1505, 2011     

纳米氧化镍浓度对磁性准固态染料敏化太阳能电池的影响

以琼脂糖为聚合物基质,N-甲基-2-吡咯烷酮(NMP)为溶剂,磁性纳米氧化镍颗粒作为添加剂用于制备染料敏化太阳能电池(DSSC)的磁性聚合物电解质。通过SEM与离子电导率测试研究不同纳米氧化镍掺杂浓度对磁性聚合物电解质的影响,并对相应的染料敏化太阳能电池进行光电性能测试与电化学交流组抗谱(EIS)测试,结果表明:1.0wt%的纳米氧化镍掺杂浓度为最优掺杂浓度,在此浓度下聚合物电解质的表面形貌较为平整,同时电解质具备最高离子电导率(2.43×10-3S.cm-1);染料敏化太阳能电池的光电效率与电子寿命均随着纳米氧化镍掺杂浓度的增加而先增加后降低,并都在纳米氧化镍掺杂浓度为1.0wt%达到最大,此时电池的光电效率为1.63%、开路电压为0.57 V、短路电流密度为5.8 mA.cm-2、填充因子为0.53。     

室温离子液体增塑的纳米复合聚合物电解质研究

在室温离子液体N-乙基-N'-甲基咪唑四氟硼酸盐(EMIBF₄)增塑的凝胶聚合物电解质中加入氧化铝纳米粒子, 制备了一种纳米复合聚合物电解质(nanocomposite polymer electrolyte, NCPE). 通过示差扫描量热(DSC)、X射线衍射(XRD)、热重分析(TGA)、电化学阻抗谱(EIS)等手段对其进行了表征. 结果显示, 随着氧化铝纳米粒子含量的增加, NCPE的结晶度降低, 离子导电率升高. 但是, 纳米粒子的加入量过大时反而引起NCPE的离子导电率降低. 当纳米粒子填充量为w＝10%时, NCPE具有最高的室温离子导电率1.25×10^－3 S•cm^－1.     

Enhanced zinc ion transport in gel polymer electrolyte: effect of nano-sized ZnO dispersion

The effect of the dispersion of zinc oxide (ZnO) nanoparticles in the zinc ion conducting gel polymer electrolyte is studied. Changes in the morphology/structure of the gel polymer electrolyte with the introduction of ZnO particles are distinctly observed using X-ray diffraction and scanning electron microscopy. The nanocomposites offer ionic conductivity values of >10^?3 S cm^?1 with good thermal and electrochemical stabilities. The variation of ionic conductivity with temperature follows the Vogel–Tamman–Fulcher behavior. AC impedance spectroscopy, cyclic voltammetry, and transport number measurements have confirmed Zn²⁺ ion conduction in the gel nanocomposites. An electrochemical stability window from ?2.25 to 2.25 V was obtained from voltammetric studies of nanocomposite films. The cationic (i.e., Zn²⁺ ion) transport number (t ₊) has been found to be significantly enhanced up to a maximum of 0.55 for the dispersion of 10 wt.% ZnO nanoparticles, indicating substantial enhancement in Zn²⁺ ion conductivity. The gel polymer electrolyte nanocomposite films with enhanced Zn²⁺ ion conductivity are useful as separators and electrolytes in Zn rechargeable batteries and other electrochemical applications.     

Dielectric properties of sols of silver nanoparticles capped by alkyl carboxylate ligands

Sols of silver nanoparticles in toluene were studied by broadband dielectric spectroscopy (10⁻³–10⁵ Hz). The frequency dependences of the specific alternating current (ac) conductivity and the complex electric modulus were used to estimate the temperature/frequency intervals of long- and short-range charge transfer occurs, respectively. A considerable increase (by more than 30 °C) in the Vogel temperature T ₀ and the glass transition temperature T _g in sols compared with the pure solvent was found. It can be hypothesized that these cooperative effects reflect the initial stage of the superlattice formation. Although the dielectric characteristics of sols are generally controlled by the conductivity relaxation, the dielectric response was observed in the high-frequency range (1–10³ Hz) at low temperatures (from −50 to +10 °C). This response results from the presence of nanoparticles in solution. It is supposed that the relaxation is caused by the motion of ion impurities on the Ag nanoparticle surface within the carboxylate ligands shell. The dielectric properties of films strongly depend on both the characteristics of nanoparticles and the conditions of the film preparation. Like in sols, the direct current (dc) conductivity and the dielectric response of Ag nanoparticles in films are due to ion impurities.     

A new methodology for producing pyrocarbon composites containing zerovalent iron nanoparticles

A magnetic pyrocarbon composite containing nanoparticles with an overwhelming predominance of zerovalent iron has been synthesized. The nanocomposite has a core–shell–matrix structure in which Fe⁰ nanoparticles with an average size of 50 nm are located in the pyrocarbon matrix and coated with a ferrite shell preventing their aggregation and oxidation. The composite is distinguished for its high thermal stability, magnetic properties 59 G cm³/g, and electrical conductivity as high as that of graphite.     

A proposed model to predict thermal conductivity ratio of Al2O3/EG nanofluid by applying least squares support vector machine (LSSVM) and genetic algorithm as a connectionist approach

In this study, a model is proposed by applying the least squares support vector machine (LSSVM). In addition, genetic algorithm is used for selection and optimization of hyperparameters that are embedded in the LSSVM model. In addition to temperature and concentration of nanoparticles, the parameters which are used in most of the modeling procedures for thermal conductivity, the effect of particle size is considered. By considering the size of nanoparticles as one of the input variables, a more comprehensive model is obtained which is applicable for wider ranges of influential factor on the thermal conductivity of the nanofluid. The coefficient of determination (R²) for the introduced model is equal to 0.9902, and the mean squared error is 8.64 × 10^?4 for the thermal conductivity ratio of Al₂O₃/EG.

     

Facile synthesis of PbTe nanoparticles and thin films in alkaline aqueous solution at room temperature

A novel, simple, and cost-effective route to PbTe nanoparticles and films is reported in this paper. The PbTe nanoparticles and films are fabricated by a chemical bath method, at room temperature and ambient pressure, using conventional chemicals as starting materials. The average grain size of the nanoparticles collected at the bottom of the bath is ∼25 nm. The film deposited on glass substrate is dense, smooth, and uniform with silver gray metallic luster. The film exhibits p-type conduction and has a moderate Seebeck coefficient value (∼147 μV K⁻¹) and low electrical conductivity (∼0.017 S cm⁻¹). The formation mechanism of the PbTe nanoparticles and films is proposed.     

Properties of a nanocomposite polymer electrolyte from an amorphous comb-branch polymer and nanoparticles

Three fully amorphous comb-branch polymers based on poly(styrene-co-maleic anhydride) as a backbone and poly(ethylene glycol) methyl ether of different molecular weights as side chains were synthesized. SiO₂ nanoparticles of various contents and the salt LiCF₃SO₃ were added to these comb-branch polymers to obtain nanocomposite polymer electrolytes. The thermal and transport properties of the samples have been characterized. The maximum conductivity of 2.8×10^–4 S cm^–1 is obtained at 28 °C. In the system the longer side chain of the comb-branch polymer electrolyte increases in ionic conductivity after the addition of nanoparticles. To account for the role of the ceramic fillers in the nanocomposite polymer electrolyte, a model based on a fully amorphous comb-branch polymer matrix in enhancing transport properties of Li⁺ ions is proposed.     

Flower-like Spherical α-Ni(OH)2 Derived NiP2 as Superior Anode Material of Sodium-Ion Batteries

Transition metal phosphides (TMPs) are promising anode candidates for sodium-ion batteries, due to their high theoretical specific capacity and working potential. However, the low conductivity and excessive volume variation of TMPs during insertion/extraction of sodium ions result in a poor rate performance and long-term cycling stability, largely limiting their practical application. In this paper, NiP₂ nanoparticles encapsulated in three-dimensional graphene (NiP₂@rGO) were obtained from the flower-like spherical α-Ni(OH)₂ by phosphating and carbon encapsulation processes. When used as a sodium-ion batteries anode material, the NiP₂@rGO composite shows an excellent cycling performance (117 mA h g⁻¹ at 10 A g⁻¹ after 8000 cycles). The outstanding electrochemical performance of NiP₂@rGO is ascribed to the synergistic effect of the rGO and NiP₂. The rGO wrapped on the NiP₂ nanoparticles build a conductive way, improving ionic and electronic conductivity. The effective combination of NiP₂ nanoparticles with graphene greatly reduces the aggregation and pulverization of NiP₂ nanoparticles during the discharge/charge process. This study may shed light on the construction of high-performance anode materials for sodium-ion batteries and to other electrode materials.     

Synthesis and Characterization of Polypyrrole Nanoparticles and Their Nanocomposites with Poly(propylene)

Summary: Conducting polypyrrole (PPy) nanoparticles were synthesized via microemulsion polymerization. PP/PPy nanocomposites were prepared by melt-mixing of polypyrrole with polypropylene (PP) and processed with injection molding. Tensile tests have revealed that increasing amount of PPy increased the strength and the stiffness of the nanocomposite while limiting the elongation of PP. Thermal gravimetric analysis has showed that incorporation of PPy nanoparticles has improved the thermal stability of the nanocomposites. Increasing amount of PPy nanoparticles increases the conductivity of nonconductive PP up to 2,4.10⁻⁴ Scm⁻¹. The same techniques were used to characterize nanocomposites containing 2% w dispersant. Composites prepared with dispersant have involved smaller dimension PPy nanoparticles and exhibited improvement in some mechanical and thermal properties.     

氮掺杂碳层包覆金属钴颗粒与氮掺杂石墨烯纳米复合材料作为高容量锂离子电池负极材料

合成了一种石墨烯基纳米复合材料即：由氮掺杂碳层包覆的金属钴纳米颗粒,充分分散于氮掺杂的石墨烯表面。这种纳米复合材料进一步提高了石墨烯的导电性,增加了石墨烯的储锂容量。该材料被用作锂离子电池负极材料,在性能测试中展现了良好的循环性能,在以100 mA·g^-1的电流密度循环200圈后,放电容量高达950.1 mAh·g^-1,库伦效率约为98%。     

Preparation of Polypyrrole/Poly(methyl methacrylate) Core-Shell Nanoparticles in Four-Component Microemulsion Media

Electrically conductive polypyrrole (PPy)/poly(methyl methacrylate) (PMMA) core-shell nanoparticles were synthesized by two-step microemulsion polymerization. PPy core particles were prepared in a four-component microemulsion system, which was formed with surfactant cetyltrimethyl ammonium bromide (CTAB), cosurfactant n-pentanol, water, and pyrrole. Ferric chloride and iodine was added as the oxidant and the dopant, respectively. Then the PPy nanoparticles were coated with PMMA to prepare PPy/PMMA core-shell nanoparticles. The morphology of PPy/PMMA core-shell nanoparticles was characterized with transmission electron microscopy (TEM). Fourier transform infrared (FTIR) spectroscopy was used to characterize the structure of the samples. The electrical conductivities of samples were studied by a Hall effect testing instrument. Despite being coated with a layer of insulation, the conductivity of the composite PPy/PMMA core-shell nanoparticles could still reached to 7.856 × 10^?1 S/cm.     

氮掺杂碳层包覆金属钴颗粒与氮掺杂石墨烯纳米复合材料作为高容量锂离子电池负极材料

合成了一种石墨烯基纳米复合材料即：由氮掺杂碳层包覆的金属钴纳米颗粒,充分分散于氮掺杂的石墨烯表面。这种纳米复合材料进一步提高了石墨烯的导电性,增加了石墨烯的储锂容量。该材料被用作锂离子电池负极材料,在性能测试中展现了良好的循环性能,在以100 mA·g^-1的电流密度循环200圈后,放电容量高达950.1 mAh·g^-1,库伦效率约为98%。     

Spectroscopic and Discharge Studies on Graphene Oxide Doped PVA/PVP Blend Nanocomposite Polymer Films

Graphene oxide (GO) nanoparticles were synthesized by modified Hummers method. The synthesized GO nanoparticles were incorporated in polyvinyl alcohol/polyvinyl pyrrolidone (PVA/PVP) blend polymers for the preparation of nanocomposite polymer films by solution cast technique. Different characterizations such as XRD, UV–Vis and FTIR were carried-out on to the prepared nanocomposite polymer films. The thermal analysis of the films was studied by DSC. The morphology of PVA/PVP:GO polymer films confirms GO was exfoliated within the PVA/PVP matrix and also reveals the heterogeneous phase of nanocomposite polymer electrolyte systems. From the conductivity studies the highest conductivity of PVA/PVP: GO (0.45: 0.3) was found to be 8.05 × 10^–4 S/cm at room temperature. Solid state battery has been fabricated with the configuration of Mg⁺/(PVA/PVP:GO)/(I₂ + C + electrolyte) and its cell parameters were calculated for a constant load of 100 kΩ.     

Conductivity of Poly(pyrrole)‐Poly(styrene sulfonate) Core–Shell Nanoparticles

The dielectric properties of poly(styrene) nanoparticles decorated at their surfaces with poly(styrene sulfonate) [PSS] brushes and subsequently loaded with polypyrrole (PPy) were studied. These film‐forming materials which may serve as hole‐injection layers in organic light‐emitting diodes, exhibit a core–shell‐type morphology with a core of electrically insulating poly(styrene) and a shell consisting of a corona of PSS chains which form the matrix in which the electrically conducting complex of PPy and PSS is embedded. This conducting complex exists in form of domains of nanoscale dimensions. Thin compressed pellets of these nanoparticles were studied using mainly impedance spectroscopy. Measurements were carried out in the temperature range between 123 and 453 K and frequency range from 10^?1 to 10⁶ Hz. While earlier studies were centered around the effect of polypyrrole volume fraction on the conductivity films and pellets composed of these nanoparticles, the present study reveals in which way the conductivity can be modified by exchange of the mobile inorganic counter ions of PSS. Besides the free‐acid form (H⁺), the Li⁺‐, Na⁺‐ and Cs⁺‐salts of PSS were investigated. The PPy volume fraction was the same for all PPy/PSS core–shell nanoparticles. The distance for phonon‐assisted hopping between next‐neighbor polypyrrolium chains is influenced by the presence of these inorganic cations. For all samples containing PPy, a transition from insulating to conducting behavior in the range of 300‐350 K was found. Using the fluctuation‐induced tunneling model, the average tunneling distance, as well as the potential energy barrier separating neighboring conducting grains was estimated. Finally, a detailed analysis of the dielectric spectra suggests the localization length of the charge carriers to be about 0.33 nm.     

Electromagnetic nanocomposites prepared by cryomilling of polyaniline and Fe nanoparticles

The polyaniline (PANI)/iron nanocomposites have been prepared by high‐energy ball milling under cryogenic temperatures, namely cryomilling, of PANI with Fe nanoparticles. It takes 5 h to refine the Fe into an average grain size of 20 nm and to get homogeneously dispersed in PANI matrix. The obtained PANI/Fe nanocomposites have a maximum conductivity of 0.78 S cm^?1 after 2‐h cryomilling, whereas its coercivity increases monotonously with time in the range of experiment up to 10 h. It is found that the sizes of Fe particles have obvious effects on both electrical and magnetic properties. When compared with micrometer Fe particles as raw materials, Fe nanoparticles result in somewhat lower conductivity but a much higher coercivity exceeding 400 Oe. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1571–1576, 2008     

Electrostatic Interactions Leading to Hierarchical Interpenetrating Electroconductive Networks in Silicon Anodes for Fast Lithium Storage

Recently, the frequency of combining MXene, which has unique properties such as metal-level conductivity and large specific surface area, with silicon to achieve excellent electrochemical performance has increased considerably. There is no doubt that the introduction of MXene can improve the conductivity of silicon and the cycling stability of electrodes after elaborate structure design. However, most exhaustive contacts can only improve the electrode conductivity on the plane. Herein, a MXene@Si/CNTs (HIEN-MSC) composite with hierarchical interpenetrating electroconductive networks has been synthesized by electrostatic self-assembly. In this process, the CNTs are first combined with silicon nanoparticles and then assembled with MXene nanosheets. Inserting CNTs into silicon nanoparticles can not only reduce the latter‘s agglomeration, but also immobilizes them on the three-dimensional conductive framework composed of CNTs and MXene nanosheets. Therefore, the HIEN-MSC electrode shows superior rate performance (high reversible capacity of 280 mA h⁻¹ even tested at 10 A g⁻¹), cycling stability (stable reversible capacity of 547 mA h g⁻¹ after 200 cycles at 1 A g⁻¹) and applicability (a high reversible capacity of 101 mA h g⁻¹ after 50 cycles when assembled with NCM622 into a full cell). These results may provide new insights for other electrodes with excellent rate performance and long-cycle stability.