Superconducting and mechanical properties of YBCO-Ag composite superconductors

The measurements of electrical properties and X-ray structural analysis were made for sintered composite materials prepared by mixing the powders of the ceramic superconductor YBa₂Cu₃O_7–x (YBCO) and the powders of the pure metal element M with with M = Ni, Cu and Ag at 50 vol% proportions. The superconducting and mechanical properties were studied further on the YBCO-Ag system in the wide volume fractions 0 to 92%Ag. The onset of the superconductivity is found to occur even for samples containing more than 80 vol % Ag. The value of the critical current density is increased initially by adding silver. The mechanical strength against fracture is also improved. The X-ray structural analysis coupled with scanning electron micrographs revealed that silver and YBCO remain intact after sintering and that fine YBCO particles form continuous networks around homogeneously distributed silver particles. This explains well both superconducting and mechanical properties in the present YBCO-Ag composite system.     

Investigation of Transport Properties of Some Superconductor Nickel-Based Antiperovskite XNNi<Subscript>3</Subscript> (X = Mg,Al, Cu,Zn, Ga,Ag, Cd,In, Sn,Sb, Pt and Pb)

We report, in this work, a theoretical study of electronic and transport (thermoelectric) properties of some superconductor nickel-based antiperovskite XNNi₃ (X = Mg, Al, Cu, Zn, Ga, Ag, Cd, In, Sn, Sb, Pt and Pb) using first-principles calculations with the full-potential linearized augmented plane wave (FPLAPW) method based on the density functional theory (DFT) as implemented in the WIEN2k package. Electronic properties are calculated and show that the studied materials are of metallic type which is in good agreement with experimental data. The Seebeck coefficient, thermal conductivity, electrical conductivity and figure of merit were reported. The results obtained show that the zinc (Zn) and silver (Ag) materials are characterized by a high value of the figure of merit at room temperature (300 K) which is respectively 0.86 and 1.02 in a p-type region. In the case of the transition metals, the maximum values of S increase in going from the Pt atom to the Zn atom and then decrease for the Cd atom. Furthermore, the Wiedemann–Franz law which states that the ratio of thermal to electrical conductivity for metals is constant is well verified in this work. The electric conductivity values are almost invariant with the temperature except for the case of MgNNi₃ and AgNNi₃ compounds in which it increases with T slightly. So, the superconducting materials based on silver and zinc are the best for the thermoelectric applications at room temperature due to the very important value of the factor of merit and the Seebeck coefficient obtained.     

Effect of silver nanoparticles content on the various properties of nanocomposite hydrogels by in situ polymerization

A series of nanocomposite hydrogels (APEAg series gels) were prepared from acrylic acid, poly(ethylene glycol) methyl ether acrylate, and silver nanoparticles through in situ polymerization by UV irradiation. The effect of the content of silver nanoparticle on the properties of the nanocomposite hydrogels was investigated. Results showed that, with increasing of the content of the silver nanoparticle in the hydrogels, the crosslinking density and shear modulus of the hydrogel were not obviously changed, the electrical conductivities of the nanocomposite hydrogels increased, and their initial rate of Escherichia coli inactivation significantly increased, but their adhesive force only slightly decreased. These materials can be assessed as promising bioadhesive patch or wound-dressing material or electrical massage patch.     

Preparation of the Silver-Superconductor Composite by Deposition of the Silver Nanoparticles in the Bismuth Cuprate Superconductor

BiSCCO (Bi–Sr–Ca–Cu–O) is high temperature superconductor with a lot of possible applications. Interfaces between superconductors and metal conductors are one of the technological problems. In this work, silver-superconductor composite was prepared by using flow of silver nanoparticles suspension in DMF (N,N-dimethylformamide) through superconductor’s pore system. Silver nanoparticles were prepared by reaction of silver nitrate with DMF. Properties of prepared composite were measured by SEM charting, XRD and critical current measurements. SEM chart showed uniform distribution of silver across sample. XRD and critical current measurements validated superconducting properties of prepared composite. In the future, materials based on this method could be used as an interface between superconductors and metals or as a base for superconducting composite with much better mechanical properties.     

超导YBa2Cu3O7 +δ/硅橡胶复合材料的压敏与介电特性

采用YBa₂Cu₃O_{7 +δ}(简称YBCO)多晶陶瓷超导粉末与硅橡胶(110型)按不同质量比进行配料,经过特殊的制备工艺,合成不同含量的超导 YBCO/硅橡胶高分子复合材料,分别测量样品的压敏效应和介电特性。结果表明,在不同应力作用下,样品电阻值的变化范围在1～4个数量级。样品电阻值随测量温度的降低(300~50K)呈下降趋势,测量温度降到90K时,样品电阻值发生突变,但在9050K没有观察到超导零电阻现象。室温下,样品的介电常数随频率的增加(1 kHz~5 MHz)而减小,介电损耗随测量频率的增大先增大后减小。随着YBCO含量的增加,形成的超电容网络微观结构也就越多,样品的电阻逐渐减小电流加大,导致超电容中电解质的极化强度有所增加,两者共同作用的结果导致样品的介电常数、介电损耗均随着YBCO含量的增加而增大。     

超导YBa_2Cu_3O_(7+δ)/硅橡胶复合材料的压敏与介电特性

采用YBa_2Cu_3O_(+δ)(简称YBCO)多晶陶瓷超导粉末与硅橡胶(110型)按不同质量比进行配料, 经过特殊的制备工艺, 合成不同含量的超导YBCO/硅橡胶高分子复合材料, 分别测量样品的压敏效应和介电特性. 结果表明, 在不同应力作用下, 样品电阻值的变化范围在1～4个数量级. 样品电阻值随测量温度的降低(300~50 K)呈下降趋势, 测量温度降到90 K时, 样品电阻值发生突变, 但在90~50 K没有观察到超导零电阻现象. 室温下, 样品的介电常数随频率的增加(1 kHz~5 MHz)而减小, 介电损耗随测量频率的增大先增大后减小. 随着YBCO含量的增加, 形成的超电容网络微观结构也就越多, 样品的电阻逐渐减小电流加大, 导致超电容中电解质的极化强度有所增加, 两者共同作用的结果导致样品的介电常数、介电损耗均随着YBCO含量的增加而增大.     

Apparatus for calorimetric measurements of losses in MgB2 superconductors exposed to alternating currents and external magnetic fields

Inexpensive superconducting wires with low AC losses would open up for a large superconductor market in AC electrical power applications. One candidate for this market is the MgB₂ conductor. In the development of an AC optimized superconductor, high-quality measurements of the AC losses under application-like conditions must be available. This article describes an apparatus built for this purpose. The measurement method is calorimetric. The temperature increase of the superconductor sample is measured and compared to the temperature increase due to a heater with known heat input. The system is designed for measurements of losses due to magnetic fields combined with transport currents. Results from tests verifying the capabilities of the system are given, as well as from initial AC loss measurements on a tape-shaped MgB₂ superconductor.     

Long, highly-ordered high-temperature superconductor nanowire arrays

The preparation and electrical properties of high-temperature superconductor nanowire arrays are reported for the first time. YBa2Cu3O(7-delta) nanowires with widths as small as 10 nm (much smaller than the magnetic penetration depth) and lengths up to 200 microm are studied by four-point electrical measurements. All nanowires exhibit a superconducting transition above liquid nitrogen temperature and a transition temperature width that depends strongly upon the nanowire dimensions. Nanowire size effects are systematically studied, and the results are modeled satisfactorily using phase-slip theories that generate reasonable parameters. These nanowires can function as superconducting nanoelectronic components over much wider temperature ranges as compared to conventional superconductor nanowires.     

Facile synthesis of silver malonate conductive MOD ink for screen printing

At present, screen printing is the most widely used technique in the printed electronics industry and the printed pattern can satisfy certain electronic application requirements. Ink development is the most important part of the printing process. In this paper, a new particle-free MOD ink (MOD?=?metal–organic-decomposition) was synthesized from silver malonate, diethanolamine (DEA) and ethylene glycol (EG). Silver malonate was the precursor of silver. DEA was the complexing agent that maked silver malonate soluble. EG acted not only as a solvent to regulate the rheological properties of the ink, but also as a reducing agent to reduce silver ions. The decomposition temperature was reduced from 210 °C to about 100 °C by the formation of silver-amine complex, thus the selection range of substrate could be broadened. The ink was spread on the polyimide (PI) substrate by screen printing. The silver film was formed after heat treatment at 150 °C for 1 h and its electrical conductivity can reach 1.0?×?10⁴ S cm^?1, which corresponded to one sixty-third of the theoretical conductivity of the bulk silver (6.3?×?10⁵ S cm^?1).

     

Colored and functional silver nanoparticle-wool fiber composites

Silver nanoparticles utilizing the surface plasmon resonance effect of silver have been used to color merino wool fibers as well as imparting antimicrobial and antistatic properties to them to produce a novel silver nanoparticle-wool composite material. This is accomplished by the reduction of silver ions in solution by trisodium citrate (TSC) in the presence of merino wool fibers or fabrics. The silver metal nanoparticles simultaneously bind to the amino acids of the keratin protein in the wool fibers using TSC as the linker. The colors of the resulting merino wool-silver nanoparticle composites range from yellow/brown to red/brown and then to brown/black, because of the surface plasmon resonance effect of silver, and are tuned by controlling the reduction of silver ions to silver nanoparticles to give the required particle size on the fiber surface. In addition to the surface plasmon resonance optical effects, the silver nanoparticle-wool composites exhibit effective antimicrobial activity, thus inhibiting the growth of microbes and also an increase in the electrical conductivity, imparting antistatic properties to the fibers. Therefore, silver nanoparticles function as a simultaneous colorant and antimicrobial and antistatic agent for wool. Chemical and physical characterizations of the silver nanoparticle-merino wool composite materials have been carried out using scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, synchrotron radiation X-ray diffraction, atomic absorption spectroscopy, X-ray photoelectron spectroscopy, direct-current electrical conductivity measurements, wash-fast and rub-fast tests, and antimicrobial tests.     

The Effect of Silver Substitution in Bi1.7Pb0.3Sr2Ca2?xAgxCu3Oy

The effect of Ag substitution on the properties of high-temperature superconductor Bi_1.7Pb_0.3Sr₂Ca_2−x Ag _x Cu₃O _y system have been investigated. The electrical and structural properties of the samples, prepared by the conventional solid-state reaction method, have been characterized by X-ray diffraction (XRD), electrical resistance and scanning electron microscopy (SEM) studies. XRD analysis reveals a multiphase structure of the samples, whereas SEM micrographs indicate some morphological changes induced by silver addition. It was found that an increase of the amount of Ag₂O addition leads to an enhancement of the critical temperature and the percentage of Bi-2223 phase in the phase mixture.     

Influence of ferroelectric-electrode interfaces on the electrical properties of BaTiO3-CoFe2O4 magnetoelectric composites

In order to further investigate the influence of electrode types and preparation conditions on the electrical properties of magnetoelectric (ME) composite ceramics, layered BaTiO₃-CoFe₂O₄ (BTO–CFO) composites were prepared using tape casting method, and the effects of silver and aluminium electrodes on the electrical properties were studied. It is found that the different electrical properties of the ME composites are related to the ferroelectric-silver and ferroelectric-aluminium interfaces formed at the same annealing temperature, in which the former enhance the leakage current density, dielectric properties and AC conductivity, but lower the ferroelectric properties compared to the latter. Meanwhile, the electrical properties of the composite, especially leakage current and ferroelectric properties, are influenced by the silver electrode annealing temperature. In addition, space charges and polarons are responsible for the dielectric constant and AC conductivity of the ME composites, respectively.     

银粉性质对太阳能电池浆料的影响

作为传统化石能源的有效替代品,太阳能电池引起了学者们的广泛关注。导电银浆作为太阳能电池的重要原料,影响着太阳能电池的光电转换率和度电成本。银粉作为银浆中的导电相,其性能对银浆的电性能、流动性、粘附性等性质起着关键作用。近年来针对银粉的形态、尺寸、分散度、粒度分布和振实密度对导电银浆电性能的影响有较多研究。研究表明银粉的形态和粒径是决定银浆导电性、烧结质量等特性的主要因素;银粉的振实密度也是影响烧结厚膜的致密性以及电池的光电转化率的重要因素。在银粉制备过程中,不同种类的分散剂会影响银粉的分散性,从而影响银浆的细度、粘附性和电阻率。     

Silver content effect on rheological and electrical properties of silver pastes

The novelty of this work is laboratory formulation of environmentally friendly, water-based silver inks adapted for screen printing. The challenge was also to elaborate inks that can withstand temperatures as high as 900 °C. Indeed, when printed on ceramic substrate, they were sintered at these high temperatures. These inks can replace conductive silver pastes present in the market, today, and containing irritant solvents such as terpineol and other aromatic solvents. Besides, screen printing is considered as an additive technique, thus allowing reducing wastes. Furthermore, only with 72.5% silver, considered as low content compared to commercial inks (≥75%), prepared inks presented good electrical resistivity, 23 nΩ m, close to that of bulk silver resistivity, 16 nΩ m. Formulation of silver inks with spherical particles, 2–3 μm mean diameter, was performed. The aim of the study was to determine silver content effect on pastes rheological behaviour, lines properties (width, thickness and roughness) and electrical properties. Therefore, rheological behaviour of inks was studied; in particular, Casson and Bingham models were applied in order to determine the yield stress. Viscosity evolution as a function of shear rate was also determined. Besides, the thixotropic behaviour of inks was highlighted. Inks were then screen printed on alumina sintered substrates and cured at different temperatures during 15 min. Topography measurements were performed. Line resistivity as small as 35 nΩ m was measured on cured lines. These inks, printed on ceramic tapes, can be used to print microwave transmission lines, for which resistivities lower than 1 mΩ m are requested.     

Effect of different types of silver and epoxy systems on the properties of silver/epoxy conductive adhesives

In this study, the effect of amine adduct powder (AAP) on the electrical conductivity, thermal expansion, and flexural modulus of one-part system conductive adhesives are investigated. One-part system conductive adhesives are prepared using two types of silver (silver A and silver B) and different percentage of filler loadings, 10 vol.% ?40 vol.%. Silver A adhesive systems exhibit higher electrical conductivity with lower percolation thresholds, high flexural moduli, and low coefficients of thermal expansion (CTE) compared silver B adhesive systems. A comparison of the electrical conductivity and thermal expansion properties of the one part and two-part of silver A adhesives system is undertaken. The one-part silver A adhesives system shows high electrical conductivity and low CTE values compared to the two-part system. This is due to the higher cross linking density of the one-part system compared to that of the two-part system.     

Quench and Recovery Characteristics of Solid Nitrogen (SN2) Cooled YBCO Coated Conductor (CC) Tapes with Different Stabilizers

Recently, a cooling system using solid nitrogen (SN2) as a cryogen was suggested to enhance the thermal and electrical stabilities of high temperature superconductor (HTS) magnet applications, due to its large heat capacity. For the successful application of the SN2 cooling system to HTS devices, it is necessary to obtain sufficient data about the thermal and electrical characteristics of the SN2-cooled YBCO coated conductor (CC). Therefore, this study examined the thermal and electrical properties of YBCO CC tapes with different stabilizers in the presence and absence of SN2. The results clearly showed that the thermal and electrical stabilities of the YBCO CC tapes were drastically improved in the presence of the SN2, regardless of the stabilizer materials. Furthermore, copper was found to be more suitable as a stabilizer of YBCO CC tape in the SN2 cooling system than stainless steel.     

Effect of Silver Addition to Superconducting SmFeAsO1−x F x

We investigate the effect of silver addition to polycrystalline Sm-1111 superconductor. We show that Ag improves the phase homogeneity of the samples drastically reducing the weight of the low temperature, hence, leading to less fluorinated phases. The intragranular critical current density is enhanced by adding a small amount of Ag in all pinning regimes but a higher content of Ag leads to a decrease of this quantity. A tentative explanation for this dependence is proposed.     

Electrical properties of silver paste prepared from nanoparticles and lead-free frit

Recently, PbO containing glass systems in commercial silver paste have been used due to their low glass transition temperature, good thermal and electrical properties. However, PbO is a hazardous material to both health and the environment. In this study, Pb-free silver paste was prepared by mixing commercial silver powder and silver nanoparticles. The commercial powder has an average particle size of 1.6 microm. The silver nanoparticles with particles size of 20-50 nm were synthesized by a chemical reduction method using surfactant. Pb-free frit was added into the mixed silver powder as the amounts of 3, 6 and 9 wt%. Using the obtained paste, thick films were fabricated by a screen printing on alumina substrate and the films were fired at temperature from 400 to 550 degrees C. The films had thickness of 6-11 microm and sheet resistivity of about 4-11 microomega cm.     

Preparation and sintering properties in air of silver-coated copper powders and pastes

In this paper, uniform and well dispersed silver-coated copper powders were prepared by replacing reaction at first. The structure and properties of the bimetallic powders were investigated by XRD, SEM and TGA. It was found that anti-oxidization of the silver-coated copper powders increased with the increase of the silver content slightly and a dense coating surface was observed at Ag content of 53.9 wt%. Furthermore, the pastes with relatively low silver content which were prepared from silver-coated copper powders, displayed high conductivity similar to pure silver even after sintering in air. And their sintering properties were also investigated at different temperature in air atmosphere. The film exhibits good electrical properties at sintering temperature between 800 and 900 °C. When the paste from silver-coated copper powder with Ag content of 53.9 wt% was printed on Al₂O₃ substrate and sintered at 800 °C in air, the sheet resistance of the film is 0.036 Ω/□ only.     

Effect of silane-based coupling agent on the properties of silver nanoparticles filled epoxy composites

The study aims at investigating package materials based on combinations of nanometallic particles and polymers for microelectronics. Understanding the behaviors of this combination materials and being able to tailor them to give a desired composite properties are of great importance. In this present study, silver nanoparticles (Ag) were used as metallic conductive filler and it was applied in epoxy resin to produce silver nanoparticles filled epoxy composites. The electrical and flexural properties of silver nanoparticles-filled epoxy composites, as functions of filler loading (0–8 vol.%) were investigated. Furthermore, study on the effect of silane coupling agent treatment on the electrical and flexural properties of Ag nanoparticles-filled epoxy composites was carried out. The electrical property characterization indicates that the insulator-to-conductor transition occurred at percolation threshold of 5 vol.% of Ag. Treatment of Ag by silane-based coupling agent exhibited remarkable improvement in electrical and flexural properties of the composite system. Morphological studies have shown noticeable improvement in filler dispersivity in the treated composite system compared to those untreated system. FTIR analysis indicates the existence of –Si–O–C–, C–N and Si–H silane bonding in the treated composites, which subsequently improve the adhesion and enhance the electrical and flexural properties of the treated composite system.