Certification method for standard thermoresistive voltage transducers

Translated from Izmeritel'naya Tekhnika, No. 2, pp. 25–27, February, 1989.     

Certification of Class I standard spectrometric gamma sources

Conclusions High accuracy can be obtained with the relative method of determining-radiation activity on a scintillation counter only when the samples are precisely positioned, especially for small distances between the source and the radiation detector. Because of the low levels of activity of the standards (approximately 0.5 Ci) SSGS must be calibrated for small distances between the source and the detector. Additional measurements taken with the source rotated through 180 greatly reduce the systematic error caused by inaccurate positioning. A large scintillation crystal of NaI(T1) used as a detector reduces systematic error in relative measurements owing to the sources shifting from the detector axis and to variations in the dimensions of the radioactive spots of different sources.Translated from Izmeritel'naya Tekhnika, No. 2, pp. 77–80, February, 1971.     

V带静电特性检测

根据国际标准ISO1813环形V带———静电特性及检测方法 ,设计出V带静电特性检测装置 ,并对几种不同材料配方的V带进行了检测和分析 ,为胶带在特殊工况下的应用提供了依据     

Graphene-wrapped hybrid spheres of electrical conductivity

We present a simple approach for the fabrication of monodisperse electroconductive hybrid spheres using graphene sheet-wrapping via ionic interaction-based self-assembly. The graphene sheets partially charged with anion, which were prepared by controlled chemical reduction of graphite oxide, were mixed with monodisperse polymer nanospheres containing cationic surface charge to form ionic self-assembled hybrid spheres of core-shell structure. The resulting graphene-wrapped hybrid spheres were found to have graphene layer thickness of ca. 10 nm and to exhibit electrical conductivity of 1.33-4.21 S/m as well as monodisperse distributions in shape and diameter.     

High-temperature electrical conductivity of aluminium nitride

The electrical conductivity of hot-pressed polycrystalline aluminium nitride doped with oxygen and beryllium was measured as a function of temperature from 800 to 1200° C and over a range of nitrogen partial pressure from 10² to 10⁵ Pa. The effect of beryllium dopant, the independence of conductivity from nitrogen partial pressure, and the observed activation energy suggested extrinsic electronic species or aluminium vacancies as charge carriers. Polarization measurements made with one electrode blocking to ionic species indicated that the aluminium nitride with oxygen impurity was an extrinsic electronic conductor.     

Experimental evaluation of electrical conductivity of microtubules

Microtubules (MTs) are self-assembled proteinaceous filaments with nanometer scale diameters and micrometer scale lengths. Through conductivity measurements in microchannels we shed some light on electrical properties of microtubules. Measuring electrical resistance we were able to detect the dynamic disassembly of MTs and determine an upper limit for the electrical conductivity of MT. The measurements yielded the value of 90 Ω⁻¹ m⁻¹ as the upper limit for the conductivity of MTs, which is in the order of conductivity observed in inorganic intrinsic semiconductors.     

The electrical conductivity of some azine compounds

Correlation of the molecular structure and thermal study of the electrical conductivity of benzaldazine (BA) and its NO₂-derivatives were carried out. The values of the activation energies, obtained from the electrical conductivity measurements, as well as the energy gaps calculated from ultra violet (u.v.) and visible spectra obtained either in liquid or in solid forms indicate that all compounds behave like a semiconducting material. Both n*s and *s were found to be the main sources participatiog in the cooduction processes.     

Effective thermal conductivity and electrical conductivity of anisotropic solids of low porosity

Equations are derived to determine the effective thermal and electrical conductivities of anisotropic media of low porosity. The influence of porosity on the thermal and electrical conductivities of anisotropic ternary alloys is established.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 30, No. 4, pp. 686–692, April, 1976.     

DC electrical conductivity of some Cd-Ge-As glasses

Results of measurement of d.c. electrical conductivity σ from 85 to 550 K are reported for eleven glass compositions of the Cd-Ge-As system. Three regions are seen in theσ-T data of all these glasses. In region I (85 to 140 K),σ is essentially constant and independent of temperature. In region II (200 to 430 K),σ is thermally activated with a single activation energy. In region III (>430 K) a sudden increase is seen inσ with temperature. From an analysis of the results, it has been possible to identify the mechanism of hopping conductivity among localised ‘defect’ states with region I, normal band type conductivity due to carriers excited to the extended states with region II and thermally assisted memory switching with region III. In the composition dependence ofσ and ΔE for the CdGe _x As₂ glasses, special features are seen at the composition Cd_28·57 Ge_14·28 As_57·15, which has equal mol fractions of CdAs₂ and CdGeAs₂. For the Cd₂Ge-As glasses also, a maximum in ΔE and a minimum inσ are seen at this composition.     

Frequency-dependent electrical conductivity of nanocrystalline SnO2

Nanocrystalline SnO₂ with a crystallite size of 3–4 and 5–6 nm has been prepared by a sol-gel process in aqueous solution. Its ac electrical conductivity has been measured in dry air at a temperature of 200°C. The observed frequency dependence of its conductivity has been interpreted in terms of the random potential barrier model. The data obtained indicate that the transport properties of the material are dominated by hopping conduction through disordered crystallite boundaries.     

Certification of normal samples of magnetic materials at high frequencies

Conclusions In measuring the magnetic parameters of samples, primarily in certifying normal samples by using sections of coaxial lines, it is necessary to select the optimum length of the line in relation to the available scales on the admittance (impedance) meter and the values of the measured parameters; introduce corrections for losses in the line either by calculations or graphically for materials with low losses; and allow for the electrical parameters of ferrites or magnetodielectrics (their complex permittivity), especially if the normal samples do not fulfill conditions (19).Translated from Izmeritel'naya Tekhnika, No. 12, pp. 42–45, December, 1970.     

俄罗斯电气类产品认证体系及适用模式

目前,俄罗斯国内有16个强制认证体系,包括俄罗斯国家标准认证(GOST R认证)体系、卫生防疫评估体系、防火安全认证体系、通信产品认证体系、工业安全和技术监管体系、建筑和设计认证体系、机械交通工具和拖车认证体系、动植物监管体系、生态监管体系、信息保护手段许可及认证体系等.     

Field monitoring of electrical conductivity of cover-zone concrete

A sensor system, developed in a previous laboratory study [McCarter WJ, Emerson M, Ezirim H. Properties of concrete in the cover-zone: developments in monitoring techniques. Mag Conc Res 1995;47(172):243–51; Chrisp TM, McCarter WJ, Starrs G, Basheer PAM, Blewett J. Depth related variation in conductivity to study wetting and drying of cover-zone concrete. Cem Conc Comp 2002;24(5):415–27], is used to obtain the spatial distribution of electrical conductivity within the cover-zone of concrete specimens subjected to a range of natural exposure conditions. The testing methodology enables in-situ monitoring of the electrical conductivity and technical issues relating to site measurements are discussed. The work also highlights the need for continual monitoring of the covercrete as the electrical conductivity changes with time, depth and environment.     

Ternary polyurethane nanocomposites with remarkable electrical conductivity

ABSTRACT

A series of polyurethane composites with constant 5 wt-% loading of 2D graphene nanosheets and varying levels of 1D silver nanowire (AgNW) were prepared by a solution mixing method. The electrical conductivity of composite films was measured using a 4-point probe method. An extremely high conductivity of 3,657?S?cm^–1 was achieved with a polyurethane composite containing 25?wt-% AgNW and 5?wt-% graphene, confirming that a combination of AgNW and graphene is very effective in producing conducting pathways to achieve high conductivity. The incorporation of AgNW and graphene was confirmed by scanning electron microscopy and energy dispersive spectrometry. Additionally, the results of tensile strengths and thermogravimetric analysis showed that the as-prepared polyurethane composite films possessed good mechanical properties and stable thermal properties.