Nanotechnology in Science and Engineering

Factors for the Electric Field-Directed Assembly of Gold Nanowires from an Electrolysis Process

Zheyao Wang — 2018-06-20

Gold nanowires have been fabricated between two Pt electrodes by applying sinusoidal signal voltage and DC offset from an electrolysis process. Factors for the growth and morphology of the nanowires include the frequency and magnitude of AC and DC offset, growing time, and distance between the electrodes.

Some Properties of Triclinic System Materials

Fae’q A. A. Radwan — 2018-07-02

The norm of elastic constant tensor and the norms of the irreducible parts of the elastic constants of the triclinic system materials (Ammonium Tetroxalate Dehydrate, NH4H3(C2O4)2.2H2O, Copper Sulfate Pentahydrate, CuSO4.5H2O and Potassium Tetroxalate Dehydrate, KH3C2O4.2H2O) were calculated. The relation of the scalar parts norm and the other parts norms and the anisotropy of these materials were presented. The norm ratios were used as a criterion to present the anisotropy degree of the properties of these materials.

Optimization of Synthesis Parameters for the Formation of Promising Y3Ba5Cu8O18 Compound

Slimani Y — 2018-07-02

In the present work, the influence of various heat treatment conditions such as sintering temperature, duration and compacting pressure, on the structure, microstructural and electrical properties of the new Y3Ba5Cu8Oy (noted Y-358, YBCO family)superconducting material was investigated. Samples were produced by means of the standard solid-state reaction process. The structural and microstructural characterizations of the various synthesized products were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). The electrical resistivity as a function of temperature was also performed and examined. The analyses show that the optimal structural formation was achieved for the product prepared at 950°C for 48 h. This sample exhibited a superconducting transition temperature (Tco) value around 95 K.

Some Physical Properties of Different Compositions of Alums

Fae’q A. A. Radwan — 2018-07-20

The norm of elastic constant tensor and the norms of the irreducible parts of the elastic constants of different compositions of alums (cubic systems) are calculated. The relation of the scalar parts norms and the other parts norms and the anisotropy of these alums are characterized. The norm ratios are used to study the isotropy and anisotropy of these alums.

Effect of Sintering Temperature on the Microstructure and Electrical Properties of Y3Ba5Cu8O18 Superconducting Material

Slimani Y — 2018-10-21

In the present work, the influence of various sintering temperatures on the microstructural and electrical properties of the new Y3Ba5Cu8Oy (noted Y-358) superconducting material was investigated. Samples were prepared through the solid-state reaction method. The structure and microstructure of the various synthesized samples were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). The measurements of the electrical resistivity as a function of temperature were also performed and examined.

On the Nature of the Ion-Specific Effects

Stoyan I. Karakashev — 2018-07-13

This article reports the effect of the counter-ions on the ionic surfactant adsorption layer and its relation to the stability of colloidal dispersions. The adsorption theory of Davies about the ionic surfactant monolayer is revisited and explored. Adsorption at the water|gas interface is compared to the water|oil interface, and the applicability of Langmuir’s concepts for distributing pressure and liquid expanded film is shown. The detailed analysis clarifies the effects of the medium and the surfactant structure (hydrocarbon chain length, the nature of the container) on the adsorption. Extra accent is put on the Hofmeister effect of the counter-ion on the adsorption of ionic surfactants. The simple model of the van der Waals interaction of an ion with the interface was revisited, so taking into account the quantitative interpretation of the Hofmeister effect on the adsorption parameters. The core of this model stands a quantity called ion specific adsorption energy ui0, which is related straightforwardly to basic ion characteristics, and is calculated for the counter-ions typically used in practice. An extended comparison with tensiometric and other experimental data demonstrates the usefulness of the theoretical models. The universality of the concept for the ion specific adsorption energy ui0 is further demonstrated by considering the role of the Hofmeister effect in two other phenomena, related to ionic surfactants: the disjoining pressure on thin liquid films and the stability of foams and emulsion. Unfortunately, the experimental data on the stability of foams and emulsions shows an opposite trend to our theoretical expectation – the stability increases upon the increase of the absolute value of the of the specific adsorption energy of the counter-ions in the water|gas or water|oil interfaces. It was shown abnormal effect of the potassium counter-ion on the stability of foams. The later either act as a foamer or de-foamer depending on its
concentration. To clarify the nature of this effect further investigations are required.