Numerical Simulation of Free Convection in a Three-Dimensional Enclosure Full of Nanofluid with the Existence a Magnetic Field

A numerical analysis was performed to study the influence of a magnetic field in free convection in a cube full with nanofluid. To solve the equation, we appeal to finite volume method. The SIMPLEC algorithm is used for pressure-velocity coupling. All walls are adiabatic, except for the left and right walls that are heated differently. The effects of the Rayleigh and Hartmann numbers, as well as the volume fraction of nanometric particles were studied. Results are conveyed in the form of isotherms, streamlines, velocity curves and Nusselt numbers. It has been shown that as the percentage of nanoparticles increases and the number of Rayleigh increases, heat transfer improves. Hartman number has considerable influence on hydrodynamic and thermal field.

Effect of Calcium Synthetic Hydro Silicate Additives on the Cement Systems’ Technological Characteristics

The use of finely dispersed fillers for cement concrete is accompanied not only by the cement binder saving, but also by a change in the technological characteristics of the cement mixtures. Depending on the nature of the additive used, both a positive and a negative water-reducing effect can be observed. The nature of the synthetic calcium silicates additives’ effect obtained by the method of sucrose-modified calcium hydro silicates thermolysis on the technological properties of the cement systems is considered. The independent methods determined the polymodal nature of the calcium silicates dispersions. The effect of the various dimensional scales particles on the technological properties of the cement system is determined. Micron particles affect the powder mixture compaction, the optimal content of calcium silicate additives is 20–40%. Nanometric particles, as well as residual freely extractable sucrose, determine the plasticizing effect of the synthetic calcium silicates additives introduction, the maximum manifestation of which is observed when the additive content is 20%. The visco-plastic properties of the “cement - synthetic calcium silicates” system’s mixtures were evaluated at various additive contents.

Supercritical Assisted Electrospray: An Improved Micronization Process

A new process is proposed that can largely improve classical electrospray (ESPR) atomization, thanks to the addition of supercritical CO2 (SC-CO2) to the liquid mixture, in which a polymer is dissolved, forming an expanded liquid. The consequent reduction of surface tension and viscosity allows the production of micrometric or nanometric particles of controlled size and distribution at a production rate up to one hundred times that of the traditional process. The new process was applied to particle generation from a very high molecular weight polyvinylpyrrolidone (PVP) and tested at different polymer percentages by weight and at different pressures. Repeatable microparticle diameters and distributions were obtained, ranging between 0.55 and 2.25 µm at PVP concentrations from 1 to 5% w/w and pressures between 80 and 120 bar.

Development of a hybrid metal-oxides (Li2O-Al2O3-Al3Fe-Al3Fe5O12) reinforced polycaprolactone composite

ABSTRACTThis paper addresses the chemical synthesis and characterization of a composite formed by Li2O-Al2O3-Al3Fe-Al3Fe5O12/PCL which were obtained by the process of reduction of ferric chloride (FeCl3) with lithium aluminum hydride (LiAlH4) in an open atmosphere. The goal of the development of this hybrid material was to perform a superparamagnetic material with several potential applications. The results of the characterizations by scanning electron microscopy (SEM) and vibrating sample magnetometer showed a Li2O-Al2O3-Al3Fe-Al3Fe5O12 “desert rose stone”-like morphology 3D hierarchical powders formation when particles were sintered at 850 °C. Homogeneous nanometric particles after calcination at 1100 °C were observed. X-ray diffraction analysis were performed to determine their composition. Subsequently, the superparamagnetic powders were added by dispersion in a polycaprolactone (PCL) matrix, and then, were evaluated by SEM for the observation of their morphologies. The composite material presented a polymer network with an opened structure, a well dispersion of the oxides particles into the interstices with irregular topography and reliefs.

Thermal conductivity difference between nanofluids and micro-fluids: Experimental data and theoretical analysis using mass difference scattering

In this work, an experimental campaign on different nanofluids and micro-fluids, obtained by the dispersion of three different metal oxides (CuO, ZnO, and TiO2) with diathermic oil or deionized water has been carried out, in order to extend phonon theory to liquids, as already done in a previous work on Al2O3. Thermal conductivity of stable samples was evaluated by time. The experimental results on thermal conductivity of stable micrometric and nanometric particles suspensions in oil and water showed a further proof of mass difference scattering phenomenon.

PP/EPDM Polymeric Compounds Dynamically Cured Compatibilized and Reinforced with Nanoclay

This paper presents the development of dynamically cured polymer composites and nanocomposites based on plastomer - PP (polypropylene) and EPDM elastomer (ethylene-propylene-diene-terpolymer) compatibilized and reinforced with nanometric particles-MMT (montmorillonite, chemically modified layered clay) in two stages, by extrusion-granulation and mixing. Nanoparticles increase the thermal resistance of dynamically cured polymer nanocomposites. By means of compatibilization and dynamic curing, elastomer particles - EPDM are more easily dispersed in the mixture. The materials obtained were tested physicomechanically (Melt Flow Index) and morpho-structurally (FT-IR and DSC).

Generation of Latex Films on Glassy Substrates by Evaporation Induced Self-Assembly (EISA) Process

It will be discussed in this work how it is possible to produce latex films by evaporation induced self-assembly (EISA) process. Latex beads were synthesized in a cylindrical flask without N2flow. The polymerization process of styrene happens at water as solvent and with the presence of persulfate potassium as initiator. The final product was a dispersion of spherical nanometric particles (ɸ = 0.47 ± 0.06μm) whose concentration can be changed from 0.5 to 10% (V/Vo). These dispersions were spread on glassy substrates at 50°C over a square area (~1cm2) with control of solvent evaporation. The films are transparent and they show the formation of nanowire structures by scanning electron microscopy (SEM) characterization. Such structures were associated to high affinity of latex beads particles to form cylindrical arrangements due to presence of O2during their synthesis. It has been concluded that this self-assembly structure can be very worthy for generation of functional devices like sensors, solar cells and biomaterials.