Weight Fraction Of Nanoparticles Research Articles

An experimental investigation on the effect of Al 2O 3–H 2O nanofluid on the efficiency of flat-plate solar collectors

In the present work the effect of Al 2O 3–water nanofluid, as working fluid, on the efficiency of a flat-plate solar collector was investigated experimentally. The weight fraction of nanoparticles was 0.2% and 0.4% and the particles dimension was 15 nm. Experiments were performed with and without Triton X-100 as surfactant. The mass flow rate of nanofluid varied from 1 to 3 Lit/min. The ASHRAE standard was used to calculate the efficiency. The results show that, in comparison with water as absorption medium using the nanofluids as working fluid increase the efficiency. For 0.2 wt% the increased efficiency was 28.3%. From the results it can be concluded that the surfactant causes an enhancement in heat transfer.

Assessment of heat dissipation performance for nanofluid

Abstract A thermal management system that governs the operating temperature is crucial to green energy/power sources. This paper evaluated the feasibility of alumina (Al 2 O 3 )/water nanofluid for these cooling systems using an air-cooled heat exchanger for heat dissipation. The Al 2 O 3 /water nanofluid was produced by the direct synthesis method at the concentrations of 0.5, 1.0, and 1.5 wt.%. The experiment aimed for measuring the heat dissipation performance at the above weight fractions, fluid flow rates (1.8, 2.1, and 2.4 L/min), and sample temperatures (30, 40, 50, and 60 °C) within the operating range of green energy/power sources. Firstly, the thermal conductivity was measured to prove the enhancement of heat dissipation. After formulating the solid/water parameters and uncertainty analysis, key issues were investigated by controlling the fluid temperatures, flow rates, and weight fractions of nanoparticles. The experiments show that the maximum enhancement of heat exchange compared with distilled water is of 40% at high weight fraction of nanoparticles (1.5 wt.%) and low nanofluid temperature (30 °C). Moreover, the maximum enhanced ratio of pumping power occurs at high temperature of 60 °C and high weight fraction of nanoparticles (1.5 wt.%). Through the experiments, one can obtain the key factors to optimize a thermal management system of green energy/power sources in the near future.

Investigation on crystallization of TiO2–water nanofluids and deionized water

Two titania–water (TiO2–water) nanofluids were prepared by dispersing TiO2 nanoparticles in rod shapes (rutile TiO2) and in spherical shapes (anatase TiO2) into deionized water. The effect of the TiO2 nanoparticles on the crystallization behaviors of the nanofluids were investigated using differential scanning calorimetry (DSC). The weight fraction of the TiO2 nanoparticles was 0.05%, 0.30% and 0.70%. The experimental results show that in the cooling rate range of 1.5–9.0°C/min, the nanofluids with rutile TiO2 nanoparticles had higher crystallization temperatures compared with deionized water and the nanofluids with anatase TiO2 nanoparticles, and the heat of crystallization of the rutile TiO2 nanofluid was larger than that of the anatase TiO2 nanofluid. It is found that the rutile TiO2 nanofluid is more suitable than the anatase TiO2 nanofluid for ice storage system under the experimental conditions. Moreover, some unexpected data were obtained, which show that the shapes of the crystallization temperature curves of the nanofluids were like symbols of inverse “N” at 0.5–9.0°C/min, and that the crystallization temperatures of some of the nanofluids were lower than that of the deionized water at low cooling rates. The mechanisms for the unusual phenomenon were discussed.

Single-step synthesis and characterization of single-walled carbon nanohorns hybridized with Pd nanoparticles using N 2 gas-injected arc-in-water method

Single-walled carbon nanohorns (SWCNHs) hybridized with palladium (Pd) nanoparticles were synthesized by a single-step gas-injected arc-in-water method (GI-AIW) with a Pd wire inserted inside the anode hole. In the arc zone, carbon and Pd were vaporized simultaneously, leading to the formation of hybrid material of SWCNHs and Pd nanoparticles due to effective quenching. Based on TEM and CO chemisorption analyses, Pd nanoparticles were found to be embedded inside SWCNH aggregates. The size of Pd nanoparticles, determined by X-ray diffraction, was in the range of 3–6 nm when Pd wires with diameters of 0.1 and 0.3 mm were used. Using a Pd wire with a diameter larger than 0.5 mm results in larger Pd nanoparticles which tend to be exposed to the outer surface of the hybrid material. According to thermogravimetric analyses, the weight fraction of Pd nanoparticles is increased by increasing the Pd wire diameter although the yield of Pd nanoparticles decreased. SWCNHs hybridized with dispersed Pd nanoparticles, synthesized with 0.1 mm Pd wire, exhibited strong anti-oxidation resistance with a highly graphitic structure.

Synthesis and catalytic properties of alkanethiolate-capped Pd nanoparticles generated from sodium S-dodecylthiosulfate

This article presents a synthetic method for alkanethiolate-functionalized Pd nanoparticles that are efficient catalysts for the isomerization of allyl alcohol to propanal. Pd nanoparticles are produced by the borohydride reduction of K2PdCl4 in toluene/H2O using sodium S-dodecylthiosulfate as a source for the stabilizing ligands. The nanoparticles are characterized by 1H NMR, Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), UV-vis absorption spectroscopy, and thermogravimetric analysis (TGA). These analyses suggest that the monolayer capped Pd nanoparticles from sodium S-dodecylthiosulfate are quite comparable in composition (dodecylthiolate) and core size from those previously prepared from dodecanethiol. However, the catalytic activity of Pd nanoparticles generated from S-dodecylthiosulfate is found to be much greater than that of Pd nanoparticles prepared from dodecanethiol. The increased catalytic activity of Pd nanoparticles is likely to be due to the lower ligand density (organic weight fraction) of Pd nanoparticles generated from S-dodecylthiosulfate. The catalytic activity of PdAu nanoparticles on the isomerization of allyl alcohol is also demonstrated.

Physical aging of polystyrene/gold nanocomposites and its relation to the calorimetric Tg depression

The aim of this work is to study the effect of gold nanoparticles on the segmental dynamics, glass transition (Tg) and physical aging of polystyrene (PS). To do so, PS/gold nanocomposite samples containing 5 and 15 wt% of 60 nm spherical gold nanoparticles, surface-treated with thiolated-PS, were prepared. The segmental dynamics of PS, as measured by means of broadband dielectric spectroscopy (BDS), was found to be unchanged in the presence of gold nanoparticles. Conversely, the calorimetric Tg of PS was shown to decrease with increasing the amount of gold nanoparticles in the samples. Furthermore, by measuring the amount of recovered enthalpy of PS—by means of DSC—after annealing at temperatures below Tg for various aging times, the physical aging was shown to speed up with increasing the nanoparticles weight fraction, i.e. the amount of PS/gold interface in the hybrid material. Thus, the main conclusion of our work is that PS molecular mobility and the out-of-equilibrium dynamics are markedly decoupled in these nanocomposites. The significant effect of the amount of PS/gold interface on both the physical aging rate of PS and the depression of the calorimetric Tg in the presence of nanoparticles is quantitatively accounted for by a model based on the diffusion of free volume holes towards polymer interfaces, with a diffusion coefficient depending only on the molecular mobility.

Preparation and thermal properties of polystyrene/silica nanocomposites

A series of polystyrene/silica nanocomposites with different inorganic nanofiller content were prepared by evaporating of toluene solvent. The weight fraction of silica nanoparticles of an average diameter of 7 nm treated with hexamethyldisilazane was varied (2, 5, 10, 15 and 30 wt.%). The polystyrene nanocomposite morphology was studied by scanning electron microscopy. The thermal stability of the samples was determined using thermogravimetry, coupled with differential scanning calorimetry. The influence of the filler content on glass transition temperature of polystyrene/silica nanocomposites was followed by differential scanning calorimetry. It was found that the polystyrene glass transition temperature was influenced by the hydrophobic silica content. A mathematical method to describe the glass transition temperature dependence on the polystyrene/silica ratio is proposed. According to the experimental results and calculations, the highest thermal stability of the nanocomposite belongs to 18% silica content.

Reinforcement of Polyamide 66 with Polyoxometalates Nanoparticles through the <i>In Situ</i> Sol-Gel Method

This paper investigated the influence of the nanoparticles on the thermal and mechanical properties of PA66 and various nanocomposites containing different weight fraction of polyoxometalate nanoparticles were prepared. The structural features of the nanocomposite are characterised using TEM, ATR-FITR, DMA and TGA. The results show that nanoparticles, around 5.5 nm in size are well-dispersed inside the polymer matrix. The physical interaction between PA66 and the POM nanoparticles led to a significant effect on the thermal and mechanical properties of PA66. Dynamic mechanical analysis (DMA) revealed a considerable change in the storage modulus of the nanocomposite. With only 1wt% of POM, the storage modulus of PA66 at 25oC is enhanced by 45%. Furthermore, the thermal stability of the nanocomposite is also enhanced, possibly owing to the absorption of oxygen by the nanoparticles. The results demonstrated that the obtained nanocomposites, via the combination of the excellent mechanical and thermal properties of PA66 with the intriguing optical, electrical and chemical properties of POM, were promising for catalytic, energy storage, memory devices, automobile and construction applications.

Templated preparation of porous magnetic microspheres and their application in removal of cationic dyes from wastewater

Porous magnetic microspheres with large particle size (350–450 μm) were prepared with sulfonated macroporous polydivinylbenzene as a template. The preparation process included ferrous ion exchange and following oxidation by hydrogen peroxide. The results showed that the weight fraction of magnetic nanoparticles exceeded 20 wt% in microspheres after the preparation process was repeated three times. X-ray diffraction profiles indicated that the crystalline phase of as-formed magnetic nanoparticles was magnetite (Fe 3O 4). TEM images revealed rod-like magnetite crystal after the first oxidation cycle, however, the crystal morphologies were transferred into random shape after more oxidation cycles. The applicability of porous magnetic microspheres for removal of cationic dyes from water was also explored. The results exhibited that basic fuchsin and methyl violet could be quickly removed from water with high efficiency. More importantly, the magnetic microspheres could be easily regenerated and repeatedly employed for wastewater treatment. Therefore, a novel methodology was provided for fast removal cationic dyes from wastewater.

Thermal efficiency of heat pipe with alumina nanofluid

The study presents the enhancement of thermal efficiency of heat pipe charged with nanofluid. The Al 2O 3/water nanofluid produced by direct synthesis method is used as the working fluid of experimental heat pipes with three different concentrations (0.5, 1.0 and 3.0 wt.%). The heat pipe is a straight copper tube with inner diameter and length of 8 and 600 mm, respectively. The heat pipes charged with distilled water and nanofluids are tested, respectively. The study discusses about the effects of charge amount of working fluid, tilt angle of heat pipe and weight fraction of nanoparticles on the thermal efficiency of heat pipe. According to the experimental results, the optimum condition of heat pipe is when nanoparticles being at 1.0 wt.%. Under this condition, the thermal efficiency is 16.8%, which is higher than that of heat pipe charged with distilled water. The charge amount can be decreased from 60% to 20%.

Effect of SiO2 nanoparticle addition on the characteristics of a new organic–inorganic hybrid membrane

Poly(vinylidene fluoride) composite membranes filled with different weight fractions of SiO2 nanoparticles have been prepared by a blending method. Cation-exchange groups were introduced by the copolymerization of glycidyl methacrylate with divinylbenzene and subsequent sulfonation. These hybrid membranes have been characterized by Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and water uptake and ion-exchange capacity measurements. Membrane potential and membrane conductivity measurements have been carried out with different counter ions to investigate the relationship between ionic migration and the SiO2 nanoparticle content. The counter-ion transport number and permselectivity of these membranes are found to be highly dependent on the SiO2 content in the membrane phase and the nature of the counter ion. Membrane conductance was analyzed in terms of phenomenological coefficients using non-equilibrium thermodynamic principles. It can be concluded that these hybrid membranes exhibit high thermal stability, improved selectivity, and moderate membrane conductivity, and may be suitable for use in the electro-driven separation processes.

Physical properties and cellular responses to crosslinkable poly(propylene fumarate)/hydroxyapatite nanocomposites

A series of crosslinkable nanocomposites has been developed using hydroxyapatite (HA) nanoparticles and poly(propylene fumarate) (PPF). PPF/HA nanocomposites with four different weight fractions of HA nanoparticles have been characterized in terms of thermal and mechanical properties. To assess surface chemistry of crosslinked PPF/HA nanocomposites, their hydrophilicity and capability of adsorbing proteins have been determined using static contact angle measurement and MicroBCA protein assay kit after incubation with 10% fetal bovine serum (FBS), respectively. In vitro cell studies have been performed using MC3T3-E1 mouse pre-osteoblast cells to investigate the ability of PPF/HA nanocomposites to support cell attachment, spreading, and proliferation after 1, 4, and 7 days. By adding HA nanoparticles to PPF, the mechanical properties of crosslinked PPF/HA nanocomposites have not been increased due to the initially high modulus of crosslinked PPF. However, hydrophilicity and serum protein adsorption on the surface of nanocomposites have been significantly increased, resulting in enhanced cell attachment, spreading, and proliferation after 4 days of cell seeding. These results indicate that crosslinkable PPF/HA nanocomposites are useful for hard tissue replacement because of excellent mechanical strength and osteoconductivity.

Research of Vacuum Pump with Nano-Lubricant

This study used the Al2O3 nano-lubricant produced from the direct synthesis method was used as the experimental samples and the ultrasonic vibration was used for dispersing the nanoparticles into three types of the weight fraction (0.1, 0.2, 0.3%wt). The base solvent was the lubricant of vacuum pump. The objectives of this study were to discuss the dependence of operating temperature of vacuum pump under the various weight fraction of Al2O3 nanoparticles. In this experiment we added Al2O3 nano-lubricant into the direct drive oil sealed rotary vacuum pump, and used the thermocouple measure the temperature on the four test points (cylinder, in-lubricant, case of vacuum pump and discharge pipeline). The results show that the cylinder temperature was reduced by 1.3% and increased by 0.4%, 1.8%, the lubricant temperature was increased by 5.3%, 0.5% and 1.9%, the case surface temperature was reduced by 1.7%, 1.4% and 1.5%, and discharge pipeline temperature was reduced by 0.6%, 2.1% and 3.8% respectively when the sample fractions were 0.1%, 0.2% and 0.3%wt. From the results, it could be realized that the nano-lubricant has more effects on increasing the performance of heat sink than conventional lubricant.

Halos mechanism in stabilizing of colloidal suspensions: Nanoparticle weight fraction and pH effects

Nanoparticle halo is a novel method that stabilizes colloidal suspensions with high efficiency compared to conventional methods. But, up to now few articles have been published on the stabilization mechanism of this method. This article investigates the dispersion behavior of colloidal Al 2O 3 aqueous suspensions in the presence of highly charged CeO 2 nanoparticles and the effect of two key parameters; the ceria nanoparticle concentration and pH on the stability of Al 2O 3–CeO 2 bidispersed suspensions. The stability behavior of these suspensions was investigated by sedimentation technique. It was concluded from this work that by increasing ceria nanoparticle concentration the stability of these bidispersed systems reaches an optimum condition, but further increasing of nanoparticles results in decreasing of the colloidal suspension stability. Also, the results showed that the suspensions have optimum dispersion state and high stability at pH 10. The calculated DLVO interparticle interaction potentials verified the experimental results of the pH effect on the stability behavior. The stabilization of the bidispersed suspensions was also evidenced by scanning electron microscopy (SEM) and SEM energy dispersive X-ray analysis (SEM/EDXA) of the sediment layers after 3 weeks.

Thermo-mechanical properties of LLDPE/SiO 2 nanocomposites

Two series of linear low density polyethylene (LLDPE)/SiO 2 nanocomposites were prepared. They were based on two types of commercial LLDPE, one prepared by metallocene (mLLDPE) and the other by traditional Ziegler–Natta (zLLDPE) catalysts, and silica nanoparticles surface treated with dimethyldichlorosilane. The silica nanonparticles used have an average diameter of 16 nm, and their weight fraction varied from 2 up to 10%. The structure and thermal-mechanical features of the nanocomposites were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic mechanical spectroscopy (DMA) as well as tensile tests. The effect of nanoparticles on crystallinity, and hence to the morphology of the materials was studied. The secondary transitions were also affected by the filler presence, while the tensile properties were reinforced with varying the nanoparticle weight fraction. The addition of the nanofillers brought up an increase in the elastic modulus and the tensile strength of mLLDPE accompanied by an unusual dramatic increase in the elongation at break. The same trend, although to a lesser extent, was observed for the zLLDPE/SiO 2 composites. The increment of the elastic modulus of the composites with increasing filler content was simulated with three micromechanical models developed in previous works. The model which assumes an effective interface between the matrix and the nanoparticles provided the best fitting with the experimental data of mLLDPE/SiO 2.

04/03093 Comparison of two FEA models for calculatingstresses in shell-and-tube heat exchanger: Jin, W. et al. International Journal of Pressure Vessels and Piping, 2004, 81, (6), 563–567

The current investigation aims to study the second law features of an innovative nanofluid having hybrid nanoparticles of graphene nanoplatelets–Pt through a ribbed triple-tube heat exchanger (RTTHX). The hot nanofluid passes inside the ribbed annulus side, the cold water enters inside the inner tube side, and the normal water moves through the outer annulus side. The effects of nanoparticle weight fraction as well as geometrical parameters including the pitch and height of the ribs are evaluated. The total entropy generation rate of heat exchanger reduces by the weight fraction increase, which demonstrates the great advantage of employing the nanofluid. Both increasing the rib height and rib pitch decrement reduce total entropy production of the nanofluid, whereas increase the total entropy production of RTTHX. Moreover, the total exergy destruction of whole heat exchanger decreases by increase of the weight fraction, such that it reduces about 23% with increasing the weight fraction from 0 to 0.1% at rib pitch of 150 mm and rib height of 3 mm. Furthermore, the second law efficiency enhances with the weight fraction increment, while reduces with the rib pitch decrement and increasing rib height. The second law efficiency has great values in all conditions under study.

Size Tunable Synthesis of Highly Crystalline BaTiO 3 Nanoparticles using Salt-Assisted Spray Pyrolysis

Highly crystalline, dense BaTiO3 nanoparticles in a size range from 30 to 360nm with a narrow size distribution (σg = 1.2–1.4) were prepared at various synthesis temperatures using a salt-assisted spray pyrolysis (SASP) method without the need for post-annealing. The effect of synthesis temperature on particle size, crystallinity and surface morphology of the nanoparticles were characterized by X-ray diffraction and scanning/transmission electron microscopy. The nature of the crystalline structure was analyzed by Rietveld refinement and Raman spectroscopy. The particle size decreased with decreasing operation temperature. The crystal phase was transformed from tetragonal to cubic at a particles size of about 50nm at room temperature. SASP can be used to produce high weight fraction of tetragonal BaTiO3 nanoparticles down to 64nm in a single step.

Preparation and characterization of ZnS–polymer nanocomposite films with high refractive index

Novel ZnS–poly(urethane-methacrylate macromer) (PUMM) nanocomposite films with high refractive index were prepared by incorporating thiophenol (PhSH)–4-thiomethyl styrene (TMSt)-capped ZnS nanoparticles into a urethane-methacrylate macromer (UMM), followed by spin-coating and ultraviolet radiation initiated free radical polymerization. PhSH–TMSt-capped colloidal ZnS solution was synthesized by reacting zinc acetate with H2S in N,N-dimethylformamide. UMM macromer was synthesized by reacting 2-hydroxyethyl methacrylate (HEMA) with isocyanate group terminated polythiourethane oligomer which was obtained from polyaddition of 2,2′-dimercaptoethyl sulfide (MES) with 2,4-tolylene diisocyanate (TDI). Thiol-capped ZnS nanoparticles were characterized and found to be 2.0–5.0 nm in diameter with a cubic phase structure. The chemical composition of these ZnS nanoparticles was determined to be Zn2+ ∶ S2− ∶ RS− = 1 ∶ 0.6 ∶ 0.6 using chemical analysis methods. The weight fraction of ZnS nanoparticles in the films was measured by TGA, and it accords well with that of theoretical calculation. FTIR and DSC studies show that ZnS nanoparticles were successfully immobilized into the polymer matrix and the resulting nanocomposite films have a good thermal stability. TEM images indicate that the ZnS nanoparticles were uniformly dispersed in the polymer matrix and the particles remained their original size (2–5 nm) before incorporation into the polymer matrix. The XPS depth profiling technique demonstrates that the ZnS nanoparticles were also dispersed homogeneously in the depth scales of the polymer matrix. The nanocomposite films show high optical transparency in the visible region (T > 95% at 550 nm) and high refractive index in the range of 1.645–1.796 at 632.8 nm as the content of thiol-capped ZnS nanoparticles linearly increased from 0 to 86 wt%.