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S. Masoud Hosseini A. R. Moghadassi D. Henneke Ali Elkamel 《Journal of Thermal Analysis and Calorimetry》2010,101(1):113-118
Changes in the thermal conductivities of paraffin and mono ethylene glycol (MEG) as a function of β-SiC nanoparticle concentration
and size was studied. An enhancement in the effective thermal conductivity was found for both fluids (i.e., both paraffin
and MEG) upon the addition of nanoparticles. Although an enhancement in thermal conductivity was found, the degree of enhancement
depended on the nanoparticle concentration in a complex way. An increase in particle-to-particle interactions is thought to
be the cause of the enhancement. However, the enhancement became muted at higher particle concentrations compared to lower
ones. This phenomenon can be related to nanoparticles interactions. An improvement in the thermal conductivities for both
fluids was also found as the nanoparticle size shrank. It is believed that the larger Brownian motion for smaller particles
causes more particle-to-particle interactions, which, in turn, improves the thermal conductivity. The role that the base-fluid
plays in the enhancement is complex. Lower fluid viscosities are believed to contribute to greater enhancement, but a second
effect, the interaction of the fluid with the nanoparticle surface, can be even more important. Nanoparticle-liquid suspensions
generate a shell of organized liquid molecules on the particle surface. These organized molecules more efficiently transmit
energy, via phonons, to the bulk of the fluid. The efficient energy transmission results in enhanced thermal conductivity.
The experimentally measured thermal conductivities of the suspensions were compared to a variety of models. None of the models
proved to adequately predict the thermal conductivities of the nanoparticle suspensions. 相似文献
3.
S. Masoud Hosseini A. R. Moghadassi Dale E. Henneke 《Journal of Thermal Analysis and Calorimetry》2010,99(3):873-877
Immobilization of lead contamination in soils by precipitation of non-assimilable for plants Pb-phosphate was considered. Glassy fertilizer of controlled release rate of the nutrients for plants as a source of phosphate anions was applied. Thermal analysis methods (TG/DTG/DTA) were used for the identification of components of Pb-precipitate, which being in statu nascendi have nonstoichiometric composition and disordered crystallographic structure difficult to identify by XRD method. Application of TA methods permits to demonstrate the negative role of Pb complexing citric acid solution simulating the natural soil conditions, which inhibits the Pb-phosphate of pyromorphite type formation. 相似文献
4.
Sultana Ferdous Marios A. Ioannidis Dale Henneke 《Journal of nanoparticle research》2011,13(12):6579-6589
The pendant drop technique was used to characterize the adsorption behavior of n-dodecane-1-thiol and n-hexane-1-thiol-capped gold nanoparticles at the hexane–water interface. The adsorption process was studied by analyzing the
dynamic interfacial tension versus nanoparticle concentration, both at early times and at later stages (i.e., immediately
after the interface between the fluids is made and once equilibrium has been established). A series of gold colloids were
made using nanoparticles ranging in size from 1.60 to 2.85 nm dissolved in hexane for the interfacial tension analysis. Following
free diffusion of nanoparticles from the bulk hexane phase, adsorption leads to ordering and rearrangement of the nanoparticles
at the interface and formation of a dense monolayer. With increasing interfacial coverage, the diffusion-controlled adsorption
for the nanoparticles at the interface was found to change to an interaction-controlled assembly and the presence of an adsorption
barrier was experimentally verified. At the same bulk concentration, different sizes of n-dodecane-1-thiol nanoparticles showed different absorption behavior at the interface, in agreement with the findings of Kutuzov
et al. (Phys Chem Chem Phys 9:6351–6358, 2007). The experiments additionally demonstrated the important role played by the capping agent. At the same concentration, gold
nanoparticles stabilized by n-hexane-1-thiol exhibited greater surface activity than gold nanoparticles of the same size stabilized by n-dodecane-1-thiol. These findings contribute to the design of useful supra-colloidal structures by the self-assembly of alkane-thiol-capped
gold nanoparticles at liquid–liquid interfaces. 相似文献
5.
Nichols William T. Malyavanatham Gokul Henneke Dale E. O'Brien Daniel T. Becker Michael F. Keto John W. 《Journal of nanoparticle research》2002,4(5):423-432
Silver nanoparticles were produced by laser ablation of a continuously flowing aerosol of microparticles in nitrogen at varying laser fluences. Transmission electron micrographs were analyzed to determine the effect of laser fluence on the nanoparticle size distribution. These distributions exhibited bimodality with a large number of particles in a mode at small sizes (3–6-nm) and a second, less populated mode at larger sizes (11–16-nm). Both modes shifted to larger sizes with increasing laser fluence, with the small size mode shifting by 35% and the larger size mode by 25% over a fluence range of 0.3–4.2-J/cm2. Size histograms for each mode were found to be well represented by log-normal distributions. The distribution of mass displayed a striking shift from the large to the small size mode with increasing laser fluence. These results are discussed in terms of a model of nanoparticle formation from two distinct laser–solid interactions. Initially, laser vaporization of material from the surface leads to condensation of nanoparticles in the ambient gas. Material evaporation occurs until the plasma breakdown threshold of the microparticles is reached, generating a shock wave that propagates through the remaining material. Rapid condensation of the vapor in the low-pressure region occurs behind the traveling shock wave. Measurement of particle size distributions versus gas pressure in the ablation region, as well as, versus microparticle feedstock size confirmed the assignment of the larger size mode to surface-vaporization and the smaller size mode to shock-formed nanoparticles. 相似文献
6.
A. R. Moghadassi S. Masoud Hosseini D. Henneke A. Elkamel 《Journal of Thermal Analysis and Calorimetry》2009,96(1):81-84
Thermal conductivity is an important parameter in the field of nanofluid heat transfer. This article presents a novel model
for the prediction of the effective thermal conductivity of nanofluids based on dimensionless groups. The model expresses
the thermal conductivity of a nanofluid as a function of the thermal conductivity of the solid and liquid, their volume fractions,
particle size and interfacial shell properties. According to this model, thermal conductivity changes nonlinearly with nanoparticle
loading. The results are in good agreement with the experimental data of alumina-water and alumina-ethylene glycol based nanofluids. 相似文献
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E. G. Henneke II C. T. Herakovich G. L. Jones M. P. Renieri 《Experimental Mechanics》1975,15(1):10-16
Acoustic-emission (AE) count rates are presented for tensile loading of unidirectional boron-epoxy and for aluminum sheets reinforced with unidirectional boron-epoxy. It is shown that different prepreg materials have different characteristic AE patterns. Results from composite-reinforced metal specimens show that early failures are accompanied by a sharp increase in AE count rate at the knee of the bilinear stress-strain diagram. It is further shown that the count rates are a function of specimen fabrication and that higher total counts do not necessarily correspond to early failures. 相似文献
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Results are reported on the use of an infrared thermovision imaging system to observe the surface temperature distribution caused by the application of high-power 20 kHz ultrasound to a variety of metal specimens and one fluoroplastic. Temperature increases of the order of 200°C were found to occur 20 to 30 s after initiation of insonation in resonant specimens of fine-grained polycrystalline brass, copper, and steel. Observation of extremely rapid temperature increases localized to the points of attachment of thermocouples to the test specimens casts strong doubt on all previous thermocouple temperature measurements made during similar experiments by earlier investigators. Fatigue cracks, artificially induced defects, and grain boundaries were also found to be sites of rapid localized heating during insonation. 相似文献
9.
Nichols William T. Malyavanatham Gokul Henneke Dale E. Brock James R. Becker Michael F. Keto John W. Glicksman Howard D. 《Journal of nanoparticle research》2000,2(2):141-145
Silver nanoparticles were produced by laser ablation of a continuously flowing aerosol of microparticles entrained in argon, nitrogen and helium at a variety of gas pressures. Nanoparticles produced in this new, high-volume nanoparticle production technique are compared with our earlier experiments using laser ablation of static microparticles. Transmission electron micrographs of the samples show the nanoparticles to be spherical and highly non-agglomerated under all conditions tested. These micrographs were analyzed to determine the effect of carrier gas type and pressure on size distributions. We conclude that mean diameters can be controlled from 4 to 20 nm by the choice of gas type and pressure. The smallest nanoparticles were produced in helium, with mean sizes increasing with increasing molecular weight of the carrier gas. These results are discussed in terms of a model based on cooling via collisional interaction of the nanoparticles, produced in the laser exploded microparticle, with the ambient gas. 相似文献
10.
Sultana Ferdous Marios A. Ioannidis Dale E. Henneke 《Journal of nanoparticle research》2012,14(5):850
The effects of temperature, pH and sodium chloride (NaCl) concentration on the equilibrium and dynamic interfacial tension (IFT) of 4.4-nm gold nanoparticles capped with n-dodecanethiol at hydrocarbon–water interfaces was studied. The pendant drop technique was used to study the adsorption properties of these nanoparticles at the hexane–water and nonane–water interfaces. The physical size of the gold nanoparticles was determined by TEM image analysis. The interfacial properties of mixtures of these nanoparticles, having different sizes and capping agents, were then studied. The addition of NaCl was found to cause a decrease of the equilibrium and dynamic IFT greater than that which accompanies the adsorption of nanoparticles at the interface in the absence of NaCl. Although IFT values for acidic and neutral conditions were found to be similar, a noticeable decrease in the IFT was found for more basic conditions. Increasing the temperature of the system was found to cause an increase in both dynamic and equilibrium IFT values. These findings have implications for the self-assembly of functionalized gold nanoparticles at liquid–liquid interfaces. 相似文献