Laser ablation of magnesium in deionized water (DW), solutions of DW and sodium dodecyl sulfate (SDS) with different concentrations, acetone and 2-propanol has been conducted. The results showed that ...ablation in acetone and 2-propanol yielded MgO and Mg nanocrystallites as isolated particles and agglomerated chains probably intermixed with organic residues resulting from the alteration/decomposition of the solvents under the high-energy conditions. Brucite-like Mg(OH)
2 particles were mainly produced by laser ablation of Mg in either DW or DW–SDS solutions. Ablation in DW yielded particles of fiber-like shapes having a diameter of about 5–10
nm and length as long as 150
nm. Materials produced in DW–SDS solutions were composed of various size and shape particles. Some had rough surfaces with irregular shapes. Small particles were about 20–30
nm and larger particles were about 120
nm. Particles with rod-like, triangular, and plate-like shapes were also observed.
Heterostructures between montmorillonite and embedded α-Fe2O3 nanoparticles are explored to create new hybrid particles with high magnetic response and magnetic-field induced tunability. α-Fe2O3 ...nanoparticles are hybridized to montmorillonite clays by using an intercalation technique. Also, stable aqueous fluids consisting of the heterostructured particles are prepared and the rheology of the fluids under external magnetic field is examined. When α-Fe2O3 nanoparticles are embedded in the interlayer space of montmorillonite clays, the magnetization per Fe atom increases at most 60 times. This unique combination of the magnetization and the coercivity is traced to the suppressed growth of embedded α-Fe2O3 nanoparticles by the aluminosilicate layers, leading to the size control, anisotropic magnetic interaction, and uniaxial stress of two-dimensionally distributed α-Fe2O3 nanoparticles. Furthermore, high magnetization of heterostructured particles leads to strong dependence of fluids’ viscosity on the external magnetic field. The present study indicates that the new heterostructured particles have unique magnetic field-dependent properties that are not attainable in individual clay or iron oxide particles.
Measurements of nanofluid surface tension were made using the pendant droplet method. Three different types of nanoparticles were used – laponite, silver and Fe
2O
3 – with de-ionized water (DW) as ...the base fluid. The reported results focus on the following categories: (1) because some nanoparticles require surfactants to form stable colloids, the individual effects of the surfactant and the particles were investigated; (2) due to evaporation of the pendant droplet, the particle concentration increases, affecting the apparent surface tension; (3) because of the evaporation process, a hysteresis was found where the evaporating droplet can only achieve lower values of surface tension than that of nanofluids at the same prepared concentrations; and (4) the Stefan equation relating the apparent surface tension and heat of evaporation was found to be inapplicable for nanofluids investigated. Comparisons with findings for sessile droplets are also discussed, pointing to additional effects of nanoparticles other than the non-equilibrium evaporation process.
Fine particulate matter (PM
2.5
) concentrations associated with 202 24-hr samples collected at the National Energy Technology Laboratory (NETL) particulate matter (PM) characterization site in south ...Pittsburgh from October 1999 through September 2001 were used to apportion PM
2.5
into primary and secondary contributions using Positive Matrix Factorization (PMF2). Input included the concentrations of PM
2.5
mass determined with a Federal Reference Method (FRM) sampler, semi-volatile PM
2.5
organic material, elemental carbon (EC), and trace element components of PM
2.5
. A total of 11 factors were identified. The results of potential source contributions function (PSCF) analysis using PMF2 factors and HYSPLIT-calculated back-trajectories were used to identify those factors associated with specific meteorological transport conditions. The 11 factors were identified as being associated with emissions from various specific regions and facilities including crustal material, gasoline combustion, diesel combustion, and three nearby sources high in trace metals. Three sources associated with transport from coal-fired power plants to the southeast, a combination of point sources to the northwest, and a steel mill and associated sources to the west were identified. In addition, two secondary-material-dominated sources were identified, one was associated with secondary products of local emissions and one was dominated by secondary ammonium sulfate transported to the NETL site from the west and southwest. Of these 11 factors, the four largest contributors to PM
2.5
were the secondary transported material (dominated by ammonium sulfate) (47%), local secondary material (19%), diesel combustion emissions (10%), and gasoline combustion emissions (8%). The other seven factors accounted for the remaining 16% of the PM
2.5
mass.
Laponite, Fe
2O
3 and Ag nanoparticles were added to deionized water to study their effect of evaporation rates. The results show that these nanofluid droplets evaporate at different rates (as ...indicated by the evaporation rate constant
K in the well known
D
2-law) from the base fluid. Different particles lead to different values of
K. As the particle concentration increases due to evaporation,
K values of various Ag and Fe
2O
3 nanofluids go through a transition from one value to another, further demonstrating the effect of increasing nanoparticle concentration. The implication for the heat of vaporization (
h
fg
) is discussed.
Apportionment of primary and secondary pollutants during a July 2001 intensive study at the National Energy Technology Laboratory is reported. PM
2.5
was apportioned into primary and secondary ...contributions using PMF2, and results were compared with apportionment based on UNMIX 2.3. Input to PMF2 included PM
2.5
mass data from four per 24 hour PC-BOSS filters and TEOM, NO
x
, NO
2
, O
3
, non-volatile, semi-volatile, and volatile organic material, elemental carbon, sulfate, and PIXE determined trace metals. Nine factors were identified in the PMF analysis. Six factors were associated with primary particles from crustal, mobile (gasoline and diesel), and three local sources high in trace metals. Three factors were associated with secondary sources. Two were associated with local emissions dominated by organic material, one was dominated by transported ammonium sulfate. UNMIX was able to identify the two major mobile sources, major local secondary source and transported secondary source. The three major sources of PM
2.5
were identified as secondary transported material (dominated by ammonium sulfate) from west and southwest (46%), secondary material formed during mid-day photochemical processes (21%), and primary emissions from diesel (10%) and gasoline (8%) mobile sources. The other five sources accounted for the remaining 15% of the PM
2.5
. These findings are consistent with the majority of secondary ammonium sulfate in the Pittsburgh area resulting from distant transport, and so decoupled from local activity involving organic pollutants in the metropolitan area. In contrast, the major local secondary sources were dominated by organic material.
Invert emulsions are used to drill for oil and gas when good wellbore stability and high temperature tolerance are required. These drilling fluids contain a solid phase and two immiscible liquid ...phases stabilised with a polymeric surfactant. In ultra deep drilling, due to high temperature, the surfactant degrades causing phase separation. However, fine particles can be used as stabilisers, and the result is a Pickering emulsion. Here, we demonstrate that the use of a combination of hydrophobic nanoparticles and organically modified nanoclay results in stable water‐in‐oil invert emulsions model drilling fluids. These gel‐like model fluids have the desired plastic viscosity and yield stress suitable for drilling fluid applications that can be modified by adjusting the nanoparticle‐content. Aging experiments at 225°C showed that they also have high‐temperature stability for demanding drilling operations.
Gaseous and particulate pollutant concentrations associated with five samples per day collected during a July 2001 summer intensive study at the Pittsburgh Carnegie Mellon University (CMU) Supersite ...were used to apportion fine particulate matter (PM2.5) into primary and secondary contributions using PMF2. Input to the PMF2 analysis included the concentrations of PM2.5 nonvolatile and semivolatile organic material, elemental carbon (EC), ammonium sulfate, trace element components, gas-phase organic material, and NO(x), NO2, and O3 concentrations. A total of 10 factors were identified. These factors are associated with emissions from various sources and facilities including crustal material, gasoline combustion, diesel combustion, and three nearby sources high in trace metals. In addition, four secondary sources were identified, three of which were associated with secondary products of local emissions and were dominated by organic material and one of which was dominated by secondary ammonium sulfate transported to the CMU site from the west and southwest. The three largest contributors to PM2.5 were secondary transported material (dominated by ammonium sulfate) from the west and southwest (49%), secondary material formed during midday photochemical processes (24%), and gasoline combustion emissions (11%). The other seven sources accounted for the remaining 16% of the PM2.5. Results obtained at the CMU site were comparable to results previously reported at the National Energy Technology Laboratory (NETL), located approximately 18 km south of downtown Pittsburgh. The major contributor at both sites was material transported from the west and southwest. Some difference in nearby sources could be attributed to meteorology as evaluated by HYSPLIT model back-trajectory calculations. These findings are consistent with the majority of the secondary ammonium sulfate in the Pittsburgh area being the result of contributions from distant transport, and thus decoupled from local activity involving organic pollutants in the metropolitan area. In contrast, the major local secondary sources were dominated by organic material.
PM2.5 mass was measured daily with three batch samplers, a PM2.5 R&P Partisol-Plus FRM, an Andersen RAAS, and a BYU PC-BOSS, and continuously with a TEOM monitor during July and August 2000. PM2.5 ...composition was also determined. These data are part of an ongoing PM2.5 characterization program centered around a sampling site at the National Energy Technology Laboratory Pittsburgh campus. The composition and concentrations of PM2.5 were both highly variable during this time period. Likely sources of PM2.5 during low concentration periods were transportation, coal-fired boiler, and other emissions generated in the local area. For these periods, the average concentration of PM2.5 was 13 μg/m3 and 70% of the PM2.5 mass was carbonaceous material, including semivolatile organic material that was lost in varying degrees from both the TEOM and FRM samplers. In contrast, much higher concentrations of PM2.5 were associated with transport of pollutants to the site. Analysis of meteorological and back-trajectory data suggests that these pollutants were emitted elsewhere during a period of high atmospheric pressure and were subsequently transported to the site with the passage of a frontal system. When the PM2.5 collected at the site originated from the west or southwest, the concentrations averaged 31 μg/m3 and ammonium sulfate averaged 54% of the PM2.5 mass. Scanning election microscopy and trace element analyses are consistent with the association of high concentration PM2.5 episodes with transport of coke and iron processing, coal-fired boiler, and other emissions from the Ohio River Valley region to the NETL site. Preliminary observations on the use of SEM and PIXE data in source apportionment at the NETL site are given.
From October 1999 through September 2000, particulate matter (PM) with aerodynamic diameter ≥2.5 μm (PM
2.5
) mass and composition were measured at the National Energy Technology Laboratory ...Pittsburgh site, with a particle concentrator Brigham Young University-organic sampling system and a tapered element oscillating microbalance (TEOM) monitor. PM
2.5
measurements had also been obtained with TEOM monitors located in the Pittsburgh, PA, area, and at sites in Ohio, including Steub-enville, Columbus, and Athens. The PM data from all these sites were analyzed on high PM days; PM
2.5
TEOM particulate mass at all sites was generally associated with transitions from locally high barometric pressure to lower pressure. Elevated concentrations occurred with transport of PM from outside the local region in advance of frontal passages as the local pressure decreased. During high-pressure periods, concentrations at the study sites were generally low throughout the study region. Further details related to this transport were obtained from surface weather maps and estimated back-trajectories using the hybrid single-particle Lagrangian integrated trajectory model associated with these time periods. These analyses indicated that transport of pollutants to the Pittsburgh site was generally from the west to the southwest. These results suggest that the Ohio River Valley and possible regions beyond act as a significant source of PM and its precursors in the Pittsburgh area and at the other regional sites included in this study.
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