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At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Quantitative assessment of environmental phenomena on maximum pit size predictions in marine environments

Maximum pit sizes were predicted for dilute and concentrated NaCl and MgCl 2 solutions as well as sea-salt brine solutions corresponding to 40% relative humidity (RH) (MgCl 2 -rich) and 76% RH (NaCl-rich) at 25 °C. A quantitative method was developed to capture the effects of various cathode evolution phenomena including precipitation and dehydration reactions. Additionally, the sensitivity of the model to input parameters was explored. Despite one's intuition, the highest chloride concentration (roughly 10.3 M Cl – ) did not produce the largest predicted pit size as the ohmic drop was more severe in concentrated MgCl 2 solutions. Therefore, the largest predicted pits were calculated for saturated NaCl (roughly 5 M Cl – ). Next, it was determined that pit size predictions are most sensitive to model input parameters for concentrated brines. However, when the effects of cathodic reactions on brine chemistry are considered, the sensitivity to input parameters is decreased. Although there was not one main input parameter that influenced pit size predictions, two main categories were identified. Under similar chloride concentrations (similar RH), the water layer thickness (WL), and pit stability product, (i · x) sf , are the most influential factors. When varying chloride concentrations (RH), changes in WL, the brine specific cathodic kinetics on the external surface (captured in the equivalent current density (i eq )), and conductivity (k o ) are the most influential parameters. Finally, it was noted that dehydration reactions coupled with precipitation in the cathode will have the largest effect on predicted pit size, and cause the most significant inhibition of corrosion damage.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Effect of crystallite size on lithium storage performance of high entropy oxide (Cr 0.2 Mn 0.2 Co 0.2 Ni 0.2 Zn 0.2 ) 3 O 4 nanoparticles

High-entropy oxides (HEOs), known for their high theoretical capacity and structural stability, are considered promising anode materials for next-generation lithium-ion batteries (LIBs). In this research, we synthesized a novel spinel-type HEO, (Cr 0.2 Mn 0.2 Co 0.2 Ni 0.2 Zn 0.2 ) 3 O 4 , using a solution combustion method. By adjusting the quantity of the combustion agent, we produced samples with varying crystallite sizes. The crystallite size of the HEOs initially enlarges with an increased combustion agent, then diminishes. The enhancement of crystallite size correlates with improved electrochemical performance for lithium storage. Notably, the (Cr 0.2 Mn 0.2 Co 0.2 Ni 0.2 Zn 0.2 ) 3 O 4 nanoparticles, with the largest crystallite size of 36.3 nm, demonstrated a reversible capacity of 343 mA h g -1 after 100 cycles at 100 mA g -1 , a capacity retention to 319 mA h g -1 after 1000 cycles at 1 A g -1 , and a commendable rate capability of 260 mA h g -1 at 2 A g -1 . Furthermore, this study underscores the pivotal role of crystallite size in LIB performance and presents a viable strategy to enhance the lithium storage capabilities of HEOs and other metal oxides.

25 ENERGY STORAGE↗
DOE OSTI2024

Process parameter translation strategies for variable directed energy deposition spot size using 316L, copper, and Inconel 625

Directed energy deposition (DED) is a form of additive manufacturing available across a variety of laser spot diameter values, often referred to as spot sizes. However, there is no method to easily transfer process parameters across discrete spot sizes, leading to DED process parameters that are equipment specific and not widely applicable. In this study, a strategy is proposed and investigated for five spot sizes that keep the areal energy density constant while varying power, feed rate, and powder flow during the deposition of 316L stainless steel. An assessment of trends in hardness and microstructure is possible due to the novel production of components of a single material across several spot sizes using a single nozzle on a single DED system. The proposed strategy was used to nullify the hardness drop during functional grading of Inconel 625 and pure copper, enabling fabrication of multi-material sample that does not compromise desirable properties. This application shows the value in establishing more efficient process parameter development and understanding spot size influences on geometric and material property flexibility, to enable a more diverse powder-based DED design space and to increase the industry adoption of DED systems.

316L↗
DOE OSTI2025

Grain size effects on slip band development

Crystallographic slip localizations, known as slip bands, concentrate stress in polycrystals, often leading to the nucleation of damage. Slip band development has been experimentally shown to be sensitive to grain size, tending to develop more frequently and with a greater intensity in large grains. In this work, we investigate the influence of grain size on the propensity for crystallographic slip band development. To this end, we employ the slip band-fast Fourier transform method (SB-FFT). SB-FFT is a 3D, full-field crystal plasticity model that permits the incremental development of discrete crystallographic slip bands according to microstructure and material properties. We present a model Inconel 718 tricrystal to isolate the effect of grain size. Our findings show that slip bands in large grains develop at lower applied strain levels and at a faster rate than slip bands in small grains. The grain size effect is due to a backstress produced by the interaction of the slip band and its neighboring grain. The backstress is most intense at small grain sizes, impeding slip activity within a developing slip band and immediately surrounding the slip band.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Apolipoprotein A-I modulates HDL particle size in the absence of apolipoprotein A-II

Human high-density lipoproteins (HDLs) are a complex mixture of structurally related nanoparticles that perform distinct physiological functions. We previously showed that human HDL containing apolipoprotein A-I (APOA1) but not apolipoprotein A-II (APOA2), designated LpA-I, is composed primarily of two discretely sized populations. Here, we isolated these particles directly from human plasma by antibody affinity chromatography, separated them by high-resolution size-exclusion chromatography and performed a deep molecular characterization of each species. The large and small LpA-I populations were spherical with mean diameters of 109 Å and 91 Å, respectively. Unexpectedly, isotope dilution MS/MS with [ 15 N]-APOA1 in concert with quantitation of particle concentration by calibrated ion mobility analysis demonstrated that the large particles contained fewer APOA1 molecules than the small particles; the stoichiometries were 3.0 and 3.7 molecules of APOA1 per particle, respectively. MS/MS experiments showed that the protein cargo of large LpA-I particles was more diverse. Human HDL and isolated particles containing both APOA1 and APOA2 exhibit a much wider range and variation of particle sizes than LpA-I, indicating that APOA2 is likely the major contributor to HDL size heterogeneity. We propose a ratchet model based on the trefoil structure of APOA1 whereby the helical cage maintaining particle structure has two “settings”—large and small—that accounts for these findings. This understanding of the determinants of HDL particle size and protein cargo distribution serves as a basis for determining the roles of HDL subpopulations in metabolism and disease states.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2016

Effective reduction in the nanoparticle sizes of NiO obtained via the pyrolysis of nickel malonate precursor modified using oleylamine surfactant

Nickel oxide nanoparticles were synthesized via thermal decomposition of two precursors, the first, a simple nickel malonate and the second, a nickel malonate modified by oleylamine, a surfactant, both having been synthesized by precipitation. While FTIR, TGA and ToF-SIMS were used to characterize the two precursors and to show the presence of oleylamine in the modified precursor, XRD, SEM, TEM and BET were employed to investigate the structure, the morphology and the specific surface area of the decomposition products obtained after pyrolysis. The results showed that the modification of nickel malonate by oleylamine was effective. The XRD results, which showed a cubic structure for the NiO obtained, suggest with SEM an important particle size reduction (at least 54%) when oleylamine was used to modify the nickel malonate precursor. The SEM images also showed a well-defined spherical nanoparticle morphology in both cases, not affected by the presence of oleylamine. The TEM also confirmed the reduction of particle size and their spherical nature but at the same time showed that, in the presence of oleylamine, there was no agglomeration resulting in a more uniform particle size distribution. The specific surface area of the NiO obtained by the oleylamine-modified precursor was 4.7 times larger than that obtained with the regular precursor. This again confirms the particle size reduction. - Highlights: • Nickel malonate precursor has been synthesized by precipitation method. • This precursor was successfully modified by a surfactant (oleylamine). • NiO was identified as the decomposition products of the previous precursors. • Oleylamine has provoked around 54% of particle size reduction of the NiO.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Size and morphology controlled NiSe nanoparticles as efficient catalyst for the reduction reactions

Facile and efficient ball milling and polyol methods were employed for the synthesis of nickel selenide (NiSe) nanoparticle. The particle size of the NiSe nanoparticle has been controlled mechanically by varying the ball size in the milling process. The role of the surfactants in the formation of various morphologies was studied. The compounds were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray energy dispersive spectroscopy (EDS). The efficiency of the NiSe nanoparticle as a catalyst was tested for the reduction of para-nitroaniline (PNA) to para-phenyldiamine (PPD) and para-nitrophenol (PNP) to para-aminophenol (PAP) using NaBH{sub 4} as the reducing agent. Particle size, morphology and the presence of surfactant played a crucial role in the reduction process. - Graphical abstract: NiSe nanoparticles in different size and morphology were synthesized using facile ball milling and polyol methods. Particle size, morphology and the presence of surfactant in these materials played a crucial role in the hydrogenation of PNA and PNP. - Highlights: • NiSe nanoparticles synthesized using ball milling and solution phase methods. • NiSe nanoparticle is an efficient catalyst for the reduction of PNA and PNP. • NiSe is found to be better than the best reported noble metal catalysts.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Grain size determination in nano-scale polycrystalline aggregates by precession illumination-hollow cone dark field imaging in the transmission electron microscope

Precession illumination hollow cone dark field (PI-HCDF) transmission electron microscopy (TEM) provides high contrast multi-beam dark field images, which are suitable for effective and robust grain size measurements in nano-scale polycrystalline aggregates. Precession illumination with slightly converged electron beam probes and precession angles up to 3 Degree-Sign has been produced using a computer-controlled system using a JEOL JEM 2000FX TEM instrument. Theoretical and practical aspects of the experimental technique are discussed using example precession illumination hollow cone diffraction patterns from single crystalline NiAl and the importance of selecting the appropriate precession angle for PI-HCDF image formation and interpretation is described. Results obtained for precession illumination are compared with those of conventional parallel beam illumination experiments. Nanocrystalline Al has been used to evaluate the influence of the precession angle on PI-HCDF image contrast with a focus on grain size analysis. PI-HCDF imaging has been applied for grain size measurements in regions of a nanocrystalline Al thin film adjacent to the edge of a pulsed laser melted and rapidly solidified region and determined the dimensions of a heat-affected zone. - Highlights: Black-Right-Pointing-Pointer New TEM method for grain size measurements combines TEM resolution with obtainability of statistically significant data sets. Black-Right-Pointing-Pointer We use precession illumination to produce time precession illumination hollow cone diffraction patterns PI-HCDP. Black-Right-Pointing-Pointer Contrast in dark field images (PI-HCDF) formed from PI-HCDP is easy to interpret as dynamical effects are reduced. Black-Right-Pointing-Pointer PI-HCDFs use several time-averaged g-rings simultaneously and contain more information than conventional DF-images. Black-Right-Pointing-Pointer Easy contrast interpretation and less dark field images required, allows fast, robust and reliable grain size determination.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Synthesis and photocatalytic applications of nano-sized zinc-doped mesoporous titanium oxide

Graphical abstract: Nano-sized mesoporous titanium oxide (T0) and zinc-doped nano-sized mesoporous titanium oxides (TA–TD) were synthesized by a simple method and characterized by different techniques. All materials have been studied in the photocatalytic degradation of methylene blue under UV light, observing that the decrease in the band gap of the materials seems to have a positive influence in the photocatalytic activity. Display Omitted Highlights: ► Nano-sized mesoporous TiO{sub 2} and Zn-doped TiO{sub 2} have been synthesized and characterized. ► Band gap of the Zn-doped TiO{sub 2} decreases when the Zn amount increases. ► Materials consist of porous particles (10–20 nm). ► The photocatalytic degradation of MB has been studied for these materials. ► A decrease in the band gap of the materials enhances the photocatalytic activity. -- Abstract: The synthesis of nano-sized mesoporous titanium oxide (T0) is described by an easy synthetic method which consists of the reaction of titanium tetraisopropoxide and a solution of HNO{sub 3} in water (pH 2.0) and the subsequent elimination of the volatiles by simple distillation. On the other hand, zinc-doped mesoporous titanium oxides (TA–TD) were synthesized using the same method but adding increasing amounts of Zn(NO{sub 3}){sub 2} to give materials which contain between 0.12 and 6.17 wt.% Zn. Upon the calcinations of all the obtained materials, characterization has been carried out by using N{sub 2} adsorption–desorption isotherms, powder X-ray diffraction, X-ray fluorescence, UV–vis spectrometry, solid state {sup 47,49}Ti NMR spectroscopy and transmission electronic microscopy (TEM). The results show that all these materials are mesoporous, with BET surfaces between 54 and 121 m{sup 2}/g and similar pore diameters between 6.4 and 9.1 nm. XRD studies show that these materials mainly consist of anatase and very small amounts of brookite. TEM technique shows the small particle sizes of the corresponding materials (from 10 to 20 nm) and the porous structure of parallel and straight channels for T0, TA, TB and TC while the order in the porosity of the system is lost in TD. In addition, studies of the Kubelka-Munk function show that the band gap energy of the synthesized materials decreases with the increase of the Zn amount of the material from 3.24 (for T0) to 2.91 eV (for TD). All the studied materials have been studied in the photocatalytic degradation of methylene blue (MB) under UV light, observing that the decrease in the band gap of the materials seems to have a positive influence in the photocatalytic activity.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Characterization and visible light photocatalytic mechanism of size-controlled BiFeO{sub 3} nanoparticles

Graphical abstract: BiFeO{sub 3} nanoparticles showed the size-dependent photocatalytic properties, and the corresponding photocatalytic mechanism for the pollutant degradation was proposed. - Highlights: • Size-controlled BiFeO{sub 3} nanoparticles were prepared by sol–gel method. • The hydroxyl radicals were the main reactive species responsible for the pollutant degradation. • BiFeO{sub 3} nanoparticles showed the size-dependent photocatalytic properties. - Abstract: BiFeO{sub 3} nanoparticles with controlled particle size were synthesized via sol–gel method. The samples were characterized by X-ray powder diffraction, transmission electron microscope, Raman spectra, nitrogen adsorption technique and UV–vis diffuse reflectance spectra. Photocatalytic activity of BiFeO{sub 3} nanoparticles was further examined by monitoring the degradation of Rhodamine B dye in an aqueous solution under visible light irradiation. Through the calculation of band position and a number of diagnostic experiments, the photocatalytic mechanism of BiFeO{sub 3} nanoparticles was proposed in this study. It was found that the hydroxyl radicals originated from the photogenerated electrons were the main reactive species responsible for the pollutant degradation. Moreover, with the variations of annealing temperature and time, the average crystallite size, specific surface area and crystallinity of BiFeO{sub 3} nanoparticles could be changed, which thus affected the photocatalytic activity of the corresponding samples.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Photocatalytic performances of BiFeO{sub 3} particles with the average size in nanometer, submicrometer, and micrometer

Highlights: • Three different synthesis routes have been taken to successfully prepare the BiFeO{sub 3} particles with the different morphologies and average size in 50, 500 nm, and 15 μm. • For photodegradation of dyes under visible irradiation in the presence of BiFeO{sub 3}, the photocatalytic efficiency increases quickly with the decrease in size. • The enhanced photocatalytic efficiency of BiFeO{sub 3} nanoparticles may attribute to more surface active catalytic-sites and shorter distances carriers have to migrate to the surface reaction sites. - Abstract: Three different synthesis routes were taken to successfully prepare the BiFeO{sub 3} particles with the different morphologies and average size in 50, 500 nm, and 15 μm, respectively. The crystal structure was recognized to be a distorted rhombohedral one with the space group R3c. With the decrease in particle size, obvious decrease in peak intensity and redshift in peak position were observed for the Raman active bands. The narrow band gap was determined from the UV–vis absorption spectra, indicating the semiconducting nature of the BiFeO{sub 3}. For photodegradation of dyes under visible irradiation in the presence of BiFeO{sub 3}, the photocatalytic efficiency increased quickly with the decrease in size which may attribute to more surface active catalytic-sites and shorter distances carriers had to migrate to the surface reaction sites.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Influence of plastic properties on the grain size effect on twinning in Ti and Mg

Deformation twinning is an inevitable mode of plastic deformation in hexagonal close packed (HCP) crystals and has been considered a hinderance to achieving formability and ductility. It has long been recognized that reductions in grain size can lower the propensity for twinning. In prior work, EBSD statistical analyses on big data sets of twins in pure Ti and Mg were carried out for the same twin type, loading conditions, initial texture, and range of grain sizes. Here, we revisit these data sets to investigate the role of material plastic properties on grain size effects on deformation twinning. We show that while reductions in grain size dramatically lower the number of twins per grain and the twin thickness in both metals, these effects are several times stronger in Ti than that for Mg. To rationalize this difference, full-field, 3D crystal plasticity calculations are performed. The analysis indicates that the stronger grain size effect in Ti arises due to the larger critical resolved shear stress (CRSS) of its easiest slip system, making Ti less accommodating of the twin shear than Mg. Overall, this result points to plastic properties as additional variables that can be tuned towards developing HCP materials for structural applications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Size effect in stainless steel thin wires under tension

Miniaturization of modern devices drives the exploration into how materials behave in small dimensions. However, the mechanical behaviors of micro-scale specimens under varied loading conditions are still challenging to characterize and predict. In this work, specimen size-dependent weakening effect was experimentally revealed in 316L stainless steel thin wires under tension with wire diameter decreasing from 200 μm down to 61 μm. The underlying mechanisms were primarily associated with surface grain softening and strain localization, which were largely dependent on the number of grains across wire diameter. Through an analog composite model with surface and interior grains that follows the Hall-Petch relation, the extent of surface grain softening was found to coincide with the flow stress reduction due to lack of boundary strengthening. Further using elasto-plastic self-consistent polycrystal modeling, the stress-strain behaviors of interior and surface grains were well described in analogy to those of bulk materials with similar-size grains and extremely large grains, respectively. Subsequently, the analog composite model well simulated the specimen size-dependent weakening effect under tension. This article provided more insights into the size effect exploration and proposed a practical model for describing size-dependent mechanical behaviors of small-scale materials to be applied to miniaturized devices.

316L stainless steel↗
DOE OSTI2015

Optimisation of sewage sludge anaerobic digestion through co-digestion with OFMSW: Effect of collection system and particle size

Highlights: • Methane production rate increased between 56% and 208% during OFMSW–SS codigestion. • The OFMSW particle size reduction from 20 to 8 mm did not affect the methane yield. • OFMSW–SS codigestion promoted β-oxidation and acetoclastic methanogenic activity. • The evolution of specific activity was a feasible tool to control the process. - Abstract: The effect of organic fraction of municipal solid waste (OFMSW) loading rate and particulate size on the sewage sludge (SS) mesophilic anaerobic co-digestion was assessed in continuous stirred tank reactor at hydraulic retention time of 20 days. The SS–OFMSW mixture composed by 54% of the volatile solids fed (inlet-VS), at OLR of 3.1 kg{sub COD} m{sup −3} d{sup −1} (1.9 kg{sub VS} m{sup −3} d{sup −1}), showed the highest increment on the volumetric methane production and yield of +200% and +59% respectively, under stable conditions. The effect of particulate size was assessed with the same mixture and same operational conditions but reducing the OFMSW particulate size from 20 mm to 8 mm with the aim to improve the hydrolysis step, but the results showed any influence in the OFMSW particulate size range analysed. In addition, specific biomass activity was assessed at the end of each co-digestion period. Results showed that OFMSW promoted β-oxidation syntrophic acetogens and the acetoclastic methanogens activity; although the last increase of the OFMSW percentage (from 47% to 54% inlet-VS) affected negatively the specific substrate activity, but not inhibitory effect was observed. Therefore, the results obtained in the continuous experiment could be related with some inhibitory or toxic effect and not due to hydrolysis limitation. The specific biomass activity test was demonstrated to be an interesting tool to evaluate and control the co-digestion process, especially when conventional parameters did not explain the behaviour of the biological system.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Revealing the Size-Dependent d–d Excitations of Cobalt Nanoparticles Using Soft X-ray Spectroscopy

Cobalt-based catalysts are widely used to produce liquid fuels through the Fischer-Tropsch (FT) reaction. However, the cobalt nanocatalysts can exhibit intriguing size-dependent activity whose origin remains heavily debated. To shed light on this issue, the electronic structures of cobalt nanoparticles with size ranging from 4 to 10 nm are studied using soft X-ray absorption (XAS) and resonant inelastic X-ray scattering (RIXS) spectroscopies. The RIXS measurements reveal the significant size-dependent d-d excitations, from which we determine that the crystal-field splitting energy 10Dq changes from 0.6 to 0.9 eV when the particle size is reduced from 10 to 4 nm. The finding that larger Co nanoparticles have smaller 10Dq value is further confirmed by the Co L-edge RIXS simulations with atomic multiplet code. Furthermore, our RIXS results demonstrate a stronger Co-O bond in smaller Co nanoparticles, which brings in further insight into their size-dependent catalytic performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Dynamic Life-Cycle Analysis of Fast Pyrolysis Biorefineries: Impacts of Feedstock Moisture Content and Particle Size

The commercialization of biorefineries has been met with significant obstacles due to the technical difficulties of handling solid biomass feedstocks, which are highly variable in physical properties and chemical compositions. An understanding of the principles of unit operations along the supply chain is key to the success of the biofuel industry. This study applies a dynamic life-cycle analysis (DLCA) methodology by developing quantitative relationships between the inputs and outputs for each unit operation based on scientific understanding of the causal effects. Using the DLCA, we assessed system sustainability of drop-in fuel production from fast pyrolysis of pine residues followed by hydro-processing. Life-cycle greenhouse gas (GHG) emissions were calculated for 4641 runs involving two key feedstock parameters: moisture content after field drying and particle size of the feed to pyrolyzer. Moisture contents varied between 25% and 35%, while particle sizes varied between 0.5 and 5 mm in these runs. The life-cycle GHG emissions of these cases vary from 22 to 40 g/MJ. Close examination of each unit operation's contribution to the total GHG emissions reveals that low moisture content after field drying produces savings in energy consumption during feedstock transportation and on-site drying. However, although small particle size leads to overall higher fuel yield, it also requires a significant amount of energy for feedstock size reduction and fuel production. The energy penalty outweighs the benefit of increased fuel yields, especially when fine particles (<1 mm) are used for pyrolysis; thus, small particle size leads to increased GHG emissions overall. The results highlight the trade-offs between the energy demand for preprocessing and the conversion yields, which can be addressed with DLCA.

09 BIOMASS FUELS↗
DOE OSTI2014

Size Dependence of Atomically Precise Gold Nanoclusters in Chemoselective Hydrogenation and Active Site Structure

We here investigate the catalytic properties of water-soluble Aun(SG)m nanocluster catalysts (H-SG = glutathione) of different sizes, including Au15(SG)13, Au18(SG)14, Au25(SG)18, Au38(SG)24, and captopril-capped Au25(Capt)18 nanoclusters. These Aun(SR)m nanoclusters (-SR represents thiolate generally) are used as homogeneous catalysts (i.e., without supports) in the chemoselective hydrogenation of 4-nitrobenzaldehyde (4-NO2PhCHO) to 4-nitrobenzyl alcohol (4-NO2PhCH2OH) in water with H2 gas (20 bar) as the hydrogen source. These nanocluster catalysts, except Au18(SG)14, remain intact after the catalytic reaction, evidenced by UV-vis spectra which are characteristic of each sized nanoclusters and thus serve as spectroscopic fingerprints . We observe a drastic size-dependence and steric effect of protecting ligands on the gold nanocluster catalysts in the hydrogenation reaction. Density functional theory (DFT) modeling of the 4-nitrobenzaldehyde adsorption shows that both the CHO and NO2 groups are in close interact with the S-Au-S staples on the gold nanocluster surface; the adsorption of the 4-nitrobenzaldehyde molecule on the four different sized Aun(SR)m nanoclusters are moderately strong and similar in strength. The DFT results suggest that the catalytic activity of the Aun(SR)m nanoclusters is primarily determined by the surface area of the Au nanocluster, consistent with the observed trend of the conversion of 4-nitrobenzaldehyde versus the cluster size. Overall, this work offers the molecular insight into the hydrogenation of 4-nitrobenzaldehyde and the catalytically active site structure on gold nanocluster catalysts.

Au nanocluster↗
DOE OSTI2012

Influence of charging process and size distribution of dust grain on the electric conductivity of dusty plasma

The effects of dust size distribution and charging process of dust grains on the complex electric conductivity of dusty plasmas have been investigated in the present paper. Comparisons are made between real dusty plasma in which there are many different dust grain species and the mono-sized dusty plasma (MDP) in which there is only one kind of dust grain whose size is the average dust size. In some cases the complex electric conductivity of real dusty plasma is larger than that of MDP, while in other cases it is smaller than that of MDP, it depends on the dust size distribution function.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗