Results for “metal nanoparticles” — Page 37

DOE OSTI2020

Synthesis and Characterization of Pd-based Nanomaterials

Bimetallic nanoparticles (BNPs) consist of two different types of metals or alloys that are bonded together. Unique properties such as optical, electronic, thermal, and catalytic effects differ for each type of BNP. Important BNPs range from Au-Pd, Ag- Pt, Au-Pt, and Ag-Ni. Pd bimetallic nanoparticles are of interest due to their many applications such as catalysis and sensing. Bimetallic catalysts have increase reaction rates and have improved catalyst stability through the geometry and ligand distribution. Pd nanoparticles are considered to be a strong catalyst due to their high activity at low temperatures and high tolerance to moisture. The catalytic properties of bimetallic nanoparticles depend on the structural properties such as size and shape. Core-shell, hollow structure, and multi-shell alloy are three possible structures nanoparticles can form as bimetallic catalysts. BNPs can be synthesized through different methods to control the size, shape, and structure. To obtain different morphologies, a variety of methods can be performed. Different methods can range from the usage of the glancing angle deposition (GLAD) to the galvanic replacement reaction, but the methods all depend on the properties of the metals. The galvanic displacement reaction was the method used to obtain Pd-based nanoparticles. This reaction is best know for obtaining hollow shaped NPs. To determine what redox process was preformed, the activity series of metals was used. From the activity series of metals, silver (Ag) was selected to preform Pd-based nanoparticles. Objectives: Synthesize Ag nanoparticles and Ag-Pd nanoparticles to understand the morphology. Characterize the synthesized nanoparticles using scanning electron microscopy (SEM), phase analysis light scattering (PALS), dynamic light scattering (DLS), energy dispersive X-ray spectroscopy (EDS), and UV-Vis spectroscopy. Results: In the UV-Vis spectrum, the Ag-Pd bimetallic NP's plasmon band decreased as the volume of palladium increased. The surface charge increases as the concentration of palladium increases. The Pd{sup 2+} ions interact with the sodium citrate surface, and decrease the negative charge. Conclusion: Ag-Pd nanoparticles were successfully created and stabilized with sodium citrate. The addition of Pd decreased the prominent plasmon band of the Ag nanoparticles. The SEM analysis showed that Ag nanoparticles had a well-defined structure, while the Ag-Pd nanoparticles showed hollow and rough structure. The EDX analysis confirmed the presence of silver and palladium. This material can be used in many industrial and research fields such as organic synthesis, fuel cells, and environmental sensing and remediation.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2021

Structural and Catalytic Properties of Isolated Pt 2+ Sites in Platinum Phosphide (PtP 2 )

This article describes the synthesis and catalytic properties of supported, 2-3 nm platinum phosphide (PtP 2 ) nanoparticles (NPs). Depending on the P loading, two PtP 2 structures are formed, that is, a PtP 2 surface on a (metallic) Pt core (Pt@PtP 2 ) and single-phase PtP 2 NPs. The structures were determined using extended X-ray absorption fine structure , in situ synchrotron X-ray diffraction, and scanning transmission electron microscopy. In PtP 2 NPs, Pt 2+ ions are geometrically isolated by P 2 2- ions, at a Pt-Pt distance of 4.02 Å, which is much longer than 2.78 Å in (metallic) Pt NPs. The oxidation state of Pt in PtP 2 NPs was determined by in situ X-ray absorption near-edge structure and in situ X-ray photoelectron spectroscopy and was found to be consistent with Pt 2+ ions even after treatment in H 2 at 550 °C. Unlike Pt NPs, which are highly active for propylene hydrogenation at room temperature, PtP 2 NPs are not active below about 150 °C, suggesting the absence of metallic surface Pt. In contrast to metallic Pt, which is poorly selective for acetylene hydrogenation, PtP 2 NPs display high selectivity toward ethylene. PtP 2 , also has high olefin selectivity for propane dehydrogenation, although the rate per g Pt is about 7 times lower than that of metallic Pt NPs of the same size. In situ resonant inelastic X-ray scattering spectroscopy shows that the energy of the filled Pt 5d valence orbitals is 1.5 eV lower than that of metallic Pt, which leads to weaker adsorbate binding consistent with its catalytic properties. Here, a H 2 -stable Pt 2+ site suggests different catalytic applications for these catalysts as compared to Pt NPs.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS2006

Metallized Gelled Propellants Combustion Experiments in a Pulse Detonation Engine

A series of combustion tests were performed with metallized gelled JP 8/aluminum fuels in a Pulse Detonation Engine (PDE). Nanoparticles of aluminum were used in the 60 to 100 nanometer diameter. Gellants were also of a nanoparticulate type composed of hydrocarbon alkoxide materials. Using simulated air (a nitrogen-oxygen mixture), the ignition potential of metallized gelled fuels with nanoparticle aluminum was investigated. Ignition of the JP 8/aluminum was possible with less than or equal to a 23-wt% oxygen loading in the simulated air. JP 8 fuel alone was unable to ignite with less than 30 percent oxygen loaded simulated air. The tests were single shot tests of the metallized gelled fuel to demonstrate the capability of the fuel to improve fuel detonability. The tests were conducted at ambient temperatures and with maximal detonation pressures of 1340 psia.

Palaszewski, Bryan↗

DOE OSTI2022

Method for preparation of nanoceria supported atomic noble metal catalysts and the application of platinum single atom catalysts for direct methane conversion

Described are methods for converting methane to olefins, aromatics, or a combination thereof using a single atom catalyst comprising CeO2 nanoparticles impregnated with individual atoms of noble metals including Pt, Pd, Rh, Ru, Ag, Au, Ir, or a combination thereof. These single atom catalysts of the present invention are heated with methane to form olefins and aromatics.

Wang, Chao↗

DOE OSTI2020

Method for producing nanoparticles and the nanoparticles produced therefrom

Disclosed herein is a method comprising disposing a container containing a metal and/or ferromagnetic solid and abrasive particles in a static magnetic field; where the container is surrounded by an induction coil; activating the induction coil with an electrical current, to heat up the metallic or ferromagnetic solid to form a fluid; generating sonic energy to produce acoustic cavitation and abrasion between the abrasive particles and the container; and producing nanoparticles that comprise elements from the container, the metal and/or the ferromagnetic solid and the abrasive particles. Disclosed herein too is a composition comprising first metal or a first ceramic; and particles comprising carbides and/or nitrides dispersed therein. Disclosed herein too is a composition comprising nanoparticles comprising chromium carbide, iron carbide, nickel carbide, γ-Fe and magnesium nickel.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Method for producing nanoparticles and the nanoparticles produced therefrom

Disclosed herein is a method comprising disposing a container containing a metal and/or ferromagnetic solid and abrasive particles in a static magnetic field; where the container is surrounded by an induction coil; activating the induction coil with an electrical current, to heat up the metallic or ferromagnetic solid to form a fluid; generating sonic energy to produce acoustic cavitation and abrasion between the abrasive particles and the container; and producing nanoparticles that comprise elements from the container, the metal and/or the ferromagnetic solid and the abrasive particles. Disclosed herein too is a composition comprising first metal or a first ceramic; and particles comprising carbides and/or nitrides dispersed therein. Disclosed herein too is a composition comprising nanoparticles comprising chromium carbide, iron carbide, nickel carbide, γ-Fe and magnesium nitride.

Manuel, Michele Viola↗

DOE OSTI2023

Method for producing nanoparticles and the nanoparticles produced therefrom

Disclosed herein is a method comprising disposing a container containing a metal and/or ferromagnetic solid and abrasive particles in a static magnetic field; where the container is surrounded by an induction coil; activating the induction coil with an electrical current, to heat up the metallic or ferromagnetic solid to form a fluid; generating sonic energy to produce acoustic cavitation and abrasion between the abrasive particles and the container; and producing nanoparticles that comprise elements from the container, the metal and/or the ferromagnetic solid and the abrasive particles. Disclosed herein too is a composition comprising first metal or a first ceramic; and particles comprising carbides and/or nitrides dispersed therein. Disclosed herein too is a composition comprising nanoparticles comprising chromium carbide, iron carbide, nickel carbide, γ-Fe and magnesium nitride.

Manuel, Michele Viola↗

DOE OSTI2023

Method for producing nanoparticles and the nanoparticles produced therefrom

Disclosed herein is a method comprising disposing a container containing a metal and/or ferromagnetic solid and abrasive particles in a static magnetic field; where the container is surrounded by an induction coil; activating the induction coil with an electrical current, to heat up the metallic or ferromagnetic solid to form a fluid; generating sonic energy to produce acoustic cavitation and abrasion between the abrasive particles and the container; and producing nanoparticles that comprise elements from the container, the metal and/or the ferromagnetic solid and the abrasive particles. Disclosed herein too is a composition comprising first metal or a first ceramic; and particles comprising carbides and/or nitrides dispersed therein. Disclosed herein too is a composition comprising nanoparticles comprising chromium carbide, iron carbide, nickel carbide, γ-Fe and magnesium nitride.

Manuel, Michele Viola↗

DOE OSTI2020

Predicting metal–metal interactions. II. Accelerating generalized schemes through physical insights

Operando-computational frameworks that integrate descriptors for catalyst stability within catalyst screening paradigms enable predictions of rates and selectivity on chemically faithful representations of nanoparticles under reaction conditions. These catalyst stability descriptors can be efficiently predicted by density functional theory (DFT)-based models. The alloy stability model, for example, predicts the stability of metal atoms in nanoparticles with site-by-site resolution. In this work, we use physical insights to present accelerated approaches of parameterizing this recently introduced alloy-stability model. These accelerated approaches meld quadratic functions for the energy of metal atoms in terms of the coordination number with linear correlations between model parameters and the cohesive energies of bulk metals. By interpolating across both the coordination number and chemical space, these accelerated approaches shrink the training set size for 12 fcc p- and d-block metals from 204 to as few as 24 DFT calculated total energies without sacrificing the accuracy of our model. We validate the accelerated approaches by predicting adsorption energies of metal atoms on extended surfaces and 147 atom cuboctahedral nanoparticles with mean absolute errors of 0.10 eV and 0.24 eV, respectively. This efficiency boost will enable a rapid and exhaustive exploration of the vast material space of transition metal alloys for catalytic applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2022

Controlling melt flow by nanoparticles to eliminate surface wave induced surface fluctuation

The high surface roughness is one of the major challenges encountered in laser metal additive manufacturing (AM) processes, which is closely related to the melt flow behavior. However, how to control the melt flow in laser metal AM processes to improve surface finish is unknown. Here we reveal the effects of nanoparticles on melt flow behavior at every location of melt pool during laser metal AM process for the first time using Al6061 + TiC nanoparticles system and achieve significant improvement of surface finish by using TiC nanoparticles to control the melt flow and damp the surface wave. Based on the in-situ x-ray imaging observation, the surface wave is fully damped after adding TiC nanoparticles, compared with only 56% damping without nanoparticles during LPBF of Al6061. Our in-depth in-situ x-ray imaging analysis and viscosity measurement enable us to identify that nanoparticle-induced increase of viscosity causes the fully damping of the surface wave by (1) increasing the internal fluid friction for more efficient wave amplitude reduction, (2) controlling the melt flow to increase the surface wave number, (3) controlling the melt flow to increase the wave damping time. Furthermore, we also quantified the relative contributions of increasing fluid friction, increasing wave number, and increasing damping time to wave damping, which account for 61%, 25%, and 14%, respectively. Furthermore, our research provides the mechanisms and potential method to address the surface finish challenge in laser metal AM processes.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Effect of grain size on iron-boride nanoglasses

Metallic nanoglasses are made of amorphous grains that are separated by lower-density amorphous boundaries, which have been proposed to enhance plasticity through the deflection of cracks and shear bands at interfaces. It has been difficult to experimentally control grain size and interfacial structure to understand their roles in plastic deformation. Here, we fabricate bulk nanoglasses via compaction and sintering of colloidally synthesized amorphous iron-boride nanoparticles. These nanoglasses have amorphous grains with diameters from 116nm to 576nm and were tested using nanoindentation and micropillar compressions. The nanoglass with a grain size of 576 nm shows the highest elastic modulus and hardness of 101 GPa and 7.4GPa, respectively. Transmission electron microscopy reveals that nanocrystals form within the nanoglasses during compaction. Higher nanocrystal density correlates with higher nanoparticle crystallization enthalpy, an increase in plasticity, and a decrease in yield strength. Plastic strain of 5.0%, yield strength of 3.8GPa, and ultimate compressive strength of 2.7–3.8GPa were achieved. Here we show that the compaction of colloidal metallic glass nanoparticles results in robust bulk samples, with mechanical properties similar to that of other iron-based bulk metallic glasses.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Metallization of 3D Printed Parts for Electrode Fabrication

Additive manufacturing has the potential to fabricate electrodes with extremely small features with control of the electrode structure. However, most of the 3D printing capabilities produce structures made of polymers rather than electrodes which much be metal. This work aims to compare methods of metallization for parts created with additive manufacturing to allow them to be used as electrodes. We used three different methods of metallization: layer-by-layer gold nanoparticle coating, electroless copper deposition, and a combination of the two. We measured the resistance of the samples and observed the uniformity of the coating. We find that the standard electroless deposition procedure and using the layer-by-layer gold as a pretreatment yield similar resistances of less than 1 Ω. However, using gold as a pretreatment has possible cost benefits as compared to the standard electroless deposition procedure. Therefore, if many samples over a long period of time need to be metallized, we recommend using the layer-by-layer process combined with copper electroless deposition.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Rational Design and Synthesis of Hierarchical Porous Mn–N–C Nanoparticles with Atomically Dispersed MnNx Moieties for Highly Efficient Oxygen Reduction Reaction

Developing transition-metal excluding iron and cobalt–nitrogen–carbon (M–N–C) electrocatalysts for the oxygen reduction reaction (ORR) is critical to substantially promote the development of precious-metal-free metal–air batteries and fuel cells. In the work, Mn–N–C nanoparticles with atomically dispersed MnNx moieties were synthesized by pyrolyzing Mn-ion–dual-pyridine coordinated complex, which was obtained via a simple condensation reaction between 2,6-diamino-pyridine and 2,6-diacetyl-pyridine with MnCl 2 as the Mn source. The precursor features with a characteristic structure of dual-pyridine ligand, which possesses a strong coordinating capability for Mn 2+ , facilitating the formation of highly dispersed nitrogen-coordinated Mn sites (MnN x ). Attributed to the highly active atomic MnN x sites, hierarchical pore structure, and high surface area of the Mn–N–C derived from the new precursor, it exhibits outstanding ORR performance in 0.1 M KOH with an almost direct four-electron reaction path and high selectivity of O 2 into H 2 O (low H2O2 production <3.5%). The half-wave potential of Mn–N–C is 0.88 V vs RHE, which is 20 mV higher than that of commercial Pt/C catalyst and reaches to the level of Fe–N–C catalyst obtained by the same method. Meanwhile, the feasibility of Mn–N–C for practical application is validated by its higher-performance power output in Zn–air battery with a maximum power density of 132 mW cm –2 compared to that of Pt/C (121 mW cm –2 ) using the same catalyst loading of 1.0 mg cm –2 . This work develops a convenient route to develop non-Fe or Co–N–C electrocatalyst for the ORR.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Pressure-Dependent Phase Behavior of Chemically Synthesized Ytterbium Hydride Nanoparticles and Confinement in CMK-3

In this work, we developed a chemical synthesis protocol to prepare both spherical and rod shaped YbH x nanoparticles and infiltrate a mesoporous CMK-3 structure with YbH x nanoparticles. The phase evolution of the YbH x nanoparticles was monitored as a function of the pressure in a diamond anvil cell. The cell volume of the Yb atom showed an unexpected positive deviation from the calculated equation of state (EoS) for the α-phase (space group Pnma) of YbH x . Additionally, the β-phase (space group Fm3̅m) YbH x nanoparticles appeared to become amorphous at approximately 27 GPa, although the same behavior was not observed in the Pnma (α-phase). The Pmna phase remained stable (measured up to 59.3 GPa) and showed a significantly higher than expected volume per Yb atom relative to the calculated EoS. This deviation could be attributed to the nanoscale effect on the thermodynamics of ytterbium hydride formation, which could provide a path forward to accessing higher order ytterbium hydrides (YbH x , x > 3) at pressures much lower than in the bulk metal.

diamond anvil cell↗

DOE OSTI2024

Charge‐Programmable Photopolymers for 3D Electronics via Additive Manufacturing

Charge‐programmed 3D printing enables the fabrication of 3D electronics with lightweight and high precision via selective patterning of metals. This selective metal deposition is catalyzed by Pd nanoparticles that are specifically immobilized onto the charged surface and promises to fabricate a myriad of complex electronic devices with self‐sensing, actuation, and structural elements assembled in a designed 3D layout. However, the achievable property space and the material‐performance correlation of the charge‐programmed printing remain unexplored. Herein, a series of photo‐curable resins are designed for unveiling how the charge and crosslink densities synergistically impact the nanocatalyst‐guided selective deposition in catalytic efficiency and properties of the 3D printed charge‐programmed architectures, leading to high‐quality 3D patterning of solid and liquid metals. The findings offer a wide tunability of the structural properties of the printed electronics, ranging from stiff to extreme flexibility. Capitalizing on these results, the printing and successful application of an ultralight‐weight and deployable 3D multi‐layer antenna system operating at an ultrahigh‐frequency of 19 GHz are demonstrated.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Ultimate compressive strength and severe plastic deformation of equilibrated single-crystalline copper nanoparticles

Mechanical properties and deformation mechanisms of defect-free copper nanoparticles are investigated by combining experiments with atomistic simulations. The compressive strength of the particles increases with decreasing size and tends to saturate near the theoretical strength in the small-size limit. In this limit, the intrinsic size dependence of the strength is governed by the stochastic nature of dislocation nucleation near the particle surface. The particle deformation process evolves from the initial strain softening to strain hardening as the particle accumulates residual damage. The normalized strength-size relation for Cu is compared with those for Au, Ni, and Pt. The lack of universal behavior among the four FCC metals is discussed. Heavily deformed Cu nanoparticles develop polycrystalline structures and change the lattice orientation from [111] to [110]. The experiments and simulations reveal the twinning mechanism of the lattice rotation leading to the new grain formation.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Ultimate compressive strength and severe plastic deformation of equilibrated single-crystalline copper nanoparticles

Mechanical properties and deformation mechanisms of defect-free copper nanoparticles are investigated by combining experiments with atomistic simulations. The compressive strength of the particles increases with decreasing size and tends to saturate near the theoretical strength in the small-size limit. In this limit, the intrinsic size dependence of the strength is governed by the stochastic nature of dislocation nucleation near the particle surface. The particle deformation process evolves from the initial strain softening to strain hardening as the particle accumulates residual damage. The normalized strength-size relation for Cu is compared with those for Au, Ni, and Pt. The lack of universal behavior among the four FCC metals is discussed. Heavily deformed Cu nanoparticles develop polycrystalline structures and change the lattice orientation from [111] to [110]. The experiments and simulations reveal the twinning mechanism of the lattice rotation leading to the new grain formation.

36 MATERIALS SCIENCE↗

DOE OSTI2025

An investigation of the physical and chemical changes of Pd nanoparticles on carbon supports in response to the release of hydrogen from aqueous formate solutions

Palladium nanoparticles on carbon supports (Pd/C) are effective for catalyzing hydrogen release from aqueous formate solutions but typically suffer from a gradual decrease of activity. This study finds two primary factors influencing activity: (i) the number of available surface Pd sites, and (ii) metal-support interactions which depend on the nature of the C support. We propose that the Pd/C catalyst is structure insensitive and undergoes Ostwald ripening to yield an active ‘conditioned’ catalyst with dispersion plateauing between ca. 15–20 %. Contrary to earlier studies, in-situ XANES experiments show that PdO is not an active catalyst for formate dehydrogenation. Calcination of Pd/C before dehydrogenation increases the catalytic activity which suggests a beneficial, albeit temporary, modification of the metal support interaction. N-containing supports minimize nanoparticle growth and also increase activity through a metal-support interaction. In conclusion, these findings advance our understanding of catalyst evolution and stability in formate dehydrogenation systems.

Formate dehydrogenation↗