Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Nanoplates”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

High Thermoelectric Performance in 2D Sb 2 Te 3 and Bi 2 Te 3 Nanoplate Composites Enabled by Energy Carrier Filtering and Low Thermal Conductivity

Thermoelectrics are an important class of materials with great potential in alternative energy applications. In this study, two-dimensional (2D) nanoplates of the layered chalcogenides, Sb 2 Te 3 and Bi 2 Te 3 , are synthesized and composites of the two are investigated for their thermoelectric properties. The two materials, Sb 2 Te 3 and Bi 2 Te 3 , were synthesized as hexagonal, 2D nanoplates via a colloidal polyol route. The as-synthesized Sb 2 Te 3 and Bi 2 Te 3 vary drastically from one another in their lateral and vertical dimensions as revealed by scanning electron microscopy and atomic force microscopy. The single crystalline nanoplate nature is deduced by high-resolution transmission electron microscopy and selected area electron diffraction. Nanoplates have well-defined hexagonal facets as seen in the scanning and transmission electron microscopy images. The nanoplates were consolidated as an anisotropic nanostructured pellet via spark plasma sintering. Preferred orientation observed in the powder X-ray diffraction pattern and scanning electron microscopy images of the fractured pellets confirm the anisotropic structure of the nanoplates. Thermoelectric properties in the parallel and perpendicular directions were measured, revealing strong anisotropy with a significant reduction to thermal conductivity in the perpendicular direction due to increased phonon scattering at nanoplate interfaces. All compositions, except that of the 25% Bi 2 Te 3 nanoplate composite, behave as degenerate semiconductors with increasing electrical resistivity as the temperature increases. The Seebeck coefficient is also increased dramatically in the nanocomposites, the highest reaching 210 μV/K for 15% Bi 2 Te 3 . The increase in Seebeck is attributed to energy carrier filtering at the nanoplate interfaces. Overall, these enhanced thermoelectric properties lead to a drastic increase in the thermoelectric performance in the perpendicular direction, with zT ~ 1.26, for the 15% Bi 2 Te 3 nanoplate composite at 450 K.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Reversible Physical Gelation of Thermotropic Liquid Crystals Driven by Nanoplate Self-Assembly

Physically gelled soft materials, driven by the self-assembly of low-molecular-mass gelators (LMGs), have emerged as a platform for designing advanced gels that exhibit reversible gelation and property tunability. Liquid crystal (LC) gels are of great interest due to their supramolecular orderings as gel hosts and their enhanced electro-optical properties. In this study, we demonstrate the physical gelation of a nematic LC driven by nanoplate self-assembly, expanding the concept of gelators from small molecules to nanoparticles. These nanoplates are functionalized with promesogenic ligands and form a fibrillar network in LCs with face-to-face interplate stacking, resembling LMGs. The critical gelation volume fraction in the tilt test is only 0.14 v %, comparable to values reported for LMGs. Rheological analyses confirm viscoelastic properties characteristic of gelation. In situ small-angle X-ray scattering (SAXS) characterizes the formation of nanoplate networks in the LC with decreasing temperature, wherein LC mesogens become trapped in pores. Molecular dynamics (MD) simulations reveal that the interaction between ligand-coated nanoplates and LC-forming mesogens induces a multidomain LC structure, increasing friction between LC domains and stabilizing the gel. This study establishes direct relationships among molecular interactions, nanostructures, and mechanical properties in physically gelled LCs. In conclusion, the findings inspire the future gelator design of both LMGs and nanoplates, with potential applicability in bioscaffold engineering and liquid crystalline nanocomposites.

36 MATERIALS SCIENCE↗
DOE OSTI2023

One-Step Solution Patterning for Two-Dimensional Perovskite Nanoplate Arrays

Two-dimensional perovskite crystals have attracted significant attention for their diverse optoelectronic characteristics, owing to their superior semiconducting properties. However, the majority of studies to date have focused on single crystals, which pose challenges for integration into device arrays due to their incompatibility with selective growth or conventional lithography techniques. Here, a facile one-step solution process for synthesizing 2D perovskite crystal arrays is proposed through meniscus-guided coating on patterned substrates. Here we further utilized this method for the synthesis of lateral heterostructure nanoplate arrays. Six different 2D perovskite nanoplate arrays, including epitaxial heterostructures, are successfully realized. Optical and crystallographic characterizations show the high optical performance and crystallinity of the nanoplates. Moreover, this method is further employed to prepare high-performance 2D perovskite nanoplate photosensor arrays. This strategy can be utilized as a guideline for the fundamental investigation of optical properties and the development of high-performance optoelectronics of perovskite materials including photosensors and displays.

2D perovskite nanoplates↗
DOE OSTI2024

Defect‐Free Nanowelding of Bilayer SnSe Nanoplates

Nanowelding is a bottom‐up technique to create custom‐designed nanostructures and devices beyond the precision of lithographic methods. Here, a new technique is reported based on anisotropic lubricity at the van der Waals interface between monolayer and bilayer SnSe nanoplates and a graphene substrate to achieve precise control of the crystal orientation and the interface during the welding process. As‐grown SnSe monolayer and bilayer nanoplates are commensurate with graphene's armchair direction but lack commensuration along graphene's zigzag direction, resulting in a reduced friction along that direction and a rail‐like, 1D movement that permits joining nanoplates with high precision. This way, molecular beam epitaxially grown SnSe nanoplates of lateral sizes 30–100 nm are manipulated by the tip of a scanning tunneling microscope at room temperature. In situ annealing is applied afterward to weld contacting nanoplates without atomic defects at the interface. This technique can be generalized to any van der Waals interfaces with anisotropic lubricity and is highly promising for the construction of complex quantum devices, such as field effect transistors, quantum interference devices, lateral tunneling junctions, and solid‐state qubits.

2D ferroelectrics↗
DOE OSTI2025

Modulating the Electronic Transport of 2D Sb2Te3 Nanoplates by Coinage Metal Intercalation

Thermoelectric materials are particularly relevant to the current energy infrastructure and demands of the 21st century, converting waste heat into usable electricity. The solution intercalation of zerovalent copper into Sb2Te3 nanoplates, a well-established thermoelectric material, is reported. The copper intercalant is homogeneously distributed throughout the nanoplates, confirmed by scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy. The copper composition was shown to be 6 at. % by X-ray photoelectron spectroscopy. Copper ordering within the van der Waals gaps of the nanoplates is confirmed by selected area electron diffraction. Fabrication and thermoelectric property measurements of single-crystal Sb2Te3 and Cu-Sb2Te3 nanoplate devices show effective modulation of electrical conductivity and Seebeck coefficient with Cu intercalation. X-ray photoelectron spectroscopic studies in the valence-band region reveal additional electronic states from copper that appear near the Fermi energy, postulated to act as electron acceptors, leading to modulation of the electronic transport properties.

2D nanoplates↗
DOE OSTI2025

Size‐Controlled Cobalt Nanoplates and Their Impact on Oxygen Evolution Catalysis

Controlling the size of nanoparticles is important in catalytic reactions, not only for tuning the surface area but also for modifying the electronic structure. However, achieving precise size control in 2D structures remains challenging. In this work, we demonstrate precise size control of cobalt nanoplates, ranging from 19 nm to 80 nm, which is achieved by tuning the ratio of two surfactants used in the synthesis. The 19 nm of Co nanoplates exhibit higher oxygen evolution reaction activity due to a higher proportion of {10$\overline{1}$1} to {0001} facets. In conclusion, this size control allows systematic investigation into how nanoplate dimensions influence catalytic performance in the oxygen evolution reaction, offering new insights into structure-activity relationships of cobalt nanocatalysts.

defect↗
DOE OSTI2021

Cluster defects in gibbsite nanoplates grown at acidic to neutral pH

Gibbsite [α-Al(OH) 3 ] is the solubility limiting phase for aluminum across a wide pH range, and it is a common mineral phase with many industrial applications. The growth mechanism of this layered-structure material, however, remains incompletely understood. Synthesis of gibbsite at low to circumneutral pH yields nanoplates with substantial interlayer disorder. Here we examine defects in this material in detail, and the effects of recrystallization in highly alkaline sodium hydroxide solution at 80 °C. We employed a multimodal approach, including scanning electron microscopy, magic-angle spinning nuclear magnetic resonance (MAS-NMR), Raman and infrared spectroscopies, X-ray diffraction (XRD), and X-ray total scattering pair distribution function (XPDF) analysis to characterize the ageing of the nanoplates over several days. Additionally, XRD and XPDF indicate that gibbsite nanoplates precipitated at circumneutral pH contain dense, truncated sheets imparting a local difference in interlayer distance. These interlayer defects appear well described by flat Al 13 aluminum hydroxide nanoclusters nearly isostructural with gibbsite sheets present under synthesis conditions and trapped as interlayer inclusions during growth. Ageing at elevated temperature in alkaline solutions gradually improves crystallinity, showing a gradual increase in H-bonding between interlayer OH groups. Between 7 to 8 vol% of the initial gibbsite nanoparticles exhibit this defect, with the majority of differences disappearing after 2–4 hours of recrystallization in alkaline solution. The results not only identify the source of disorder in gibbsite formed under acidic/neutral conditions but also point to a possible cluster-mediated growth mechanism evident through inclusion of relict oligomers with gibbsite-like topology trapped in the interlayer spaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Synchrotron X-ray-induced Synthesis of Copper Hydroxide Nitrate Nanoplates on Cu Thin Films in an Ambient Atmosphere

Synchrotron X-rays are widely used for material characterizations. However, they can also ionize atoms and molecules to damage and manipulate probed materials. We report here an X-ray-induced growth of copper hydroxide nitrate, Cu 2 (OH) 3 NO 3 , on copper thin films in the ambient atmosphere without solvents and thermal treatment. In situ synchrotron X-ray diffraction measurements showed that the time-dependent growth process of the Cu 2 (OH) 3 NO 3 is accompanied by the consumption of Cu metal and can be described by a sigmoidal model. The growth rate was reduced after the initial fast growth period. Scanning electron microscopy (SEM) images show that the isolated islands of Cu 2 (OH) 3 NO 3 nanoplates formed in the beginning, which grew together with new nanoplates formed under continued X-ray irradiation. The result demonstrated that high-flux synchrotron X-rays may provide an unconventional approach to synthesizing and manipulating materials, which will inspire future investigation both experimentally and theoretically.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Activity and selectivity for CO 2 methanation of clusters and nanoplates of ruthenium dispersed on ceria: In-situ studies with XAFS and DRIFTS

The performance of Ru/CeO 2 catalysts under CO 2 hydrogenation conditions was studied using in situ X-ray absorption fine structure (XAFS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to understand the structural evolution and chemical nature of each component under reaction conditions. The catalysts were prepared using a reverse microemulsion method that maximized the dispersion of RuOx particles on ceria. A RuO x → Ru transformation was observed upon exposure of the RuO x /CeO 2 systems to H 2 at 250 °C. For a sample with 5% molar Ru, two-dimensional clusters (2-4 atoms) of Ru formed on top of the ceria support. An increase in the loading of ruthenium to 20% molar led to the formation of nanoplates of the metal 2-3 atomic layers thick. Both Ru structures were highly dispersed on ceria. They were oxidized after exposure to CO 2 at 250 °C. However, under CO 2 /H 2 mixture, they remained in a metallic state as two-dimensional clusters and nanoplates. In situ DRIFTS studies, the 5% and 20% Ru/CeO 2 catalysts showed distinct reaction intermediates when exposed to CO 2 or CO 2 /H 2 (1/4) reaction mixtures. Normalized to the Ru molar percentage, the 5% Ru/CeO 2 system was the most active catalyst exhibiting a selectivity of ~ 60% CH 4 and 40% CO at 250 °C. On the other hand, under the same reaction conditions, the 20% Ru/CeO 2 system was less active but had a CH 4 selectivity close to 80%. In conclusion, these results highlight the importance of the structure of the metallic Ru particles as a factor that determines the catalytic performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Structural Design of Bismuth Telluride Nanoplates through Process Variables

Binary pnictogen chalcogen compounds, primarily bismuth tellurides and selenides, are of great interest due to their applications in emerging quantum devices, as well as thermoelectric generators. The performance of bismuth telluride in these roles depends on its structure at the nanoscale, particularly the size, shape, and crystallinity of its nanocrystalline forms. However, current methods for controlling these features are often slow, inconsistent, or difficult to scale. Here, we demonstrate that through a solvothermal synthesis and hot injection process, precise control over the morphology of bismuth telluride nanoplates is possible with independent tuning of process variables, such as temperature and reaction time. We find that the nanoplate shape and internal porosity vary systematically with synthesis temperature and that the same morphological outcomes can be rapidly achieved at a fixed temperature by adjusting reaction duration. These results reveal that both the temperature and time can independently direct bismuth telluride morphological features, allowing for rapid, tunable synthesis strategies. Our approach offers a scalable framework, not only for bismuth telluride but also for related layered chalcogenides used in energy harvesting and quantum technologies.

Ackley, Jordan [Boise State Univ., ID (United Stat↗
DOE OSTI2024

Effect of Adsorbed Carboxylates on the Dissolution of Boehmite Nanoplates in Highly Alkaline Solutions

Understanding the dissolution of boehmite in highly alkaline solutions is important to the processing of the complex nuclear wastes stored at the Hanford (WA) and Savannah River (SC) sites. Here, we report the adsorption of model carboxylate anions on boehmite nanoplates in alkaline solutions and their effects on subsequent boehmite dissolution in 3 M NaOH at 80 °C. Although expectedly lower than at circumneutral pH, adsorption of oxalate at pH 13 at room temperature was significant and remained so through a linear decrease to 3 M NaOH conditions with no evidence for the appearance of new phases. Modeling of the adsorption data and rate were consistent with the formation of outer-sphere surface complexes. By using these conditions to preload the boehmite nanoplates with oxalate, and separately acetate, we measured and compared their dissolution behavior at 80 °C and observed a clear suppression of the dissolution rate for the case of adsorbed oxalate by 23% and for adsorbed acetate by 10% compared to pure solids. Ex situ scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterization revealed no detectable difference in the morphologic evolution of the dissolving boehmite materials. In conclusion, we nonetheless conclude that pre-adsorbed carboxylate anions, even as nominally weakly bound outer-sphere complexes, can persist on the surface through highly alkaline conditions, decreasing the density of dissolution-active sites and thereby adding an extrinsic control on the dissolution rate.

Adsorption kinetics↗
DOE OSTI2025

Mesocrystal growth through oriented sliding and attachment of nanoplates

Oriented attachment is a critical, yet poorly understood, crystal growth pathway based on the self-assembly of nanocrystals. During oriented attachment, solvent-separated particles align and coalesce through forces that enable precise rotation and translation. While prior studies emphasized intragap forces driving crystallographic alignment, the forces enabling uniform stacking and superlattice formation remain unclear. Here, we demonstrate how macroscopic gibbsite mesocrystals emerge from nanoplates guided into staggered positions by directional sliding. Electron microscopy and X-ray scattering reveal the monoclinic superlattice structure, based on nanoplate stacking with a uniform ≈50° stagger along the gibbsite [010] direction. In situ liquid-cell TEM captures preferential sliding along the gibbsite [010] direction, decelerating with increasing particle overlap. Molecular dynamics simulations reveal that this staggered arrangement corresponds to a global free-energy minimum, rather than full alignment. The simulations also confirm that sliding along the [010] direction is energetically favored and provide insight into the role of interfacial water in achieving long-range ordered assemblies. These insights highlight the energy landscape’s role in oriented attachment, with implications for material synthesis and hierarchical structures in nature.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Printed copper-nanoplate conductor for electro-magnetic interference

As one of the conductive ink materials with high electric conductivity, elemental copper (Cu) based nanocrystals promise for printable electronics. Here, single crystalline Cu nanoplates were synthesized using a facile hydrothermal method. Size engineering of Cu nanoplates can be rationalized by using the LaMer model and the versatile Cu conductive ink materials are suitable for different printing technologies. The printed Cu traces show high electric conductivity of 6 MS m -1 , exhibiting electro-magnetic interference shielding efficiency value of 75 dB at an average thicknesses of 11 μ m. Together with flexible alumina ceramic aerogel substrates, it kept 87% conductivity at the environmental temperature of 400 °C, demonstrating the potential of Cu conductive ink for high-temperature printable electronics applications.

Materials Science↗
DOE OSTI2023

Fe-N 4 O-C Nanoplates Covalently Bonding on Graphene for Efficient CO 2 Electroreduction and Zn-CO 2 Batteries

Electrochemical carbon dioxide (CO 2 ) reduction into value-added products holds great promise in moving toward carbon neutrality but remains a grand challenge due to lack of efficient electrocatalysts. Herein, the nucleophilic substitution reaction is elaborately harnessed to synthesize carbon nanoplates with a Fe-N 4 O configuration anchored onto graphene substrate (Fe-N 4 O-C/Gr) through covalent linkages. Density functional theory calculations demonstrate the unique configuration of Fe-N 4 O with one oxygen (O) atom in the axial direction not only suppresses the competing hydrogen evolution reaction, but also facilitates the desorption of *CO intermediate compared with the commonly planar single-atomic Fe sites. The Fe-N 4 O-C/Gr shows excellent performance in the electroreduction of CO 2 into carbon monoxide (CO) with an impressive Faradaic efficiency of 98.3% at -0.7 V versus reversible hydrogen electrode (RHE) and a high turnover frequency of 3511 h -1 . Furthermore, as a cathode catalyst in an aqueous zinc (Zn)-CO 2 battery, the Fe-N 4 O-C/Gr achieves a high CO Faradaic efficiency (≈91%) at a discharge current density of 3 mA cm -2 and long-term stability over 74 h. Here this work opens up a new route to simultaneously modulate the geometric and electronic structure of single-atomic catalysts toward efficient CO 2 conversion.

25 ENERGY STORAGE↗
DOE OSTI2025

Mechanistic Transformation of CuI Nanoparticles Into Oxidation‐Resistant 2D Copper Nanoplates

Unconventional phase transformations reveal new crystallization mechanisms, yet direct observation of such pathways during nanoscale solution-phase synthesis remains challenging. This study uncovers an atypical growth process in which thermodynamically stable CuI nanoparticles (NPs) transform into high-energy 2D Cu plates. Using a combination of in situ transmission electron microscopy, ex situ structural analysis, and density functional theory calculations shows that the formation of structural defects induced by hexadecylamine and chloride ions facilitates the transformation by promoting surface iodine vacancies. The resulting Cu{111} nanoplates, with ultrathin thicknesses (≈4 nm) and exceptionally high aspect ratios (≈450), display enhanced oxidation resistance and long-term stability under ambient conditions. This resistance is attributed to the close-packed {111} facets, which suppress chemical oxidation even after extended exposure to air over 100 days. These findings provide new insights into non-classical crystallization pathways in metal nanomaterials and suggest a versatile approach for preparing oxidation-resistant, structurally defined Cu nanostructures.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Enabling AC electroluminescence in quasi-2D perovskites by uniformly arranging different-n-value nanoplates to allow bidirectional charge transport

Perovskite light-emitting diodes (LEDs) are normally operated under forward direct current (DC) to realize electron/hole injection at cathode/anode surfaces. In this work, we demonstrate an alternating current (AC) driven LED enabled by bi-directionally allowed charge transport in quasi-2D perovskite (PEA 2 MA n-1 PbnI 3n+1 ) film. Essentially, the bi-directional charge transport is realized by uniformly arranging different-n-value 2D nanoplates together with symmetrically designed anode/cathode interfaces, which can allow injected electrons and holes to form light-emitting states under both forward and reverse biases, leading to an AC electroluminescence (EL) with the device architecture of ITO/PEI/PEDOT:PSS/PEA 2 MA n-1 PbnI 3n+1 /P3HT/PEI/Ag. The high AC EL performance was achieved with the radiance = 24 W Sr -1 m -2 and 18.3 W Sr -1 m -2 and EQE = 12.5% and 3.7% under forward and reverse biases. Furthermore, the device-operational stability was largely improved with the half-intensity time of T 50 = 11.0 h under AC bias (+2 V/-2 V, 50 Hz) as compared to T 50 = 3.9 h under forward bias (+2 V/0 V, 50 Hz).

36 MATERIALS SCIENCE↗
DOE OSTI2021

Scalable nanomanufacturing of chalcogenide inks: a case study on thermoelectric V–VI nanoplates

Solution-processed semiconducting main-group chalcogenides (MMCs) have attracted increasing research interest for next-generation device technologies owing to their unique nanostructures and superior properties. To achieve the full potential of MMCs, the development of highly universal, scalable, and sustainable synthesis and processing methods of chalcogenide particles is thus becoming progressively more important. Here we studied scalable factors for the synthesis of two-dimensional (2D) V–VI chalcogenide nanoplates (M 2 Q 3 : M = Sb, Bi; Q = Se, Te) and systematically investigated their colloidal behaviour and chemical stability. Based on a solvent engineering technique, we demonstrated scale-up syntheses of MMCs up to a 900% increase of batch size compared with conventional hydrazine-based gram-level syntheses, and such a scalable approach is highly applicable to various binary and ternary MMCs. Furthermore, we studied the stability of printable chalcogenide nanoparticle inks with several formulation factors including solvents, additives, and pH values, resulting in inks with high chemical stability (>4 months). As a proof of concept, we applied our solution-processed chalcogenide particles to multiple additive manufacturing methods, confirming the high printability and processability of MMC inks. Furthermore, the ability to combine the top-down designing freedom of additive manufacturing with bottom-up scalable synthesis of chalcogenide particles promises great opportunities for large-scale design and manufacturing of chalcogenide-based functional devices for broad application.

36 MATERIALS SCIENCE↗