SEARCH · Engineering Papers
Results for “nanostructure”
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.
Electron tomography unravels new insights into fiber cell wall nanostructure; exploring 3D macromolecular biopolymeric nano-architecture of spruce fiber secondary walls
Lignocellulose biomass has a tremendous potential as renewable biomaterials for fostering the “bio-based society” and circular bioeconomy paradigm. It requires efficient use and breakdown of fiber cell walls containing mainly cellulose, hemicellulose and lignin biopolymers. Despite their great importance, there is an extensive debate on the true structure of fiber walls and knowledge on the macromolecular nano-organization is limited and remains elusive in 3D. We employed dual-axis electron tomography that allows visualization of previously unseen 3D macromolecular organization/biopolymeric nano-architecture of the secondary S2 layer of Norway spruce fiber wall. Unprecedented 3D nano-structural details with novel insights into cellulose microfibrils (~2 nm diameter), macrofibrils, nano-pore network and cell wall chemistry (volume %) across the S2 were explored and quantified including simulation of structure related permeability. Matrix polymer association with cellulose varied between microfibrils and macrofibrils with lignin directly associated with MFs. Simulated bio-nano-mechanical properties revealed stress distribution within the S2 and showed similar properties between the idealized 3D model and the native S2 (actual tomogram). Present work has great potential for significant advancements in lignocellulose research on nano-scale understanding of cell wall assembly/disassembly processes leading to more efficient industrial processes of functionalization, valorization and target modification technologies.
High-performance cementitious composites containing nanostructured carbon additives made from charred coal fines
Carbon-based nanomaterials, such as carbon nanoplatelets, graphene oxide, and carbon quantum dots, have many possible end-use applications due to their ability to impart unique mechanical, electrical, thermal, and optical properties to cement composites. Despite this potential, these materials are rarely used in the construction industry due to high material costs and limited data on performance and durability. In this study, domestic coal is used to fabricate low-cost carbon nanomaterials that can be used economically in cement formulations. A range of chemical and physical processing approaches are employed to control the size, morphology, and chemical functionalization of the carbon nanomaterial, which improves its miscibility with cement formulations and its impact on mechanical properties and durability. At loadings of 0.01 to 0.07 wt.% of coal-derived carbon nanomaterial, the compressive and flexural strength of cement samples are enhanced by 24% and 23%, respectively, in comparison to neat cement. At loadings of 0.02 to 0.06 wt.%, the compressive and flexural strength of concrete composites increases by 28% and 21%, respectively, in comparison to neat samples. Additionally, the carbon nanomaterial additives studied in this work reduce cement porosity by 36%, permeability by 86%, and chloride penetration depth by 60%. These results illustrate that low-loadings of coal-derived carbon nanomaterial additives can improve the mechanical properties, durability, and corrosion resistance of cement composites.
Topological transitions, pinning and ratchets for driven magnetic hopfions in nanostructures
Not Available
Kinetic analyses for solid-state phase transition of metastable amorphous-AlO x (2.5 < x ≤ 3.0) nanostructures into crystalline alumina polymorphs
Solid-solid phase change materials (SS-PCMs) hold promise for energy storage/dissipation in batteries and energetic materials. Yet, phase change kinetics for SS-PCMs undergoing metastable to semi-stable/stable phase transformations remain relatively ill-studied because trapping metastable phases remain challenging. Recently, we demonstrated the kinetic entrapment and stabilization of a highly disordered and amorphous Al-oxide phase m-AlO x @C (x~2.5-3.0) via laser ablation synthesis in solution (LASiS). We report here, to our knowledge, the first chemical kinetics analysis for S-S phase transition of the m-AlO 3 @C nanocomposites (< 5–8 nm sizes) into semi-stable equilibrium alumina phases (θ/γ-Al 2 O 3 ) via disproportionation reaction, while releasing excess trapped gases. Our results indicate the atomic density of the AlO 3 structures to be ~5–10 times less than that of the final Al 2 O 3 phases, which led to the hypothesis of a volume shrinkage process during their phase transition. Temperature-dependent X-ray diffraction studies reveal the high-temperature phase transition for m-AlO 3 → θ/γ-Al 2 O 3 to follow contracting volume kinetics model, thereby validating our earlier hypothesis. Using the geometric volume contraction model, reaction kinetics analyses from Arrhenius plots reveal the activation energy barrier for the phase transition to be ~270±11 kJ/mol. This makes the activation energy barrier nearly identical to the oxidation of micron-sized Al particles.
Employing bicontinuous-to-micellar transitions in nanostructure morphology for on-demand photo-oxidation responsive cytosolic delivery and off–on cytotoxicity
PEG- b -PPS bicontinuous nanospheres resist degradation and stably retain payloads within cells. When loaded with a photosensitizing agent, these nanospheres demonstrate off–on inducible photo-responsive release of cytotoxic agents into the cytosol of cells.
Boosting the activity of transition metal carbides towards methane activation by nanostructuring
The interaction of methane with pristine surfaces of bulk MoC and Mo 2 C is known to be weak. In contrast, a series of X-ray photoelectron spectroscopy (XPS) experiments, combined with thermal desorption mass spectroscopy (TDS), for MoC y (y = 0.5–1.3) nanoparticles supported on Au(111)—which is completely inert towards CH 4 —show that these systems adsorb and dissociate CH 4 at room temperature and low CH 4 partial pressure. This industrially-relevant finding has been further investigated with accurate density functional theory (DFT) based calculations on a variety of MoC y supported model systems. The DFT calculations reveal that the MoC y /Au(111) systems can feature low C–H bond scission energy barriers, smaller than the CH 4 adsorption energy. Our theoretical results for bulk surfaces of Mo 2 C and MoC show that a simple Brønsted–Evans–Polanyi (BEP) relationship holds for C–H bond scission on these systems. However, this is not the case for methane activation on the MoC y nanoparticles as a consequence of their unique electronic and chemical properties. Finally, the discovery that supported molybdenum carbide nanoparticles are able to activate methane at room temperature paves the road towards the design of a new family of active carbide catalysts for methane activation and valorisation, with important implications in climate change mitigation and carbon cycle closure.
Liquid nanostructure of choline lysinate with water and a model lignin residue
The structure of the ionic liquid choline lysinate ([Ch][Lys]) and its water mixtures, including a dissolved model lignin residue, guaiacol, is revealed at atomic and nanoscale resolution using neutron diffraction.
Enhanced solar photothermal effect of PANi fabrics with plasmonic nanostructures
The photothermal energy conversion in hanging and floating polyaniline (PANi)-cotton fabrics is investigated using a model based on the heat diffusion equation.
Controlling nanostructure and mechanical properties in triblock copolymer/monomer blends via reaction-induced phase transitions
Explore the source record for details and available documents.
Core–shell nanostructures: perspectives towards drug delivery applications
Nanosystems have shown encouraging outcomes and substantial progress in the areas of drug delivery and biomedical applications.
Co-self-assembly of multiple DNA origami nanostructures in a single pot
We demonstrate co-self-assembly of two distinct DNA origami structures with a common scaffold strand through programmable bifurcation of folding pathways.
Evaluation of electrochemical properties of nanostructured metal oxide electrodes immersed in redox-inactive organic media
Electrochemical impedance measurements of NiO and α-Fe 2 O 3 films immersed in redox-inactive organic media depend on both film morphology and electronic structure.
Role of nanoparticle size and surface chemistry on ion transport and nanostructure of perfluorosulfonic acid ionomer nanocomposites
In this work, we present a systematic investigation of the impact of silica nanoparticle (SiNP) size and surface chemistry on the nanoparticle dispersion state and the resulting morphology and vanadium ion permeability of the composite ionomer membranes. Specifically, Nafion containing a mass fraction of 5% silica particles, ranging in nominal diameters from 10 nm to >1 μm and with both sulfonic acid- and amine-functionalized surfaces, was fabricated. Most notably, an 80% reduction in vanadium ion permeability was observed for ionomer membranes containing amine-functionalized SiNPs at a nominal diameter of 200 nm. Further, these membranes exhibited an almost 400% increase in proton selectivity when compared to pristine Nafion. Trends in vanadium ion permeability within a particular nominal diameter were seen to be a function of the surface chemistry, where, for example, vanadyl ion permeability was observed to increase with increasing particle size for membranes containing unfunctionalized SiNPs, while it was seen to remain relatively constant for membranes containing amine-functionalized SiNPs. In general, the silica particles tended to exhibit a higher extent of aggregation as the size of the particles was increased. From small-angle neutron scattering experiments, an increase in the spacing of the hydrophobic domains was observed for all composite membranes, though particle size and surface chemistry were seen to have varying impacts on the spacing of the ionic domains of the ionomer.
The morphology-dependent lattice stability investigation in ZnS nanostructures by high-pressure XAFS
Explore the source record for details and available documents.
Substrate controls photovoltage, photocurrent and carrier separation in nanostructured Bi 2 S 3 films
Bi 2 S 3 is a narrow bandgap semiconductor of interest for the construction of solar energy devices and can be synthesized by E-Chem/Sulfurization approach. The (photo)current from Bi 2 S 3 can be controlled by the substrate workfunction and its resistance.
Nanostructure fabrication by area selective deposition: a brief review
This review introduces area selective deposition and highlights recent contributions toward understanding and developing robust ASD processes.
Nanostructure retention to 1100 °C in soft-templated niobium tungstates using dual-carbon strategy
The temperature stability window of mesoporous niobium tungstates is improved by 500 °C using pore backfilling strategies with carbon precursors.