Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “direct synthesis”

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 847 records · Page 47
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

20th Aerospace Mechanisms Symposium

The proceedings of the 20th Aerospace Mechanisms Symposium, hosted by the NASA Lewis Research Center, Cleveland, Ohio, on May 7-9, 1986, is documented herein. During the 3 days, 23 technical papers were presented by experts from the United States and Western Europe. A panel discussion by an International group of experts on future directions In mechanisms was also presented; this discussion, however, is not documented herein. The technical topics addressed included deployable structures, electromagnetic devices, tribology, thermal/mechanical/hydraulic actuators, latching devices, positioning mechanisms, robotic manipulators, and computerized mechanisms synthesis.

Source record↗
NASA NTRS2000

Peptide nucleic acids rather than RNA may have been the first genetic molecule

Numerous problems exist with the current thinking of RNA as the first genetic material. No plausible prebiotic processes have yet been demonstrated to produce the nucleosides or nucleotides or for efficient two-way nonenzymatic replication. Peptide nucleic acid (PNA) is a promising precursor to RNA, consisting of N-(2-aminoethyl)glycine (AEG) and the adenine, uracil, guanine, and cytosine-N-acetic acids. However, PNA has not yet been demonstrated to be prebiotic. We show here that AEG is produced directly in electric discharge reactions from CH(4), N(2), NH(3), and H(2)O. Electric discharges also produce ethylenediamine, as do NH(4)CN polymerizations. AEG is produced from the robust Strecker synthesis with ethylenediamine. The NH(4)CN polymerization in the presence of glycine leads to the adenine and guanine-N(9)-acetic acids, and the cytosine and uracil-N(1)-acetic acids are produced in high yield from the reaction of cyanoacetaldehyde with hydantoic acid, rather than urea. Preliminary experiments suggest that AEG may polymerize rapidly at 100 degrees C to give the polypeptide backbone of PNA. The ease of synthesis of the components of PNA and possibility of polymerization of AEG reinforce the possibility that PNA may have been the first genetic material.

NASA Discipline Exobiology↗
DOE OSTI2020

1D to 2D Transition in Tellurium Observed by 4D Electron Microscopy

A new microwave-enhanced synthesis method for the production of tellurium nanostructures is reported here—with control over products from the 1D regime (sub-5 nm diameter nanowires), to nanoribbons, to the 2D tellurene regime—along with a new methodology for local statistical quantification of the crystallographic parameters of these materials at the nanometer scale. Using a direct electron detector and image-corrected microscope, large and robust 4D scanning transmission electron microscopy datasets for accurate structural analysis are obtained. These datasets allow the adaptation of quantitative techniques originally developed for X-ray diffraction (XRD) refinement analyses to transmission electron microscopy, enabling the first demonstration of sub-picometer accuracy lattice parameter extraction while also obtaining both the size of the coherent crystallite domains and the nanostrain, which is observed to decrease as nanowires transition to tellurene. This new local analysis is commensurate with global powder XRD results, indicating the robustness of both the new synthesis approach and new structural analysis methodology for future scalable production of 2D tellurene and characterization of nanomaterials.

2D materials↗
DOE OSTI2026

Metallic Pd–Cu Alloy Phases Drive Selective Heterogeneous Electrochemical Ketonization of 1-Butene

Electrification of 2-butanone synthesis via ketonization of 1-butene offers a viable pathway to reduce emissions associated with its production as a commodity chemical and enhance its prospects as a clean carbon-based synthetic fuel. However, the direct electrochemical ketonization of alkenes remains underexplored, with previous studies largely limited to epoxides and glycols. Herein, we report an electrochemical heterogeneous system optimized for 1-butene ketonization, converting 1-butene to 2- butanone using a bimetallic PdCu catalyst in aqueous electrolytes. The system achieves a Faradaic efficiency of 20% and a partial current density of 0.6 mA/cm 2 at 1.8 V RHE . In comparison to monometallic Pd and oxidized PdCu analogs, the PdCu catalyst doubles the ketonization Faradaic efficiency and quadruples the production rate. Postelectrolysis characterization reveals that PdCu preserves the surface metallic alloy phase under anodic polarization, which likely accounts for the enhanced ketonization activity. This work demonstrates the significance of the Pd−Cu speciation dynamics and provides a framework for designing selective electrocatalysts for alkene ketonization.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
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 OSTI2019

Utilizing TiO 2 amorphous precursors for polymorph selection: An in situ TEM study of phase formation and kinetics

Selective synthesis of metastable polymorphs requires a fundamental understanding of the complex energy landscapes in which these phases form. Recently, the development of in situ high temperature and controlled atmosphere transmission electron microscopy has enabled the direct observation of nucleation, growth, and phase transformations with near atomic resolution. In this work, we directly observe the crystallization behavior of amorphous TiO 2 thin films grown under different pulsed laser deposition conditions and quantify the mechanisms behind metastable crystalline polymorph stabilization. Films deposited at 10 mTorr chamber oxygen pressure crystallize into nanocrystalline Anatase at 325 degrees C, whereas films deposited at 2 mTorr crystallize into significantly larger needle-like grains of Brookite and Anatase at 270 degrees C. Increasing film deposition rate by a factor of 4 results in a 10x increase in the crystalline growth front velocity as well as a decrease in crystallization temperature from 270 degrees C to 225 degrees C. Engineering the amorphous precursor state through deposition conditions therefore provides routes to microstructure control and the accessibility of higher energy metastable phases.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Understanding the cold plasma synthesis of ammonia with model metal catalysts through plasma diagnostics (Final Report)

The industrial synthesis of ammonia, which amounts to over 200 million tons annually, is the most energy-intensive chemical process. Therefore, there is a critical need and increased interest in exploring less energetic routes to produce ammonia. Not only does ammonia have a direct impact on the food market, but also it has the potential as a fuel and hydrogen carrier. Recently, plasma catalysis has emerged as a promising alternative for synthesizing ammonia at mild (pressure, temperature and power) conditions. The key to this catalytic process is the synergy between the plasma and the catalyst, where the non-equilibrium plasma allows the generation of excited species, which recombine at the catalyst surface to form ammonia. However, our current understanding of this process is in its infancy. In this respect, model metals are ideal candidates for gaining a basic understanding of this reaction. Moreover, a major roadblock to rationally designing novel effective catalysts for plasma-assisted ammonia production is the need for fundamental aspects of this process. Through a comprehensive plan that integrates model metals as catalysts and world-class diagnostics, the proposed work aims to provide fundamental knowledge about the nature of reactive processes occurring during plasma-assisted catalysis and to demonstrate the selective production of ammonia, catalyzed by employing selected metals under non-thermal plasma conditions. Toward this goal, the central thrust of this proposal was to demonstrate that the synergy between plasma and rationally selected model metals will boost ammonia yields during plasma-assisted ammonia synthesis by delaying hydrogen recombination. Specifically, we aimed to (1) understand the formation and role of gas-phase active species such as NH, N 2 , N 2 + and Ha during the plasma-enhanced synthesis of ammonia through OES and FTIRAS using different reaction configurations: a) only plasma (non-packed DBD reactor) and b) packed DBD reactor with metal nanoparticles. This proposal was awarded/recommended with a run time on the PCRF facility FY20.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1990

Multiprocessor architecture: Synthesis and evaluation

Multiprocessor computed architecture evaluation for structural computations is the focus of the research effort described. Results obtained are expected to lead to more efficient use of existing architectures and to suggest designs for new, application specific, architectures. The brief descriptions given outline a number of related efforts directed toward this purpose. The difficulty is analyzing an existing architecture or in designing a new computer architecture lies in the fact that the performance of a particular architecture, within the context of a given application, is determined by a number of factors. These include, but are not limited to, the efficiency of the computation algorithm, the programming language and support environment, the quality of the program written in the programming language, the multiplicity of the processing elements, the characteristics of the individual processing elements, the interconnection network connecting processors and non-local memories, and the shared memory organization covering the spectrum from no shared memory (all local memory) to one global access memory. These performance determiners may be loosely classified as being software or hardware related. This distinction is not clear or even appropriate in many cases. The effect of the choice of algorithm is ignored by assuming that the algorithm is specified as given. Effort directed toward the removal of the effect of the programming language and program resulted in the design of a high-level parallel programming language. Two characteristics of the fundamental structure of the architecture (memory organization and interconnection network) are examined.

Standley, Hilda M.↗
DOE OSTI2020

Synthesis of luminescent core/shell α-Zn 3 P 2 /ZnS quantum dots

Metal chalcogenide nanoparticles offer vast control over their optoelectronic properties via size, shape, composition, and morphology which has led to their use across fields including optoelectronics, energy storage, and catalysis. While cadmium and lead-based nanocrystals are prevalent in applications, concerns over their toxicity have motivated researchers to explore alternate classes of nanomaterials based on environmentally benign metals such as zinc and tin. The goal of this research is to identify material systems that offer comparable performance to existing metal chalcogenide systems from abundant, recyclable, and environmentally benign materials. With band gaps that span the visible through the infrared, II–V direct band gap semiconductors such as tetragonal zinc phosphide (α-Zn 3 P 2 ) are promising candidates for optoelectronics. To date, syntheses of α-Zn 3 P 2 nanoparticles have been hindered because of the toxicity of zinc and phosphorus precursors, surface oxidation, and defect states leading to carrier trapping and low photoluminescence quantum yield. Here, we report a colloidal synthesis of quantum confined α-Zn 3 P 2 nanoparticles from common phosphorus precursor tris(trimethylsilyl)phosphine and environmentally benign zinc carboxylates. Shelling of the nanoparticles with zinc sulfide is shown as a method of preventing oxidation and improving the optical properties of the nanoparticles. These results show a route to stabilizing α-Zn 3 P 2 nanoparticles for optoelectronic device applications.

25 ENERGY STORAGE↗
DOE OSTI2023

A highly proton conductive perfluorinated covalent triazine framework via low-temperature synthesis

Proton-conducting materials are essential to the emerging hydrogen economy. Covalent triazine frameworks (CTFs) are promising proton-conducting materials at high temperatures but need more effective sites to strengthen interaction for proton carriers. However, their construction and design in a concise condition are still challenges. Herein, we show a low temperature approach to synthesize CTFs via a direct cyclotrimerization of aromatic aldehyde using ammonium iodide as facile nitrogen source. Among the CTFs, the perfluorinated CTF (CTF-TF) was successfully synthesized with much lower temperature ( ≤ 160 °C) and open-air atmosphere. Due to the additional hydrogen-bonding interaction between fluorine atoms and proton carriers (H 3 PO 4 ), the CTF-TF achieves a proton conductivity of 1.82 × 10 -1 S cm -1 at 150 °C after H 3 PO 4 loading. Moreover, the CTF-TF can be readily integrated into mixed matrix membranes, displaying high proton conduction abilities and good mechanical strength. This work provides an alternative strategy for rational design of proton conducting media.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

A potential role for RNA aminoacylation prior to its role in peptide synthesis

Coded ribosomal peptide synthesis could not have evolved unless its sequence and amino acid–specific aminoacylated tRNA substrates already existed. We therefore wondered whether aminoacylated RNAs might have served some primordial function prior to their role in protein synthesis. Here, we show that specific RNA sequences can be nonenzymatically aminoacylated and ligated to produce amino acid–bridged stem-loop RNAs. We used deep sequencing to identify RNAs that undergo highly efficient glycine aminoacylation followed by loop-closing ligation. The crystal structure of one such glycine-bridged RNA hairpin reveals a compact internally stabilized structure with the same eponymous T-loop architecture that is found in many noncoding RNAs, including the modern tRNA. We demonstrate that the T-loop-assisted amino acid bridging of RNA oligonucleotides enables the rapid template-free assembly of a chimeric version of an aminoacyl-RNA synthetase ribozyme. We suggest that the primordial assembly of amino acid–bridged chimeric ribozymes provides a direct and facile route for the covalent incorporation of amino acids into RNA. A greater functionality of covalently incorporated amino acids could contribute to enhanced ribozyme catalysis, providing a driving force for the evolution of sequence and amino acid–specific aminoacyl-RNA synthetase ribozymes in the RNA World. The synthesis of specifically aminoacylated RNAs, an unlikely prospect for nonenzymatic reactions but a likely one for ribozymes, could have set the stage for the subsequent evolution of coded protein synthesis.

Science & Technology - Other Topics↗
DOE OSTI2024

Creating yellow seed Camelina sativa with enhanced oil accumulation by CRISPR ‐mediated disruption of Transparent Testa 8

Summary Camelina ( Camelina sativa L.), a hexaploid member of the Brassicaceae family, is an emerging oilseed crop being developed to meet the increasing demand for plant oils as biofuel feedstocks. In other Brassicas, high oil content can be associated with a yellow seed phenotype, which is unknown for camelina. We sought to create yellow seed camelina using CRISPR/Cas9 technology to disrupt its Transparent Testa 8 (TT8) transcription factor genes and to evaluate the resulting seed phenotype. We identified three TT8 genes, one in each of the three camelina subgenomes, and obtained independent CsTT8 lines containing frameshift edits. Disruption of TT8 caused seed coat colour to change from brown to yellow reflecting their reduced flavonoid accumulation of up to 44%, and the loss of a well‐organized seed coat mucilage layer. Transcriptomic analysis of CsTT8 ‐edited seeds revealed significantly increased expression of the lipid‐related transcription factors LEC1 , LEC2 , FUS3 , and WRI1 and their downstream fatty acid synthesis‐related targets. These changes caused metabolic remodelling with increased fatty acid synthesis rates and corresponding increases in total fatty acid (TFA) accumulation from 32.4% to as high as 38.0% of seed weight, and TAG yield by more than 21% without significant changes in starch or protein levels compared to parental line. These data highlight the effectiveness of CRISPR in creating novel enhanced‐oil germplasm in camelina. The resulting lines may directly contribute to future net‐zero carbon energy production or be combined with other traits to produce desired lipid‐derived bioproducts at high yields.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Biocatalytic Synthesis of α-Amino Esters via Nitrene C–H Insertion

α-Amino esters are precursors to noncanonical amino acids used in developing small-molecule therapeutics, biologics, and tools in chemical biology. α-C–H amination of abundant and inexpensive carboxylic acid esters through nitrene transfer presents a direct approach to α-amino esters. Methods for nitrene-mediated amination of the protic α-C–H bonds in carboxylic acid esters, however, are underdeveloped. This gap arises because hydrogen atom abstraction (HAA) of protic C–H bonds by electrophilic metal-nitrenoids is slow: metal-nitrenoids preferentially react with polarity-matched, hydridic C–H bonds, even when weaker protic C–H bonds are present. This study describes the discovery and evolution of highly stable protoglobin nitrene transferases that catalyze the enantioselective intermolecular amination of the α-C–H bonds in carboxylic acid esters. We developed a high-throughput assay to evaluate the activity and enantioselectivity of mutant enzymes together with their sequences using the Every Variant Sequencing (evSeq) method. Furthermore, the assay enabled the identification of enantiodivergent enzymes that function at ambient conditions in Escherichia coli whole cells and whose activities can be enhanced by directed evolution for the amination of a range of substrates.

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

Plasma-Catalyst Reactivity Control of Surface Nitrogen Species through Plasma-Temperature-Programmed Hydrogenation to Ammonia

Nonthermal plasma activation of N 2 can facilitate nitrogen adsorption on metal catalysts at low bulk temperatures and atmospheric pressure. Here, we apply a plasma-assisted temperature-programmed reaction (plasma-TPRxn) for ammonia (NH 3 ) synthesis using sequential exposure of a silica-supported metal catalyst to N 2 plasma followed by thermal hydrogen treatment while ramping the temperature to decouple the plasma activation of N 2 from surface catalyzed hydrogenation steps. This approach eliminates the effects from bulk plasma phase reactions, thereby allowing for direct interrogation of plasma activated nitrogen on the active metal surfaces. We confirm previously reported spectroscopic observations that show plasma-generated surface nitrogen can be converted to NH 3 through surface catalyzed pathways. Further, we demonstrate that the ammonia desorption peak temperature is sensitive to metal, with Pt desorbing NH 3 at the lowest temperature. Unsteady state microkinetic models of desorption kinetics as a function of initial N coverage and metal recover observed trends in NH 3 desorption temperatures and confirm that observed results reflect hydrogenation of plasma-induced N accommodation at each surface. In total, we show that the hydrogenation ability of the catalyst after plasma activation of N 2 is responsible for the reactivity trends observed in plasma-assisted NH 3 synthesis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Mobilizing Vacuolar Sugar Increases Vegetative Triacylglycerol Accumulation

Photosynthetically derived sugars provide carbon skeletons for metabolism and carbon signals that favor anabolism. The amount of sugar available for fatty acid (FA) and triacylglycerol (TAG) synthesis depends on sugar compartmentation, transport, and demands from competing pathways. We are exploring the influence of sugar partitioning between the vacuole and cytoplasm on FA synthesis in Arabidopsis by building on our previous finding that reduced leaf sugar export in the sucrose-proton symporter2 (suc2) mutant, in combination with impaired starch synthesis in the ADP-glucose pyrophosphorylase (adg1) mutant, accumulates higher sugar levels and increased total FA and TAG compared to the wild type parent. Here we sought to relocalize sugar from the vacuole to the cytoplasm to drive additional FA/TAG synthesis and growth. Arabidopsis suc2 adg1 was therefore crossed with tonoplast monosaccharide transporter mutants tmt1 and tmt2 and overexpression of the sucrose/proton cotransporter SUC4 in which tmt1 tmt2 impairs sugar transport to the vacuole from the cytoplasm and SUC4 overexpression enhances sugar transport in the reverse direction from the vacuole to the cytoplasm. A resulting homozygous suc2 adg1 tmt1 tmt2 SUC4 line was used to test the hypothesis that increased intracellular carbon supply in the form of sugars would increase both FA and TAG accumulation. The data shows that relative to suc2 adg1, suc2 adg1 tmt1 tmt2 SUC4 significantly increases leaf total FA content by 1.29-fold to 10.9% of dry weight and TAG by 2.4-fold to 2.88%, supporting the hypothesis that mobilizing vacuolar sugar is a valid strategy for increasing vegetative oil accumulation.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

An Emerging Trend in the Synthesis of Iron Titanate Photocatalyst Toward Water Splitting

Hydrogen gas is a prominent focus in pursuing renewable and clean alternative energy sources. The quest for maximizing hydrogen production yield involves the exploration of an ideal photocatalyst and the development of a simple, cost-effective technique for its generation. Iron titanate has garnered attention in this context due to its photocatalytic properties, affordability, and non-toxic nature. Over the years, different synthesis routes, different morphologies, and some modifications of iron titanate have been carried out to improve its photocatalytic performance by enhancing light absorption in the visible region, boosting charge carrier transfer, and decreasing recombination of electrons and holes. The use of iron titanate photocatalyst for hydrogen evolution reaction has seen an upward trend in recent times, and based on available findings, more can be done to improve the performance. This review paper provides a comprehensive overview of the fundamental principles of photocatalysis for hydrogen generation, encompassing the synthesis, morphology, and application of iron titanate-based photocatalysts. The discussion delves into the limitations of current methodologies and present and future perspectives for advancing iron titanate photocatalysts. By addressing these limitations and contemplating future directions, the aim is to enhance the properties of materials fabricated for photocatalytic water splitting.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Rational Enzyme Design for Controlled Functionalization of Acetylated Xylan for Cell-Free Polymer Biosynthesis

Xylan O-acetyltransferase 1 (XOAT1) is involved in O-acetylating the backbone of hemicellulose xylan. Recent structural analysis of XOAT1 showed two unequal lobes forming a cleft that is predicted to accommodate and position xylan acceptors into proximity with the catalytic triad. Here, we used docking and molecular dynamics simulations to investigate the optimal orientation of xylan in the binding cleft of XOAT1 and identify putative key residues (Gln445 and Arg444 on Minor lobe & Asn312, Met311 and Asp403 on Major lobe) involved in substrate interactions. Site-directed mutagenesis coupled with biochemical analyses revealed the major lobe of XOAT1 is important for xylan binding. Mutation of single key residues yielded XOAT1 variants with various enzymatic efficiencies that are applicable to one-pot synthesis of xylan polymers with different degrees of O-acetylation. Taken together, our results demonstrate the effectiveness of computational modeling in guiding enzyme engineering aimed at modulating xylan and redesigning plant cell walls.

93 SC - Biological and Environmental Research (BER↗