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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.

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43 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Report on Current Assessment of Fabrication Routes to Large-Scale UN Production

Uranium mononitride has been proposed for nuclear fuels, given its favorable uranium atom density and thermal conductivity. Current synthesis routes are either cost prohibitive or leave behind unwanted carbon or oxygen contaminants. Here, a route known as oxidative ammonolysis is explored to convert uranium tetrafluoride to uranium dinitride. Reaction products have been examined and phases determined. The study here shows the possibility to convert uranium fluoride phases to uranium nitride phases.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

A New Method to Overcome Carboxyamide Formation During AFEX Pretreatment of Lignocellulosic Biomass

Lignin-carbohydrate complexes (LCCs) in the plant cell wall are responsible for providing resistance against biomass-degrading enzymes produced by microorganisms. Four major types of lignin-carbohydrate bonds are reported in the literature, namely, benzyl ethers, benzyl esters, phenyl glycosides, and acetyl ester linkages. Ester’s linkages in the plant cell wall are labile to alkaline pretreatments, such as ammonia fiber expansion (AFEX), which uses liquid or gaseous ammonia to cleave those linkages in the plant cell wall and reduce biomass recalcitrance. Two competing reactions, notably hydrolysis and ammonolysis, take place during AFEX pretreatment process, producing different aliphatic and aromatic acids, as well as their amide counterparts. AFEX pretreated grasses and agricultural residues are known to increase conversion of biomass to sugars by four- to five-fold when subjected to commercial enzyme hydrolysis, yielding a sustainable feedstock for producing biofuels, biomaterials, and animal feed. Animal feed trials on dairy cows have demonstrated a 27% increase in milk production when compared to a control feedstock. However, the presence of carboxamides in feedstocks could promote neurotoxicity in animals if consumed beyond a certain concentration. Thus, there is the need to overcome regulatory hurdles associated with commercializing AFEX pretreated biomass as animal feed in the United States. This manuscript demonstrates a modified pretreatment for increasing the digestibility of industrial byproducts such as Brewer’s spent grains (BSG) and high-fiber meal (HFM) produced from BSG and dry distillers grains with soluble (DDGS), while avoiding the production of carboxamides. The three industrial byproducts were first treated with calculated amounts of alkali such as NaOH, Ca(OH) 2 , or KOH followed by AFEX pretreatment. We found that 4% alkali was able to de-esterify BSG and DDGS more efficiently than using 2% alkali at both 10 and 20% solids loading. AFEX pretreatment of de-esterified BSG, HFM, and DDGS produced twofold higher glucan conversion than respective untreated biomass. This new discovery can help overcome potential regulatory issues associated with the presence of carboxamides in ammonia-pretreated animal feeds and is expected to benefit several farmers around the world.

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

Effects of Extractive Ammonia Pretreatment on the Ultrastructure and Glycan Composition of Corn Stover

Lignocellulosic biomass is highly recalcitrant and requires a pretreatment step to improve the enzyme accessibility and fermentable sugar yields during enzymatic hydrolysis. Our previous studies demonstrated the rearrangement of the hydrogen bond network within CIII, makes it “amorphous-like” and facilitates easier glucan chain extraction by enzyme. Also, these changes increase the number of solvent-exposed glucan chain hydrogen bonds with water ~50% lowering the surface-bound cellulase by 60–70%. Also, major chemical modifications to lignin occur via ammonolysis of ester-linked ferulate and coumarate linkage. These apparent ultrastructural changes help the enhancement of cellulase activity resulting in higher production of fermentable sugars during enzyme hydrolysis of EA pretreated corn stover relative to Ammonia Fiber Expansion (AFEX) pretreatment. To understand ultra-structural modifications that occur during EA pretreatment, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were used to examine untreated and EA-pretreated corn stover in an effort to visualize changes in the biomass resulting from the pretreatment. In addition, Immunofluorescence Microscopy was applied to both untreated and pretreated plant cell walls using glycan-directed monoclonal antibodies to reveal possible changes in the spatial distributions of wall glycan epitopes resulting from EA pretreatment. This evaluation was complemented with glycome profiling to determine the glycan epitope compositions of EA-pretreated cell walls relative to untreated and AFEX pretreated corn stover, where lignin and carbohydrates are not extracted. Distinct differences could be observed in the case of xyloglucan, unsubstituted and substituted pectin- and pectic-arabinogalactan-epitope levels in the plant cell wall after EA pretreatment compared with untreated and AFEX-pretreated walls. Liquid ammonia induced de-lignification of cell wall has helped to clearly identify the glucans that are intact after pretreatment. These studies support some of our hypothesis that liquid ammonia cleaves lignin–carbohydrate ester linkages, partially solubilizing lignin and its associated carbohydrates. Specifically, the imaging studies clearly show that some of the cell wall components are extracted as a separate liquid stream during the EA process, thereby creating porous, interconnected tunnel-like networks in the plant cell walls thereby providing better access of carbohydrate polymers to enzymes and thereby increasing the sugar yield from the EA-pretreated biomass.

09 BIOMASS FUELS↗
NASA NTRS1994

Synthesis Of A Precursor Of Silicon Nitride

Promising route toward production of highly pure, finely divided, easily sinterable silicon nitride (Si3N4) involves thermal decomposition of silicon diimide {Si(NH)2} prepared by ammonolysis of Si(SCN)4 in CH3CN and purified by complete extraction of byproduct NH4SCN by use of ammonia at temperature and pressure above critical point.

Philipp, Warren H.↗
DOE OSTI2012

Double perovskite Sr{sub 2}FeMoO{sub 6-x}N{sub x} (x=0.3, 1.0) oxynitrides with anionic ordering

Two new oxynitride double perovskites of composition Sr{sub 2}FeMoO{sub 6-x}N{sub x} (x=0.3, 1.0) have been synthesized by annealing precursor powders obtained by citrate techniques in flowing ammonia at 750 Degree-Sign C and 650 Degree-Sign C, respectively. The polycrystalline samples have been characterized by chemical analysis, x-ray and neutron diffraction (NPD), Moessbauer spectroscopy and magnetic measurements. They exhibit a tetragonal structure with a=5.5959(1) A, c=7.9024(2) A, V=247.46(2) A{sup 3} for Sr{sub 2}FeMoO{sub 5.7}N{sub 0.3}; and a=5.6202(2) A, c=7.9102(4) A, V=249.85(2) A{sup 3} for Sr{sub 2}FeMoO{sub 5}N; space group I4/m, Z=2. The nitridation process seems to extraordinarily improve the long-range Fe/Mo ordering, achieving 95% at moderate temperatures of 750 Degree-Sign C. The analysis of high resolution NPD data, based on the contrast existing between the scattering lengths of O and N, shows that both atoms are located at (O,N)2 anion substructure corresponding to the basal ab plane of the perovskite structure, whereas the O1 site is fully occupied by oxygen atoms. The evolution of the Left-Pointing-Angle-Bracket Fe-O Right-Pointing-Angle-Bracket and Left-Pointing-Angle-Bracket Mo-O Right-Pointing-Angle-Bracket distances suggests a shift towards a configuration close to Fe{sup 4+}(3d{sup 4}, S=2):Mo{sup 5+}(4d{sup 1}, S=1/2). The magnetic susceptibility shows a ferrimagnetic transition with a reduced saturation magnetization compared to Sr{sub 2}FeMoO{sub 6}, due to the different nature of the magnetic double exchange interactions through Fe-N-Mo-N-Fe paths in contrast to the stronger Fe-O-Mo-O-Fe interactions. Also, the effect observed by low-temperature NPD seems to reduce the ordered Fe moments and enhance the Mo moments, in agreement with the evolution of the oxidation states, thus decreasing the saturation magnetization. - Graphical Abstract: We have synthesized and studied the new oxinitride double perovskites Sr{sub 2}FeMoO{sub 6-x}N{sub x}. They present anionic ordering between O and N. The nitridation process improves the long-range Fe/Mo ordering. They show a ferrimagnetic transition with a reduced saturation magnetization compared to Sr{sub 2}FeMoO{sub 6}, due to the different nature of the double exchange interactions through Fe-N-Mo-N-Fe in contrast to Fe-O-Mo-O-Fe. We suggest a shift towards a configuration Fe{sup 4+}(3d{sup 4}, S=2):Mo{sup 5+}(4d{sup 1}, S=1/2). Highlights: Black-Right-Pointing-Pointer Synthesis and study of the new oxinitride double perovskites Sr{sub 2}FeMoO{sub 6-x}N{sub x} (x=0.3, 1.0). Black-Right-Pointing-Pointer Compounds present anionic ordering between O and N. Black-Right-Pointing-Pointer Nitridation process extraordinarily improves the long-range Fe/Mo ordering. Black-Right-Pointing-Pointer We suggest a shift towards a configuration Fe{sup 4+}(3d{sup 4}, S=2):Mo{sup 5+}(4d{sup 1}, S=1/2).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗