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At least 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Optimal Design of Ozone Bleaching Parameters to Approach Cellulose Nanofibers Extraction from Sugarcane Bagasse Fibers

Cellulose nanofibers (CNFs) were isolated from sugarcane bagasse (SCB) through the combination of bio-refinery, sulfur-free, and totally chlorine free (TCF) chemo-mechanical pretreatments, with a focus on the optimal design of ozone bleaching parameters based on a response surface methodology (RSM). For this purpose, the most effective parameters in ozone bleaching (temperature, time, and pulp consistency) were set between 40 and 85 °C, 60 and 360 min, and 1–5 wt%, respectively. High-performance liquid chromatography (HPLC), Fourier transform infrared spectroscopy (FTIR), Kappa number, and scanning electron microscopy (SEM) were used to chemically and morphologically characterize the SCB fibers. The size distribution and morphology of CNFs were also evaluated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). HPLC analysis revealed that percentage of cellulose increased from 41.5 to 91.39% after chemical pretreatments. FTIR and Kappa number analyses also confirmed the successful isolation of cellulose fibers from the SCB fibers after chemical pretreatments. Furthermore, DLS results showed that the hydrodynamic diameter of the isolated cellulose fibers reduced to 268 nm by dint of ultrasonication. Additionally, TEM images confirmed the isolation of CNFs: the average diameter of cellulose fibers decreased to about 28 nm after mechanical steps and the yield of fibrillation was found to be around 99%. According to the obtained results, the applied chemo-mechanical treatment appears to be promising for green and facile isolation of CNFs.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Electrospun ZnO Nanoparticles Doped Core–Sheath Nanofibers: Characterization and Antimicrobial Properties

Coaxial electrospinning technique was used to fabricate the core–sheath composite nanofibers of ZnO nanoparticle (Nps) (10%, 20% w/w) doped polymethyl methacrylate (PMMA) (as sheath) and polyvinyl alcohol (PVA) (as core). Fourier transform infrared (FT-IR) spectra were confirmed the weak forces arise between ZnO Nps, PMMA and PVA matrixes. The hexagonal (wurtzite) structure of ZnO Nps with ~ 30.8 nm of diameter was confirmed from the X-ray diffraction pattern. The morphology and microstructure of core–sheath composite nanofibers were confirmed from the scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is clearly seen from the TEM images that the PMMA encapsulate the PVA core. Core–sheath composite nanofibers were assessed against Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) bacteria through quantitative, disk diffusion and viable cell count methods. It was found that ZnO Nps doped core–sheath nanofibers were effectively inhibit the growth of gram positive bacteria, B. subtilis.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Intercalation of Nanopolyaniline with Nanobentonite and Manganese Oxide Nanoparticles as a Novel Nanocomposite to Remediate Cobalt/Zinc and Their Radioactive Nuclides {sup 60}Co/{sup 65}Zn

A novel nanocomposite based on the combination of nanobentonite with nanopolyaniline and nanomanganese oxide (N-Bent–NPANI–NMn{sub 3}O{sub 4}) was synthesized and investigated to extract Co/Zn ions from water using batch technique and {sup 60}Co/{sup 65}Zn radionuclides from radioactive wastewater using column techniques. Characterization was established by High resolution-transmission electron microscopy (HR-TEM), Scanning electron microscope, X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and Fourier transform infrared spectrophotometer. The image of HR-TEM indicated that the produced nanocomposite was ranged from 59.07 to 83.38 nm. Solution pH, time of reaction, amount of solid and metal concentration, all of these parameters were inspected and optimized as fundamental factors during the extraction process. The obtained results implied that the ideal conditions for extraction were pH 6 and 7, reaction time 10 and 20 min, for Co and Zn ions, respectively. The highest removal capacities were found 255.28 and 202.22 mg g{sup −1} for Co and Zn, respectively by using 5 mg nanocomposite. Excellent recoveries were obtained as 94.0–94.5% and 92.0–93.0% for removal of Co–{sup 60}Co and of Zn–{sup 65}Zn ions, respectively from the examined samples. Graphical Abstract: .

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Polymer Based Palladium Nanocatalyst for the Degradation of Nitrate and Congo Red

In this study, the Pd catalyst based on chitosan-tannin (CT) framework as support was prepared and characterized. The CT support and Pd catalyst were characterized by attenuated total reflection (ATR) spectroscopy and Raman spectroscopy, Scanning electron microscopy-energy dispersive X-ray analyzer (SEM–EDX) and transmission electron microscopy (TEM) and X-ray diffractometry (XRD). Attenuated total reflection (ATR) spectra revealed the coordination of Pd via hydroxyl and amino functional groups. Raman spectral analysis was carried out to give information about the structural defect of the catalyst compared to CT support. The SEM–EDX results revealed regular surface morphology and presence of Pd in the catalyst as compared to CT support. TEM analysis revealed that the deposition of Pd on organic support with a spherical shape possessing size in the range of 6.01 nm–20.7 nm (average particle size = 12.65 ± 3.14 nm). The XRD results revealed the amorphous nature of the catalyst compared to CT support. TGA analysis revealed that the catalyst is highly thermally-stable compared to CT support. The catalytic activity of Pd catalyst was investigated for the reduction of nitrate and Congo red in the presence and absence of H{sub 2}. The catalytic activities exhibited 71.11% and 23% removal of nitrate and Congo red in 20 and 60 min, respectively. Thus, results suggested that Pd catalyst has a potential of catalytic activity toward reduction of nitrate and Congo red in presence H{sub 2}.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Electrochemical and Magnetic Properties of Electrospun SrTi{sub 1−x}Fe{sub x}O{sub 3} (x = 0, 0.05 and 0.10) Nanofibers for Anodes of Li-Ion Batteries

SrTi{sub 1−x}Fe{sub x}O{sub 3} (x = 0, 0.05 and 0.1) nanofibers (NFs) were fabricated by electrospinning technique. As prepared products were calcined at 800 {sup ∘} C in argon atmosphere for 3 h to obtain a perovskite phase. The crystal structure and morphology of samples were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Electrochemical and magnetic properties of calcined NFs were studied using a potentiostat/galvanostat electrochemical cell system and vibrating sample magnetometer (VSM), respectively. XRD results showed the cubic perovskite structure of calcined samples with the diameter estimated by TEM in the range of 137.4–141.3 nm SEM micrographs revealed the linkage of crystalline grains in NFs of porous and rough surfaces. Electrochemical properties performed on coin-cell-type Li-ion batteries (LIBs) with calcined SrTi{sub 1−x}Fe{sub x}O{sub 3} (x = 0.05 and 0.10) NF-based anodes showed a significant increase of the specific capacity from 305 to 431 mAh/g for the first cycle with the reversible values of 100 and 130 mAh/g, respectively. VSM measurements at room temperature (RT) indicated that calcined SrTiO{sub 3} NFs exhibited paramagnetic (PM) behavior, while calcined SrTi{sub 1−x}Fe{sub x}O{sub 3} NFs displayed ferromagnetic (FM) behavior at RT with the increase of unsaturated magnetization at 10 kOe from 0.46 to 0.82 emu/g for samples with x = 0.05 and 0.10, respectively. The observed FM behavior in calcined SrTi{sub 1−x}Fe{sub x}O{sub 3} (x = 0.05 and 0.1) NFs was suggested to originate from the face center exchange (FCE) mechanism owing to Fe{sup 3+} –Vo–Fe{sup 3+} couplings.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

The Effect of Ba Doping on the Structural, Optical, Magnetic, and Dielectric Properties of BiFeO{sub 3} Nanoparticles

Nanoparticles (Nps) of Ba (0, 1 to 5 at.%)-doped BiFeO{sub 3} were synthesized by a sol-gel route at 100 °C using tartaric acid as a chelating agent. The obtained results were studied by using XRD, SEM with EDAX, TEM, UV-vis diffusion reflectance spectra, VSM, and impedance analyzer. EDAX spectra confirmed the presence of Bi, Ba, and Fe in the samples. X-ray diffraction studies showed that BiFeO{sub 3} and Bi{sub 1−x}Ba{sub x}FeO{sub 3} samples exhibited the expected rhombohedral perovskite structure up to a Ba concentration of 3%, whereas 4 and 5% of Ba concentration exhibited the tetragonal phase. TEM studies indicate the particle sizes in the range of 08–28 nm. Reflectance spectra measurements showed a decrease in band gap with increasing Ba concentration. Magnetic properties indicated that the undoped BiFeO{sub 3} and Ba-doped BiFeO{sub 3} samples were ferromagnetic at room temperature. The dielectric constant (ε{sup ′}) and loss (ε{sup ″}) show large dispersion behavior. The dielectric constant increases with an increase of dopant concentration, but a very high value of the dielectric constant was noticed for x = 0.05.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Tailoring the Structural, Optical and Magnetic Properties of NiFe{sub 2}O{sub 4} by Varying Annealing Temperature

Magnetic nanocrystalline NiFe{sub 2}O{sub 4} nanoparticles of size ranging between 13 and 19 nm were synthesized by the hydrothermal method using polyethylene glycol (PEG) as surfactant. The role of annealing on phase, crystallite size, and morphology was determined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Energy-dispersive X-ray spectroscopy (EDX) was used for qualitative analysis. X-ray diffraction confirmed the single phase of as-obtained particles. TEM revealed a spherical morphology having an average particle size of 13.73 nm at 523 K and rises to 14.89, 16.42, and 21.14 nm at 623, 723, and 823 K respectively, which is approximately the same as the crystallite size determined from XRD. EDX results confirmed that elemental ratios were in stoichiometry. Fourier transform infrared (FTIR) spectral analysis demonstrates the formation of M-O bond in NiFe{sub 2}O{sub 4} nanoparticles. The optical spectra obtained from UV-visible spectroscopy revealed that nanoparticles have direct allowed energy band gap of 2.34, 2.47, 2.70, and 2.20 eV at 523, 623, 723, and 823 K respectively. A vibrating sample magnetometer (VSM) was used at room temperature for magnetic measurements which further showed ferromagnetic behavior of as-synthesized material. In addition, it was found that saturation magnetization increases with an increase of annealing temperature while coercivity decreases with temperature.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Synthesis and Characterization of Er-Doped Nano ZnO Samples

Pure and erbium-doped ZnO nanoparticles (Zn{sub 1−x}Er{sub x}O), (0.00 ≤ x ≤ 0.10), were synthesized by wet chemical co-precipitation method. The structural, optical, and magnetic properties of the prepared samples were investigated using x-ray powder diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV), Fourier transform infrared spectroscopy (FTIR), M-H magnetic hysteresis, and electron paramagnetic resonance (EPR). XRD studies exhibit the presence of a single ZnO wurtzite hexagonal crystal structure for 0.00 ≤ x ≤ 0.06. A secondary phase of Er{sub 2}O{sub 3} appears for x > 0.06. This means that the solubility limit for doping Zn{sup 2+} ions by Er{sup 3+} ions is about x = 0.06 under our preparations condition. The lattice parameter a is not affected by the Erbium doping. On the other hand, the lattice parameter c and the unit cell volume V increase with the increase of x up to x = 0.06. This is attributed to the larger ionic size of Er{sup 3+} ions (0.88 Å) compared to Zn{sup 2+} ions (0.74 Å). Both c and V decrease for x > 0.06. TEM micrographs indicate that the shape and the size of the ZnO nanoparticles are modified by changing the doping level of Er. The UV measurements point out that band gap energy E{sub g} decreases with the increase of x up to x = 0.06. Then, it increases for both x = 0.08 and 0.10. FTIR spectra confirm the presence of O–H and Zn–O stretching modes at 3451.963 and 428.901 cm{sup − 1}, respectively, in pure and doped ZnO samples. The Zn–O stretching mode shifts toward a lower wavenumber for x = 0.06 and toward a higher wavenumber for x = 0.10. M-H hysteresis analysis, at room temperature, reveals that the pure ZnO has a ferromagnetic signal combined with diamagnetic and paramagnetic contributions. This ferromagnetism is reduced for the doped samples up to x = 0.02, and an antiferromagnetic alignment appears for 0.04 ≤ x ≤ 0.10. The saturation magnetization (M{sub s}), the coercivity (H{sub c}), the retentivity (M{sub r}), the anisotropy constant (K{sub a}), and the magnetic moment (μ{sub m}) were estimated and discussed in terms of erbium doping for the different samples. EPR spectra for Zn{sub 1−x}Er{sub x}O were measured at room temperature in order to study the effect of Er substitution on the g value, resonance field (H{sub r}), peak to peak line width (ΔH{sub pp}) and spin–spin relaxation time constant (T{sub 2}).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Synthesis, Spectroscopy, and Magnetic Characterizations of PVP-Assisted Nanoscale Particle

Inverse spinel ferrite of nonmagnetic metal-doped ferro-ferric oxide was synthesized by co-precipitation technique, and its characterizations have been performed by XRD, FTIR, TEM, EDX, VSM, and EPR. XRD figures show the prepared samples in their cubic phase and that their crystallite faces vary from 5.57 to 18.47 nm. FTIR spectra of the as-synthesized samples were performed in the range of 400 and 4000 cm{sup −1} and annealed at 600 {sup ∘}C. The TEM revealed that the syllable construction of the nanoscale particles was agglomerated in their crystalline sample. From VSM study, the sample obtained has a doublet pattern, and ferromagnetic performance was observed from the samples. From EPR spectra, the line shape and the g values obtained for the samples conformed to superparamagnetic resonance due to Mg{sup + 2} ions with a stoichiometric composition. These typical magnetic hypnotic specifications are used for various sensing applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Magnetic and Structural Properties of Novel Neodymium-Tin Spinel Ferrite Nanoparticles

Novel spinel neodymium-tin ferrite nanoparticles (Nd{sub 0.5}Sn{sub 0.5}Fe{sub 2}O{sub 4}) have been synthesized by the coprecipitation method; x-ray diffraction (XRD), transmission electron microscopy (TEM), and superconducting quantum interference device magnetometer (SQUID) techniques were used to characterize the crystal structure, morphology, and magnetic properties. The spinel structure of a single phase is obtained according to XRD results. From TEM characterization results, we obtained a spherical morphology with an average of 13 nm. Magnetic measurement indicates that the nanoparticles have a superparamagnetic phase with a corresponding blocking temperature (T{sub B}) of about 360 K. These new nanomaterials can potentially be used in nanoelectronic devices, magnetic sensors, and hyperthermia application.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Physical Properties of Mn{sub 2}O{sub 3} Nanoparticles Synthesized by Co-precipitation Method at Different pH Values

Mn{sub 2}O{sub 3} nanoparticles were synthesized at different pH values ranging from 10 to 13 by co-precipitation technique. The characterization of all samples were completed by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), ultraviolet-absorption spectroscopy (UV), Raman spectroscopy, and M–H loop measurements. The XRD spectra show that the structure of Mn{sub 2}O{sub 3} is cubic, and the lattice parameter a decreases as pH increases. Crystalline size, determined from TEM and XRD analyses, decreases as pH increases. TGA curves show that a mass loss is significantly affected as pH increases, indicating the decomposition of organic species besides the oxidation of Mn{sub 2}O{sub 3} to Mn{sub 3}O{sub 4}. FTIR spectra indicate that the absorption peaks at 593.73 and 519.09 cm{sup − 11} referred to the stretching vibration of Mn–O and Mn–O–Mn bonds during the synthesis of Mn{sub 2}O{sub 3} nanoparticles. UV-visible spectroscopy is measured in the range 250–800 nm and showed a deviation to the lower wavelength in addition to an increase in the band-gap energy (E{sub g}) values from 1.012 to 1.370 eV is obtained. Raman spectra shows a slight deviation to the left which is conversely proportional to the crystalline size. M–H loops for the prepared samples were measured and the results of retentivity (M{sub s}) and coercivity (H{sub c}) were discussed.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Enhanced Magneto-optical and Antibacterial Studies of Bi{sub 1−x}Mg{sub x}FeO{sub 3} (0.0 ≤ x ≤ 0.15)) Nanoparticles

Mg-doped BiFeO{sub 3} (Bi{sub 1−x}Mg{sub x}FeO{sub 3} (0.00 ≤ x ≤ 0.15)) nanoparticles (NPs) have been successfully prepared by simple solution combustion method using urea as fuel. The obtained product was sintered at 550 °C for 2 h to get pure-phase formation. The as-prepared samples were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscope (TEM), ultraviolet–visible (UV-Vis) absorption, photoluminescence (PL) spectra, and vibrating sample magnetometer (VSM) analysis. Powder XRD study revealed that all products exhibit rhombohedral structure with pure-phase formation. The average crystallite size of the samples decreased from 56.25 to 46.15 nm with increasing the concentration of Mg (x = 0.00, 0.05, 0.10, and 0.15). Surface morphology of the samples were analyzed by FE-SEM and TEM micrograph techniques, and the grain distribution was not quite homogeneous and observed agglomeration of the particles, which is mainly due to the magnetic interaction among them. EDX analysis confirmed the presence of Bi, Fe, O, and Mg elements without any form of impurity peak in all products. PL spectra shows a high intense peak at 464 nm, which is attributed to blue emission. The saturation magnetization is enhanced with increasing Mg doping level at RT. Antibacterial activity of Bi{sub 1−x}Mg{sub x}FeO{sub 3} NPs was found to be enhanced with increase in Mg doping concentration as it causes a reduction in the grain size of the samples.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Influence of Ce{sup 3+} Ion Doping on Structural and Magnetic Properties of Magnesium Nanoferrite

Pure and rare earth ion Ce{sup 3+}-doped magnesium nanoferrite magnetic particles, i.e., MgFe{sub 2}O{sub 4} and MgCe{sub x}Fe{sub 2−x}O{sub 4} (x = 0.0, 0.025, 0.05, 0.075, and 0.1) were successfully fabricated using sol-gel technique, and qualitative studies were carried out using X-ray diffractometer (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), high-resolution field-emission scanning electron microscopy (HRFESEM) equipped with energy-dispersive spectroscopy (EDS), vibrating sample magnetometer (VSM), and electron paramagnetic resonance (EPR) techniques. X-ray diffraction analysis confirmed the crystalline phase of the synthesized samples with no extra phase. The crystallite size obtained from W-H plots follow the same trend as calculated using Scherrer method, and the strain decreases with increasing Ce{sup 3+} ion concentration indicating a lesser number of deformities. FTIR spectra revealed the shifting of lower-frequency band to the higher side with the larger radii Ce{sup 3+} ions. HRFESEM images reveal the reduction in stress on doping. No additional impurities are observed in synthesized samples as is confirmed by EDS analysis. The average particle size obtained by TEM are in agreement with XRD analysis. EPR studies showed an increase in g value and line width with doping. Magnetic measurements carried out at room temperature reveals the value of magnetization initially decreases up to x = 0.05 and afterwards increases with the addition of Ce{sup 3+} ions. These properties reveal superparamagnetic nature of cerium-doped magnesium nanoparticles and can be suitable for catalyst and humidity sensors.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Structural, Morphological, Raman, and Mössbauer Studies on (La{sub 0.8}Ca{sub 0.2}){sub 1−x}Bi{sub x}FeO{sub 3} (x = 0.0, 0.1, and 0.2) Compounds

(La{sub 0.8}Ca{sub 0.2}){sub 1−x}Bi{sub x}FeO{sub 3} (x = 0.0, 0.1, and 0.2) compounds were prepared by the sol-gel method, using the citric acid route. Structural and microstructural characteristics of the samples were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. Mössbauer spectroscopy was also used for magnetic characterization and structural confirmation of X-ray data. Refinement of XRD patterns indicated that the compounds crystallize in an orthorhombic structure, Pnma space group. The SEM measurements showed that the morphology of the samples is characterized by the existence of large agglomerates, while TEM confirmed the fine particle size. Raman spectra revealed that, when increasing temperature, the level of oxygen species adsorbed at the surface of the particles increases progressively. Room temperature Mössbauer spectroscopy data revealed the existence of two octahedral magnetic sites in the structure of the compounds, which is compatible with XRD data, and a small percentage of a paramagnetic phase in the samples, which increases with Bi-content.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Effect of Synthesis Temperature on Structural, Optical, and Magnetic Properties of ZnO Nanoparticles Synthesized by Combustion Method

ZnO nanoparticles at different temperatures were synthesized by using the combustion method. The effect of synthesis temperature on the properties of the nanoparticles was studied by using XRD, FESEM, EDS, TEM, photoluminescence (PL), Raman, diffuse reflectance spectra (DRS), and VSM characterization techniques. The XRD results reveal that the grown nanoparticles have a hexagonal wurtzite structure without any impurities and agreed with EDS results. FESEM and TEM micrographs show that the ZnO nanoparticles possess a spherical shape with agglomeration free, and the size increases with increase of synthesis temperature. From DRS studies, it was noticed that the band gap decreases with increase of synthesis temperature. In PL studies, blue peak at 465 nm may be due to defect-related transitions. A sharp intense peak in Raman spectra at 485 cm{sup −1} represents E{sub 2}H mode is a characteristic of a hexagonal wurtzite structure. The magnetic studies show that the magnetization decreases from 0.0172 to 0.0042 emu/g as the synthesis temperature increases from 400 to 550 °C. ZnO synthesized at 500 °C has a large squareness ratio. These materials are potential candidates for memory devices.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Influence of Ag on the Magnetic Anisotropy of Fe{sub 3}O{sub 4} Nanocomposites

In this work, the thermal decomposition method is used to obtain Fe{sub 3}O{sub 4}-Ag nanocomposites. The weight losses observed in the thermogravimetric measurements are used to estimate the amount of organic mass present in the samples. Fourier-transform infrared (FTIR) spectra show characteristic absorption peaks of the stretching vibration of the Fe-O and C-H groups. Samples are characterized structurally and morphologically by measurements of X-ray diffraction (XRD) and transmission electronic microscopy (TEM), respectively. The XRD patterns indicate the formation of a cubic phase with spinel crystallographic structure. Particles sizes analysis estimated by Scherrer’s equation for Fe{sub 3}O{sub 4} phase show that sizes are unaffected by the Ag-insertion. TEM images reveal that the nanoparticles have a spherical-like shape and a mean particles sizes ranging 3 < d < 4 nm. The best fits of zero-field-cooling and field-cooling (ZFC/FC) curves allow us to state that the magnetic anisotropy constant decreasing as a function of Ag concentration.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2021

Effects of a Pressurized Water Treatment on Internal Gelation Sol-Gel Microspheres

Based on previous observations that a pressurized water treatment (PWT) prevented cracking of sol-gel microspheres, we investigated the effects of a PWT on microsphere crystallinity, density, and specific surface area (SSA). Results were used to determine how a PWT alters the properties of microspheres upon drying and heating. Microspheres with diameters near 100-200 µm were prepared with and without a PWT and measured using x-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption (BET), and pycnometry. Properties of air-dried microspheres processed with and without a PWT are compared. Additionally, the properties of microspheres processed using a PWT are reported after heating to 150 °C, 450 °C, 750 °C, 1050 °C, and 1350 °C. X-ray diffraction measurements indicate that the PWT step improves the crystallinity of air-dried microspheres. XRD data was also used to calculate crystallite size, which increases with higher heat treatment temperatures. TEM images support crystallite size calculations from XRD data and provide an indication of the range of crystallite sizes, particularly for samples processed at higher temperatures where crystallite sizes are too large for estimation using the Scherrer formula. Density and SSA measurements performed as a function of heat treatment temperature indicate that a PWT increases the density of air-dried microspheres, creates a pore network, and that significant densification occurs between 450 - 750 °C. These results may be used to inform decisions on internal gelation flowsheet parameters to optimize the microsphere formation and gelation step, prevent microsphere cracking, and produce microspheres suitable for subsequent coating operations or pressing into pellets.

cerium oxide, TRISO, internal gelation, nuclear fu↗