Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “MODIFICATIONS”

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 1,477 records · Page 82
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Synthesis, surface group modification of 3D MnV{sub 2}O{sub 6} nanostructures and adsorption effect on Rhodamine B

Highlights: ► Fabrication of urchin-like MnV{sub 2}O{sub 6} with oxygen-containing surface groups. ► Mn{sub 0.5}V{sub 2}O{sub 5}·nH{sub 2}O as an intermediate product holds the key to the final products. ► 3D architectures of MnV{sub 2}O{sub 6} with oxygen-containing surface groups as sorbent. ► The sorbent shows a good adsorption ability. -- Abstract: Highly uniform 3D MnV{sub 2}O{sub 6} nanostructures modified by oxygen functional groups (-COO-) were successfully prepared in large quantities by an approach involving preparation of vanadyl ethylene glycolate as the precursor. The growth and self-assembly of MnV{sub 2}O{sub 6} nanobelts and nanorods could be readily tuned by additive species and quantities, which brought different morphologies and sizes to the final products. With a focus on the regulation of structure, the formation process of 3D architectures of MnV{sub 2}O{sub 6} by self-assembly of nanobelts was followed by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The consecutive processes of vanadyl ethylene glycolate and benzoyl peroxide assisted formation of layered structure Mn{sub 0.5}V{sub 2}O{sub 5}·nH{sub 2}O, growth of aligned MnV{sub 2}O{sub 6} nanobelts, and oriented assembly were proposed for the growth mechanism. The band gap vs. different morphology was also studied. Optical characterization of these MnV{sub 2}O{sub 6} with different morphologies showed direct bandgap energies at 1.8–1.95 eV. The adsorption properties of 3D MnV{sub 2}O{sub 6} nanostructures synthesized under different conditions were investigated through the removal test of Rhodamine B in aqueous water, and the 3D nanostructures synthesized with 30 g L{sup −1} benzoyl peroxide showed good adsorption capability of Rhodamine B.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Modification of the optical properties of ZnO thin films by proton implantation

Highlights: ► Optical properties of proton-implanted ZnO thin film prepared by rf magneton sputtering were studied. ► Increase in the ordinary refractive index after proton implantation was explained by the polarizability. ► A slight decrease in the optical bandgap by proton implantation was identified. -- Abstract: Optical properties of proton-implanted ZnO thin film prepared by radio-frequency (rf) magneton sputtering have been studied, the optical constants being obtained from the reflectance measurements by employing Cauchy–Urbach model. Increase in the ordinary refractive index after proton implantation was explained by that in the polarizability. Besides, a slight increase in the optical band gap by proton implantation was identified and discussed in terms of the hydrogen shallow donors introduced by the proton implantation.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Synthesis and modification of nano-sized TiO{sub 2} for photo-degradation process under visible light irradiation; a Placket–Burman experimental design

Graphical abstract: - Highlights: • Nanosized TiO{sub 2} doped with nitrogen and iron was produced by sol-gel method. • Linear models were derived to relate the phase and particle size to synthesis factors. • High photocatalytic activity was observed for acetaldehyde degradation. - Abstract: In this research, nitrogen and iron (III) co-doped nano TiO{sub 2} (N-Fe-TiO{sub 2}) was prepared by sol-gel method using ammonium chloride and iron chloride solutions as nitrogen and iron sources, respectively. The effect of synthesis parameters (weight ratios of N/TiO{sub 2} and Fe/TiO{sub 2}, synthesis temperature, calcination time and temperature) was simultaneously investigated on the quality of the N-Fe-TiO{sub 2} product by a two-level Placket–Burman experimental design. The synthesized powders were characterized by XRD, XPS and UV–Vis spectroscopy techniques. The mean crystal size and anatase content were determined and evaluated as the linear functions of so-called synthesis parameters by the statistical analysis and regression. The 2%N-1%Fe-TiO{sub 2} product by 11 nm mean crystal size and 78% anatase content, synthesized at 35 °C and calcined at 500 °C during 2 h, exhibited the most significant activity during the photo-degradation of acetaldehyde under visible light irradiation and its efficiency was obtained about four times more than photocatalytic activity of Degussa TiO{sub 2}-P25.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Surface modifications and optical variations of (−1 1 1) lattice oriented CuO nanofilms for solar energy applications

Graphical abstract: - Highlights: • The films are grown using a low cost SILAR method. • The pH value is found to play a significant role in the property of the resulting films. • The fabrication of band pass filters between 450 nm and 1000 nm is envisaged. • Electrical conductivity and optical band gap values were found to be 68.1 × 10{sup −3} Ω{sup −1} cm{sup −1} and 1.08 eV. • Coating may aid the small band of frequencies could pave way for enhancing the efficiency. - Abstract: This paper reports on the preparation and characterization of Successive Ionic Layer by Adsorption and Reaction (SILAR) grown CuO thin films. The films were deposited onto glass substrates at various solution pH values. The thickness of the film is increased with increase of solution pH values. X-ray diffraction analysis revealed that the prepared films exhibited the monoclinic structure with (−1 1 1) predominant orientation. The optimized pH value is 11 ± 0.1. The microstructure, morphology, optical and electrical properties are studied and reported. The transmission spectra (T) at normal incidence revealed that the films exhibit indirect transitions and may be tailored for passing selected bands of frequencies in visible near IR range. The activation energy is estimated to be about 0.29 eV.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Influence of composition modification on Ca{sub 0.5−x}Mg{sub x}Ti{sub 2}(PO{sub 4}){sub 3} (0.0 ≤ x ≤ 0.5) nanoparticles as electrodes for lithium batteries

Graphical abstract: - Highlights: • Cation mixing was determined in the Ca{sub 0.5−x}Mg{sub x}Ti{sub 2}(PO{sub 4}){sub 3} biphasic series. • Nanometric Ca{sub 0.15}Mg{sub 0.35}Ti{sub 2}(PO{sub 4}){sub 3} delivered 138 mAh/g at C/20 in lithium cells. • Low content of Ca{sup 2+} increases cell volume favoring Li{sup +} insertion in R-3c framework. • Diminution of R{sub SEI} and R{sub CT} for Ca{sub 0.15}Mg{sub 0.35}Ti{sub 2}(PO{sub 4}){sub 3} discharged electrodes. • Fast electrode response for x = 0.35. - Abstract: The Ca{sub 0.5−x}Mg{sub x}Ti{sub 2}(PO{sub 4}){sub 3} series (0.0 ≤ x ≤ 0.5) was prepared by a sol–gel method. X-ray diffraction patterns showed two rhombohedral phases which coexist for intermediate compositions. Despite of the absence of a solid solution mechanism for the whole stoichiometry range, an appreciable cation mixing was observed in both phases. {sup 31}P MAS NMR spectroscopy revealed that low magnesium contents are incorporated to the calcium compound inducing changes in the ordering of the alkaline earth cations in M{sub 1} sites. Derivative plots of the voltage–capacity curves revealed two reversible regions ascribed to the reduction of Ti{sup 4+} to Ti{sup 3+}, ascribable to the subsequent insertion of lithium ions into M{sub 1} and M{sub 2} vacant sites. Capacity values as high as 138 mAh/g after the first discharge were monitored for nanometric Ca{sub 0.15}Mg{sub 0.35}Ti{sub 2}(PO{sub 4}){sub 3} at C/20. Cell cycling under successive kinetic rates revealed a good capacity retention for samples with x = 0.15 and 0.25. Impedance spectra were recorded in lithium cells discharged after different number of cycles at different C rates. The increase in charge transfer resistance was shown to be an important factor determining the electrode behavior on extended cycling.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Characterization, organic modification of wollastonite coated with nano-Mg(OH){sub 2} and its application in filling PA6

Highlights: • Wollastonite is first inorganic modified by coating nano-Mg(OH){sub 2} and then organic modified with silane. • Filling 30% of this composite powder in PA6 the mechanical properties, the heat distortion temperature and oxygen index of the PA6 composites were notably enhanced. - Abstract: Nano-Mg(OH){sub 2} was deposited on the surface of wollastonite (MW) powder with heterogeneous nucleation method and then modified with silane. The microstructure and surface properties of wollastonite (W) and MW powders were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDS) and X-ray diffraction (XRD), respectively. The microstructure of W, MW and silane modified MW (SMW) powders were characterized by Fourier translation infrared spectroscopy (FTIR). The mechanical properties, heat distortion temperature (HDT) and oxygen index (OI) of PA6 composites having different fillers were discussed. It was shown that the surface of wollastonite was coated with a layer of 33 nm thickness of Mg(OH){sub 2} grains and the distribution of which was uniform. The number of the hydroxyl groups on the surface of wollastonite powder increased after coated with Mg(OH){sub 2}. Filling 30% of SMW powder in PA6 the mechanical properties, HDT and OI were notably enhanced.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Modification of Bi:YIG film properties by substrate surface ion pre-treatment

Highlights: • Effects of substrates ion beam treatment on magnetoptical properties Bi:YIG films. • Substrate surface damage results in sign inversion of the magneto-optical effects. • Atomically smooth films growth takes place on low energy ions treated substrates. • High energy ions treatment results in selective nucleation mechanism of the growth. - Abstract: The effect of a controlled ion beam pre-treatment of (1 1 1)-oriented Gd{sub 3}Ga{sub 5}O{sub 12} substrates on the magneto-optical properties and surface morphology of the ultrathin bismuth-substituted yttrium–iron garnet films with a composition Bi{sub 2.8}Y{sub 0.2}Fe{sub 5}O{sub 12} was studied. It has been shown that the observed sign inversion of magneto-optical effects (Faraday rotation and magnetic circular dichroism) observed in films that were deposited on the GGG substrate pre-treated by 1 keV and 4 keV Ar{sup +} ion beams is a result of the substrate surface amorphization caused by the ion bombardment.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Detection of oxygen species generated by WO{sub 3} modification fullerene/TiO{sub 2} in the degradation of 1,5-diphenyl carbazide

Highlights: • Reactive oxygen species were detected through oxidation reaction from DPCI to DPCO. • Generated reactive oxygen species and hydroxyl radicals can be analysed by DPCI degradation. • C{sub 60} have good effect in photo/ultrasonic degradation process. • Enhanced adsorption capacity can increase the degradation effect. • Photocatalytic activity attributed to photo-absorption effect by C{sub 60} and cooperative effect of WO{sub 3} and TiO{sub 2}. - Abstract: In the present work, powders with different relative mole ratios of WO{sub 3}-fullerene/TiO{sub 2} were irradiated by visible light and ultrasonic. The composite obtained was characterized by BET surface area measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), fourier transform infrared (FT-IR), transmission electron microscopy (TEM) and UV–vis analysis. A methylene blue (MB) solution under visible light and ultrasonic irradiation was used to determine the catalytic activity. The generation of reactive oxygen species were detected through the oxidation reaction from 1,5-diphenyl carbazide (DPCI) to 1,5-diphenyl carbazone (DPCO). Finally, we performed experiments to find the optimum relative mole ratio of fullerene for the degradation of MB.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Enhanced photocatalytic performance of g-C{sub 3}N{sub 4} with BiOCl quantum dots modification

Highlights: • Novel BiOCl quantum dots modified g-C{sub 3}N{sub 4} photocatalyst was synthesized. • BiOCl-g-C{sub 3}N{sub 4} showed much higher photocatalytic activity than pure g-C{sub 3}N{sub 4} and BiOCl. • High separation efficiency of photoinduced carriers results in the enhanced performance. - Abstract: Novel BiOCl quantum dots modified g-C{sub 3}N{sub 4} photocatalyst was synthesized by a one-step chemical bath method at low temperature. The photocatalyst was characterized using X-ray diffraction, high-resolution transmission microscopy UV–visible light diffusion reflectance spectrometry, and photoluminescence spectroscopy. The results indicated that BiOCl quantum dots were dispersed on g-C{sub 3}N{sub 4} to form heterojunction structures with high specific surface area. BiOCl-g-C{sub 3}N{sub 4} showed much higher photocatalytic activity than pure g-C{sub 3}N{sub 4} and BiOCl for rhodamine B degradation. The enhanced performance was induced by the high separation efficiency of photoinduced carriers.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Enhanced organic photovoltaic properties via structural modifications in PEDOT:PSS due to graphene oxide doping

Highlights: • Graphene oxide(GO) blended with PEDOT:PSS is used as HTL for PTB7:PCBM BHJ solar cells. • Increase in conductivity due to structural alterations in PEDOT:PSS by GO addition. • The structural alterations are reaveled under Raman spectroscopy, XPS and AFM. • PEDOT:PSS changed to extended coil due to addition of GO to PEDOT:PSS. • Enhanced conductivity after GO addition to PEDOT:PSS resulted in enhanced PCE. - Abstract: Poly(3,4-thylenedioxythiophene):poly(styrene sulfonate), PEDOT:PSS is a well-known conductive polymer for hole transport in organic devices, the properties of which can be enhanced by doping. Common dopants are metal oxides and nanoparticles. In this study, addition of graphene oxide (GO) to PEDOT:PSS as a dopant is addressed in organic photovoltaics (OPVs). With GO doping, electrical conductivity and transport properties of PEDOT:PSS increases due to structural alterations in the presence of −COOH and −OH functional groups in GO. These structural alterations have been revealed under detailed study of Raman spectra, X-ray photoelectron spectroscopy (XPS) analysis, Topographical and conductive Atom force microscopy (AFM/C-AFM) mapping. OPVs fabricated using PEDOT:PSS: GO (5:1) as a hole transport layer (HTL) exhibited a power conversion efficiency (PCE) of 7.68%, which was higher than the 7.01% that was obtained for the OPVs using pristine PEDOT:PSS.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Enhanced catalytic activity of mesoporous graphitic carbon nitride on thermal decomposition of ammonium perchlorate via copper oxide modification

Highlights: • Novel mpg-C{sub 3}N{sub 4}/rod-like CuO nanocomposites were synthesized via a facile precipitation method for the first time. • The BET surface area of as-synthesized mpg-C{sub 3}N{sub 4}/CuO is 111.33 m{sup 2} g{sup −1}, which is beneficial for catalyzing the thermal decomposition process of ammonium perchlorate (AP). • The synergistic effect between mpg-C{sub 3}N{sub 4} and CuO was the origin of the high catalytic activity. • The mpg-C{sub 3}N{sub 4}/CuO nanocomposites were applied in catalyzing the thermal decomposition of AP and the proposed catalytic mechanism was also proposed. - Abstract: Aiming at enhancing the catalytic activity of mpg-C{sub 3}N{sub 4} on thermal decomposition of ammonium perchlorate, mpg-C{sub 3}N{sub 4} was successfully modified by CuO nanorods, via a facile precipitation method. The structure, morphology and composition of mpg-C{sub 3}N{sub 4} and mpg-C{sub 3}N{sub 4}/CuO nanocomposites were characterized by nitrogen adsorption-desorption measurements, transmission electron microscopy, scanning electron microscope, X-ray power diffraction, fourier transform infrared spectroscopy, as well as X-ray photoelectron spectroscopy. The results demonstrated that CuO nanorods (length of 200–300 nm, diameter of 10–15 nm) were uniformly dispersed throughout mpg-C{sub 3}N{sub 4}, efficiently avoiding the agglomeration. Finally, it was demonstrated that the high weight-loss decomposition temperature of AP was decreased up to 118.5 °C in the presence of 2 wt% mpg-C{sub 3}N{sub 4}/CuO nanocomposites, which was higher than that of pure mpg-C{sub 3}N{sub 4} and CuO, respectively, demonstrating the catalytic performances of the nanocomposites was enhanced via the synergistic catalysis between mpg-C{sub 3}N{sub 4} and CuO.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Improving the humidity sensing below 30% RH of TiO2 with GO modification

Highlights: • Rutile phase TiO{sub 2} aggregates were prepared via thermal oxidation of pure Ti-discs, which is simple and inexpensive method. • TiO{sub 2} aggregates with submicron particles based sensor exhibited ultra-high response (R{sub A}/R{sub H{sub 2O}} > 10{sup 6}) to 90% RH. • Sensors based on TiO{sub 2} modified with GO exhibited improved sensitivity, stability and reproducibility. - Abstract: The development of cost-effective, robust, and reliable humidity monitoring system is nowadays in high demand. To this context, humidity sensors based on rutile TiO{sub 2} aggregates were prepared via thermal oxidation of pure Ti-discs at 1000 °C. The sensors based on only TiO{sub 2} aggregates exhibited the ultra-high response of about six orders of magnitude (R{sub A}/R{sub %RH} ∼ 10{sup 6}) to 90% RH with a response time of 28 s and excellent stability. However, these sensors showed no response to RH below 30%, which limits their use in practical applications for such RH level monitoring. Although with a reduced response in high RH, the TiO{sub 2} modified with GO showed potential to overcome this drawback. To understand their functionality, the TiO{sub 2} aggregates and TiO{sub 2}/GO were further characterized by XRD, SEM, TEM, Raman and FT-IR spectroscopy. The presented results are of high interest in terms of wide range humidity monitoring, low-cost and simple synthesis route, and high stability.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Mussel-inspired surface modification of untreated wasted husks with stable polydopamine/polyethylenimine for efficient continuous Cr(VI) removal

Highlights: • Functional rice husks with abundant amino groups was firstly modified with PDA/PEI for Cr(VI) removal. • Potentiality of monolithic samples for dynamic continuous adsorption. • Expectable higher adsorption capacity than most of reported similar bio-sorbents. • Excellent mechanical stability, reusability and convenient separation. - Abstract: A cost-effective and chemically modified biological adsorbent based on agricultural wasted husks for heavy metal removal was fabricated by coating with Polydopamine–Polyethylenimine via the mussel inspired chemistry. Batch and fixed bed column adsorption experiments were carried out to explore the sorption capacity and potency of industrial application. The batch results indicated that the maximum adsorption capacity reached 42.8 mg/g which is much larger than most adsorbents based on bioresource and agricultural wastes for Cr(VI) removal in aqueous solution simultaneously with excellent recycling performance. In column adsorption experiments, it exhibited high mechanical stability and applied potential. The equilibrium time was 9130 min under the flow rate of 1 ml/min, and reached the equilibrium adsorption capacity of 47.14 mg/g. The breakthrough curves ploted by the data of fixed bed experiments under different flow rates (1 ml/min & 2 ml/min) fitted the Thomas model with R{sup 2} of 0.9510 and 0.9437 respectively.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Layer-by-layer modification of aliphatic polyamide anion-exchange membranes to increase Cl - /SO 4 2- selectivity

Development of anion-exchange membranes (AEMs) with selectivities among anions may expand the applications of these membranes in salt separations. This work shows that layer-by-layer coating of aliphatic polyamide AEMs with poly(4-styrenesulfonate) (PSS)/protonated poly(allylamine) (PAH) films enhances Cl - /SO 4 2- dialysis selectivities, and the extent of this enhancement depends on the source-phase salt concentrations. For a source phase containing 0.01 M NaCl and 0.01 M Na 2 SO 4 and a receiving phase of 0.01 M Na 2 CO 3 , a (PSS/PAH) 5 PSS coating (5 PSS/PAH “bilayers” capped with a layer of PSS) increases the Cl - /SO 4 2- selectivity from 1.7 to 5.3 in diffusion dialysis and from 1.3 to 7.4 in electrodialysis. Remarkably, the diffusion dialysis selectivity of a coated membrane increases to 140 when the salt concentrations in the source phase are 0.1 M. Even with bare membranes, selectivity increases to 13 with 0.1 M source-phase salt concentrations. Moreover, AEMs coated only on the receiving side show much higher selectivities but lower fluxes than those coated only on the source side. In conclusion, partitioning experiments and modelling suggest that the increased Cl - /SO 4 2- selectivities at high source-phase salt concentrations stem from enhanced Cl - partitioning and electromigration that disproportionately decreases SO 4 2- flux in the AEM.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗