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At least 1,729 records · Page 96

Formation of nanogranular ZnO ultrathin films and estimation of their performance for photocatalytic degradation of amoxicillin antibiotic

Highlights: • A modified sol–gel process with addition of ammonium acetate to form ZnO nanograins. • ZnO very thin layers with particular nano-granular morphology. • Opportunity to form mono-layers of separated nano-grains. • Correlated effects observed on morphology and dielectric function. • Efficient photo-degradation of amoxicillin antibiotic. - Abstract: Very thin nanogranular zinc oxide layers have been grown using sol–gel synthesis modified by incorporating ammonium acetate with varying content. Ammonium acetate has multiple correlated effects such as thickness reduction from 70 to 20 nm; grains size reduction from 50 nm to 25 nm; and morphology evolution from a dense stacking of grains to a single layer of grains. The potential application to photocatalytic degradation of pharmaceutical materials has been evaluated by carrying out the degradation of amoxicillin antibiotic under UV irradiation. The particular nanogranular morphology of the layers positively impacts the photodegradation efficiency.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

NASA JSC’s Simulant Development Lab Capabilities and Artemis Testing

The Simulant Development Lab (SDL) is a multifunctional collaborative workspace that supports the development, curation, analysis, testing, and distribution of planetary regolith simulants – including lunar, Martian, asteroidal, and other granular materials. The lab provides a multidisciplinary setting for scientific characterization of simulant physical properties and for engineering evaluations conducted with simulant test beds. To enable this work, the SDL curates and maintains a stock of more than 35 metric tons of simulant material. To evaluate these materials and support testing goals, the lab is equipped with a comprehensive suite of processing tools and analytical instruments. These capabilities enable the SDL’s mission at NASA’s Johnson Space Center to distribute, develop, process, characterize, and test regolith simulants for mission relevant applications. Through controlled and repeatable testing environments that replicate the physical and compositional properties of lunar regolith, the SDL supports Artemis hardware maturation, providing safe, Earth‑based analogs for evaluating systems that must withstand regolith dust interactions, physical wear and abrasion, and operational loads. The facility’s extensive simulant inventory and integrated geological and engineering test infrastructure accelerate technology readiness for Artemis and future exploration campaigns (e.g., future crewed or robotic missions to Mars).

Simulant Development Lab↗

Forum on Materials and Interfaces for Energy Storage and Conversion

This ACS Applied Materials & Interfaces forum on energy storage and conversion contains the topics of research discoveries to advance energy technology development. The topics are focused on the efficient and sustainable use of energy in the fields of fuel cells, CO 2 conversion, water splitting, batteries, and electrochemical capacitor. This forum highlights recent achievements in these emerging technologies through the design and evaluation of novel materials and devices and theoretical study. Additionally, this forum also showcases the technology at all stages of development from “embryonic” conception to industrial adaptation.

25 ENERGY STORAGE↗

Optimal application of Morrison's iterative noise removal for deconvolution

Morrison's iterative method of noise removal can be applied for both noise removal alone and noise removal prior to deconvolution. This method is applied to noise of various noise levels added to determine the optimum use of the method. The phase shift method of migration and modeling is evaluated and the results are compared to Stolt's approach. A method is introduced by which the optimum iterative number for deconvolution can be found. Statistical computer simulation is used to describe the optimum use of two convergent iterative techniques for seismic data. The Always-Convergent deconvolution technique was applied to data recorded during the quantitative analysis of materials through NonDestructive Evaluation (NDE) in which ultrasonic signals were used to detect flaws in substances such as composites.

Ioup, George E.↗

Study on the Properties of Novel Soft Magnetic Composites of FeSiAl

In this paper, we compounded the FeSiAl powder with a novel amorphous inorganic insulation agent (AIIA). Silicone resin (3 wt.%) was used as organic insulating agent, and the inorganic insulating agent was Fe{sub 83.5}Si{sub 7.5}B{sub 5}Cr{sub 4} amorphous powder (0, 1, 2, 3, and 4 wt.%). Amorphous powder was prepared by passivation pretreatment before compounding. The results showed that the addition of amorphous inorganic insulating agent will significantly affect the soft magnetic properties of FeSiAl powders. Compared with the pure FeSiAl powder having only silicone resin the saturation magnetization of composite powders slightly increased (by 0.1–4.9%). When AIIA content was 2 wt.%, the sample had the highest initial permeability, which increased by 14.6%. At the same time, the core loss was also reduced by 15.7% (B{sub m} = 5 mT, f = 1000 kHz) when AIIA content was also 2 wt.%.

36 MATERIALS SCIENCE↗

Microstructure and Interfacial Shear Strength in W/(Zr{sub 55}Cu{sub 30}Al{sub 10}Ni{sub 5}){sub 100−x}Nb{sub x} Composites

In the present study, (Zr{sub 55}Cu{sub 30}Al{sub 10}Ni{sub 5}){sub 100−x}Nb{sub (x=0,1,2,3)} bulk metallic glass matrix/tungsten wire composites were fabricated by a gas pressure infiltration process at temperature 950 °C for 5 min. Microstructural studies and mechanical behaviors of the materials have been investigated by scanning electron microscopy, transmission electron microscopy and pullout tests. The mechanical results showed that the interface shear strength in the composite sample with X = 2 increased more than twice compared to the composite sample with X = 0. Based on the microstructural results, the addition of two atomic percent Nb in the matrix composite causes an increase in the diffusion band thickness during the melt infiltration and change in the interface fracture mode as a result of pullout test.

36 MATERIALS SCIENCE↗

Controlled High Filler Loading of Functionalized Al{sub 2}O{sub 3}-Filled Epoxy Composites for LED Thermal Management

Thermal management in light-emitting diode (LED) has been extensively researched recently. This study is intended to develop an effective thermally conductive epoxy composite as thermal interface material (TIM) for headlamp LEDs. Silane-functionalized aluminum oxide (Al{sub 2}O{sub 3}) powder of different average particle sizes (44 and 10 µm) was studied for its feasibility as filler at its maximum loading. A detailed comparison of three different methods of particle dispersions, hand-mix, speed-mix and calendaring process (3-roll mill), has been reported. The dispersion of Al{sub 2}O{sub 3} particles, the thermal conductivity and thermal degradation characteristics of the composites were investigated and explained in detail. At 75 wt.% filler loading, 10 and 44 µm Al{sub 2}O{sub 3} achieved composite thermal conductivities of 1.13 and 2.08 W/mK, respectively, which is approximately 528 and 1055% of enhancement with respect to neat epoxy. The package-level thermal performance of the LED employing the Al{sub 2}O{sub 3}-filled TIMs was carried out using thermal transient analysis. The experimental junction-to-ambient thermal resistances (R{sub thJ-A}) achieved were 6.65, 7.24, and 8.63 K/W for Al{sub 2}O{sub 3-44µm}, Al{sub 2}O{sub 3-10µm} and neat epoxy, respectively. The results revealed that the Al{sub 2}O{sub 3-44µm} fillers-filled composite performed better in both material-level and package-level thermal characteristics.

36 MATERIALS SCIENCE↗

Static and Dynamic Mechanical Properties of Graphene Oxide-Incorporated Woven Carbon Fiber/Epoxy Composite

This study investigates the synergistic effects of graphene oxide (GO) on the woven carbon fiber (CF)-reinforced epoxy composites. The GO nanofiller was incorporated into the epoxy resin with variations in the content, and the CF/epoxy composites were manufactured using a vacuum-assisted resin transfer molding process and then cured at 70 and 120 °C. An analysis of the mechanical properties of the GO (0.2 wt.%)/CF/epoxy composites showed an improvement in the tensile strength, Young’s modulus, toughness, flexural strength and flexural modulus by ~ 34, 20, 83, 55 and 31%, respectively, when compared to the CF/epoxy composite. The dynamic mechanical analysis of the composites exhibited an enhancement of ~ 56, 114 and 22% in the storage modulus, loss modulus and damping capacity (tanδ), respectively, at its glass transition temperature. The fiber–matrix interaction was studied using a Cole–Cole plot analysis.

36 MATERIALS SCIENCE↗

Electron Backscattered Diffraction Study of Pulse Electrodeposited Cu-Y{sub 2}O{sub 3} Composite Coating

The current investigation is an effort of correlating the grain growth, crystallographic orientation and second-phase Y{sub 2}O{sub 3} particles to the mechanical properties of the electrodeposited pure copper (Cu) and Cu-Y{sub 2}O{sub 3} coatings. Energy-dispersive spectrum and elemental mapping confirm the codeposition of Y{sub 2}O{sub 3} in the composite coating matrix, which indeed justifies the composite (Cu-Y{sub 2}O{sub 3}) coating. Both pure Cu and Cu-Y{sub 2}O{sub 3} coatings have (101) preferred orientation; however, the volume fraction is found comparatively lower in composite coating. Both microstructural and textural characterization through electron backscattered diffraction technique show significant grain refinement in case of Cu-Y{sub 2}O{sub 3} composite coating compared to pure Cu coating, and prominent 〈011〉 fiber texture is observed in case of pure Cu coating compared to composite coating. By the addition of second-phase Y{sub 2}O{sub 3} in the matrix, the 〈011〉 fiber texture is disintegrated and concentrated at ϕ{sub 1} = 37°, ϕ = 45°, ϕ{sub 2} = 0°. Despite lower volume fraction of 〈011〉 fiber texture, better mechanical properties (hardness and wear resistance) of the composite coating compared to pure Cu coating can be attributed to finer grain size, higher misorientation angle and incorporation of second-phase Y{sub 2}O{sub 3} particles.

36 MATERIALS SCIENCE↗

Nano-modification to improve the ductility of cementitious composites

Effect of nano-sized mineral additions on ductility of engineered cementitious composites (ECC) containing high volumes of fly ash was investigated at different hydration degrees. Various properties of ECC mixtures with different mineral additions were compared in terms of microstructural properties of matrix, fiber-matrix interface, and fiber surface to assess improvements in ductility. Microstructural characterization was made by measuring pore size distributions through mercury intrusion porosimetry (MIP). Hydration characteristics were assessed using thermogravimetric analysis/differential thermal analysis (TGA/DTA), and fiber-matrix interface and fiber surface characteristics were assessed using scanning electron microscopy (SEM) through a period of 90 days. Moreover, compressive and flexural strength developments were monitored for the same period. Test results confirmed that mineral additions could significantly improve both flexural strength and ductility of ECC, especially at early ages. Cheaper Nano-CaCO{sub 3} was more effective compared to nano-silica. However, the crystal structure of CaCO{sub 3} played a very important role in the range of expected improvements.

36 MATERIALS SCIENCE↗

Efficient H{sub 2} production over Au/graphene/TiO{sub 2} induced by surface plasmon resonance of Au and band-gap excitation of TiO{sub 2}

Highlights: • Both surface plasmon resonance and band-gap excitation were used for H{sub 2} production. • Au/Gr/TiO{sub 2} composite photocatalyst was synthesized. • Au/Gr/TiO{sub 2} exhibited enhancement of light absorption and charge separation. • H{sub 2} production rate of Au/Gr/TiO{sub 2} was about 2 times as high as that of Au/TiO{sub 2}. - Abstract: H{sub 2} production over Au/Gr/TiO{sub 2} composite photocatalyst induced by surface plasmon resonance of Au and band-gap excitation of TiO{sub 2} using graphene (Gr) as an electron acceptor has been investigated. Electron paramagnetic resonance study indicated that, in this composite, Gr collected electrons not only from Au with surface plasmon resonance but also from TiO{sub 2} with band-gap excitation. Surface photovoltage and UV–vis absorption measurements revealed that compared with Au/TiO{sub 2}, Au/Gr/TiO{sub 2} displayed more effective photogenerated charge separation and higher optical absorption. Benefiting from these advantages, the H{sub 2} production rate of Au/Gr/TiO{sub 2} composite with Gr content of 1.0 wt% and Au content of 2.0 wt% was about 2 times as high as that of Au/TiO{sub 2}. This work represents an important step toward the efficient application of both surface plasmon resonance and band-gap excitation on the way to converting solar light into chemical energy.

36 MATERIALS SCIENCE↗

One-step synthesis of homogeneous BaFe{sub 12}O{sub 19}/Y{sub 3}Fe{sub 5}O{sub 12} composite powders

Highlights: • A simple one-step sol–gel method was used to synthesize composite magnets. • The composite powders show good homogeneity and exchange coupling. • The M{sub r}/M{sub s} value increases with the BaM concentration. - Abstract: BaFe{sub 12}O{sub 19}/Y{sub 3}Fe{sub 5}O{sub 12} (BaM/YIG) composite powders were synthesized via a simple one-step sol–gel method. The phase composition and morphology of the as-synthesized composite powders were characterized using an X-ray diffractometer and a scanning electron microscopy equipped with energy dispersive X-ray spectroscopy. The magnetic properties of the composite powders were investigated by a vibrating sample magnetometer. Compared with the composite powders prepared by the conventional physical mixing method, the BaM/YIG composite powders show better homogeneity and exchange coupling.

36 MATERIALS SCIENCE↗

Dielectric relaxation of gamma irradiated muscovite mica

Highlights: • The present article reports the effect of gamma irradiation on the dielectric relaxation characteristics of muscovite mica. • Dielectric and electrical relaxations have been analyzed in the framework of dielectric permittivity, electric modulus and Cole–Cole formalisms. • The frequency dependent electrical conductivity has been rationalized using Johnsher’s universal power law. • The experimentally measured electric modulus and conductivity data have been fitted using Havriliak–Negami dielectric relaxation function. - Abstract: In the present research, the dielectric relaxation of gamma irradiated muscovite mica was studied in the frequency range of 0.1 Hz–10 MHz and temperature range of 653–853 K, using the dielectric permittivity, electric modulus and conductivity formalisms. The dielectric constants (ϵ′ and ϵ′′) are found to be high for gamma irradiated muscovite mica as compared to the pristine sample. The frequency dependence of the imaginary part of complex electric modulus (M′′) and dc conductivity data conforms Arrhenius law with single value of activation energy for pristine sample and two values of activation energy for gamma irradiated mica sample. The experimentally assessed electric modulus and conductivity information have been interpreted by the Havriliak–Negami dielectric relaxation explanation. Using the Cole–Cole framework, an analysis of real and imaginary characters of the electric modulus for pristine and gamma irradiated sample was executed which reflects the non-Debye relaxation mechanism.

36 MATERIALS SCIENCE↗

Solar photocatalytic activities of porous Nb-doped TiO{sub 2} microspheres by coupling with tungsten oxide

Highlights: • Nb-TiO{sub 2}/WO{sub 3} was prepared by USP method combined impregnation method. • Nb-doping extend the spectral absorption of TiO{sub 2} into visible spectrum. • Nb-TiO{sub 2}/WO{sub 3} has a similar optical band gap as Nb-TiO{sub 2}. • PL spectra indicate WO{sub 3} can accept the photoexcited electrons from Nb-TiO{sub 2}. • Nb-TiO{sub 2}/WO{sub 3} shows higher activity than TiO{sub 2} and Nb-TiO{sub 2} under solar light. - Abstract: Nb doped TiO{sub 2} microspheres modified with WO{sub 3} (Nb-TiO{sub 2}/WO{sub 3}) was prepared by ultrasonic spray pyrolysis method combined with impregnation method. The microspheres were characterized with SEM, TEM, XRD, BET, photoluminescence and UV–vis absorption spectra. The Nb-doping was observed to extend the spectral absorption of TiO{sub 2} into visible spectrum, and the absorption onset was red-shifted for about 88 nm compared to pristine TiO{sub 2} microspheres. Nb-TiO{sub 2}/WO{sub 3} microspheres do not display a red-shifted absorption edge compared with Nb doped TiO{sub 2} microspheres. Under solar irradiation, Nb-TiO{sub 2}/WO{sub 3} microspheres showed higher photocatalytic activity for methylene blue degradation compared with that of pure TiO{sub 2} microspheres and Nb doped TiO{sub 2} microspheres, which could be ascribed to the extended light absorption range and the suppression of electron-hole pair recombination.

36 MATERIALS SCIENCE↗

Investigation of methanol oxidation on a highly active and stable Pt–Sn electrocatalyst supported on carbon–polyaniline composite for application in a passive direct methanol fuel cell

Highlights: • PtSn/C-PANI performed superior in the MOR compared with a commercial PtRu/C. • Catalytic activity of PtRu/C was highly reduced during the accelerated durability test. • Anode of the PtSn/C-PANI in a passive DMFC lowered methanol crossover by 30%. - Abstract: Polyaniline fiber (PANI) was synthesized and utilized to fabricate a vulcan–polyaniline (C-PANI) composite. Pt/C-PANI and PtSn/C-PANI electro-catalysts with different Pt:Sn atomic ratios were prepared by the impregnation method. These electro-catalysts, along with commercial PtRu/C (Electrochem), were characterized with respect to their structural and electrochemical properties in methanol oxidation reaction (MOR). PtSn(70:30)/C-PANI showed excellent performance in MOR, the obtained maximum current density being about 40% and 50% higher than that for PtRu/C and Pt/C-PANI, respectively. It was also found that the CO tolerance and stability of PtSn(70:30)/C-PANI was considerably higher than that of PtRu/C. Finally, the performance of these two materials was compared in a passive direct methanol fuel cell (DMFC). The DMFC test results demonstrated that the membrane electrode assembly (MEA) prepared using PtSn(70:30)/C-PANI anode catalyst performed more satisfactorily in terms of maximum power density and lower methanol crossover.

36 MATERIALS SCIENCE↗

Effect of ultrasound treatment on the morpho-structural and luminescent characteristics of cerium doped yttrium silicate phosphors

Highlights: • Y{sub 2}SiO{sub 5}:Ce is prepared by gel combustion in ultrasound conditions (US). • Morpho-structural characteristics are revealed based on FTIR, SEM, XRD, BET. • Incorporation of Ce{sup 3+} in X1/X2 type centers depends on preparative conditions. • US treatment increases the luminescent performances up to 151%. - Abstract: Cerium activated yttrium silicate (Y{sub 2}SiO{sub 5}:Ce) phosphors were prepared by gel-combustion, using yttrium–cerium nitrate as oxidizer, aspartic acid as fuel and TEOS as source of silicon. Two modalities for samples preparation were approached namely: the classical gel-combustion and sonication gel-combustion. The ultrasound treatment during the gelling stage has a positive effect on the structural and luminescent characteristics of the final product. Therefore, a well crystallized single X2–Y{sub 2}SiO{sub 5} phase phosphor was obtained at 1200 °C. Based on FT-IR and XRD investigations, conversion of X1 to X2–Y{sub 2}SiO{sub 5} phases is observed as the firing temperature is varied (1100 °C, 1200 °C, 1300 °C 1400 °C). The ultrasound treatment leads to smaller particle size and enhances the luminescent performances up to 151% in comparison with samples prepared by classical way.

36 MATERIALS SCIENCE↗

A new strategy on utilizing nitrogen doped TiO{sub 2} in nanostructured solar cells: Embedded multifunctional N-TiO{sub 2} scattering particles in mesoporous photoanode

Highlights: • N-doped TiO{sub 2} scattering particles were synthesized for embedding into commercial photoanode of dye sensitized solar cells. • Embedded scatterers improved optical and electrical features of the cells. • These multifunctional scatterers increased cell performance up to 17%. - Abstract: Aggregated sub-micron size nitrogen doped TiO{sub 2} (N-TiO{sub 2}) particles with superior optical and electrical features were successfully synthesized for embedding into commercial mesoporous TiO{sub 2} photoelectrode of dye sensitized solar cells (DSSCs) as the light scattering particles compared to undoped one. X-ray photoelectron spectroscopy and absorption spectra confirmed that the titanium dioxide is sufficiently doped by nitrogen in N-TiO{sub 2} sample. Employing these high-surface N-TiO{sub 2} in mesoporous photoelectrode of solar cells, the power conversion efficiency of 8% has been achieved which shows 17% improvement for the optimum embedded level of doping (30 wt%) compared to commercial photoelectrode without additive; while enhanced efficiency is only 3% embedding undoped sub-micron size TiO{sub 2} particles. These results can introduce the novel multifunctional photoelectrode for nanostructured solar cells with enhanced values of scattering efficiency and improved electrical features including trap states density reduction in comparison to commercial mesoporous photoelectrodes.

14 SOLAR ENERGY↗

Controlled synthesis of Ag{sub 3}PO{sub 4}/BiVO{sub 4} composites with enhanced visible-light photocatalytic performance for the degradation of RhB and 2, 4-DCP

Highlights: • Ag{sub 3}PO{sub 4}/BiVO{sub 4} composites were synthesized by in-situ precipitation method. • Ag{sub 3}PO{sub 4}/BiVO{sub 4} is more efficient than pure Ag{sub 3}PO{sub 4} and BiVO{sub 4} for RhB and 2, 4-DCP degradation. • Ag{sub 3}PO{sub 4}/BiVO{sub 4} can act as a high performance and low cost photocatalyst. - Abstract: Ag{sub 3}PO{sub 4}/BiVO{sub 4} composites were fabricated by in-situ precipitation method. Results showed that Ag{sub 3}PO{sub 4}/BiVO{sub 4} composites exhibited higher photocatalytic activity than that of pure BiVO{sub 4} and Ag{sub 3}PO{sub 4} sample under visible light irradiation. The effect of Ag{sub 3}PO{sub 4}:BiVO{sub 4} ratio on the photocatalytic activity was systemically studied and the optimum molar ratio of Ag{sub 3}PO{sub 4}:BiVO{sub 4} was 1:5. The Ag{sub 3}PO{sub 4}/BiVO{sub 4}-5 exhibited excellent photocatalytic activity for the degradation of Rhodamine B (ca. 92% in 30 min) and 2, 4-dichlorophenol (ca. 84% in 180 min) under visible light irradiation. The enhanced photocatalytic activity could be mainly ascribed to the suitable Ag{sub 3}PO{sub 4}/BiVO{sub 4} heterojunction interface and the smaller particles of Ag{sub 3}PO{sub 4} compared to pure Ag{sub 3}PO{sub 4} particles which could promote the separation of photoinduced electron-hole pairs. The Ag{sub 3}PO{sub 4}/BiVO{sub 4} composite can significantly reduce the silver consumption compared to the pure Ag{sub 3}PO{sub 4}. It is worth noting that Ag{sub 3}PO{sub 4}/BiVO{sub 4} composite can act as a high performance and low cost visible-light-driven photocatalyst for environmental remediation.

36 MATERIALS SCIENCE↗