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1.
Artigo em Inglês | MEDLINE | ID: mdl-32910643

RESUMO

Metallic glasses (MGs) with superior catalytic performance have recently been recognized as attractive candidates for wastewater treatment. However, further improving their performance will require knowledge of how to precisely regulate their electronic structures via compositional control. Here, two Fe-based MGs (Fe78Si9B13 and Fe80Si9B11) were prepared to compare how slightly altering boron content affected their electronic structure and catalytic performance. Density functional theory revealed that the Fe78Si9B13 MG with 2 at.% higher boron exhibits an attractive electron delocalization, a high persulfate adsorption energy, and a superb work function due to precise regulation of the electronic structure, leading to exceptional degradation performance for seven organic pollutants. Furthermore, it can be reused 23 times without significant deterioration of catalytic performance, amorphous structure, or surface morphology. This work provides a new paradigm for fundamental theory explaining how electronic structure is controlled by composition, creating a solid foundation to explore novel catalysts in water treatment.

2.
Materials (Basel) ; 13(17)2020 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-32825550

RESUMO

The as spun amorphous (Fe78Si9B13)99.5Zr0.5 (Zr0.5) and (Fe78Si9B13)99Zr1 (Zr1) ribbons having a Fenton-like reaction are proved to bear a good degradation performance in organic dye wastewater treatment for the first time by evaluating their degradation efficiency in methylene blue (MB) solution. Compared to the widely studied (Fe78Si9B13)100Zr0 (Zr0) amorphous ribbon for degradation, with increasing cZr (Zr atomic content), the as-spun Zr0, Zr0.5 and Zr1 amorphous ribbons have gradually increased degradation rate of MB solution. According to δc (characteristic distance) of as-spun Zr0, Zr0.5 and Zr1 ribbons, the free volume in Zr1 ribbon is higher Zr0 and Zr0.5 ribbons. In the reaction process, the Zr1 ribbon surface formed the 3D nano-porous structure with specific surface area higher than the cotton floc structure formed by Zr0 ribbon and coarse porous structure formed by Zr0.5 ribbon. The Zr1 ribbon's high free volume and high specific surface area make its degradation rate of MB solution higher than that of Zr0 and Zr0.5 ribbons. This work not only provides a new method to remedying the organic dyes wastewater with high efficiency and low-cost, but also improves an application prospect of Fe-based glassy alloys.

3.
J Colloid Interface Sci ; 581(Pt B): 860-873, 2020 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-32818686

RESUMO

Due to the great limitation of glass forming ability, precisely controlling the chemical compositions of metallic glasses (MGs) still dramatically inhibits their widespread applications in wastewater remediation. Here, heterostructured catalysts were exploited by rapid annealing of Fe-based MGs and subsequent ball milling (BM) as advanced alternatives for amorphous counterparts in Fenton-like process. It was found that the surface characteristics tailored by ball milling enable more chemically active sites due to its enlarged specific surface area, surface defects and nanosized amorphous oxide layer that significantly enhance surface-catalyzed reaction in Fenton-like process. On the other hand, high-temperature annealing induced grain growth and electrochemical potential difference induced effect of galvanic cells in multiple crystalline phases (e.g. α-Fe (Si), Fe2B and Fe3Si) further provide an important contribution to high efficiency of electron transfer in heterostructured catalysts. Since the multiphase heterostructure is easily formed by a high-temperature annealing of MGs/amorphous-crystalline composite alloys, this work aims to provide an advanced alternative of MG catalyst without the elemental limitation of glass forming ability for wastewater remediation.

4.
Adv Mater ; : e2000385, 2020 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-32267030

RESUMO

Electrochemical water splitting offers an attractive approach for hydrogen production. However, the lack of high-performance cost-effective electrocatalyst severely hinders its applications. Here, a multinary high-entropy intermetallic (HEI) that possesses an unusual periodically ordered structure containing multiple non-noble elements is reported, which can serve as a highly efficient electrocatalyst for hydrogen evolution. This HEI exhibits excellent activities in alkalinity with an overpotential of 88.2 mV at a current density of 10 mA cm-2 and a Tafel slope of 40.1 mV dec-1 , which are comparable to those of noble catalysts. Theoretical calculations reveal that the chemical complexity and surprising atomic configurations provide a strong synergistic function to alter the electronic structure. Furthermore, the unique L12 -type ordered structure enables a specific site-isolation effect to further stabilize the H2 O/H* adsorption/desorption, which dramatically optimizes the energy barrier of hydrogen evolution. Such an HEI strategy uncovers a new paradigm to develop novel electrocatalyst with superior reaction activities.

5.
Water Res ; 167: 115110, 2019 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-31577967

RESUMO

Membrane separation and advanced oxidation processes (AOPs) have been respectively demonstrated to be effective for a variety of water and/or wastewater treatments. Innovative integration of membrane with catalytic oxidation is thus expected to be more competing for more versatile applications. In this study, ceramic membranes (CMs) integrated with manganese oxide (MnO2) were designed and fabricated via a simple one-step ball-milling method with a high temperature sintering. Functional membranes with different loadings of MnO2 (1.67%, 3.33% and 6.67% of the total membrane mass) were then fabricated. The micro-structures and compositions of the catalytic membranes were investigated by a number of advanced characterisations. It was found that the MnO2 nanocatalysts (10-20 nm) were distributed uniformly around the Al2O3 particles (500 nm) of the membrane basal material, and can provide a large amount of active sites for the peroxymonosulfate (PMS) activation which can be facilitated within the pores of the catalytic membrane. The catalytic degradation of 4-hydroxylbenzoic acid (HBA), which is induced by the sulfate radicals via PMS activation, was investigated in a cross-flow membrane unit. The degradation efficiency slightly increased with a higher MnO2 loading. Moreover, even with the lowest loading of MnO2 (1.67%), the effectiveness of HBA degradation was still prominent, shown by that a 98.9% HBA degradation was achieved at the permeated side within 30 min when the initial HBA concentration was 80 ppm. The stability and leaching tests revealed a good stability of the catalytic membrane even after the 6th run. Electron paramagnetic resonance (EPR) and quenching tests were used to investigate the mechanism of PMS activation and HBA degradation. Both sulfate radicals (SO4•-) and hydroxyl radicals (•OH) were generated in the catalytic membrane process. Moreover, the contribution from non-radical process was also observed. This study provides a novel strategy for preparing a ceramic membrane with the function of catalytic degradation of organic pollutants, as well as outlining into future integration of separation and AOPs.


Assuntos
Poluentes Ambientais , Compostos de Manganês , Cerâmica , Óxidos , Sulfatos
6.
Adv Mater ; 30(45): e1802764, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30277608

RESUMO

Metallic glasses (MGs) with the metastable nature and random atomic packing structure have attracted large attention in the catalytic family due to their superior catalytic performance. In contrast, their crystalline counterparts are restricted by the highly ordered packing structure, fewer surface active sites, and crystallographic defects for catalytic activity. The uncertainty of the different catalytic mechanisms and the intrinsic characteristics correlated to MGs and their crystalline counterparts become a major impediment to promote their catalytic efficiencies and widespread applications. Herein, it is reported that the excellent catalytic behavior in Fe-based MGs goes through a detrimental effect with the partial crystallization, but receives a compelling rejuvenation in the full crystallization. Further investigation reveals that multiphase intermetallics with electric potential differences in fully crystallized alloys facilitate the formation of galvanic cells. More importantly, extensively reduced grain boundaries due to grain growth greatly weaken electron trapping and promote inner electron transportation. The relatively homogenous grain-boundary corrosion in the intermetallics contributes to well-separated phases after reaction, leading to refreshment of the surface active sites, thereby quickly activating hydrogen peroxide and rapidly degrading organic pollutants. The exploration of catalytic mechanisms in the crystalline counterparts of MGs provides significant insights into revolutionize novel catalysts.

7.
Chem Asian J ; 13(23): 3575-3592, 2018 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-30225995

RESUMO

With an intrinsically disordered atomic structure and a widely tunable atomic constituent, metallic glasses (MGs) have been extensively studied as promising catalysts in different catalytic fields. Particularly, Fe-based MGs with high catalytic activity, relatively low material cost, and environmental friendly compatibility also emerge as advanced catalysts. This review systematically discusses the recent advances of Fe-based MGs in catalytic applications, including wastewater remediation based on reductive degradation by multicomponent Fe-based MGs, oxidative degradation by introduction of advanced oxidation processes (AOPs) and nanocrystallization applied in Fe-based MGs up to date, and renewable energy conversion, with purposes of revealing Fe-based MG catalysts in the further improvement of catalytic performance and exploiting their promising catalytic abilities in a widely catalytic field.

8.
Adv Mater ; 30(39): e1803351, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30059172

RESUMO

Quasi-1D cadmium chalcogenide quantum rods (QRs) are benchmark semiconductor materials that are combined with noble metals to constitute QR heterostructures for efficient photocatalysis. However, the high toxicity of cadmium and cost of noble metals are the main obstacles to their widespread use. Herein, a facile colloidal synthetic approach is reported that leads to the spontaneous formation of cadmium-free alloyed ZnSx Se1-x QRs from polydisperse ZnSe nanowires by alkylthiol etching. The obtained non-noble-metal ZnSx Se1-x QRs can not only be directly adopted as efficient photocatalysts for water oxidation, showing a striking oxygen evolution capability of 3000 µmol g-1 h-1 , but also be utilized to prepare QR-sensitized TiO2 photoanodes which present enhanced photo-electrochemical (PEC) activity. Density functional theory (DFT) simulations reveal that alloyed ZnSx Se1-x QRs have highly active Zn sites on the (100) surface and reduced energy barrier for oxygen evolution, which in turn, are beneficial to their outstanding photocatalytic and PEC activities.

9.
ACS Appl Mater Interfaces ; 9(36): 30703-30710, 2017 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-28829113

RESUMO

For the first time, a porous and conductive Co0.85Se/graphene network (CSGN), constructed by Co0.85Se nanocrystals being tightly connected with each other and homogeneously anchored on few-layered graphene nanosheets, has been synthesized by a facile one-pot solvothermal method. Compared to unhybridized Co0.85Se, CSGN exhibits much faster kinetics and better electrocatalytic behavior for hydrogen evolution reaction (HER). The HER mechanism of CSGN is improved to Volmer-Tafel combination, instead of Volmer-Heyrovsky combination, for Co0.85Se. CSGN has a very low Tafel slope of 34.4 mV/dec, which is much lower than that of unhybridized Co0.85Se (41.8 mV/dec) and is the lowest ever reported for Co0.85Se-based electrocatalysts. CSGN delivers a current density of 55 mA/cm2 at 250 mV overpotential, much larger than that of Co0.85Se (33 mA/cm2). Furthermore, CSGN shows superior electrocatalytic stability even after 1500 cycles. The excellent HER performance of CSGN is attributed to the unique porous and conductive network, which can not only guarantee interconnected conductive paths in the whole electrode but also provide abundant catalytic active sites, thereby facilitating charge transportation between the electrocatalyst and electrolyte. This work provides insight into rational design and low-cost synthesis of nonprecious transition-metal chalcogenide-based electrocatalysts with high efficiency and excellent stability for HER.

10.
Sci Rep ; 6: 38520, 2016 12 06.
Artigo em Inglês | MEDLINE | ID: mdl-27922099

RESUMO

Stability and reusability are important characteristics of advanced catalysts for wastewater treatment. In this work, for the first time, sulfate radicals (SO4∙-) with a high oxidative potential (Eo = 2.5-3.1 V) were successfully activated from persulfate by a Fe78Si9B13 metallic glass. This alloy exhibited a superior surface stability and reusability while activating persulfate as indicated by it being used for 30 times while maintaining an acceptable methylene blue (MB) degradation rate. The produced SiO2 layer on the ribbon surface expanded strongly from the fresh use to the 20th use, providing stable protection of the buried Fe. MB degradation and kinetic study revealed 100% of the dye degradation with a kinetic rate k = 0.640 within 20 min under rational parameter control. The dominant reactive species for dye molecule decomposition in the first 10 min of the reaction was hydroxyl radicals (∙OH, Eo = 2.7 V) and in the last 10 min was sulfate radicals (SO4∙-), respectively. Empirical operating variables for dye degradation in this work were under catalyst dosage 0.5 g/L, light irradiation 7.7 µW/cm2, and persulfate concentration 1.0 mmol/L. The amorphous Fe78Si9B13 alloy in this work will open a new gate for wastewater remediation.

11.
Sci Rep ; 6: 23905, 2016 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-27049025

RESUMO

NiTi wires were brazed together via eutectic reaction between NiTi and Nb powder deposited at the wire contact region. Phase transformation and deformation behavior of the NiTi-Nb eutectic microstructure were investigated using transmission electron microscopy (TEM) and cyclic loading-unloading tests. Results show that R phase and B19' martensite transformation are induced by plastic deformation. R phase transformation, which significantly contributes to superelasticity, preferentially occurs at the interfaces between NiTi and eutectic region. Round-shaped Nb-rich phase with rod-like and lamellar-type eutectics are observed in eutectic regions. These phases appear to affect the deformation behavior of the brazed NiTi-Nb region via five distinct stages in stress-strain curves: (I) R phase reorientation, (II) R phase transformation from parent phase, (III) elastic deformation of reoriented martensite accompanied by the plastic deformation of Nb-rich phase and lamellar NiTi-Nb eutectic, (IV) B19' martensitic transformation, and (V) plastic deformation of the specimen.

12.
Mater Sci Eng C Mater Biol Appl ; 60: 503-510, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26706557

RESUMO

A series of Ti-7Fe-xNb (x=0, 1, 4, 6, 9, 11 wt.%) alloys was designed and cast to investigate the ß→α″ martensitic phase transformation, ß phase stability, the resulting microstructure and mechanical properties. Phase analysis revealed that only Ti-7Fe-11Nb alloy shows a single body-centred cubic ß phase microstructure while the others are comprised of ß and orthorhombic α″ phases. Moreover, Nb addition up to 11 wt.% enhances the stability and volume fraction of ß phase in the microstructure, hence reducing the propensity of the alloy system to form α″ phase during quenching. Compressive yield strength and hardness of the alloys are (985-1847) MPa and (325-520) Hv respectively. Additionally, Ti-7Fe-11Nb possesses the lowest Young's modulus (84 GPa) and the highest deformability (42% strain) among the designed alloys due to the single ß phase microstructure. This high deformability is also corroborated by the large plastic deformation zone underneath the Vickers indenter. In contrast, the fractured surfaces of Ti-7Fe and Ti-7Fe-1Nb alloys after compressive tests mostly contain shallow dimples, verifying their low ductility. The good combination of mechanical properties obtained for Ti-7Fe-11Nb renders it more desirable than commonly used CP-Ti and Ti-6Al-4V materials and makes it a promising candidate for biomedical application.


Assuntos
Ligas/química , Ferro/química , Nióbio/química , Titânio/química , Teste de Materiais , Resistência à Tração
13.
Mater Sci Eng C Mater Biol Appl ; 33(5): 2788-94, 2013 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-23623097

RESUMO

Surface engineering through the application of super-hard, low-friction coatings as a potential approach for increasing the durability of metal-on-metal replacements is attracting significant attention. In this study innovative design strategies are proposed for the development of diamond-like-carbon (DLC) coatings against the damage caused by wear particles on the joint replacements. Finite element modeling is used to analyze stress distributions induced by wear particles of different sizes in the newly-designed coating in comparison to its conventional monolithic counterpart. The critical roles of architectural design in regulating stress concentrations and suppressing crack initiation within the coatings is elucidated. Notably, the introduction of multilayer structure with graded modulus is effective in modifying the stress field and reducing the magnitude and size of stress concentrations in the DLC diamond-like-carbon coatings. The new design is expected to greatly improve the load-carrying ability of surface coatings on prosthetic implants, in addition to the provision of damage tolerance through crack arrest.


Assuntos
Carbono/química , Materiais Revestidos Biocompatíveis , Diamante , Prótese Articular , Análise de Elementos Finitos
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