Growth of carbon nanofibres on molybdenum carbide nanowires and their self-decoration with noble-metal nanoparticles

High specific surface area makes carbon nanofibres suitable for catalyst support. Here we report on optimization of carbon nanofibre (CNF) growth on molybdenum carbide nanowires (MoCNW) by direct carburization of Mo 6 S 2 I 8 nanowire bundles. Typical CNFs obtained by this method are several hundreds of nanometres long at a diameter of 10–20 nm. We show that nanofibre growth does not depend on the initial morphology of the nanowires: nanofibres grow on individual bundles of MoCNW, on dense networks of nanowires deposited on silicon substrate, and on free-standing nanowire foils. We find that carbon nanofibres remain firmly attached to the nanowires even if they are modified into Mo 2 C and further into Mo S 2 nanowires. The method thus enables production of a novel hybrid material composed of Mo S 2 nanowires densely covered with carbon nanofibres. We have additionally shown that the obtained CNFs can easily be self-decorated with platinum nanoparticles with diameters of several nanometres directly from water solution at room temperature without reducing agents. Such efficient synthesis and decoration process yield hybrid platinum/CNF/molybdenum-based NW materials, which are a promising material for a wide range of possible future applications, including sensitive sensorics and improved catalysis.

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A Perspective on the Application of Covalent Organic Frameworks for Detection and Water Treatment

Nanomaterials ◽

10.3390/nano11071651 ◽

2021 ◽

Vol 11 (7) ◽

pp. 1651

Author(s):

Cristina Arqueros ◽

Félix Zamora ◽

Carmen Montoro

Keyword(s):

Water Treatment ◽

Resource Scarcity ◽

Covalent Organic Frameworks ◽

Design Strategies ◽

Free Standing ◽

Water And Wastewater Treatment ◽

Design And Synthesis ◽

Water Detection ◽

Wide Range ◽

Quality Water

Global population growth and water resource scarcity are significant social problems currently being studied by many researchers focusing on finding new materials for water treatment. The aim is to obtain quality water suitable for drinking and industrial consumption. In this sense, an emergent class of crystalline porous materials known as Covalent-Organic Frameworks (COFs) offers a wide range of possibilities since their structures can be designed on demand for specific applications. Indeed, in the last decade, many efforts have been made for their use in water treatment. This perspective article aims to overview the state-of-the-art COFs collecting the most recent results in the field for water detection of pollutants and water treatment. After the introduction, where we overview the classical design strategies on COF design and synthesis for obtaining chemically stable COFs, we summarize the different experimental methodologies used for COFs processing in the form of supported and free-standing membranes and colloids. Finally, we describe the use of COFs in processes involving the detection of pollutants in water and wastewater treatment, such as the capture of organic compounds, heavy metals, and dyes, the degradation of organic pollutants, as well as in desalination processes. Finally, we provide a perspective on the field and the potential technological use of these novel materials.

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Effect of the Dispersion of Nanosized Carbides (NbC - TaC) in the Sintered Microstructure of the Stainless Steel 316L

Materials Science Forum ◽

10.4028/www.scientific.net/msf.591-593.294 ◽

2008 ◽

Vol 591-593 ◽

pp. 294-298

Author(s):

Uilame Umbelino Gomes ◽

L.A. Oliveira ◽

S.R.S. Soares ◽

M. Furukava ◽

C.P. Souza

Keyword(s):

Stainless Steel ◽

Automotive Industry ◽

Sintering Temperature ◽

Vacuum Furnace ◽

Nanosized Particles ◽

Stainless Steel 316L ◽

Wide Range ◽

Sintered Stainless Steel ◽

20 Nm ◽

Hardness Values

Sintered stainless steel has a wide range of applications mainly in the automotive industry. Properties such as wear resistance, density and hardness can be improved by addition of nanosized particles of refractory carbides. The present study compares the behavior of the sintering and hardness of stainless steel samples reinforced with NbC or TaC (particles size less than 20 nm) synthesized at UFRN. The main aim of this work was to identify the effect of the particle size and dispersion of different refractory carbides in the hardness and sintered microstructure. The samples were sintered in a vacuum furnace. The heating rate, sintering temperature and times were 20°C/min, 1290°C and 30, 60 min respectively. We have been able to produce compacts with a relative density among 95.0%. The hardness values obtained were 140 HV for the reinforced sample and 76 HV for the sample without reinforcement.

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Characteristics of air entrainment during dynamic wetting failure along a planar substrate

Journal of Fluid Mechanics ◽

10.1017/jfm.2014.110 ◽

2014 ◽

Vol 747 ◽

pp. 119-140 ◽

Cited By ~ 24

Author(s):

E. Vandre ◽

M. S. Carvalho ◽

S. Kumar

Keyword(s):

High Speed ◽

Water Solution ◽

Air Entrainment ◽

Dynamic Contact ◽

Operating Conditions ◽

Dynamic Wetting ◽

Glycerol Water ◽

Planar Substrate ◽

Wide Range ◽

Stationary Plate

AbstractCharacteristic substrate speeds and meniscus shapes associated with the onset of air entrainment are studied during dynamic wetting failure along a planar substrate. Using high-speed video, the behaviour of the dynamic contact line (DCL) is recorded as a tape substrate is drawn through a bath of a glycerol/water solution. Air entrainment is identified by triangular air films that elongate from the DCL above some critical substrate speed. Meniscus confinement within a narrow gap between the substrate and a stationary plate is shown to delay air entrainment to higher speeds for a wide range of liquid viscosities, expanding upon the findings of Vandre, Carvalho & Kumar (J. Fluid Mech., vol. 707, 2012, pp. 496–520). A pressurized liquid reservoir controls the meniscus position within the confinement gap. It is found that liquid pressurization further postpones air entrainment when the meniscus is located near a sharp corner along the stationary plate. Meniscus shapes recorded near the DCL demonstrate that operating conditions influence the size of entrained air films, with smaller films appearing in the more viscous solutions. Regardless of size, air films become unstable to thickness perturbations and ultimately rupture, leading to the entrainment of air bubbles. Recorded critical speeds and air-film sizes compare well to predictions from a hydrodynamic model for dynamic wetting failure, suggesting that strong air stresses near the DCL trigger the onset of air entrainment.

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Porosity Control of Thermally Sprayed Ceramic Deposits

Thermal Spray 1998: Proceedings from the International Thermal Spray Conference ◽

10.31399/asm.cp.itsc1998p1299 ◽

1998 ◽

Author(s):

P. Chraska ◽

V. Brozek ◽

B.J. Kolman ◽

J. Ilavsky ◽

K. Neufuss ◽

...

Keyword(s):

Gas Permeability ◽

Water Immersion ◽

Thermal Spraying ◽

Spray Parameters ◽

Post Processing ◽

Free Standing ◽

Spray Process ◽

Wide Range ◽

Controlled Porosity ◽

Selection Of

Abstract Porosity regulates the deposit's properties and therefore methods for its control are of a vital industrial importance. Thermal spraying can produce deposits in a wide range of porosities by selection of a spray process itself, by selection of spray parameters, feedstock size and chemistry, etc. Manufacturing of deposits with controlled porosity may be difficult if the selection of spray processes and materials is limited. Special methods of deposition or/and subsequent post processing may be therefore necessary. These methods are studied in the presented work. All spraying was done with the water-stabilized plasma (WSP®) system PAL 160. Thick deposits and free-standing parts were sprayed from alumina, zircon, metal Al and Ni powders and their combinations. Porosity was characterized by number of techniques such as gas permeability, water immersion, MIP, SEM and SANS. Mechanical properties were characterized by the Young's modulus. Special methods of deposition, such as spraying of mixtures of ceramics and metals were successfully used. Either sandwiched-structures with alternating layers of ceramics and metals were sprayed (for the sealing purpose) or mechanical mixtures of ceramic and metallic feedstock were sprayed. Several post-processing methods were used to change porosity volumes or other materials characteristics. To increase the porosity the metallic phases were subsequently removed by leaching or by annealing at temperatures above the melting point of metal. A number of sealing materials (organic and inorganic) were used to seal the pores by infiltration at ambient or higher pressures. The results show, that significant changes of porosity volume and, especially, of the gas permeability are possible. Another tested method was annealing/calcination of deposits, which resulted in an increase or decrease of porosity, depending on deposit's chemistry and annealing conditions. Results show that all used post processings are capable of significant changes of deposit microstructure and that they may be successfully applied in practice.

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Influence of thermal treatment and combustible additives on properties of Latvian clay ceramics pellets

Processing and Application of Ceramics ◽

10.2298/pac1304175d ◽

2013 ◽

Vol 7 (4) ◽

pp. 175-180 ◽

Cited By ~ 3

Author(s):

Liga Dabare ◽

Ruta Svinka

Keyword(s):

Surface Area ◽

Ph Value ◽

Water Solution ◽

Porous Ceramic ◽

Mercury Porosimetry ◽

Environmental Application ◽

Wide Range ◽

Different Temperatures ◽

Ph Level ◽

Clay Ceramics

Porous ceramic pellets for possible environmental application were produced from different Latvian clays by sintering at different temperatures. Their characteristics and influence of additives were analysed using X-ray diffraction, mercury porosimetry and BET tests. The obtained ceramic pellets from calcareous clays after immersion in distilled water change its pH value, which affects their capability to adsorb ions or molecules on the surface. The sorption capabilities are dependent on the pH level of water solution, composition of clays, and used adsorbate. Porosity of the produced pellets is mostly within range from 15 to 25 % throughout all sintering temperatures with a slight decrease at 1050 ?C. The specific surface area has a wide range up to 30 m2/g. The highest surface area has pellets sintered at lower temperatures. The adsorption capability of pellets was evaluated using water solutions with different ions. The most promising results were obtained with iodine sorption. For most pellets the sorption capacity was 12.7 mg/g, although for the pellets sintered at 1050 ?C it was lower.

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Experimental investigation of the parameters of water solution purposes by ceramic, coal filters and reverse-osmotic module

Кераміка наука і життя ◽

10.26909/csl.3.2019.4 ◽

2019 ◽

pp. 30-33

Author(s):

S.V. Gulienko

Keyword(s):

Reverse Osmosis ◽

Water Solution ◽

Ceramic Filter ◽

Main Process ◽

Working Pressure ◽

Ceramic Filters ◽

Quality Of Water ◽

Urgent Task ◽

Wide Range ◽

Series Of Experiments

The urgent task is to research in detail the possibilities of operation of the reverse osmosis membrane in the conditions of changing various parameters, which include, first of all, the working pressure, the initial concentration of the cleaning solutions, as well as the working conditions and the complete set of cleaning stands with auxiliary filters: mechanical, ceramic and carbon, which improves the quality of water and increases the life of high-value reverse osmosis modules. Particular attention was paid in this series of experiments to the role of ceramic filters, since in the previous series of experiments the concentration of the solution did not change both after mechanical and after carbon filters. Therefore, it was decided to modernize the stand and use a ceramic filter in the flow chart. In this work the detailed scheme of bench-scale setup with using of ceramic and carbon filters and also reverse-osmosis module is represented. The experimental reseaches of purification of NaCl water solutions were carried out in wide range of concentrations (0,2∙10-3…6,5 g/l) and working pressures (0,2…0,65 MPa). The comparative characteristics of main process parameters with and without ceramic filter are represented. The experiments were carried out on a laboratory stand for complex purification of aqueous solutions by microfiltration, adsorption and reverse osmosis using the following process steps carried out in the respective apparatus.

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Single Crystal CVD Diamond Nuclear Detectors

Advances in Science and Technology ◽

10.4028/www.scientific.net/ast.48.103 ◽

2006 ◽

Vol 48 ◽

pp. 103-112 ◽

Cited By ~ 2

Author(s):

Claudio Manfredotti

Keyword(s):

Single Crystal ◽

Time Derivative ◽

Diamond Films ◽

Radiation Detectors ◽

Cvd Diamond ◽

High Energy ◽

Neutron Spectrometry ◽

Free Standing ◽

Wide Range ◽

Nuclear Detectors

CVD diamond films have reached in recent years superlative improvements in their “ detector grade “ quality, with a time derivative which was never registered for other similar frontier materials. The basic properties of high quality CVD diamond films make them very interesting for a wide range of radiation detectors : they provide fast signals with very low leakage currents, they are very radiation resistant, they have excellent thermal properties and they can be manufactured as free-standing detectors. The recent availability of single crystal CVD diamond samples of extreme good quality, suitable thickness and surface area has opened new application fields in nuclear detection and dosimetry, such as, for instance, hadron therapy and neutron spectrometry in fusion reactors. At the same time, strip and pixel detectors of unprecedented performances have been successfully realized and exploited in the framework of high energy physics experiments. The paper will review the more recent history of CVD diamond nuclear detectors with respect to material quality, with a particular emphasis on epitaxial single crystals diamond, and the achievements in terms of applications in some different fields.

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Noble Metal Composite Porous Silk Fibroin Aerogel Fibers

Materials ◽

10.3390/ma12060894 ◽

2019 ◽

Vol 12 (6) ◽

pp. 894 ◽

Cited By ~ 4

Author(s):

Alexander Mitropoulos ◽

F. Burpo ◽

Chi Nguyen ◽

Enoch Nagelli ◽

Madeline Ryu ◽

...

Keyword(s):

Noble Metal ◽

Silk Fibroin ◽

Noble Metals ◽

Metal Salt ◽

Supercritical Drying ◽

Noble Metal Nanoparticles ◽

Metal Composite ◽

Composite Aerogel ◽

Wide Range ◽

Composite Aerogels

Nobel metal composite aerogel fibers made from flexible and porous biopolymers offer a wide range of applications, such as in catalysis and sensing, by functionalizing the nanostructure. However, producing these composite aerogels in a defined shape is challenging for many protein-based biopolymers, especially ones that are not fibrous proteins. Here, we present the synthesis of silk fibroin composite aerogel fibers up to 2 cm in length and a diameter of ~300 μm decorated with noble metal nanoparticles. Lyophilized silk fibroin dissolved in hexafluoro-2-propanol (HFIP) was cast in silicon tubes and physically crosslinked with ethanol to produce porous silk gels. Composite silk aerogel fibers with noble metals were created by equilibrating the gels in noble metal salt solutions reduced with sodium borohydride, followed by supercritical drying. These porous aerogel fibers provide a platform for incorporating noble metals into silk fibroin materials, while also providing a new method to produce porous silk fibers. Noble metal silk aerogel fibers can be used for biological sensing and energy storage applications.

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Long-range exciton diffusion in molecular non-fullerene acceptors

Nature Communications ◽

10.1038/s41467-020-19029-9 ◽

2020 ◽

Vol 11 (1) ◽

Cited By ~ 3

Author(s):

Yuliar Firdaus ◽

Vincent M. Le Corre ◽

Safakath Karuthedath ◽

Wenlan Liu ◽

Anastasia Markina ◽

...

Keyword(s):

Organic Semiconductors ◽

Diffusion Length ◽

Crystal Packing ◽

Maximum Size ◽

Exciton Diffusion ◽

Exciton Diffusion Length ◽

Donor And Acceptor ◽

Wide Range ◽

20 Nm ◽

End Group

Abstract The short exciton diffusion length associated with most classical organic semiconductors used in organic photovoltaics (5-20 nm) imposes severe limits on the maximum size of the donor and acceptor domains within the photoactive layer of the cell. Identifying materials that are able to transport excitons over longer distances can help advancing our understanding and lead to solar cells with higher efficiency. Here, we measure the exciton diffusion length in a wide range of nonfullerene acceptor molecules using two different experimental techniques based on photocurrent and ultrafast spectroscopy measurements. The acceptors exhibit balanced ambipolar charge transport and surprisingly long exciton diffusion lengths in the range of 20 to 47 nm. With the aid of quantum-chemical calculations, we are able to rationalize the exciton dynamics and draw basic chemical design rules, particularly on the importance of the end-group substituent on the crystal packing of nonfullerene acceptors.

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