scholarly journals Fractal Structure in Silica and Composites Aerogels

Gels ◽  
2020 ◽  
Vol 7 (1) ◽  
pp. 1
Author(s):  
Thierry Woignier ◽  
Juan Primera ◽  
Adil Alaoui ◽  
Philippe Dieudonne ◽  
Laurent Duffours ◽  
...  
Keyword(s):  
Fractal Structure ◽  
High Surface ◽  
High Surface Area ◽  
Silica Aerogels ◽  
High Porosity ◽  
Material Density ◽  
X Ray ◽  
Synthesis Conditions ◽  
Fractal Characteristics ◽  
Synthesis Procedure

Silica aerogels are known to be materials with exceptional characteristics, such as ultra-low density, high surface area, high porosity, high adsorption, and low-thermal conductivity. In addition, these unique properties are mainly related to their specific processing. Depending on the aerogel synthesis procedure, the aerogels texture can be tailored with meso and/or macroporosity. Fractal geometry has been observed and used to describe silica aerogels at nanoscales in certain conditions. In this review paper, we describe the fractal structure of silica aerogels that can develop depending on the synthesis conditions. X-ray and neutron scattering measurements allow to show that silica aerogels can exhibit a fractal structure over one or even more than two orders of magnitude in length. The fractal dimension does not depend directly on the material density but can vary with the synthesis conditions. It ranges typically between 1.6 and 2.4. The effect of the introduction of silica particles or of further thermal treatment or compression of the silica aerogels on their microstructure and their fractal characteristics is also resumed.

scholarly journals Preparation of modified paints with nano-structured additives and its potential applications

2020 ◽  
Vol 10 ◽  
pp. 184798042090918
Author(s):  
Ricardo Solano ◽  
David Patiño-Ruiz ◽  
Adriana Herrera
Keyword(s):  
Electron Microscopy ◽  
Zno Nanoparticles ◽  
Uv Light ◽  
High Surface ◽  
High Surface Area ◽  
Antibacterial Properties ◽  
Normal Function ◽  
High Porosity ◽  
X Ray ◽  
Self Cleaning

Recently, an increase in the production of intelligent nanomaterials has been reported for the application of solid surface coating. These nanomaterials provide a wide number of functionalities such as anticorrosive, antibacterial, and self-cleaning properties. Hence, titanium dioxide (TiO2) and zinc oxide (ZnO) nanoparticles were synthesized using a green chemistry approach. These nanoparticles were fully characterized by scanning electron microscopy, energy-dispersive X-ray, high-resolution transmission electron microscopy, X-ray diffraction, ultraviolet (UV)–visible spectroscopy, Brunauer–Emmett–Teller test, and nitrogen adsorption–desorption isotherm. Then, a commercial enamel-type paint was modified by using different concentrations (2, 3.5, and 5 w/v%) of nanoparticles. These nanofilled paints were then brushed onto the surface of different types of materials such as carbon steel sheets, wood sheets, and aluminum disks. Anticorrosive, self-cleaning, and antibacterial properties of the nanofilled paints were evaluated, with the aim to determine the capability for this application. According to the characterization results, TiO2 and ZnO nanoparticles exhibited similar physicochemical properties compared to those synthesized using traditional methods. The anticorrosion results revealed that nanofilled paints provide a barrier using low concentrations of nanoparticles, due to the decrease of agglomerates on the surface avoiding the presence of high porosity. In the case of self-cleaning, a proposed mechanism of degradation demonstrated that the presence of both nanoparticles in the paint provided high degradation of methylene blue due to the high surface area offered by the nanoparticles. On the other hand, antibacterial activity under UV light was observed only for ZnO nanoparticles, which may be related to the diffusion of nanoparticles into the cell membrane of the bacteria, affecting the normal function. These results showed to be promising for the modification of paints with TiO2 and ZnO nanoparticles, and the application on solid surfaces for the construction, and even in textile fields.

One-Step Processing to Fabricate Highly Transparent Superhydrophobic Surface via Granuliform Silica Aerogels

2014 ◽  
Vol 936 ◽  
pp. 1042-1046 ◽  
Author(s):  
Bi Xu ◽  
Jing Jing Ge ◽  
Zai Sheng Cai
Keyword(s):  
Superhydrophobic Surface ◽  
High Surface ◽  
High Surface Area ◽  
Silica Aerogels ◽  
Silica Xerogel ◽  
Methyl Groups ◽  
High Porosity ◽  
Porous Network ◽  
Glass Slides ◽  
One Step

A simple, versatile method has been developed to fabricate the transparent superhydrophobic surface via granuliform silica aerogels. The effect of ageing on the wettability, microstructure morphology and chemical structure of the dried gels has been investigated. Silica aerogel (dried alcogel with ageing) has a 3D porous network exhibiting the high surface area and pore volume. In comparison, large aggregates of silica nanoparticles exist within the backbone of the silica xerogel (dried alcogel without ageing). Both the aerogel and xerogel exhibit analogous chemical composition with abundant of methyl groups on the surface. The rough surface due to the high porosity and low surface energy provided by the methyl groups of aerogel contribute to the superhydrophobicity. Meanwhile, glass slides coated with aerogel film is highly transparent because the roughness created by the aerogel film is limited.

X-ray and FIB Tomography of Extremely High Surface Area Nanostructured Hollow Fiber Membranes

2012 ◽  
Vol 1421 ◽  
Author(s):  
Amy J. Grano ◽  
Franchessa M. Sayler ◽  
Amber Genau ◽  
Keana L. Graves ◽  
Brian M. Patterson ◽  
...  
Keyword(s):  
High Surface ◽  
High Surface Area ◽  
Porous Silica ◽  
Porous Metal ◽  
Sample Volume ◽  
Ionic Conductors ◽  
Hierarchically Porous ◽  
X Ray ◽  
Synthesis Conditions ◽  
Wide Range

ABSTRACTHierarchically porous materials are of interest in a wide range of applications. If the materials are electronic, or ionic conductors, such materials are of interest as electrodes for use in fuel cells. Using hierarchically porous silica as templates, we have demonstrated the formation of hierarchically porous metal and metal oxide structures. Through the control of the synthesis conditions, we have produced partial replicas ca. 1 cubic centimeter in volume, in which two macroporous networks are separated by a nanoporous membrane. The macroporous network in the silica template is known to be bicontinuous. Our underlying model predicts that the second, induced, macroporous network should be similarly bicontinuous.Micrometer resolution X-ray tomography of the whole sample confirms that the synthesis produces one bicontinuous macroporous network, and is consistent with the existence of a second set of macropores. Preliminary experiments were carried out using FIB/SEM serial tomography to image the second macropore network, however, the length scale of the structures is such that this approach it is unable to firmly establish that the second macropore network is bicontinuous throughout the entire sample volume.

Synthesis Procedure and Industrial Applications of NaY Zeolite for Various Processes: A Review

2020 ◽  
Vol 17 (7) ◽  
pp. 795-804
Author(s):  
Mahjoobeh Hajitabar Firouzjaee ◽  
Majid Taghizadeh
Keyword(s):  
Alkali Treatment ◽  
High Surface ◽  
High Surface Area ◽  
Industrial Applications ◽  
Exchange Capacity ◽  
High Porosity ◽  
Ion Exchange Capacity ◽  
Y Zeolites ◽  
Natural Gas Dehydration ◽  
Synthesis Procedure

Faujasite Y zeolites, due to their outstanding properties, have numerous applications in the chemical industries like petroleum refining, adsorption, FCC, petrochemical, aromatic alkylation, natural gas dehydration, separation, and environmental protection. The astonishing properties include high surface area, high porosity, high thermal stability and large ion-exchange capacity. In this review study, a summary of different synthesis techniques of this type of zeolite has been addressed. Different kinds of techniques like seeding, free template, organic template, increasing the alkali treatment and temperature control methods are described. Subsequently, because of its important role as a catalyst for different processes, the application of this zeolite was reviewed for different chemical processes.

scholarly journals Synthesis, characterization, and reactivity of tungsten oxynitride

1998 ◽  
Vol 13 (8) ◽  
pp. 2321-2327 ◽  
Author(s):  
Toby E. Lucy ◽  
Todd P. St. Clair ◽  
S. Ted Oyama
Keyword(s):  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
X Ray Diffraction ◽  
Heating Rates ◽  
Continuous Transformation ◽  
X Ray ◽  
Synthesis Conditions ◽  
Temperature Programmed ◽  
Temperature Programmed Reaction

High surface area tungsten oxynitride has been prepared by the temperature programmed reaction (TPR) of WO3 with NH3. All samples were characterized by x-ray diffraction (XRD), nitrogen physisorption, CO chemisorption, and elemental analysis. Samples were prepared at different heating rates (β), and a Redhead analysis yielded an activation energy for nitridation of 109 kJ mol−1. A heating rate of 0.016 K s−1 gave optimal synthesis conditions. Solid state intermediates were studied by interrupting the temperature program at various stages. No distinct suboxide phases were found using XRD. The nitridation step was determined to be a continuous transformation from oxide to oxynitride. Surface area, CO uptake, and nitrogen weight % were all found to increase as the reaction progressed. Reactivity experiments showed reasonable hydrodeoxygenation (HDO) and hydrodenitrogenation (HDN) activity, but little hydrogenation (HYD) or hydrodesulfurization (HDS) activity.

Synthesis and Characterization of Silica-Alumina Supported Ca and Ni Catalyst for Deoxygenation of Vegetable Oil into Diesel

2016 ◽  
Vol 840 ◽  
pp. 353-358 ◽  
Author(s):  
Nurul Aiskin Mijan ◽  
Hwei Voon Lee ◽  
Abdulkareem Ghassan Alsultan ◽  
Yun Hin Taufiq-Yap
Keyword(s):  
Vegetable Oil ◽  
Catalyst Activity ◽  
High Surface ◽  
High Surface Area ◽  
Ni Catalyst ◽  
High Porosity ◽  
X Ray ◽  
Mesoporous Support ◽  
Silica Alumina ◽  
Temperature Programme Desorption

Developing an environmentally friendly and high-quality of fuel from vegetable oil (triglycerides) have attracted a great attention among the researches. Deoxygenation reaction using Ca-based catalyst is a potentially promising element for removing an oxygen species from organic compounds and converting the molecule to hydrocarbon. Addition of transition metal in the catalysis synthesis studies not only could enhance the properties of the catalyst but also could tune the selectivity toward desired product. Cooperation of mesoporous support such as silica alumina (SA) exhibit unique and excellent properties (high surface area, high porosity) which simultaneously could increase the catalyst activity. In the present studies, a set of bifunctional acid-base supported on the highly mesoporous SA doped with Ca and Ni were synthesized. The Ca (NO)3 and Ni (NO)3 were impregnated on the mesoporous SA support and were calcined at 500 °C for 2 h in order to activate the synthesized catalyst. The physicochemical properties of the catalyst were characterized by X-Ray fluorescence spectroscopy (XRF), X-Ray diffraction spectroscopy (XRD), temperature programme desorption carbon dioxide (TPD-CO2) and temperature programme desorption ammonia (TPD-NH3) and scanning electron microscopy (SEM).

scholarly journals Non-Thermal Plasma-Modified Ru-Sn-Ti Catalyst for Chlorinated Volatile Organic Compound Degradation

Catalysts ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1456
Author(s):  
Yujie Fu ◽  
You Zhang ◽  
Qi Xin ◽  
Zhong Zheng ◽  
Yu Zhang ◽  
...  
Keyword(s):  
Plasma Treatment ◽  
Photoelectron Spectroscopy ◽  
High Surface ◽  
High Surface Area ◽  
Surface Oxidation ◽  
Treatment Method ◽  
X Ray ◽  
Chlorinated Volatile Organic Compounds ◽  
Volatile Organic ◽  
Doped Titania

Chlorinated volatile organic compounds (CVOCs) are vital environmental concerns due to their low biodegradability and long-term persistence. Catalytic combustion technology is one of the more commonly used technologies for the treatment of CVOCs. Catalysts with high low-temperature activity, superior selectivity of non-toxic products, and resistance to chlorine poisoning are desirable. Here we adopted a plasma treatment method to synthesize a tin-doped titania loaded with ruthenium dioxide (RuO2) catalyst, possessing enhanced activity (T90%, the temperature at which 90% of dichloromethane (DCM) is decomposed, is 262 °C) compared to the catalyst prepared by the conventional calcination method. As revealed by transmission electron microscopy, X-ray diffraction, N2 adsorption, X-ray photoelectron spectroscopy, and hydrogen temperature-programmed reduction, the high surface area of the tin-doped titania catalyst and the enhanced dispersion and surface oxidation of RuO2 induced by plasma treatment were found to be the main factors determining excellent catalytic activities.

scholarly journals Attached β-cyclodextrin/γ-(2,3-epoxypropoxy) propyl trimethoxysilane to graphene oxide and its application in copper removal

2017 ◽  
Vol 75 (10) ◽  
pp. 2403-2411 ◽  
Author(s):  
Zongxue Yu ◽  
Qi Chen ◽  
Liang Lv ◽  
Yang Pan ◽  
Guangyong Zeng ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
High Surface ◽  
High Surface Area ◽  
Esterification Reaction ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cavity Structure ◽  
Optimum Ph ◽  
Exchange Adsorption ◽  
Langmuir Isotherm Model

The environmental applications of graphene oxide and β-cyclodextrin (β-CD) have attracted great attention since their first discovery. Novel nanocomposites were successfully prepared by using an esterification reaction between β-cyclodextrin/γ-(2,3-epoxypropoxy) propyl trimethoxysilane grafted graphene oxide (β-CD/GPTMS/GO). The β-CD/GPTMS/GO nanocomposites were used to remove the Cu2+ from aqueous solutions. The characteristics of β-CD/GPTMS/GO were detected by scanning electron microscopy (SEM), Fourier transform infrared, X-ray diffraction (XRD), thermogravimetric analysis (TG) and energy dispersive X-ray (EDX). The dispersibility of graphene oxide was excellent due to the addition of β-CD. The adsorption isotherms data obtained at the optimum pH 7 were fitted by Langmuir isotherm model. The excellent adsorption properties of β-CD/GPTMS/GO for Cu2+ ions could be attributed to the apolar cavity structure of β-CD, the high surface area and abundant functional groups on the surface of GO. The adsorption patterns of β-CD/GPTMS/GO were electrostatic attraction, formation of host-guest inclusion complexes and the ion exchange adsorption. The efficient adsorption of β-CD/GPTMS/GO for Cu2+ ions suggested that these novel nanocomposites may be ideal candidates for removing other cation pollutants from waste water.

Highly stable metal-organic framework UiO-66-NH2 for high-performance triboelectric nanogenerators

2021 ◽  
Author(s):  
Yong-Mei Wang ◽  
Xinxin Zhang ◽  
Dingyi Yang ◽  
Liting Wu ◽  
Jiaojiao Zhang ◽  
...  
Keyword(s):  
High Performance ◽  
Metal Organic Framework ◽  
High Surface ◽  
High Surface Area ◽  
Triboelectric Nanogenerator ◽  
High Porosity ◽  
Chemically Modified ◽  
Metal Organic ◽  
Triboelectric Nanogenerators ◽  
Organic Framework

Abstract The high porosity, controllable size, high surface area, and chemical versatility of a metal-organic framework (MOF) enable it a good material for a triboelectric nanogenerator (TENG), and some MOFs have been incorporated in the fabrication of TENGs. However, the understanding of effects of MOFs on the energy conversion of a TENG is still lacking, which inhibits the improvement of the performance of MOF-based TENGs. Here, UiO-66-NH2 MOFs were found to significantly increase the power of a TENG and the mechanism was carefully examined. The electron-withdrawing ability of Zr-based UiO-66-family MOFs was enhanced by designing the amino functionalized 1,4-terephthalic acid (1,4-BDC) as ligand. The chemically modified UiO-66-NH2 was found to increase the surface roughness and surface potential of a composite film with MOFs embedded in polydimethylsiloxane (PDMS) matrix. Thus the total charges due to the contact electrification increased significantly. The composite-based TENG was found to be very durable and its output voltage and current were 4 times and 60 times higher than that of a PDMS-based TENG. This work revealed an effective strategy to design MOFs with excellent electron-withdrawing abilities for high-performance TENGs.

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