Synthesis and Characterization of Silica Aerogel Materials Doped with TiO2 Powder for Thermal Insulation

2016 ◽  
Vol 723 ◽  
pp. 492-496
Author(s):  
Guang Wu Liu ◽  
Yan Gang Liu
Keyword(s):  
Surface Modification ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Silica Aerogel ◽  
High Performance ◽  
Silica Aerogels ◽  
Molar Ratio ◽  
Composite Aerogel ◽  
Thermal Conductivities

Super insulation and hydrophobic silica-based aerogels doped with TiO2 powder (8wt %) were successfully synthesized by using cost effective processing from Tetraeth oxysilane (TEOS). After aging and washing of wet gel, surface modification were modified using trimethylchlorosilane (TMCS) via one-step solvent exchange and surface modification. And the proper molar ratio of TMCS to pore water is 0.02. The microstructure and morphology of the ultralow density silica aerogels were characterized by the specific surface area, SBET, SEM, and the pore size distribution techniques. From the results, the obtained aerogel doped with TiO2 powder exhibited excellent physical properties with less than 10% volume shrinkage, extremely high specific surface area (652 m2/g) and super hydrophobicity (contact angle of~145°). It should be noted that TiO2 powders are physically embedded by SiO2 aerogel, and there is an obvious Ti–O–Ti and Si–O–Si bonding group based on structural analysis. The thermal properties of silica aerogel were determined using the Hot Disk device, composite aerogel exhibited thermal conductivities of 0.0426 W/m·K at 700°C, TiO2 powders effectively suppressed the intensified thermal radiations at high temperatures to achieve ultralow thermal conductivities. These results have important implications for designing novel structure of porous materials of high performance for silica aerogels.

Preparation and Characterization of Ultralow Density Silica Aerogels by Acetonitrile Supercritical Drying

2012 ◽  
Vol 519 ◽  
pp. 83-86 ◽  
Author(s):  
Guang Wu Liu ◽  
Xing Yuan Ni ◽  
Bin Zhou ◽  
Qiu Jie Yu
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Silica Aerogel ◽  
Sol Gel ◽  
Supercritical Drying ◽  
Silica Aerogels ◽  
High Specific Surface Area ◽  
Molar Ratio ◽  
Sol Gel Process

This paper deals with the synthesis of ultralow density silica aerogels using tetramethyl orthosilicate (TMOS) as the precursor via sol-gel process followed by supercritical drying using acetonitrile solvent extraction. Ultralow density silica aerogels with 6 mg/cc of density was made for the molar ratio by this method. The microstructure and morphology of the ultralow density silica aerogels was characterized by the specific surface area, SBET, SEM, and the pore size distribution techniques. The results show that the ultralow density silica aerogel has the high specific surface area of 812m2/g. Thermal conductivities at desired temperatures were analyzed by the transient plane heat source method. Thermal conductivity coefficients of silica aerogel monoliths changed from 0.024 to 0.043W/ (m K) as temperature increased to 400°C, revealed an excellent heat insulation effect during thermal process.

The Monolithic Silica Aerogel Derived from MTMS/TEOS

2013 ◽  
Vol 364 ◽  
pp. 631-634
Author(s):  
Yu Xi Yu ◽  
Yong Chen
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Silica Aerogel ◽  
Sol Gel ◽  
Supercritical Drying ◽  
Silica Aerogels ◽  
Synthesis And Characterization ◽  
Sol Gel Process

The experimental results on the synthesis and characterization of tetraethoxysilane (TEOS)/ methyltrimethoxysilane (MTMS)-based silica aerogels using two step sol-gel process via supercritical drying, are described. The obtained TEOS/MTMS-based aerogel showed properties of 0.1g/cm3 density, 95.5% porosity and 1070 m2/g specific surface area.

Functional Silica Aerogels with High Specific Surface Area: Influence of Preparation Conditions on Structure Properties

2009 ◽  
Vol 79-82 ◽  
pp. 2039-2042
Author(s):  
Li Ye ◽  
Wei Jian Han ◽  
Zhi Hong Ji ◽  
Ji Dong Hu ◽  
Tong Zhao
Keyword(s):  
Specific Surface ◽  
Bulk Density ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Silica Aerogels ◽  
Pore Distribution ◽  
Nano Particles ◽  
Molar Ratio ◽  
Electron Microscopic

A series monolithic silica aerogels modified by amino-substituted organic groups were synthesized by sol-gel processing of tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) mixtures, followed by drying of the wet gels with supercritical carbon dioxide (SCCO2). The molar ratios of EtOH/TEOS and DMF/ (TEOS+APTES) were fixed at 5 and 0.4, respectively, and APTES/TEOS ratio was varied between 1:9 and 3:7. HCl was added to obtain a narrow pore distribution, and the ratio of HCl/ (TEOS+APTES) was varied between 0 and 0.004. When APTES/TEOS ratio was kept at constant, gelling of the precursor mixtures was accelerated with an increasing ratio of HCl/ (TEOS+APTES). The physical properties of the aerogels have been investigated in detail by the bulk density, porosity, nitrogen sorption measurements and scanning electron microscopic (SEM). The results showed that adding HCl did increase the specific surface areas of the aerogels and make the aerogels have narrow pore distributions, but also resulted in some increase in bulk densities and decrease in porosities. The bulk density of the aerogels was 0.13-0.32 g/cm3, the corresponding porosity between 80% and 92%. Microscopically, the framework of the functional aerogels consists of spherical secondary nano-particles, which stack into grape-like aggregate and interconnect in different directions into a network. The specific surface area of the aerogels were in the range of 362-1044 m2/g, and uniform pore distribution aerogels were obtained when the molar ratio of APTES/ (TEOS+APTES)/HCl at 1/10/0.002 and 1/10/0.004.

KCl-assisted activation: Moringa oleifera branch-derived porous carbon for high performance supercapacitor

2021 ◽  
Vol 45 (12) ◽  
pp. 5712-5719
Author(s):  
Yongxiang Zhang ◽  
Peifeng Yu ◽  
Mingtao Zheng ◽  
Yong Xiao ◽  
Hang Hu ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Porous Carbon ◽  
High Performance ◽  
Moringa Oleifera ◽  
High Specific Surface Area ◽  
Porous Carbons

Porous carbons with a high specific surface area (2314–3470 m2 g−1) are prepared via a novel KCl-assisted activation strategy for high-performance supercapacitor.

Three-dimensional graphene encapsulated hollow CoSe2-SnSe2 nanoboxes for high performance asymmetric supercapacitors

2022 ◽  
Author(s):  
Kainan Li ◽  
Ke Zheng ◽  
Zhifang Zhang ◽  
Kuan Li ◽  
Ziyao Bian ◽  
...  
Keyword(s):  
Electrochemical Performance ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Active Sites ◽  
Specific Capacity ◽  
Three Dimensional ◽  
Hollow Structure ◽  
Large Specific Surface Area ◽  
Composite Aerogel

Abstract Construction of metal selenides with a large specific surface area and a hollow structure is one of the effective methods to improve the electrochemical performance of supercapacitors. However, the nano-material easily agglomerates due to the lack of support, resulting in the loss of electrochemical performance. Herein, we successfully design a three-dimensional graphene (3DG) encapsulation-protected hollow nanoboxes (CoSe2-SnSe2) composite aerogel (3DG/CoSe2-SnSe2) via a co-precipitation method coupled with self-assembly route, followed by a high temperature selenidation strategy. The obtained aerogel possesses porous 3DG conductive network, large specific surface area and plenty of reactive active sites. It could be used as a flexible and binder-free electrode after a facile mechanical compression process, which provided a high specific capacitance of 460 F g-1 at 0.5 A g-1, good rate capability of 212.7 F g-1 at 10 A g-1, and excellent cycle stability due to the fast electron/ion transfer and electrolyte diffusion. With the as-prepared 3DG/CoSe2-SnSe2 as positive electrodes and the AC (activated carbon) as negative electrodes, an asymmetric supercapacitor (3DG/CoSe2-SnSe2//AC) was fabricated, which delivered a high specific capacity of 38 F g-1 at 1A g-1 and an energy density of 11.89 W h kg-1 at 749.9 W kg-1, as well as a capacitance retention of 91.1% after 3000 cycles. This work provides a new method for preparing electrode material.

The Influence of Fe/Al Molar Ratio on Microreactor-Based Catalyst Preparation and Carbon Nanotube Preparation

2021 ◽  
Vol 1036 ◽  
pp. 130-136
Author(s):  
Ting Qun Tan ◽  
Lei Geng ◽  
Yan Lin ◽  
Yan He
Keyword(s):  
Carbon Nanotubes ◽  
Catalytic Activity ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Small Diameter ◽  
High Specific Surface Area ◽  
Detection Methods ◽  
Molar Ratio ◽  
High Catalytic Activity

In order to prepare carbon nanotubes with high specific surface area, small diameter, low resistivity, high purity and high catalytic activity, the Fe-Mo/Al2O3 catalyst was prepared based on the microreactor. The influence of different Fe/Al molar ratios on the catalyst and the carbon nanotubes prepared was studied through BET, SEM, TEM and other detection methods. Studies have shown that the pore structure of the catalyst is dominated by slit pores at a lower Fe/Al molar ratio. The catalytic activity is the highest when the Fe/Al molar ratio is 1:1, reaching 74.1%. When the Fe/Al molar ratio is 1:2, the catalyst has a higher specific surface area, the maximum pore size is 8.63 nm, and the four-probe resistivity and ash content of the corresponding carbon nanotubes are the lowest. The higher the proportion of aluminum, the higher the specific surface area of the catalyst and the carbon nanotubes, and the finer the diameter of the carbon nanotubes, which gradually tends to relax. The results show that when the Fe/Al molar ratio is 1:2, although the catalytic activity of the catalyst is not the highest, the carbon nanotubes prepared have the best performance.

scholarly journals Time-Resolved X-ray Operando Observations of Lithiation Gradients across the Cathode Matrix and Individual Oxide Particles during Fast Cycling of a Li-Ion Cell

2021 ◽  
Author(s):  
Tianlong Zheng ◽  
Jing He ◽  
Pingwei Cai ◽  
Xi Liu ◽  
Duojie Wu ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
High Performance ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Carbon Paper ◽  
Free Energy Barrier ◽  
Active Components

Abstract Self-supporting three-dimensional (3D) transition metal electrodes have been considered for designing high-performance non-noble metal oxygen evolution reaction (OER) catalysts owing to their advantages such as binder-free, good mass transfer, and large specific surface area. However, the poor conductivity of ((oxy)hydr)oxides and the difficulty in adjusting their electronic structure limit their application. As an alternative strategy, instead of constituting the array electrode by the active components themselves, we herein report 3D Co(OH)2@MnO2 heterostructure decorated carbon nanoarrays grown directly on carbon paper (Co(OH)2@MnO2-CNAs). This unique structure can not only enhance electrical conductivity but also provide a larger specific surface area, and facilitate electrolyte diffusion and ion transport. The core-shell heterostructured Co(OH)2@MnO2 formed via incorporation with MnO2 facilitates the transition of CoII to CoIII in Co(OH)2 and it increases the storage of oxidative charge in the catalyst, leading to an OER activity with benchmark RuO2 and good stability. Density functional theory calculations suggest that the improved OER performance can be attributed to the formation of the heterojunction structure, resulting in the modulation of the electronic structure of Co atoms and the reduction of the free energy barrier of the rate-determining step for the OER.

In-situ controlled synthesis of NiFe MOF materials with excellent electrocatalytic performances for water splitting

2021 ◽  
Vol 14 (02) ◽  
pp. 2151011
Author(s):  
Jingwen Jia ◽  
Longfu Wei ◽  
Ziting Guo ◽  
Fang Li ◽  
Changlin Yu ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Water Splitting ◽  
Specific Surface Area ◽  
High Performance ◽  
Alkaline Condition ◽  
High Porosity ◽  
Large Specific Surface Area ◽  
Electrocatalytic Performance

Metal–organic frameworks (MOFs) are the electrocatalytic materials with large specific surface area, high porosity, controllable structure and monodisperse active center, which is a promising candidate for the application of electrochemical energy conversion. However, the electrocatalytic performance of pure MOFs is seriously limited its poor conductivity and stability. In this work, high-performance electrocatalyst was fabricated through combining NiFe/MOF on nickel foam (NF) via in-situ growth strategy. Through rational control of the time and ratio in reaction precursors, we realized the effective manipulation of the growth behavior, and further investigated the electrocatalytic performance in water splitting. The catalyst presented excellent electrocatalytic performance for water splitting, with low overpotential of 260 mV in alkaline condition at a current density of 50 mA[Formula: see text], which is benefited from the large specific surface area and active sites. This study demonstrates that the rational design of NiFe MOF/NF plays a significant role in high-performance electrocatalyst.

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