A facile method to fabricate monolithic alumina–silica aerogels with high surface areas and good mechanical properties

AbstractHigh surface area ethyltrimethoxysilane (ETMS) modified silica aerogels and xerogels were synthesized by cohydrolyzing the mixtures of ETMS and tetramethylorthosilicate (TMOS). The effects of ETMS content, pH value and solvent addition were investigated. The surface area, pore structure and hydrophobicity were studied using nitrogen and water sorption measurements. By ETMS modification of TMOS gels, high surface area, density and hydrophobicity were achieved. The 25 mole% ETMS-75 mole% TMOS was found to be the best composition for both aerogel and xerogel, which are hydrophobic and have surface areas of 1221 and 832 m2/g, respectively.

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Polymer-Silica Nanocomposite Aerogels with Enhanced Mechanical Properties Using Chemical Vapor Deposition (CVD) of Cyanoacrylates

MRS Proceedings ◽

10.1557/proc-1007-s09-05 ◽

2007 ◽

Vol 1007 ◽

Author(s):

Dylan J. Boday ◽

Douglas A. Loy ◽

Kimberley A. DeFriend ◽

Kennard V. Wilson ◽

David Coder

Keyword(s):

Mechanical Properties ◽

Chemical Vapor Deposition ◽

Surface Area ◽

Vapor Deposition ◽

High Surface ◽

High Surface Area ◽

Chemical Vapor ◽

Fold Increase ◽

Silica Aerogels ◽

Organic Polymer

ABSTRACTAerogels were structurally modified using chemical vapor deposition (CVD) of cyanoacrylate monomers to afford polycyanoacrylate-aerogel nanocomposites. Silica aerogels are low density, high surface area materials whose applications are limited by their fragility. Cyanoacrylate CVD allowed us to deposit a film of organic polymer throughout fragile porous monoliths within hours. Our experiments have shown that polymerization of the cyanoacrylate monomers was initiated by the adsorbed water on the surface of the silica permitting the nanocomposites structures to be formed with little or no sample preparation. We found that the strength of the polycyanoacrylate-aerogel nanocomposites increased thirty two-fold over the untreated aerogels with only a three-fold increase in density and an eight-fold decrease in surface area. Along with the improvement in mechanical properties, the aerogels became less hydrophilic than un-modified aerogels. Polycyanoacrylate-coated aerogels were placed directly into water and did not suffer catastrophic fragmentation as observed with un-modified silica aerogels.

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Size Effect of CaCO3 Filler on the Mechanical Properties of SMC Composites

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.365.244 ◽

2015 ◽

Vol 365 ◽

pp. 244-248 ◽

Cited By ~ 2

Author(s):

Y.J. Lee ◽

Y. Kim ◽

Soo Ryong Kim ◽

Dong Geun Shin ◽

Sea Cheon Oh ◽

...

Keyword(s):

Mechanical Properties ◽

Calcium Carbonate ◽

Size Effect ◽

High Surface ◽

High Surface Area ◽

Mechanical And Thermal Properties ◽

Calcium Carbonates ◽

Surface Areas ◽

High Thermal Resistance ◽

Mineral Fillers

SMC composites consist of chopped glass fiber as a reinforcements, polyester and mineral fillers. Among them, filler is one of the important factors for improving mechanical and thermal properties of composites, but it has not drawn much attention for SMC composites. In this study, the size effect of calcium carbonate as mineral filler on mechanical properties of SMC composites was discussed using five different sizes of commercial calcium carbonates without chopped fiber reinforcement, to focus on the size effect itself. The SMC process was modified to be suitable for a laboratory scale composed of three steps. The mean sizes of the calcium carbonates were 3 – 20 μm, and the specific surface areas were calculated to be 1 – 5 m2/g by BET. Small size of calcium carbonate having high surface area up to 4 m2/g showed high thermal resistance, and showed higher strength comparing to the large fillers because it affected to form a dense packed microstructure.

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A Highly Crystalline Anthracene-Based MOF-74 Series Featuring Electrical Conductivity and Luminescence

10.26434/chemrxiv.8222492 ◽

2019 ◽

Author(s):

Patricia Scheurle ◽

Andre Mähringer ◽

Andreas Jakowetz ◽

Pouya Hosseini ◽

Alexander Richter ◽

...

Keyword(s):

Electrical Conductivity ◽

Metal Ions ◽

Light Emission ◽

Block Design ◽

High Surface ◽

Visible Spectrum ◽

Building Blocks ◽

Divalent Metal Ions ◽

Conductivity Enhancement ◽

Surface Areas

Recently, a small group of metal-organic frameworks (MOFs) has been discovered featuring substantial charge transport properties and electrical conductivity, hence promising to broaden the scope of potential MOF applications in fields such as batteries, fuel cells and supercapacitors. In combination with light emission, electroactive MOFs are intriguing candidates for chemical sensing and optoelectronic applications. Here, we incorporated anthracene-based building blocks into the MOF-74 topology with five different divalent metal ions, that is, Zn2+, Mg2+, Ni2+, Co2+ and Mn2+, resulting in a series of highly crystalline MOFs, coined ANMOF-74(M). This series of MOFs features substantial photoluminescence, with ANMOF-74(Zn) emitting across the whole visible spectrum. The materials moreover combine this photoluminescence with high surface areas and electrical conductivity. Compared to the original MOF-74 materials constructed from 2,5-dihydroxy terephthalic acid and the same metal ions Zn2+, Mg2+, Ni2+, Co2+ and Mn2+, we observed a conductivity enhancement of up to six orders of magnitude. Our results point towards the importance of building block design and the careful choice of the embedded MOF topology for obtaining materials with desired properties such as photoluminescence and electrical conductivity.

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Cellulose Nanofibrils-based Hydrogels for Biomedical Applications: Progresses and Challenges

Current Medicinal Chemistry ◽

10.2174/0929867327666200303102859 ◽

2020 ◽

Vol 27 (28) ◽

pp. 4622-4646 ◽

Cited By ~ 1

Author(s):

Huayu Liu ◽

Kun Liu ◽

Xiao Han ◽

Hongxiang Xie ◽

Chuanling Si ◽

...

Keyword(s):

Mechanical Properties ◽

Metal Ion ◽

Biomedical Applications ◽

Biomedical Application ◽

Cellulose Nanofibrils ◽

Wound Dressings ◽

Preparation Methods ◽

Tissue Scaffold ◽

Surface Areas ◽

Mechanical Methods

Background: Cellulose Nanofibrils (CNFs) are natural nanomaterials with nanometer dimensions. Compared with ordinary cellulose, CNFs own good mechanical properties, large specific surface areas, high Young's modulus, strong hydrophilicity and other distinguishing characteristics, which make them widely used in many fields. This review aims to introduce the preparation of CNFs-based hydrogels and their recent biomedical application advances. Methods: By searching the recent literatures, we have summarized the preparation methods of CNFs, including mechanical methods and chemical mechanical methods, and also introduced the fabrication methods of CNFs-based hydrogels, including CNFs cross-linked with metal ion and with polymers. In addition, we have summarized the biomedical applications of CNFs-based hydrogels, including scaffold materials and wound dressings. Results: CNFs-based hydrogels are new types of materials that are non-toxic and display a certain mechanical strength. In the tissue scaffold application, they can provide a micro-environment for the damaged tissue to repair and regenerate it. In wound dressing applications, it can fit the wound surface and protect the wound from the external environment, thereby effectively promoting the healing of skin tissue. Conclusion: By summarizing the preparation and application of CNFs-based hydrogels, we have analyzed and forecasted their development trends. At present, the research of CNFs-based hydrogels is still in the laboratory stage. It needs further exploration to be applied in practice. The development of medical hydrogels with high mechanical properties and biocompatibility still poses significant challenges.

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Mitigating the Agglomeration of Nanofiller in a Mixed Matrix Membrane by Incorporating an Interface Agent

Membranes ◽

10.3390/membranes11050328 ◽

2021 ◽

Vol 11 (5) ◽

pp. 328

Author(s):

Manh-Tuan Vu ◽

Gloria M. Monsalve-Bravo ◽

Rijia Lin ◽

Mengran Li ◽

Suresh K. Bhatia ◽

...

Keyword(s):

Gas Separation ◽

Polymer Matrix ◽

Ion Beam ◽

High Surface ◽

Mixed Matrix Membrane ◽

Mechanical And Thermal Properties ◽

Separation Membranes ◽

Surface Areas ◽

Separation Membrane ◽

Focus Ion Beam

Nanodiamonds (ND) have recently emerged as excellent candidates for various applications including membrane technology due to their nanoscale size, non-toxic nature, excellent mechanical and thermal properties, high surface areas and tuneable surface structures with functional groups. However, their non-porous structure and strong tendency to aggregate are hindering their potential in gas separation membrane applications. To overcome those issues, this study proposes an efficient approach by decorating the ND surface with polyethyleneimine (PEI) before embedding it into the polymer matrix to fabricate MMMs for CO2/N2 separation. Acting as both interfacial binder and gas carrier agent, the PEI layer enhances the polymer/filler interfacial interaction, minimising the agglomeration of ND in the polymer matrix, which is evidenced by the focus ion beam scanning electron microscopy (FIB-SEM). The incorporation of PEI into the membrane matrix effectively improves the CO2/N2 selectivity compared to the pristine polymer membranes. The improvement in CO2/N2 selectivity is also modelled by calculating the interfacial permeabilities with the Felske model using the gas permeabilities in the MMM. This study proposes a simple and effective modification method to address both the interface and gas selectivity in the application of nanoscale and non-porous fillers in gas separation membranes.

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Mechanical Properties of Hybrid Graphene Nanoplatelet-Nanosilica Filled Unidirectional Basalt Fibre Composites

Nanomaterials ◽

10.3390/nano11061468 ◽

2021 ◽

Vol 11 (6) ◽

pp. 1468

Author(s):

Ummu Raihanah Hashim ◽

Aidah Jumahat ◽

Mohammad Jawaid

Keyword(s):

Mechanical Properties ◽

Polymer Composites ◽

Glass Fibre ◽

Graphene Nanosheets ◽

High Surface ◽

High Surface Area ◽

High Strength ◽

Basalt Fibre ◽

Graphene Nanoplatelet ◽

Dispersion State

Basalt fibre (BF) is one of the most promising reinforcing natural materials for polymer composites that could replace the usage of glass fibre due to its comparable properties. The aim of adding nanofiller in polymer composites is to enhance the mechanical properties of the composites. In theory, the incorporation of high strength and stiffness nanofiller, namely graphene nanoplatelet (GNP), could create superior composite properties. However, the main challenges of incorporating this nanofiller are its poor dispersion state and aggregation in epoxy due to its high surface area and strong Van der Waals forces in between graphene sheets. In this study, we used one of the effective methods of functionalization to improve graphene’s dispersion and also introducing nanosilica filler to enhance platelets shear mechanism. The high dispersive silica nanospheres were introduced in the tactoids morphology of stacked graphene nanosheets in order to produce high shear forces during milling and exfoliate the GNP. The hybrid nanofiller modified epoxy polymers were impregnated into BF to evaluate the mechanical properties of the basalt fibre reinforced polymeric (BFRP) system under tensile, compression, flexural, and drop-weight impact tests. In response to the synergistic effect of zero-dimensional nanosilica and two-dimensional graphene nanoplatelets enhanced the mechanical properties of BFRP, especially in Basalt fibre + 0.2 wt% GNP/15 wt% NS (BF-H0.2) with the highest increment in modulus and strength to compare with unmodified BF. These findings also revealed that the incorporation of hybrid nanofiller contributed to the improvement in the mechanical properties of the composite. BF has huge potential as an alternative to the synthetic glass fibre for the fabrication of mechanical components and structures.

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A simple one-step electrochemical deposition of bioinspired nanocomposite for the non-enzymatic detection of dopamine

Journal of Analytical Science & Technology ◽

10.1186/s40543-021-00260-y ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Vijayaraj Kathiresan ◽

Dinakaran Thirumalai ◽

Thenmozhi Rajarathinam ◽

Miri Yeom ◽

Jaewon Lee ◽

...

Keyword(s):

Electrochemical Deposition ◽

Electrochemical Impedance ◽

High Surface ◽

Electrochemical Characteristics ◽

Surface Areas ◽

Electrochemically Reduced Graphene Oxide ◽

Sensitivity And Selectivity ◽

Controlled Deposition ◽

Enzymatic Detection ◽

Walled Carbon Nanotubes

AbstractA simple and cost-effective electrochemical synthesis of carbon-based nanomaterials for electrochemical biosensor is of great challenge these days. Our study describes a single-step electrochemical deposition strategy to prepare a nanocomposite of electrochemically reduced graphene oxide (ErGO), multi-walled carbon nanotubes (MWCNTs), and polypyrrole (PPy) in an aqueous solution of pH 7.0 for dopamine (DA) detection. The ErGO/MWCNTs/PPy nanocomposites show enhanced electrochemical performance due to the strong π–π* stacking interactions among ErGO, MWCNTs, and PPy. The efficient interaction of the nanocomposites is confirmed by evaluating its physical and electrochemical characteristics using field-emission scanning electron microscopy, Raman spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry, and amperometry. The deposited nanocomposites are highly stable on the substrates and possess high surface areas, which is vital to improve the sensitivity and selectivity for DA detection. The controlled deposition of the ErGO/MWCNTs/PPy nanocomposites can provide enhanced electrochemical detection of DA. The sensor demonstrates a short time response within 2 s and is a highly sensitive approach for DA detection with a dynamic linear range of 25–1000 nM (R2 = 0.999). The detection limit is estimated to be 2.3 nM, and the sensor sensitivity is calculated to be 8.96 μA μM−1 cm−2, with no distinct responses observed for other biological molecules.

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