scholarly journals Preparation and strengthening mechanisms of in-situ HF catalyzed highly porous mullite with whisker frame structure

2021 ◽  
Vol 39 (1) ◽  
pp. 208-215
Author(s):  
Haihong Zhang ◽  
Qi Wang ◽  
Jinhai Wang ◽  
Fangli Yu ◽  
Jianjiang Tang ◽  
...  
Keyword(s):  
Porous Materials ◽  
High Efficiency ◽  
Sol Gel ◽  
High Strength ◽  
Transition Process ◽  
Lap Joints ◽  
Frame Structure ◽  
High Porosity ◽  
Porous Mullite

Using HF as catalyst and based on sol-gel chemical precursor powder molding and sintering process, porous mullite with whisker frame structure was in-situ synthesized in the blank body. Due to the high efficiency catalysis of HF, this structure has both of high porosity and high strength. The effects of HF addition and sintering temperature on the formation of mullite whisker frame, phase transition process, porosity and strength of porous materials were discussed, and the optimal process parameters were determined. The mechanism of strengthening the porous materials was preliminary analyzed, and under the catalysis of HF, the close connection between whisker frame lap joints was formed. When the porosity of mullite is up to 83.22%, the compressive strength of can reach 16.48 MPa.

scholarly journals Anisotropic Cellulose Nanofibers/Polyvinyl Alcohol/Graphene Aerogels Fabricated by Directional Freeze-drying as Effective Oil Adsorbents

Polymers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 712 ◽  
Author(s):  
Lijie Zhou ◽  
Shengcheng Zhai ◽  
Yiming Chen ◽  
Zhaoyang Xu
Keyword(s):  
Polyvinyl Alcohol ◽  
Freeze Drying ◽  
High Efficiency ◽  
Cellulose Nanofibers ◽  
High Strength ◽  
Dip Coating ◽  
High Porosity ◽  
Water Contact ◽  
Water Separation ◽  
Composite Aerogel

Under the current situation of frequent oil spills, the development of green and recyclable high-efficiency oil-absorbing aerogel materials has attracted wide attention from researchers. In this study, we report a high-strength, three-dimensional hydrophobic cellulose nanofiber (CNF)/polyvinyl alcohol (PVA)/graphene oxide (GO) composite aerogel with an anisotropic porous structure, which was fabricated by directional freeze-drying technology using anisotropically grown ice crystals as a template, followed by hydrophobic treatment with a simple dip coating process. The prepared composite aerogel presented anisotropic multi-level pore microstructures, low density (17.95 mg/cm3) and high porosity (98.8%), good hydrophobicity (water contact angle of 142°) and great adsorption capacity (oil absorption reaching 96 times its own weight). More importantly, the oriented aerogel had high strength, whose compressive stress at 80% strain reached 0.22 MPa and could bear more than 22,123 times its own weight without deformation. Therefore, the CNF/PVA/GO composite aerogel prepared by a simple and easy-to-operate directional freeze-drying method is a promising absorbent for oil-water separation.

A novel approach to prepare high strength and high porosity reticulated porous ceramics by in-situ synthesis of mullite whiskers

2021 ◽  
Vol 47 (10) ◽  
pp. 14561-14568
Author(s):  
Dong Lao ◽  
Peng Lin ◽  
Xiajie Liu ◽  
Ruoyu Chen ◽  
Wenbao Jia ◽  
...  
Keyword(s):  
High Strength ◽  
Porous Ceramics ◽  
In Situ Synthesis ◽  
High Porosity ◽  
Novel Approach ◽  
Mullite Whiskers

Growth of Ceria-Zirconia Electrolyte Nanostructures with High Interface Density by Using Sol-gel/GLAD Combination

2004 ◽  
Vol 835 ◽  
Author(s):  
Laxmikant Saraf ◽  
D. W. Matson ◽  
J. S. Young ◽  
C. M. Wang ◽  
S. Thevuthasan
Keyword(s):  
High Efficiency ◽  
Sol Gel ◽  
Mapping Technique ◽  
Cross Sectional ◽  
X Ray ◽  
Glancing Angle ◽  
Zirconia Electrolyte ◽  
Glad Technique ◽  
Cell Electrolytes

ABSTRACTWe report a process for the successful incorporation of ceria in to yttria-stabilized zirconia (YSZ) columnar nanostructures grown by glancing angle deposition (GLAD) technique, resulting in high interface density columnar nanostructures. The incorporation of ceria into YSZ columns is confirmed by scanning electron microscopy (SEM) in a cross sectional geometry with in-situ analysis of elemental x-ray mapping technique and energy dispersive x-ray analysis (EDX). Controlled engineering of such nanostructures is potentially important in the future development of high efficiency solid oxide fuel cell electrolytes. The challenges and advantages of this process are discussed.

scholarly journals Carbon nanotube embedded adhesives for real-time monitoring of adhesion failure in high performance adhesively bonded joints

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Tadej Bregar ◽  
Donglan An ◽  
Somayeh Gharavian ◽  
Marek Burda ◽  
Isidro Durazo-Cardenas ◽  
...  
Keyword(s):  
High Performance ◽  
High Strength ◽  
Epoxy Adhesive ◽  
Lap Joints ◽  
Bonded Joints ◽  
Strain Sensing ◽  
Adhesively Bonded ◽  
Contact Points ◽  
Adhesion Failure

Abstract Carbon nanotubes (CNTs) embedded polymers are of increasing interest to scientific and industrial communities for multi-functional applications. In this article, CNTs have been introduced to high-strength epoxy adhesive for enabling in-situ strain sensing in adhesively bonded aluminium-to-aluminium single-lap joints to accurately indicate the onset and propagation of adhesion failure to the evolution of piezo-resistivity in varying mechanical loads. The CNT modified adhesive in bonded joints and the CNT modified adhesive alone have been tested under monothonic and cyclic tensile loads up to ultimate failure. The changes in the piezo-resistivity induced by the CNTs have been monitored in situ with respect to loading. A novel interpretation method has been developed for progressive, instantaneous adhesion failure estimation under cyclic tensile stresses from a resistivity baseline. The method indicates that the in-situ resistivity changes and the rate of the changes with strain, i.e. sensitivity, strongly correlate with the adhesion failure progression, irrespective of the CNT dispersion quality. Moreover, the effect of bond thickness on the evolution of piezo-resistivity and adhesion failure have been studied. It was observed that relatively thin adhesive bonds (0.18 mm thickness), possessing higher CNT contact points than thick bonds (0.43 mm thickness), provide 100 times higher sensitivity to varying cyclic loads.

scholarly journals In-Situ Synthesis of Hydrophobic Polyurethane Ternary Composite Induced by Hydroxyethyl Cellulose through a Green Method for Efficient Oil Removal

Polymers ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 509
Author(s):  
Junyong Chen ◽  
Xian Yue ◽  
Zhou Xiao ◽  
Huaxin Li ◽  
Xianbo Yu ◽  
...  
Keyword(s):  
High Efficiency ◽  
In Situ Polymerization ◽  
Aqueous Dispersion ◽  
Hydroxyethyl Cellulose ◽  
High Porosity ◽  
Oil Removal ◽  
Aqueous Synthesis ◽  
Ternary Composite ◽  
Hydrophobic Sio2

Hydroxyethyl cellulose (HEC) was introduced to activate the surface of polyurethane (PU) sponge to successfully prepare a hydrophobic ternary composite PU/HEC/SiO2. The hydrophobic layer of the composite was realized by in-situ polymerization of methyltriethoxysilane (MTES) onto the surface of PU sponge. The formation of a stable hydrophobic SiO2 layer solved successfully the problem of ease of SiO2 particles shedding from the composite. Moreover, the amphiphilic molecules produced by the hydrolysis of MTES monomers facilitated the preparation of hydrophobic materials by aqueous dispersion polymerization. Aqueous synthesis made the reaction process environmentally-friendly and pollution-free. The as-prepared composite PU/HEC/SiO2 not only retains high porosity and low density of the PU sponge, but also considerably reduced the surface free energy and increased the surface roughness of the PU sponge. Therefore, outstanding hydrophobicity and high porosity endow the composite with excellent oil removal capability as a high-efficiency absorbent. Moreover, the hydrophobic composite that had absorbed oil could be regenerated easily by squeezing and recycling.

Effects of Sintering Temperature and Porogen Addition on Properties of Low Cost Porous Mullite Ceramics

2015 ◽  
Vol 655 ◽  
pp. 114-117
Author(s):  
Na Na Xu ◽  
Shu Jing Li ◽  
Yuan Bing Li ◽  
Lin Yuan ◽  
Jin Long Zhang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Sintering Temperature ◽  
Raw Materials ◽  
Low Cost ◽  
High Strength ◽  
High Porosity ◽  
Mullite Phase ◽  
Best Value ◽  
Porous Mullite ◽  
Mullite Ceramics

In the present paper, low cost porous mullite ceramics with high porosity, high strength and low thermal conductivity were fabricated using ceramic waste powder and clay as raw materials, and sawdust as porogen. The correlation of phase composition and physicochemical properties of such porous mullite ceramics were researched by varying sintering temperature and the extra addition of sawdust. The results show that: The ceramics show the best comprehensive properties when the sintering temperature is 1400 oC and the addition of sawdust is 30wt%. The results of SEM and EDS analysis confirm that new mullite phase is generated in the ceramics, which can strengthen the ceramics. And the best value of the bulk density, apparent porosity, cold crushing strength and the thermal conductivity of the prepared ceramics is 0.96g.cm-3,60.7%,5.3MPa and 0.212W·m-1·K-1, respectively.

In situ observation of the martensitic transformation in (Mg,Y)-PSZ

1986 ◽  
Vol 44 ◽  
pp. 500-501
Author(s):  
R-R. Lee
Keyword(s):  
Martensitic Transformation ◽  
High Strength ◽  
Nucleation And Growth ◽  
In Situ Observation ◽  
Considerable Potential ◽  
Transmission Electron ◽  
Structural Applications ◽  
Applied Stresses ◽  
Kinetics Of

Partially-stabilized ZrO2 (PSZ) ceramics have considerable potential for advanced structural applications because of their high strength and toughness. These properties derive from small tetragonal ZrO2 (t-ZrO2) precipitates in a cubic (c) ZrO2 matrix, which transform martensitically to monoclinic (m) symmetry under applied stresses. The kinetics of the martensitic transformation is believed to be nucleation controlled and the nucleation is always stress induced. In situ observation of the martensitic transformation using transmission electron microscopy provides considerable information about the nucleation and growth aspects of the transformation.

The use of high-resolution FESEM to study solid-state phase transformations and reactions

1994 ◽  
Vol 52 ◽  
pp. 1028-1029
Author(s):  
P. G. Kotula ◽  
D. D. Erickson ◽  
C. B. Carter
Keyword(s):  
Solid State ◽  
High Resolution ◽  
Phase Transformations ◽  
High Efficiency ◽  
Sol Gel ◽  
Quantitative Information ◽  
Solid State Reactions ◽  
Critical Dimensions ◽  
Backscattered Electrons ◽  
Backscattered Electron

High-resolution field-emission-gun scanning electron microscopy (FESEM) has recently emerged as an extremely powerful method for characterizing the micro- or nanostructure of materials. The development of high efficiency backscattered-electron detectors has increased the resolution attainable with backscattered-electrons to almost that attainable with secondary-electrons. This increased resolution allows backscattered-electron imaging to be utilized to study materials once possible only by TEM. In addition to providing quantitative information, such as critical dimensions, SEM is more statistically representative. That is, the amount of material that can be sampled with SEM for a given measurement is many orders of magnitude greater than that with TEM.In the present work, a Hitachi S-900 FESEM (operating at 5kV) equipped with a high-resolution backscattered electron detector, has been used to study the α-Fe2O3 enhanced or seeded solid-state phase transformations of sol-gel alumina and solid-state reactions in the NiO/α-Al2O3 system. In both cases, a thin-film cross-section approach has been developed to facilitate the investigation. Specifically, the FESEM allows transformed- or reaction-layer thicknesses along interfaces that are millimeters in length to be measured with a resolution of better than 10nm.

Phase separation in sol gel-derived ceramic films of silica-zirconia, alumina-zirconia, and titania-zirconia system

1994 ◽  
Vol 52 ◽  
pp. 646-647
Author(s):  
J. Tong ◽  
L. Eyring
Keyword(s):  
Fracture Toughness ◽  
Phase Separation ◽  
Sol Gel ◽  
Great Influence ◽  
High Strength ◽  
Chemical Durability ◽  
Separation Method ◽  
Toughening Mechanism ◽  
Ceramic Films ◽  
Zirconia Toughened Alumina

There is increasing interest in composites containing zirconia because of their high strength, fracture toughness, and its great influence on the chemical durability in glass. For the zirconia-silica system, monolithic glasses, fibers and coatings have been obtained. There is currently a great interest in designing zirconia-toughened alumina including exploration of the processing methods and the toughening mechanism.The possibility of forming nanocrystal composites by a phase separation method has been investigated in three systems: zirconia-alumina, zirconia-silica and zirconia-titania using HREM. The morphological observations initially suggest that the formation of nanocrystal composites by a phase separation method is possible in the zirconia-alumina and zirconia-silica systems, but impossible in the zirconia-titania system. The separation-produced grain size in silica-zirconia system is around 5 nm and is more uniform than that in the alumina-zirconia system in which the sizes of the small polyhedron grains are around 10 nm. In the titania-zirconia system, there is no obvious separation as was observed in die alumina-zirconia and silica-zirconia system.

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