scholarly journals Synthesis of Flexible Aerogel Composites Reinforced with Electrospun Nanofibers and Microparticles for Thermal Insulation

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Huijun Wu ◽  
Yantao Chen ◽  
Qiliang Chen ◽  
Yunfei Ding ◽  
Xiaoqing Zhou ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Thermal Insulation ◽  
Polyvinylidene Fluoride ◽  
Sol Gel ◽  
Electrospun Nanofibers ◽  
Ambient Atmosphere ◽  
Thermal And Mechanical Properties ◽  
Gel Processing ◽  
Exchange Surface

Flexible silica aerogel composites in intact monolith of 12 cm were successfully fabricated by reinforcing SiO2aerogel with electrospun polyvinylidene fluoride (PVDF) webs via electrospinning and sol-gel processing. Three electrospun PVDF webs with different microstructures (e.g., nanofibers, microparticles, and combined nanofibers and microparticles) were fabricated by regulating electrospinning parameters. The as-electrospun PVDF webs with various microstructures were impregnated into the silica sol to synthesize the PVDF/SiO2composites followed by solvent exchange, surface modification, and drying at ambient atmosphere. The morphologies of the PVDF/SiO2aerogel composites were characterized and the thermal and mechanical properties were measured. The effects of electrospun PVDF on the thermal and mechanical properties of the aerogel composites were evaluated. The aerogel composites reinforced with electrospun PVDF nanofibers showed intact monolith, improved strength, and perfect flexibility and hydrophobicity. Moreover, the aerogel composites reinforced with the electrospun PVDF nanofibers had the lowest thermal conductivity (0.028 W·m−1·K−1). It indicates that the electrospun PVDF nanofibers could greatly improve the mechanical strength and flexibility of the SiO2aerogels while maintaining a lower thermal conductivity, which provides increasing potential for thermal insulation applications.

Robust and superhydrophobic thiourethane bridged polysilsesquioxane aerogels as potential thermal insulation materials

2016 ◽  
Vol 4 (28) ◽  
pp. 10801-10805 ◽  
Author(s):  
Fangxin Zou ◽  
Peng Yue ◽  
Xinghua Zheng ◽  
Dawei Tang ◽  
Wenxin Fu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Thermal Insulation ◽  
Sol Gel ◽  
Vacuum Drying ◽  
Drying Method ◽  
Low Thermal Conductivity ◽  
Insulation Materials ◽  
Sol Gel Process ◽  
Bridged Polysilsesquioxane

Novel thiourethane bridged polysilsesquioxane aerogels prepared by a sol–gel process and vacuum drying method exhibit extraordinary mechanical properties and low thermal conductivity.

Apatite-forming ability and mechanical properties of PTMO-modified CaO–SiO2 hybrids prepared by sol–gel processing: effect of CaO and PTMO contents

Biomaterials ◽  
2002 ◽  
Vol 23 (14) ◽  
pp. 3033-3040 ◽  
Author(s):  
Noboru Miyata ◽  
Ken-ichi Fuke ◽  
Qi Chen ◽  
Masakazu Kawashita ◽  
Tadashi Kokubo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Sol Gel ◽  
Processing Effect ◽  
Gel Processing

scholarly journals Flame-retardant MXene/Polyimide Film with Outstanding Thermal and Mechanical Properties Based on the Secondary Orientation Strategy

2021 ◽  
Author(s):  
Yue Zhu ◽  
Qingyu Peng ◽  
Haowen Zheng ◽  
Fuhua Xue ◽  
Pengyang Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Transition Metal ◽  
Mechanical Performance ◽  
Polyimide Film ◽  
Polymeric Films ◽  
Two Dimensional ◽  
Thermal And Mechanical Properties ◽  
Metal Carbides ◽  
Transition Metal Carbides

With the development of multifunction and miniaturization in modern electronics, polymeric films with strong mechanical performance and high thermal conductivity are urgently needed. Two-dimensional transition metal carbides and nitrides (MXenes)...

Cryogenic thermal insulating and mechanical properties of rigid polyurethane foams blown with hydrofluoroolefin: Effect of perfluoroalkane

2021 ◽  
pp. 0021955X2110626
Author(s):  
Tae Seok Kim ◽  
Yeongbeom Lee ◽  
Chul Hyun Hwang ◽  
Kwang Ho Song ◽  
Woo Nyon Kim
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Thermal Stability ◽  
Cell Size ◽  
Thermal Insulation ◽  
Coefficient Of Thermal Expansion ◽  
Lower Surface ◽  
Polyurethane Foams ◽  
Insulation Material ◽  
Pu Foams

The effect of perfluoroalkane (PFA) on the morphology, thermal conductivity, mechanical properties and thermal stability of rigid polyurethane (PU) foams was investigated under ambient and cryogenic conditions. The PU foams were blown with hydrofluorolefin. Morphological results showed that the minimum cell size (153 μm) was observed when the PFA content was 1.0 part per hundred polyols by weight (php). This was due to the lower surface tension of the mixed polyol solution when the PFA content was 1.0 php. The thermal conductivity of PU foams measured under ambient (0.0215 W/mK) and cryogenic (0.0179 W/mK at −100°C) conditions reached a minimum when the PFA content was 1.0 php. The low value of thermal conductivity was a result of the small cell size of the foams. The above results suggest that PFA acted as a nucleating agent to enhanced the thermal insulation properties of PU foams. The compressive and shear strengths of the PU foams did not appreciably change with PFA content at either −170°C or 20°C. However, it shows that the mechanical strengths at −170°C and 20°C for the PU foams meet the specification. Coefficient of thermal expansion, and thermal shock tests of the PU foams showed enough thermal stability for the LNG carrier’s operation temperature. Therefore, it is suggested that the PU foams blown by HFO with the PFA addition can be used as a thermal insulation material for a conventional LNG carrier.

Influence of additive composition on thermal and mechanical properties of β–Si3N4 ceramics

2004 ◽  
Vol 19 (11) ◽  
pp. 3270-3278 ◽  
Author(s):  
Xinwen Zhu ◽  
Hiroyuki Hayashi ◽  
You Zhou ◽  
Kiyoshi Hirao
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Fracture Toughness ◽  
Nitrogen Pressure ◽  
High Fracture Toughness ◽  
Oxygen Impurity ◽  
Thermal And Mechanical Properties ◽  
High Fracture ◽  
Doped Materials ◽  
Gas Pressure Sintering

Dense β–Si3N4 ceramics were fabricated from α–Si3N4 raw powder by gas-pressure sintering at 1900 °C for 12 h under a nitrogen pressure of 1 MPa, using four different kinds of additive compositions: Yb2O3–MgO, Yb2O3–MgSiN2, Y2O3–MgO, and Y2O3–MgSiN2. The effects of additive composition on the microstructure and thermal and mechanical properties of β–Si3N4 ceramics were investigated. It was found that the replacement of Yb2O3 by Y2O3 has no significant effect on the thermal conductivity and fracture toughness, but the replacement of MgO by MgSiN2 leads to an increase in thermal conductivity from 97 to 113 Wm-1K-1and fracture toughness from 8 to 10 MPa m1/2, respectively. The enhanced thermal conductivity of the MgSiN2-doped materials is attributed to the purification of β–Si3N4 grain and increase of Si3N4–Si3N4 contiguity, resulting from the enhanced growth of large elongated grains. The improved fracture toughness of the MgSiN2-doped materials is attributed to the increase of grain size and fraction of large elongated grains. However, the same thermal conductivity between the Yb2O3- and Y2O3-doped materials is related to not only their similar microstructures, but also the similar abilities of removing oxygen impurity in Si3N4 lattice between Yb2O3 and Y2O3. The same fracture toughness between the Yb2O3- and Y2O3-doped materials is consistent with their similar microstructures. This work implies that MgSiN2 is an effective sintering aid for developing not only high thermal conductivity (>110 Wm−1K−1) but also high fracture toughness (>10 MPa m1/2) of Si3N4 ceramics.

Apatite-forming ability and mechanical properties of PTMO-modified CaO–SiO2–TiO2 hybrids derived from sol–gel processing

Biomaterials ◽  
2004 ◽  
Vol 25 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Noboru Miyata ◽  
Ken-ichi Fuke ◽  
Qi Chen ◽  
Masakazu Kawashita ◽  
Tadashi Kokubo ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Sol Gel ◽  
Gel Processing

scholarly journals Influence of the Direction of Mixture Compaction on the Selected Properties of a Hemp-Lime Composite

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4629
Author(s):  
Przemysław Brzyski ◽  
Piotr Gleń ◽  
Mateusz Gładecki ◽  
Monika Rumińska ◽  
Zbigniew Suchorab ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Temperature Distribution ◽  
Preparation Method ◽  
Thermal And Mechanical Properties ◽  
Compaction Process ◽  
External Wall ◽  
Capillary Uptake ◽  
Parallel Direction ◽  
The Individual

The aim of the research presented in the article was to check the differences in the hygro-thermal and mechanical properties of hemp-lime composites with different shives fractions, depending on the direction of mixture compaction. The research part of the paper presents the preparation method and investigation on the composites. Thermal conductivity, capillary uptake, as well as flexural and compressive strengths were examined. Additionally, an analysis of the temperature distribution in the external wall insulated with the tested composites was performed. The results confirm that the direction of compaction influences the individual properties of the composites in a similar way, depending on the size of the shives. The differences are more pronounced in the case of the composite containing longer fractions of shives. Both thermal conductivity of the material and the capillary uptake ability are lower in the parallel direction of the compaction process. Composites exhibit greater stiffness, but they fail faster with increasing loads when loaded in the direction perpendicular to compaction.

scholarly journals Utilization of SiC and Cu Particles to Enhance Thermal and Mechanical Properties of Al Matrix Composites

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2770 ◽  
Author(s):  
Dongxu Wu ◽  
Congliang Huang ◽  
Yukai Wang ◽  
Yi An ◽  
Chuwen Guo
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
High Thermal Conductivity ◽  
Low Density ◽  
Matrix Composites ◽  
Thermal And Mechanical Properties ◽  
Cu Content ◽  
Sic Particles ◽  
Al Matrix Composites ◽  
Al Matrix

In this work, SiC and Cu particles were utilized to enhance the thermal and mechanical properties of Al matrix composites. The ball-milling and cold-compact methods were applied to prepare Al matrix composites, and the uniform distribution of SiC and Cu particles in the composite confirms the validity of our preparation method. After characterizing the thermal conductivity and the compressibility of the prepared composites, results show that small particles have a higher potential to improve compressibility than large particles, which is attributed to the size effect of elastic modulus. The addition of SiC to the Al matrix will improve the compressibility behavior of Al matrix composites, and the compressibility can be enhanced by 100% when SiC content is increased from 0 to 30%. However, the addition of SiC particles has a negative effect on thermal conductivity because of the low thermal conductivity of SiC particles. The addition of Cu particles to Al-SiC MMCs could further slightly improve the compressibility behavior of Al-SiC/Cu MMCs, while the thermal conductivity could be enhanced by about 100% when the Cu content was increased from 0 to 30%. To meet the need for low density and high thermal conductivity in applications, it is more desirable to enhance the specific thermal conductivity by enlarging the preparation pressure and/or sintering temperature. This work is expected to supply some information for preparing Al matrix composites with low density but high thermal conductivity and high compressibility.

Identification and enhancement of the thermal and mechanical properties of two types of plasters successively derived from gypsum: from the Safi basin and the High Atlas of Marrakech, Morocco

2020 ◽  
Author(s):  
imane baba ◽  
Mounsif Ibnoussina ◽  
Omar Witam
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Mechanical Strength ◽  
Setting Time ◽  
Density Measurement ◽  
Raw Material ◽  
Mechanical And Thermal Properties ◽  
Thermal And Mechanical Properties ◽  
X Ray Diffraction ◽  
High Atlas

<p>Over the past few decades, the construction industry has focused on sustainable, environmentally friendly and easily recyclable materials. The objective of this work is to characterize and enhance the thermal conductivity, mechanical strength and setting time of a composite material based on plaster and lime. This material is designed for use in plasters.</p><p>Two types of gypsum are studied, the first one belongs to the Safi basin, the second one characterizes the High Atlas of Marrakech and precisely Douar Tafza. Geologically speaking, the two sites have many similarities. They are characterized by a Meso-Cenozoic age coverage covering a deformed Paleozoic age basement.</p><p>The characterization of the plaster's raw material, gypsum, was necessary to determine its physical and geotechnical properties, mineralogy, thermal behaviour and microscopic structure. Several analyses have been developed such as: pycnometer density measurement, X-ray diffraction, infrared spectroscopy and scanning electron microscopy.</p><p>We made samples, of standardized dimensions, of two mixtures based on the two types of plaster reinforced by the addition of two types of lime from different localities. The latter are from Marrakech and the Agadir region. The water/plaster mass ratio was set at 0.75 and the addition of lime was achieved by increasing its percentage in slices by 12.5% and up to 50%.</p><p>The reinforcement of plaster with lime has enhanced its thermal and mechanical properties and setting time. The measurements show that the addition of lime has reduced the thermal conductivity and increased the mechanical strength of both types of plaster. In addition, following the addition of lime, the setting time has decreased and the basicity of the material has increased. Noting that the intrinsic properties of the raw material influence the mechanical and thermal properties of the material.</p><p><strong>Keywords:</strong>   plaster, enhancement, properties, mechanical, thermal, Morocco</p>

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