scholarly journals Robust polyimide nano/microfibre aerogels welded by solvent-vapour for environmental applications

2019 ◽  
Vol 6 (8) ◽  
pp. 190596 ◽  
Author(s):  
Ying Shen ◽  
Dawei Li ◽  
Bingyao Deng ◽  
Qingsheng Liu ◽  
Huizhong Liu ◽  
...  
Keyword(s):  
Compressive Strain ◽  
Building Blocks ◽  
Uniform Structure ◽  
Low Density ◽  
High Porosity ◽  
Air Filtration ◽  
Solvent Vapour ◽  
Fibrous Network ◽  
Aerosol Filtration ◽  
New Perspective

Due to the high porosity, resilience and ultra-low density, polymer nanofibre-derived aerogels (NFAs) have been widely investigated in recent years. However, welding of the fibrous networks of NFAs, which has been proved extremely essential to their structural performance, still remains a major challenge. Herein, electrospun polyimide (PI) nano/microfibres were used as building blocks to construct hierarchically porous aerogels through a solid-templating technique. By further welding the adjacent nano/microfibres at their cross-points in a controllable fashion by solvent-vapour, super elasticity was achieved for the aerogels, with a recoverable ultimate strain of 80%. It is noteworthy that this process is free from cross-linking, heating and significant structure changing (i.e. chemical structure, crystallinity and fibrous network). Additionally, the porous structure of PI nano/microfibre aerogels (PI-N/MFAs) could be tuned by adjusting the organization of microfibres from a disordered/ordered cellular to a uniform structure. The as-obtained aerogels showed ultra-low density (4.81 mg cm −3 ), high porosity (99.66%), and comparable or higher recoverable compressive strain and stress relative to the other nanofibre-based aerogels. Furthermore, we showed the potential of such an aerogel for particle or aerosol filtration. PI nanofibre aerogels composite filters (PI-NFACFs) manifested excellent performance in PM 2.0 filtration (99.6% filtration efficiency with 115 Pa pressure drop). Therefore, this study brought a new perspective on the simple preparation of nanofibre-based aerogels for air filtration.

scholarly journals Low-Density Insulation Blocks and Hardboards from Amaranth (Amaranthus cruentus) Stems, a New Perspective for Building Applications

Coatings ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 349
Author(s):  
Philippe Evon ◽  
Guyonne de Langalerie ◽  
Laurent Labonne ◽  
Othmane Merah ◽  
Thierry Talou ◽  
...  
Keyword(s):  
Aerial Part ◽  
Low Density ◽  
Renewable Materials ◽  
Fractionation Process ◽  
Amaranthus Cruentus ◽  
Cosmetic Industry ◽  
New Perspective ◽  
The One ◽  
Promising Source ◽  
Amaranth Oil

Nowadays, amaranth appears as a promising source of squalene of vegetable origin. Amaranth oil is indeed one of the most concentrated vegetable oils in squalene, i.e., up to 6% (w/w). This triterpene is highly appreciated in cosmetology, especially for the formulation of moisturizing creams. It is almost exclusively extracted from the liver of sharks, causing their overfishing. Thus, providing a squalene of renewable origin is a major challenge for the cosmetic industry. The amaranth plant has thus experienced renewed interest in recent years. In addition to the seeds, a stem is also produced during cultivation. Representing up to 80% (w/w) of the plant aerial part, it is composed of a ligneous fraction, the bark, on its periphery, and a pith in its middle. In this study, a fractionation process was developed to separate bark and pith. These two fractions were then used to produce renewable materials for building applications. On the one hand, the bark was used to produce hardboards, with the deoiled seeds acting as natural binder. Such boards are a viable alternative to commercial wood-based panels. On the other hand, the pith was transformed into cohesive and machinable low-density insulation blocks revealing a low thermal conductivity value.

Aerogels as promising materials for antibacterial applications: a mini-review

2021 ◽  
Author(s):  
Gulcihan Guzel Kaya ◽  
Elena Aznar ◽  
Huseyin Deveci ◽  
Ramón Martínez-Máñez
Keyword(s):  
Antibacterial Activity ◽  
Low Density ◽  
High Porosity

Aerogels with ultra-low density, high porosity, tunable sizes, and biocompatibility have been regarded as promising carriers for antibacterial applications. Different approaches can be followed to obtain such beneficial antibacterial activity.

scholarly journals Continuous, Strong, Porous Silk Firoin-Based Aerogel Fibers toward Textile Thermal Insulation

Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1899 ◽  
Author(s):  
Haiwei Yang ◽  
Zongqian Wang ◽  
Zhi Liu ◽  
Huan Cheng ◽  
Changlong Li
Keyword(s):  
Heat Transfer ◽  
Thermal Insulation ◽  
Hollow Fiber ◽  
High Performance ◽  
Large Scale ◽  
Low Density ◽  
Potential Candidate ◽  
Scale Production ◽  
Insulation Material ◽  
High Porosity

Aerogel fiber, with the characteristics of ultra-low density, ultra-high porosity, and high specific surface area, is the most potential candidate for manufacturing wearable thermal insulation material. However, aerogel fibers generally show weak mechanical properties and complex preparation processes. Herein, through firstly preparing a cellulose acetate/polyacrylic acid (CA/PAA) hollow fiber using coaxial wet-spinning followed by injecting the silk fibroin (SF) solution into the hollow fiber, the CA/PAA-wrapped SF aerogel fibers toward textile thermal insulation were successfully constructed after freeze-drying. The sheath (CA/PAA hollow fiber) possesses a multiscale porous structure, including micropores (11.37 ± 4.01 μm), sub-micron pores (217.47 ± 46.16 nm), as well as nanopores on the inner (44.00 ± 21.65 nm) and outer (36.43 ± 17.55 nm) surfaces, which is crucial to the formation of a SF aerogel core. Furthermore, the porous CA/PAA-wrapped SF aerogel fibers have many advantages, such as low density (0.21 g/cm3), high porosity (86%), high strength at break (2.6 ± 0.4 MPa), as well as potential continuous and large-scale production. The delicate structure of multiscale porous sheath and ultra-low-density SF aerogel core synergistically inhibit air circulation and limit convective heat transfer. Meanwhile, the high porosity of aerogel fibers weakens heat transfer and the SF aerogel cellular walls prevent infrared radiation. The results show that the mat composed of these aerogel fibers exhibits excellent thermal insulating properties with a wide working temperature from −20 to 100 °C. Therefore, this SF-based aerogel fiber can be considered as a practical option for high performance thermal insulation.

Ultra-low density aerogel optical applications

1993 ◽  
Vol 8 (2) ◽  
pp. 352-355 ◽  
Author(s):  
S.P. Hotaling
Keyword(s):  
Surface Topology ◽  
Low Density ◽  
High Porosity ◽  
Fractal Surface ◽  
Surface Geometry ◽  
Surface Machining ◽  
Low Weight ◽  
Optical Applications ◽  
Materials Used ◽  
Reflective Coatings

Despite the extremely low density and the hence low weight of aerogel materials, the applicability of these materials to reflective applications has had little attention due to the high porosities exhibited by the materials. This high porosity yields an intrinsically rough but uniform surface topology for aerogel of density in the low hundreds of milligrams per cubic centimeter and a fractal surface geometry for lower density aerogel (densities of the order of tens of milligrams per cubic centimeter). This paper presents new results of aerogel materials used as ultra-light substrates for reflective coatings by way of surface machining, polishing, and planarization prior to metallization, and the optical characterization thereof.

scholarly journals High-Porosity Thermal Barrier Coatings from High-Power Plasma Spray Equipment—Processing, Performance and Economics

Coatings ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 957
Author(s):  
Nicholas Curry ◽  
Matthias Leitner ◽  
Karl Körner
Keyword(s):  
Thermal Barrier Coatings ◽  
High Power ◽  
Deposition Efficiency ◽  
Sintering Behavior ◽  
Thermal Barrier ◽  
Low Density ◽  
High Porosity ◽  
Plasma System ◽  
Barrier Coatings ◽  
The Impact

High-porosity thermal barrier coatings are utilized on gas turbine components where maximizing the coating thermal insulation capability is the primary design criteria. Though such coatings have been in industrial use for some time, manufacturing high-porosity coatings quickly and efficiently has proven challenging. With the industry demand to increase productivity and reduce waste generation, there is a drive to look at improved coating manufacturing methods. This article looks at high-porosity coatings manufactured using a high-power plasma system in comparison with a current industrial coating. A commercial spray powder is compared with an experimental Low-Density powder developed to maximize coating porosity without sacrificing coating deposition efficiency. The resultant coatings have been assessed for their microstructure, adhesion strength, furnace cyclic lifetime, thermal conductivity and sintering behavior. Finally, the impact of spray processing on coating economics is discussed. The use of a Low-Density powder with a high-power plasma system allows a high-porosity coating to be manufactured more efficiently and more cost effectively than with conventional powder feedstock. The improvement in thermal properties for the experimental coating demonstrates there is scope to improve industrial coatings by designing with specific thermal resistance rather than thickness and porosity as coating requirements.

Rigid Polyurethane Foam: A Versatile Energy Efficient Material

2016 ◽  
Vol 678 ◽  
pp. 88-98 ◽  
Author(s):  
Harpal Singh
Keyword(s):  
Thermal Conductivity ◽  
Polyurethane Foam ◽  
Weight Ratio ◽  
Building Envelope ◽  
Polymerization Reaction ◽  
Low Density ◽  
High Porosity ◽  
Rigid Polyurethane Foam ◽  
Low Thermal Conductivity ◽  
Moisture Permeability

Rigid polyurethane foam (RPUF) is typically prepared by the reaction of an isocyanate, such as methyl diphenyl diisocyanate (MDI) with a polyol blend. During the polymerization reaction, a blowing agent expands the reacting mixture. The finished product is a solid, cellular polymer with a high thermal resistance. RPUF is an outstanding material for different applications. It has many desirable properties such as low thermal conductivity, low density, low water absorption, low moisture permeability, excellent dimensional stability, high strength to weight ratio. So, it is the best insulating material for industrial buildings, cold storages, telecom and defense shelters due to low thermal conductivity, low density, low moisture permeability and high porosity. It works to reduce heating and cooling loss, improving the efficiency of the building envelope. Thus, RPUF insulation in building envelopes brings additional benefits in energy savings, resulting in lower energy bills and protecting the environment by cutting CO2 emissions.

scholarly journals Physico-chemical and rheological properties of gelatinized/freeze-dried cereal starches

2017 ◽  
Vol 31 (3) ◽  
pp. 357-365 ◽  
Author(s):  
Magdalena Krystyjan ◽  
Wojciech Ciesielski ◽  
Dorota Gumul ◽  
Krzysztof Buksa ◽  
Rafał Ziobro ◽  
...  
Keyword(s):  
Rheological Properties ◽  
Binding Capacity ◽  
Uniform Structure ◽  
High Porosity ◽  
Water Binding ◽  
Molecular Weights ◽  
Physico Chemical ◽  
Lower Viscosity ◽  
Freeze Dried ◽  
Modified Starches

AbstractThe influence of gelatinization and freeze-drying process on the physico-chemical and rheological properties of cereal starches was evaluated, and it was observed that modified starches revealed an increased water binding capacity and solubility when compared to dry starches, while exhibiting the same amylose and fat contents. The molecular weights of starches decreased after modification which resulted in the lower viscosity of dissolved modified samples in comparison to native starch pastes. As it was observed by scanning electron microscopy modified starches were characterized by an expanded surface, a uniform structure and high porosity.

Preparation of Mesoporous Oxides for Mems Structures

2000 ◽  
Vol 657 ◽  
Author(s):  
Jong-Ah Paik ◽  
Nobuaki Kitazawa ◽  
Shih-Kang Fan ◽  
Chang-Jin Kim ◽  
Ming C. Wu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Surface Roughness ◽  
Block Copolymers ◽  
Low Density ◽  
High Porosity ◽  
Mems Devices ◽  
Mems Fabrication ◽  
Mesoporous Oxide ◽  
Mesoporous Oxides ◽  
Uniform Pore Size

ABSTRACTThe high porosity and uniform pore size provided by mesoporous oxide films offer interesting opportunities for MEMS devices that require low density and low thermal conductivity. This paper describes recent efforts at adapting mesoporous films for MEMS fabrication. Mesoporous SiO2 and Al2O3 films were prepared using block copolymers as the structure-directing agents, leading to films which were 70% porous and < 5 nm surface roughness. A number of etchants were investigated and good etch selectivity was observed with both dry and wet systems. Micromachining methods were used to fabricate cantilevers, micro bridges and membranes.

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