Manufactory and Properties of Poly(p-Phenylenebenzobisoxazole) Aerogels Prepared by a Simple Freeze-Drying Procedure

2020 ◽  
Vol 993 ◽  
pp. 662-668
Author(s):  
Yu Nong Wei ◽  
Guang Li ◽  
Sheng Lin Yang ◽  
Jun Hong Jin
Keyword(s):  
High Performance ◽  
Freeze Drying ◽  
Sol Gel ◽  
Fire Retardant ◽  
Decomposition Temperature ◽  
High Specific Surface Area ◽  
High Porosity ◽  
Cellulose Aerogel ◽  
Small Pore ◽  
Small Pore Diameter

Aerogels based on organic high performance fibers have been attracted great attention due to its excellent thermal and mechanical properties. Here, PBO nanofiber aerogel were prepared from the super-fiber PBO through a top-down process with a sol-gel process and a simple freeze-drying process, followed by thermal cross-linking. The prepared aerogel has a small volume shrinkage, a high specific surface area of 168.9 m2 /g and a small pore diameter of 1.356 nm. Because of its 3D porous structure, it results in a low density of 6 to 30 mg/cm3 and a high porosity (98%). The aerogel retains the molecular structure of PBO at the same time, which gives it initial thermal decomposition temperature up to 500 °C and a superior fire-retardant capability. PBO aerogel possesses good compressive properties with a yield stress of 0.44MPa at 80% strain and an elasticity modulus of 1.98 MPa which is higher than SiO2 and cellulose aerogel reported.

scholarly journals Elucidation of the Crystal Growth Characteristics of SnO2 Nanoaggregates Formed by Sequential Low-Temperature Sol-Gel Reaction and Freeze Drying

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1738
Author(s):  
Saeid Vafaei ◽  
Alexander Wolosz ◽  
Catlin Ethridge ◽  
Udo Schnupf ◽  
Nagisa Hattori ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Low Temperature ◽  
Photoelectron Spectroscopy ◽  
High Performance ◽  
Freeze Drying ◽  
Sno2 Nanoparticles ◽  
Sol Gel ◽  
Functional Materials ◽  
Cost Effective ◽  
High Concentration

SnO2 nanoparticles are regarded as attractive, functional materials because of their versatile applications. SnO2 nanoaggregates with single-nanometer-scale lumpy surfaces provide opportunities to enhance hetero-material interfacial areas, leading to the performance improvement of materials and devices. For the first time, we demonstrate that SnO2 nanoaggregates with oxygen vacancies can be produced by a simple, low-temperature sol-gel approach combined with freeze-drying. We characterize the initiation of the low-temperature crystal growth of the obtained SnO2 nanoaggregates using high-resolution transmission electron microscopy (HRTEM). The results indicate that Sn (II) hydroxide precursors are converted into submicrometer-scale nanoaggregates consisting of uniform SnO2 spherical nanocrystals (2~5 nm in size). As the sol-gel reaction time increases, further crystallization is observed through the neighboring particles in a confined part of the aggregates, while the specific surface areas of the SnO2 samples increase concomitantly. In addition, X-ray photoelectron spectroscopy (XPS) measurements suggest that Sn (II) ions exist in the SnO2 samples when the reactions are stopped after a short time or when a relatively high concentration of Sn (II) is involved in the corresponding sol-gel reactions. Understanding this low-temperature growth of 3D SnO2 will provide new avenues for developing and producing high-performance, photofunctional nanomaterials via a cost-effective and scalable method.

An Environment-Friendly Thermal Insulation Material from Porous Cellulose Aerogel

2013 ◽  
Vol 773 ◽  
pp. 487-491 ◽  
Author(s):  
Jian Jun Shi ◽  
Ling Bin Lu ◽  
Jing Ying Zhang
Keyword(s):  
Freeze Drying ◽  
Solvent System ◽  
Insulation Material ◽  
High Porosity ◽  
Porous Network ◽  
Environment Friendly ◽  
Cellulose Aerogel ◽  
Cellulose Hydrogel ◽  
Drying Technology ◽  
Insulation Performance

Cellulose hydrogel was prepared by using the NaOH/ Thiourea/ H2O as solvent system, cellulose aerogels were obtained by freeze-drying technology. The results showed that cellulose aerogel had porous network structure. Freeze-drying method was an effective way to prepare cellulose aerogel, and the volume shrinkage was 20.41%-28.36%. Bulk cellulose aerogel had low density, high porosity and fine mechanical strength. The density was low to 0.233g/cm3, and the porosity was up to 84.88%. The compressive strength was 5.7-8.2MPa. Cellulose aerogel had good heat insulation performance and thermal conductivity could be as low as 0.029 W/ (m·K). This work provided a foundation for the possibility of applying cellulose aerogels in the insulating material field.

scholarly journals Fabrication Of Carbon Aerogels From Coir For Oil Adsorption

2022 ◽  
Vol 964 (1) ◽  
pp. 012033
Author(s):  
Hieu M Nguyen ◽  
Khoi A Tran ◽  
Tram T N Nguyen ◽  
Nga N H Do ◽  
Kien A Le ◽  
...  
Keyword(s):  
Freeze Drying ◽  
Oil Spills ◽  
Sol Gel ◽  
Urea Solution ◽  
Carbon Aerogels ◽  
Low Density ◽  
High Porosity ◽  
Motor Oil ◽  
Sol Gel Process ◽  
Oil Adsorption

Abstract Coir, known as coconut fibers, are an abundant cellulosic source in Vietnam, which are mostly discarded when copra and coconut water are taken, causing environmental pollution and waste of potential biomass. In this research, carbon aerogels from chemically pretreated coir were successfully synthesized via simple sol-gel process with NaOH-urea solution, economical freeze-drying, and carbonization. The samples, including pretreated coir, coir aerogels, and carbon aerogels, are characterized using FTIR spectroscopy, SEM, XRD spectroscopy, and TGA. The carbon aerogels exhibit low density (0.034–0.047 g/cm3), high porosity (97.63–98.32 %), and comparable motor oil sorption capacity (22.71 g/g). The properties of carbon aerogels are compared with those of coir aerogels, indicating such better values than those of coir aerogels. Coir-derived carbon aerogels is a potential replacement for the hydrophobically-coated cellulose aerogels in term of treating oil spills.

Cellulose-Silica Composite Aerogels Prepared with Sodium Silicate by Freeze Drying Method

2016 ◽  
Vol 697 ◽  
pp. 129-133 ◽  
Author(s):  
Hua Zheng Sai ◽  
Rui Fu ◽  
Li Xing ◽  
Jun Hui Xiang ◽  
Zhen You Li ◽  
...  
Keyword(s):  
Freeze Drying ◽  
Sol Gel ◽  
Cellulose Nanofibers ◽  
Compression Modulus ◽  
High Specific Surface Area ◽  
Regenerated Cellulose ◽  
Organic Precursor ◽  
Silica Composite ◽  
Composite Aerogels ◽  
Solvent Replacement

The cellulose-silica composite aerogels (CAs) were fabricated through a permeation sol-gel process in the regenerated cellulose hydrogels followed by freeze drying. The precursor Na2SiO3 instead of traditional organic precursor was diffused in the cellulose matrix followed by permeating the catalyst into the cellulose nanofibers network gradually to promote the in situ condensation of Na2SiO3 to form a SiO2 gel skeleton from outside to inside. The obtained CAs displayed the interpenetrating network (IPN) structure of the regenerated cellulose nanofibers network and the SiO2 gel skeleton in nanoscale. In the IPN structure, the flexible cellulose nanofibers network was supported by the hard inorganic network effectively to sustain the compression and the silica gel skeleton protect the cellulose nanofibers to avoid the remodeling of their shape in the process of solvent replacement before freeze drying. Due to the synergic effects of the different network, the IPN structure endows the CAs with high compression modulus (as high as 15.48 MPa), high specific surface area (as high as 621 m2 g-1) and low density (less than 0.182 g cm-3).

Improvement of Mesopore Structure of Resorcinol and Formaldehyde Carbon Cryogels by Acid Solution

2008 ◽  
Vol 55-57 ◽  
pp. 529-532
Author(s):  
K. Kraiwattanawong ◽  
P. Kitchaiya ◽  
Arthit Neramittagapong ◽  
P. Praserthdam ◽  
H. Tamon
Keyword(s):  
Acid Solution ◽  
Pore Structure ◽  
Freeze Drying ◽  
Sol Gel ◽  
Inert Atmosphere ◽  
Size Distributions ◽  
Large Pore ◽  
Small Pore ◽  
Carbon Gels ◽  
Mesopore Structure

Resorcinol and formaldehyde (RF) carbon cryogels are prepared by sol-gel polycondensation by using sodium carbonate (C) as a catalyst with water (W) as solvent, immersed in acid solution, hydrochloric acid (HCl), dried by freeze-drying technique and then carbonized under inert atmosphere, respectively. Compared with their carbon precursors, both Vmes and mesopore size distributions of all carbon cryogels can be developed since the pore shrinkage is the crucial role in the change of pore structure of carbon gels. HCl may promote the strength of small pore structure and increase the pore shrinkage of large pore structure. Consequently, the treatment of HCl does not only enhance the partial collapse of large pore structure, the treatment also increases the strength of small pore structure to inhibit the shrinkage of this structure during carbonization as well.

Growth of Carbon Nanotube on the Ni-Mesoporous Alumina Catalysts for Use as Adsorbent

2013 ◽  
Vol 829 ◽  
pp. 559-562
Author(s):  
Pariya Shahbazi ◽  
Mahmood Kazemzad ◽  
Amirali Yuzbashi
Keyword(s):  
Carboxylic Acids ◽  
Organic Compounds ◽  
High Performance ◽  
Sol Gel ◽  
High Specific Surface Area ◽  
Mesoporous Alumina ◽  
Porous Support ◽  
Ordered Mesoporous Materials ◽  
Ordered Mesoporous ◽  
Commercial Applications

Ordered mesoporous materials with high specific surface area and large pore volume have high potential for commercial applications in adsorption and catalysis. In this study, ordered mesoporous alumina (γ-alumina) with high thermal and chemical resistance was synthesized by the sol-gel method using various organic compounds, i.e. aminoacids and carboxylic acids as template. The obtained data showed that γ-Al2O3 produced in the presence of carboxylic acids as template results in very well catalytic activities for CNT growth. The best results obtained using Ni catalysts supported on alumina at a temperature of 900 °C. Since the method and amount of the catalyst deposited on a porous support affects its efficiency in CVD growth of CNT, the above parameters have been also optimized in this work. Alumina supported CNT,s were applied as adsorbent for removal of some organic compounds from aqueous samples. The microstructure, morphology, and chemical composition of the adsorbents were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and scanning electron microscopy (SEM). Efficiency of synthesized samples for adsorption organic compounds was investigated by high performance liquid chromatography (HPLC) analysis of filtrate. This work showed that, although mesoporous alumina supported CNT can be applied as a good adsorbent for removal of trace amounts of organic compounds from drinking water efficiency of the adsorbents are extremely dependent on the porous adsorbent syntheses condition.

Experimental Study on Micropore Structure and Filtration Characteristics of Polypropylene Melt-Blown Nonwoven

2014 ◽  
Vol 1048 ◽  
pp. 493-497 ◽  
Author(s):  
Bing Xuan Ni ◽  
Peng Zhang
Keyword(s):  
Pore Size ◽  
Capillary Flow ◽  
Nonwoven Fabric ◽  
High Specific Surface Area ◽  
High Porosity ◽  
Air Filtration ◽  
Micropore Structure ◽  
Small Pore ◽  
Polypropylene Melt ◽  
Melt Blown Nonwoven

Melt-blown nonwoven fabric is a kind of excellent fiber filter media in the field of air filtration, which has the characteristics of high specific surface area, small pore size, high porosity, superfine fiber, low pressure drop and high filtration efficiency. In this paper, the microstructure characteristics of pore diameter and pore size distribution of polypropylene melt-blown nonwoven, and the relationship of micropore structure and filtration characteristics, continuous dust holding test were studies by using instruments of Microscope, Capillary Flow Porometer and TSI 8130 Auto Filter Tester.

scholarly journals A Novel Application of Cellulose Aerogel Composites From Pineapple Leaf Fibers And Cotton Waste: Removal of Dyes and Oil In Wastewater

2021 ◽  
Author(s):  
Phu V. Vu ◽  
Trung D. Doan ◽  
Giang C. Tu ◽  
Nga H.N. Do ◽  
Kien A. Le ◽  
...  
Keyword(s):  
Methylene Blue ◽  
Oil Pollution ◽  
Removal Rate ◽  
Sol Gel ◽  
Water Remediation ◽  
Urea Solution ◽  
High Porosity ◽  
Wastewater Remediation ◽  
Cellulose Aerogel ◽  
Cotton Waste

Abstract In a world where demands for freshwater are ever-growing, wastewater remediation becomes a global concern. Especially, water, which is contaminated by oil, dyes, poses challenges to the management of water resources. The development of innovative processes for wastewater treatment is still a major obstacle. With regard to its fast removal rate and environmental compatibility, cellulose aerogel composites are recently considered as a potential contributor for water remediation. In this study, cellulose aerogel composites are fabricated using the sol-gel method from two-agroindustrial wastes: pineapple leaf fibers and cotton waste fibers in alkali-urea solution followed by freeze-drying. The prepared cellulose aerogel composites are extremely lightweight with a low density (0.053−0.069 g.cm−3) and high porosity of nearly 95%. It is worth noting that the mechanical strength of the cellulose aerogel composites is remarkably improved with their Young’s modulus increasing by 5-9 times compared to that of the previous aerogel composites using polyvinyl alcohol as a binder. The as-synthesized aerogel composites are directly applied to adsorb cationic methylene blue and exhibit a maximum adsorption uptake of 34.01 g.g-1. The methyltrimethoxysilane-coated cellulose aerogel composites also show their ability to deal with oil pollution with a maximum oil adsorption capacity of 15.8 g.g−1 within only 20 sec. Besides the oil removal, our developed cellulose aerogel composites have demonstrated their capability in treating dye-contaminated wastewater for the first time based on their evidenced ability to eliminate methylene blue.

Controlling porosity and density of nanocellulose aerogels for superhydrophobic light materials

TAPPI Journal ◽  
2018 ◽  
Vol 17 (03) ◽  
pp. 145-153 ◽  
Author(s):  
Chengua Yu ◽  
Feng Wang ◽  
Shiyu Fu ◽  
Lucian Lucia
Keyword(s):  
Contact Angle ◽  
Freeze Drying ◽  
Engine Oil ◽  
High Porosity ◽  
Water Mixture ◽  
Waste Engine Oil ◽  
Hydrophobically Modified ◽  
Static Contact ◽  
Oil Water ◽  
Hydrophobic Material

A very low-density oil-absorbing hydrophobic material was fabricated from cellulose nanofiber aerogels–coated silane substances. Nanocellulose aerogels (NCA) superabsorbents were prepared by freeze drying cellulose nanofibril dispersions at 0.2%, 0.5%, 0.8%, 1.0%, and 1.5% w/w. The NCA were hydrophobically modified with methyltrimethoxysilane. The surface morphology and wettability were characterized by scanning electron microscopy and static contact angle. The aerogels displayed an ultralow density (2.0–16.7 mg·cm-3), high porosity (99.9%–98.9%), and superhydrophobicity as evidenced by the contact angle of ~150° that enabled the aerogels to effectively absorb oil from an oil/water mixture. The absorption capacities of hydrophobic nanocellulose aerogels for waste engine oil and olive oil could be up to 140 g·g-1 and 179.1 g·g-1, respectively.

scholarly journals Effect of Nanofiller Content on Dynamic Mechanical and Thermal Properties of Multi-Walled Carbon Nanotube and Montmorillonite Nanoclay Filler Hybrid Shape Memory Epoxy Composites

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 700
Author(s):  
Muhamad Hasfanizam Mat Yazik ◽  
Mohamed Thariq Hameed Sultan ◽  
Mohammad Jawaid ◽  
Abd Rahim Abu Talib ◽  
Norkhairunnisa Mazlan ◽  
...  
Keyword(s):  
Shape Memory ◽  
High Performance ◽  
Loss Modulus ◽  
Decomposition Temperature ◽  
Hybrid Nanocomposites ◽  
Mechanical And Thermal Properties ◽  
Scanning Calorimetry ◽  
Hybrid Filler ◽  
Dynamic Mechanical ◽  
Tan Δ

The aim of the present study has been to evaluate the effect of hybridization of montmorillonite (MMT) and multi-walled carbon nanotubes (MWCNT) on the thermal and viscoelastic properties of shape memory epoxy polymer (SMEP) nanocomposites. In this study, ultra-sonication was utilized to disperse 1%, 3%, and 5% MMT in combination with 0.5%, 1%, and 1.5% MWCNT into the epoxy system. The fabricated SMEP hybrid nanocomposites were characterized via differential scanning calorimetry, dynamic mechanical analysis, and thermogravimetric analysis. The storage modulus (E’), loss modulus (E”), tan δ, decomposition temperature, and decomposition rate, varied upon the addition of the fillers. Tan δ indicated a reduction of glass transition temperature (Tg) for all the hybrid SMEP nanocomposites. 3% MMT/1% MWCNT displayed best overall performance compared to other hybrid filler concentrations and indicated a better mechanical property compared to neat SMEP. These findings open a way to develop novel high-performance composites for various potential applications, such as morphing structures and actuators, as well as biomedical devices.

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