scholarly journals Processing nanoporous organic polymers in liquid amines

2019 ◽  
Vol 10 ◽  
pp. 1844-1850 ◽  
Author(s):  
Jeehye Byun ◽  
Damien Thirion ◽  
Cafer T Yavuz
Keyword(s):  
Elevated Temperatures ◽  
Carbon Film ◽  
Carboxyl Groups ◽  
Network Structures ◽  
High Porosity ◽  
Organic Polymers ◽  
Photo Catalysis ◽  
Nanoporous Polymers ◽  
Polymeric Chains ◽  
Fine Carbon

Rigid network structures of nanoporous organic polymers provide high porosity, which is beneficial for applications such as gas sorption, gas separation, heterogeneous (photo)catalysis, sensing, and (opto)electronics. However, the network structures are practically insoluble. Thus, the processing of nanoporous polymers into nanoparticles or films remains challenging. Herein, we report that nanoporous polymers made via a Knoevenagel-like condensation can be easily processed into nanoparticles (115.7 ± 40.8 nm) or a flawless film by using liquid amines as a solvent at elevated temperatures. FTIR spectra revealed that the carboxyl groups in the nanoporous polymers act as reactive sites for amines, forming new functionalities and spacing the polymeric chains to be dissolved in the liquid amines. The processed film was found to be CO2-philic despite the low surface area, and further able to be transformed into a fine carbon film by thermal treatment.

On Factors Influencing Macro Shrinkage Porosity Formation in Compacted Graphite Iron

2014 ◽  
Vol 790-791 ◽  
pp. 429-434 ◽  
Author(s):  
Sadaf Vazehrad ◽  
Jessica Elfsberg ◽  
Attila Diószegi
Keyword(s):  
Elevated Temperatures ◽  
Carbon Film ◽  
Shrinkage Porosity ◽  
Compacted Graphite Iron ◽  
Porosity Formation ◽  
Porosity Level ◽  
Compacted Graphite ◽  
Factors Influencing

The purpose of this work is to investigate the relation between macro shrinkage porosity level and the level of graphite nodularity, gaseous elements and the size of eutectic colonies in compacted graphite iron. Also, the internal shrinkage-pore surfaces were analyzed by SEM and EDS techniques. It was found that samples with higher shrinkage porosity level, contained higher level of graphite nodularity and number of eutectic colonies. Also, samples with higher level of gaseous elements (Hydrogen and Nitrogen) showed higher tendency to shrinkage porosity formation. Austenite dendrites with different morphologies were observed inside the pores, indicating that were formed at different times during solidification, and the surface of the pores were covered with a layer of carbon film indicating that the pores were internal, with no contact to the atmosphere at elevated temperatures.

scholarly journals Selective removal of cationic micro-pollutants using disulfide-linked network structures

RSC Advances ◽  
2017 ◽  
Vol 7 (42) ◽  
pp. 25969-25977 ◽  
Author(s):  
Mehmet Sahin Atas ◽  
Sami Dursun ◽  
Hasan Akyildiz ◽  
Murat Citir ◽  
Cafer T. Yavuz ◽  
...  
Keyword(s):  
Membrane Filtration ◽  
Water Sources ◽  
Selective Removal ◽  
Network Structures ◽  
Organic Polymers ◽  
Great Affinity ◽  
Micro Pollutants

Micropollutants are found in all water sources, even after thorough treatments that include membrane filtration. We have developed swellable di-sulfide covalent organic polymers (COPs) with great affinity towards cationic textile micropollutants.

A Novel Heating Technology for Ultra-High Resolution Imaging in Electron Microscopes

2009 ◽  
Vol 17 (4) ◽  
pp. 50-55 ◽  
Author(s):  
Lawrence F. Allard ◽  
Wilbur C. Bigelow ◽  
Steven A. Bradley ◽  
Jingyue(Jimmy) Liu
Keyword(s):  
Elevated Temperatures ◽  
New Technology ◽  
Carbon Film ◽  
Elevated Pressure ◽  
Stable Operation ◽  
Heater Element ◽  
Resolution Imaging ◽  
Electron Microscopes ◽  
Differential Pumping

Capabilities for in-situ studies of materials at elevated temperatures and under gaseous environments have received increasing attention in recent years [1]. With the advent of electron microscopes that provide routine imaging at the atomic level (e.g. aberration-corrected TEM and STEM instruments), it is of particular interest to be able to record images at high temperatures while retaining the inherent resolution of the microscope; that is, the resolution is not limited by drift in the heating holder or other instabilities associated with its operation. A number of commercial and experimental heating devices have been used over the years; some holders are designed with miniature furnaces that heat entire grids [2], while a more recent development used a tiny spiral filament coated with a carbon film as the heater element [3]. These devices, while very useful for some applications (particularly in “environmental microscopes” that employ differential pumping to allow gases at some elevated pressure to be injected around the specimen), are invariably not as stable as might be desired for sub-Ångström imaging experiments. They are also limited by the speed at which the sample can be heated to temperature for stable operation. In collaboration with Protochips Inc. (Raleigh, NC), our laboratory is developing a novel new technology for in-situ heating experiments that overcomes a number of performance problems associated with standard heating stage technologies [4].

scholarly journals Behavior of Steel Slag Concrete Subjected to Elevated Temperature

2020 ◽  
Vol 9 (4) ◽  
pp. 1165-1170
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
High Temperatures ◽  
Elevated Temperatures ◽  
Coarse Aggregate ◽  
Steel Slag ◽  
Partial Replacement ◽  
High Porosity ◽  
Residual Mechanical Properties

Recycling of materials has become a major interest for engineers. At present, the amount of slag deposited in storage yard adds up to millions of tons/year leading to the occupation of farm land and serious pollution to the environment, as a result of the rapid growth in the steel industry. Steel slag is made at 1500- 1650°C having a honey comp shape with high porosity. Using steel slag as the natural aggregate with a lower waste material cost can be considered as a good alternative for sustainable constructions. The objective of this study is to evaluate the performance of residual mechanical properties of concrete with steel slag as coarse aggregate partial replacement after exposing to high temperatures .This study investigates the behavior of using granulated slag as partial or fully coarse aggregate replacement with different percentages of 0%, 15%, 30%, 50% and 100% in concrete when subjected to elevated temperatures. Six groups of concrete mixes were prepared using various replacement percentages of slag exposed to different temperatures of 400 °C, 600 °C and 800 °C for different durations of 1hr, 1.5hr and 2hr. Evaluation tests were compressive strength, tensile strength, and bond strength. The steel slag concrete mixes showed week workability lower than control mix. A systematic increasing of almost up to 21.7% in compressive strength, and 66.2% in tensile strength with increasing the percentage of steel slag replacement to 50%. And the results showed improvement on concrete residual mechanical properties after subjected to elevated temperatures with the increase of steel slag content. The findings of this study give an overview of the effect of steel slag coarse aggregate replacement on concrete after exposed to high temperatures.

Annealing Effects on Toughened Intra-Type Nanocomposites

2006 ◽  
Vol 45 ◽  
pp. 1632-1639 ◽  
Author(s):  
Hideo Awaji ◽  
Seong Min Choi
Keyword(s):  
Fracture Toughness ◽  
Elevated Temperatures ◽  
Volume Fraction ◽  
Process Zone ◽  
Nitrate Solution ◽  
Crack Tip ◽  
Hydrogen Atmosphere ◽  
Second Phase ◽  
High Porosity ◽  
The Matrix

Intra-type nanocomposites, in which nanosized second-phase particles are embedded within matrix grains, generate dislocations around the dispersed nanoparticles. The intra-type nanostructure induces a thermal expansion mismatch between the matrix and the dispersed particles, which will yield nanoscale stress distribution around the particles and generate lattice defects, such as dislocations. The dislocations of ceramics can be generated at elevated temperatures, become sessile dislocations at room temperature, and serve as nanocrack nuclei in highly stresses fields, e.g. at a main crack tip. The frontal process zone size ahead of a crack tip is expanded due to creation of nanocracks and hence the fracture toughness is improved. Annealing after sintered nanocomposites is important in controlling the dislocation activities. Appropriate annealing will disperse dislocations into the matrix grains. However, dislocations are sensitive to temperature, and higher temperature or longer annealing time result in dislocation disappearance and cause the reduction of the strength and fracture toughness of nanocomposites. In this study, commercially available γ-alumina agglomerated powder with high porosity was used to create the intra-type nanostructure. Nickel nitrate solution was infiltrated into nanopores of the γ-alumina agglomerates in vacuum. The alumina/nickel composite powder following reduction in hydrogen atmosphere was sintered using a pulse electric current sintering method. The volume fraction of nickel was about 3 vol %. After appropriate annealing, the highest fracture toughness was obtained to be 7.6 MPam1/2, which is two times higher than that of monolithic alumina.

Oriented Graphitic Carbon Film Grown by Mass-Selected Ion Beam Deposition at Elevated Temperatures

1999 ◽  
Vol 593 ◽  
Author(s):  
J. Kulik ◽  
G. Lempert ◽  
E. Grossman ◽  
Y. Lifshitz
Keyword(s):  
Elevated Temperatures ◽  
Ion Beam ◽  
Ambient Pressure ◽  
Carbon Film ◽  
Bragg Diffraction ◽  
Biaxial Stress ◽  
Layer Spacing ◽  
Ion Beam Deposition ◽  
Graphitic Layer ◽  
Beam Deposition

ABSTRACTMass-selected ion-beam deposition using 120 eV C+ ions has been used to grow a carbon film on a Si substrate held at 200° C. The structure of the film has been characterized by transmission electron microscopy and electron energy loss spectroscopy. The film is graphitic and highly oriented with the c-axis lying parallel to the substrate. Moreover, the film is under significant biaxial stress such that the graphitic layer spacing is reduced by 4% from that of ambient pressure graphite. This oriented structure evolves due to the mobility of the carbon atoms at 200 °C. The material is sufficiently crystalline on the nanometer scale so as to produce Bragg diffraction discs in a convergent beam electron diffraction pattern using a 2.5 nm probe.

Comparative Studies of Brown Coal and Lignin. II. The Action of Concentrated Alkali at Elevated Temperatures

1960 ◽  
Vol 13 (4) ◽  
pp. 567 ◽  
Author(s):  
BM Lynch ◽  
RA Durie
Keyword(s):  
Functional Groups ◽  
Brown Coal ◽  
Comparative Studies ◽  
Elevated Temperatures ◽  
Carboxyl Groups ◽  
Hydroxyl Groups ◽  
Brown Coals ◽  
Simple Chemical ◽  
Phenolic Hydroxyl Groups ◽  
Dihydric Phenol

A study was made of the products formed by treating brown coal or lignin with concentrated aqueous or ethanolic alkali at 200 �C. With brown coals a major redistribution of the oxygen-containing functional groups appeared to occur, because the products contained aliphatically linked carboxyl groups and aliphatic hydroxyl, as well as phenolic hydroxyl groups. The behaviour of lignin under the same conditions was less clear but sufficiently similar to that of brown coal to suggest that reactions of the same type were occurring in both cases. Reactions involving decarboxylation, ring scission of dihydric phenol structures, and subsequent hydrogenation are suggested tentatively as the main steps in the formation of the products. The results provide some additional evidence for the view that there is a simple chemical relation between Victorian brown coal and lignin.

Obtaining and Characterization of Porous Bodies Obtained by Gelatinization

2016 ◽  
Vol 881 ◽  
pp. 64-68
Author(s):  
Ana Gabriela Storion ◽  
Sylma Carvalho Maestrelli ◽  
Eric Ramalho Pinto ◽  
Juliana Cristina de Freitas ◽  
W.A. Mariano ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Porous Ceramics ◽  
Raw Material ◽  
Homogeneous Distribution ◽  
High Porosity ◽  
High Toughness ◽  
Porous Bodies ◽  
A New Technique ◽  
Solids Content

Porous ceramics have certain unique properties such as high toughness and resistance to heating at elevated temperatures. These properties make them products of great interest for applications on the field of filters and biomaterials. This paper proposes a new technique, called gelatinization, for processing this class of ceramics in order to obtain materials with more controlled pore size, plus a more homogeneous distribution. In order to check the efficiency of this technique, it was used as a raw material powders of calcined alumina and titania, previously characterized, mixed with unflavored gelatin, water and dispersant for holding the ceramic conformation. Three different formulations (with 40, 50 and 55% of solids content) were investigated using alumina and titania separately. The results indicated that the most suitable composition in terms of moldability was 55% of solids. It was also observed that the use of this technique to obtain bodies of high porosity is feasible; however, more detailed studies of sintering are necessary to obtain parts after firing in a close future. Due to the high porosity obtained the green, a detailed study of the sintering conditions is crucial to obtain parts with physical integrity.

High Thermo-Mechanical Stability in Polybenzoxazine Aerogels

2019 ◽  
Author(s):  
Sadeq Malakooti ◽  
Guoqiang Qin ◽  
Chandana Mandal ◽  
Chariklia Sotiriou-Leventis ◽  
Nicholas Leventis ◽  
...  
Keyword(s):  
Glass Transition ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Mechanical Performance ◽  
Mechanical Stability ◽  
Three Dimensional ◽  
High Porosity ◽  
Transition Temperatures ◽  
Glass Transition Temperatures ◽  
Structural Applications

Abstract Aerogels are three-dimensional networks of nanoparticles with high specific surface area and high porosity. Following the significant improvement on the mechanical strengths and ductility of traditional aerogels with polymer cross-linking (i.e., X-aerogels), the emergence of pure polymeric aerogels has enabled unprecedented aerogel applications such as ballistic armor protection, which is quite surprising for such low-density materials. However, generally low glass transition temperatures (Tg) of polymeric aerogels hinder their structural applicability at service temperatures above their Tg temperatures. Thereby, developing novel polymeric aerogels with high Tg temperatures is crucial for high-temperature structural applications. As phenolic resins, polybenzoxazines are heat-resistant and mechanically strong with high glass transition temperatures. In this study, polybenzoxazine aerogels have been successfully synthesized, and their mechanical properties at different densities and elevated temperatures have been investigated. High thermo-mechanical stability has been observed over the entire temperature range of interest (i.e., below 250 °C) for their quasi-static compressive properties such as Young’s modulus and compressive strength. Moreover, the storage and loss moduli in shear of the aerogels have been studied at different temperatures and frequencies. The strong mechanical performance of these aerogels at elevated temperatures makes them an important, inexpensive, and advanced material for high-temperature applications, competitive with significantly more expensive polyimides.

scholarly journals Characterization of Biochars Produced from Dairy Manure at High Pyrolysis Temperatures

Agronomy ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 634 ◽  
Author(s):  
Wen-Tien Tsai ◽  
Po-Cheng Huang ◽  
Yu-Quan Lin
Keyword(s):  
Surface Area ◽  
Elevated Temperatures ◽  
Chemical Properties ◽  
Hysteresis Loops ◽  
Calorific Value ◽  
Volatile Matter ◽  
Dairy Manure ◽  
Bet Surface Area ◽  
High Porosity ◽  
Pore Properties

In this work, the thermochemical analyses of dairy manure (DM), including the proximate analysis, ultimate (elemental) analysis, calorific value, thermogravimetric analysis (TGA), and inorganic elements, were studied to evaluate its potential for producing DM-based char (DMC) with high porosity. The results showed that the biomass should be an available precursor for producing biochar materials based on its high contents of carbon (42.63%) and volatile matter (79.55%). In order to characterize their pore properties, the DMC products produced at high pyrolysis temperatures (500–900°C) were analyzed using surface area and porosity analyzer, pycnometer, and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS). The values of pore properties for the DMC products increased with an increase in pyrolysis temperature, leading to more pore development and condensed aromatic cluster at elevated temperatures. Because of the microporous and mesoporous structures from the N2 adsorption–desorption isotherms with the hysteresis loops (H4 type), the Brunauer–Emmett–Teller (BET) surface area of the optimal biochar (DMC-900) was about 360 m2/g, which was higher than the data reported in the literature. The highly porous structure was also seen from the SEM observations. More significantly, the cation exchange capacity (CEC) of the optimal DMC product showed a high value of 57.5 ± 16.1 cmol/kg. Based on the excellent pore and chemical properties, the DMC product could be used as an effective amendment and/or adsorbent for the removal of pollutants from the soil media and/or fluid streams.

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