scholarly journals Membrane-Based Separation of Phenol/Water Mixtures Using Ionically and Covalently Cross-Linked Ethylene-Methacrylic Acid Copolymers

2008 ◽  
Vol 2008 ◽  
pp. 1-12 ◽  
Author(s):  
Alexander Mixa ◽  
Claudia Staudt
Keyword(s):  
Methacrylic Acid ◽  
Elevated Temperatures ◽  
Type Equation ◽  
Enrichment Factors ◽  
Cross Linking ◽  
Temperature Dependent ◽  
Monomer Content ◽  
Phenol Water ◽  
Feed Temperature ◽  
Acetyl Acetonate

Membrane-based separation of phenol/water mixtures with concentrations of phenol between 3 wt% and 8 wt% in the feed has been performed with nonmodified as well as cross-linked ethylene-methacrylic acid (E-MAA) copolymers with different amounts of methacrylic acid. As cross-linking agents, aluminium acetyl acetonate, which leads to ionically cross-linked membranes, and 2,3,5,6-tetramethyl-1,4-phenylene diamine and glycerine digycidether, leading to covalently cross-linked membranes, have been used. Generally, it was found that with increasing phenol content in the feed, the total flux is increasing whereas the enrichment factor is decreasing. Using nonmodified membranes with higher methacrylic acid monomer content in the polymer, lower fluxes and higher enrichment factors were observed. Investigation of different cross-linked membranes showed that with high phenol concentration in the feed, ionic cross-linking seems to be very promising. Furthermore, variation of feed temperature shows that ionically cross-linked membranes reached higher fluxes as well as higher enrichment factors at elevated temperatures. The temperature-dependent data were fitted based on an Arrhenius-type equation, and activation energies for the permeation of phenol and water through the membrane were calculated.

scholarly journals Physical networks from entropy-driven non-covalent interactions

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Anthony C. Yu ◽  
Huada Lian ◽  
Xian Kong ◽  
Hector Lopez Hernandez ◽  
Jian Qin ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Dissociation Rate ◽  
Mathematical Framework ◽  
Temperature Dependent ◽  
Nanoparticle Interactions ◽  
Temperature Superposition ◽  
Non Covalent Interactions ◽  
Time Temperature Superposition ◽  
Covalent Interactions ◽  
Physical Crosslinking

AbstractPhysical networks typically employ enthalpy-dominated crosslinking interactions that become more dynamic at elevated temperatures, leading to network softening. Moreover, standard mathematical frameworks such as time-temperature superposition assume network softening and faster dynamics at elevated temperatures. Yet, deriving a mathematical framework connecting the crosslinking thermodynamics to the temperature-dependent viscoelasticity of physical networks suggests the possibility for entropy-driven crosslinking interactions to provide alternative temperature dependencies. This framework illustrates that temperature negligibly affects crosslink density in reported systems, but drastically influences crosslink dynamics. While the dissociation rate of enthalpy-driven crosslinks is accelerated at elevated temperatures, the dissociation rate of entropy-driven crosslinks is negligibly affected or even slowed under these conditions. Here we report an entropy-driven physical network based on polymer-nanoparticle interactions that exhibits mechanical properties that are invariant with temperature. These studies provide a foundation for designing and characterizing entropy-driven physical crosslinking motifs and demonstrate how these physical networks access thermal properties that are not observed in current physical networks.

Conductivity-Temperature Dependent Studies on MG49 Doped Lithium Triflate Salt

2015 ◽  
Vol 1107 ◽  
pp. 181-186
Author(s):  
Zaidatul Salwa Mahmud ◽  
N.H.M. Zaki ◽  
R. Zakaria ◽  
Mohamad Faizul Yahya ◽  
Ab Malik Marwan Ali
Keyword(s):  
Ionic Conductivity ◽  
Elevated Temperatures ◽  
Ethylene Carbonate ◽  
Ionic Mobility ◽  
Ionic Conductors ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
Lithium Triflate ◽  
Mobility Of Charge Carriers ◽  
Solution Cast

This paper reports on the conductivity-temperature studies of gel polymer electrolytes (GPEs) based on 49% poly (methyl methacrylate) grafted-natural rubber (MG49) doped with lithium triflate salt (LiTf) and plasticized with ethylene carbonate (EC). The GPE films are prepared by solution cast technique. The X-ray diffraction (XRD) studies reveal the polymer electrolyte systems are amorphous. AC impedance spectroscopy is carried out in the temperature range between 303 and 373 K. The magnitudes of conductivity observed are strongly dependent on salt concentration and temperature. The high ionic conductivity at elevated temperatures of GPE is attributed to the high ionic mobility of charge carriers. The ionic migration is seen to follow the VTF behavior and approaches to Arrhenius rule at high and low at temperature. Ionic conductivity relaxation appears to be a characteristic of the ionic polarization and the modulus formalism studies confirmed the GPEs in the present investigation are ionic conductors.

Simplified Analysis Methods for Primary Load Designs at Elevated Temperatures

2011 ◽  
Author(s):  
Peter Carter ◽  
T.-L. Sam Sham ◽  
R. I. Jetter
Keyword(s):  
Elevated Temperatures ◽  
Design Procedure ◽  
Inelastic Strain ◽  
Temperature Dependent ◽  
Perfectly Plastic ◽  
Reference Stress ◽  
Analysis Methods ◽  
Elastic Perfectly Plastic ◽  
Further Development ◽  
Primary Load

The use of “simplified” (reference stress) analysis methods is discussed and illustrated for primary load high temperature design. Elastic methods are the basis of the ASME Section III, Subsection NH primary load design procedure. There are practical drawbacks with this current NH approach, particularly for complex geometries and temperature gradients. The paper describes an approach which addresses these difficulties through the use of temperature-dependent elastic, perfectly-plastic analysis. Traditionally difficulties associated with discontinuity stresses, inelastic strain concentrations and multiaxiality are addressed. A procedure is identified to provide insight into how this approach could be implemented. Though preliminary in nature, it is intended to provide a basis for further development and eventual Code adaptation.

scholarly journals Phenol Novalac Epoxy-modified unsaturated polyester hybrid networks by Silica Nanoparticles/ and Cross linking with Silane Compounds

2020 ◽  
Vol 1 (2) ◽  
pp. 28-32
Keyword(s):  
Epoxy Resin ◽  
Silica Nanoparticles ◽  
Elevated Temperatures ◽  
Unsaturated Polyester ◽  
Low Cost ◽  
Physical And Mechanical Properties ◽  
Hybrid Networks ◽  
Azo Compounds ◽  
Cross Linking ◽  
Chemical Attributes

In this study epoxy phenol novalac resin which consists of silica nanoparticles and unsaturated poly ester resin linked to the Silane and cross linking to that structure and also parameters affecting the processes involved have been evaluated. Cross linking in phenol novalac epoxy resins effects on many properties such as thermal, electrical, mechanical and chemical attributes especially in elevated temperatures. Silane cross-linking’s in phenol novalac epoxy resin with respect to other methods like proxiding, irradiation and utilization of Azo compounds, looks to be a very simple and low cost route, which makes it very encouraging for various industries. Unsaturated poly ester resin is compatible with phenol novalac epoxy resin and also creates some cross-linking and as far as tri methoxy Silane is added to the mentioned resin, its thermal, physical and mechanical properties are optimized. In this literature impact, tension, glass transition temperature, humidity absorption, FTIR and Scanning electron microscopy (SEM) tests were done and the results revealed that as the cross-linking occurs, tension in rupture region increases. This increase is more common at elevated temperatures. The growth in content of silica nanoparticles leads to a drop in water permeability of phenol novalac epoxy resin nanocomposite which contains unsaturated poly ester resin.

scholarly journals Determining the material model at elevated temperatures with different strain rates and simulating the warm forming process for Mg alloy AZ31B sheet

2015 ◽  
Vol 18 (2) ◽  
pp. 149-158
Author(s):  
Thien Tich Truong ◽  
Long Thanh Nguyen ◽  
Binh Nguyen Thanh Vu ◽  
Hien Thai Nguyen
Keyword(s):  
Magnesium Alloy ◽  
Constitutive Equations ◽  
Elevated Temperatures ◽  
Material Model ◽  
Alloy Sheet ◽  
Strain Rates ◽  
Functional Requirements ◽  
Temperature Dependent ◽  
Forming Process ◽  
Az31b Alloy

Magnesium alloy is one of lightweight alloys has been studied more extensively today. Because weight reduction while maintaining functional requirements is one of the major goals in industries in order to save materials, energy and costs, etc. Its density is about 2/3 of aluminum and 1/4 of steel.The material used in this study is commercial AZ31B magnesium alloy sheet which includes 3% Al and 1% Zn. However, due to HCP (Hexagonal Close Packed) crystal structure, magnesium alloy has limited ductility and poor formability at room temperature. But its ductility and formability will be improved clearly at elevated temperature. From the data of tensile testing, the constitutive equations of AZ31B was approximated using the Ramgberg-Osgood model with temperature dependent parameters to fit in the experiment results in tensile test. Yield locus are also drawn in plane stress σ1- σ2 with different yield criteria such as Hill48, Drucker Prager, Logan Hosford, Y. W. Yoon 2013 and particular Barlat 2000 criteria with temperature dependent parameters. Applying these constitutive equations were determined at various temperatures and different strain rates, the finite element simulation stamping process for AZ31B alloy sheet by software PAM- STAMP 2G 2012, to verify the model materials and the constitutive equations.

scholarly journals A model for ultimate bearing capacity of piles in unsaturated soils under elevated temperatures

2020 ◽  
Vol 205 ◽  
pp. 05003
Author(s):  
Sannith Kumar Thota ◽  
Farshid Vahedifard
Keyword(s):  
Bearing Capacity ◽  
Unsaturated Soils ◽  
Elevated Temperatures ◽  
Skin Resistance ◽  
Ultimate Bearing Capacity ◽  
Temperature Dependent ◽  
Deep Foundation ◽  
Energy Applications ◽  
Temperature Dependent Model ◽  
Pile Resistance

Geo-energy applications such as energy piles can expose unsaturated, deep foundation soils to elevated temperatures. This paper presents a closed-form equation for the ultimate bearing capacity of piles in unsaturated soils subject to elevated temperatures under drained conditions. For this purpose, a temperature-dependent effective stress model was incorporated into calculations of skin resistance and end bearing resistance of piles. The proposed temperature-dependent model is an extension of the modified β method for determining the ultimate pile bearing capacity of unsaturated soils under drained conditions. Employing the proposed model, a parametric study was carried out to evaluate the ultimate pile bearing capacity for hypothetical clay and silt soils at temperatures ranging from 25 °C to 55 °C. For both clay and silt, the results indicated that the ultimate pile bearing capacity varies with an increase in temperature. Different trends with temperature were observed for clay and silt. A monotonic increase in pile resistance was observed in clays. For silt, the pile resistance increased at relatively low matric suction whereas it decreased at higher matric suctions.

The Temperature-Dependent Ideal Shear Strength of Solid Single Crystals

2018 ◽  
Vol 85 (3) ◽  
Author(s):  
Tianbao Cheng ◽  
Daining Fang ◽  
Yazheng Yang
Keyword(s):  
Shear Strength ◽  
Theoretical Model ◽  
Melting Point ◽  
Single Crystals ◽  
Elevated Temperatures ◽  
Absolute Zero ◽  
Temperature Dependent ◽  
Temperature Changes ◽  
First Time ◽  
The Ideal

Knowledge of the ideal shear strength of solid single crystals is of fundamental importance. However, it is very hard to determine this quantity at finite temperatures. In this work, a theoretical model for the temperature-dependent ideal shear strength of solid single crystals is established in the view of energy. To test the drawn model, the ideal shear properties of Al, Cu, and Ni single crystals are calculated and compared with that existing in the literature. The study shows that the ideal shear strength first remains approximately constant and then decreases almost linearly as temperature changes from absolute zero to melting point. As an example of application, the “brittleness parameter” of solids at elevated temperatures is quantitatively characterized for the first time.

Insight into Channel Conduction Mechanisms of 4H-SiC(0001) MOSFET Based on Temperature-Dependent Hall Effect Measurement

2020 ◽  
Vol 1004 ◽  
pp. 620-626
Author(s):  
Hironori Takeda ◽  
Mitsuru Sometani ◽  
Takuji Hosoi ◽  
Takayoshi Shimura ◽  
Hiroshi Yano ◽  
...  
Keyword(s):  
Hall Effect ◽  
Field Effect ◽  
Elevated Temperatures ◽  
Field Effect Transistors ◽  
Free Carrier ◽  
Oxide Semiconductor ◽  
Thermal Excitation ◽  
Temperature Dependent ◽  
Conduction Mechanisms ◽  
The Impact

Temperature-dependent Hall effect measurements were conducted to investigate the channel conduction mechanisms of 4H-SiC metal-oxide-semiconductor field-effect transistors (MOSFETs). This method allows us to discriminate the impact of the density of mobile (free) carriers in the inversion channels and their net mobility on the performance of SiC MOSFETs. It was found that, while the free carrier ratio of SiC MOSFETs with conventional gate oxides formed by dry oxidation is below 4% at 300 K, increasing the free carrier ratio due to thermal excitation of trapped electrons from SiO2/SiC interfaces leads to an unusual improvement in the field-effect mobility of SiC MOSFETs at elevated temperatures. Specifically, a significant increase in free carrier density surpasses the mobility degradation caused by phonon scattering for thermally grown SiO2/SiC interfaces. It was also found that, although nitrogen incorporation in SiO2/SiC interfaces increases the free carrier ratio typically up to around 30%, introduction of an additional scattering factor associated with interface nitridation compensates for the moderate amount of thermally generated mobile carriers at high temperatures, indicating a fundamental drawback of nitridation of SiO2/SiC interfaces. On the basis of these findings, we discuss the channel conduction mechanisms of SiC MOSFETs.

Near-Field Radiative Transfer Between Heavily Doped SiGe at Elevated Temperatures

2011 ◽  
Author(s):  
Z. M. Zhang ◽  
E. T. Enikov ◽  
T. Makansi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
State Energy ◽  
Radiative Heat ◽  
Elevated Temperatures ◽  
Near Field ◽  
Temperature Dependent ◽  
Heavily Doped ◽  
The Heat Transfer Coefficient

SiGe alloys represent an important type of high-temperature semiconductor material for solid-state energy conversion. In the present study, the near-field radiative heat transfer between heavily doped SiGe plates is investigated. A dielectric function model is formulated based on the previously reported room-temperature mobility and temperature-dependent electric resistivity of several silicon-rich alloys with different doping type and concentration. The fluctuational electrodynamics is used to evaluate the near-field noncontact heat transfer coefficient. The variation of the heat transfer coefficient with doping concentration and temperature is explained according to the change in the optical constants and in the spectral distribution of the near-field heat flux.

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