An open coaxial re-entrant microwave sensor has been used for the non-invasive and continuous monitoring of the sol–gel transition of physical gels characterized by different gelation mechanisms, solvents, compositions, and stabilities.
MAECTITE Chemical Fixation/Stabilization for Lead-Cadmium & Heavy Metals - Ca...Sevenson Environmental
This paper (presents typical approaches to the evaluation of the MAECTITE® chemical fixation/stabilization technology for use on lead and heavy metal bearing waste streams and materials ranging from treatability scale viability demonstrations to full-scale project applications. In addition, a brief technology history and technical overview is presented with analytical data supporting a range of applications to various lead bearing materials. Finally, two (2) full-scale projects are examined that depict a range of project magnitudes and complexities that incorporated common MAECTITE® technology application forms.
Investigation on Peritectic Layered Structures by Using the Binary Organic Co...CrimsonPublishersRDMS
Investigation on Peritectic Layered Structures by Using the Binary Organic Components TRIS-NPG as Model Substances for Metal-Like Solidification by JP Mogeritsch* in Crimson Publishers: Peer Reviewed Material Science Journals
Thermal Instability of Chemically Reacting Maxwell Fluid in a Horizontal Poro...IJERA Editor
The effect of chemical reaction on the linear stability of a viscoelastic fluid saturated horizontal densely-packed
porous layer is investigated. The viscoelastic properties are given by Maxwell constitutive relations. The porous
layer is cooled from the upper boundary while an adiabatic thermal boundary condition is imposed at the lower
boundary. Linear stability analysis suggests that there is a competition between the processes of viscous
relaxation and thermal diffusion that causes the first convective instability to be oscillatory rather than stationary.
The effect of Deborah number, Darcy-Prandtl number, normalized porosity, and the Frank-Kamenetskii number
on the stability of the system is investigated. Using a weighted residual method we calculate numerically the
convective thresholds for both stationary and oscillatory instability. The effects of viscoelasticity and chemical
reaction on the instability are emphasized. Some existing results are reproduced as the particular cases of the
present study.
MAECTITE Chemical Fixation/Stabilization for Lead-Cadmium & Heavy Metals - Ca...Sevenson Environmental
This paper (presents typical approaches to the evaluation of the MAECTITE® chemical fixation/stabilization technology for use on lead and heavy metal bearing waste streams and materials ranging from treatability scale viability demonstrations to full-scale project applications. In addition, a brief technology history and technical overview is presented with analytical data supporting a range of applications to various lead bearing materials. Finally, two (2) full-scale projects are examined that depict a range of project magnitudes and complexities that incorporated common MAECTITE® technology application forms.
Investigation on Peritectic Layered Structures by Using the Binary Organic Co...CrimsonPublishersRDMS
Investigation on Peritectic Layered Structures by Using the Binary Organic Components TRIS-NPG as Model Substances for Metal-Like Solidification by JP Mogeritsch* in Crimson Publishers: Peer Reviewed Material Science Journals
Thermal Instability of Chemically Reacting Maxwell Fluid in a Horizontal Poro...IJERA Editor
The effect of chemical reaction on the linear stability of a viscoelastic fluid saturated horizontal densely-packed
porous layer is investigated. The viscoelastic properties are given by Maxwell constitutive relations. The porous
layer is cooled from the upper boundary while an adiabatic thermal boundary condition is imposed at the lower
boundary. Linear stability analysis suggests that there is a competition between the processes of viscous
relaxation and thermal diffusion that causes the first convective instability to be oscillatory rather than stationary.
The effect of Deborah number, Darcy-Prandtl number, normalized porosity, and the Frank-Kamenetskii number
on the stability of the system is investigated. Using a weighted residual method we calculate numerically the
convective thresholds for both stationary and oscillatory instability. The effects of viscoelasticity and chemical
reaction on the instability are emphasized. Some existing results are reproduced as the particular cases of the
present study.
Evaluation of Compression Lines and Aging Effect on Clayey Soilsijtsrd
the intrinsic compression lines (ICL) obtained from this study can be used for studying the compressive behaviour of clayey soils due to aging effect. The results of oedometer tests of undisturbed samples were compared with the corresponding results of recomposed samples at room and high temperature and slurry samples. The values of compression index, Cc and pcpe*, where pc is the preconsolidation pressure and pe* is the equivalent pressure on the compression curve of slurry (1.5wL) sample when the sample yields, of undisturbed samples are different from those of recomposed samples due to the effect of soil structure. The compression lines of slurry samples obtained from the relationship of void index and effective overburden pressure can be expressed by the equations with sufficient accuracy. The values of void index difference, ? Ivy can be used to find the effect of the enhanced resistance to compression of natural soil structure. If ? Ivy value is high, there will be high maximum value of compression index after destroying the resistance of soil structure caused by the aging effect. The proposed compression index ratio, r"™ obtained from the Iv-log p relationship can be considered as a useful index to represent the aging effect. Htay Win"Evaluation of Compression Lines and Aging Effect on Clayey Soils" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-5 , August 2018, URL: http://www.ijtsrd.com/papers/ijtsrd18348.pdf http://www.ijtsrd.com/engineering/civil-engineering/18348/evaluation-of-compression-lines-and-aging-effect-on-clayey-soils/htay-win
Some Excess Properties of Ternary Liquid Mixture of Water, Methanol, Ethanol ...paperpublications3
Abstract: Densities and viscosities of ternary liquid mixtures of water, methanol, ethanol of volume by volume ratio of 1:1:1 have been measured at 308.15, 313.15., 318.15, 323.15, 328.15, K .From the density and viscosity data the values of various properties, Excess volume (VE) Excess viscosity (µE) and Excess Gibb’s free energy of activation of flow (ΔGE) have been determined. On the basis of the values of interaction parameters and various excess properties, the nature of molecular interactions between the components of mixtures has been explained.
Keywords: Viscosity, Liquids, Density, Ternary Mixture, Water, Methanol and Ethanol, Excess Volume, Excess Viscosity, Gibb’s Free Energy.
A series of siloxane based side chain liquid crystal polymers have been prepared with asystematic variation in spacer length. Nematic liquid crystal polymers possess large optical nonlinearities owing to their large refractive index anisotropy coupled with the collective molecular reorientation. All the polymer exhibited a smectic phase, for which the Nematic -isotropic transition temperature increased as the spacer length increased. Electro-optic measurements are used to evaluate the threshold voltages for this series of polymers. It is found that with increasing spacer length (n) of polymer the threshold voltage is lowered and that the variation of the threshold voltage arises from changes to the intrinsic curvature elasticity rather than to differences in orientational order. A simple model is used to indicate the origion of the effects observed which appear to arise from the constraints offered by the coupling of the mesogenic units to the polymer backbone.
The effect of temperature onthe micellization of an anionic surfactant in mix...iosrjce
IOSR Journal of Applied Chemistry (IOSR-JAC) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of applied chemistry and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in Chemical Science. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Role of αc–relaxation in high-temperature polymer deformation.
Proceedings of the American Society for Composites 2009-Twenty-Fourth Technical ConferenceWith the Canadian Association for Composite Structures and Materials (Joint Canadian-American International Conference), September 15-17, Newark, DE
Evaluation of Compression Lines and Aging Effect on Clayey Soilsijtsrd
the intrinsic compression lines (ICL) obtained from this study can be used for studying the compressive behaviour of clayey soils due to aging effect. The results of oedometer tests of undisturbed samples were compared with the corresponding results of recomposed samples at room and high temperature and slurry samples. The values of compression index, Cc and pcpe*, where pc is the preconsolidation pressure and pe* is the equivalent pressure on the compression curve of slurry (1.5wL) sample when the sample yields, of undisturbed samples are different from those of recomposed samples due to the effect of soil structure. The compression lines of slurry samples obtained from the relationship of void index and effective overburden pressure can be expressed by the equations with sufficient accuracy. The values of void index difference, ? Ivy can be used to find the effect of the enhanced resistance to compression of natural soil structure. If ? Ivy value is high, there will be high maximum value of compression index after destroying the resistance of soil structure caused by the aging effect. The proposed compression index ratio, r"™ obtained from the Iv-log p relationship can be considered as a useful index to represent the aging effect. Htay Win"Evaluation of Compression Lines and Aging Effect on Clayey Soils" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-5 , August 2018, URL: http://www.ijtsrd.com/papers/ijtsrd18348.pdf http://www.ijtsrd.com/engineering/civil-engineering/18348/evaluation-of-compression-lines-and-aging-effect-on-clayey-soils/htay-win
Some Excess Properties of Ternary Liquid Mixture of Water, Methanol, Ethanol ...paperpublications3
Abstract: Densities and viscosities of ternary liquid mixtures of water, methanol, ethanol of volume by volume ratio of 1:1:1 have been measured at 308.15, 313.15., 318.15, 323.15, 328.15, K .From the density and viscosity data the values of various properties, Excess volume (VE) Excess viscosity (µE) and Excess Gibb’s free energy of activation of flow (ΔGE) have been determined. On the basis of the values of interaction parameters and various excess properties, the nature of molecular interactions between the components of mixtures has been explained.
Keywords: Viscosity, Liquids, Density, Ternary Mixture, Water, Methanol and Ethanol, Excess Volume, Excess Viscosity, Gibb’s Free Energy.
The Formation of Two-Phase Periodic Structures-Crimson Publishers
Similar to Non invasive and continuous monitoring of the sol–gel phase transition of supramolecular gels using a fast (open-ended coaxial) microwave sensor
A series of siloxane based side chain liquid crystal polymers have been prepared with asystematic variation in spacer length. Nematic liquid crystal polymers possess large optical nonlinearities owing to their large refractive index anisotropy coupled with the collective molecular reorientation. All the polymer exhibited a smectic phase, for which the Nematic -isotropic transition temperature increased as the spacer length increased. Electro-optic measurements are used to evaluate the threshold voltages for this series of polymers. It is found that with increasing spacer length (n) of polymer the threshold voltage is lowered and that the variation of the threshold voltage arises from changes to the intrinsic curvature elasticity rather than to differences in orientational order. A simple model is used to indicate the origion of the effects observed which appear to arise from the constraints offered by the coupling of the mesogenic units to the polymer backbone.
The effect of temperature onthe micellization of an anionic surfactant in mix...iosrjce
IOSR Journal of Applied Chemistry (IOSR-JAC) is a double blind peer reviewed International Journal that provides rapid publication (within a month) of articles in all areas of applied chemistry and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in Chemical Science. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Role of αc–relaxation in high-temperature polymer deformation.
Proceedings of the American Society for Composites 2009-Twenty-Fourth Technical ConferenceWith the Canadian Association for Composite Structures and Materials (Joint Canadian-American International Conference), September 15-17, Newark, DE
Introduction
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Characterization and Humidity Sensing Application of WO3-SnO2 NanocompositeIOSR Journals
Studies on the sensitivity of the electrical resistance and fabrication process of SnO2 doped WO3
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Non invasive and continuous monitoring of the sol–gel phase transition of supramolecular gels using a fast (open-ended coaxial) microwave sensor
1. Non-invasive and continuous monitoring of the sol–gel phase transition of
supramolecular gels using a fast (open-ended coaxial) microwave sensor|
ISweek - Industry sourcing
An open coaxial re-entrant microwave sensor has been used for the non-invasive and
continuous monitoring of the sol–gel transition of physical gels characterized by different
gelation mechanisms, solvents, compositions, and stabilities. Comparison of
measurements by differential scanning calorimetry allowed the identification of the phase
transition by a change in the dielectric properties of the material over time.
Self-assembled viscoelastic gels of organic solvents (organogels), water (hydrogels) or
water–organic solvent mixtures (aqueous gels) have been recognized as promising
materials for bottom-up nanofabrication tools in various fields including biomedicine,
sensors, cosmetics, food, catalysis, and environmental remediation.As soft materials,
gels are continuous in structure and solid-like in rheological behavior. In contrast to
chemical gels, which are based on covalent bonds (usually cross-linked polymers unable
to redissolve), physical (also called supramolecular) gels are made of either low-
molecular-weight (LMW) compounds or polymers – so called gelators – through
extensive non-covalent interactions, predominantly hydrogen-bonding, van der Waals,
dipole–dipole, charge-transfer, donor–acceptor, π–π stacking and metal-coordination
interactions. Furthermore, systems based on both types of connections are also known.
The solid-like appearance of these gels is the result of the entrapment of the liquid (major
component) in the interstices of a solid 3D matrix of large surface area (minor
component), usually through surface tension and capillary forces. Remarkably, many gels
can immobilize up to 105
solvent molecules per molecule of gelator and increase the
viscosity of the medium by a factor of 1010
.
In the case of LMW gelators, the formation of the viscoelastic matrix is a consequence of
the entanglement of 1D supramolecular fibers (typically of micrometer scale lengths and
nanometer scale diameters), which is usually induced by cooling their hot isotropic
solutions to room temperature (RT). However, it should be noted that gelation of liquids at
RT or induced by ultrasound treatment instead of heating–cooling has also been
described. Due to the weakness of the non-covalent interactions that maintain the
dynamic supramolecular structure, physical gels are usually thermoreversible. Moreover,
the sol–gel (and/or gel–sol) phase transition could also be triggered by other stimuli such
as pH, light irradiation or ionic strength if the gelator molecule possesses appropriate
structural moieties for recognition. It is also important to recognize that the metastable
nature of physical gels derives from an elusive equilibrium between dissolution and
crystallization, which has stimulated numerous studies and applications in the field of
crystal engineering during the last few years.
Due to the brittleness of these materials, it is usually easier to monitor the gel–sol
transition rather than the sol–gel for the construction of phase diagrams according to both
the gel–sol transition temperature (TGS) and the sol–gel transition temperature (TSG).
Among different techniques, rheology, NMR spectroscopy and conventional differential
2. scanning calorimetry (DSC) are the most common and accurate methods used so far for
this kind of study, albeit they normally suffer from the disadvantages of being relatively
time consuming and requiring the use of very expensive equipments and trained
personnel. Techniques of higher specificity such as ESR, NIR and fluorescence
spectroscopy have also been used to characterize the sol–gel transitions of colloids.17
On
the other hand, dielectric measurements have also been used to determine sol–gel
transitions, usually below a few kHz. At these frequencies the dielectric properties are
normally related to the conductive nature of the material and this quantity becomes (less)
sensitive to chemical changes that occur at gelation.Dielectric measurements at
microwave frequencies, however, are very sensitive to the mobility of molecules in the gel
(especially when some water dipoles are involved). Therefore, the use of the mobility of
the molecular structure through dielectric properties provides a direct (and in situ)
measurement of the chemical and physical state of the matter.Changes in dielectric
parameters can be related to critical points in different material processes, such as cure
reaction onset, gelation, end-of-cure, build-up of the glass-transition temperature, etc.For
example, a microwave system designed for adhesive cure monitoring has been
previously described by some of us where in situ dielectric measurements correlate very
well with conventional measurement techniques such as DSC, combining accuracy and
rate with simplicity and an affordable cost.
This communication presents a microwave non-destructive system for monitoring the
sol–gel transition process of supramolecular gels (Fig. 1A). A microwave sensor adapted
to a standard pyrex vial containing the precursor isotropic solution allows in situ
measurements of dielectric properties in order to distinguish the changes over time and
temperature.
Fig. 1B shows a picture of the portable microwave device used to conduct the dielectric
measurements. The system comprises a microwave sensor, a microwave transmitter and
receiver (from 1.5 to 2.5 GHz) and a control unit to provide real-time information about
the gelation progress without interfering with the reaction. The precursor isotropic
solution is introduced in a pyrex vial and placed inside an open coaxial re-entrant
(microwave) cavity sensor. When the low-intensity electromagnetic waves penetrate into
the material, its molecules tend to orient with the (applied) external field and the material
gains certain polarization, reflecting the back part of the microwave signal from the
sensor. This reflected signal is measured continuously to determine the resonance
frequency and quality factor of the sensor during gelation to monitor the transition
process. Fig. 1C and D show a typical response of the reflected signal in the microwave
cavity sensor in the imaginary plane (Smith chart) or in magnitude representation of a
gelation experiment at a given temperature. We have reported elsewhere the
fundamental details of the microwave system with a different sensor head.
Fig. 2 shows the library of known gelators that we prepared (ESI) to test the ability of the
microwave sensor to monitor the sol–gel transition of physical gels. The library included
single LMW gelators (1–8) as well as bicomponent (9) and multicomponent gelator
3. systems (10). A number of gels with different solvents and compositions could be easily
obtained from this library at well-defined concentrations. Moreover, N,N′-dibenzoyl-L-
cystine (6) was included in this study for the preparation of aqueous gels. Azobenzene-
containing peptide 8 was selected because its phase transition can be triggered either
thermally or photochemically. Besides the classical heating–cooling treatment needed for
the formation of thermoreversible physical gels made from solid compounds 1–8, gelator
systems 9 and 10 enable sol–gel phase transitions at RT and well below RT, respectively.
In the case of 9, DMF stock solutions of oxalic acid dihydrate and copper(II) acetate
monohydrate were mixed at RT to form the corresponding organogel. Multicomponent
solution 10 constitutes a special system used to form organogels at low temperatures
upon addition of a small amount of this solution to a suitable organic solvent (ESI). In
contrast to the gels obtained from 1–8, those derived from 9–10 are not thermoreversible
despite the non-covalent interactions involved in the gelation process. Moreover, gels
made from 10 eventually undergo subsequent transition to a thermodynamically most
stable crystallization phase This collection of gelators offered a versatile scenario for the
proof-of-concept of the detection of the sol–gel transition in physical gels by continuously
monitoring the dielectric properties of the materials.
The isotropic solutions of the gelators were prepared as previously reported (ESI).
Preliminary experiments with solutions prepared at different concentrations of a LMW
gelator showed a response of the microwave sensor to viscosity changes of the medium
(ESI). On the basis of this observation, the dielectric properties of the sol–gel transition
were continuously monitored at microwave frequencies and the obtained profile was
correlated with the actual temperature of the material (ESI). Moreover, DSC thermograms
were recorded separately for model systems in order to draw meaningful comparisons
between the change in the dielectric properties of the material and the exothermic effect
associated with the sol–gel transition. The temperature profiles during the sol–gel period
were constructed independently by means of a thermocouple probe (∅ 0.1 mm) centrally
placed inside the mixture. We confirmed that the use of this probe did not affect the
gelation kinetics. After each measurement, the state of the material was examined by the
“stable-to-inversion” test, and the gel condition of model samples that did not show
gravitational flow upon turning the vial upside-down was also confirmed by oscillatory
rheological measurements (ESI).
The results indicated a good correlation between the different techniques to recognize
the sol–gel transition under different conditions (e.g., solvent nature, concentration, and
gelator structure). Finally, preliminary experiments have shown that the microwave
sensor could also be used to detect the melting (gel–sol) transitions as we could record
the variation of the dielectric properties of the material at single points (upon heating
separately) and correlate marked changes with the TGS determined by DSC or the inverse
flow method (ESI).
ISweek(http://www.isweek.com/)- Industry sourcing & Wholesale industrial products