Freezing/Melting Transition of Physically Restricted n-Decane

1994 ◽  
Vol 366 ◽  
Author(s):  
P. M. Hoffmann ◽  
V. M. Malhotra
Keyword(s):  
Large Fraction ◽  
Porous Silica ◽  
Melting Transition ◽  
Scanning Calorimetry ◽  
Freezing Transition ◽  
Dsc Measurements ◽  
Linear Behavior ◽  
Alkane Chain ◽  
Two Peaks ◽  
Interesting Behavior

ABSTRACTWe undertook differential scanning calorimetry (DSC) measurements at 170 K < T < 300 K on n-decane, physically confined in 8 nm (= diameter D) porous silica derivatized with various functional groups, to understand how surface structure of the confining media affects the freezing or melting transition of the n-decane. Though we observed a typical depression (ΔT) in the freezing or melting transition temperature of the physically confined decane, our results failed to manifest usual linear dependence of ΔT on D−1 when the expected contraction in D, due to the presence of aminopropyl-, hexyl-, phenyl- or trimethyl-groups on the silica surface, was taken into account. However, it is worth noting that a linear behavior was observed between ΔT and D−1 if only alkane-chain derivatized hosts were considered. Our results also indicate that a large fraction of physically confined n-decane (35 to 70 %), depending on the host silica, does not participate either in the melting or freezing transition. The most interesting behavior observed in the present study is the occurrence of the unusual two peaks associated with the freezing transition of physically confined decane. This bimodal behavior is strongly dependent on the chemistry of the confining silica host's surface.

Effects of Surfaces on the Melting/Freezing Behavior of Fluids in Derivatized- and Nude-Porous Silica

1992 ◽  
Vol 290 ◽  
Author(s):  
V. K. Malhotra ◽  
R. Mu ◽  
A. Natarajan
Keyword(s):  
Differential Scanning Calorimetry ◽  
Surface Structure ◽  
Pore Radius ◽  
Porous Silica ◽  
Freezing Behavior ◽  
Melting Transition ◽  
Scanning Calorimetry ◽  
Thermodynamic Behavior ◽  
Dsc Measurements ◽  
Effective Pore Radius

AbstractComparative differential scanning calorimetry (DSC) measurements were made at 200 K < T < 310 K on geometrically restricted cyclohexane and n-decane in nude-, trimethyl derivatized-, and hexyl derivatized-porous (Rp = 4 nm) silica with a view to determine how the surface structure of the confining media affects the thermodynamic behavior of the restricted fluid. Our results suggest that, irrespective of the fact that both trimethyl derivatized- and hexyl derivatized-silica have methyl terminal groups, the freezing or melting transition of cyclohexane is much more depressed in trimethyl derivatized-silica than in hexyl derivatized- or nude-silica. This is not the case for n-decane where the depression in the melting transition is consistent with the fact that the effective pore radius of the hexyl derivatized-silica is smaller than the trimethyl derivatized- or nude-silica.

scholarly journals Phase Transitions of N-(4-methoxybenzylidene)-4-butylaniline (MBBA) Confined within Mesoporous Silica

Crystals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 792
Author(s):  
Takehisa Yoshimi ◽  
Ayumi Shima ◽  
Shoko Hagiwara-Norifusa ◽  
Takayuki Sugimoto ◽  
Atsushi Nagoe ◽  
...  
Keyword(s):  
Phase Transition ◽  
Nematic Phase ◽  
Three Dimensional ◽  
Porous Silica ◽  
Temperature Shift ◽  
Thermal Anomaly ◽  
Scanning Calorimetry ◽  
Isotropic Liquid ◽  
One Dimensional ◽  
Dsc Measurements

We have used differential scanning calorimetry (DSC) to investigate the phase transition of a liquid crystal, N-(4-methoxybenzylidene)-4-butylaniline (MBBA), confined within porous silica materials with one- and three-dimensional pore architectures. Each phase-transition temperature of the confined MBBA linearly decreased with the inverse pore size compared with that of bulk MBBA. However, the degree of temperature shift varied owing to differences in the pore architectures. In addition, when MBBA was confined within one-dimensional pores, the thermal anomaly associated with the phase transition from the nematic phase to the isotropic liquid phase was not observed in the DSC measurements.

Comparative Thermodynamic Behavior of Physically Restricted Cyclohexane and Cyclohexanone in Porous Silica

1998 ◽  
Vol 543 ◽  
Author(s):  
S. Amanuel ◽  
V. M. Malhotra
Keyword(s):  
Transition Temperature ◽  
Thermodynamic Properties ◽  
Differential Scanning Calorimeter ◽  
Pore Radius ◽  
Porous Silica ◽  
Melting Transition ◽  
Confined Fluids ◽  
Bulk Fluid ◽  
Host Interactions ◽  
Dsc Measurements

AbstractWe undertook comparative differential scanning calorimeter (DSC) measurements on cyclohexane (C6H12) and cyclohexanone (C6H10O), physically confined in porous silica of pore radius 4, 7.5, 15, 30, and 62.5 nim, with a view to ascertain how guest fluid-surface host interactions affected the thermodynamic properties of the confined fluids. Our results can be summarized as follows: (a) No distinct signature of freezing or melting transition was observed for the physically confined cyclohexanone, irrespective of whether the bulk was present outside the pores. However, this was not the case for cyclohexane. (b) The solid-to-solid transition temperature of cyclohexane and cyclohexanone inversely scaled with the pore radius of the host porous silica. (c) The cubic-to-orthorhombic transition of cyclohexanone was strongly influenced by whether the bulk fluid was present outside the pores. In the absence of the bulk, the transition temperature was considerably suppressed relative to the bulk transition temperature. However, in the presence of the bulk, the confined and the bulk transitions occurred at the same temperature.

Nanocrystal superlattices that exhibit improved order on heating: an example of inverse melting?

2015 ◽  
Vol 181 ◽  
pp. 181-192 ◽  
Author(s):  
Yixuan Yu ◽  
Avni Jain ◽  
Adrien Guillaussier ◽  
Vikas Reddy Voggu ◽  
Thomas M. Truskett ◽  
...  
Keyword(s):  
Structural Transition ◽  
Grazing Incidence ◽  
Melting Transition ◽  
Transition Temperatures ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Dsc Measurements ◽  
X Ray Scattering ◽  
Nanocrystal Superlattices ◽  
Melting And Solidification

Grazing incidence small angle X-ray scattering (GISAXS) measurements reveal that superlattices of 1.7 nm diameter, gold (Au) nanocrystals capped with octadecanethiol become significantly more ordered when heated to moderate temperatures (50–60 °C). This enhancement in order is reversible and the superlattice returns to its initially disordered structure when cooled back to room temperature. Disorder–order transition temperatures were estimated from the GISAXS data using the Hansen–Verlet criterion. Differential scanning calorimetry (DSC) measurements of the superlattices exhibited exotherms (associated with disordering during cooling) and endotherms (associated with ordering during heating) near the transition temperatures. The superlattice transition temperatures also correspond approximately to the melting and solidification points of octadecanethiol. Therefore, it appears that a change in capping ligand packing that occurs upon ligand melting underlies the structural transition of the superlattices. We liken the heat-induced ordering of the superlattices to an inverse melting transition.

A Vibrational Investigation of Crystal Nucleation and Growth from a Physically Confined and Supercooled Liquid

1994 ◽  
Vol 366 ◽  
Author(s):  
R. Mu ◽  
D. O. Henderson ◽  
Z. Pan ◽  
Y. Xue
Keyword(s):  
Solid Phase ◽  
Porous Silica ◽  
Supercooled Liquid ◽  
Nucleation And Growth ◽  
Crystal Nucleation ◽  
Melting Transition ◽  
Temperature Dependent ◽  
Freezing Transition ◽  
20 Nm

ABSTRACTTemperature dependent Raman measurements were conducted on bulk and the confined 2,4,6-trinitrotoluene (TNT) in 2.5, 5, 10, and 20 nm porous silica. Two bands at 23 and 190 cm−1 were chosen to evaluate the structure and the melting and freezing transitions of the confined TNT in pores. The results show that the solid phase TNT confined in larger pores (dp > 5 nm) forms conventional solid TNT structure, while the TNT restricted in small pores has no freezing and melting transition characteristics. The results also suggest that the freezing transition of the confined TNT starts at the pore center and the confined TNT maintains its interconnectivity during the freezing transition.

scholarly journals Polypropylene/Lignin/POSS Nanocomposites: Thermal and Wettability Properties, Application in Water Remediation

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3950
Author(s):  
Abeer Alassod ◽  
Syed Rashedul Islam ◽  
Mina Shahriari Khalaji ◽  
Rogers Tusiime ◽  
Wanzhen Huang ◽  
...  
Keyword(s):  
Organic Liquid ◽  
Contact Angles ◽  
Water Remediation ◽  
Scanning Calorimetry ◽  
Water Contact ◽  
Thermally Induced ◽  
Dsc Measurements ◽  
Infrared Measurement ◽  
Oligomeric Silsesquioxane ◽  
Tga And Dsc

Compositing is an interesting strategy that has always been employed to introduce or enhance desired functionalities in material systems. In this paper, sponges containing polypropylene, lignin, and octavinyl-polyhedral oligomeric silsesquioxane (OV-POSS) were successfully prepared via an easy and elegant strategy called thermally induced phase separation (TIPS). To fully explore the behaviour of different components of prepared sponges, properties were characterized by a thermogravimetric analyser (TGA), differential scanning calorimetry (DSC), Fourier transform infrared measurement (FTIR), and scanning electron microscopy (SEM). Furthermore, wettability properties toward an organic liquid and oil were investigated. The FTIR analysis confirmed the chemical modification of the components. TGA and DSC measurements revealed thermal stability was much better with an increase in OV-POSS content. OV-POSS modified sponges exhibited ultra-hydrophobicity and high oleophilicity with water contact angles of more than 125°. The SEM revealed that POSS molecules acted as a support for reduced surface roughness. Moreover, OV-POSS-based blend sponges showed higher sorption capacities compared with other blend sponges without OV-POSS. The new blend sponges demonstrated a potential for use as sorbent engineering materials in water remediation.

Investigations on the polymorphism and pseudopolymorphism of clobetasone butyrate

2011 ◽  
Vol 76 (5) ◽  
pp. 553-566
Author(s):  
Christian Näther ◽  
Inke Jeß
Keyword(s):  
Room Temperature ◽  
Polymorphic Form ◽  
Stable Form ◽  
Scanning Calorimetry ◽  
Amorphous Form ◽  
Space Group ◽  
Dsc Measurements ◽  
Independent Molecules ◽  
Solvent Molecules ◽  
Similar Conformation

Clobetasone butyrate was investigated for polymorphism and pseudopolymorphism. Solvent mediated conversion experiments reveal that the commercially available form I represent the thermodynamically most stable form at room temperature and DSC measurements shows that it should also be the most stable form until melting. Form I crystallizes in space groupP212121with three crystallographically independent molecules of similar conformation. From methanol an additional pseudo polymorphic form was discovered. In the crystal structure (space groupP212121) the solvent molecules are connected to the clobetasone butyrate molecules by O–H···O hydrogen bonding. Investigations of the solvate using thermogravimetry, differential thermoanalysis as well as differential scanning calorimetry proves, that on solvent removal an amorphous form is obtained that crystallizes into form I on further heating.

Effects of Aging on the Microstructure and Phase Transformation Behavior of Cu-Al-Mn Shape Memory Alloy

2021 ◽  
Vol 882 ◽  
pp. 21-27
Author(s):  
Seyed Veghar Seyedmohammadi ◽  
Amin Radi ◽  
Guney Guven Yapici
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Aging Treatment ◽  
Scanning Calorimetry ◽  
Dsc Measurements ◽  
Peak Aged Condition ◽  
Peak Aged ◽  
Rolled Condition ◽  
The One ◽  
Effects Of Aging

In the present work, the effects of artificial aging treatment on the transformation temperatures and hardness of Cu-Al-Mn shape memory alloy have been investigated. The aging processes have been performed on the one-time re-melted and 90% rolled samples. Differential scanning calorimetry reveals that reverse transformation is present for the re-melted sample which is aged at 400°C. However, in 90% rolled condition, this transformation takes place at 200°C and 300°C. Hardness examination shows that the aged specimens possess higher values in hardness in comparison to un-aged samples at all studied temperatures. Although, the peak-aged condition was demonstrated at 300°C for the re-melted sample, the rolled sample displayed increased hardness levels up to 500°C. Based on the DSC measurements and microstructural observations, it can be asserted that the thermo-mechanical processing including rolling plus aging at 300°C provides favorable transformation characteristics for shape memory behavior.

scholarly journals A Facile Synthesis and Characterization of Highly Crystalline Submicro-Sized BiFeO3

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3035
Author(s):  
Dovydas Karoblis ◽  
Diana Griesiute ◽  
Kestutis Mazeika ◽  
Dalis Baltrunas ◽  
Dmitry V. Karpinsky ◽  
...  
Keyword(s):  
Bismuth Ferrite ◽  
Cost Effective ◽  
Xrd Analysis ◽  
Synthetic Approach ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Dsc Measurements ◽  
Optimal Annealing Temperature ◽  
Synthesized Materials

In this study, a highly crystalline bismuth ferrite (BFO) powder was synthesized using a novel, very simple, and cost-effective synthetic approach. It was demonstrated that the optimal annealing temperature for the preparation of highly-pure BFO is 650 °C. At lower or higher temperatures, the formation of neighboring crystal phases was observed. The thermal behavior of BFO precursor gel was investigated by thermogravimetric and differential scanning calorimetry (TG-DSC) measurements. X-ray diffraction (XRD) analysis and Mössbauer spectroscopy were employed for the investigation of structural properties. Scanning electron microscopy (SEM) was used to evaluate morphological features of the synthesized materials. The obtained powders were also characterized by magnetization measurements, which showed antiferromagnetic behavior of BFO powders.

scholarly journals Luminescence of SiO2-BaF2:Tb3+, Eu3+ Nano-Glass-Ceramics Made from Sol–Gel Method at Low Temperature

Nanomaterials ◽  
2022 ◽  
Vol 12 (2) ◽  
pp. 259
Author(s):  
Natalia Pawlik ◽  
Barbara Szpikowska-Sroka ◽  
Tomasz Goryczka ◽  
Ewa Pietrasik ◽  
Wojciech A. Pisarski
Keyword(s):  
Sol Gel ◽  
Three Dimensional ◽  
Glass Ceramics ◽  
Emission Spectra ◽  
Scanning Calorimetry ◽  
Light Emitting ◽  
Co Doping ◽  
Dsc Measurements ◽  
Decay Times

The synthesis and characterization of multicolor light-emitting nanomaterials based on rare earths (RE3+) are of great importance due to their possible use in optoelectronic devices, such as LEDs or displays. In the present work, oxyfluoride glass-ceramics containing BaF2 nanocrystals co-doped with Tb3+, Eu3+ ions were fabricated from amorphous xerogels at 350 °C. The analysis of the thermal behavior of fabricated xerogels was performed using TG/DSC measurements (thermogravimetry (TG), differential scanning calorimetry (DSC)). The crystallization of BaF2 phase at the nanoscale was confirmed by X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM), and the changes in silicate sol–gel host were determined by attenuated total reflectance infrared (ATR-IR) spectroscopy. The luminescent characterization of prepared sol–gel materials was carried out by excitation and emission spectra along with decay analysis from the 5D4 level of Tb3+. As a result, the visible light according to the electronic transitions of Tb3+ (5D4 → 7FJ (J = 6–3)) and Eu3+ (5D0 → 7FJ (J = 0–4)) was recorded. It was also observed that co-doping with Eu3+ caused the shortening in decay times of the 5D4 state from 1.11 ms to 0.88 ms (for xerogels) and from 6.56 ms to 4.06 ms (for glass-ceramics). Thus, based on lifetime values, the Tb3+/Eu3+ energy transfer (ET) efficiencies were estimated to be almost 21% for xerogels and 38% for nano-glass-ceramics. Therefore, such materials could be successfully predisposed for laser technologies, spectral converters, and three-dimensional displays.

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