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.

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.

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.

Analytical Models for the Systematic Errors of Differential Scanning Calorimetry Instruments

Volume 1 ◽  
2004 ◽  
Author(s):  
Adrian S. Sabau ◽  
Wallace D. Porter
Keyword(s):  
Differential Scanning Calorimetry ◽  
Phase Change ◽  
Computational Analysis ◽  
Systematic Errors ◽  
Analytical Models ◽  
Transition Temperatures ◽  
Scanning Calorimetry ◽  
Heating And Cooling ◽  
Dsc Measurements ◽  
Phase Transition Temperatures

Differential Scanning Calorimetry (DSC) measurements are routinely used to determine enthalpies of phase change, phase transition temperatures, glass transition temperatures, and heat capacities. In order to obtain data on the amount of phases during phase change, time-temperature lags, which are inherent to the measurement process, must be estimated through a computational analysis. An analytical model is proposed for the systematic error of the instrument. Numerical simulation results are compared against experimental data obtained at different heating and cooling rates.

scholarly journals Soil Burial Biodegradation of PLA/Hydrolysed Collagen/Silver Manoparticles Bionanocomposites

2020 ◽  
Vol 71 (4) ◽  
pp. 128-135
Author(s):  
Petruta Preda ◽  
Maria Rapa ◽  
Alexandru Nicoara ◽  
Oana Tutunaru ◽  
Marioara Avram ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Differential Scanning Calorimetry ◽  
Melt Processing ◽  
Scanning Calorimetry ◽  
Degradation Behaviour ◽  
Soil Burial ◽  
Dsc Measurements ◽  
Scanning Electron ◽  
Loss Determination

In this study we evaluated the degradation behaviour of some polymeric bionanocomposites based on polylactic acid (PLA), hydrolysed collagen (HC) and silver nanoparticles (AgNPs) obtained by melt processing, by exposure at soil action for 30 days and 60 days. The quantification of the bionanocomposites� degradability was investigated by the weight loss determination, evaluation of the morphology-Scanning Electron Microscopy (SEM) measurements and the thermal parameters by Differential Scanning Calorimetry (DSC) measurements. From the obtained results we can observe that the polymeric composites based on hydrolysed collagen has degraded.

scholarly journals Assessment of the denaturation of collagen protein concentrates using different techniques

2019 ◽  
Vol 400 (12) ◽  
pp. 1583-1591 ◽  
Author(s):  
Victor Perez-Puyana ◽  
Francisco J. Ostos ◽  
Pilar López-Cornejo ◽  
Alberto Romero ◽  
Antonio Guerrero
Keyword(s):  
Differential Scanning Calorimetry ◽  
Fourier Transform ◽  
Glass Transition ◽  
Infrared Spectroscopy ◽  
Raw Material ◽  
Cd Spectra ◽  
Scanning Calorimetry ◽  
Dsc Measurements ◽  
Collagen Protein ◽  
Α Helix

AbstractThe use of collagen and gelatin in the field of regenerative medicine is widely extended. However, most of the studies in this topic are focused on the scaffolds’ properties, but only a few are related to the properties of the raw material used. The raw material analysis not only consists of a study of the composition, but also of the denaturation degree that can influence the processing and properties of the structure of the scaffold. Thus, the denaturation degree analysis of different collagen proteins was performed and assessed by the comparison of four different methods: differential scanning calorimetry (DSC), Fourier transform Infrared Spectroscopy (FTIR) and circular dichroism (CD) spectra and sulfhydryls content analysis. DSC measurements put forward a glass transition between 88°C and 95°C as well as from the FTIR measurements; the characteristic peaks for proteins are evidenced. However, from the sulfur content, only a small proportion of free sulfhydryls are present with respect to their total amount. In addition, CD spectra allow to estimate the secondary structure of the protein by the analysis of the α-helix and β-strand and also quantify the denaturation degree with the ‘positive/negative ratio’ (RPN) from the CD profiles, obtaining values in the range between 25% and 100%.

Applying Differential Scanning Calorimetry to Detergency Studies of Oily Soil

1992 ◽  
Vol 62 (2) ◽  
pp. 101-104 ◽  
Author(s):  
Mamiko Yatagai ◽  
Motoko Komaki ◽  
Toshimasa Hashimoto
Keyword(s):  
Differential Scanning Calorimetry ◽  
Filter Paper ◽  
Soil Removal ◽  
Fibrous Materials ◽  
Oily Soil ◽  
Melting Points ◽  
Scanning Calorimetry ◽  
Dsc Measurements ◽  
Peak Areas ◽  
Polymorphic Forms

Differential scanning calorimetry (DSC) has been applied to studies of oily soil removal from fibrous materials. Fabric and filter paper were soiled with various oily substances present in sebum. After washing, the fibrous samples were subjected to DSC measurements. The residual oily soils on the samples were analyzed by the melting peak areas of the DSC heating curves, a method that is widely applicable to various oily substances with different melting points and polymorphic forms. Various woven or nonwoven fibrous samples can be scanned, regardless of sample size in washing experiments.

scholarly journals Morphological Investigation into Starch Bio-Nanocomposites via Synchrotron Radiation and Differential Scanning Calorimetry

2011 ◽  
Vol 2011 ◽  
pp. 1-14 ◽  
Author(s):  
Huihua Liu ◽  
Deeptangshu Chaudhary ◽  
Joseph John ◽  
Moses O. Tadé
Keyword(s):  
Differential Scanning Calorimetry ◽  
Moisture Content ◽  
Scanning Calorimetry ◽  
Dsc Measurements ◽  
X Ray Scattering ◽  
Free Moisture ◽  
Ternary Interactions ◽  
Diffraction Patterns ◽  
Crystalline Domains ◽  
Crystalline Growth

We studied a hydrophilic, plasticized bionanocomposite system involving sorbitol plasticizer, amylose biopolymer, and montmorillonite (MMT) for the presence of competitive interactions among them at different moisture content. Synchrotron analysisviasmall angle X-ray scattering (SAXS) and thermal analysis using differential scanning calorimetry (DSC) were performed to understand crystalline growth and the distribution of crystalline domains within the samples. The SAXS diffraction patterns showed reduced interhelix spacing in the amylose network indicating strong amylose-sorbitol interactions. Depending on the sorbitol and MMT concentration, these interactions also affected the free moisture content and crystalline domains. Domains of around 95 Å and 312 Å were found in the low-moisture-content samples as compared to a single domain of 95 Å in the high-moisture-content samples. DSC measurements confirmed that the MMT increased the onset and the melting temperature of nanocomposites. Moreover, the results showed that the ternary interactions among sorbitol-amylose-MMT supported the crystalline heterogeneity through secondary nucleation.

scholarly journals Thermal analysis of Li2-хNaxGe4O9 glasses crystallization

2020 ◽  
Vol 28 (2) ◽  
pp. 83-86
Author(s):  
A. O. Diachenko ◽  
D. V. Volynets ◽  
M. P. Trubitsyn ◽  
M. D. Volnianskii
Keyword(s):  
Thermal Analysis ◽  
Solid Solution ◽  
Differential Scanning Calorimetry ◽  
Thermal Gravimetric Analysis ◽  
Single Stage ◽  
Gravimetric Analysis ◽  
Thermal Gravimetric ◽  
Glass Crystallization ◽  
Scanning Calorimetry ◽  
Dsc Measurements

The glasses of lithium-sodium tetragermanate LiNaGe4O9 and solid solution Li1.8Na0.2Ge4O9 were prepared by quenching the melt and crystallized on heating. The glass crystallization was controlled by differential scanning calorimetry and thermal gravimetric analysis. The DSC measurements performed in the range 300–1200 K show that the crystallization of the glasses occurs through a single stage. There are no anomalies on TGA dependences. It is assumed that LiNaGe4O9 and Li 1.8Na0.2Ge4O9 glasses crystallize in accordance with a polymorphic mechanism.

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