Influences of Surface Chemistry on Dehydrogenation Kinetics of Ammonia Borane in Porous Carbon Scaffold

2010 ◽  
Vol 132 ◽  
pp. 19-28 ◽  
Author(s):  
Saghar Sepehri ◽  
Betzaida Batalla García ◽  
Qi Feng Zhang ◽  
Guo Zhong Cao
Keyword(s):  
Activation Energy ◽  
Surface Chemistry ◽  
Ammonia Borane ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Dehydrogenation Kinetics ◽  
Carbon Cryogel ◽  
Solid Form ◽  
Kinetics Of ◽  
Catalytic Effects

Ammonia borane (AB) with high gravimetric hydrogen capacity is of great interest for storing hydrogen in solid form which is an important issue in the growing field of hydrogen technology. In this work the effects of surface chemistry on dehydrogenation kinetics of carbon cryogel (CC) – ammonia borane nanocomposites have been studied. Boron-modified, nitrogen-modified, and boron-nitrogen- modified CCs were used as scaffold for AB and dehydrogenation kinetics of CC-ABs was studied by means of differential scanning calorimetry (DSC) at multiple heating rates. The results demonstrated that AB incorporated inside the mesopores of CC modified with nitrogen and boron possesses lower activation energy with enhanced kinetics of dehydrogenation due to catalytic effects as compared to AB in unmodified CC under otherwise the same or similar conditions. In addition, the lowest activation energy was observed for boron-modified CC-AB that could be attributed to the destabilization of AB by surface interactions with B2O3 that may accelerate the dehydrogenation process.

Modified Carbon Cryogel-Ammonia Borane Nanocomposites for Hydrogen Storage

2007 ◽  
Vol 1042 ◽  
Author(s):  
Saghar Sepehri ◽  
Betzaida Batalla Garcia ◽  
Qifeng Zhang ◽  
Guozhong Cao
Keyword(s):  
Hydrogen Storage ◽  
Photoelectron Spectroscopy ◽  
Ammonia Borane ◽  
Scanning Calorimetry ◽  
Dehydrogenation Kinetics ◽  
Carbon Cryogel ◽  
Nitrogen Doped Carbon ◽  
Kinetics Of ◽  
Catalytic Effects

AbstractThis paper reports the synthesis and characterization of coherent Boron/Nitrogen –doped –carbon cryogels- ammonia borane nanocomposites for hydrogen storage. Resorcinol formaldehyde derived doped carbon cryogels (CC) were obtained via chemical modification.CC- ammonia-borane nanocomposites were made by incorporation of ammonia borane (AB), in CCs. Nitrogen sorption analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy, are used to investigate the structure and morphology of the modified CCs. Differential scanning calorimetry is used to study the dehydrogenation of coherent doped-CC-AB nanocomposites. Modified CCs show higher mesoporosity, and more homogeneous porous structure compared to undoped CCs. Also, dehydrogenation kinetics of nanocomposites is enhanced as compared to neat AB. Possible nanoscale and catalytic effects of nanocomposites in improved dehydrogenation kinetics are discussed.

Effect of Pore Size on Dehydrogenation Temperature of Carbon Cryogel-Ammoniaborane Nanocomposites

2008 ◽  
Vol 1098 ◽  
Author(s):  
Saghar Sepehri ◽  
Betzaida Batalla Garcia ◽  
Guozhong Cao
Keyword(s):  
Differential Scanning Calorimetry ◽  
Hydrogen Storage ◽  
Pore Size ◽  
Porous Carbon ◽  
Ammonia Borane ◽  
Scanning Calorimetry ◽  
Resorcinol Formaldehyde ◽  
Dehydrogenation Kinetics ◽  
Carbon Cryogel ◽  
Kinetics Of

AbstractThis study reports the effects of pore size of porous carbon scaffold on the dehydrogenation of ammoniaborane in the coherent carbon- ammoniaborane nanocomposites. Porous carbon scaffold is obtained from resorcinol formaldehyde derived carbon cryogels. The nanocomposites are made by simple soaking porous carbon scaffold in ammonia borane solution. Nitrogen sorption analysis and differential scanning calorimetry are used to investigate the structure and dehydrogenation of the nanocomposites. The results reveal that dehydrogenation temperature decreases in nanocomposites as compared to neat ammonia borane, and is lower in nanocomoposites with smaller pore sizes. These findings can be used to tune the dehydrogenation temperature to meet specific hydrogen storage applications. Also, dehydrogenation kinetics of nanocomposites is enhanced as compared to neat ammonia borane.

scholarly journals Non-Isothermal Sublimation Kinetics of 2,4,6-Trinitrotoluene (TNT) Nanofilms

Molecules ◽  
2019 ◽  
Vol 24 (6) ◽  
pp. 1163 ◽  
Author(s):  
Walid Hikal ◽  
Brandon Weeks
Keyword(s):  
Activation Energy ◽  
Analytical Techniques ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Absorbance Spectroscopy ◽  
Calculated Activation Energy ◽  
Sublimation Kinetics ◽  
Sublimation Rates ◽  
First Time ◽  
Kinetics Of

Non-isothermal sublimation kinetics of low-volatile materials is more favorable over isothermal data when time is a crucial factor to be considered, especially in the subject of detecting explosives. In this article, we report on the in-situ measurements of the sublimation activation energy for 2,4,6-trinitrotoluene (TNT) continuous nanofilms in air using rising-temperature UV-Vis absorbance spectroscopy at different heating rates. The TNT films were prepared by the spin coating deposition technique. For the first time, the most widely used procedure to determine sublimation rates using thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC) was followed in this work using UV-Vis absorbance spectroscopy. The sublimation kinetics were analyzed using three well-established calculating techniques. The non-isothermal based activation energy values using the Ozawa, Flynn–Wall, and Kissinger models were 105.9 ± 1.4 kJ mol−1, 102.1 ± 2.7 kJ mol−1, and 105.8 ± 1.6 kJ mol−1, respectively. The calculated activation energy agreed well with our previously reported isothermally-measured value for TNT nanofilms using UV-Vis absorbance spectroscopy. The results show that the well-established non-isothermal analytical techniques can be successfully applied at a nanoscale to determine sublimation kinetics using absorbance spectroscopy.

scholarly journals Thermal Analysis On The Kinetics Of Magnesium-Aluminum Layered Double Hydroxides In Different Heating Rates

2015 ◽  
Vol 60 (2) ◽  
pp. 1357-1359 ◽  
Author(s):  
Y. Hongbo ◽  
C. Meiling ◽  
W. Xu ◽  
G. Hong
Keyword(s):  
Activation Energy ◽  
Thermal Analysis ◽  
Layered Double Hydroxides ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Exponential Factor ◽  
Thermal Kinetic Parameters ◽  
Double Hydroxides ◽  
Kinetics Of ◽  
Dsc Curves

Abstract The thermal decomposition of magnesium-aluminum layered double hydroxides (LDHs) was investigated by thermogravimetry analysis and differential scanning calorimetry (DSC) methods in argon environment. The influence of heating rates (including 2.5, 5, 10, 15 and 20K/min) on the thermal behavior of LDHs was revealed. By the methods of Kissinger and Flynn-Wall-Ozawa, the thermal kinetic parameters of activation energy and pre-exponential factor for the exothermic processes under non-isothermal conditions were calculated using the analysis of corresponding DSC curves.

Crystallization Kinetics in Cu64.5Zr35.5 Binary Metallic Glass

2017 ◽  
Vol 727 ◽  
pp. 233-238 ◽  
Author(s):  
Qian Gao ◽  
Zeng Yun Jian ◽  
Jun Feng Xu ◽  
Man Zhu
Keyword(s):  
Activation Energy ◽  
Grain Growth ◽  
Crystallization Kinetics ◽  
Crystallization Process ◽  
Crystallization Kinetic ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Growth Activation ◽  
Local Activation Energy ◽  
Kinetics Of

The crystallization kinetics of melt-spun Cu64.5Zr35.5 amorphous alloy ribbons was investigated using differential scanning calorimetry (DSC) at different heating rates. Besides, the Kissinger and isoconversional approaches were used to obtain the crystallization kinetic parameters. As shown in the results, the activation energies for glass transition and crystallization process at the onset, peak and end crystallization temperatures were obtained by means of Kissinger equation to be 577.65 ± 34, 539.86 ± 54, 518.25 ± 20 and 224.84 ± 2 kJ/mol, respectively. The nucleation activation energy Enucleation is greater than grain growth activation energy Egrowth, indicating that the nucleation process is harder than grain growth. The local activation energy Eα decreases in the whole crystallization process, which suggests that crystallization process is increasingly easy.

Estimation of Cure and Thermal Degradation Kinetics of Epoxy/Organoclay Nanocomposite

2010 ◽  
Vol 123-125 ◽  
pp. 667-670 ◽  
Author(s):  
Jae Young Lee ◽  
Bum Choul Choi ◽  
Hong Ki Lee
Keyword(s):  
Activation Energy ◽  
Thermal Degradation ◽  
Epoxy Matrix ◽  
Degradation Kinetics ◽  
Cure Kinetics ◽  
Diglycidyl Ether ◽  
Thermal Degradation Kinetics ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Kinetics Of

Polymer nanocomposite was synthesized through the intercalation and exfoliation of organoclay in an epoxy matrix. The epoxy matrix was composed of diglycidyl ether of bisphenol A (DGEBA, epoxy base resin), 4,4'-methylene dianiline (MDA, curing agent) and malononitrile (MN, chain extender) and organoclay was prepared by treating the montmorillonite with octadecyltrimethylammonium bromide (ODTMA). The intercalation of the organoclay was estimated by wide angle X-ray diffraction (WAXD) and transmission electron microscope (TEM) analyses. In order to measure the cure rate of DGEBA/MDA (30 phr)/MN (5 phr)/Organoclay (5 phr), differential scanning calorimetry (DSC) analysis were performed at the heating rates of 5, 10, 15 and 20 oC/min, and the data was interpreted by Kissinger equation. Thermal degradation kinetics of the epoxy nanocomposite was also studied by thermogravimetric analysis (TGA). The epoxy sample was decomposed in the TGA furnace at the heating rates of 5, 10, 15 and 20 oC/min with nitrogen atmosphere of 50 ml/min. The TGA data was introduced to the Ozawa equation and the degradation activation energy was calculated according to the degradation ratio. The activation energy for cure kinetics was 43.3 kJ/mol and that for thermal degradation was 171.5 kJ/mol.

scholarly journals Effect of Surface Treatment of Halloysite Nanotubes (HNTs) on the Kinetics of Epoxy Resin Cure with Amines

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 930 ◽  
Author(s):  
Vahideh Akbari ◽  
Maryam Jouyandeh ◽  
Seyed Mohammad Reza Paran ◽  
Mohammad Reza Ganjali ◽  
Hossein Abdollahi ◽  
...  
Keyword(s):  
Activation Energy ◽  
Epoxy Resin ◽  
Low Cost ◽  
Halloysite Nanotubes ◽  
Diffusion Control ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Epoxy Amine ◽  
Amine System ◽  
Kinetics Of

The epoxy/clay nanocomposites have been extensively considered over years because of their low cost and excellent performance. Halloysite nanotubes (HNTs) are unique 1D natural nanofillers with a hollow tubular shape and high aspect ratio. To tackle poor dispersion of the pristine halloysite (P-HNT) in the epoxy matrix, alkali surface-treated HNT (A-HNT) and epoxy silane functionalized HNT (F-HNT) were developed and cured with epoxy resin. Nonisothermal differential scanning calorimetry (DSC) analyses were performed on epoxy nanocomposites containing 0.1 wt.% of P-HNT, A-HNT, and F-HNT. Quantitative analysis of the cure kinetics of epoxy/amine system made by isoconversional Kissinger–Akahira–Sunose (KAS) and Friedman methods made possible calculation of the activation energy (Eα) as a function of conversion (α). The activation energy gradually increased by increasing α due to the diffusion-control mechanism. However, the average value of Eα for nanocomposites was lower comparably, suggesting autocatalytic curing mechanism. Detailed assessment revealed that autocatalytic reaction degree, m increased at low heating rate from 0.107 for neat epoxy/amine system to 0.908 and 0.24 for epoxy/P-HNT and epoxy/A-HNT nanocomposites, respectively, whereas epoxy/F-HNT system had m value of 0.072 as a signature of dominance of non-catalytic reactions. At high heating rates, a similar behavior but not that significant was observed due to the accelerated gelation in the system. In fact, by the introduction of nanotubes the mobility of curing moieties decreased resulting in some deviation of experimental cure rate values from the predicted values obtained using KAS and Friedman methods.

Global Kinetics of the Thermal Decomposition of Materials

1997 ◽  
Author(s):  
Azzedine Missoum ◽  
Ashwani K. Gupta ◽  
Jianrong Chen
Keyword(s):  
Heat Transfer ◽  
Activation Energy ◽  
Heating Rate ◽  
Decomposition Reaction ◽  
Decomposition Process ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Transfer Product ◽  
Product Evolution ◽  
Kinetics Of

Abstract Results on the thermal destruction behavior during the decomposition of cellulose under controlled conditions are presented. Thermogravimetric (TGA) and Differential Scanning Calorimetry (DSC) tests have been carried out on the celluose samples under conditions of various heating rate and surrounding gas environment. Pyrolysis times were also measured for different size particles having different moisture contents in a controlled mixing history reactor (CMHR). The global decomposition kinetics were investigated and it was found that the decomposition process is shifts to higher temperatures at higher heating rates as a result of the competing effects of heat and mass transfer, product diffusion and the reactions kinetics. The Arrhenius parameters for pyrolysis were determined using a first order decomposition reaction of the type, dm = −km dt. It was found that the activation energy, heat of pyrolysis and char yield are a strong function of the heating rate. An increase in heating rate from 5 to 60°C/min resulted in a change of activation energy from 204.19 to 138.31 kJ/mole °C. This heating rate dependence of the kinetics is discussed. The overall decomposition process of the examined materials is generally endothermic. In general, heat transfer, mass diffusion, product evolution, heating rate, temperature and environment are the parameters that control the decomposition process. It was also shown that heat transfer and mass transport have the most effects on the decomposition process.

scholarly journals Non-Isothermal Crystallization Kinetics of Co67Fe4Cr7Si8B14 Amorphous Alloy

2012 ◽  
Vol 706-709 ◽  
pp. 1311-1317 ◽  
Author(s):  
S.A. Hasheminezhad ◽  
M. Haddad-Sabzevar ◽  
S. Sahebian
Keyword(s):  
Activation Energy ◽  
Amorphous Alloy ◽  
Crystallization Kinetics ◽  
Isothermal Crystallization ◽  
Frequency Factor ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Kinetics Parameters ◽  
Isothermal Crystallization Kinetics ◽  
Kinetics Of

Non-isothermal crystallization kinetics of Co67Fe4Cr7Si8B14amorphous ribbons was studied by differential scanning calorimetry (DSC) technique under 10, 20, 30, 40 and 80 °Cmin-1heating rates. It is found that Co67Fe4Cr7Si8B14amorphous alloy exhibits two-stage crystallization on heating. The two crystallization peaks shift to higher temperatures with increasing heating rate. The apparent activation energies (EC) for the first stage of crystallization were determined as 443.44 and 434.47 kJmol-1by using the Kissinger and Ozawa equations, respectively. Frequency factor (A) estimated to be 1.084×1026s-1using Kissinger equation. Kinetics parameters such as Crystallization exponent (n) and dimensionality of growth (Ndim) were determined using JMA (Johnson-Mehl-Avrami) method. Details of the nucleation and growth behaviours during the non-isothermal crystallization were studied in terms of local activation energy EC(x) by the OFW (Ozawa, Flynn and Wall) method. Also the activation energy for nucleation (En) and growth (Eg) separately estimated.

scholarly journals Curing kinetics of two commercial urea-formaldehyde adhesives studied by isoconversional method

2011 ◽  
Vol 65 (6) ◽  
pp. 717-726 ◽  
Author(s):  
Mladjan Popovic ◽  
Jaroslava Budinski-Simendic ◽  
Mirjana Jovicic ◽  
Joszef Mursics ◽  
Milanka Djiporovic-Momcilovic ◽  
...  
Keyword(s):  
Activation Energy ◽  
Urea Formaldehyde ◽  
Curing Kinetics ◽  
Isoconversional Methods ◽  
Isoconversional Method ◽  
Reaction Enthalpy ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
Dsc Measurements ◽  
Kinetics Of

Differential scanning calorimetry (DSC) was used to evaluate the curing kinetics of two commercial urea-formaldehyde (UF) adhesives having different formaldehyde to urea (F/U) ratio of 1.112 (UF1) and 1.086 (UF2). DSC measurements were done in dynamic scanning regime with heating rates of 5, 10, 15 and 20?C?min-1 in order to determine the activation energy for each adhesive. Obtained data were analyzed using isoconversional methods with application of Ozawa-Flynn-Wall and Kissinger-Akahira-Sunose kinetic models. In addition, different catalyst levels were tested at the heating rate of 10?C/min. Results showed that the adhesive with higher F/U ratio achieved higher activation energy, while having lower peak temperature of curing reaction. It was also noticed that the increase of catalyst level influenced the increase of reaction enthalpy of the adhesive with lower F/U ratio.

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