Annealing Kinetics of Neutron?Irradiated Aluminium and Copper

1960 ◽  
Vol 13 (2) ◽  
pp. 347 ◽  
Author(s):  
TH Blewitt ◽  
RR Coltman ◽  
CE Klabunde
Keyword(s):  
Activation Energy ◽  
Activation Energies ◽  
Slope Method ◽  
Measured Activation Energy ◽  
Measured Activation ◽  
Kinetics Of ◽  
Constant Activation Energy

Activation energies for the annealing of copper and aluminium following reactor bombardment near 4 OK have been measured in the range from 10 to 40 OK. Both the change in slope method and the isothermal technique method were utilized with the assumption that a constant activation energy existed. Computations of the number of jumps involved from the measured activation energy result in an impossibly small number. It is obvious that the method for determination of the activation energies is not applicable, probably because of the non-uniqueness of the activation energy.

Investigations of the νT=1 Exciton Condensate

2007 ◽  
Vol 21 (08n09) ◽  
pp. 1256-1265 ◽  
Author(s):  
R. D. Wiersma ◽  
J. G. S. Lok ◽  
L. Tiemann ◽  
W. Dietsche ◽  
K. von Klitzing ◽  
...  
Keyword(s):  
Activation Energy ◽  
Quantum Hall ◽  
Activation Energies ◽  
Condensation Energy ◽  
Counter Flow ◽  
Zero Bias ◽  
Thermally Activated ◽  
Measured Activation Energy ◽  
Exciton Condensate ◽  
Measured Activation

Recent experiments on quantum Hall bilayers in the vicinity of total filling factor 1 (νT=1) have revealed the possibility of a superfluidic exciton condensate. We report on our experimental work involving the νT=1 exciton condensate in independently contacted bilayer two-dimensional electron systems. We reproduce the previously reported zero bias resonant tunneling peak, a quantized Hall drag resistivity, and in counter-flow configuration, the near vanishing of both ρxx and ρxy resistivity components. At balanced electron densities in the layers, we find for both drag and counter-flow current configurations, thermally activated transport with a monotonic increase of the activation energy for d/ℓB < 1.65 with activation energies up to 0.4 K. In the imbalanced system the activation energies show a striking asymmetry around the balance point, implying that the gap to charge excitations is considerably different in the separate layers that form the bilayer condensate. This indicates that the measured activation energy is neither the binding energy of the excitons, nor their condensation energy. We establish a phase diagram of the excitonic condensate showing the enhancement of this state at slight imbalances.

scholarly journals Temperature Effects on the Crystallization and Coarsening of Nano-CeO2 Powders

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
H. F. Lopez ◽  
H. Mendoza
Keyword(s):  
Activation Energy ◽  
Mass Transport ◽  
Ostwald Ripening ◽  
Effect Of Temperature ◽  
Transport Mechanisms ◽  
X Ray Diffraction ◽  
Measured Activation Energy ◽  
Measured Activation ◽  
Mass Transport Mechanisms ◽  
Nanoparticle Sizes

The effect of temperature on nano-CeO2 particle coarsening is investigated. The nanoceria powders were synthesized using the microemulsion method and then exposed to temperatures in the range of 373–1273 K. It was found that the nanoparticles exhibited a strong tendency to form agglomerates and through the application of ultrasound these agglomerates could be broken into smaller sizes. In addition average nanoparticle sizes were determined by powder X-ray diffraction (XRD). The outcome of this work indicates that the initial nano-CeO2 powders are amorphous in nature. Annealing promotes CeO2 crystallization and a slight shift in the (111) XRD intensity peaks corresponding to CeO2. Moreover, at temperatures below 773 K, grain growth in nano-CeO2 particles is rather slow. Apparently, mass transport through diffusional processes is not likely to occur as indicated by an estimated activation energy of 20 kJ/mol. At temperatures above 873 K, the measured activation energy shifted to 105 kJ/mol suggesting a possible transition to Ostwald-Ripening type mass transport mechanisms.

Hydrogen Incorporation in A-Si:H: Temperature and Doping Type Dependence

1990 ◽  
Vol 192 ◽  
Author(s):  
M.J.M. Pruppers ◽  
K.M.H. Maessen ◽  
F.H.P.M. Habraken ◽  
J. Bezemer ◽  
W.F. Van Der Weg
Keyword(s):  
Activation Energy ◽  
Glow Discharge ◽  
Gas Phase ◽  
Hydrogen Concentration ◽  
Hydrogen Content ◽  
Hydrogen Incorporation ◽  
Undoped Material ◽  
Measured Activation Energy ◽  
Measured Activation ◽  
The Difference

ABSTRACTPhosphorus, boron and compensation doped hydrogenated amorphous silicon films were deposited in a glow discharge at different substrate temperatures in the range 50–330°C. Gas phase doping levels were 1%. At the lower temperatures the hydrogen concentration in the B doped and compensated doped films is larger than in the P and undoped films. For higher deposition temperatures the H concentration of the B doped films appeared to be smaller than in the other materials. The difference in hydrogen content of the doped and undoped material, deposited at various temperatures, is considered as a function of the measured activation energy for conduction in these films. This difference varies in much the same way with the activation energy as the hydrogen content in films deposited at one substrate temperature, but with varying gas phase dopant levels. This represents strong evidence that, apart from the deposition temperature, the hydrogen concentration in glow discharge a-Si:H is determined by the position of the Fermi level.

Synthesis and Determination of the Kinetic Parameters for Non-Isothermal Decomposition of Complexes Ln(thd)3phen

2006 ◽  
Vol 530-531 ◽  
pp. 506-512 ◽  
Author(s):  
Wilton Silva Lopes ◽  
Crislene Rodrigues da Silva Morais ◽  
A.G. de Souza
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Lanthanide Complexes ◽  
Reaction Order ◽  
Decomposition Reaction ◽  
Cylindrical Symmetry ◽  
Boundary Reaction ◽  
Phase Boundary Reaction ◽  
Kinetics Of

In this work the kinetics of the thermal decomposition of two ß-diketone lanthanide complexes of the general formula Ln(thd)3phen (where Ln = Nd+3 or Tm+3, thd = 2,2,6,6- tetramethyl-3,5-heptanodione and phen = 1,10-phenantroline) has been studied. The powders were characterized by several techniques. Thermal decomposition of the complexes was studied by non-isothermal thermogravimetry techniques. The kinetic model that best describes the process of the thermal decomposition of the complexes it was determined through the method proposed by Coats-Redfern. The average values the activation energy obtained were 136 and 114 kJ.mol-1 for the complexes Nd(thd)3phen and Tm(thd)3phen, respectively. The kinetic models that best described the thermal decomposition reaction the both complexes were R2. The model R2 indicating that the mechanism is controlled by phase-boundary reaction (cylindrical symmetry) and is defined by the function g(α) = 2[1-(1-a)1/2], indicating a mean reaction order. The values of activation energy suggests the following decreasing order of stability: Nd(thd)3phen > Tm(thd)3phen.

Hydrogen Passivation Kinetics of Si Nanocrystals in SiO2

2003 ◽  
Vol 770 ◽  
Author(s):  
Andrew R. Wilkinson ◽  
Robert G. Elliman
Keyword(s):  
Reaction Kinetics ◽  
Activation Energies ◽  
Hydrogen Passivation ◽  
Time Resolved ◽  
Luminescence Efficiency ◽  
Si Nanocrystals ◽  
Preliminary Study ◽  
Kinetics Of ◽  
Insight Into

AbstractHydrogen passivation of non-radiative defects increases the luminescence intensity from silicon nanocrystals. In this study, photoluminescence (PL) and time-resolved PL were used to investigate the chemical kinetics of the hydrogen passivation process. Isochronal and isothermal annealing sequences were used to determine the reaction kinetics for the absorption and desorption of hydrogen, using the generalised consistent simple thermal (GST) model proposed by Stesmans for Pb defects at planar Si/SiO2 interfaces. This included determination of the activation energies and rate constants for the forward and reverse reactions as well as the associated spread in activation energies. The reaction kinetics determined from such measurements were found to be in excellent agreement with those for the passivation of Pb defects at planar Si/SiO2 interfaces, suggesting the nanocrystal emission process is also limited by such defects. These results provide useful model data as well as insight into the processing conditions needed to achieve optimum passivation in H2. As an extension to the work, a preliminary study into passivation by atomic hydrogen was pursued via a post-metallization Al anneal (alneal). A considerable gain in luminescence efficiency was achieved over the previously optimised passivation in H2.

scholarly journals Torrefaction of Sewage Sludge: Kinetics and Fuel Properties of Biochars

Energies ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 565 ◽  
Author(s):  
Jakub Pulka ◽  
Piotr Manczarski ◽  
Jacek Koziel ◽  
Andrzej Białowiec
Keyword(s):  
Activation Energy ◽  
Sewage Sludge ◽  
Thermal Transformation ◽  
Fuel Properties ◽  
Process Time ◽  
Technological Aspect ◽  
Heating Value ◽  
Valuable Product ◽  
Kinetics Of

We propose a ‘Waste to Carbon’ thermal transformation of sewage sludge (SS) via torrefaction to a valuable product (fuel) with a high content of carbon. One important, technological aspect to develop this concept is the determination of activation energy needed for torrefaction. Thus, this research aimed to evaluate the kinetics of SS torrefaction and determine the effects of process temperature on fuel properties of torrefied products (biochars). Torrefaction was performed using high ash content SS at six (200~300 °C) temperatures and 60 min residence (process) time. Mass loss during torrefaction ranged from 10~20%. The resulting activation energy for SS torrefaction was ~12.007 kJ·mol−1. Initial (unprocessed) SS higher heating value (HHV) was 13.5 MJ·kg−1. However, the increase of torrefaction temperature decreased HHV from 13.4 to 3.8 MJ·kg−1. Elemental analysis showed a significant decrease of the H/C ratio that occurred during torrefaction, while the O/C ratio fluctuated with much smaller differences. Although the activation energy was significantly lower compared with lignocellulosic materials, low-temperature SS torrefaction technology could be explored for further SS stabilization and utilization (e.g., dewatering and hygienization).

scholarly journals GaN Decomposition in Ammonia

2000 ◽  
Vol 5 (S1) ◽  
pp. 273-279 ◽  
Author(s):  
D.D. Koleske ◽  
A.E. Wickenden ◽  
R.L. Henry
Keyword(s):  
Activation Energy ◽  
Growth Rate ◽  
Decomposition Rate ◽  
Flow Conditions ◽  
Growth Pressure ◽  
Growth Environment ◽  
Similar Role ◽  
Measured Activation Energy ◽  
Movpe Growth ◽  
Measured Activation

GaN decomposition is studied as a function of pressure and temperature in mixed NH3 and H2 flows more characteristic of the MOVPE growth environment. As NH3 is substituted for the 6 SLM H2 flow, the GaN decomposition rate at 1000 °C is reduced from 1×1016 cm−2 s−1 (i.e. 9 monolayers/s) in pure H2 to a minimum of 1×1014 cm−2 s−1 at an NH3 density of 1×1019 cm−3. Further increases of the NH3 density above 1×1019 cm−3 result in an increase in the GaN decomposition rate. The measured activation energy, EA, for GaN decomposition in mixed H2 and NH3 flows is less than the EA measured in vacuum and in N2 environments. As the growth pressure is increased under the same H2 and NH3 flow conditions, the decomposition rate increases and the growth rate decreases with the addition of trimethylgallium to the flow. The decomposition in mixed NH3 and H2 and in pure H2 flows behave similarly, suggesting that surface H plays a similar role in the decomposition and growth of GaN in NH3.

Kinetics of Magnetic Relaxation and Determination of Activation Energy in High-$\bf {\mbi T}_{c}$ Superconductors

1994 ◽  
Vol 33 (Part 2, No. 6B) ◽  
pp. L843-L845
Author(s):  
Xiao-Guang Li ◽  
Ryu Kobayashi ◽  
Yasutoshi Kotaka ◽  
Jun-ichi Shimoyama ◽  
Kohji Kishio
Keyword(s):  
Activation Energy ◽  
Magnetic Relaxation ◽  
Kinetics Of

scholarly journals Desorption characteristics and kinetic parameters determination of molecular sieve by thermogravimetric analysis/differential thermogravimetric analysis technique

2018 ◽  
Vol 36 (7-8) ◽  
pp. 1389-1404 ◽  
Author(s):  
Yalou Guo ◽  
Hui Zhang ◽  
Yingshu Liu
Keyword(s):  
Activation Energy ◽  
Thermogravimetric Analysis ◽  
Heating Rates ◽  
Carrier Gas ◽  
Zeolite 13X ◽  
Analysis Technique ◽  
Desorption Activation Energy ◽  
Differential Thermogravimetric Analysis ◽  
Kinetics Of

The kinetics of the thermal desorption of CO2 adsorbed on zeolite 13X were obtained using a differential thermogravimetric analyser under two different carrier gas conditions. The varying heating rates were set as 8, 12, 16, and 20 K min−1, respectively. The desorption activation energy of the physisorption sites for this experiment evaluated by an integral method without prediction of the reaction order ranged from 12.15 to 14.12 kJ mol−1 (CO2 as the carrier gas) and 43.32 to 50.42 kJ mol−1 (Ar as the carrier gas), respectively. The desorption activation energy of the chemisorption sites ranged from 57.95 to 58.53 kJ mol−1 (CO2 as the carrier gas) and 74.02 to 79.92 kJ mol−1 (Ar as the carrier gas), respectively.

Oxidation kinetics of biodiesel from soybean mixed with synthetic antioxidants BHA, BHT and TBHQ: Determination of activation energy

2014 ◽  
Vol 127 ◽  
pp. 111-116 ◽  
Author(s):  
Dionisio Borsato ◽  
João Rafael de Moraes Cini ◽  
Hágata Cremasco da Silva ◽  
Rodolfo Lopes Coppo ◽  
Karina Gomes Angilelli ◽  
...  
Keyword(s):  
Activation Energy ◽  
Oxidation Kinetics ◽  
Synthetic Antioxidants ◽  
Kinetics Of
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