scholarly journals Study of the Microstructural and First Hydrogenation Properties of TiFe Alloy with Zr, Mn and V as Additives

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1217
Author(s):  
Abhishek Kumar Patel ◽  
Alexandre Duguay ◽  
Bernard Tougas ◽  
Bettina Neumann ◽  
Chris Schade ◽  
...  
Keyword(s):  
High Capacity ◽  
Interface Velocity ◽  
Secondary Phase ◽  
Secondary Phases ◽  
Fast Reaction ◽  
Hydrogen Storage Properties ◽  
Rate Limiting Step ◽  
Diffusion Controlled ◽  
Rate Limiting ◽  
Storage Properties

In this paper, we report the effect of adding Zr + V or Zr + V + Mn to TiFe alloy on microstructure and hydrogen storage properties. The addition of only V was not enough to produce a minimum amount of secondary phase and, therefore, the first hydrogenation at room temperature under a hydrogen pressure of 20 bars was impossible. When 2 wt.% Zr + 2 wt.% V or 2 wt.% Zr + 2 wt.% V + 2 wt.% Mn is added to TiFe, the alloy shows a finely distributed Ti2Fe-like secondary phase. These alloys presented a fast first hydrogenation and a high capacity. The rate-limiting step was found to be 3D growth, diffusion controlled with decreasing interface velocity. This is consistent with the hypothesis that the fast reaction is likely to be the presence of Ti2Fe-like secondary phases that act as a gateway for hydrogen.

Devitrification kinetics and mechanism of Pyrex borosilicate glass

2001 ◽  
Vol 16 (6) ◽  
pp. 1752-1758 ◽  
Author(s):  
Jau-Ho Jean ◽  
Yu-Ching Fang
Keyword(s):  
Borosilicate Glass ◽  
Linear Growth ◽  
Energy Analysis ◽  
Three Dimensional ◽  
Rate Limiting Step ◽  
Dimensional Diffusion ◽  
Limiting Step ◽  
Diffusion Controlled ◽  
Rate Limiting ◽  
Kinetics Of

Cristobalite is formed when initially amorphous Pyrex borosilicate glass (Corning 7740) is fired at temperatures ranging from 700 to 1000 °C. The sigmoidal devitrification kinetics of cristobalite obeys Avrami-like three-dimensional diffusion-controlled kinetics. Activation energy analysis indicates that the diffusion of Na+ in the glass is the rate-limiting step during phase transformation. The above conclusion is further confirmed by calculated and measured results of linear growth rates.

Microstructure and Hydrogen Storage Properties of Ti-V-Fe Alloys

2016 ◽  
Vol 847 ◽  
pp. 3-7 ◽  
Author(s):  
Gang Fu ◽  
Feng Wang ◽  
Jiang Wang ◽  
Mao Hua Rong ◽  
Zhong Min Wang ◽  
...  
Keyword(s):  
Hydrogen Storage ◽  
Secondary Phase ◽  
Hydrogen Desorption ◽  
Laves Phase ◽  
Thermal Stabilities ◽  
Hydrogen Storage Properties ◽  
Dsc Measurements ◽  
Arc Melting ◽  
Fe Alloys ◽  
Storage Properties

Microstructure, hydrogen storage properties and thermal stabilities of V-Ti-Fe alloys prepared by arc-melting were studied in this work. It was confirmed that V60Ti30Fe10, V70Ti20Fe10 and V80Ti10Fe10 alloys are a body-centered cubic (bcc) single phase, while V75Ti10Fe15 alloy consists of the bcc main phase and C14-typed Laves secondary phase. Experimental results show that the V80Ti10Fe10 alloy reached the largest hydrogen absorption capacities which were about 1.9 wt.% and 1.62 wt.% at 423 K and 473 K, while V75Ti10Fe15 alloy with C14-typed Laves phase showed better hydrogen desorption capacities with 1.31 wt.% at 423 K and 1.35 wt.% at 473 K, respectively. In addition, the DSC measurements indicate that the thermal stability of V75Ti10Fe15 alloy with C14-typed Laves phase decreased, which is very beneficial to the improvement of dehydrogenation rate in the alloy.

Microstructures and Electrochemical Hydrogen Storage Properties of La0.7Ce0.3Ni3.83Mn0.43Co0.25-xAl0.26Cu0.48(Fe0.43B0.57)x Alloys

2013 ◽  
Vol 721 ◽  
pp. 59-62
Author(s):  
Yu Zhou ◽  
Xian Yun Peng ◽  
Bao Zhong Liu
Keyword(s):  
Hydrogen Storage ◽  
Discharge Current ◽  
Secondary Phase ◽  
High Rate ◽  
Electrochemical Characteristics ◽  
Hydrogen Storage Alloys ◽  
Discharge Current Density ◽  
Hydrogen Storage Properties ◽  
Electrochemical Hydrogen Storage ◽  
Storage Properties

Microstructures and electrochemical characteristics of La0.7Ce0.3Ni3.83Mn0.43Co0.25-x Al0.26Cu0.48(Fe0.43B0.57)x hydrogen storage alloys have been investigated. XRD results indicate that La0.7Ce0.3Ni3.83Mn0.43Co0.25-xAl0.26Cu0.48 alloy is single LiNi5 phase, and the alloys containing Fe0.43B0.57 are composed of LaNi5 matrix phase and La3Ni13B2 secondary phase, and the abundance of the secondary phase gradually increases with increasing Fe0.43B0.57 content. Maximum discharge capacity of the alloy electrodes monotonically decreases from 311.2 mAh/g (x = 0) to 289.6 mAh/g (x = 0.20). High-rate dischargeability at the discharge current density of 1200 mA/g first increases from 53.1% (x = 0) to 64.0% (x = 0.15), and then decreases to 56.5% (x = 0.20).

Nuclear magnetic resonance studies of proton exchange in imidate esters and amides in strong acid

1981 ◽  
Vol 59 (16) ◽  
pp. 2527-2535 ◽  
Author(s):  
Charles L. Perrin ◽  
Eric R. Johnston
Keyword(s):  
Strong Acid ◽  
Proton Exchange ◽  
Saturation Transfer ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Intramolecular Exchange ◽  
Diffusion Controlled ◽  
Amide Exchange ◽  
Rate Limiting ◽  
Kinetics Of

Saturation-transfer or lineshape measurements of kinetics of proton exchange show that HZ of ethyl acetimidate in 46% H2SO4 or ethyl N-methylformimidate in 40% H2SO4 exchanges faster than HE, and HE of protonated 2-iminotetrahydrofuran exchanges faster than HZ, as expected on the basis of the stabilities of the stereoisomeric imidate esters. In contrast, amide exchange is too fast to measure in aqueous H2SO4, but can be measured in 100% H2SO4, where HE and HZ exchange at equal rates. Also, there is intramolecular exchange occurring at this same rate. These results are interpreted as evidence for exchange in amides via the N-protonated intermediate, whose lifetime in H2SO4 is sufficiently long to permit the protons on nitrogen to become equivalent. By comparing OH exchange with NH exchange, it is concluded that N-protonation is the rate-limiting step. Even though this is a thermodynamically favorable proton transfer in H2SO4, its rate constant is significantly lower than the diffusion-controlled limit. The contrasts between imidate esters and amides and between dilute solutions and H2SO4 are discussed.

Role of intestinal basolateral membrane in absorption of nutrients

1992 ◽  
Vol 263 (3) ◽  
pp. R482-R488 ◽  
Author(s):  
C. Cheeseman
Keyword(s):  
Amino Acid ◽  
Basolateral Membrane ◽  
High Capacity ◽  
Allosteric Modulation ◽  
Transporter Protein ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Dibasic Amino Acid ◽  
Rate Limiting

Organic solutes leave the intestinal epithelium and enter the circulation via specific facilitated carriers located in the basolateral membrane. In the case of glucose it is a low-affinity, high-capacity transport system that can adapt to the carbohydrate content of the diet. Chronic diabetes also promotes the exit of glucose, and in both cases the effect results from an increased density of carriers in the basolateral membrane. In contrast, a rapid upregulation of this system that can be induced within 30 min by hyperglycemia does not involve large changes in the amount of transporter protein. Similarly, the absorptive capacity of the small intestine from some amino acids can be influenced by events occurring at the basolateral membrane. In the case of dibasic amino acid absorption, exit from the epithelium is the rate-limiting step. The activity of the basolateral carrier can be increased almost 10-fold within 60 s by the addition of micromolar concentrations of the neutral amino acid leucine to either the lumen or the plasma. This response does not involve the second messenger adenosine 3',5'-cyclic monophosphate and may represent an allosteric modulation of the carrier. These observations are discussed in relation to the role of the basolateral membrane as a locus for controlling intestinal absorption of organic nutrients.

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