Evidence for Eigenfrequencies in Dendritic Growth Dynamics

Author(s):  
Jeffrey C. LaCombe ◽  
Matthew B. Koss ◽  
Cindie Giummarra ◽  
Julie E. Frei ◽  
Afina O. Lupulescu ◽  
...  
MRS Advances ◽  
2018 ◽  
Vol 3 (22) ◽  
pp. 1201-1207 ◽  
Author(s):  
Asghar Aryanfar ◽  
Daniel J. Brooks ◽  
William A. Goddard

ABSTRACTDendritic growth during charging period is one of the main barriers for the rechargeablity of conventional batteries. Additionally this phenomenon hinders the utilization of high energy density metal candidates by limiting the safety and allowable operating condition for these devices. We address the role of square wave pulse on the growth dynamics of dendrites in the continuum scale and large time periods by formulating an analytical criterion. Our dimension-free analysis permits the application our results to a variety of electrochemical systems in diverse scales.


2000 ◽  
Vol 652 ◽  
Author(s):  
J.E. Frei ◽  
M.E. Glicksman ◽  
J.C. LaCombe ◽  
M.B. Koss ◽  
C. Giummarra ◽  
...  

ABSTRACTMicrogravity dendritic growth experiments, conducted aboard the space shuttle Columbia (STS-87) in November/December 1997, are analyzed and discussed. In-situ video images now reveal that pivalic acid (PVA) dendrites growing in the diffusion-controlled environment of low-earth orbit exhibit a range of growth behaviors, including steady, transient, and oscillatory states. The observed transient features of the growth process are being studied with the objective of understanding their physical mechanisms. Some transients in the observed growth speed are thought to arise as an intrinsic aspect of the evolving dendritic pattern. Variability in the growth speed observed from a sequence of identical runs at equal supercooling suggests that self-interactions of the dendrite remain important throughout the development of the dendritic pattern. A Greens function analysis of the near-tip diffusion sources contributing to the local field at the tip suggests that strong non-local interactions exist well into the time-dependent side-branch region of real dendrites. Video data obtained at 30 fps allow the first application of discrete Fourier transform methods (Lomb periodograms) to the digitized images of dendritic growths under quiescent microgravity conditions. These observations provide evidence for the appearance of characteristic frequencies in the tip shape and its dynamical behavior. Some of the frequency bands observed coincide closely with the ratio of the dendritic tip growth speed divided by the side branch spacing. Other observed lower frequencies remain as yet unexplained. These data, and their interpretations, are discussed in this paper.


2018 ◽  
Vol 15 ◽  
pp. 128-153
Author(s):  
Hui Xing ◽  
Xiang Lei Dong ◽  
Jian Yuan Wang ◽  
Ke Xin Jin

In this paper, we review our results from phase field simulations of tilted dendritic growth dynamics and dendrite to seaweed transition in directional solidification of a dilute alloy. We focus on growth direction selection, stability range and primary spacing selection, and degenerate seaweed-to-tilted dendrite transition in directional solidification of non-axially orientated crystals. For growth direction selection, the DGP law (Phys. Rev. E, 78 (2008) 011605) was modified through take the anisotropic strength and pulling velocity into account. We confirm that the DGP law is only validated in lower pulling velocity. For the stability range and primary spacing selection, we found that the lower limit of primary spacing is irrelative to the misorientation angle but the upper limit is nonlinear with respect to the misorientation angle. Moreover, predicted results confirm that the power law relationship with the orientation correction by Gandin et al. (Metall. Mater. Trans. A. 27A (1996) 2727-2739) should be a universal scaling law for primary spacing selection. For the seaweed-to-dendrite transition, we found that the tip-splitting instability in degenerate seaweed growth dynamics is related to the M-S instability dynamics, and this transition originates from the compromise in competition between two dominant mechanisms, i.e., the macroscopic thermal field and the microscopic interfacial energy anisotropy.


Author(s):  
Pham V. Huong ◽  
Stéphanie Bouchet ◽  
Jean-Claude Launay

Microstructure of epitaxial layers of doped GaAs and its crystal growth dynamics on single crystal GaAs substrate were studied by Raman microspectroscopy with a Dilor OMARS instrument equipped with a 1024 photodiode multichannel detector and a ion-argon laser Spectra-Physics emitting at 514.5 nm.The spatial resolution of this technique, less than 1 μm2, allows the recording of Raman spectra at several spots in function of thickness, from the substrate to the outer deposit, including areas around the interface (Fig.l).The high anisotropy of the LO and TO Raman bands is indicative of the orientation of the epitaxial layer as well as of the structural modification in the deposit and in the substrate at the interface.With Sn doped, the epitaxial layer also presents plasmon in Raman scattering. This fact is already very well known, but we additionally observed that its frequency increases with the thickness of the deposit. For a sample with electron density 1020 cm-3, the plasmon L+ appears at 930 and 790 cm-1 near the outer surface.


2020 ◽  
Vol 634 ◽  
pp. 231-236 ◽  
Author(s):  
EA McHuron ◽  
T Williams ◽  
DP Costa ◽  
C Reichmuth

Author(s):  
Saule Zhangirovna Asylbekova ◽  
Kuanysh Baibulatovich Isbekov ◽  
Vladimir Nickolaevich Krainyuk

Pike-perch is an invader for the water basins of Central Kazakhstan. These species have stable self-reproductive populations in the regional waters. Back calculation method was used to investigate pike-perch growth rates in reservoirs of K. Satpayev’s channel. For comparison, the data from the other water bodies (Vyacheslavsky and Sherubay-Nurinsky water reservoirs) were used, as well as literature data. Pike-perch species from the investigated waters don’t show high growth rates. The populations from the reservoirs of K. Satpayev’s channel have quite similar growth rates with populations from the Amur river, from a number of reservoirs in the Volga river basin and from the reservoir in Spain. Sexual differences in growth have not been observed. Evaluating possible influence of various abiotic and biotic factors on the growth rate of pike-perch in the reservoirs of K. Satpayev’s channel was carried out. It has been stated that the availability of trophic resources cannot play a key role in growth dynamics because of their high abundance. Morphology of water bodies also does not play a role, as well as chromaticity, turbidity and other optical water indicators. It can be supposed that the main factor influencing growth of pike perch is the habitat’s temperature. This factor hardly ever approaches optimal values for the species in reservoirs of K. Satpaev’s channel. The possible influence of fishing selectivity on pike-perch growth rates was also evaluated. Currently, there has been imposed a moratorium on pike-perch catch. However, pike-perch is found in by-catches and in catches of amateur fishermen. It should be said that such seizures have an insignificant role in the dynamics of growth rates.


1996 ◽  
Author(s):  
M. Glicksman ◽  
M. Koss ◽  
L. Bushnell ◽  
J. LaCombe ◽  
E. Winsa

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