z**h
发帖数: 224 | 1 we are trying to explain this physically. If you plot the free energy vs
compositon , you get two minimums.The nucleation and spinodal lies between
the two minimums. when the second derivative of free energy is negative , the
spinodal happens. My question was for nucleation or spinodal, we finally got
A-rich phase and B-rich phase. The initial composition lies between this two.
So if A from initial mixture goes to A-rich phase we have negative diffusion.
If A from initial mixturre goes to B-rich |
|
D********g
发帖数: 533 | 2 Spinodal Decomposition暂时没有标准的翻译方法，一般都用下面的形式翻译：
旋节线相分离(Spinodal Decomposition) |
|
S*****n
发帖数: 6055 | 3 spinodal decomposition叫旋节相分离啊
spinodal curve叫旋节线 |
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c*******n
发帖数: 1648 | 4 OK, that's interdiffusion. It's normal to see D<0 for any phase seperation
process. Because interdiffusion is totally different from the selfdiffusion.
It has two components, one is from the average mobility of the polymer pairs,
another is from the thermodynamic contribution(chi). At spinodal,actually D=0,
That's been called thermodynamic slowing down. D<0 simply means that two
components have tendency to demix.(chi>chi*) That's all. If you look at the
Fick's Law, you will find when D will be n |
|
z**h
发帖数: 224 | 5 How to explain the nucleation has positive diffusion coefficient while
spinodal has negative?
pairs,
D=0,
negative |
|
c*****e
发帖数: 238 | 6 It has something to do with the phase morphology.
I think the spinodal decomposition you referred to usually corresponds to
bicontinuous phases, in that case, the hydrodynamic effects dominate over
normal diffusion induced by the nuclei. |
|
w********h
发帖数: 12367 | 7 yes.
refer to the papers I listed before...
seperation
selfdiffusion.
spinodal,actually
the |
|
c*****e
发帖数: 238 | 8 You can read the papers listed by wonderlich.
Or you can read two papers by P.G. de Gennes and P. Pincus in JCP
the title is Dynamics of spinodal decomposition(?), 1980
Very excellent scaling argument. |
|
c*******n
发帖数: 1648 | 9 Actually what I was talking about is a physical picture in people's mind
When spinodal happens, the tiny amplitude of composition fluctuation wave
exists initally, the composition fluctuation is getting bigger and bigger
with the time. The concentration gradient is getting bigger and bigger as the
result. That's exactly what negative diffusion coeff. means!
When nucleation happens, following your way, let's say tiny amount of
B nucleat into almost 100% pure particles. As this particle grows into |
|
c*****e
发帖数: 238 | 10 Since the normal diffusion is usually pure entropic, when the enthalpic
contribution to the free energy becomes pronounced, it can dominate over the
entropy, then there might appear this negative diffusion, which is related the
concentration difference, but the real difference is governed by the chemical
potential, which still favors aggregation of similar components(A or B)
As for the difference between spinodal decomposition and nucleation, the
macroscopic difference is mainly the difference i |
|
c***r
发帖数: 4631 | 11 说上一个笑话里那个从莱特兄弟飞机上敲了块金属下来做电镜的无聊人
有一次又无聊了一把，不知道从什么地方捡了一块不知名的合金做了个
电镜样品，一做衍射，好，出来了一圈十个点。
十个点就是五折对称加一个镜面对称，当时这老家伙就傻乐，晶体学
大家都知道啊！五折对称在晶体里面是不可能的。
后来，他找到一个叫John Cahn的牛人，这个John Cahn被认为是Gibbs后对
热力学做出大贡料学家。更多人认为
他是材料学家，或者叫材料工程学家。John Cahn尽管对热力学做了很大
的贡献，他的研究通常是在冶金学背景下完成的。比如说金属里面的
spinodal之类的东西。
牛人就是牛人，John Cahn一努力，生生在另外一群无聊人的帮助下把
五折对称晶体结构的构造给想出来了。John Cahn自己认为这项工作可能
是他自己在spinodal后对科学做出的最大贡献了。但是这篇paper投到什么
地方去呢？一群人想了半天后决定投给Applied Physics Letters。两个月
后，John Cahn收到回信，说“文章内容过于倾向冶金学之雕虫小技，不
适于物理学家口味，因此不于发表”。Joh |
|
s****d
发帖数: 10 | 12 【 以下文字转载自 Joke 讨论区 】
【 原文由 spinod 所发表 】
郭靖原本是个生活极有规律的人，自从和黄蓉一起之后他的生活开始有所改变。以前郭
靖从不缺课，可黄蓉告诉他，逃课现在是一件很流行的事。郭靖想，那我就逃逻辑与思
维方式吧，反正这门课我随便怎么样也过不了的。郭靖的逃课在寝室里引起了一股风潮
，同寝室的尹志平啊，赵志敬啊都想，这个世道连郭靖都逃课了，我们还一本正经地去
上课干什么。前面我说过上逻辑与思维方式的丘处机是个脾气暴躁的老师，他当即把郭
靖等人找来一顿臭骂。郭靖说："丘老师，你关了暗吧，反正你上课说的暗啥都听不懂。
"丘老师一句话都说不出来了。以前郭靖每天早起，准时收听东广早新闻。可黄蓉又告诉
他，睡懒觉也是一件很流行的事，于是郭靖就每星期睡四天懒觉。还有三天他要早起晨
跑敲章--星期二替黄蓉敲，星期三替自己敲，星期五替杨康敲。如果有一天早上下雨，
那下一天早上他就要起来跑两次步，跑完一次跑回寝室再换一张体锻卡去敲章。如果被
体育老师发觉问他怎么一天早上来敲两个章，他就照黄蓉教他说的回答："前面跑的时候
你没给暗敲上章，暗只好再跑一次。"通常老师看他老实巴交 |
|
s****d
发帖数: 10 | 13 【 以下文字转载自 Joke 讨论区 】
【 原文由 spinod 所发表 】
关于郭靖的笨那是天赋问题，生出来就笨。郭靖没有爸爸，他妈妈是内蒙古某奶品
集团的董事长，有西北第一女强人之称，家里非常之有钱。因此还好她及早投大资本对
郭靖进行智力开发，才让郭靖中规中矩地从小学一路念到大学。郭靖妈妈老是对郭靖说
："靖儿啊，你要争气啊。家里有的是钱，你要什么就能有什么，只有学问是要不来的，
所以你一定要好好念书，将来做学问。你妈妈就吃了没文化的苦头，你爸爸才会被那个
叫段天德的贱人骗走。妈妈这几年拼命赚钱，就是为了让你能在大学里做学问，没钱哪
能有闲工夫做学问啊？你不要辜负你妈妈啊！"所以郭靖的前途是他妈妈帮他树立好的：
考大学--考研--留校--争取当教授。他从没多想过以后的事。可进大学后他的前途受到
了动摇。 |
|
s****d
发帖数: 10 | 14 【 以下文字转载自 Joke 讨论区 】
【 原文由 spinod 所发表 】
发信人: flyings (fifi), 信区: FDU_Chinese
标 题: 大学生郭靖（九）
发信站: 日月光华站 (Thu Apr 26 16:12:05 2001) , 站内信件
考历史系是郭靖自己选的，整个历史系也只有他是以第一志愿考进来的。郭靖觉得
学历史比较容易，可以搞搞不用脑子的考据文献什么的，要做学问他也只有这个可以做
了。可是进了历史系他大失所望，考试居然还是有那么多东西要背的。高考的时候郭靖
已经吃够了背书的苦头，背什么政治历史人家背两三遍就记住了，他要背上二十遍三十
遍，还要吃大量"忘不了"什么的（虽然吃这种东西没什么用可他妈妈认为聊胜于无反正
家里有的是钱就一大批一大批地买回来直到有一次郭靖吃得拉肚子为止）。好不容易捱
到了大学想不到大学里要背的东西居然还要多。比如上学期那个变态系主任柯镇恶上第
一节课就在那儿说："我不会为难你们的。"可是一学期下来，郭靖记了整整三大本笔记
，差点没背得死过去。还好柯老师眼睛不大好，郭靖考试的时候占了不少便宜，才没被
关。
由 |
|
l****u
发帖数: 3449 | 15 【 以下文字转载自 Physics 讨论区 】
发信人: lotayu (罗大佑), 信区: Physics
标 题: paper help
发信站: BBS 未名空间站 (Sun Dec 19 16:51:04 2010, 美东)
de Fontaine, D.: Spinodal and Equilibrium Reactions; Physica B, 103, 57-66
(1981)
Kogachi, M., and Nakahigashi, K.: Phase Relations in the Cu3Ag1-xAux,
Ag3Au1
-xCux and Au3Cu1-xAgx Ternary Systems; Jpn. J. Appl. Phys., 19, 1443-1449
(1980)
Kogachi, M., Nakahigashi, K.: Phase Relations in the AuCu1-yAgy and Au(Cu1
-yAgy)3 Ternary Systems; Jpn. J. Appl. Phys., 24, 121-125 (1985)
请发... 阅读全帖 |
|
|
d****n
发帖数: 397 | 17 【 以下文字转载自 Physics 讨论区 】
发信人: dragon (dragon), 信区: Physics
标 题: gas phase nucleation问题求教
发信站: BBS 未名空间站 (Sat Mar 16 00:45:57 2013, 美东)
版上大牛，
我有个问题。就是gas phase nucleation.我们都知道pure water在0度以下，-40度
以上是不会结冰的。这是因为要形成冰核，必需翻越一个能垒。这个能垒联接了过冷水
（metastable state)和冰(stable state).同样也有过热蒸汽。当一个gas phase
species的浓度大于它的饱和蒸汽压的时候，它也不会形成droplet。所以nucleation(
形成droplet的过程),也是有个能垒。这个能垒和nucleation 速率有关，就是物理化学
（化学物理）里面的transition state theory.这个nucleation rate很早就已经有人
研究，Gibbs就提出classical nucleation theory.这个理论后来被发... 阅读全帖 |
|
g*****a
发帖数: 340 | 18 另外一篇灌水文章，需要自己推荐reviewer, 开始随便找了几个都不搭理，有愿意帮忙
的么？虽然杂志排名低，但多少也算审稿，申请绿卡什么的应该有用的。。。
1. Title and the central theme of the article.
Paper title: "A MATLAB Program for Quantitative Simulation of Self-assembly
of Polymer Blend Films with Nano-scaled Features". This paper introduced the
introduction to the fundamentals, design principles, and scientific use
cases of a computer program for simulation of self-assembly of polymer blend
films with nano-features.
2. Which subject/theme of the Journal the mate... 阅读全帖 |
|
c*****e
发帖数: 238 | 19 这个只是一个一般的观点吧,实验可以测出concentration fluctuation,但不能确定
是否能引发phase separation/transition.
实际的情况是,在spinodal以后,任何微小的fluctuation都可以导致phase transition,
只要在q*有fluctuation.
但在亚稳区就不是一样了,通常需要比较大的fluctuation才能越过barrier.
所以要确定实际的phase transition point,就必须考虑fluctuation.
事实上,正是因为fluctuation任何体系才会回到equilibrium,或者到能量的最低态. |
|
c*****e
发帖数: 238 | 20 好像是有通过light scattering来测量structure factor的,在spinodal附近确实有peak
在q*,大概算是测定fluctuation的大小吧. |
|
z**h
发帖数: 224 | 21 neutron scattering
factor的,在spinodal附近确实有peak
定
transition,
. |
|
|
c*****e
发帖数: 238 | 23 最好详细说说,当初好像记得这个,现在记不清了.
不过应该是说的morphology的演变吧,比如coarsening什么的? |
|
c*******n
发帖数: 1648 | 24 Interdiffusion coeff. or selfdiffusion coeff?
If it's inter diffusion coeff. why it's surprising to know it's a negative
number at the phase seperation? If you say self diffusion, then I also want to
know the answer. |
|
w********h
发帖数: 12367 | 25 I think it is interdiffusion bah..
I never heard of negative diffusion coefficient...//expect more details.
Here are some papers, I don't know if they are helpful or not:
(1)
Spontaneous Double Phase Separation Induced by Rapid Hydrodynamic Coarsening
in Two-Dimensional Fluid Mixtures
Physical Review Letters Volume: 81, Issue: 2, July 13, 1998. pp. 389-392.
Tanaka, Hajime; Araki, Takeaki
(2)
New mechanisms of droplet coarsening in phase-separating fluid mixtures
The Journal of Chemical Physics V |
|
z**h
发帖数: 224 | 26 the question is a component diffuses from low concentration to high
concentration.
to |
|
c*****e
发帖数: 238 | 27 I think that's related to coarsening..
Usually the region with high concentration also has small curvature, and thus
the chemical potential of the boundaries is lower. |
|
c*******n
发帖数: 1648 | 28 Hoho, here is the big trap!
Personally, I never looked into this situation
However, based on my limited knowledge in crystallization
I guess in ur case, the nuclei are very pure particles initially
That means infinite sharp concentration gradient on interface
This concentration gradient relax with the time. That's the reason |
|
c*******n
发帖数: 1648 | 29 hard to follow, more detail? |
|
c*******n
发帖数: 1648 | 30 Thanks a lot. Maybe you guys concentrated on the internal reasons. Actually
from the first principle of interdiffusion, the change of concentration
gradient profile with time near the interface tells all.
to
over |
|
z**h
发帖数: 224 | 31 若自由能vs composition 有两个最小点，
则相转变不论spinodal or nucleation, 最终两相的
组分应相同。 |
|
z**h
发帖数: 224 | 32 polymers.
any connection between spinodal decompostion and nanophase seperation of
diblock copolymers? |
|
|
|
g*****a
发帖数: 340 | 35 另外一篇灌水文章，需要自己推荐reviewer, 开始随便找了几个都不搭理，有愿意帮忙
的么？虽然杂志排名低，但多少也算审稿，申请绿卡什么的应该有用的。。。
1. Title and the central theme of the article.
Paper title: "A MATLAB Program for Quantitative Simulation of Self-assembly
of Polymer Blend Films with Nano-scaled Features". This paper introduced the
introduction to the fundamentals, design principles, and scientific use
cases of a computer program for simulation of self-assembly of polymer blend
films with nano-features.
2. Which subject/theme of the Journal the mate... 阅读全帖 |
|
s****a
发帖数: 238 | 36 Many old professorsin MSE department don't care Adv.Mater, Nano letter, and
even
Nature or Science. They think they just publish some fancy picture but not
so
serious.
They only concern Acta, or Metallurgical Transaction.
I've worked on physical metallurgy for 7 year and I'm so sad to see this
field
is almost dead. It's a very interesting field, a lot of phenomenon haven't
been
well explained. I like martensite, autensite, spinodal decomposition, O-
lattice
...much more than the f*** protein I h |
|
|
l****u
发帖数: 3449 | 38 de Fontaine, D.: Spinodal and Equilibrium Reactions; Physica B, 103, 57-66
(1981)
Kogachi, M., and Nakahigashi, K.: Phase Relations in the Cu3Ag1-xAux,
Ag3Au1
-xCux and Au3Cu1-xAgx Ternary Systems; Jpn. J. Appl. Phys., 19, 1443-1449
(1980)
Kogachi, M., Nakahigashi, K.: Phase Relations in the AuCu1-yAgy and Au(Cu1
-yAgy)3 Ternary Systems; Jpn. J. Appl. Phys., 24, 121-125 (1985)
请发送s************[email protected]
多谢多谢! |
|
d****n
发帖数: 397 | 39 版上大牛，
我有个问题。就是gas phase nucleation.我们都知道pure water在0度以下，-40度
以上是不会结冰的。这是因为要形成冰核，必需翻越一个能垒。这个能垒联接了过冷水
（metastable state)和冰(stable state).同样也有过热蒸汽。当一个gas phase
species的浓度大于它的饱和蒸汽压的时候，它也不会形成droplet。所以nucleation(
形成droplet的过程),也是有个能垒。这个能垒和nucleation 速率有关，就是物理化学
（化学物理）里面的transition state theory.这个nucleation rate很早就已经有人
研究，Gibbs就提出classical nucleation theory.这个理论后来被发展到
multicomponent很复杂的公式。但是这个理论有个不好的地方是（1）它要surface
tension.这是一个宏观量，当droplet很小的时候不一定准。（2）当supersaturation
接近spinodal decomposition的时候，能垒... 阅读全帖 |
|
