电迁移法提纯稀土金属-基本原理_百科知识_行业资讯

电迁移法也称电传输法、固态电解法，其原理是基于溶解在固体（或液态）导体中的原子在直流电场的作用下能够有顺序地迁移，特别是在金属熔点附近具有较高的迁移率。将待处理的稀土金属置于两个电极之间，施加直流电，使得杂质向一端迁移，而另一端纯度相应得到提高，实现杂质浓度的再分配。电迁移法对去除稀土金属中的O、C、N、H和部分金属杂质效果明显。一般地说，金属杂质朝阳极方向迁移，间隙杂质O、C、N、H等朝阴极方向迁移。一次提纯结束后，取其中间段再在两端施加电压进行迁移，如此反复直至达到纯度要求为止。由此可见，这种提纯方法所用设备比较简单，不足之处是提纯周期长，产率低，能耗高，目前仅在某些研究领域中制取少量超前纯金属。溶解在固体或液体中的原子，由于组分梯度、温度梯度以及电场梯度的作用而发生迁移，电迁移过程中金属纯度的变化可用下式表示：

normal style="TEXT-ALIGN: center; mso-element: frame; mso-element-frame-hspace: 9.0pt; mso-element-wrap: around; mso-element-anchor-vertical: paragraph; mso-element-anchor-horizontal: margin; mso-element-left: 111.25pt; mso-element-top: 15.7pt; mso-height-rule: exactly" align=center>ln	normal style="mso-element: frame; mso-element-frame-hspace: 9.0pt; mso-element-wrap: around; mso-element-anchor-vertical: paragraph; mso-element-anchor-horizontal: margin; mso-element-left: 111.25pt; mso-element-top: 15.7pt; mso-height-rule: exactly" align=center>c (x,∞)	normal style="TEXT-ALIGN: center; mso-element: frame; mso-element-frame-hspace: 9.0pt; mso-element-wrap: around; mso-element-anchor-vertical: paragraph; mso-element-anchor-horizontal: margin; mso-element-left: 111.25pt; mso-element-top: 15.7pt; mso-height-rule: exactly" align=center>=	normal style="TEXT-ALIGN: center; mso-element: frame; mso-element-frame-hspace: 9.0pt; mso-element-wrap: around; mso-element-anchor-vertical: paragraph; mso-element-anchor-horizontal: margin; mso-element-left: 111.25pt; mso-element-top: 15.7pt; mso-height-rule: exactly" align=center>ln	normal style="mso-element: frame; mso-element-frame-hspace: 9.0pt; mso-element-wrap: around; mso-element-anchor-vertical: paragraph; mso-element-anchor-horizontal: margin; mso-element-left: 111.25pt; mso-element-top: 15.7pt; mso-height-rule: exactly" align=center>UEL	normal style="TEXT-ALIGN: center; mso-element: frame; mso-element-frame-hspace: 9.0pt; mso-element-wrap: around; mso-element-anchor-vertical: paragraph; mso-element-anchor-horizontal: margin; mso-element-left: 111.25pt; mso-element-top: 15.7pt; mso-height-rule: exactly" align=center>－	normal style="mso-element: frame; mso-element-frame-hspace: 9.0pt; mso-element-wrap: around; mso-element-anchor-vertical: paragraph; mso-element-anchor-horizontal: margin; mso-element-left: 111.25pt; mso-element-top: 15.7pt; mso-height-rule: exactly" align=center>（	normal style="mso-element: frame; mso-element-frame-hspace: 9.0pt; mso-element-wrap: around; mso-element-anchor-vertical: paragraph; mso-element-anchor-horizontal: margin; mso-element-left: 111.25pt; mso-element-top: 15.7pt; mso-height-rule: exactly" align=center>UE	normal style="mso-element: frame; mso-element-frame-hspace: 9.0pt; mso-element-wrap: around; mso-element-anchor-vertical: paragraph; mso-element-anchor-horizontal: margin; mso-element-left: 111.25pt; mso-element-top: 15.7pt; mso-height-rule: exactly" align=center>）	normal style="TEXT-ALIGN: center; mso-element: frame; mso-element-frame-hspace: 9.0pt; mso-element-wrap: around; mso-element-anchor-vertical: paragraph; mso-element-anchor-horizontal: margin; mso-element-left: 111.25pt; mso-element-top: 15.7pt; mso-height-rule: exactly" align=center>x	normal style="TEXT-ALIGN: right; mso-element: frame; mso-element-frame-hspace: 9.0pt; mso-element-wrap: around; mso-element-anchor-vertical: paragraph; mso-element-anchor-horizontal: margin; mso-element-left: 111.25pt; mso-element-top: 15.7pt; mso-height-rule: exactly" align=center> [5]
	normal style="TEXT-INDENT: 10.5pt; mso-element: frame; mso-element-frame-hspace: 9.0pt; mso-element-wrap: around; mso-element-anchor-vertical: paragraph; mso-element-anchor-horizontal: margin; mso-element-left: 111.25pt; mso-element-top: 15.7pt; mso-height-rule: exactly; mso-char-indent-count: 1.0" align=center>co			normal style="TEXT-INDENT: 5.25pt; mso-element: frame; mso-element-frame-hspace: 9.0pt; mso-element-wrap: around; mso-element-anchor-vertical: paragraph; mso-element-anchor-horizontal: margin; mso-element-left: 111.25pt; mso-element-top: 15.7pt; mso-height-rule: exactly; mso-char-indent-count: .5" align=center>D			normal style="TEXT-INDENT: 5.25pt; mso-element: frame; mso-element-frame-hspace: 9.0pt; mso-element-wrap: around; mso-element-anchor-vertical: paragraph; mso-element-anchor-horizontal: margin; mso-element-left: 111.25pt; mso-element-top: 15.7pt; mso-height-rule: exactly; mso-char-indent-count: .5" align=center>D

式中 co——杂质的初始浓度； c (x,∞)——在处理时间t趋于∞时，沿棒长距试棒端点x处的杂质的深度； U——电迁移速率，cm²/（V·s）； E——电场强度，A/ cm²； D——扩散系数，cm²； L——试棒长度，cm。式（6-5）称为电迁移方程，它说明提高电场强度E，延长金属棒长度L，都对提高纯度有利；某元素的电迁移率U和扩散系数D是决定提纯效果的基本参数，二者之比U/D值越大，说明该元素的提纯效果越好。如从表1中碳、氮、氧在金属镥中的U/D值随温度的变化可知，元素不同，其变化规律也不同。
表1 不同温度下镥金属中杂质的U/D值电迁移温度/℃ U/D
C N O
133014501600 18.326.332.3 23.023.835.0 20.819.514.0

电迁移法提纯稀土金属-基本原理

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电迁移温度/℃	U/D
电迁移温度/℃	C	N	O
133014501600	18.326.332.3	23.023.835.0	20.819.514.0