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扫描电子显微镜

Scanning Electron Microscope

 
 
 
 
 

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扫描电镜应用之:金属氧化物涂覆在羰基铁粉的表征  

2010-12-31 08:32:55|  分类: 默认分类 |  标签: |举报 |字号 订阅

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作者:Sivan Salzman    Scanning Electron Microscopy Practicum MSC 507
扫描电镜实习课 理科硕士
University of Rochester, Spring 2009
罗切斯特大学 2009年春
- 驰奔 编译(转载请注明)


Abstract摘要
In this project we describe the process of characterizing coated and uncoated CI particles using the scanning electron microscopy (SEM) and other microscopic techniques acquired in the MSC 507 course. The CI particles are an integral part of the Magnetorheological finishing (MRF) process carried at the Laboratory for Laser Energetics (LLE) at the University of Rochester. The results shown here help us to get better understanding of the modification process of the CI particles and their behavior.

理科硕士507课程这个试验项目,我们来明白如何使用扫描电镜和其他显微技术表征涂覆和没哟涂覆羰基铁粉(CI )。CI颗粒是保存在LLE中的磁流变液(MRF)的主要部分。这个试验课程显示的结果,可以帮助我们对CI粒子的变化过程和他们的性质获得更好的理解。

Introduction介绍
Magnetorheological finishing (MRF) is a deterministic polishing process developed at the University of Rochester for polishing optical materials [1]. The magnetorheological (MR) fluid consists of ~80 wt% carbonyl iron (CI) particles. New MR fluid based on modified CI is studied these days at the LLE. Here we characterize modified CI particles coated with a thin layer of metal oxide (XyO2) using microscopic techniques (The specific description of the metal oxide used is not revealed here due to sensitivity of patent manners). Fresh CI and coated CI particles were viewed in the SEM and were characterized using X-ray technique. The results show the change in the CI particles shape and texture after the modification process. As part of this course requirement, other techniques were used, such as stereo pairs (3D) image and colorization of an image. 

MRF是一种成熟的确定的抛光过程,主要用于抛光光学材料。磁流变液总重量的80%是CI粒子。基于改性CI的新MR液目前在LLE研究当中。这里我们用显微技术表征改性CI粒子被涂覆一薄层金属氧化物(由于专利的敏感性,金属氧化物的详细说明不便透露)。CI颗粒和被涂覆的CI颗粒用SEM进行观察同时用X射线显微分析技术(
EDS OR WDS)。改性处理后,试验结果显示CI形状和内部结构的变化。试验课程的需要部分,也是用了其他的相关技术,例如立体对技术,伪彩色图像。

Materials and methods材料和方法
Two types of CI particles were tested in this project: 1) Fresh CI, and 2) Metal oxide coated CI. All the samples have a powder form and they were milled with mortar and pastel before attached to the SEM stub. In addition, two other samples were prepared in a form of puck by mixing CI particles powder with epoxy powder under controlled pressure and temperature. The pucks were polished using the MRF machine in order to cut the particles and obtain their cross section. The samples were prepared and examined using six techniques described in the results and discussion paragraph.

 在这个试验中,测试两种类型的CI颗粒。 1)、纯的CI    2)、被金属氧化物涂覆的CI.  样品都是粉体,在粘在样品杯之前使用研钵研磨。同时,另外在可控的压力和温度下,把CI颗粒和环氧树脂颗粒混合,准备两种冰球形状样品。为了获得颗粒剖面,使用MRF机抛光冰球。

Results and discussion 结果与讨论
This paragraph describes the techniques used to characterize the coated and uncoated particles. The differences between the two types of CI particles are shown in the attached figures and disused as well.

本段描述用于涂覆和非涂覆颗表征的技术。两种类型的CI颗粒的差别显示在附图同时进行讨论。

1. Sample coating  样品镀膜

All the samples, except of the fresh CI powder sample, were sputtered with a thin layer of gold/palladium alloy on the surface to improve their conductivity. This process allows us to reduce / prevent charging on the sample surface and improve the signal and the quality of the images taken on the SEM. The thickness of the gold/palladium conductive layer is about 20 (the samples were sputtered for 20 seconds using a current of 20mA).

 所有样品,除了纯的CI粉末样品,都需要在表面离子溅射一薄层金靶合金以改善导电性能。这个处理降低或者阻止样品荷电,改善扫描电镜图像信号质量。金靶导电层的厚度大约20nm( 离子流20mA,溅射20秒---太厚了吧?)C

2. Secondary electrons二次电子图像

The following images were taken using the secondary electron detector (SED). There are two kinds of SE detectors: SE2 and InLens. The images shown in Figures 1-3 were taken using the InLens detector (will be explained in the next paragraph). The accelerating voltage and the working distance are given at the bottom of the each image. Figure 1 shows two SEM images of fresh CI particles. Figure 2 shows two SEM images of Metal oxide coated CI particles. Figure 3 shows SEM images of the cross section of the particles that was obtained from the epoxy pucks after they were polished with the MRF machine. From the first two figures (1 and 2) we can see the change in the CI particles texture and shape. The surface of the particles in Figure 2 is rougher due to the metal oxide coating layer. Figure 3 presents two images of particles cross section. From this figure we see that the coating layer appears to be uniform, and that the particles diameter increased due to the modification process. This suggests that the coating process is accurate. in addition, the scratching and grooving marks on the cross section area of the particles are due to the polishing process of the pucks. These marks are the MR fluid signature on the surface.C

扫描电镜使用的是(fieldemissions场发射)FE-SEM,下图使用SED。电镜中有两个se探测器--在物镜下方样品室中的SE2,和在物镜上方镜筒中的SE1.(一般称作上SE和下SE,不同制造商叫法混乱,因为inlens sed名称被注册专利)。图像1-3采用SE2D,加速电压和工作距离显示在图像的底部信息区。图一显示两个纯CI颗粒SEM图像。图二显示两个被金属氧化物涂覆的颗粒。图三显示用树脂包埋后采用MRF机抛光的颗粒剖面sem图像。从图一和图二中,我们能够看到颗粒表面结构和形状。图二中的颗粒表面更粗糙,由于涂覆。图三展现两个颗粒的剖面sem图像。从这个图像中我们看到表面涂层好像是均匀的,颗粒的直径由于改性而增加。这显示涂覆处理是精确的。此外,在颗粒剖面上的划伤课槽痕迹是因为抛光处理的结果

扫描电镜应用之:金属氧化物涂覆在羰基铁粉的表征 - 驰奔 - ---DEMA 驰奔---涂覆和镀膜表面复型。溅射或者蒸发镀膜可以表面复制。


Characterizing Metal Oxide Coated Carbonyl Iron (CI) Particles - 驰奔 - ---DEMA 驰奔---
Characterizing Metal Oxide Coated Carbonyl Iron (CI) Particles - 驰奔 - ---DEMA 驰奔---
(b)
Figure 1: SEM image of fresh CI particles using the InLens detector. (a) Magnification: X 29.17K; Accelerating voltage: 5KV; Working distance: 7.9mm. (b) Magnification: X 183K; Accelerating voltage: 15KV; Working distance: 4mm.

图一:纯CI颗粒,SE2探测器。 (a) 放大倍数 29170 X, AV=5KV ,WD=7.9mm  (b) 放大倍数183000倍,AV=15KV WD=4mm

  (以上两张图像显示放大倍数实际相同,但图像显示尺寸标准依据不同)

Characterizing Metal Oxide Coated Carbonyl Iron (CI) Particles - 驰奔 - ---DEMA 驰奔---

 (a)

Characterizing Metal Oxide Coated Carbonyl Iron (CI) Particles - 驰奔 - ---DEMA 驰奔---
(b)
Figure 2: SEM image of Metal oxide coated CI particles using the InLens detector. (a) Magnification: X 17.40K; Accelerating voltage: 10KV; Working distance: 5.5mm. (b) Magnification: X 20.58K; Accelerating voltage: 10KV; Working distance: 4.4mm.

图二: 氧化物涂覆 CI颗粒, SE2探测器。

Characterizing Metal Oxide Coated Carbonyl Iron (CI) Particles - 驰奔 - ---DEMA 驰奔---

 (a)<---C

Characterizing Metal Oxide Coated Carbonyl Iron (CI) Particles - 驰奔 - ---DEMA 驰奔---
---------------------------------->(b)
Figure 3: SEM image of the cross section obtain from the polished pucks. (a) Cross section of fresh CI particle. Magnification: X 53.51K; Accelerating voltage: 10KV; Working distance: 3.9mm. (b) Cross section of Metal oxide coated CI particles. The metal oxide layer is obtained here as amorphous dark halo around the original CI particles. Magnification: X 31.16K; Accelerating voltage: 10KV; Working distance: 3.9mm. 

3. Back scattered electrons 背散射电子

One image of the Metal oxide coated particles was taken with the back scattered electron detector (BSD). Because the BS electrons are emitted from the inner part of the sample and not from its surface it is difficult to obtain the surface texture of the CI particles using these electrons signal. We present in Figure 4 a set of three images taken with the BS, SE1 and InLens detectors. This presentation allows us to judge the three detectors in our settings. By using the SE1detector we see details that we barely see in the image taken with the BS detector (for example: the pattern of the metal oxide layer). By using the InLens detector we see more details more clearly than how we see them in the image taken with the SE1 detector. It seems that the most informative image for our purposes is the image taken with the InLens detector. Therefore, in this project most of the images were taken with the InLens detector in a short working distance. 
     金属氧化物涂覆颗粒,采用
背散射电子探测器的SEM图像。因为背散射电子从样品中更深层发射的,因此bse sem图像很难获得CI颗粒表面形貌。图四展示 bse, SE1,SE2,探测器的对比。通过这些图像可以让我们判断是使用哪种探测器。SE1探测器获得细节比bsed多一点。采用SE2探测器,我们看到比se1探测到更多细节。因为SE2可以获得更好的图像细节(主要是获得SE信号主要来此初级电子束的轰击区,比较纯),因此试验项目多数使用SE2探测器,短的工作距离(高位探测器不适合长WD)。

Characterizing Metal Oxide Coated Carbonyl Iron (CI) Particles - 驰奔 - ---DEMA 驰奔---

 (a) 

Characterizing Metal Oxide Coated Carbonyl Iron (CI) Particles - 驰奔 - ---DEMA 驰奔---

 (b) 

Characterizing Metal Oxide Coated Carbonyl Iron (CI) Particles - 驰奔 - ---DEMA 驰奔---

 (c)

Figure 4: SEM images of the metal oxide coated CI particles taken with different detectors: (a) BSD, (b) SED-SE1, and (c) SED-InLens(SE2D). All images were taken under the same conditions: Magnification: X 6.62K; Accelerating voltage: 20KV; Working distance: 10.8mm. 

4. X ray diffraction pattern 应该是X射线能谱,(不是衍射)。

The X-ray diffraction for both fresh and coated (w/metal oxide) particles is shown in Figure 5 (a) and (b), respectively. The first image shows that the fresh CI sample consists of: iron (Fe), carbon (C) and aluminum (Al). The Fe element is the sample composition, while the C and the Al elements are from the carbon tape and the SEM aluminum stub. The second image (Fig. 5(b)) shows the coated CI sample that consists of: iron (Fe), carbon (C), aluminum (Al), oxygen (O) and a metal component (Xy). The additional elements in this case are the oxygen and the metal composites that appear due to the coating layer: XyO2.

图五:纯CI和涂覆CI颗粒的能谱。 纯的CI显示包含 Fe ,C,Al。铁元素是样品成分,而C和AI元素来自碳导电胶带和AI样品杯。涂覆的CI样品包含Fe,C,AL ,O, Xy(金属氧化物保密代号),这种情况下额外元素是氧和金属组分,即是XyO2涂覆材料

Characterizing Metal Oxide Coated Carbonyl Iron (CI) Particles - 驰奔 - ---DEMA 驰奔---

 (a) 

Characterizing Metal Oxide Coated Carbonyl Iron (CI) Particles - 驰奔 - ---DEMA 驰奔---

(b) 

Figure 5: X-ray diffraction pattern of: (a) Fresh CI sample, and (b) Metal oxide coated CI sample.

5. Stereo pairs - 3D image 立体对 --3D图像

One of the techniques studied in the class was the stereo pairs. This technique integrates two images that were taken in different tilting angles of the stage: image 1 with tilting angle of 0 , and image 2 with tilting angle of 4 . Then, by using Photoshop, one of the images was colored in red and the other one was colored in cyan. The combination of these two images with the different angle and color causes the 3D effect. Two examples are shown in Figure 6 (a) and (b).-

立体对技术研究. 这个技术叠加了两个不同样品台倾斜角度的图像(需要全轴对中倾斜),使用 Photoshop,一张图使用红色,另一张图使用蓝绿色。两张图合成在一起产生3D效果。 (实际应该带3D电影的眼镜才会发现真正的立体效果)

Characterizing Metal Oxide Coated Carbonyl Iron (CI) Particles - 驰奔 - ---DEMA 驰奔---

Characterizing Metal Oxide Coated Carbonyl Iron (CI) Particles - 驰奔 - ---DEMA 驰奔---

(a)<------------------------------------->(b)
Figure 6: Stereo pairs image of the fresh CI sample.

 6. Colorized images 伪彩色图像

Another technique studied in the class was image colorization. Figure 7 and 8 show images that were colorized using Photoshop.

 使用 Photoshop,加伪彩色。

Characterizing Metal Oxide Coated Carbonyl Iron (CI) Particles - 驰奔 - ---DEMA 驰奔---

 Figure 7 : Colorized image of the fresh CI sample.

Characterizing Metal Oxide Coated Carbonyl Iron (CI) Particles - 驰奔 - ---DEMA 驰奔---

Characterizing Metal Oxide Coated Carbonyl Iron (CI) Particles - 驰奔 - ---DEMA 驰奔---

-
(a)------------------------------------(b)

Figure 8: (a) Colorized image of the metal oxide coated CI sample, (b) the original image. C

Conclusions 结论
The techniques used in this project provided us information about the CI particles shape and texture before and after the metal oxide coating process. Better understanding of the modification process was achieved thanks to the SEM images and the X-ray analysis. In addition, working on this project improved my microscopic skills and experience.

这个实验项目使用的技术给我们提供在涂覆金属氧化物处理前后CI颗粒的形貌信息。多亏有了扫描电镜和X射线显微分析,获得对改性处理更好的理解。此外,在实验的工作中,提高我们的电子显微技术的技能和经验。

References
[1] S. D. Jacobs et al., Magnetorheological finishing: A deterministic process for optics manufacturing, in Optical Fabrication and Testing (SPIE, Tokyo, Japan, 1995), Vol. 2576, pp. 372382.

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