辉光放电质谱法直接分析石墨中痕量杂质

引用本文

王梓任, 王长华, 胡芳菲, 李继东. 辉光放电质谱法直接分析石墨中痕量杂质. 光谱学与光谱分析, 2019,39(4): 1256-1261
WANG Zi-ren, WANG Chang-hua, HU Fang-fei, LI Ji-dong. Quantification of Trace Impurities in Graphite by Glow Discharge Mass Spectrometry. Spectroscopy and Spectral Analysis, 2019,39(4): 1256-1261. 复制到剪切板

Doi: 10.3964/j.issn.1000-0593(2019)04-1256-06
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光谱学与光谱分析所有

辉光放电质谱法直接分析石墨中痕量杂质

王梓任, 王长华, 胡芳菲, 李继东^*

国标(北京)检验认证有限公司, 北京 100088

*通讯联系人 e-mail: lijidong@grinm.com

作者简介: 王梓任, 1992年生, 国标(北京)检验认证有限公司硕士研究生 e-mail: warcraftrain@126.com

收稿日期: 2018-03-09 接受日期: 2018-07-21

基金项目: 国家重点研究发展计划项目(2016YFF0100100)资助

摘要

石墨是理想的无机非金属材料, 具有高化学稳定性、良好的导电性、较好的耐磨性等优点, 被广泛应用于现代化学工业及其他诸多领域。由于石墨是难熔物, 其中的微量杂质元素使用普通化学法或常规仪器分析法均难以准确检出。常用的火法-电感耦合等离子质谱(ICP)方法检测石墨存在的问题是: (1)在高温灼烧期间个别元素容易损失; (2)在加酸溶解灰化组分过程中部分杂质氧化物仍无法溶解完全。因此, 很多学者开始研究利用固体进样法来测定石墨中的杂质元素含量。辉光放电质谱法(GDMS)是将辉光放电源(GD)与质谱分析方法(MS)联用的一种技术, 采用固体进样方式, 具有样品前处理简单、基体效应小、检出限低、灵敏度高等优点, 在国内外已成为部分高纯金属和半导体材料分析领域的标准方法。灵敏度因子值(RSF)是一个用于校正GDMS分析结果的系数, 对于GDMS分析而言, 大部分元素在不同基体中仍然存在较明显的基体效应。要将GDMS分析作为一种定量分析方法, 需要采用与基体匹配的标准物质来校正RSF, 但目前大多数GDMS分析均采用仪器厂家提供的标准相对灵敏度因子(RSF_Std)进行测定, 只能获得半定量分析结果。研究了采用GDMS直接测定石墨样品中9种杂质元素含量的方法, 通过对放电条件等参数的优化选择, 确定了石墨分析的最佳放电条件(电流强度为55 mA, 放电气体流量为450 mL·min^-1)。在此条件下采用半定量法(RSF_Std)测定了石墨参考样品中Mg, Cr, Ni, Ti, Fe, Cu, Al, Si, Ca共九种杂质元素含量, t检验结果表明, 多数元素测量结果与参考值存在显著差异。要获得更为准确的结果, 需要获得各元素相应的RSF _x以建立定量分析方法。通过实验, 考察了不同的电流强度和放电气体流量对九种元素RSF值的影响, 讨论了影响因素产生的原因。实验结果表明, 电流强度和放电气体流量对大部分元素的RSF值都有较大的影响, 其中放电气体流量对RSF值影响最大, 各元素的RSF值变化幅度在15%和405%之间。在选定条件下采用RSF_x值定量分析了石墨材料中Mg, Cr和Ni等九种杂质元素含量, 检测结果的 t检验sig值均大于0.05, 表明测定结果与参考值无显著性差异, 方法的准确度有了显著提高; 测定结果的精密度(RSD)介于3.2%~9.9%之间, 方法可满足4N纯度以上高纯石墨材料的分析。

关键词: 辉光放电质谱法; 石墨材料; 9种杂质元素; 分析条件; 相对灵敏度因子值(RSF)

中图分类号:O657.6 文献标识码:A

Quantification of Trace Impurities in Graphite by Glow Discharge Mass Spectrometry

WANG Zi-ren, WANG Chang-hua, HU Fang-fei, LI Ji-dong^*

Guobiao (Beijing) Testing & Certification Co., Ltd., Beijing 100088, China

Abstract

Graphite material is an ideal inorganic non-metallic material with high chemical stability, good conductivity, and good wear resistance. As graphite is a refractory substance, it is difficult to test the trace element contents by using common chemical methods or conventional instrumental analyses. Common problems in the graphite analysis by the Fire-ICP method are as follows: (1) the individual elements are easily lost during the high temperature burning pretreatment process, and (2) the graphite cannot be dissolved completely during the process of adding acid dissolution. Therefore, many scholars began using solid analytical technology to determine the impurity contents in graphite. Glow discharge mass spectrometry (GDMS) is a technology combining glow discharge power supply (GD) with mass spectrometry (MS). It has advantages of simple pretreatment, weak matrix effect, low detection limit and high sensitivity. It has become a division of high pure metal and semiconductor materials at home and abroad. Relative sensitivity factor (RSF) is a coefficient used to correct GDMS analysis results. For GDMS analysis, most elements still have obvious matrix effect in different matrixes. In order to make GDMS analysis as a quantitative analysis method, it is necessary to use the standard material matching the matrix to correct the RSF. However, most of the GDMS analysis is based on the standard relative sensitivity factor (RSFStd) provided by instrument manufacturers and only semi quantitative analysis results can be obtained. This paper describes an analytical method to determine the content of 9 elements in graphite materials using GDMS. Through the optimization of the discharge conditions, the suitable discharge conditions of graphite were determined (current intensity as 55 mA, discharge gas flow rate as 450 mL·min^-1). Under optimized analytical conditions, 9 impurities (Mg, Cr, Ni, Ti, Fe, Cu, Al, Si and Ca) were determined. The result of t-test showed that there was significant difference between the results of most elements and the reference value. In order to obtain more accurate results, the corresponding RSFx of each element was required to establish quantitative analysis methods. Through experiments, the effects of different current intensity and discharge gas flow on the RSF value of 9 elements were investigated, and the causes of the influencing factors were discussed. The experimental results showed that the current intensity and discharge gas flow have a great influence on the RSF value of most elements. The discharge gas flow has the greatest influence on the RSF value, and the RSF value of each element varies between 15% and 405%. Under selected conditions, the content of 9 impurity elements, such as Mg, Cr and Ni in graphite materials, was quantitatively analyzed by RSF _x value. The t-test sig value of the test results was more than 0.05, indicating that there was no significant difference between the measured results and the reference value, and the accuracy of the method was significantly improved. The relative standard deviations (RSD) were between 3.2% and 9.9%. The method can meet the need for the analysis of high purity graphite materials above 4N purity.

Key words: Glow discharge mass spectrometry; Graphite material; 9 impurity elements; Discharge condition; Relative sencitivity factor values

文章图片

引言

石墨是理想的无机非金属材料, 具有高化学稳定性、良好的导电性、较好的耐磨性等优点, 被广泛应用于现代化学工业及其他诸多领域^{[1, 2, 3]}。

由于石墨是难熔物, 其中的微量杂质元素使用普通化学法或常规仪器分析法均难以准确检出。常用的火法-电感耦合等离子质谱(ICP)方法检测石墨^[4]存在的问题是: (1)在高温灼烧期间个别元素容易损失; (2)在加酸溶解灰化组分过程中部分杂质元素氧化物仍无法溶解完全。因此现在有很多学者开始研究利用固体进样方法来测定石墨中杂质元素含量^{[5, 6, 7]}。

辉光放电质谱法(glow discharge mass, GDMS)是将辉光放电源(glow discharge, GD)与质谱分析方法(MS)联用的一种分析技术, 具有前处理简单、检出限低、灵敏度高等优点, 在测定高纯金属中杂质元素含量方面具有显著的优势^{[8, 9, 10, 11, 12]}, 该方法在国内外已被用作部分高纯金属和半导体材料的标准分析方法, 但对石墨材料中杂质元素的检测尚未见报道。

RSF是一个用于校正GDMS分析结果的系数, 对于GDMS分析而言, 大部分元素在不同基体中仍然存在较明显的基体效应^{[13, 14, 15, 16, 17]}。将GDMS分析作为一种定量分析方法, 需要采用与基体匹配的标准物质来校正RSF, 但目前大多数GDMS分析均采用仪器厂家提供的标准灵敏度因子(RSF_Std)进行测定, 只能获得半定量分析结果。

本工作采用GDMS法对石墨材料中九种杂质元素的含量进行测定, 利用石墨参考样品考察不同实验条件对各元素RSF值的影响, 探索建立石墨材料中杂质元素含量的GDMS定量分析方法。

1 实验部分

1.1 仪器和试剂

Element GD辉光放电质谱仪: 美国Thermo Fisher公司产品, 表1为辉光放电质谱仪工作参数。

表1 辉光放电质谱仪的工作参数 Table 1 Operating parameters of GDMS

表2 元素质量数选择和质谱干扰 Table 2 Element mass selection and mass spectrometry interference

高纯石墨样品(5N纯度)和两块石墨参考样品: 北京有色金属研究总院提供, 各元素参考含量见表3和表4。

表3 石墨参考样品A中九种元素的分析结果 Table 3 Analytical results of 9 elements in graphite reference sample A

1.2 待测元素质量数选择

以选择同位素丰度高、质谱干扰小为原则, 选择合适的待测元素质量数进行测定, 具体信息列于表2, 其中“ Distinguishing ability” 指设置仪器分辨率为10 000时是否能区分待测峰和干扰峰情况。

由表2可知, 其中仅有待测元素⁸⁸Sr⁺⁺对于⁴⁴Ca的干扰需要10 000以上的分辨率才可以分开, 通过测定, 发现待测样品中Sr含量未检出, ⁸⁸Sr⁺⁺对于⁴⁴Ca的干扰可忽略。其他待测元素的潜在干扰峰在10 000分辨率时均可以完全分开, 测定时可不考虑这些元素的潜在质谱干扰。

1.3 样品

石墨样品切割成尺寸约为5 cm× 4 cm× 2 cm的块状, 用800目砂纸打磨表面, 去离子水清洗, 酒精棉擦拭后用1∶ 1硝酸浸泡3 min, 去离子水二次冲洗, 高纯氮气吹干后备用。

2 结果与讨论

2.1 放电条件优化

为了确定最优放电条件, 考察了¹²C, ²⁴Mg, ⁴⁴Ca, ⁶³Cu和220(背景噪声)五个质量数处的信号强度随放电电流和放电气体流量改变产生的变化情况。

2.1.1 放电电流强度的选择

设定放电气体流量为450 mL· min^-1, 选择放电电流梯度为45, 50, 55, 60和65 mA, 实验结果如图1所示。

	Figure Option View Download New Window
	图1 放电电流强度对信号强度和精密度的影响Fig.1 The effects of discharge current for signal intensity and precision

由图1可知, 随着电流强度的增大, 四种元素的信号强度均呈逐渐增强趋势。放电电流在45~55 mA间变化时, 所有元素的信号强度均随电流强度的增加明显增大; 除Mg以外, 电流超过55 mA后各元素信号强度增大趋势逐渐减小, 而Mg元素信号强度在55~60 mA间略有减小; 从精密度来看, 各元素信号强度的相对波动均在5%以内, 无明显变化。太大的电流强度会增加碳在阳极上的沉积速度, 沉积物增多最终会导致放电短路, 缩短放电时间; 同时, 沉积物的增多也会导致检测信号的稳定性变差, 影响测定结果的精密度。综合考虑, 选择55 mA作为放电电流进行实验。

2.1.2 放电气体流量的选择

设定放电电流为55 mA, 选择放电气体流量梯度为375, 400, 425, 450, 475和500 mL· min^-1, 实验结果如图2所示。

	Figure Option View Download New Window
	图2 放电气体流量对信号强度和精密度的影响Fig.2 The effects of discharge gas flow rate for signal intensity and precision

由图2可知, 随着放电气体流量的增大, C信号强度呈先增大后减小的趋势, 在425~475 mL· min^-1间基本保持不变; 对于Mg, Ca和Cu三元素, 随着放电气体流量的增大, 信号强度呈逐渐减小趋势; 从精密度来看, 各元素信号强度的相对波动均在5%以内, 无明显差异。综合考虑信号强度和精密度变化情况, 最终选择放电气体流量为450 mL· min^-1进行实验。

2.1.3 放电条件变化对背景噪声的影响

由实验数据可知, 在实验条件范围内无论电流和放电气体流量如何改变, 220质量数处的信号始终保持在0~1 cps之间, 表明仪器的背景噪声未受放电条件变化的影响。

2.2 预溅射时间选择

实验通过监测Na元素含量变化来确定样品预溅射时间的长短, 以除去可能存在于样品表面的污染, 设定放电电流为55 mA, 放电气体流量为450 mL· min^-1。图3为样品表面Na含量随溅射时间的变化情况。

	Figure Option View Download New Window
	图3 石墨样品中钠含量与溅射时间的关系Fig.3 The relationship between Na content in graphite sample and sputtering time

由图3可知, 随着放电进行, Na含量逐渐降低, 至15 min后下降趋势减缓, 18 min以后基本稳定, 表明样品表面确实存在一定的污染情况。实验选择18 min作为预溅射时长, 以去除样品表面存在的污染。

2.3 方法的检出限、准确度和精密度

在选定的优化测定条件下, 采用仪器自带的RSF_std对高纯石墨样品独立进行11次分析, 统计测定结果标准偏差, 以3倍标准偏差计算方法的检出限; 对石墨参考样品A进行平行六次测定, 统计准确度和精密度; 对测定结果与参考值进行单变量t检验, 选择置信区间为95%, 所得sig值见表3。若sig> 0.05, 表示测定结果与参考值无显著差异。 w₁代表被测元素的参考含量, w₂代表该元素的平均测定含量。

由表3可知, 各元素测定结果的相对标准偏差(relative standard deviation, RSD)介于2%~10%之间。对于低含量元素如Mg和Ni, RSD值较大, 在8.5%左右。实验结果表明, 该法测定石墨材料中杂质元素的精密度良好。 t检验结果表明, 对于Si和Ca两元素, 检测结果与参考值无显著差异, 对于其他元素则存在显著差异。因此, 有必要通过技术改进进一步提高本方法的测量准确度。拟通过实验获得优化条件下的各元素RSF_x值并校正检测结果, 以获得更准确的定量分析结果。

2.4 相对灵敏度因子(relative sensitixity factor, RSF)测定

相对灵敏度因子的计算方法见式(1)和式(2)。

$\begin{array}{l} c_{k} = \frac{I_{x}}{I_{m}} \end{array}$ (1)

$RS F_{x} = \frac{c_{x}}{c_{k}}$ (2)

其中, c_k是元素的表观测定含量, I_x和I_m分别是待测元素和基体元素的离子计数强度(丰度校正后), c_x是参考样品中元素的参考含量。

2.4.1 电流强度对RSF值的影响

设定放电气体流速为450 mL· min^-1, 依次考察放电电流为40, 45, 50, 55和60 mA对各元素RSF值的影响, 实验结果见图4。

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	图4 待测元素RSF值随着电流强度的变化趋势Fig.4 Trend of RSF value of element tested with current intensity

由图4可知, 大多数元素的RSF值随着电流强度的增加有逐步增大的趋势。多数元素RSF值在50~55 mA范围内相对保持稳定, 在55~60 mA范围内个别轻元素(如Mg, Al和Si)RSF值明显增大, 重元素(Cr, Ni, Cu)RSF值呈减小趋势。从变化幅度来看, Mg, Al和Si的RSF值变化幅度超过40%, 其他元素如Ca, Cr, Ni和Cu的RSF值的变化幅度在10%左右。实验结果表明, 轻元素RSF值更容易受放电电流的影响, 原因可能是轻元素原子在石墨材料中具有更高的溅射率, 随着放电电流增强, 其原子的溅射速率快速增大, RSF值也随之明显改变; 其他元素的溅射率受放电电流强度影响较小, 因此RSF值保持相对稳定。综上所述, 放电电流对石墨材料中多数元素的RSF值有较大影响。

2.4.2 放电气体流量对RSF值的影响

放电电流设定为55 mA, 在400~500 mL· min^-1范围内依次改变放电气体流量, 考察放电气体流量对RSF值的影响。实验结果见图5。

	Figure Option View Download New Window
	图5 待测元素RSF值随放电气体流量的变化趋势Fig.5 Trend of RSF value of element tested with gas flow rate

由图5可知, 随着放电气体流量的增大, 各元素RSF值均发生了明显变化。 Si元素RSF值增大了近15%, 而Ca, Ti, Fe和Cu的RSF值增幅在100%以上, 其他元素的RSF值增幅也都超过了30%。不断增大的气体流量会导致被溅射出来的粒子密度降低, 但同时各元素的溅射或电离效率获得提高。大多数元素RSF值随着放电气体流量的增加而增大, 原因可能在于各元素溅射或电离效率提高带来的加强效果超过了气体稀释效应, 表现为多数元素的RSF值逐渐增大; 在气体流量介于475~500 mL· min^-1范围时, Si和Cu的RSF值略有减小, 可能的原因是气体的稀释效应过大, 导致RSF值变小。综上所述, 放电气体流量对石墨中各元素的RSF值有显著的影响。

2.5 样品分析

在优化放电条件(放电电流为55 mA, 放电气体流量为450 mL· min^-1)下, 采用该条件下获得的RSF_x值对石墨参考样品B进行了六次重复测定, 所得结果见表4, 其中w₃是石墨参考样品B中各杂质元素的参考含量, w₄是利用仪器自带RSF_std测定获得的各元素含量, w₅是利用获得的RSF_x值测定结果; sig₁和sig₂分别对应为w₄和w₅测定结果与参考值的t检验结果。

表4 实际样品分析 Table 4 Sample analysis

由表4数据可知, 利用RSF_x值进行测定和计算的检测结果sig值均大于0.05, 表明采用RSF_x进行测定的结果更接近参考值, 方法的准确度有了显著提高。

3 结论

建立了采用GDMS法定量分析石墨材料中9种杂质元素含量的方法, 方法具有良好的准确度和精密度; 研究了不同放电条件对各元素RSF值的影响, 研究结果表明大部分元素的RSF值会受放电条件的影响, 其中放电气体流量对RSF值有更为显著的影响。利用优化条件下获得的RSF_x测定各元素含量, 获得了满意的分析结果, 方法可满足4N以上纯度石墨样品中杂质元素含量的分析要求。

The authors have declared that no competing interests exist.

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[7]	WANG Zi-ren, PAN Yuan-hai, LI Ji-dong(王梓任, 潘元海, 李继东). Chinese Journal of Analysis Laboratory(分析试验室), 2017, 36(11): 1320. [本文引用:1]
[8]	YANG Hai-an, LUO Shun, LIU Ying-bo(杨海岸, 罗舜, 刘英波). Yunnan Metallurgy(云南冶金), 2015, (3): 61. [本文引用:1]
[9]	Konarski P, Kaczorek K, Kaliński D. Surface and Interface Analysis, 2013, 45(1): 494. [本文引用:1]
[10]	Marisa Di Sabatino. Measurement, 2014, 50: 135. [本文引用:1]
[11]	HU Fang-fei, WANG Chang-hua, LI Ji-dong(胡芳菲, 王长华, 李继东). Journal of Chinese Mass Spectrometry Society(质谱学报), 2014, 35(4): 335. [本文引用:1]
[12]	LIU Hong, WEI Ru-xin, LI Ai-chang(刘红, 魏茹欣, 李爱嫦). Chinese Journal of Analysis Laboratory(分析试验室), 2018, (2): 188. [本文引用:1]
[13]	LIU Jie, QIAN Rong, ZHUO Shang-jun(刘洁, 钱荣, 卓尚军). Chinese Journal of Analytical Chemistry(分析化学), 2012, 40(1): 66. [本文引用:1]
[14]	TANG Yi-chuan, ZHOU Tao, XU Chang-kun(唐一川, 周涛, 徐常昆). Journal of Instrumental Analysis(分析测试学报), 2012, (6): 664. [本文引用:1]
[15]	WEI Xing-lian, WANG Li-ping, QIN Zhen(魏兴俭, 王丽萍, 秦震). Journal of Chinese Mass Spectrometry Socieuy(质谱学报), 2016, (4): 343. [本文引用:1]
[16]	HUANG Jin, GUO Bin-bin, ZHENG Qing-hong(黄瑾, 郭斌斌, 郑清洪). Chinese Journal of Analysis Laboratory(分析试验室), 2016, 35(7): 765. [本文引用:1]
[17]	Marisa Di Sabatino, Anne L Dons, Joachim Hinrichs. Spectrochimica Acta Part B: Atomic Spectroscopy, 2011, 66(2). [本文引用:1]

2015

0.0

GAO

Tian-ming

, CHEN

Qi-shen

, YU

Wen-jia

(高天明, 陈其慎, 于汶加). Resource Science(资源科学), 2015, 37, 1059.

The application scope of graphite changed from traditional industries such as refractory,crucible,and casting to the sealing,lubricating,and electronic information industries through the use and development of new products,expanded graphite and graphite milk. With intensive research on the structural properties of graphite,it will likely become the raw material of new energy and new material industry. Graphite is a necessary raw material for traditional industries and strategic emerging industries,and has become an important strategic resource for the development of high technology. Many analyses of graphite resource demand have focused on recent demand only or the subjective projection of long-term change. Here,we predict future graphite consumption based on graphite consumption sectors and account for each industry’s graphite demand and total demand scale,and future development. Forecasts of future demand for steel casting,refractory materials,sealing materials,brake materials,lubricants,adsorbent and battery electrode industries show that by 2020 the demand in China for graphite volume will reach 1 000 thousand ton,1.42 times that of 2010. Demand will reduce in refractory industry,while demand will double that distance in ten years in sealing,lubricating,and battery electrodes industry. We found that the graphene preparation method will produce great uncertainty for graphite demand. The future graphite consumption pattern determining the Chinese graphite industry will be developed from material level production to professional and deep processing production,cultivation of electrical carbon graphite materials industry chains and new material industry chains,and development of infrared electrothermal graphite material,graphite polymer material additive,graphite fluoride and isotropic graphite.

1. Institute of Geographic Sciences and Natural Resources Research,Chinese Academy of Sciences,Beijing 100101,China; 2. Research Center for Strategy of Global Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China

天然石墨是传统工业和战略性新兴产业所必须的矿物原料,成为支撑高新技术发展的重要战略资源。本文从天然石墨消费的主要部门,核算各产业石墨的需求量及未来发展方向。对耐火材料、钢铁铸造、密封材料、制动材料、润滑剂、吸附剂、电池电极等产业的未来需求预测,结论为：到2020年中国石墨需求量将达到100万t,是2010年的1.42倍;耐火材料行业需求量将减少,而密封、制动材料,润滑、吸附剂及电池电极等行业需求将翻番。石墨烯具有广阔的应用前景,但2020年前石墨烯产业难以改变天然石墨的消费格局。未来石墨的消费格局决定了中国石墨产业将从材料级产品向专业级产品深加工方向发展,重点培育电碳石墨材料产业链和新兴材料产业链,开发石墨红外电热材料、石墨高分子材料添加剂、氟化石墨、各向同性石墨等产品。

... 引言石墨是理想的无机非金属材料, 具有高化学稳定性、良好的导电性、较好的耐磨性等优点, 被广泛应用于现代化学工业及其他诸多领域^[1,2,3] ...

2014

0.0

ZHANG

Yun-qiu

, LIANG

Yong-ming

, ZHOU

Jian-xin

(张芸秋, 梁勇明, 周建新). Acta Chimica Sinica(化学学报), 2014, 72, 367.

Doping is the most feasible and convenient method to modulate the band structure of graphene from semimetal to p-type or n-type material. In recent years, the chemical vapor deposition methods have been well developed to grow graphene layer with high quality and large area. This paper briefly reviews the recent research progress on doping methods of CVD graphene, including the doping effects by metals, small molecules, chemical reactions and replacement of lattice atoms. The methods of bilayer graphene band regulation as well as the fabrication of graphene p-n junction are also introduced, and the future tendency and potential applications of doped graphene are proposed. For graphene, it is relatively easy to produce p-type doping via surface absorption, exposing pristine graphene in those molecules with electron withdrawing groups (H2O, O-2, N-2, NO2, PMMA et al.) will lead to evident p-type doping, and graphene of this kind of p-type doping can rapidly recover to its original state when doping molecules are removed. If boron source was introduced into the CVD growth process of graphene, substitutional p-doping that some carbon atoms in graphene hexagonal lattice are replaced by boron atoms can be formed. Compared to the p-type doping, stable n-type doping is not facile for graphene. It has been proved that some electron-donating molecules such as ammonia, potassium, phosphorus, hydrogen and poly(ethyleneimine) (PEI) can produce n-type doping in graphene through surface electron transfer, but these doping effects are unstable. By introducing nitrogen-containing precursors in growth approach, small part of lattice carbon atoms will be replaced by nitrogen atoms which can result in effectively n-doping effect. Combine the p-type and n-type doping method together, the p-n junction can be produced in mono- or bi-layer graphene, a series of novel functional devices like photothermoelectric devices have been constructed using these hetero-doped graphene p-n junctions.

[Zhang Yunqiu; Liang Yongming; Zhou Jianxin] Nanjing Univ Aeronaut & Astronaut, State Key Lab Mech & Control Mech Struct, Coll Aerosp Engn NUAA, Nanjing 210016, Jiangsu, Peoples R China.

石墨烯的p型和n型掺杂调控对于石墨烯基功能器件的构筑至关重要. 近年来，随着化学气相沉积（CVD）石墨烯技术的发展和广泛应用，CVD石墨烯掺杂技术及相应性能调控的研究也取得了极大进展. 本文主要介绍了近几年来石墨烯，特别是CVD生长石墨烯掺杂研究的发展，讨论了金属电极接触、气体小分子吸附、氧化性及还原性极性分子吸附及晶格掺杂等多种石墨烯掺杂的方法，同时介绍了近期出现的对双层石墨烯能带调控以及制造石墨烯p-n结的研究，展望了石墨烯掺杂对于其功能器件研究的作用和发展前景.

... 引言石墨是理想的无机非金属材料, 具有高化学稳定性、良好的导电性、较好的耐磨性等优点, 被广泛应用于现代化学工业及其他诸多领域^[1,2,3] ...

2011

0.0

YUAN

Xiao-ya

(袁小亚). Journal of Inorganic Materials(无机材料学报), 2011, 26: 561.

Graphene has attracted much interest in recent years due to its unique and outstanding properties. Different routes to prepare graphene have been developed and achieved. Preparation methods of graphene used in recent years are intensively introduced, including micromechanical cleavage, chemical vapor deposition, liquid/gas- phase-based exfoliation of graphite, epitaxial growth on an insulator, chemical reduction of exfoliated graphene oxide, etc. And their advantages and shortcomings are further discussed in detail. The preparations of graphene are also prospected.

(College of Science, Chongqing Jiaotong University, Chongqing 400074, China)

近年来, 石墨烯以其独特的结构和优异的性能, 在化学、物理和材料学界引起了广泛的研究兴趣. 人们已经在石墨烯的制备方面取得了积极的进展, 为石墨烯的基础研究和应用开发提供了原料保障. 本文大量引用近三年最新参考文献, 综述了石墨烯的制备方法: 物理方法(微机械剥离法、液相或气相直接剥离法)与化学法(化学气相沉积法、晶体外延生长法、氧化?还原法), 并详细介绍了石墨烯的各种修饰方法. 分析比较了各种方法的优缺点, 指出了石墨烯制备方法的发展趋势.

... 引言石墨是理想的无机非金属材料, 具有高化学稳定性、良好的导电性、较好的耐磨性等优点, 被广泛应用于现代化学工业及其他诸多领域^[1,2,3] ...

2010

0.0

... 常用的火法-电感耦合等离子质谱(ICP)方法检测石墨^[4]存在的问题是: (1)在高温灼烧期间个别元素容易损失 ...

2015

0.0

... 因此现在有很多学者开始研究利用固体进样方法来测定石墨中杂质元素含量^[5,6,7] ...

2017

0.0

... 因此现在有很多学者开始研究利用固体进样方法来测定石墨中杂质元素含量^[5,6,7] ...

2017

0.0

... 因此现在有很多学者开始研究利用固体进样方法来测定石墨中杂质元素含量^[5,6,7] ...

2015

0.0

... 辉光放电质谱法(glow discharge mass, GDMS)是将辉光放电源(glow discharge, GD)与质谱分析方法(MS)联用的一种分析技术, 具有前处理简单、检出限低、灵敏度高等优点, 在测定高纯金属中杂质元素含量方面具有显著的优势^{[8,9,10,11,12]}, 该方法在国内外已被用作部分高纯金属和半导体材料的标准分析方法, 但对石墨材料中杂质元素的检测尚未见报道 ...

2013

0.0

2014

0.0

2014

0.0

Fang-fei

, WANG

Chang-hua

, LI

Ji-dong

(胡芳菲, 王长华, 李继东). Journal of Chinese Mass Spectrometry Society(质谱学报), 2014, 35(4): 335.

In order to investigate elemental analysis in non-conducting samples by direct current glow discharge mass spectrometry (dc-GDMS), a method for detecting impurities in α -Al 2 O 3 powder was established. Copper powder acted as a kind of conducting host matrix, which was fully mixed with α -Al 2 O 3 powder，and then pressed the mixture into wafers. Effect of glow discharge conditions, such as discharge current, discharge gas flow, ion source temperature, and pressure conditions, such as mixture ratio, pressure, etc. on discharge stability and sensitivity were investigated. The experiment condition was optimized. Total signal of Al, O and Cu normalization was adopted, and the impurities contents in α -Al 2 O 3 powder were calculated in subtraction. The method precision is within 54% and the detection limits are between 0.005 μg/g and 0.57 μg/g. The results coincide with that of direct current spark atomic emission spectrometry.

General Research Institute of Non-ferrous Metals, Beijing 100088, China

为了探索采用直流辉光放电质谱法(dc-GDMS)测定非导体样品中的杂质含量，建立了dc-GDMS法测定 α -Al 2 O 3 粉末中杂质元素的方法。以Cu粉作为导电介质，与 α -Al 2 O 3 粉末混合均匀，压片，考察辉光放电条件（放电电流、放电气体流量、离子源温度）和压片条件（两种粉末的混合比例、压片机压力等因素）对放电稳定性和灵敏度的影响，同时优化了实验条件。尝试将Al、O、Cu的总信号归一化进行计算，并用差减法计算了Al 2 O 3 粉末中的杂质含量。方法精密度在54%以内，元素检出限为0.005~0.57 μg/g。该方法的测定结果与直流电弧发射光谱法的测定结果基本吻合。

2018

0.0

2012

0.0

LIU

Jie

, QIAN

Rong

, ZHUO

Shang-jun

(刘洁, 钱荣, 卓尚军). Chinese Journal of Analytical Chemistry(分析化学), 2012, 40(1): 66.

This paper mainly describes the determination of relative sensitivity factors (RSF) of the key impurities in poly-silicon by direct current glow discharge mass spectrometry (dc-GD-MS). Appropriate content of non-standard poly-silicon samples was molten in furnace under argon atmosphere and cast to ingot. Prior to casting B and P key impurities were added to the silicon melt in the range of 1 - 30 mu g/g. Then a series of standard samples were made for the flat cell analysis (20 mm x 20 mm x 2 mm). The accurate concentrations of the key impurity in these standard samples were determined by secondary ion mass spectrometry(SI-MS) analysis. The key impurities of standard samples were also detected by GD-MS to get the ion intensity and the uncorrected concentration under optimized conditions. The relative sensitivity factors(RSF) of key impurities were calculated by the experimental formula and standard curve method.

[Liu Jie; Qian Rong; Zhuo Shang-Jun] Chinese Acad Sci, Shanghai Inst Ceram, Shanghai Mass Spectrometry Ctr, Shanghai 200050, Peoples R China.;[Siqin Bilige] Chinese Acad Sci, Shanghai Inst Opt & Fine Mech, Shanghai 201800, Peoples R China.;[Liu Jie; He Pin-Gang] E China Normal Univ, Dept Chem, Shanghai 200062, Peoples R China.

... RSF是一个用于校正GDMS分析结果的系数, 对于GDMS分析而言, 大部分元素在不同基体中仍然存在较明显的基体效应^{[13,14,15,16,17]} ...

2012

0.0

TANG

Yi-chuan

, ZHOU

Tao

, XU

Chang-kun

(唐一川, 周涛, 徐常昆). Journal of Instrumental Analysis(分析测试学报), 2012, (6): 664.

As a powerful tool for the analysis of high pure metal and semiconductor，glow discharge mass spectrometry(GDMS) has been extended applied in China.The primary theory and application of GDMS were simply introduced and the instrumental conditions，measurement repeatability and series certified reference materials with different metallic matrix were researched in detail.The measured repeatabilities of analysis results were in the range of 1%-5% for the impurities which the contents were about 1 mg/kg. The series of certified reference materials of steel，copper，including SRM1761a,SRM1762a，SRM1763a，SRM1764a，SRM1765，SRM1766，SRM1767，SRM1767，SRM1112-SRMC1117 and SRM1256b purchased from National Institute of Standards and technology(NIST) of USA，were investigated and the results were compared.It was found that the same correction factors could be used in the measurement of impurities with similar matrix in a wide range of contents under the same measurement conditions.The correlation coefficients of series results were more than 0.999.It was found that there were obvious matrix effects in the measurements of samples with different matrixes.The routine instrumental values of some relative sensitivity factors(RSFs)，especially for the elements of lighter mass number，were not suitable for the quantitative analysis,but it is enough for the semi-quantitative analysis because the differences were no more than double of the RSFs.The result indicated that the correction of RSFs was the key technique for the measurement traceability through the research of the quantitative analysis by GDMS spectrometry.

辉光放电质谱(GDMS)作为高纯金属和半导体材料分析的强有力工具在国内已得到了大量应用，该文简要介绍了GDMS的基本原理和国内外应用现状，对仪器测量条件的选择、测量重复性进行了详细研究，对于含量在1 mg/kg左右的杂质，测量的重复性将产生约1%~5%的不确定度；对不同金属基体的系列标准物质进行对比研究，发现对于基体相同的样品，杂质元素在较宽的浓度范围内可以使用同样的校正系数进行校正，大部分元素的线性相关系数达到0.999以上，但对于不同基体的样品，测量中仍存在明显的基体效应，一些元素，尤其是轻质量数元素的相对灵敏度因子(RSF)设定值存在较大的偏差，并不适合定量分析，但绝大部分不超过2倍误差，可以满足半定量分析的要求。通过对GDMS定量分析中关键因素的研究，认为相对灵敏度因子的校正是GDMS测量结果可溯源性的关键。

... RSF是一个用于校正GDMS分析结果的系数, 对于GDMS分析而言, 大部分元素在不同基体中仍然存在较明显的基体效应^{[13,14,15,16,17]} ...

2016

0.0

WEI

Xing-lian

, WANG

Li-ping

, QIN

Zhen

(魏兴俭, 王丽萍, 秦震). Journal of Chinese Mass Spectrometry Socieuy(质谱学报), 2016, (4): 343.

Three impact basics of the relative sensitivity factors (RSF) and the ion intensity of glow discharge mass spectrometry (GDMS), including discharge current, voltage and gas flow rate, were investigated. The results showed that under constant discharge current or voltage conditions, the RSF of heavy elements increases while the gas flow rate increases, and the RSF of light elements decreases slightly or stabilizes. Under constant discharge current conditions, the ion intensity increases while the gas flow rate is from 300 mL/min to 400 mL/min, and the ion intensity decreases while the gas flow rate is from 400 mL/min to 500 mL/min. Under constant discharge voltage conditions, the ion intensity increases while the gas flow rate is from 300 mL/min to 500 mL/min. Under constant gas flow rate conditions, the RSF of most elements is stabilized while the discharge current and voltage are changed, and the ion intensity increases while the discharge current and voltage increase. This means that the gas flow rate is the most important impact basic. The RSF of some elements was determined using the CRM of Fe, Co, Ti, Ni, Zn, Sn and Pb under the gas flow rate of 400 mL/min. It was found that the RSF difference of the same element at different matrixes is tiny, and matrix effect isn’t distinct. This helps to achieve accurate measurement using non matrix-matched RSF while the matrix-matched standards are lacking. The mean RSF at different matrixes was calculated to calibrate the measured values of a few elements of two Cu-Zn alloys. The relative difference of the corrected values and the standard values is under 30%.

Institute of Materials, China Academy of Engineering Physics, Mianyang 621900, China

本工作研究了辉光放电气体流速、放电电压和放电电流3个主要因素对辉光放电质谱法（GDMS）相对灵敏度因子（RSF）的影响。结果显示，在恒定的放电电流或放电电压下，重元素的RSF随放电气体流速的增大而增大，轻元素的RSF随放电气体流速的增加略微减小或不变；在恒定的放电气体流速下，多数元素的RSF基本不随放电电流和放电电压改变。在400 mL/min放电气体流速下，分别测定了Fe、Co、Ti、Ni、Zn、Sn、Pb 7种不同基体标准物质部分元素的RSF，结果显示，同一元素在不同基体条件下RSF的差异较小，基体效应不明显。将进一步得到的不同基体下的平均RSF应用于2种铜锌合金标准物质元素组分的测定，其主要元素的测定值与标准值的相对百分差均不超过30%。

... RSF是一个用于校正GDMS分析结果的系数, 对于GDMS分析而言, 大部分元素在不同基体中仍然存在较明显的基体效应^{[13,14,15,16,17]} ...

2016

0.0

... RSF是一个用于校正GDMS分析结果的系数, 对于GDMS分析而言, 大部分元素在不同基体中仍然存在较明显的基体效应^{[13,14,15,16,17]} ...

2011

0.0

... RSF是一个用于校正GDMS分析结果的系数, 对于GDMS分析而言, 大部分元素在不同基体中仍然存在较明显的基体效应^{[13,14,15,16,17]} ...