【摘要】：激光誘導(dǎo)擊穿光譜(Laser-Induced Breakdown Spectroscopy, LIBS)作為一種原子輻射光譜技術(shù),與傳統(tǒng)的化學(xué)分析技術(shù)相比,具有遠(yuǎn)程、非接觸、可原位、可實(shí)時(shí)、可全元素同時(shí)測量的巨大優(yōu)勢；與一般光譜分析技術(shù)相比,又具有快速、可便攜、樣品制備簡單或者無需制備、適用固體液體氣體的優(yōu)點(diǎn)。這些優(yōu)勢和優(yōu)點(diǎn)決定了LIBS技術(shù)在諸多領(lǐng)域極具應(yīng)用潛力。但是,由于激光與物質(zhì)相互作用的非線性過程極為復(fù)雜,這直接導(dǎo)致了LIBS在定量分析上遇到很大的困難,嚴(yán)重地限制了它的實(shí)際應(yīng)用。因此,定量分析應(yīng)用的研究和分析性能的改善是當(dāng)前LIBS研究領(lǐng)域的聚焦熱點(diǎn)。實(shí)際應(yīng)用中分析物質(zhì)和測量條件多樣復(fù)雜,一方面不同樣品產(chǎn)生的信號(hào)差異明顯,所謂的基體效應(yīng)影響了定標(biāo)定量分析的精確度,另一方面激光與物質(zhì)的耦合效率等因素也限制了LIBS技術(shù)的分析靈敏度。本論文針對(duì)生活環(huán)境中經(jīng)常檢測的分析對(duì)象包括油液、水溶液、土壤,開展了LIBS的定量分析研究,有效地提高了LIBS應(yīng)用的定量分析性能,深入的研究可以促進(jìn)LIBS發(fā)揮更大的應(yīng)用潛力。本論文首先設(shè)計(jì)搭建了穩(wěn)定的籠式結(jié)構(gòu)的LIBS實(shí)驗(yàn)系統(tǒng),實(shí)現(xiàn)了樣品表面掃描精確控制、光譜采集和數(shù)據(jù)分析以及LIBS信號(hào)的測量優(yōu)化。然后在實(shí)驗(yàn)系統(tǒng)搭建的基礎(chǔ)上,開展了油液、水溶液和土壤的定量分析方法研究。本論文將金屬表面增強(qiáng)的機(jī)制應(yīng)用于油液的金屬元素定量分析。將少量油液在金屬表面形成薄膜,脈沖激光聚焦于金屬表面擊穿燒蝕產(chǎn)生高溫金屬等離子體,從而間接擊穿了表層的薄油膜,提高了油膜的元素分析靈敏度。通過對(duì)油液中所含九種金屬元素(Mg、Cu、Ag、Ti、Si、Sn、Cr、Fe、Ni)的定標(biāo)曲線以及定量分析,得到金屬元素分析的探測極限為亞ppm或者ppm。進(jìn)一步對(duì)10種不同機(jī)油或蔬菜油的分析比較,發(fā)現(xiàn)不同油液的基體效應(yīng)在金屬表面增強(qiáng)方法中基本可忽略。本論文應(yīng)用該方法測量了廢機(jī)油中的磨損金屬元素。本論文開展了水溶液的金屬表面增強(qiáng)LIBS方法研究。將少量的含氯礦物質(zhì)粉末的水溶液沉積在光滑的金屬表面形成沉積薄層,同時(shí)也將粉末壓片,通過對(duì)兩種制樣方法的LIBS分析測量比較,研究了基體效應(yīng)在兩種方法中表現(xiàn)的差異。通過對(duì)金屬表面增強(qiáng)方法產(chǎn)生的等離子體演化特性診斷,表明金屬表面增強(qiáng)LIBS方法中,其產(chǎn)生的等離子體特性主要取決于金屬基底,因而大大減小了分析物質(zhì)所帶來的基體效應(yīng)。本論文提出了激光預(yù)處理金屬表面的方法,有效克服了水溶液在光滑基底表面擴(kuò)散慢、沉積分布不均勻的問題。由于規(guī)則微結(jié)構(gòu)的存在,水溶液在激光預(yù)處理的有限表面區(qū)域均勻擴(kuò)散,與光滑金屬表面相比,大大提高了測量的重復(fù)精度,張力的變化使得水溶液在該區(qū)域擴(kuò)散十分迅速,且很好地被約束在區(qū)域內(nèi),使得水溶液多次沉積富集成為可能。最后實(shí)現(xiàn)了水溶液的重金屬測量探測極限達(dá)到亞μg/L (Cd、Ni為例)或μg/L(以Cd為例),比常規(guī)LIBS方法提高了三個(gè)數(shù)量級(jí),比文獻(xiàn)報(bào)道的最優(yōu)的LIBS測量方法也有約兩個(gè)數(shù)量級(jí)的提高。本論文提出了溴化鉀凝結(jié)壓片的土壤LIBS定量分析方法。土壤是異質(zhì)物質(zhì)的代表,基體效應(yīng)嚴(yán)重影響LIBS定量分析應(yīng)用。本論文使用了溴化鉀作為凝結(jié)物質(zhì)進(jìn)行土壤粉末壓片,通過改變溴化鉀含量以及燒蝕坑的分析,發(fā)現(xiàn)澳化鉀的添加明顯提高了土壤與激光的耦合效率,且由于高含量溴化鉀的添加,基體效應(yīng)明顯下降,最后得到了不同類型土壤定量分析的共同定標(biāo)曲線,預(yù)測誤差小于20%。本論文主要?jiǎng)?chuàng)新之處：1)利用金屬表面增強(qiáng)的LIBS液體分析方法,提高了激光與液體的耦合效率,增強(qiáng)了分析物質(zhì)測量的靈敏度,分析發(fā)現(xiàn)了在混合等離子體中起決定性作用的金屬基底使得分析物質(zhì)帶來的基體效應(yīng)可以忽略。2)提出激光預(yù)處理金屬表面和金屬表面增強(qiáng)相結(jié)合的方法,使LIBS分析水溶液的靈敏度提高了2-3個(gè)數(shù)量級(jí),明顯改善了測量重復(fù)精度。3)利用溴化鉀凝結(jié)土壤進(jìn)行壓片的LIBS定量分析方法,有效提高了激光消融土壤物質(zhì)的效率,明顯改善了土壤砂巖物質(zhì)的基體效應(yīng)。
[Abstract]:Laser-Induced Breakdown Spectroscopy (LIBS) is a kind of atomic radiation spectroscopy technology. Compared with traditional chemical analysis technology, LIBS has the advantages of remote, non-contact, in-situ, real-time and simultaneous measurement of all elements. Compared with general spectrum analysis technology, LIBS is fast, portable and sample preparation. These advantages determine that LIBS technology has great potential in many fields. However, due to the extremely complex nonlinear process of laser-matter interaction, LIBS has encountered great difficulties in quantitative analysis, which severely limits its practical application. Therefore, the application of quantitative analysis and the improvement of analytical performance are the focus of the current LIBS research field. In practical application, the analytical materials and measurement conditions are various and complex. On the one hand, the signals produced by different samples are obviously different. The so-called matrix effect affects the accuracy of the calibration and quantitative analysis, on the other hand, laser and material. The coupling efficiency and other factors restrict the sensitivity of LIBS. In this paper, the quantitative analysis of LIBS is carried out for the analysis objects in living environment, including oil, water and soil. The quantitative analysis performance of LIBS is effectively improved. The further study can promote the application potential of LIBS. Firstly, a stable cage-type LIBS experimental system is designed and constructed to realize the precise control of sample surface scanning, spectrum acquisition and data analysis, and the optimization of LIBS signal measurement. Then on the basis of the experimental system, the quantitative analysis methods of oil, water and soil are studied. The mechanism is applied to the quantitative analysis of metal elements in oil. A small amount of oil is formed on the surface of the metal, and pulsed laser is focused on the surface of the metal to break down and ablate to produce high-temperature metal plasma, which indirectly breaks through the thin oil film on the surface and improves the sensitivity of element analysis of the oil film. The calibration curves and quantitative analysis of Ti, Si, Sn, Cr, Fe, Ni show that the detection limit of metal element analysis is sub-ppm or ppm. Further analysis and comparison of 10 different oil or vegetable oil shows that the matrix effect of different oil can be neglected basically in the metal surface strengthening method. This paper uses this method to measure the abrasion in waste engine oil. Metal elements are destroyed. In this paper, the metal surface-enhanced LIBS method of aqueous solution is studied. A small amount of chlorine-containing mineral powder is deposited on the smooth metal surface to form a thin layer of deposition. At the same time, the powder is pressed into sheets. By diagnosing the plasma evolution characteristics produced by metal surface enhancement method, it is shown that the plasma characteristics produced by metal surface enhancement LIBS method mainly depend on the metal substrate, thus greatly reducing the matrix effect caused by the analytical material. It overcomes the problem of slow diffusion and uneven distribution of aqueous solution on smooth substrate surface.Due to the existence of regular microstructure,aqueous solution diffuses uniformly in the limited surface area of laser pretreatment.Compared with smooth metal surface,the repetition precision of measurement is greatly improved.The change of tension makes the diffusion of aqueous solution very fast in this area. Finally, the detection limit of heavy metals in aqueous solution reaches sub-g/L (Cd, Ni for example) or micro-g/L (Cd for example), which is three orders of magnitude higher than the conventional LIBS method and about two orders of magnitude higher than the optimal LIBS method reported in the literature. In this paper, a quantitative analysis method of soil LIBS for potassium bromide condensation tablets is proposed. Soil is the representative of heterogeneous materials, and matrix effect seriously affects the application of LIBS quantitative analysis. The coupling efficiency between soil and laser is improved obviously, and the matrix effect is decreased obviously due to the addition of high content of potassium bromide. Finally, the common calibration curve of different types of soil quantitative analysis is obtained, and the prediction error is less than 20%. The main innovations of this paper are as follows: 1) The LIBS liquid analysis method enhanced by metal surface is used to improve the laser intensity. The coupling efficiency with the liquid enhances the sensitivity of the analytical material measurement. It is found that the metal substrate plays a decisive role in the mixed plasma makes the matrix effect of the analytical material negligible. The LIBS quantitative analysis method using potassium bromide condensate soil for compaction can effectively improve the efficiency of laser ablation of soil material and improve the matrix effect of soil sandstone material.
【學(xué)位授予單位】：華東師范大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：TN249;O433.4

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本文編號(hào)：2207123