The Study Of One-dimensional,Two-dimensional And Three-dimensional Elemental Distribution In Solids Using High Irradiance Laser Ionization Time-of-flight Mass Spectrometry

With the rapid development of material science,the traditional solution-based analytical strategy is difficult to satisfy the requirement of modern science,which is attributed to its shortcomings,such as tedious pretreatment for sample,ease to be contaminated,limited capability to get rough composition information etc.Considering these,developing a method with the capacity to directly analyze the solids is receiving increasing interest in analytical chemistry.An in-house-built buffer-gas assisted high irradiance laser ionization time-of-flight mass spectrometry(LI-TOFMS)has been proved to be an excellent technique for direct solids analysis.Its application fields include conductive sample,semi-conductive and nonconductive one.And it is able to rapidly determine almost all elements simultaneously,including non-metal elements.Moreover,it is capable of performing semi-quantitative analysis without the requirement of calibration by standards,which is vital within the direct solids analysis due to the rarity of matrix matched solid standards.In this dissertation,the study of the composition spatial distribution on the actual solids,which includes one-dimensional,two-dimensional and three-dimensional elemental distribution analysis were performed using LI-TOFMS.The brief introduction of these three sections were demonstrated as follows:1.One-dimensional elemental distribution analysisThis sectional study demonstrates that the homogeneous crater and uniform ablation is vital for the depth profiling of coating,which can be achieved by a beam expander and an aperture.Firstly,the depth profile of single layer and multilayer samples was carried out by nanosecond laser ionization time-of-flight mass spectrometry(ns-LI-TOFMS).But both of the average ablation rate(AAR(Zn)=1.3 μm/pulse)and the depth resolution(AZ(Zn)= 2.4μm)were in the range of micrometer.In order to further improve the ability of the technique in the depth profiling,a femtosecond laser was introduced to compare with the nanosecond laser.The compared results indicate both the average ablation rate(AAR(Pd)= 55 nm/pulse)and depth resolution(AZ(Pd)= 310 nm)by fs-LI-TOFMS were one order of magnitude better than ns-LI-TOFMS.Moreover,not only the conductive coating but also the nonconductive one can be analyzed.2.Two-dimensional elemental distribution analysisThis sectional study demonstrates the capacity of two-dimensional imaging basing on buffer-gas assisted high irradiance femtosecond laser ionization time-of-flight mass spectrometry(fs-LI-TOFMS).The 2D mapping on the cross-section of the ancient celadon,present by elemental distribution in glaze-transition-porcelain body,was carried out to explore the formation mechanism of the transition layer between porcelain body and glaze.Additionally,the composition characteristics of the porcelain body as well as glaze from Yue kiln in different cultural eras(Tang Dynasty,Five Dynasties,Song Dynasty and contemporary era)were revealed.29 elements in the porcelain body and 25 elements in the glaze were detected.The elements Fe and Ti of porcelain body and Ca,P,Mn and Mg of glaze were considered as characteristic elements to classify the porcelain among different cultural eras,even for the discrimination of the counterfeits from contemporary era.Moreover,elemental composition of celadon body and glaze from the Yue kiln and Yaozhou kiln were compared for further exploring the raw material and firing technologies of porcelain between Southern and Northern kiln.3.Three-dimensional elemental distribution analysisThis sectional study combines the two previous works,depth profiling and 2D imaging,and develops the ability of three-dimensional imaging using fs-LI-TOFMS.A self-prepared disc mixing four high purity metal powders of Cr,Fe,Ni and Cu,was first introduced to validate the feasibility of the 3D imaging by this technique with a lateral resolution of 50 Jim and a depth resolution of 7 pin.Then,3D imaging was performed on the Nantan meteorite with a detection limit of 1O-6 g/g and a dynamic range of 6 orders of magnitude.And the spatial distributed characteristics of three type elements including siderophile(Iron-loving)elements(Co and Ni),chalcophile(S-loving)elements(Cu,Cr,V and Mn)and lithophile elements(Li,Na,Mg,Al,K,Ca,Ti)reveal that siderophile elements are mainly enriched in the metal phase,chalcophile elements in sulfide and lithophile elements,in the form of silicate inclusion,embedded within the metal phase.S,P and C aggregate together in the imaging volume.These 3D distributions of elements aid the exploration of the formation as well as evolution of the meteorite.