Research Of Rapid Elemental Analysis Of Various Forms Of Materials By Laser-induced Breakdown Spectroscopy

Many industries need to use analytical instruments to detect various materials,and the forms of the materials are mostly complex.It is often necessary to meet the requirements of the detection of comprehensive forms of solid,liquid and powder materials.Taking oil and gas exploration field as an example,it is necessary to analyze various forms of materials at the drilling site,such as debris,drilling wastewater and slurry drilling fluid.Traditional analytical methods have to use a variety of analytical techniques to analyze the various forms of the samples,which means the detection of the specific form of the samples have to use the matched specific analytical instruments.Therefore,realizing the on-site rapid analysis of various forms of materials is of great importance to the depth development of many industries.Laser-induced breakdown spectroscopy(LIBS)is a frontier analytical technology in spectrum analysis field for its unique advantages such as rapid multi-element analysis,few or even no sample pre-treatment procedures,in situ analysis capability,on-site analysis,non-touch detection and no strict limit on the form of the sample.The advantages of LIBS rendered it particularly suitable for rapid analysis of various forms of materials in many applications.However,at present,LIBS has many limitations in detection of solid materials,liquid materials and powder materials due to the influences of the properties of materials,the reference samples and the detection technology,and there is no instrument which is capable of rapid detection of various forms of materials.Therefore,LIBS is limited in rapid and field analysis,which restricts the development of LIBS technology in many applications.Because of these,the main research contents of this paper are as follows:(1)In accordance with application requirements of rapid elemental analysis of liquid materials,and the limitations such as the poor sensitivity and stability,complex pre-treatment procedures(e.g.conversion of liquids to solids using special substrates and pre-concentration,etc.),complex operation,time-consuming detection and expensive system.In the present work,the rapid elemental analysis of semi-colloidal suspension and colloidal solution,non-trace elements and trace elements of true solution were studied.A sample heating method combined with superabsorbent and PVA-supported ring-shaped phase conversion method was proposed to realize rapid liquid-to-solid conversion.Combined with signal enhancement with inert gas,the method efficiently improves the detection sensitivity and stability.Based on this method,a rapid elemental detection apparatus of liquid materials was developed.The elemental analysis of slurry drilling fluid and metal ions solutions were achieved using the apparatus.Compared to other liquid detection technique,the detection speed,sensitivity and stability of the apparatus were notably improved.(2)In accordance with application requirements of rapid elemental analysis of powder materials,and the limitations such as the poor accuracy and sensitivity,complex pre-treatment procedures(e.g.decomposition and tableting method,etc.),time-consuming detection,complex and expensive detection system.In the present work,the rapid elemental analysis of powder materials was studied.A sample heating method combined with liquid organic binder solidification method was proposed to realize rapid solidification of powder materials.The method efficiently improves the detection accuracy and sensitivity.Based on this method,a rapid elemental detection apparatus of powder materials was developed.The elemental analysis of certified reference materials copper ores and nickel ores were achieved using the apparatus.Compared to conventional tableting method,the surface characterization of laser ablated crater,signal stability,detection accuracy and sensitivity of the apparatus were notably improved.The results demonstrated that the apparatus has excellent performance of detecting powder materials.Futher more,the measurement uncertainty of the results were analysed and evaluated,further proved the feasibility of the apparatus,and it has definite guiding meaning in the improvement of the apparatus performance.(3)In accordance with application requirements of multi-elemental surface mapping of materials elemental compositions in many fields.In the present work,two-dimensional spatially-resolved scanning LIBS elemental analysis on the materials surface was studied.A micro/visual LIBS scanning mapping analytical system was developed to analyze the distribution of multi-elemental compositions on the surface of the materials by two-dimensional spatially-resolved scanning mapping technology.The LIBS two-dimensional spatially-resolved multi-elemental surface scanning mapping of pyrite quartz veins and stibnite mineralized sericitized kaolinized granite was studied using the apparatus.The emission lines for each concerned element were selected to indicate the corresponding elemental concentration with their intensities.The two-dimensional mappings of each element could reflect well the relative variation of elemental concentration over the surface profile,proved the feasibility of the analytical system.The LIBS two-dimensional spatially-resolved scanning mapping technology developed in this work can provide key elemental information for relevant researches in many applications.(4)In accordance with the limitation of the traditional LIBS quantitative analysis methods(e.g.calibration-based(CB)methods and chemometrics methods)which has to detect a large number of samples with known elemental compositions.In order to improve the speed of quantitative analysis and realize the determination of materials without reference samples,the elemental analysis of materials without reference samples was studied in this work.A portable LIBS instrument combined with a calibration-free(CF)method was developed.Cemented compact carbides without reference samples were analyzed without any calibration measurements.Qualitative and quantitative analysis of the samples were achieved using the portable LIBS instrument combined with the CF method.To validate the results obtained by CF method using the portable LIBS instrument,X-ray fluorescence spectrometry(XRF)was used to analyze the samples as well.The CF results agreed well with the XRF results.For the major element,the relative errors obtained were between-1.72% and-0.71%.For the other elements,the relative errors were acceptable as well.Compared with the CB methods and chemometrics methods,the technology developed in this work improved the speed of quantitative analysis and realize the determination of materials without reference samples,which makes it promising for practical field applications.(5)In accordance with application requirements of rapid detection of various forms of materials in many fields.Based on the above research of rapid elemental analysis of liquid materials,powder materials and solid materials,a multifunctional sampling chamber for LIBS rapid batch detection of various forms of materials was developed.Based on the application requirements of LIBS detection,the LIBS relevant technologies of the apparatus were studied.A multifunctional sampling chamber suitable for integrated instrument and experimental platform was developed respectively,realized the function matching in different detection conditions.On this basis,an automatic detection system of multifunctional sampling chamber was developed.It could realize rapid solidification of liquid and powder materials,and achieve two-dimensional spatially-resolved scanning LIBS elemental analysis on the solid materials surface.The apparatus efficiently improves the detecting efficiency,stability and sensitivity of liquid,powder and solid materials.It meet the applications requirements of the rapid detection of various forms of materials.Futher more,in order to further improve the detecting efficiency,operability and intuitivity of the multifunctional sampling chamber,several functional modules(e.g.laser autofocus module and automatic detection of visual selected measurement location module,etc.)of the apparatus were developed.