Quantitative Research Of Pore Structure Of The Filtering Material By Electron Microscopy Image Analysis

Bubble-point method, mercury porosimetry and small angle X-Ray scatteringare relatively common characterization methods of filtering material, which areindirect determinations of aperture, distribution of aperture or porosity, theopen-close and size of the pores have great influence on the precision ofmeasurement. Electron microscopy observation is generally used as qualitativeobservation. The filtering materials were divided into three kinds of material, i.e.particle leaching filtering material, particle stacking filtering material and fiberinterweaving filtering material according to its production process and structuremorphology. A new analysis method which characterizes by electron microscopeimage analysis was established. Ten kinds of parameters, i.e. aperture, effectiveaperture, wall thickness, pore area, pore perimeter, porosity, pore density,roundness, elongation and concave were defined to be the parameter. Theprocedures of image processing and measurement were combined into a macroprogram, by which we can process and measure these images semi-automatically.Comprehensive quantitative characterization of the pore structure got through thequantitative electron microscopy research on the filtering material.The characterization method was established based on the characteristic ofparticle leaching filtering material, five kinds of characterization methods, i.e.aperture, wall thickness, pore perimeter, porosity, pore density, roundness werechosen. The aperture results of WT membrane, AJL membrane, XY-1membraneand XY-2membrane were0.38μm,0.5μm,0.27μm and0.55μm, the wall thicknessresults of them were1.0μm,2.0μm,0.98μm and1.4μm, the roundness results ofthem were0.13,0.09,0.12and0.11. The relative standard deviations of theaperture、wall thickness and roundness were2.3%,5.7%and3.5%, respectively.Results of the parameters demonstrated that the aperture was small, distribution ofaperture was narrow and followed normal distribution.The using of image inpainting during the image processing was due to thecomplicated pore structure of particle stacking filtering material. The qualitativeobservation and quantitative study revealed that aperture, wall thickness, pore perimeter, porosity, pore density and concave were better suited to thecharacterization of this kind of material. The aperture results of BL filter, JD-1filter core, JD-2filter core and DQ filter core were14μm,3.5μm,3.1μm and5.8μm, the concave results of them were0.13,0.09,0.12and0.11, respectively.The relative standard deviations of the aperture and concave were5.5%and5.9%,respectively. The results showed that the aperture was large; the distribution ofaperture was wide and closed to normal distribution.Since the layer structure of the fiber interweaving filtering material wasunclear even after the optimization of depth, median filtering was essential to betaken into the image processing study. Based on the characteristic of porestructure of fiber interweaving filtering material, aperture, wall thickness, poreperimeter, porosity, pore density and roundness were chose to be thecharacterization parameters. The aperture results of PL membrane, WT membrane,XY-1membrane and XY-2membrane were0.40μm,64μm,0.77μm and0.64μm,the wall thickness results of them were0.40μm,64μm,0.77μm and0.64μm, theroundness results of them were0.86,0.82,0.86and0.8, respectively. The resultsof the parameters revealed that the number of the pore was large and the aperturewas small, the pore shape was complicated.Nanoporous gold prepared by dealloying are promised to be advancedultrafiltration material. A new way to regulate the pore structure was found basedon the quantitative characterization of the pore structure by electron microscopeimage analysis. Nanoporous gold was immersed in NaCl, NaBr and NaI solutions,respectively. Aperture increased from11.3nm to25.4nm,13.7nm and50.1nm,respectively; Wall thickness increased from24.8nm to29.8nm,25.1nm and54.0nm, respectively; Roundness reduced from0.6to0.55,0.59and0.51,respectively. Changes of pore structure of nanoporous gold are possibly based onnanometer size effect, which induced the dissolution of Ag and the diffusion andself-assembly of Au, and the changes of pore structure.