Application of polarized light microscopy on microstructural characterization of semisolid slurry

In this paper,two ways of micro structural characterization,optical microscopy(OM) and polarized light microscopy(PLM),were both employed to describe the micro structure of semisolid slurry prepared by swirling enthalpy equilibration device(SEED).The results show that PLM is more reliable and accurate than OM to describe the special morphology feature of semisolid slurry made by SEED process.Meanwhile,the effects of pouring temperature and mass of molten liquid on the primary α-Al particle size and morphology were also investigated using PLM.The quantitative metallographic results measured from PLM demonstrate that the grain size and morphology and their distribution are significantly affected by both pouring temperature and the mass of molten liquid.The grain size poured with 2.7 kg liquid decreases from 659 to186 μm,and grain morphology transforms from dendrite to globular structure with pouring temperature reducing from690 to 630℃.The decreasing pouring temperature also promotes the distribution of spherical structure on the cross section.Meanwhile,the mass of molten liquid decreasing from 2.7 to 2.3 kg can decrease the grain size by maximum of 44% at high pouring temperature.

Advancing respirable coal mine dust source apportionment:a preliminary laboratory exploration of optical microscopy as a novel monitoring tool

Exposure to respirable coal mine dust(RCMD)can cause chronic and debilitating lung diseases.Real-time monitoring capabilities are sought which can enable a better understanding of dust components and sources.In many underground mines,RCMD includes three primary components which can be loosely associated with three major dust sources:coal dust from the coal seam itself,silicates from the surrounding rock strata,and carbonates from the inert‘rock dust’products that are applied to mitigate explosion hazards.A monitor which can reliably partition RCMD between these three components could thus allow source apportionment.And tracking silicates,specifically,could be valuable since the most serious health risks are typically associated with this component-particularly if abundant in crystalline silica.Envisioning a monitoring concept based on field microscopy,and following up on prior research using polarized light,the aim of the current study was to build and test a model to classify respirable-sized particles as either coal,silicates,or carbonates.For model development,composite dust samples were generated in the laboratory by successively depositing dust from high-purity materials onto a sticky transparent substrate,and imaging after each deposition event such that the identity of each particle was known a priori.Model testing followed a similar approach,except that real geologic materials were used as the source for each dust component.Results showed that the model had an overall accuracy of 86.5%,indicating that a field-microscopy based moni-tor could support RCMD source apportionment and silicates tracking in some coal mines.

Quantification of polarization distribution from polarizing light microscopy images of ferroelectric single crystals

Qualification of polarization can be realized either on a macroscopic scale as an average property by P-E hysteresis measurements or on a nano/micro scale by piezoelectric force microscopy,transmission electron microscopy,scanning electron microscopy,and so on.However,visualization and qualification of polarization distribution in the micron to millimeter scale is still a challenge.Polarizing light microscopy(PLM)is often used in the study of ferroelectric domain structures mainly for domain patterns.A phe-nomenon called“chromatic polarization”has been observed in transparent ferroelectric crystals by using a crossed-PLM system viewed with white light,which contains rich information about local polariza-tion distribution.In this study,an automatic full-angle light intensity detection(AFALID)algorithm com-bined with colorimetry is developed to analyze the distribution of nonuniform local spontaneous polar-ization distribution in transparent ferroelectric single crystals.Temperature-dependent spontaneous po-larizations from the color analysis for PMN-0.36PT single crystals with single tetragonal domain state are in good coincidence with those extracted from temperature-dependent hysteresis loops and pyroelectric current measurements.We further apply this method to quantify the nonuniform domain distributions with nano-indentations.This non-contact and non-destructive characterization can provide fast and au-tomatic detection of polarization distributions in ferroelectric materials.

Preparation and Characterization of Mesophase Pitch via Co-Carbonization of Waste Polyethylene/Petroleum Pitch

The low-cost petroleum pitch and waste polyethylene （WPE） were used as raw materials to prepare the mesophase pitch by co-carbonization method and the forming mechanization of mesophase pitch was also investigated. Polarized microscopy, softening point, Fourier transform infrared spectroscopy （FTIR） and thermogravimetric analysis （TGA） were used to characterize and analyze the properties and struc- ture of the mesophase pitch. The results showed that the carbonization yield of the modified pitch was high when 1-2 wt% WPE was added and the property of mesophase pitch （MP1-450-4 and MP2-450-4） prepared by thermal polymerization was excellent. Moreover, when the treatment temperature was above 420 ~C, the mesophase development of the modified pitch may be entire and 100% streamline texture mesophase can form. During the co-carbonization of WPEJpetroleum pitch, a large number of naphthenic structures and methylene bridges may be generated, which can improve the properties of the obtained mesophase pitch.

Morphological and microscopic characterization of five commonly-used testacean traditional Chinese medicines

Testacean traditional Chinese medicine(TTCM), derived from the outer shell of sea or freshwater mollusks, is a special and important category of Chinese medicinal materials. To ensure the effective use of TTCM, a comparative identification study was performed on five commonly-used testacean drugs, including Haliotidis Concha, Arcae Concha, Meretricis Concha, Ostreae Concha and Margaritifera Concha(Shijueming, Walengzi, Geqiao, Muli and Zhenzhumu in Chinese, respectively).Typical morphological photographs of the crude drugs were acquired, and the key microscopic characteristics of the derived powders under normal light microscope and polarized light microscope were summarized. The major results can be concluded as follows:(1) the original species involved in the five TTCMs could be distinguished by their respective interspecies morphological characteristics;(2) the key identification characteristics of the five powdered crude drugs were mainly crystal fragments, with the fragment features under both normal light and polarized light microscope providing powerful points for differentiating the five commonly-used testacean drugs. This study demonstrated that it is feasible to provide authentication for these five kinds of TTCMs by the combination of morphology with microscopy.

胆石体外调节人体胆汁的胆固醇结晶途径

背景:胆固醇结晶是胆石形成的一个必要步骤。尽管一些模拟胆汁研究显示,胆石表面与周围水相对于结晶形成过程中的胆固醇分子存在竞争关系;但相关研究尚未在人体胆汁中开展。方法:收集13例行腹腔镜胆囊切除术患者的新鲜胆汁,其中10例为胆固醇结石,3例为胆色素结石。再从其他2例患者收集小的胆固醇结石。应用偏光显微镜观察原始胆汁和超滤胆汁(加入或不加入胆石)中胆固醇结晶的形态,包括螺旋状和针状无水胆固醇结晶,以及片状和块状胆固醇单水结晶。分别于胆石加入胆汁前和加入21天后,称量胆石的重量。结果:在原始胆汁中加入胆石后,无水胆固醇结晶有减少的趋势,但块状胆固醇单水结晶显著增多。在超滤胆汁中加入胆石后,螺旋状结晶和针状结晶的形成有受抑趋势,而片状和块状胆固醇单水结晶数量显著增多。胆汁孵育21天后,胆石重量显著减轻,无论是原始胆汁(-4.5%61.6%,P=0.046)还是超滤胆汁(-6.5%61.5%,P=0.002)。来自胆色素结石患者的胆汁,在未加入胆石前是清亮的;但加入胆固醇胆石后,所有样本均早期出现片状和块状胆固醇单水结晶。结论:无论是在原始胆汁还是超滤胆汁中,加入胆固醇结石均可对胆固醇结晶途径产生重大影响,胆固醇单水结晶的数量增加,而无水胆固醇结晶的形成受抑。固态胆固醇结晶从胆石表面分离或可解释这一现象。