消光起伏频谱法颗粒测量技术

消光起伏法也称为光脉动法，采用一束窄光束照射流动的颗粒群，接收透射光信号，测量区中颗粒浓度的起伏导致了透射光信号起伏，由此得到颗粒的粒径和浓度信息。最早用消光起伏法来对颗粒测量的是Grogery，他得到了颗粒的平均粒径和浓度。然而，该模型无法合理地解释宽分布颗粒的消光起伏信号，因此无法得到颗粒的粒径分布。     

激光散射法测量烟幕质量浓度的试验研究

为实现实时测量烟幕粒子数浓度、质量浓度和烟幕粒子的粒径分布,开发一种烟幕质量浓度测量装置,该装置采用激光前向散射原理和消光法测量原理相结合的方法。通过测试数据,可以计算出某一时刻的烟幕粒子数浓度和质量浓度的平均值。结果表明:烟幕质量浓度测量装置运行正常,粒径及粒径分布测量值准确。     

遗传算法用于颗粒粒度分布重建的研究

消光法是一种基于消光定律的非接触式颗粒浓度和颗粒粒度测量的有效方法。由于它原理简单、易操作、易实现，因而得到了广泛的应用与研究。粒度谱重建算法是消光法粒度谱测量的核心内容，为了克服以往粒度谱重建算法需要先验知识的局限性，提出了采用改进的遗传算法来重建颗粒的粒度分布函数，并给出了算法的实现步骤。从数值模拟和实验研究的结果来看，该算法具有较高的精度和稳定性，它不受颗粒粒度分布影响，对噪声不敏感，同时还可以用于未知光学常数颗粒的测量。     

基于主成分分析的消光法波长选择算法

在消光法颗粒粒径测量中,被测颗粒系的消光光谱包含有颗粒粒径、折射率等信息.在可见及可见-红外波段内,对单峰R-R分布的消光光谱,一阶微分以及二阶微分消光光谱进行主成分变换.通过分析比较,提出一种基于主成分分析的特征波长的选择算法.该算法首先对一阶微分消光光谱进行主成分变换,然后将每个波长下的一阶微分消光谱对主成分贡献率的大小作为特征波长选择的主要依据,同时将光谱范围的边界波长也作为特征波长,这样的波长选择方法保证了选出的光谱消光值具有较高的信息量.文中分别对单峰及双峰R-R分布的颗粒系采用独立模式反演算法进行仿真实验验证,仿真实验证实了所提方法的有效性和实用性.     

玻璃基底上二维有序Au纳米结构阵列消光特性的理论研究

采用离散偶极子近似方法(discrete dipoleapproximation,简称DDA)从理论上对玻璃基底上不同粒径的Au纳米粒子结构阵列的消光光谱以及消光峰与纳米粒子粒径的关系进行了研究。计算结果显示玻璃基底上的Au纳米粒子结构阵列的消光谱中出现明显区别于Au单体纳米粒子的共振峰,玻璃基底上的Au纳米粒子结构阵列的消光性质与单体纳米粒子的粒径密切相关,随着纳米粒径的增大表面等离子体共振吸收峰出现明显红移,并且在粒径>40nm时出现多峰吸收现象。计算结果与实验结果基本一致。给出玻璃基底上的Au纳米粒子结构阵列的共振吸收峰随单体纳米粒子粒径变化的关系图。对Au纳米结构阵列的吸收机制进行系统的理论分析。     

宽频超声衰减法测量河流泥沙粒径分布

为了研究宽频超声波通过河流泥沙悬浊液的声衰减谱中包含泥沙的颗粒粒度信息,采用超声耦合相模型和散射模型的叠加描述河流泥沙悬浊液中超声衰减行为,宽频超声换能器测量得到2～7.5MHz间泥沙悬浊液声衰减谱,结合独立模式的最优正则化反演算法,获得了相同体积浓度、不同粒径分布下和相同粒径分布、不同体积浓度下泥沙的颗粒粒径分布。结果表明,宽频超声衰减法能较好地区分3种不同粒径分布的泥沙,并且在体积浓为3.8%～8.5%范围间,测量得到的平均粒径受浓度变化影响较小。将超声法测量结果与显微镜图像法测量结果相比较,两种方法得到的粒径分布趋势较为一致,平均粒径较为吻合。     

光学式颗粒计数装置的研制

设计了一种检测装置,用来对洁净介质中的颗粒粒径大小和数量进行统计。详细分析了用几何光学的光阻公式替代消光公式对大粒径颗粒的检测机理和前向光散射探测器检测小粒径颗粒时的计数技术。用该装置对标准颗粒物质进行了检测实验,结果表明：对于2μm以上的颗粒计数。效率能达到90％;对于1μm以下的颗粒也有较好的分辨能力,计数效率在70％左右。数值计算和实验结果证实了该装置具有较好的计数能力,能够表征洁净介质的污染程度。     

显微图像法测量颗粒粒径的不确定度评定

采用显微图像法测量某球形玻璃微珠颗粒的平均粒径,从测试重复性、显微图像内标法粒径测量等方面对影响颗粒粒径测量结果的不确定度进行分析和阐述,并对各不确定度分量进行计算和合成,最终给出颗粒粒径测量的不确定度报告。结果表明,当采用扫描电镜内标法在放大倍率为200时,球形玻璃微珠颗粒的数量平均粒径的扩展不确定度为5.3%,有效自由度为96。     

消光法粒度测量中折射率反演问题研究

多波长消光法粒度测量中,在已知粒度分布前提下,采用遗传算法可以对折射率进行反演.相比于传统的优化方法,该算法获得的折射率结果逼近全局最优解.反演采用的波长数目和颗粒单分散性的优劣影响解的可靠性.     

采用比表面积和孔径分析仪测量纳米颗粒粒径

采用比表面积和孔径分析仪,利用颗粒堆积产生的孔隙大小与颗粒粒径之间存在的几何关系,通过测量纳米颗粒堆积产生的孔隙尺寸,实现了纳米颗粒粒径的测量。结果表明,对于粒径在30~70 nm的纳米颗粒,颗粒堆积产生的介孔尺寸与颗粒粒径之间存在良好的线性关系,通过工作曲线可快速获得粒径数值。尤其对于粒径小于100 nm的干燥颗粒,该方法具有良好的适用性,测量分辨率可达0.2 nm,测量结果具有统计意义。     

炭纤维乳液上浆剂

采用转相乳化法，选用不同的混合乳化剂对环氧树脂AG－80进行乳化。通过静置沉淀法，比较不同混合乳化剂对其乳化的影响，结果表明乳化效果最好的是乳化剂1601与NP－10的混合乳化剂。粒径分析结果显示乳液的最可几粒径为934．1nm时，乳液稳定性较好。上浆处理后，单纤维复合材料的界面剪切强度较未上浆时有所提高，说明用该上浆剂处理，不仅可达到保护炭纤维表面的目的，而且可以改善炭纤维与基体树脂间的界面粘结。     

转相乳化法制备乙烯基酯树脂炭纤维上浆剂

以乙烯基酯树脂与端环氧基反应型液态丁腈橡胶为主浆料,采用转相乳化法制备乳液型炭纤维上浆剂.探讨乳化剂种类、质量比、乳化温度、搅拌速率和溶剂对乳液性能的影响.结果表明:当乳化剂壬基酚聚氧乙烯醚磷酸铵与蓖麻油聚氧乙烯醚质量比为3∶1,乳化剂质量分数为主浆料的10%、乳化温度为50℃、搅拌速率为10000r/min、苯乙烯质...     

Pyrometric sizing of high-temperature particles in flow reactors

A pyrometric method was developed earlier for the simultaneous in situ measurement of the temperature and the size of combusting fuel particles in entrained flow reactors. The temperature measurement is based on two-color pyrometry and the particle sizing on the proportionality of the measured radiative flux and the cross-sectional area of a particle at a known temperature. This particle-sizing method needs a discrimination procedure to confirm that the detected particle is valid for particle sizing. We report on a novel method for particle discrimination based on coaxial reference optics. The new method has several advantages compared with the method presented earlier, including the measurement in turbulent flow fields.     

碳纤维水性杂化上浆剂的制备及其上浆后力学性能

以一定比例的甲基三乙氧基硅烷、正硅酸乙酯、对甲苯磺酸、γ-氨丙基三乙氧基硅烷、无水乙醇制备含硅溶胶,将含硅溶胶和聚醚型水性聚氨酯的水溶液以一定比例复合,制备碳纤维水性杂化上浆剂。研究了不同配比对上浆剂平均粒径和稳定性的影响,结果表明:当水性聚氨酯含量为0.02g/mL时,上浆剂乳液平均粒径为99.94nm,粒径分布较窄,稳定性较好;使用制备的杂化上浆剂对碳纤维进行上浆处理,结果显示:上浆后碳纤维单丝拉伸强度较商用碳纤维提高4.45%,较未上浆碳纤维提高11.04%;与环氧树脂复合后的复合材料界面剪切强度比商用碳纤维增强环氧树脂复合材料的提高了13.74%。     

Control of Particle Adsorption for Stability of Pickering Emulsions in Microfluidics

Studying the stability of Pickering emulsion is of great interest for applications including catalysis, oil recovery, and cosmetics. Conventional methods emphasize the overall behavior of bulk emulsions and neglect the influence of particle adsorbing dynamics, leading to discrepancies in predicting the shelf‐life of Pickering emulsion–based products. By employing a microfluidic method, the particle adsorption is controlled and the stability of the Pickering emulsions is consequently examined. This approach enables us to elucidate the relationship between the particle adsorption dynamics and the stability of Pickering emulsions on droplet‐level quantitatively. Using oil/water emulsions stabilized by polystyrene nanoparticles as an example, the diffusion‐limited particle adsorption is demonstrated and investigated the stability criteria with respect to particle size, particle concentration, surface chemistry, and ionic strength. This approach offers important insights for application involving Pickering emulsions and provides guidelines to formulate and quantify the Pickering emulsion–based products.     

纳米SiO2改性炭纤维乳液上浆剂的性能评价

采用纳米SiO₂改性环氧树脂乳液上浆剂和未改性乳液上浆剂对聚丙烯腈(PAN)基炭纤维进行表面上浆。通过静置沉淀法和光学显微镜评价了两种乳液的稳定性。利用扫描电子显微镜(SEM)、 X射线能谱仪(EDS)、 原子力显微镜(AFM)和动态接触角测试仪(DCAA)研究了未上浆、 未改性和改性上浆炭纤维的表面性能, 并用单纤维碎裂法探讨了上浆剂对炭纤维与环氧树脂界面黏结的影响。结果表明: 未改性和经纳米SiO₂改性的两种乳液粒径较小, 稳定性较好, 而前者优于后者。上浆后, 炭纤维表面的粗糙度和表面能都增大, 而且最大值出现在改性乳液上浆炭纤维的表面。改性乳液上浆单纤维复合材料拥有最大的界面剪切强度(IFSS), 比未改性上浆的高出27.2%; 改性上浆炭纤维与基体的调和平均黏结功(W(h)_a )和几何平均黏结功(W(g)_a )也分别高出未改性上浆的12.7%和11.7%。      

Particle sizing by quantitative acoustic emission

Two methods of particle sizing using an acoustic method are presented. The technique relies on the detection and measurement of elastic waves arising from impact of the particles with a small target plate. The acoustic impact signal, as measured from a high fidelity piezoelectric transducer, is characterised by the first wave arrival (compression wave) amplitude and risetime. A theoretical approach, based upon Hertzian impact theory and elastic wave propagation theory, is developed and used to determine the relationship between the impact dynamics of the particle and the acoustic signal. The first method of particle sizing relies upon amplitude measurements alone but requires accurate system calibration and full knowledge of the particle impact velocity, incident angle and coefficient of restitution. The velocity measurements were determined using a laser Doppler technique. The second approach for particle sizing incorporates risetime measurement and only depends very weakly upon the compression wave amplitude, thus minimizing the need for accurate absolute calibration. Knowledge of the impact velocity, incident angle, and coefficient of restitution were not required.Spherical particles of glass in the size range 35 to 140 µm diameter were dropped onto an aluminium target plate at an incident velocity of 8.1 m/s and angle to the surface normal of 0°, 40°, and 61°. The two acoustic methods were used to size the particles, and the results were compared to the particle size distributions obtained from video microscope measurements. The first sizing method undersized the smaller particles by 20% to 30% and oversized the larger ones by 5% to 10%. However, the second approach gave much smaller errors and consistently undersized all sizes of particle by just a few percent. This undersizing was understood in terms of some plasticity in the target that occurred during particle impact.     

聚乙二醇改性环氧乳液碳纤维上浆剂的研制

用聚乙二醇(PEG)在催化剂过硫酸钾作用下与环氧树脂反应, 制得自乳化环氧树脂乳液。通过红外光谱表征改性环氧的结构, 并比较不同实验方案下乳液的稳定性, 探讨了反应原料、合成工艺等因素对实验结果的影响, 确定了最佳实验方案; 用热分析实验表征上浆剂的热稳定性, 接触角测试表征上浆剂乳液的浸润性, 单丝碎裂实验测定界面剪切强度。结果表明, 使用双酚A环氧树脂及PEG1000在80~120 ℃反应制得的乳液稳定性最好, 上浆剂的热稳定性和浸润性良好。用实验制得的乳液对碳纤维上浆, 单丝界面剪切强度比上浆前提高33.48%, 碳纤维毛丝量减少。      

引发剂对阳离子苯丙乳液表面施胶剂粒径和性能的影响

以苯乙烯、甲基丙烯酸二甲胺乙酯、丙烯酸异辛酯为单体、改性PVA-0588为乳化剂,采用无皂乳液聚合的方式,合成了含功能性单体丙烯酸酯的阳离子共聚乳液。研究了不同的引发剂种类、不同的引发剂用量、不同的季铵化剂用量等因素对聚合物粒径的影响。研究发现,采用引发剂-还原剂体系,可获得平均粒径100 nm左右,粒径分布窄的阳离子苯丙乳液;作为纸张表面施胶剂,施胶效果得到明显提高,在同等条件下,比粒径宽分布的样品施胶效果提高7%左右。     

Laser-induced incandescence for soot particle size measurements in premixed flat flames

Measurements of soot properties by means of laser-induced incandescence (LII) and combined scattering-extinction were performed in well-characterized premixed ethylene-air flames. In particular, the possibility of using LII as a tool for quantitative particle sizing was investigated. Particle sizes were evaluated from the temporal decay of the LII signal combined with heat balance modeling of laser-heated particles, and these sizes were compared with the particle sizes deduced from scattering-extinction measurements based on isotropic sphere theory. The correspondence was good early in the soot-formation process but less good at later stages, possibly because aggregation to clusters began to occur. A critical analysis has been made of how uncertainties in different parameters, both experimental and in the model, affect the evaluated particle sizes for LII. A sensitivity analysis of the LII model identified the ambient-flame temperature as a major source of uncertainty in the evaluated particle size, a conclusion that was supported by an analysis based on temporal LII profiles.