超细钛硅分子筛粒径的激光粒度分析

研究了试样浓度、超声波强度、分散时间及分散剂的加入对钛硅分子筛粒度测定结果的影响，结果表明，试样浓度低或高，粒度测定结果偏大；超声波强度的增大和超声波分散时间适当的延长有利于粒子的分散，也有利于粒度的准确测定；加入分散剂六偏磷酸钠后，测试结果重复性好。     

超细稀土氧化物粉体粒度测定

采用美国布鲁克海文仪器公司制造的90 Plus粒度仪测定超细稀土氧化物粉体粒度. 以氧化钇为研究对象, 研究了分散剂、悬浮介质、待测样品浓度、分散时间等因素对亚微米级氧化钇粉体粒度测量精度的影响. 由此确定了能准确测定亚微米级氧化钇粉体粒度的测量条件.     

动态光散射法测量颗粒粒径的溯源性

分别对动态光散射粒径测量仪的入射波长、散射角度、测量池温度进行校准,并对影响测量结果准确性各因素的不确定度分量进行了评价,校准后动态光散射仪的测量结果可溯源至国家计量标准。为消除多重散射、颗粒间相互作用、颗粒粒径分布对动态光散射测量结果的影响,建立了动态光散射测量结果修正方法。其中为消除多重散射及颗粒间相互作用的影响,需采用多浓度测量或线性回归的方法得到特定浓度下的颗粒粒径;为修正颗粒粒径分布对动态光散射测量结果的影响,需先采用SEM方法准确测量颗粒粒径分布,然后根据光强加权动力学平均粒径和数量平均粒径的理论公式,得到二者之间的差异。     

氧化钇粒度控制与测定

用氨水或碳酸氢铵与氯化钇溶液反应生成沉淀，煅烧沉淀制备了D50为0．45μmt 2-10μm的各种粒径的氧化钇粉末。分别采用Coulter MultisizerⅡ和90Plus粒度仪测定微米和亚微米级氧化钇粉体粒度，研究了分散剂，待测样品量，分散时间等因素对亚微米级氧化钇粉体粒度测量精度的影响。     

超声衰减谱测量电池浆料的粒度分布

电池浆料中颗粒状活性物质的粒度大小和分散均匀性对电池的内阻、 电压、 局部表面电流和总极化程度等性能有直接影响, 实现对其的在线实时测量对电池的质量控制具有重要意义. 基于电池浆料的高固含量、 高黏度和低透光性的特点, 本文利用超声衰减谱的方式测量了其粒度分布(PSD). 应用于电池浆料的粒度分布测量的最大难点是其利用超声衰减谱法预测粒度分布的模型需要难以获得的分散相和连续相的物性参数. 本文采用主成分分析(PCA)结合误差反向传播(BP)神经网络建立预测模型解决了超声衰减谱法的难点, 并引入遗传算法(GA)优化BP神经网络的初始阈值和权值. 通过以LiCoO₂为活性物质的电池浆料进行了验证, 结果表明, PCA-GA-BP神经网络能够有效对不同固含量电池浆料的粒度分布进行预测, 预测值与真实值的峰形重合度高, 峰高偏差小, 两者的均方误差为0.1358, 拟合度(R²)为0.9816, 说明超声衰减谱法可作为测量电池浆料粒度分布的重要方式.     

粒度分析及粒度标准物质研究进展

综述了当前粒度分析测试方法的研究进展,并简单介绍了各种测试方法的基本原理以及包括美国、欧洲、中国在内的国家和地区在粒度标准物质方面的研究概况。     

纳米ATO颗粒粒度分布的脉冲超声波测量研究

讨论了脉冲超声波测量纳米ATO颗粒粒度分布方法中的3个步骤,即超声波衰减谱测量、严格数学模型的选型以及颗粒粒度分布的反演计算.通过发射脉冲超声波并利用变声程方法测量25 ℃时2%(体积分数)的纳米ATO-H2O分散液的超声衰减谱;选取McClements理论模型叠加BLBL理论模型共同描述纳米ATO颗粒分散液中的超声衰减现象;采用最优正则优化反演算法反演得到纳米ATO颗粒的粒度分布以及平均粒径.脉冲超声法检测结果显示,纳米ATO颗粒的平均粒径为25.6 nm,粒度分布为11.4 ～47.1 nm,CPS离心沉降纳米粒度分析仪测定结果分别为22.1 nm和10.1 ～62.6 nm.脉冲超声法检测结果与透射电镜图像以及离心沉降纳米粒度分析仪检测结果吻合较好,证明了脉冲超声波测量纳米颗粒粒度分布以及平均粒径的可行性与可靠性.     

Particle Size Distribution Measurement and Assessment of Agglomeration of Commercial Nanosized Ceramic Particles

ABSTRACT

Commercially available powders with primary particle sizes of 10–100?nm (transition aluminas, Boehmites, and a commercially available silica dispersion) have been studied using three different instruments, a photocentrifuge (Horiba CAPA 700), photon correlation spectroscopy (PCS, Malvern Zetasizer 4), and an x-ray disc centrifuge (XDC, Brookhaven X-ray Disc Centrifuge BI-XDC). Particle size distributions for five powders were collected with each instrument and in conjunction with nitrogen adsorption measurements an agglomeration factor calculated. An example is given to show the importance of using a light scattering correction when measuring particle size distributions with a photocentrifuge for a gamma alumina powder where the uncorrected data can overestimate the D _V50 by up to a factor of 10 depending on the powder. The importance of the assessment of agglomeration and how different treatments such as milling modifies the agglomeration factor F _AG is illustrated for an “as received” and attrition milled gamma alumina. Results are discussed with respect to the assumptions and limitations of the different instruments. Results are presented after consideration of the hydrodynamic density in the sedimentation methods, and light scattering for the optical based methods. For narrow size distributions in the 15–25?nm range all three instruments show very a good correlation. When the size range approaches the 40–100?nm regime PCS is very sensitivity to small populations of agglomerates. The instrument giving the best resolution in the 10–100?nm range was found to be the XDC. The speed of measurement should also be born in mind and varies enormously from several minutes for the PCS to several hours for the sedimentation techniques. To assess the accuracy of the measured sizes a model spherical silica powder was analyzed on all the instruments as well as by image analysis. The results with the silica powder showed how the accuracy of the sedimentation methods depends strongly on a knowledge of the suspended particles hydrodynamic density. This can be effected greatly by particle or agglomerate porosity and the thickness of the electrical double layer in the aqueous dispersions investigated. The results with the silica suggest accuracy's on the size better than ±20% is difficult without an accurate hydrodynamic density whereas consistency between methods for narrow size distributions can be better than 5% for median volume diameters.     

同时测量纳米颗粒悬浊液粒度、密度及浓度的方法研究

提出了一种基于超声检测同时测量纳米颗粒悬浊液的粒度、密度和浓度的方法.设计了一套高频宽带脉冲超声波检测系统,以纳米掺锑氧化锡(ATO)悬浊液为研究对象,结合脉冲回波技术,获得了频率为17 ～ 26 MHz的声衰减谱.据此运用最优正则化方法求解粒度反演方程,得到纳米ATO颗粒的分布曲线,中位径为22.07 nm,该值与离...     

Measurement of Continuous Particle Size Distributions of Finely Dispersed Powders by the Dynamic Light Scattering

Dispersity of finely dispersed powders with continuous bell-shaped particle size distributions is measured. The measurements are performed using two different dynamic light scattering instruments, a transmission electron microscope, and a sedimentograph equipped with an X-ray detector. Correlation functions measured with the dynamic light scattering instruments are processed using the CONTIN and KLUB software packages. Comparative analysis of the results obtained by different methods demonstrated that a reliable information on the dispersity of samples with wide particle size distributions can be obtained but using a combination of several analytical methods.     

细粒度氧化钇生产的新方法

采用氨水与氯化钇溶液共沉淀制得Y(OH)3胶体, 再加草酸溶液转化, 可制得细粒度Y2O3粉末(D50=1～2 μm). 初步探讨了制备工艺中的有关因素, 在选定条件下, 沉淀过程物料浓度、温度、加入速度对最终产物D50有一定影响, 但不明显. 草酸沉淀母液最终pH值对D50影响最大.     

单颗粒气溶胶飞行时间质谱仪在细颗粒物研究中的应用和进展

单颗粒气溶胶质谱技术起源于20世纪70年代,在近二十年得到了快速的发展.单颗粒气溶胶飞行时间质谱仪具有高时间分辨率,且同时测量大气中单个细颗粒物粒径、多种化学组分和混合状态的特点,在大气细颗粒物监测和科学研究中逐渐得到了广泛应用.本文对单颗粒气溶胶飞行时间质谱仪的发展历程进行了介绍,对目前已商品化的单颗粒气溶胶飞行时间质谱仪ATOFMS和SPAMS的原理、数据分析方法、结果输出方式以及在环境监测和研究中的主要应用进行了总结,并指出单颗粒气溶胶飞行时间质谱仪的发展方向.     

Maximum Achievable Particle Size in Emulsion Polymerization: Modeling of Large Particle Sizes

A simplified model for particle formation in emulsion polymerization (comprising aqueous‐phase propagation to degrees of polymerization which may enter a pre‐existing particle and/or form new particles by homogeneous or micellar nucleation, coupled with the aqueous‐phase and intra‐particle kinetics of oligomeric radicals) is formulated to provide a model suitable for the simulation of systems containing large‐sized particles. The model is particularly useful to explore conditions for growth of large particles while avoiding secondary particle formation. Applied to the Interval II emulsion polymerization of styrene with persulfate initiator at 50°C, it is found that there is an effective maximum particle size that can be achieved if the formation of new particles is to be avoided. The parameter space of initiator concentration, particle number concentration and particle radius is mapped to show a “catastrophe” surface at the onset of new nucleation. Advanced visualization techniques are used to interpret the large number of simulations in the series, showing a maximum achievable particle diameter of around 5 μm.     

Asymptotic Particle Size Distributions Attained during Coagulation Processes

The effects of the collision kernel on the self-preserving size distribution and on the gelation phenomenon of aerosol coagulation were investigated. An analytical solution for the asymptotic width of log-normally preserving size distribution during coagulation was obtained as a function of the degree of homogeneity using arbitrary shape of homogeneous collision kernels. From the solution obtained, it was shown that when the degree of homogeneity is larger than 1, self-preserving size distribution does not exist, and gelation occurs. A very accurate numerical coagulation simulation method, the sectional method, was also used for calculating the self-preserving particle size distribution for some specific classes of coagulation kernels and the results were compared with the analytical solution obtained by the log-normal method. Copyright 2001 Academic Press.     

SAPO-11分子筛的粒度调控

采用干凝胶法,通过向合成体系中添加适量的十六烷基三甲基溴化铵(CTAB)或氟化氢(HF)控制SAPO-11分子筛的粒度。采用SEM、XRD、IR、MAS NMR、TPD、TEM、TG-DSC以及低温N2吸附脱附对产物进行表征。结果表明,CTAB或HF的加入不仅能够减小分子筛的粒度,而且能调控分子筛骨架元素组成、表观形貌、孔道结构及酸性质等。其中,CTAB的加入有利于Si进入分子筛骨架,增加产物的酸量;HF的加入使样品由不规则的微米级颗粒调控为500 nm左右的棒状单晶,增强了分子筛的稳定性,但阻止了硅进入骨架,降低产物的酸量。     

Particle Size Limit for Concomitant Tuning of Size and Shape of Platinum Nanoparticles

Based on a polyol process, one-step synthetic procedures were investigated for concomitant control of the shape and size of platinum nanoparticles (Pt NPs). Cubic and octahedral/tetrahedral particles of different sizes (5–10 nm) were synthesized using these procedures. Further attempts to control the shape of the NPs below 3–4 nm failed. It was found that 3–4 nm is the particle size limit for Pt NPs above which the particle size and shape can be concomitantly controlled.     

Study of Stability of Sesame Oil-In-Water Emulsions Determined using an Optical Analyzer and Measurement of Particle Size and Distribution

The aim of the study was to determine the optimal conditions, that is, the content of sesame oil and the amount of carboxymethylcellulose, to obtain stable dispersion systems. Emulsions were stored under different temperature conditions. For this purpose, six emulsions were prepared and their stability was examined empirically using techniques including particle size analysis, optical microscopy, and the Turbiscan test. The emulsion containing 40 g of oil and 0.6 g of thickener had the highest stability. No destabilizations in whole the range of stored temperature were observed for the emulsion with that composition. Emulsion was stable as well at cool temperature as at extreme environment (40°C). Nowadays, the use of O/W emulsions based on vegetable oil is continuously increasing. To date, sesame oil has been used mainly for direct consumption. The present work indicates a novel possibility for use of sesame oil as the fat base of an emulsion system. Besides, the study gave information about parameters of long-term stability emulsion what is the key in the quality of the dispersion systems. This knowledge is necessary for the industry in order to avoid destabilizing processes occurring in a new product.     

4种激光粒度仪对下蜀土湿法粒度测试的对比研究

使用4种应用较为广泛的激光粒度仪(Mastersizer2000、Bettersize2000、Horiba LA950和LS13320)对粒度差异较小的下蜀土(土塘剖面)进行了测试,从而对比分析不同激光粒度仪对于下蜀土的粒度组成测试差异及其这种差异对研究结果可能产生的影响.结果表明:对粉砂颗粒组分的分析,4种激光粒度分析仪分析结果的差异最小,而对砂和粘土颗粒组分分析的差异最大.就粒度频数曲线、概率累积曲线、粒度组分、C-M图、粒度参数散点图及粒度参数剖面垂向变化等统计参数与统计方式而言,4种仪器的测试结果均有一定的差异,其中,概率累积曲线、粒度参数散点图差异较大.粒度参数的剖面变化差异也较大,影响了对剖面的阶段性划分,这在一定程度上影响了研究结果,造成使用不同仪器,可能会得出不同的结果.     

Effect of Different Composition on Particle Size Chitosan-PMAA-PNIPAM Hydrogel

Chitosan-based (chitosan-poly(methacrylic acid)-poly(N-isopropylacrylamide) [Cs-PMAA-PNIPAM] copolymer hydrogels were synthesized by free radical emulsion polymerization to study the effect of different composition of monomer on hydrogel particle size. Chitosan usually applied for medical use such as drug delivery due to its biodegradability, bio-compatibility, and non-toxicity properties. Co-polymerized chitosan with MAA and NIPAM is an improvement of chitosan gel to be more responsive to the environment of human body included different pH, temperature, ionic strength, electric field, and enzyme activities. Small size of the particles is particularly important to ensure the particles reach the target site especially as a drug delivery. A full factorial experimental design (2³) was employed to identify which factors influenced most on the particle size. The design considered three factors which is amount of MAA, NIPAM and N,N’-Methylenebisacrylamide (MBA) while particle size are chosen as the responses of the variation on each composition. Particle size distribution was measured by laser diffractionin wet condition. From the design of experiment, NIPAM shows the main factor affected the particle size. However combination of the others factors also contributed on the whole size of the hydrogel.     

聚氨酯脲-丙烯酸酯水分散液的粒径及形态研究

研究了羧基含量、异氰酸酯指数（［ － ＮＣＯ］／［ － ＯＨ］） 、聚氨酯脲与聚丙烯酸酯组成比（ＰＵＵ／ＰＡ） 以及一系列制备工艺因素对聚氨酯脲—丙烯酸酯（ＰＵＡ） 水分散液粒子尺寸及形态的影响。结果表明：羧基含量和ＰＵＵ／ＰＡ 组成比增大或异氰酸酯指数减小都会导致分散液粒径减小;ＰＵＡ 中ＰＡ 含量越大,ＰＵＡ 水分散液粒子形态越不规整;工艺因素如搅拌强度、升温速率等对ＰＵＡ 水分散液粒子尺寸及形态的影响不符合传统乳液聚合的规律。