岛津离心粒度分析仪测量模式的比较

分别对沉降式离心粒度分析仪的自然沉降与混合沉降以及混合沉降与离心沉降进行了比较试验,结果表明,当最大粒径值达到混合沉降测量模式的上限,即临界粒径值时,应对两种测量模式进行比较试验,才能从中选出最佳测量模式;对超细粉体而言,4μm以下的颗粒才适合选用离心沉降模式,最大粒径大于4μm时,应用混合沉降模式测量。     

水中微气泡光散射偏振特性的研究

在Mie散射理论的基础上，建立气泡光散射模型，计算水中微小气泡与固体微粒在不同的粒径参数和散射角条件下的光散射偏振特性，并对两者进行比较．结果表明，水中气泡及微粒对入射光散射后偏振状态的改变十分复杂．总体上气泡的退偏振效应比固体微粒强25％，微小气泡与固体微粒对偏振状态的影响在粒径域和散射角上具有选择性．     

微粒直径对气－固两相流固体微粒浓度的光－电测量法的影响

光－电检测法应用于气－固两相流微粒浓度的测量时，被测固体颗粒直径的变化对测量结果将产生明显影响．以致使测量结果与实际状态相反．本文分析了固体颗粒粒径对测量的影响，并提出了有效的修正方法．     

电爆喷涂中工艺参数对涂层性能的影响

电爆喷涂技术能够快速、方便地在玻璃等非金属表面制备金属涂层。通过对不同工艺参数下电爆喷涂实验样品的测试与分析,得到了工艺参数与涂层性能之间的关系。结果表明,电爆喷涂过程中,当电容器初始电压从10kV逐渐增大到20kV、金属丝直径由1mm逐渐减小到0.5mm、回路电感由10.8μH逐渐减小到3.9μH时,能够使金属丝的受热更加充分,爆炸产生的金属微粒的平均粒径更小,温度更高,飞行速度更快,因而形成的涂层更加致密、均匀,涂层电阻最小达到0.235mΩ。     

纳米 ZnO涂层对不同孔径 α-Al2O3微滤膜的修饰作用

采用不同粒径的α-Al2O3微粒，利用浸渍涂覆的工艺方法，在粒径为10μm的α-Al2O3载体上制备了厚度约为25μm的不同孔径的微滤膜．并以Zn（NO3）2和尿素为原料，采用共沉淀法，对上述不同孔径的微滤膜进行纳米ZnO涂层修饰改性．结果表明：采用ZnO改性后的微滤膜的水通量都得到了提高，且以粒径为0．5μm的α-Al2O3微粒构成孔径为0．15μm的微滤膜其水通量增幅最大；当Zn（NO3）2的浓度为0．3mol／L，经二次涂覆后，改性作用最佳，微滤膜的水通量增幅最高达到46．4％．同时，文中还对纳米ZnO涂层改性作用机理进行了初步探讨．     

搅拌磨中研磨介质大小对氧化锌超细研磨的影响

采用2种直径分别为0.4⁰.6、0.80.6、0.8¹.0 mm的氧化锆球,研究研磨介质大小对湿法研磨过程中氧化锌粒径的影响,并利用粉磨动力学模型分析研磨过程中的破碎机理。结果表明,采用直径为0.41.0 mm的氧化锆球,研究研磨介质大小对湿法研磨过程中氧化锌粒径的影响,并利用粉磨动力学模型分析研磨过程中的破碎机理。结果表明,采用直径为0.4⁰.6 mm的研磨介质研磨30 min时,氧化锌粒径可达到最小,即d50为0.9μm,d90为2.41μm;研磨介质直径为0.40.6 mm的研磨介质研磨30 min时,氧化锌粒径可达到最小,即d50为0.9μm,d90为2.41μm;研磨介质直径为0.4⁰.6 mm时的破碎速率明显大于直径为0.80.6 mm时的破碎速率明显大于直径为0.8¹.0 mm时的破碎速率,且破碎颗粒分布在较小的粒径范围内;在研磨过程中冲击破碎和摩擦破碎同时存在,研磨介质直径为0.41.0 mm时的破碎速率,且破碎颗粒分布在较小的粒径范围内;在研磨过程中冲击破碎和摩擦破碎同时存在,研磨介质直径为0.4⁰.6 mm时摩擦破碎的比例大于直径为0.80.6 mm时摩擦破碎的比例大于直径为0.8¹.0 mm时的比例。     

重力沉降法测定水-柴油乳化液粒径分布

针对目前油包水乳化液粒径分布测试困难的问题,采用经流变系数修正后的重力沉降法对入口浓度5 000 mg/L、乳化泵转速1 800 r/min的油包水乳化液进行粒径分布测试,并利用显微镜观测法进行结果验证。对比两种方法的测试结果,重力沉降法测试结果中位粒径13μm,粒径分布范围5~40μm,显微镜观测法测试结果为中位直径15μm,粒径分布范围为5~40μm,两种方法的结果一致性较高。实验结果证明:经流变系数修正后的重力沉降法可以准确测试油包水乳化液粒径分布,且该方法测试原理简单、操作简单、测试成本小,在工业现场测试上有一定的优势。     

静电纺丝法制备聚苯乙烯微纳米纤维膜及其过滤性能

采用静电纺丝法制备聚苯乙烯(PS)微纳米纤维膜,研究了静电纺丝工艺对PS纤维膜微观形貌、纤维直径以及孔隙尺寸分布的影响,并表征了其对固体颗粒物的过滤性能。结果表明:随着纺丝电压和接收距离的增加,PS纤维膜的直径和孔隙尺寸均减小且分布集中,随着推进速率增加,PS纤维膜的直径和孔隙尺寸逐渐增加且分布范围变宽;当纺丝电压为24kv,收集距离为24cm,推进速率为0.318mL/h时所得PS纤维膜的直径和孔隙中位径分别为940.1nm和1979.4nm,过滤尺寸范围为0.1~35μm的固体颗粒后,剩余颗粒的平均粒径仅为2.19μm。     

物理气相沉积热障涂层批量生产用球坑仪快速测厚法研究

为了满足热障涂层批量生产时对厚度快速、准确检测的需要,本文选用球坑测厚法对物理气相沉积热障涂层厚度进行了测量研究。首先在GH3039高温合金基体上分别制备厚约120μm的NiCrAlYSi涂层和Zr O₂·Y₂O₃(YSZ)涂层,研究了研磨液粒径、研磨时间等参数与磨坑直径的关系,随后根据试验结果对高温合金试片涂覆的NiCrAlYSi/YSZ热障涂层使用球坑测厚法进行了厚度测量,并与金相测厚法结果进行了对比。结果表明：NiCrAlYSi涂层和YSZ涂层磨坑直径与研磨时间均满足抛物线增加关系;相同条件下,所用研磨液粒径为5μm和10μm时获得的磨坑直径相当,均比1μm时的大;针对同一涂层,球坑测厚法与金相测厚法测量结果吻合度高,误差在6%以内。     

Ni-金刚石复合电沉积的界面作用力及其对复合量的影响

采用复合电沉积技术制备Ni-金刚石复合镀层,实验中镀层微粒含量可控制在1.47%～15.6%(质量分数)范围;测定了金刚石微粒在电极上的附着率和金刚石微粒与新生镍间的界面作用力,研究了电流密度、搅拌强度及方式、微粒粒径等工艺参数对复合量的影响.结果表明:金刚石微粒进入镍镀层所需要的滞留时间极短,在此过程中,界面作用力是主要因素,而非简单的几何形状的锁定或机械啮合作用,该作用力大小约3.3×103N/m2;间歇搅拌可提高复合量.     

Development of a double-layered ceramic filter for aerosol filtration at high-temperatures: the filter collection efficiency

The performance of double-layered ceramic filters for aerosol filtration at high temperatures was evaluated in this work. The filtering structure was composed of two layers: a thin granular membrane deposited on a reticulate ceramic support of high porosity. The goal was to minimize the high pressure drop inherent of granular structures, without decreasing their high collection efficiency for small particles. The reticulate support was developed using the technique of ceramic replication of polyurethane foam substrates of 45 and 75 pores per inch (ppi). The filtering membrane was prepared by depositing a thin layer of granular alumina-clay paste on one face of the support. Filters had their permeability and fractional collection efficiency analyzed for filtration of an airborne suspension of phosphatic rock in temperatures ranging from ambient to 700 degrees C. Results revealed that collection efficiency decreased with gas temperature and was enhanced with filtration time. Also, the support layer influenced the collection efficiency: the 75 ppi support was more effective than the 45 ppi. Particle collection efficiency dropped considerably for particles below 2 microm in diameter. The maximum collection occurred for particle diameters of approximately 3 microm, and decreased again for diameters between 4 and 8 microm. Such trend was successfully represented by the proposed correlation, which is based on the classical mechanisms acting on particle collection. Inertial impaction seems to be the predominant collection mechanism, with particle bouncing/re-entrainment acting as detachment mechanisms.     

Particle formation in ambient MALDI plumes

The ablated particle count and size distribution of four solid matrix materials commonly used for matrix-assisted laser desorption ionization (MALDI) were measured with a scanning mobility particle sizer (SMPS) combined with a light scattering aerodynamic particle sizer (APS). The two particle sizing instruments allowed size measurements in the range from 10 nm to 20 μm. The four solid matrixes investigated were 2,5-dihydroxybenzoic acid (DHB), 4-nitroaniline (NA), α-cyano-4-hydroxycinnamic acid (CHCA), and sinapic acid (SA). A thin film of the matrix was deposited on a stainless steel target using the dried droplet method and was irradiated with a 337 nm nitrogen laser at atmospheric pressure. The target was rotated during the measurement. A large number of nanoparticles were produced, and average particle diameters ranged from 40 to 170 nm depending on the matrix and the laser fluence. These particles are attributed to agglomeration of smaller particles and clusters and/or hydrodynamic sputtering of melted matrix. A coarse particle component of the distribution was observed with diameters between 500 nm and 2 μm. The coarse particles were significantly lower in number but had a total mass that was comparable to that of the nanoparticles. The coarse particles are attributed to matrix melting and spallation. Two of the compounds, CHCA and SA, had a third particle size distribution component in the range of 10 to 30 nm, which is attributed to the direct ejection of clusters.     

Trace metal loading on water-borne soil and dust particles characterized through the use of split-flow thin-cell fractionation

The fate and transport of metallic pollutants through a watershed are related to the characteristics of undissolved solid particles to which they are bound. Removal of these particles and their associated pollutants via engineered structures such as settling ponds is one goal of stormwater management. Because the particles most often implicated in metal pollution have nominal diameters of <50 microm, Split-flow thin-cell (SPLITT) fractionation was investigated to study the metal loading as a function of particle settling rate. Several diverse particle samples--soil, urban dust, and parking deck sweepings--were fractionated using this technique, and the metal loadings were quantified with inductively coupled plasma-atomic emission spectrometry. Implications for stormwater management are discussed.     

波纹翅片管换热器表面粉尘沉积特性的实验研究

空调器室外换热器大多采用波纹翅片管,因使用过程中表面积灰而导致性能下降。本文通过搭建积灰可视化实验台来观测粉尘的分布特征并测定沉积量,研究波纹翅片管换热器表面的粉尘沉积特性。其中测试样件的翅片间距范围为1.6~3.2mm,喷粉浓度范围为80~280 kg/m~3,风速范围为1~3 m/s,喷粉时间为15~90 s。研究表明,粉尘主要沉积在换热器迎风面的翅片前缘处以及换热管的迎风面上;翅片间距小时易于粉尘沉积,翅片间距为1.6 mm样件上的单位面积粉尘沉积量较3.2 mm样件最多增加了52%;提高喷粉浓度会增加粉尘沉积,喷粉浓度为280 kg/m~3下的单位面积粉尘沉积量较80 kg/m~3最多增加了88.2%;高风速能够抑制粉尘沉积,风速为3 m/s下的单位面积粉尘沉积量较1 m/s最多下降了6.3%。     

Optical Probe for the In-Line Determination of Particle Shape, Size, and Velocity

A laboratory optical probe was developed to simultaneously determine the following particle characteristics: circularity, particle projection area, equivalent diameter of a circle, length of the particle outline or perimeter, maximum chord length, aspect ratio, and particle velocity. Using the projection area and the perimeter, the particle shape factor circularity can be determined. The aspect ratio was approximated by the ratio of the equivalent diameter to the maximum chord length. The basic measuring principle is multi-point scanning of the particle shadow image by a line of optical fibers. In addition, the particle velocity can be measured by a differential spatial filter of optical fibers. These fibers are step index fibers with a core diameter of 64 µm and cladding of 70 µm. The shadow image of a single particle was generated by a parallel laser beam. The uncertainty of the measured circularity and aspect ratio was investigated by using metal wires with diameters of 0.12 to 0.5 mm as test particles with known circularity and aspect ratio. The standard deviations were 1.9% for the circularity and 15.5% for the approximated aspect ratio. In addition, the optical probe system was investigated by measurements of solid particles with different shapes. As an example, the results of sand, marjoram seed, and metallic oxide particles are shown. Using 1000 sand particles, the correlation between equivalent diameter and particle velocity could be demonstrated. The presented configuration of the optical probe is applicable in the size range of 0.1 to 0.9 mm and up to a particle velocity of 5 m/s.     

链转移剂加入方式对丙烯酸酯乳液聚合过程及压敏粘接性能的影响

报道了三种不同链转移剂加料方式制备的丙烯酸丁酯共聚物乳液,其固含量为50%,并研究了它们的压敏特性。动态光散射跟踪了聚合过程乳胶粒粒径的变化,结果显示,该乳液聚合没有明显的二次成核过程,按预定的粒径生长。用凝胶渗透色谱(GPC)和动态力学分析(DMA)表征了聚合物的分子参数,按照FINAT标准测试了该乳液压敏胶的初粘力、剥离力和耐剪切强度,并将压敏性能与分子参数,如凝胶含量和聚合物分子量进行了关联。     

Optical Probe for the In-Line Determination of Particle Shape,Size, and Velocity

A laboratory optical probe was developed to simultaneously determine the following particle characteristics: circularity, particle projection area, equivalent diameter of a circle, length of the particle outline or perimeter, maximum chord length, aspect ratio, and particle velocity. Using the projection area and the perimeter, the particle shape factor circularity can be determined. The aspect ratio was approximated by the ratio of the equivalent diameter to the maximum chord length. The basic measuring principle is multi-point scanning of the particle shadow image by a line of optical fibers. In addition, the particle velocity can be measured by a differential spatial filter of optical fibers. These fibers are step index fibers with a core diameter of 64 µm and cladding of 70 µm. The shadow image of a single particle was generated by a parallel laser beam. The uncertainty of the measured circularity and aspect ratio was investigated by using metal wires with diameters of 0.12 to 0.5 mm as test particles with known circularity and aspect ratio. The standard deviations were 1.9% for the circularity and 15.5% for the approximated aspect ratio. In addition, the optical probe system was investigated by measurements of solid particles with different shapes. As an example, the results of sand, marjoram seed, and metallic oxide particles are shown. Using 1000 sand particles, the correlation between equivalent diameter and particle velocity could be demonstrated. The presented configuration of the optical probe is applicable in the size range of 0.1 to 0.9 mm and up to a particle velocity of 5 m/s.     

陶瓷颗粒表面沉积层性能的研究

采用化学气相沉积技术对氧化铝颗粒表面进行沉积层处理, 研究了沉积层的高温抗氧化性, 沉积层的结合强度以及沉积层对氧化铝颗粒与金属基体界面结合强度的影响。结果表明: N i 沉积层的氧化产物有助于提高界面湿润性、改善界面结构; 沉积层的膜基分离结合强度较高; 沉积层可明显提高氧化铝陶瓷与金属基体间的界面结合强度, 且有沉积层时的界面结合强度是无沉积层时的6 倍多, 界面无缝隙存在。      

Entrainment of Heterogeneous Particles from Gas-Fluidized Bed

The entrainment of heterogeneous particles in a gas-fluidized bed for particle mixtures of categories A and B according to the Geldart classification was conducted in this study. The experiments were carried out in an acrylic column of 0.092 m diameter. The distributors were perforated plates of up to 5.9% free area fraction. Measurements of pressure gradients were made using 24 pressure taps. Glass beads with particle diameters from 60 to 400 μm were used. The mixtures were described using the Rosin-Rammler-Bennet granulometric distribution model. The transport disengaging height (TDH) heights were obtained using the Geldart methodology. A 2⁵ experimental design was applied relating the dispersion index, mean diameter, solid mass, superficial gas velocity, and free area fraction of the distributor to obtain the TDH heights. Slugging and transition for turbulence regimes characterized the behaviors of fluidized beds. The results showed that TDH heights for heterogeneous particles were dependent on the solid mass and superficial gas velocity.