消光起伏法中的颗粒交叠效应

消光起伏法是一种新的颗粒测量方法,可用来同时测量两相流中颗粒的粒径分布和体积浓度.由于在测量原理和结构上非常简单,这种方法可以用来实现在线、实时测量.本文讨论窄光束中颗粒系统在时间域内的消光起伏光谱,在几何光学近似下通过统计方法得到颗粒交叠的百分率与单层颗粒面密度β和颗粒系统层数NML之间的关系.在理论上得到了多层颗粒系统的消光起伏光谱与单层消光起伏光谱之间的关系,定性证明了颗粒交叠效应的存在.并通过数值模拟计算初步得到了消光起伏光谱的频率响应与消光值之间的关系.     

涂料中消光剂性能研究

从孔体积、颗粒大小、表面处理、干膜厚度方面研究了消光剂的消光效率的影响因素。结果表明孔体积越大颗粒越大,消光效率越好,若考虑到表面的光滑度,可选用经表面处理的消光剂。     

涂料中消光剂性能研究

从孔体积，颗粒大小，表面处理，干膜厚度方面研究了消光剂的消光效率的影响因素。结果表明孔体积越大颗粒越大，消光效率越好，若考虑到表面的光滑度，可选用经表面处理的消光剂。     

二氧化硅消光剂研究进展

1涂料用二氧化硅消光剂的性能要求对传统涂料的消光研究表明．有效的消光或降低光泽有赖于涂层表面形成微细的粗糙表面。涂层要形成微细的粗糙表面必须具备两个条件：一是漆膜中存在大量粒径适宜的消光剂颗粒．二是涂膜干燥过程中产生体积收缩。涂料中所使用的消光剂应能满足以下基本要求：     

低聚合度消光PVC树脂的研制

研究了低聚合消光PVC树脂生产中，消光剂品种的选择、复配、用量、加料方式及聚合温度控制等对低聚合度消光树脂的性能影响，并对该工艺下制备的低聚合度消光树脂进行了物化性能、相对分子质量及其分布、颗粒形态及消光性能检测，最终生产出分子量≤700，凝胶含量≥25%的低聚合度消光树脂。     

消光测粒反演方法的正则化参数优化

独立模式反演算法求解消光法颗粒粒径测量中病态反演问题,参数优化线准则的参数优化性能,通过数值模拟和实测数据验证,讨论了上述准则在消光法测粒反演中的应用.表明它们均具有一定的数据误差自适应能力.结合Twomey-NNLS算法,对单峰分布颗粒系给出合理的反演结果.     

白炭黑消光剂溶剂型涂料的发展及应用

在涂料中加入颜料或填料，均匀分布于涂料膜中并形成一种微粗糙面。表面颗粒越大，微粗糙程度越大，光泽就越低。有时生产无光涂料使用轻质碳酸钙或滑石粉等，用量较大，常常超过涂料的临界颜料体积浓度而使涂膜的物理性能变差，如分层和硬沉淀等现象，使用消光剂可避免这一现象。常用的消光剂分有机和无机2类，无机消光剂主要是白炭黑消光剂，其化学成分是二氧化硅，分为表面经有机物处理和未处理2种。现着重讨论白炭黑消光剂在涂料中的应用：     

聚酯切片中二氧化钛凝聚粒子的测定

<正> 一 引言 聚酯切片中凝聚粒子的颗粒度及其数量对熔体的可纺性(尤其是高速纺丝),甚至纤维的性能有很大的影响,因此在聚酯纤维生产中必须测定切片中凝聚粒子,并定为一重要的品质指标。通常凝聚粒子有四类, 1.熔聚粒子 消光剂二氧化钛悬浮在乙二醇里加到物料中时,由于二氧化钛颗粒度过大,浓度过高或搅拌不匀而产生这种粒子。据杜邦公司介绍,单个二氧化钛熔凝粒子的颗粒度约为0.3微米,而多个粒子的     

两种Primid共挤消光体系聚酯树脂的合成与研究

正1.前言目前低光粉末涂料多以户内混合型为主,在消光剂的配合下,可以做到众多不同程度的光泽。而户外聚酯粉末涂料由于消光剂对其反应体系作用有限,所以很难与消光剂一起挤出制备低光粉末涂料,目前户外低光粉末涂料主要是靠两种不同反应活性的粉末涂料进行干混消光。干混消光虽然可以得到较低的光     

水性涂料中防霉剂的选择

涂料中的消光剂是一类能够改变涂膜表面光学性能的助剂。这类助剂能够在涂膜表面产生预期微粗糙度,使涂膜的光泽显著降低。在涂料中加入颜料或填料,使之凸现于涂膜表面,也可以向涂膜表面引入微粗糙度。表面的颗粒越多,微粗糙度越大,光泽度越低。生产无光涂料可以使用填料(例如轻质碳酸钙和滑石粉等),但所需要的用量较高,常常会超过涂料的临界颜料体积浓度而使涂膜的物理性能变差,而使用消光剂则可以避免这一问题。     

Zirconia with Defined Particle Morphology and Hierarchically Structured Pore System Synthesized via Combined Exo‐ and Endotemplating

Highly porous zirconia with defined particle morphology can be prepared by impregnation of spherical activated carbon as an exotemplate with a zirconia nanoparticle sol. The resulting zirconia spheres show a particle size distribution between 0.2 and 0.4 mm and exhibit high specific surface areas and specific pore volumes up to 104 m²g^–1 and 0.56 cm³g^–1, respectively. Addition of a triblockcopolymer (TBC) as an endotemplate during the synthesis leads to the formation of an additional pore system. The corresponding spherical zirconia products possess a hierarchically structured pore system with a bimodal pore size distribution with maxima at ca. 3 and 20 nm. The relative fraction of pores originating from the endotemplate can be varied by changing the endotemplate content in the zirconia nanoparticle sol. The presence of the TBC also has an influence on the specific surface area and the specific pore volume. Using the ratio of TBC to zirconium of n_TBC/n_Zr = 0.027, a material can be prepared that exhibits a specific surface area and a specific pore volume of 161 m²g^–1 and 0.62 cm³g^–1, respectively. These values are more than twice as high as for zirconia prepared by a conventional precipitation method (68 m²g^–1 and 0.11 cm³g^–1, respectively).     

Synthesis of ZSM‐5 by hydrothermal method with pre‐mixing in a stirred‐tank reactor

This work proposed a synthesis route of ZSM‐5 via the hydrothermal method with premixing in a stirred tank reactor (STR). Effects of various operating conditions, including pre‐mixing time, molar ratio of SiO₂/Al₂O₃, TPAOH (organic template agents) concentration, NaCl (alkali metal cations) concentration, crystallization temperature, and crystallization reaction time, on the average particle size (PS) and particle size distribution (PSD) were investigated. It was found that the pre‐mixing time in the STR significantly affect the formation of proto‐nuclei in premixing process and crystal growth in hydrothermal reaction process, and consequently influence the PS and PSD of the prepared ZSM‐5. ZSM‐5 with good thermal stability, a PS of 380 nm, PSD of 0.17–0.9 µm, pore diameter of 2.31 nm, pore volume of 0.19 cm³ · g^?1 and specific surface area of 337.25 m² · g^?1 were obtained under the optimal conditions of a crystallization reaction time of 24 h, a crystallization temperature of 130 °C, a molar ratio of SiO₂/Al₂O₃ of 200, a TPAOH concentration of 3.5 mol · L^?1, NaCl concentration of 0.3 mol · L^?1, and a pre‐mixing time of 5 h. This work indicated that the operating conditions including premixing time have a significant effect on its PS and PSD.     

Hydrothermally prepared nanocrystalline Mn–Zn ferrites: Synthesis and characterization

Nanocrystalline particles of Mn_xZn_1−xFe₂O₄ were prepared by chemical precipitation of hydroxides, followed by hydrothermal processing and freeze–drying. The synthesis involves the hydrolysis of aqueous metal precursors by using ammonia as precipitating agent. The chlorine ion concentration in the solution and the pH of the precipitation, are shown to play a crucial role in retaining the initial stoichiometry of the solution to the nanoparticles. The obtained products exhibited some interesting and unique features: they consisted of nanoparticles with sizes ranging from 5 to 25 nm, they had surface areas between 60 and 110 m² g⁻¹ and pore sizes in the mesopore region (i.e. 8–20 nm). The produced materials were examined by powder X-ray diffraction for crystalline phase identification, scanning electron microscopy for grain morphology, high resolution transmission electron microscopy for particle size distribution and nitrogen sorption for surface area, pore volume and pore size distribution determination. The sintering of the ferrite powders was also studied by thermogravimetric analysis and dilatometry of the powders mixed with an organic binder to improve their compaction properties.     

Effect of mineral acids on the production of alumina nanopowder from raw bauxite

In this study a novel synthetic method for the large-scale production of spherical, high surface area and ultra-fine alumina (Al₂O₃) powder has been described. Synthetic Bayer liquor was extracted by alkali fusion of raw bauxite with sodium hydoxide. Alumina nanopowders were synthesised through a ball mill-aided precipitation method using the synthetic Bayer liquor and mineral acid precipitants. The powders produced were characterised by X-ray diffraction (XRD), particle size distribution (PSD), Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller surface area and pore size analysis, energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In this article, the effects of precipitants such as H₂SO₄, HCl and HNO₃ on crystallite and particle size, surface area, pore volume, and pore size and shape are reported. The experimental results prove that precipitation leads to an aggregated particle that is disaggregated by the ball-milling method. The ball milling process strongly influences the formation of uniform-sized spherical particles with a high surface area. It was revealed that nitric acid is an effective precipitant for controlling particle size and textural properties of Al₂O₃ powder. A nanopowder of γ-Al₂O₃ with an average crystallite size of 3 nm and an average particle size of 58 nm with a specific surface area (SSA) of 190 m² g^− 1 is produced. This article elucidates a new method with a simple reaction scheme for the mass production of Al₂O₃ nanoparticles from raw bauxite for various commercial applications.     

Preparation and performance of the novel PVDF ultrafiltration membranes blending with PVA modified SiO2 hydrophilic nanoparticles

In this study, PVA‐SiO₂ was synthesized by modifying silica (SiO₂) with polyvinyl alcohol (PVA), then a novel polyvinylidene fluoride (PVDF) ultrafiltration (UF) membrane was prepared by incorporating the prepared PVA‐SiO₂ into membrane matrix using the non‐solvent induced phase separation (NIPS) method. The effects of PVA‐SiO₂ particle on the properties of the PVDF membrane were systematically studied by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT‐IR), surface pore size, porosity, and water contact angle. The results indicated that with the addition of PVA‐SiO₂ particles in the PVDF UF membranes, membrane mean pore size increased from 80.06 to 126.00 nm, porosity improved from 77.4% to 89.1%, and water contact angle decreased from 75.61° to 63.10°. Furthermore, ultrafiltration experiments were conducted in terms of pure water flux, bovine serum albumin (BSA) rejection, and anti‐fouling performance. It indicated that with the addition of PVA‐SiO₂ particles, pure water flux increased from 70 to 126 L/m² h, BSA rejection increased from 67% to 86%, flux recovery ratio increased from 60% to 96%, total fouling ratio decreased from 50% to 18.7%, and irreversible fouling ratio decreased from 40% to 4%. Membrane anti‐fouling property was improved, and it can be expected that this work may provide some references to the improvement of the anti‐fouling performance of the PVDF ultrafiltration membrane. POLYM. ENG. SCI., 59:E412–E421, 2019. © 2018 Society of Plastics Engineers     

Soft-template synthesis of ordered mesoporous carbon/nanoparticle nickel composites with a high surface area

Ordered mesoporous carbon/nanoparticle nickel composites have been synthesized via multi-component co-assembly strategy associated with a direct carbonization process from resol, tetraethyl orthosilicate, Ni(NO₃)₂·6H₂O and triblock copolymer F127 and subsequent silicates removal with NaOH solution. The incorporation of rigid silicates in the pore walls can reduce framework shrinkage significantly during the pyrolysis process, creating large mesopores. Moreover, plenty of complementary small pores caused by silica removal are observed in the carbon pore walls, which contribute to the large surface area. The mesoporous carbon/nanoparticle nickel composites with a low Ni content (1.7 wt%) possess ordered two-dimensional hexagonal structure, large mesopores (6.8 nm), high surface area (1580 m² g⁻¹) and large pore volume (1.42 cm³ g⁻¹). Magnetic Ni nanocrystals with particle size of ∼16.0 nm are confined in the matrix of carbon frameworks. With increase of Ni content, the surface area and pore volume of the composites decrease. The particle size of metallic Ni nanocrystals increases up to 20.3 nm, when its content increases to 10 wt%. These carbon/nanoparticle nickel composites with high surface area, large pore size and superparamagnetic property show excellent adsorption properties for bulky dye fuchsin base and an easy separation procedure.     

Micro-mesoporous TiO2/SiO2 nanocomposites: Sol-gel synthesis,characterization, and enhanced photodegradation of quinoline

Micro-mesoporous TiO₂/SiO₂ nanocomposite powders have been successfully synthesized by the sol-gel process with different TiO₂/SiO₂ molar ratios and were applied in the UV-photodegradation of quinoline (λ = 254 nm). The structural, morphological, and textural characterization of the powders showed a homogeneous distribution of TiO2 nanoparticles within a porous amorphous SiO2 matrix. Due to the micro-mesoporous character of the materials, their textural characteristics were evaluated by the N2 adsorption method, by comparing BET, DR, Langmuir, and DFT theories. Si₆₀Ti₄₀ powders (60%SiO₂/40%TiO₂) presented the highest specific surface area (SSA) obtained from BET (SSA = 363 m²g^-1), DR (SSA = 482 m²g^-1), and Langmuir (SSA = 492 m²g^-1) due to the adequate particle size of TiO₂ and its high dispersion in the porous matrix. A higher degradation of quinoline in the presence of H₂O₂ (66%) was achieved using Si₈₀Ti₂₀ powders (80%SiO₂/20%TiO₂), as compared to pure sol-gel TiO₂ powders, (51%) under the same reaction conditions (1 UVC lamp - 250W, t = 180 min). The better performance of the Si₈₀Ti₂₀ nanocomposite could be attributed to the small TiO₂ anatase crystallite size (<5.7 nm), high dispersion of these crystallites in the SiO₂ matrix, great specific surface area (DR SSA = 342 m² g^?1), and the formation of Ti–O–Si bond, which is associated with new catalytic sites in TiO₂/SiO₂ composite.     

微通道内双重孔结构SiO2微球的制备

利用微流控技术制备双重孔结构SiO₂微球具有微观结构和宏观形貌可控的优点。在同轴环管微通道中,通过pH和温度变化引发快速凝胶过程制备得到了具有双重孔结构的SiO₂微球,考察了有机相溶剂性质、有机相流速以及凝胶温度等因素对微球宏观形貌以及微观结构的影响规律。实验结果表明,制备得到的SiO₂微球粒径在300～600 μm可调,比表面积可以达到1000 m²·g^-1,介孔孔径在4～10 nm之间,大孔孔径在400～1500 nm之间。实验发现有机相流速的增大会导致微球粒径的减小,提高三辛胺对盐酸的萃取速率,加快二氧化硅溶胶粒子的凝胶过程,更易生成松散的网状大孔结构。较高的凝胶温度会增大SiO₂微球介孔的孔容和孔径。     

Effects of TiO2 starting materials on the synthesis of Li2ZnTi3O8 for lithium ion battery anode

Lithium zinc titanate (Li₂ZnTi₃O₈) anode materials have been successfully synthesized using rutile-TiO₂ with different particle sizes as titanium sources via a molten-salt method. Various physical and electrochemical methods are applied to characterize the effects of TiO₂ particle sizes on the structures and physicochemical properties of the Li₂ZnTi₃O₈ materials. When the particle size of TiO₂ is too small (10 nm), it is difficult to homogeneously mix TiO₂ with the other raw materials. Thus, the final product Li₂ZnTi₃O₈ has poor crystallinity, large particle size, small specific surface area, pore volume and average pore diameter, which are disadvantageous to its electrochemical performance. Using TiO₂ with the proper particle size of 100 nm as the titanium source, the Li₂ZnTi₃O₈ (R-100-LZTO) with excellent electrochemical performance can be obtained. At 1 A g⁻¹, 175.8 and 163.6 mA h g⁻¹ are delivered at the 1st and the 200th cycles, respectively. The largest capacities of 163, 133.3 and 122.5 mA h g⁻¹ are delivered at 2.5, 5 and 6 A g⁻¹, respectively. The good high-rate performance of the R-100-LZTO originates from the good crystallinity, small particle size, large specific surface area and average pore diameter, low charge-transfer resistance and high Li⁺ diffusion coefficient.     

Effect of boehmite sol on the performance of alumina microfiltration membranes

Precursor film method was used to prepare highly permeable ceramic microfiltration membranes in this work. The performance of alumina microfiltration membranes was improved by adding boehmite sol in the membrane precursor film. With increasing the boehmite sol content, the effective average pore size of the membrane was continuously decreased and the separation efficiency of the membrane was increased. These improvements were due to that the boehmite sol not only helped the dispersion of the α-Al₂O₃ powder in the membrane forming slurry, but also formed γ-Al₂O₃ in the gaps among the existed α-Al₂O₃ particles which was beneficial for membrane sintering and pore size decreasing. For the membrane prepared with 45 wt% boehmite sol, the effective average filtration pore diameter was 178 nm and the water permeance of the membrane reached 1691 Lm⁻²h⁻¹bar⁻¹, which was much better than the values reported before. Moreover, the reusability of the membrane was confirmed using a recycling test.