Effect of the particle size and particle agglomeration on composite membrane performance

One of the most used methods for studying the rigidification of polymer matrices in composite membranes is differential scanning calorimetry. Glass‐transition temperatures give information about filler–polymer interaction and the rigidity of the polymer matrix. In this study, optical microscopy, mechanical property testing, and X‐ray diffraction, instead of differential scanning calorimetry, were used to study both poly(ether imide) (PEI) matrix rigidification and activated carbon–PEI interfacial adhesion. Then, the permselective properties of the mixed matrix membranes were interpreted. The change in rigidity in these composite membranes was in agreement with the decrease in the flexibility of the composite materials as the filler content increased. This fact was confirmed by the tension and elongation data and X‐ray diffraction (DRX) measurements. However, the Young's modulus value decreased as the carbon content increased. There was an increase in all of the gas permeability coefficients measured in the composites compared with that of PEI. As the particle size grew, a low particle surface area and a poor interfacial adhesion were observed. The carbon agglomerates acted as sites of stress concentration within the polymeric matrix. This decreased the intercatenary distances and limited the movement of polymer chains, which resulted in a more rigid matrix. The higher selectivity of the H₂/CH₄, H₂/CO₂ and O₂/N₂ systems observed in the composite membranes revealed that there were both a preferential sorption of certain gases in the carbon surface or carbon–polymer interface and a molecular size exclusion, which were responsible for that increment, despite the poor interfacial adhesion. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of preparation method on activity and stability of LaMnO3 and LaCoO3 catalysts for the flameless combustion of methane

A set of LaMnO₃ and LaCoO₃ catalysts was prepared through different synthesis procedures. The selected techniques included the sol–gel method, flame hydrolysis from aqueous solution, complexation through EDTA and solid-state reaction. The last was accomplished through reactive grinding by ball-milling either in a vibration mill or in a planetary mill. EDTA complexation was applied for LaCoO₃ only and did not improve significantly catalyst activity or stability, with respect to other techniques. Ball-milling never allowed obtaining a pure perovskitic phase, at least under the most energetic grinding conditions permitted by our apparatus. The highest activity for the catalytic flameless combustion of methane was obtained with the sol–gel prepared samples, though thermal resistance revealed insufficient for high temperature applications. A bit lower activity, but coupled with good thermal stability was obtained with the samples prepared through flame hydrolysis.     

粉磨工艺对水泥颗粒分布及其混凝土性能的影响

研究了不同粉磨工艺系统磨制水泥的颗粒分布、粉磨电耗、标准稠度用水量、与减水剂相容性及其配制的混凝土强度、耐磨性、抗碳化性能的差异;针对我国混凝土行业的现状,从混凝土性能的角度出发,探讨了现阶段各种水泥粉磨工艺的特点。研究结果表明,水泥粉磨工艺系统的效率越高,水泥的颗粒分布越集中,水泥的标准稠度用水量增大,与减水剂相容性变差,在缺乏良好的掺合料进行颗粒分布校正的前提下,所配制混凝土的强度、耐磨性及抗碳化性能均有所下降。     

颗粒粒径对20%咯菌腈悬浮剂性能的影响

[目的]研究颗粒粒径与悬浮剂性能之间的关系。[方法]考察了20%咯菌腈悬浮剂不同颗粒粒径对黏度、悬浮率、稳定性指数(TSI)和热储性能的影响。[结果]20%咯菌腈悬浮剂的黏度随着粒径的减小而增加。悬浮率随着粒径的减小先增加后保持不变。稳定性指数越小,悬浮剂稳定性越好,稳定性指数随着粒径的减小先逐渐减小后趋近于恒定。热储后的黏度和析水率都趋近于相同,和热储前颗粒粒径没有明确相关性。当热储前粒径较小时,热储后粒径趋近于相同,当热储前粒径较大时,热储后粒径没有明显变化。[结论]在一定粒径范围内,20%咯菌腈悬浮剂粒径越小,黏度越大,悬浮率越高,稳定性指数越小。热储后的粒径、析水率和黏度与配方组成有关,和热储前颗粒粒径无关。     

粒径对磺酸官能化介孔材料性能的影响

以聚乙氧基-聚丙氧基-聚乙氧基三嵌段共聚物(P123)为模板剂、正硅酸乙酯(TEOS)为硅源,保持P123和TEOS的浓度比,改变P123和TEOS在合成体系中的浓度,水热法合成了系列具有不同粒径的介孔分子筛SBA-15.采用后合成法,将3-巯基丙摹三甲氧基硅烷(MPTMS)嫁接到具有不同粒径的介孔分子筛SBA-15表面上,经氧化后得到含有强酸性的磺酸基因的固体酸样品SBA-15-SO_3H.采用SEM、XRD、FT-IR、TG-DTA、N_2吸附以及酯化反应考察了粒径对所制备的SBA-15-SO_3H的物化性能和催化性能的影响.结果表明,SBA-15的粒径大小对MPTMS在其上的嫁接量没有很人影响,但对后续氧化过程有较大的影响,SBA-15粒径的减小有利于巯基被氧化为磺酸基,导致磺酸的负载量随着粒径的减少而增大.SBA-15-SO_3H在乙酸和乙醇的酯化反应中表现出不同的催化性能,催化性能的差异是粒径大小、酸量及磺酸基和巯基相互作用的综合结果.     

粒径分布对嵌段聚醚氨基硅乳液性能的影响

通过机械搅拌、均质化等制备了一系列pH=5.9的嵌段聚醚氨基硅(BPEAS)乳液,用激光粒度分布仪和透射电子显微镜对乳液粒径和结构进行了表征,并探讨了不同粒径分布的乳液对整理织物性能的影响,确定了合适的粒径范围。结果表明,中位径(D50)分布在32.67～52.48 nm,粒径在58.77～98.82 nm时的累积分布达到90%以上的乳液具有较好的稳定性;经整理后的织物白度基本不变,弯曲刚度明显下降,亲水性增强,综合应用性能优异。     

SiC加入量和粒度对耐火浇注料性能的影响

以特级矾土骨料、氧化铝微粉、二氧化硅微粉、刚玉细粉、SiC和纯铝酸钙水泥为主要原料,研究了SiC加入量和粒度对耐火浇注料性能的影响。研究发现,在浇注料基质内加入6％的150目SiC,可以改善耐火浇注料的抗热震稳定性。     

Effect of blade angle and particle size on powder mixing performance in a rectangular box

This study focuses on the understanding of flow over a single blade and its impact on powder mixing. The Discrete or Distinct Element Method (DEM) is used and the flow of a single blade through a bed of a binary particle mixture is studied. Mixing performance with respect to a blade-rake angle and particle size is investigated using the Modified Generalized Mean Mixing Index (MGMMI) and the maximum mean instantaneous velocities. A wide range of angles and different loading scenarios of the binary particle mixture were studied. Velocity profiles for all these cases were computed, as well as the forces on particles and the blade. The results showed an inverse relation between the interparticle force and blade-rake angle. Systems with a higher number of larger particles experienced a higher interparticle force. Similar results were obtained for the blade force. The results for mixing efficiency showed that if the smaller particles are placed at the top this leads to a higher mixing performance. The mixing performance was highest for blade-rake angles that offered a maximal surface area or maximal resistance to the flow of particles, which occurred for blade-rake angles from 70° to 90°.     

Effect of particle size on the surface oxidation and flotation behavior of galena particles in lime system

ABSTRACT

In this research, the effect of particle size on the surface oxidation and flotation behavior of galena in the lime system was studied. Coarse (?0.074 + 0.038 mm), intermediate (?0.038 + 0.025 mm) and fine (?0.025 mm) galena particles were used in the experiment. The dissolution tests, flotation tests, and sorption tests were accomplished. Through further analysis by XPS, the effect of particle size and lime was observed. The decrease of mineral particle sizes increased the adsorption ratio of collector and the dissolution of galena, while the hydrophilic product OH^?/Ca(OH)⁺ produced by dissolution occupied the dominant position, which led to the minerals hydrophilic.     

Effect of platinum particle size and catalyst support on the platinum catalyzed selective oxidation of carbohydrates

The effect of the platinum particle diameter and the catalyst support was investigated for the aqueous phase selective oxidation of methyl α-D-glucopyranoside, octyl α-D-glucopyranoside and α-cyclodextrin with molecular oxygen. No platinum particle size effect was observed in the platinum particle diameter range of 1.4 to 3.0 nm. The structure-insensitivity is attributed to the high degree of surface coverage by oxygen. The rate of deactivation due to over-oxidation of the catalyst increases to a small extent with decreasing platinum particle diameter. The effect of the catalyst support is much larger than the platinum particle size effect. The turnover frequency for platinum on activated carbon and carbon fibrils supported catalyst is 3-7 times higher than for graphite as the catalyst support. The support effect is attributed to the hydrophilic character of the support. This revised version was published online in July 2006 with corrections to the Cover Date.     

正丁烷氧化装置主要设备的风险评估

应用RBI软件对正丁烷氧化装置的主要设备（限于R-160A／B氧化反应器、RE-165A／B盐浴冷却器,下同）以及附属的部分工艺管线进行了失效可能性与失效后果的分析与计算,确定了各设备项的风险大小及风险等级,分析了造成风险的可能因素,为将来正丁烷氧化装置的全面检验提供参考和依据,以保证设备安全、稳定和长周期运行的目的。     

高C3S水泥的颗粒组成与性能的关系

比较了两种不同矿物组成、不同颗粒级配的高C3S水泥的抗压强度和水化热与颗粒组成的关系。试验发现增加粉磨时间,水泥的抗压强度和水化放热量增加;抗压强度与平均粒径和均匀性系数的乘积(X·n)呈线性关系;抗压强度与0～30μm颗粒含量有明显的规律性。传统认为的水泥强度主要提供者3～30μm颗粒含量与抗压强度和水化热没有明显的规律性,因为增加粉磨时间3～30μm颗粒含量变化不大。     

Effect of nano-ZnO with different particle size on the performance of PVDF composite membrane

To evaluate the effect of nanoparticle size on the structure and performance of the membranes, polyvinylidene fluoride composite membranes modified by nano-ZnO with different particle size were successfully fabricated by the non-solvent induced phase inversion method. A series of tests, including contact angle measurement, porosity and pore size measurement, scanning electron microscope, atomic force microscopy, differential scanning calorimeter and filtration experiments were performed to characterise the composite membranes. The results showed that the size of nano-ZnO particle has an influence on the structure and performance of the composite membranes. The membrane with 90?nm nano-ZnO particle has abundant porosity, high hydrophilicity and low surface roughness. These features are responsible for its excellent permeability and antifouling property.     

制备方法对锆硅分子筛的催化性能影响

分别以水热法(DHT)、干胶法(DGC)和溶胶-凝胶法(Sol-Gel)合成了锆硅杂原子分子筛,采用XRD、TPD、SEM、TEM、FT-IR、N_2吸附-脱附等对分子筛样品的晶相结构、表面形貌、比表面积、孔径分布以及表面酸性进行表征。结果表明,水热法制备的锆硅杂原子分子筛特征峰明显,具有较高的结晶度,分子筛以微孔为主,并具有较多的酸中心和较大的比表面积,在α-蒎烯异构化反应中表现出较好活性和较高的柠檬烯选择性。     

Ce的掺杂对负载型催化剂LaMnO3/赤铁矿脱硝性能的影响

采用柠檬酸络合浸渍法,通过对A位离子进行掺杂或取代和调节Ce的掺杂量,制备了一系列的负载型催化剂La_1-xA_xMnO₃/赤铁矿（A=Ce、Co,x=0/0.1/0.2/0.3）,并将催化剂应用于固定床NH₃-SCR脱硝。采用XRD、BET、XRF、H₂-TPR、NH₃-TPD等表征手段对催化剂进行分析和表征。结果表明,Ce的掺杂提高了催化剂LaMnO₃/赤铁矿的低温脱硝效率和拓宽了催化剂的活性温度窗口,如La_0.8Ce_0.2MnO₃/赤铁矿催化剂,在180℃时,脱硝效率就高达98%,且在150～250℃温度区间的脱硝效率均在90%以上。结合表征分析证明,稀土元素Ce的适量掺杂,明显提高了LaMnO₃/赤铁矿催化剂的氧化还原能力和催化剂表面NH₃分子的吸附能力;稀土元素Ce的适量掺杂也改善了催化剂比表面积,也使活性物质高度分散在载体表面上。     

Effect of particle size on pigments colour

The historical pigments, contrary to modern ones, are not constituted by particles having all the same size and this influences the colour of the paint layers. The hiding power and colouring power of a pigment depends, in fact, on its particle size. The aim of this study was to evaluate the influence of particle size on optical characterization of paintings in terms of reflection of light and related colour specification. Starting from the qualitative observation, we have attempted to quantify the pigments colour variations induced by grinding and then attributable to granularity. Powdered pigments of principal colours have been selected in specific particle size range by mechanical sieving. The measurements were performed both on pigment pellets and on paintings realized with binder casein. All samples were characterized by an optical and colorimetric point of view through spectrophotometric analysis and for the surface morphological observation through scanning electron microscopy. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 236–243, 2017     

硅铁粉粒度对合成氮化硅铁的影响

采用FeSi75为原料,利用直接氮化合成法制备了氮化硅铁粉末,研究了中位径(d50)分别为13.41μm、8.023μm和5.229μm的3种硅铁粉分别在1150℃、1250℃和1350℃保温9h处理后的氮化规律。借助XRD、SEM等测试手段测定和观察了产物的物相组成和显微形貌。结果表明:较细的硅铁粉(d50=5.229μm)氮化时,反应快速、剧烈,导致烧结严重,氮化效果差,而较粗硅铁粉(d50=13.41μm)氮化效果较好;较细硅铁粉氮化后易于形成须状、纤维状和柱状氮化硅晶体,较粗硅铁粉氮化后易于形成球状氮化硅团聚体。制备的氮化硅铁中有大量充满氮化硅的孔洞,产物中的Fe3Si与FexSi被其包围,这种结构有利于体现氮化硅铁的优异性能。     

制备方法对CuO-ZnO-ZrO_2低温催化CO氧化性能的影响

采用不同制备方法(共沉淀法、柠檬酸络合法、溶胶凝胶法、模板剂法及均匀沉淀法)制备了Cu O-Zn O-Zr O2催化剂,考察了制备方法对催化剂物化性能及CO氧化性能的影响。通过X射线衍射、N2吸附-脱附、氢气程序升温还原等对制备的催化剂进行表征,结果表明,共沉淀法制备的催化剂比表面积和孔容积最大,分散度最高,平均晶粒尺寸最小。在CO氧化反应中,共沉淀法制备的样品CO低温氧化活性最高,连续反应100 h,稳定性能良好。在50℃、3 MPa的工况条件下,可将液相丙烯中CO体积分数脱除低至2×10-8,达到聚合级烯烃对CO脱除深度的要求。     

Effect of Al2O3 particle size on preparation and properties of ZTA ceramics formed by gelcasting

Zirconia-toughened alumina (ZTA) ceramics were prepared using three different kinds of Al₂O₃ powders (marked PW-A average particle size: 7.53 μm, marked PW-B average particle size: 1.76 μm, marked PW-C average particle size: 0.61 μm) by gelcasting. Effect of Al₂O₃ particle size on zeta potential, dispersant dosage and solid volume fractions of ZTA suspensions as well as the mechanical properties of ZTA green bodies and ceramics were investigated. The optimum dosages of dispersant for ZTA suspensions prepared by PW-A, PW-B and PW-C are 0.4 wt%, 0.5 wt% and 0.7 wt%, respectively. The highest solid volume fractions of ZTA suspensions can reach 62 vol% (SP-A), 60 vol% (SP-B) and 52 vol% (SP-C), respectively. The green bodies show a bending strength as high as 20 MPa, which can meet the requirement of machining. The Al₂O₃ powder with fine particle size is beneficial to the improvement of mechanical properties. The ZTA ceramics prepared by PW-B Al₂O₃ powder show the highest bending strength (680 MPa) and toughness (7.49 MPa m^1/2).