Computer vision-aided DEM study on the compaction characteristics of graded subgrade filler considering realistic coarse particle shapes

The compaction quality of subgrade filler strongly affects subgrade settlement.The main objective of this research is to analyze the macro-and micro-mechanical compaction characteristics of subgrade filler based on the real shape of coarse particles.First,an improved Viola-Jones algorithm is employed to establish a digitalized 2D particle database for coarse particle shape evaluation and discrete modeling purposes of subgrade filler.Shape indexes of 2D subgrade filler are then computed and statistically analyzed.Finally,numerical simulations are performed to quantitatively investigate the effects of the aspect ratio(AR)and interparticle friction coefficient(μ)on the macro-and micro-mechanical compaction characteristics of subgrade filler based on the discrete element method(DEM).The results show that with the increasing AR,the coarse particles are narrower,leading to the increasing movement of fine particles during compaction,which indicates that it is difficult for slender coarse particles to inhibit the migration of fine particles.Moreover,the average displacement of particles is strongly influenced by the AR,indicating that their occlusion under power relies on particle shapes.The dis-placement and velocity of fine particles are much greater than those of the coarse particles,which shows that compaction is primarily a migration of fine particles.Under the cyclic load,the interparticle friction coefficientμhas little effect on the internal structure of the sample;under the quasi-static loads,however,the increase inμwill lead to a significant increase in the porosity of the sample.This study could not only provide a novel approach to investigate the compaction mechanism but also establish a new theoretical basis for the evaluation of intelligent subgrade compaction.

Influence of filler characteristics on particle removal in fluid catalytic cracking slurry under an alternating electric field

The characteristics of the packing material under an alternating electric field are an important factor in the removal of FCCS particles.In this study,the electric field distribution of a separation unit consisting of packed spheres under an alternating electric field is simulated,and the movement mechanism of catalyst particles is analysed.An"effective contact point"model is derived to predict the adsorption of filler contact points on catalyst particles under the alternating electric field,and the model is validated by simulations and experiments.The numerical calculation and experimental results indicate that the electrical properties of the filler spheres,the filler angleθ,and the frequency f of the alternating electric field affect the adsorption of catalyst particles.As the frequency of the electric field increases,the particle removal efficiency of the high-conductivity filler(silicon carbide)increases and then settles,and the separation efficiency of the low-conductivity filler(glass,zirconia)is not sensitive to the change in electric field frequency.

Basic Characteristics of an Appropriate Waste Fillers for Solvent Free and Water-Borne Industrial Polymer Floors and Their Utilization

Recently the manufacture of epoxy coating and flooring materials begun to be under strong pressure to use more environmentally friendly raw materials in its composition.First tendency to reduce of solvents and diluents contained in the materials appeared at the end of 90´s.This situation was supported by the Council of Europe in 2004 to reduce VOC emissions to zero till 2020.Solvent materials were thus largely replaced by solvent free materials from which the volatile substances are not released into the air.But pressure continued to increase,and over the past decade began to take centre stage water-based epoxy.On the Czech market solvent based material is still occasionally used,but predominant are solvent free materials.There are no commonly used materials containing wastes as fillers in new water-borne and solvent-free epoxy materials.Characteristics identification of the waste material as a potential filler is a set of properties that determine the limits of secondary raw materials or waste as a filler.This paper describes the basic characteristics which must be selected to meet the requirements,to affect negatively the workability,sedimentation,properties and behavior of the final floor system.Some materials must comply with special requirements,such as resistance to chemicals,etc.Next part of paper talks about utilization of polymer floors and their mechanical properties.

Synthesis of Y_2O_3 Nano-Powder from Yttrium Oxalate under Ambient Temperature

High purity Y_2O_3 nano-powders was synthesized directly from solution ofindustrial YCl_3 by method of oxalate precipitation through super-micro-reactors made by complexnon-ionic surfactant. The purity and diameter of Y_2O_3 particles were controlled by such processingparameters as concentration of YCl_3 and oxalic acid and complex non-ionic surfactant etc. TEMphotomicrographs show that Y_2O_3 particles are spherical in shape, with an average diameter of lessthan 30 nm. Test results certify that the purity and particle diameter as well as the dispersion ofY_2O_3 nano-powder depend on the concentrations of YCl_3, oxalic acid and complex non-ionicsurfactant. The optimum ranges of the concentrations for YCl_3 and complex non-ionic surfactant whenthe diameter of Y_2O_3 particles is smaller than 100 nm are 0.43 ～1.4 mol ? L^(-1) and0.031～0.112 mol·L^(-1) respectively, while the mass fraction range of oxalic acid is 10% ～18% .The purity of Y_2O_3 nano-powder tested by ICP-AES analysis is 99.99% .

Progress on grain growth dynamics in sintering of nano-powders

Nanostructured materials, characterized by an ultrafine grain size, have stimulated much research interest by virtue of their unusual mechanical, electrical, optical, and magnetic properties. In this paper, the sintering process of nano-powders were reviewed, to which sintering of the traditional materials compared. The microstructural development, i.e., grain growth and densification during sintering as well as the mechanism of crystal surface diffusion and boundary migration were analyzed, and the dynamic models on sintering process were summarized by the relationship of grain growth and pores size, interface diffusion, densification rate, and sintering temperature. Finally, the research tendency of this major on the basis of above models was discussed.

ITO nano-powders prepared by microwave-assisted co-precipitation in aqueous phase

By using microwave-assisted co-precipitation in aqueous phase, adding surface activation agent PEG-6000 into the mixture of InCl3 solution and SnCl4 solution, and dropping the ammonia solution with the density (volume ratio) of 1-0 to 1-4, ITO precursor was prepared at different reaction system temperatures of 35 ℃-85 ℃, then ITO nano-powder was obtained after it was calcinated at 800 ℃ for 1 h. The morphology of ITO nano-powder was characterized by SEM and its electrical conductivity was determined by conductivity meter. The effects of different temperatures and ammonia concentration in microwave-assisted reaction system on its morphology and electric conductivity were discussed. The experimental results indicate that with the dilution of the ammonia solution or the rise of reacting system temperature, the morphology of ITO particles is transformed from spherical to rod-like one with the decline of its electric conductivity. And the electric conductivity of ITO nano-powders with spherical morphology is higher than that of ITO nano-powders with rod-like morphology.

The Critical Role of Fillers in Composite Polymer Electrolytes for Lithium Battery

With excellent energy densities and highly safe performance,solidstate lithium batteries(SSLBs)have been hailed as promising energy storage devices.Solid-state electrolyte is the core component of SSLBs and plays an essential role in the safety and electrochemical performance of the cells.Composite polymer electrolytes(CPEs)are considered as one of the most promising candidates among all solid-state electrolytes due to their excellent comprehensive performance.In this review,we briefly introduce the components of CPEs,such as the polymer matrix and the species of fillers,as well as the integration of fillers in the polymers.In particular,we focus on the two major obstacles that affect the development of CPEs:the low ionic conductivity of the electrolyte and high interfacial impedance.We provide insight into the factors influencing ionic conductivity,in terms of macroscopic and microscopic aspects,including the aggregated structure of the polymer,ion migration rate and carrier concentration.In addition,we also discuss the electrode-electrolyte interface and summarize methods for improving this interface.It is expected that this review will provide feasible solutions for modifying CPEs through further understanding of the ion conduction mechanism in CPEs and for improving the compatibility of the electrode-electrolyte interface.

Structure and Properties of PLA Composite Enhanced with Biomass Fillers from Herbaceous Plants

PLA composites containing biomass fillers from the three herbaceous plants such as reed,wheat stalk,and coco-nut fiber with length and diameter at the scale of several millimeters were prepared without using additives.The reinforcement effect on the properties of PLA/biomass filler composites is investigated.The research results show that the PLA/biomass filler composites exhibit good stiffness,flexural strength,and impact toughness.Among the three kinds of biomass fillers,reed reinforced PLA composites show optimal mechanical properties.When filled with 40%–50%reed,the flexural moduli of the composites are over 7000 MPa.Flexural strength retains at the same level of pure PLA.The notch impact strength reaches to 4.50±0.73 kJ/m^(2),which is 2.06 times higher than that of pure PLA.Furthermore,the introduction of biomass fillers increases the crystallization ability of PLA and does not increase the water absorption of the composites.This research demonstrated that PLA composites prepared with biomass fillers from the herbaceous plants(namely herb plastic composites,HPCs)is a material with good comprehensive mechanical properties while retaining the intrinsic particularity of biological sources.

Effects of Yb ^(3+)-Doping on Phase Transformation and Photocatalytic Activities of TiO_2 Nano-Powders

Yb 3+-doped TiO_2 composite nano-particles were prepared by the acid-catalyzed sol-gel method using Ti(OC_4H_9)_4 and Yb(NO_3)_3 as precursors. The effects of the amount of Yb 3+ doping and calcination temperature on the phase transformation, crystallite size, surface texture of the nanopowders were investigated by XRD and BET specific surface area. Their photocatalytic activities were evaluated using the photocatalytic degradation of methylene blue in aqueous solution as a probe reaction. At the interface, titanium ions substitute for ytterbium ions in the lattice of Yb_2O_3 to form Ti-O-Yb bonds, which cause distortion and inhibit the anatase to rutile phase transformation in TiO_2. The results indicate that Yb 3+-doping can enhance the photocatalytic activity of TiO_2 nano-powders as compared with pure TiO_2. 0.125%(mass fraction) Yb 3+ doped TiO_2 nano-powders calcined at 600 ℃ for 2 h show the highest photocatalytic activity. The increase in photoactivity is due to the effects of the factors such as crystal phase, crystallite size, surface chemical property, surface density of OH groups, and surface texture properties of the TiO_2 nano-powders.

Influence of current injection ways on efficiency and size of powders in preparation of nano-powders with electrical explosion

Wire electrical explosion may result in the existence of micro-sized large particles in powders while current injection ways may influence the size and content of micro-sized large particles. Therefore, two kinds of electrical explosion devices with different electrodes by gas discharge were designed in this paper. The pole-board electrodes and the cone electrodes were used respectively for studying copper wire electrical explosion process. The current and voltage data were measured with the Rogowski coil and high voltage probe. The results show that the pulverizing process of electrical explosion is more efficient when the wire electrode current density injected into the cone electrodes is approximately twice as much as the pole-board electrodes. The content of micro-sized large particles is the least among the products of the electrical explosion, when the total deposition energy of the wire prior to vaporization stage is 2. 5 times larger than that of the theoretical value of the completed vaporization.

Molybdenum Carbide Nano-Powder for Production of Mo-99 Radionuclides

At present, there are two ways to produce 99Mo in a reactor: 1) fission process—from U fission product by reaction 235U (n, f) 99Mo and 2) activation process—by radiation capture reaction 98Mo (n, γ) 99Mo. This paper presents the results of experiments performed with molybdenum carbide nano-powder to produce 99Mo. These results show the implementation of the above idea in practice.

In-depth analysis of the influence of bio-silica filler(Didymosphenia geminata frustules)on the properties of Mg matrix composites

A novel metal matrix composites(MMC)with Mg matrix reinforced with natural filler in the form of Didymosphenia geminata frustules(algae with distinctive siliceous shells)are presented in this work.Pulse plasma sintering(PPS)was used to manufacture Mg-based composites with 1,5 and 10 vol.%ceramic filler.As a reference,pure Mg was sintered.The results show that the addition of 1 vol.%Didymosphenia geminata frustules to the Mg matrix increases its corrosion resistance by supporting passivation reactions,and do not affect the morphology of L929 fibroblasts.Addition of 5 vol.%the filler does not cause cytotoxic effects,but it supports microgalvanic reactions leading to the greater corrosion rate.Higher content than 5 vol.%the filler causes significant microgalvanic corrosion,as well as increases cytotoxicity due to the greater micro-galvanic effect of the composites containing 10 and 15 vol.%diatoms.The results of contact angle measurements show the hydrophilic character of the investigated materials,with slightly increase in numerical values with addition of amount of ceramic reinforcement.The addition of Didymosphenia geminata frustules causes changes in a thermo-elastic properties such as mean apparent value of coefficient of thermal expansion(CTE)and thermal conductivity(λ).The addition of siliceous reinforcement resulted in a linear decrease of CTE and reduction in thermal conductivity over the entire temperature range.With the increasing addition of Didymosphenia geminata frustules,an increase in strength with a decrease in compressive strain is observed.In all composites an increase in microhardness was attained.The results clearly indicate that filler in the form of Didymosphenia geminata frustules may significantly change the most important properties of pure Mg,indicating its wide potential in the application of Mg-based composites with a special focus on biomedical use.

Phase field simulation of grain refinement in silver-based filler metal

Numerical simulation is one of the important auxiliary methods for studying materials-related problems. In this study, phase field simulation was employed to investigate the refinement behavior of BAg55CuZn-x B brazing alloys. Simulation and experimental studies were conducted for B contents ranging from 0 wt.% to 0.2 wt.%. The results demonstrated that the addition of 0.05 wt.% B in the brazing alloy leads to a significant refinement effect. As the B content increases, the grain size further reduces, and a refinement stagnation phenomenon occurs after exceeding 0.15 wt.%. The solidification process of brazing alloys with different B content was predicted by simulation, and the simulation results showed that with the increase of B content, the initial number of nucleation increased, and the radius of the dendrite tip decreased. The simulation results are in good agreement with the experimental findings, providing further evidence of the refining effect of the B element and the reliable predictive capability of the phase field model.

不同填料生物膜对海水养殖尾水的脱氮效能及微生物群落分析

为探究不同填料生物膜对海水养殖尾水氮污染物的处理能力,分别以无填料(C)、牡蛎壳(M)、珊瑚石(S)、弹性填料(T)和悬浮球填料(F)构建5组生物滤池,比较填料生物膜成熟时间、成膜情况及对不同氮污染物的24 h去除能力,同时利用高通量测序技术分析挂膜期间(20、40、60 d)填料生物膜上微生物群落的变化。结果表明:不同填料生物膜成熟时间需要46~50 d,珊瑚石所需时间最短(46 d);扫描电镜显示,弹性填料和悬浮球填料附着生物量最多,以杆状细菌为主;对氨氮、亚硝酸盐氮、硝酸盐氮的24 h去除率最高的填料分别是悬浮球填料(68.66%±6.27%)、珊瑚石(99.99%±0.00%)和悬浮球填料(6.73%±3.41%);高通量测序显示,随着挂膜时间延长,弹性填料生物膜上的细菌丰度显著增加,牡蛎壳和珊瑚石生物膜上的细菌多样性显著下降(P<0.05);在门分类水平上,变形菌门(Proteobacteria)、拟杆菌门(Bacteroidetes)是不同填料生物膜的主要优势菌群,硝化螺旋菌门(Nitrospirae)、硝化刺菌门(Nitrospinae)的相对丰度随挂膜时间延长不断升高;在属分类水平上,亚硝酸菌属(Nitrosomonas)、硝化螺菌属(Nitrospira)、硝化刺菌属(Nitrospina)和未分类_亚硝化单胞菌科(unclassified_Nitrosomonadaceae)是填料生物膜上具有硝化作用的优势菌属,这4种硝化菌属在挂膜60 d时的相对丰度总和从高到低依次为悬浮球填料(42.53%)>牡蛎壳(30.50%)、弹性填料(29.30%)>珊瑚石(11.74%),假单胞菌属(Pseudomonas)、青枯菌属(Ralstonia)、噬几丁质菌属(Chitinophaga)和草螺菌属(Herbaspirillum)等反硝化菌属在珊瑚石填料生物膜上的相对丰度高于其他填料。研究表明,珊瑚石、悬浮球填料能够实现脱氮菌属的高效富集,对海水养殖尾水具有良好的脱氮能力,是较为理想的生物填料。

不同助留体系对装饰原纸二氧化钛复合填料留着效果的影响

本研究分别分析了单元助留体系阳离子聚酰胺环氧氯丙烷树脂(PAE),双元助留体系PAE/阴离子聚丙烯酰胺(APAM)、PAE/膨润土(MMT)、PAE/阳离子聚丙烯酰胺(CPAM),三元助留体系PAE/CPAM/APAM、PAE/CPAM/MMT对装饰原纸TiO_(2)/滑石粉复合填料留着效果的影响。确定了各个体系的最佳添加量,并筛选出助留效果最好的助留体系。结果表明,当PAE添加量2.0%、CPAM添加量0.08%、MMT添加量0.6%时,组成的PAE/CPAM/MMT三元助留体系留着效果最佳,此时,浆料和填料留着率分别为89.5%和65.0%,纸张的不透明度、白度及匀度分别为98.5%、86.6%和91。

污水处理填料堵塞的形成机理及控制措施

污水处理填料能够提高污水处理效果,但其堵塞问题会降低处理能力、恶化运行工况,亟待解决。为提高污水处理填料的抗堵塞能力,综述了污水处理填料堵塞的相关研究,从填料特性、应用场景、物质分类、堵塞特点、发展机制和影响因素等方面总结了污水处理填料堵塞的形成机理,从事前、事中、事后三个方面讨论了针对污水处理填料堵塞问题的7项常用控制措施,并根据研究现状提出了堵塞形成机理、堵塞控制措施、填料设计优化等方面的研究建议,以期为污水处理填料及配套工艺的后续研究和技术开发提供支撑,提高污水处理填料的应用效益。

航天器用界面导热填料应用状态接触传热系数分析

为解决航天器用RKTL-DRZ-2型导热脂及RKTL-DRNJ-1型导热凝胶2种新开发导热填料无实际应用状态下接触传热系数数据的问题,采用试验方法对其接触传热系数进行研究,得到在航天器上设备典型尺寸及不同固定螺钉分布情况下的接触传热系数。试验结果表明:在相同安装状态下,与目前常用的RKTL-DRZ-1型导热脂相比,RKTL-DRZ-2型导热脂对界面接触传热性能改善效果较好,RKTL-DRNJ-1型导热凝胶较差。此外,获取了保证导热填料填充效果的实施经验,并给出了导热填料的选用建议。试验分析结论可应用于选用导热填料时的航天器热设计及热控实施。

温度影响下罗布泊盐岩路基填料变形特性研究

为探明温度影响下盐岩路基填料变形特性,保障盐岩路基稳定性,促进盐岩在路基工程中资源化应用,全面分析了卤水及盐岩相变特征,基于正交试验方法探究了单次降温多因素交互作用下盐岩填料的变形规律,系统研究了多次冻融循环后盐岩填料盐胀累积规律,并基于试验段现场监测综合评价了盐湖区盐岩路基变形特征。结果表明:不同浓度卤水降温曲线均未出现明显过冷阶段,其降温曲线平衡及波动维持时间极为短暂,同时卤水相变温度随浓度增加而升高。盐岩填料的降温曲线存在显著的过冷及温度跳跃阶段,其相变温度随拌和卤水浓度增加而下降。单次降温作用下盐岩填料变形量介于-0.09~0.18 mm,各因素对盐岩填料变形的影响顺序为:上覆荷载>含卤水率>最大粒径>压实度。冻融循环作用下拌合卤水浓度越低,盐岩填料盐胀量越大;上覆荷载对盐岩填料盐胀抑制作用较强。实体工程现场监测表明随着监测时间增长盐岩路基变形呈现正弦波式周期性变化,且变形沿深度方向呈减小趋势,同时盐岩路基变形与温度具有较强的线性相关性。

无机填料对水泥固化泥炭土强度的影响

通过无侧限抗压强度和扫描电镜试验,研究了无机填料种类和粒径对水泥固化泥炭土强度的影响.结果表明:水泥固化泥炭土强度随着石英砂掺量的增加呈先增加后降低的趋势,20%石英砂掺量下水泥固化泥炭土强度最高;当石英砂粒径d>1.0 mm时,水泥固化泥炭土强度提升有限,而当d<0.5 mm时,水泥固化泥炭土强度提升明显;高岭土颗粒可有效填充泥炭土孔隙,有利于水泥联结无机填料和泥炭土颗粒,且水泥联合高岭土固化泥炭土的强度明显优于水泥联合石英砂;当泥炭土含水率为600%,高岭土掺量从5%增至30%时,28d龄期水泥固化泥炭土强度的增幅为58.5%~116.6%.

有压热闷渣微粉对环氧涂料的性能影响

以有压热闷渣为研究对象,采用超细立式粉磨机处理有压热闷渣形成微粉,利用有压热闷渣微粉替代传统防腐填料与环氧树脂、二甲苯、正丁醇及聚酰胺形成有压热闷渣/环氧复合防腐涂料.根据《色漆和清漆摆杆阻尼试验》(GB/T 1730—2007)、《漆膜划圈试验》(GB/T 1720—2020)、《色漆和清漆耐磨性的测定旋转橡胶砂轮法》(GB/T 1768—2006)、《漆膜、腻子膜柔韧性测定法》(GB/T 1731—2020)测定涂层的硬度、附着力、耐磨性、柔韧性,《色漆和清漆耐中性盐雾性能》(GB/T 1771—2007)与《漆膜吸水率测定法》(HG/T 3344—2012)测定涂层的耐盐雾性能及吸水率.采用接触角测量仪、精密阻抗测试仪和电化学工作站测定涂层的接触角、阻抗模量和腐蚀电位.采用扫描电子显微镜、X射线荧光光谱仪、X射线衍射仪和激光粒度分析仪测试微观形貌、化学成分、矿物组成和粒度分布.研究有压热闷渣微粉对环氧复合防腐涂料涂层力学性能、防腐性能的影响,及其作用机理.结果表明有压热闷渣的主要矿物成分C_(3)S、C_(2)S、Ca(OH)_(2)、C_(2)F、RO相和f-CaO等,其具有硅酸盐特性可以提高耐久性.利用超细立式粉磨机对有压热闷渣进行加工,有利于f-CaO矿化,减小颗粒粒径、增大比表面积.当有压热闷渣微粉的粒径均匀度为2.240,其添加量为5%时有压热闷渣/环氧复合防腐涂料涂层的性能最佳,即摆杆硬度测试结果为115.75 s、附着力为3级、磨损量最小、柔韧性为4 mm、阻抗模量为10^(6.1)Ω·cm^(2)、腐蚀电位E为0.143 V.有压热闷渣微粉作为一种刚性粒子,将其加入环氧涂料体系中,一方面可以改善涂层的硬度、耐摩擦、力学等性能,另一方面合理的粒径均匀度可以增强涂层的密实度,提升防腐性能.开启有压热闷渣在非建材领域高值化利用的新途径,实现钢铁行业“以废增效”、涂料行业“以废降本”的目的.