Adsorption and Desorption Mechanisms of Methylene Blue Removal with Iron-Oxide Coated Porous Ceramic Filter

Adsorption and desorption mechanisms of methylene blue (MB) removal with iron-oxide coated porous ce-ramics filter (IOCPCF) were investigated in batch and column mode. The results revealed that MB removal mechanisms included physical adsorption and chemical adsorption, of which chemical adsorption by surface ligand complex reaction played a dominant role after infrared spectrum analysis. Recycling agents were se-lected from dilute nitric acid (pH=3), sodium hydroxide solution (pH=12) and distilled water. Among three agents, dilute metric acid (pH=3) was the best recycling agent. Regeneration rate of IOCPCF arrived at 82.56% at batch adsorption and regeneration was finished in 75min at column adsorption. Adsorp-tion-desorption cycles of IOCPCF after batch and column adsorption were four and three times, respectively. Further, compared with fresh IOCPCF, MB removal rate with these desorbed IOCPCF adsorption only slightly decreased, which suggested that IOCPCF should be used repeatedly.

Effects of laser energy density on forming accuracy and tensile strength of selective laser sintering resin coated sands

Baozhu sand particles with size between 75 μm and 150 μm were coated by resin with the ratio of 1.5 wt.% of sands. Laser sintering experiments were carried out to investigate the effects of laser energy density(E = P/v), with different laser power(P) and scanning velocity(v), on the dimensional accuracy and tensile strength of sintered parts. The experimental results indicate that with the constant scanning velocity, the tensile strength of sintered samples increases with an increase in laser energy density; while the dimensional accuracy apparently decreases when the laser energy density is larger than 0.032 J·mm-2. When the laser energy density is 0.024 J·mm-2, the tensile strength shows no obvious change; but when the laser energy density is larger than 0.024 J·mm-2, the sample strength is featured by the initial increase and subsequent decrease with simultaneous increase of both laser power and scanning velocity. In this study, the optimal energy density range for laser sintering is 0.024-0.032 J·mm-2. Moreover, samples with the best tensile strength and dimensional accuracy can be obtained when P = 30-40 W and v = 1.5-2.0 m·s-1. Using the optimized laser energy density, laser power and scanning speed, a complex coated sand mould with clear contour and excellent forming accuracy has been successfully fabricated.

Influence of resin flow on shrinkage of additive manufacturing coated sand molds

Coated sands are used extensively for additive manufacturing sand molds in the metal casting process, and the packing structure changes caused by the resin flow promote the shrinkage and deformation of the part. During the coated sand heating, the resin on the surface flowing to the contact points of the particles forms the resin neck and causes particles to pack close to each other. In this work, the diameters of the coated ceramsite sand before and after heating were measured based on in-situ experimental observations with image measuring apparatus and blue laser, to obtain the relationship between resin coating thickness and the particle diameter. The particle packing model was established to describe the particles＇ achievement of a stable state one by one. A re-packing simulation was then performed after reducing the particle diameter according to the resin coating thickness, to obtain the shrinkage ratios at different particle size distributions. It was found that the resin coating thickness increased from 0.8 to 2.3 IJm as the particle diameter increased from 107 to 500 IJm, for the coated ceramsite sand with the resin content of 2wt.%; the shrinkage ratio decreased first and then increased as the particle diameter increased. The experimental minimum shrinkage ratio was 3.28%, and the corresponding particle diameter was 300-375 IJm, while the minimum shrinkage ratio obtained by simulation was 3.43%, and the corresponding particle diameter was 214-300 IJm. After mixing the five groups proportionally, the shrinkage ratios of the simulation and experiment dropped to 2.81% and 3.04%, respectively, indicating the best results.

Carbon coated sand filtration

The goal of this work is to determine the removal efficiency of pathogen by using carbon coated sand filter.For the bacterial research,serial dilution and agar plate methods are used,E.coli is used as bacterial indicator and the experiments are operated under four different conditions:different HRTs,different sand:bran ratios,different carbon sources and different sand types.As a result the treatment efficiency of bacteria is too much less than the slow sand filtration.It’s not suitable for bacteria removal.Although its treatment efficiency is less than the advanced methods,it is a low-tech system which can be easily built up and it is very economic.

Preparation of coated sand for selective laser sintering and optimization of baking process of sand moulds

A cold method was used to prepare coated sand for application in the selective laser sintering(SLS)process.Tensile strength,loss on ignition,gas evolution,and accuracy of the SLS samples were tested and analyzed,and the baking process was thoroughly investigated.Compared with coated sand prepared by the hot method,the cold method yields a more uniform and complete resin film on the sand's surface,resulting in enhanced tensile strength and accuracy.Additionally,the cold method requires a lower binder content to meet the same strength requirements,thereby minimizing gas evolution,reducing porosity defects,and ultimately improving casting quality.The coated sand samples prepared through the cold method exhibit superior accuracy,with a size error of within±0.4 mm.In contrast,the coated sand samples prepared by the hot method display a lower accuracy,with an average negative error of 2.1993 mm.The highest tensile strength could be attained by controlling the baking temperature within a suitable range(180-190°C),which can effectively reduce the generation of gas,thus contributing to improved overall performance.

Freeze-Thaw Effect on Coarse Sand Coated Interface between FRP and Concrete

This paper examines the effect of freezing and thawing on the coarse sand coating chosen to achieve the composition of FRP and concrete in FRP-concrete composite deck. Push-out test specimens with dimensions of 100 × 100 × 450 mm were subjected to repeated freeze-thaw cycles under wet conditions ranging from -18℃± 2℃ to 4℃ ± 2℃. The failure strength of the interface and the deformation of FRP at failure exhibited by the specimens that experienced 300 freezing-thawing cycles showed a difference of merely 5% compared to those of the specimens that were not subjected to freeze-thaw. This indicates that coarse sand coating is not affected by freezing-thawing cycles and the FRP-concrete composite deck owns sufficient applicability in terms of durability against freezing-thawing.

Adsorption of Fluoride from Water Using Aluminum Coated Sand: Kinetics, Equilibrium, Effect of pH, and Coexisting Ions

An aluminum coated sand (AlCS) was evaluated as a metal oxide adsorbent for adsorption and removal of fluoride from water using a low-cost adsorbent with potential application in continuous flow adsorber systems. Surface characterization of the AlCS sorbent was performed using TEM, SEM/EDX, XRD and BET. The AlCS sorbent contained mostly amorphous aluminum oxides based on adsorbent characterization results. Favorable adsorption of fluoride onto the AlCS sorbent occurred according to the Langmuir and Freundlich adsorption equations, while physical adsorption of fluoride onto the AlCS sorbent was observed based on results from the Dubinin-Radushkevich equation. Fluoride adsorption onto the AlCS sorbent followed pseudo-second order kinetics, while surface charge analysis indicated a pHPZC of 7.1 for the AlCS sorbent. Effective fluoride removal occurred over a broad pH range from 3 to 11 with a maximum fluoride removal observed at pH 4 to 5. The effect of co-existing ions in water resulted in a decrease in fluoride uptake in the presence of bicarbonate, while resulting in an increase in fluoride uptake in the presence of calcium. The AlCS sorbent was a low-cost and sustainable adsorbent for effective adsorption and rapid removal of fluoride from water within an hour.

Coating process of multi-material composite sand mold 3D printing

Sand mold 3 D printing technology is an advanced manufacturing technology which has great flexible manufacturing ability. A multi-material composite sand mold can control the temperature field of metallic parts during the pouring process, while the current sand mold 3 D printing technology can only fabricate a single material sand mold. The casting temperature field can not be adjusted by using single sand mold material with isotropous heat exchange ability during the pouring process. In this work, a kind of novel coating device was designed. Multi-material composite sand molds could be manufactured using the coating device according to the casting process demands of the final parts. The influences of curing agent content, coating velocity and scraper shape on compactness and surface roughness of the sand layer(silica sand and zircon sand) were studied. The shapes and sizes of transition intervals of two kinds of sand granules were also tested. The results show that, with the increase of the added volume of curing agent, the compactness of sand layer reduces and the surface roughness value rises. With the increase of the velocity of the coating device, the compactness of sand layer reduces and the surface roughness value rises similarly. In addition, the scraper with a dip angle of 72 degrees could increase the compactness value of the sand layer. The criteria of quality parmeters of the coating procedure are obtained. That is, the surface roughness(δ) of sand layer should be equal to or lesser than half of main size of the sand particles(Dm). The parameter H of the coating device which is the distance between the base of hopper and the surface of sand layer impacts the size of transition zone. The width of the transition zone is in direct proportion to the parameter H, qualitatively. Through the optimization of the coating device, high quality of multi-material sand layers can be obtained. This will provide a solution in manufacturing the multi-material composite sand mold.

Wear behavior of high velocity arc sprayed 3Cr13 steel coating in oil containing sand

To improve the wear resistance of the machine components serving in desert areas, the 3Cr13 stainless steel coating was produced by the high velocity arc spraying technique. The microstructure and phase constitute of the coating were analyzed by SEM and XRD. The effects of sand content on the friction and wear behaviors of the coating under the lubrication of oil containing sand were investigated on a ball-on-disk tester. SEM was used to reveal the wear mechanisms of the coating. The results show that the wear volume increases with increasing the sand content in the oil, and the sprayed coating exhibits better triobological properties compared with the 1045 steel. The predominant wear mechanisms of the sprayed coating are micro-cutting, brittle fracture and delamination.

Sand-wear resistance of brush electroplated nanocomposite coating in oil and its application to remanufacturing

Sand-wear resistance of nano scale alumina particle reinforced nickel matrix composite coating （n-Al2O3/Ni） prepared by brush electroplating technique was investigated via wear tests in sand-contaminated oil lubricant, comparing with that of AISI1045 steel and brush electroplated Ni coating. Effects of testing load, sand content and sand size on worn volume of the three materials, and also coating surface roughness on worn volume of the brush electroplated coatings were accessed. Results show that the worn volume of all the three materials increases with increasing of testing load, sand content and sand size. In the same conditions, n-Al2O3/Ni composite coating has the smallest worn volume while AISI1045 steel has the largest because of the n-Al2O3 particle effects. As to n-Al2O3/Ni and Ni coatings, the surface-polished coatings have obviously lower worn volume than the as-plated coatings. The brush electroplated n-Al2O3/Ni composite coating was employed to remanufacture the sand-worn bearing seats of a heavy vehicle and good results were gained.

Effects of surface roughness of substrate on properties of Ti/TiN/Zr/ZrN multilayer coatings

Ti/TiN/Zr/ZrN multilayer coatings were deposited on Cr_17Ni_2 steel substrates with different surface roughnesses by vacuum cathodic arc deposition method. Microstructure, micro-hardness, adhesion strength and cross-sectional morphology of the obtained multilayer coatings were investigated. The results show that the Vickers hardness of Ti/TiN/Zr/ZrN multilayer coating, with a film thickness of 11.37 μm, is 29.36 GPa. The erosion and salt spray resistance performance of Cr_17Ni_2 steel substrates can be evidently improved by Ti/TiN/Zr/ZrN multilayer coating. The surface roughness of Cr_17Ni_2 steel substrates plays an important role in determining the mechanical and erosion performances of Ti/TiN/Zr/ZrN multilayer coatings. Overall, a low value of the surface roughness of substrates corresponds to an improved performance of erosion and salt spray resistance of multilayer coatings. The optimized performance of Ti/TiN/Zr/ZrN multilayer coatings can be achieved provided that the surface roughness of Cr_17Ni_2 steel substrates is lower than 0.4μm.

Iron casting skin management in no-bake mould – Effects of magnesium residual level and mould coating

The relative performance of coatings for furan resin sand moulds [P-toluol sulphonic acid(PTSA) as hardener] [FRS-PTSA moulds], was compared by analyzing the surface layer for degenerated graphite in Mg treated iron with 0.020 wt.% to 0.054 wt.% Mgres. It was found that the iron nodularising potential(Mg, Ce, La content) and whether the mould coatings contained S, or were capable of desulphurizing were important factors. These moulds have S in the PTSA binder, which aggravates graphite degeneration in the surface layer, depending strongly on the Mgres with lower Mgres increasing the layer thickness. The application of a mould coating strongly influenced graphite deterioration in the surface layer of castings. It either promoted graphite degeneration to less compact morphologies when using S-bearing coatings, or conversely, limited the surface layer thickness using desulphurization type coatings. Independently of the S-source at the metal – mould interface, the presence of sulphur had an adverse effect on graphite quality at the surface of Mg-treated irons, but its negative effect could also reach the graphite phase within the casting section. If the coatings employed desulphurization materials, such as Mg O, or a mixture(Ca O + Mg O + Talc) or Mgbearing Fe Si, they protected the graphite shape, improving graphite nodularity, at the metal – mould interface, and so decreased the average layer thickness in FRS-PTSA moulds. Fe Si Mg was highly efficient in minimizing the casting skin by improving graphite nodularity. It is presumed that the Mg O or(Mg O + Ca O + Talc) based coatings acted to remove any S released by the mould media. The Mg-Fe Si coatings also reacted with S from the mould but additionally supplemented the Mg nodularising potential prior to solidification. This dual activity is achievable with coatings containing active magnesium derived from fine Mg-Fe Si materials.

不同支撑剂组合方式下页岩导流能力实验评价

为了深入了解多粒径支撑剂组合条件下页岩储层导流能力的大小,依据达西定律,采用API支撑剂实验装置,评价分析不同支撑剂质量比例、粒径、铺砂浓度、类型、流体类型、岩性等对导流能力的影响。实验结果表明:随着闭合压力增加,各种支撑剂组合方式下的导流能力都有很大程度下降;相同条件下,铺砂浓度与导流能力呈正相关关系,覆膜砂的导流能力高于石英砂,清水条件下的导流能力高于破胶液,硬度高的页岩储层导流能力高于硬度低的页岩储层;70/140目陶粒+40/70目覆膜砂+30/50目覆膜砂支撑剂组合,在质量比为1∶6∶3时导流能力最优;在高闭合压力下,70/140目陶粒+40/70目覆膜砂+30/50目覆膜砂组合的导流能力,略高于70/140目陶粒+30/50目覆膜砂+20/40目覆膜砂支撑剂组合。可见,对于较软地层采用覆膜砂组合支撑剂,更有利于长期保持较高的导流能力;压裂液选用时更要注重压裂液配方的低伤害性,以提高导流能力。

内河水沙冲蚀条件下港口钢构件涂层损伤劣化的图像识别方法

为探究内河港口码头钢构件在水沙冲蚀条件下防腐涂层的损伤劣化规律,通过自制的水沙加速冲蚀磨损装置开展不同冲蚀条件下涂层材料损伤劣化的试验研究,基于图像识别技术对冲蚀损伤后的涂层表面形貌进行数字化和二值化特征提取,设定区分像素孔隙的灰度阈值,用以定量分析涂层表面破坏形式和损伤劣化面积。结果表明:当来流角度呈45°时,涂层损伤劣化最严重且表面凹坑比和划痕比大致相同,涂层损伤劣化面积随来流速度的增大呈指数扩大趋势;当含沙量低于45 kg/m^(3)时,含沙量的增大对涂层损伤劣化有促进作用,但当超过45 kg/m^(3)后反而降低了涂层损伤劣化速率,实现了在无损情况下对内河水沙冲蚀条件下钢构件涂层的损伤劣化规律分析。

涂膜、腻子膜打磨性测定仪校准方法的研究

研究建立了涂膜、腻子膜打磨性测定仪的校准方法。通过对生产厂家和用户的调研,参考相关的国家标准和校准规范,提出一种采用电子秒表、钢直尺、电子天平作为校准设备,校准涂膜、腻子膜打磨性测定仪的摩擦速度示值误差、摩擦行程、打磨头质量、附加砝码质量的方法。选择代表性的涂膜、腻子膜打磨性测定仪,依据该校准方法对计量特性进行实验验证,验证结果符合指标要求。该方法促进了涂膜、腻子膜打磨性测定仪量值溯源的标准化和规范化,推动其校准规范的制定。

基于沥青砂涂层设计的沥青混凝土路面抗紫外光老化性能分析

针对沥青路面光老化问题,参照含砂雾封层技术原理,基于沥青抗紫外光添加剂最优组合,制备含砂沥青涂层,开展不同级配和厚度的沥青砂涂层试验研究,通过沥青混凝土高低温性能试验和抗滑性能试验分析含砂涂层设计下沥青混凝土路面抗光老化性能,结果表明:涂层设计下沥青路面老化前后抗滑性能降低,但是相比于无涂层时老化后降低幅度变小且仍满足规范要求,在不考虑抗滑损失的情况下,可选择使用;老化后高低温路用性能试验说明增加路表面密实度可以提高抗光老化能力,但是涂层厚度不宜过厚,以基本完全填充混凝土表面空隙最好,建议理论厚度2 mm,要重点考虑细料涂层的级配设计,适当提高沥青砂中较大粒径的比例对封层设计效果会更好。

复杂内腔铝合金件液态模锻试验研究

目的为拓宽液态模锻技术的应用范围,实现具有复杂内腔结构件的高性能短流程成形制造,开展了使用砂芯的液态模锻技术试验研究。方法以具有复杂内腔的新能源汽车铝合金空气弹簧顶座为对象,利用广州和德装备制造公司生产的卧式液态模锻机,对比研究不同砂芯、涂料及液锻加压制度对黏砂缺陷的影响作用。结果普通砂芯在液锻中容易被压溃或产生黏砂缺陷;在苏铸砂芯的基础上自行配制HDSC01液锻砂芯,配合HDCoating03专用涂料,采用阶梯加压方法进行液态模锻,所得液锻件内表面光洁无黏砂、尺寸精确。结论液态模锻可以使用砂芯进行复杂内腔结构件的高性能精密成形,但工艺控制不当,容易出现黏砂缺陷。阶梯加压、使用专用砂芯和专用涂料是防止黏砂的有效途径。

水基涂料涂覆工艺对3D打印砂型表面质量影响的研究

以涂料波美度、单次浸涂时间、浸涂次数等工艺参数为影响因素,设计了水基涂料浸涂正交试验,研究了以上因素对3D打印砂型表面粗糙度、涂料层厚度以及涂料层厚度均匀度的影响,得到水基涂料浸涂最佳工艺。采用该工艺,涂层表面粗糙度可以达到Ra3.2~Ra6.3,涂层厚度0.3~0.35 mm,且涂层均匀度好。实际验证铸件表面粗糙度可以达到Ra6.3。

考虑静荷载与环境耦合作用的钢结构涂层劣化实验研究

为研究钢结构涂层在静荷载与大温差、风沙侵蚀作用下的劣化性能,设计了钢结构涂层的静荷载加载系统;以钢桥常见的普通型和长效型体系为对象,通过静力加载与温差控制、气流挟沙喷射法开展实验研究。采用拉开法测试了静荷载与大温差耦合作用下涂层的劣化情况,并对涂层的附着、内聚破坏模式进行定量化测试;结合拉开法及厚度测试结果,得到了涂层抗力的动态劣化过程;采用气流挟沙喷射法研究了静荷载与大温差作用下涂层的耐冲蚀性能,综合实验结果,得到涂层在静荷载与环境耦合作用下工作性能的退化过程。研究结果表明:静荷载与环境耦合作用使面漆抗力衰减至防护功能破坏后,大温差导致涂层材料向脆性转变,静荷载加速涂层的劣化,风沙冲蚀作用造成涂层从体系剥离;耦合作用下体系的抗力快速衰减,涂层逐次退出工作,涂装体系完全丧失抗力,最终从基材上剥离。对于实验涂装体系,经历30 d静荷载与大温差作用后,涂层附着力最大降低8.97%,厚度、冲蚀量、临界冲蚀角最大分别增加25.3%、46.15%、17.4%。