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Theoretical and experimental study on the fluidity performance of hard-to-fluidize carbon nanotubes-based

《化学科学与工程前沿（英文）》 2022年第16卷第10期页码 1460-1475 doi: 10.1007/s11705-022-2159-x

摘要： Carbon nanotubes-based materials have been identified as promising sorbents for efficient CO₂ capture in fluidized beds, suffering from insufficient contact with CO₂ for the high-level CO₂ capture capacity. This study focuses on promoting the fluidizability of hard-to-fluidize pure and synthesized silica-coated amine-functionalized carbon nanotubes. The novel synthesized sorbent presents a superior sorption capacity of about 25 times higher than pure carbon nanotubes during 5 consecutive adsorption/regeneration cycles. The low-cost fluidizable-SiO₂ nanoparticles are used as assistant material to improve the fluidity of carbon nanotubes-based sorbents. Results reveal that a minimum amount of 7.5 and 5 wt% SiO₂ nanoparticles are required to achieve an agglomerate particulate fluidization behavior for pure and synthesized carbon nanotubes, respectively. Pure carbon nanotubes + 7.5 wt% SiO₂ and synthesized carbon nanotubes + 5 wt% SiO₂ indicates an agglomerate particulate fluidization characteristic, including the high-level bed expansion ratio, low minimum fluidization velocity (1.5 and 1.6 cm·s^–1), high Richardson−Zakin index (5.2 and 5.3 > 5), and low Π value (83.2 and 84.8 < 100, respectively). Chemical modification of carbon nanotubes causes not only enhanced CO ₂ uptake capacity but also decreases the required amount of silica additive to reach a homogeneous fluidization behavior for synthesized carbon nanotubes sorbent.

关键词： CO₂ capture CNT-based sorbents fluidization SiO₂ nanoparticles fluidized bed reactors

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Silicon carbide waste as a source of mixture materials for cement mortar

Zhengwu Jiang, Qiang Ren, Haoxin Li, Qing Chen

《环境科学与工程前沿（英文）》 2017年第11卷第5期 doi: 10.1007/s11783-017-0974-y

摘要： This paper presents an investigation of the feasibility of recycling silicon carbide waste (SCW) as a source of mixture materials in the production of cement mortar. Mortars with SCW were prepared by replacing different amounts of cement with SCW, and the properties of the resulting mortars, such as the fluidity, strength and shrinkage, were studied in this work. Thermogravimetry-differential scanning calorimetry and scanning electron microscopy were employed to understand the reasons for the property changes of the mortars. The results indicate that SCW decreases the initial and 1-h fluidity of fresh mortar but improves the loss of fluidity. The mortar with SCW exhibits a lower strength at 3 d and 7 d but a higher strength at 28 d and 56 d compared to the control. The shrinkage rate of cement mortar with SCW shows an obvious decrease as the replacement ratio increases. In addition, the content of calcium hydroxide in hardened paste also shows that SCW has some impact on the hydration of the cement-SCW system. The microstructures of the hardened paste also show evidence for a later strength change of mortar containing SCW. This work provides a strategic reference for possibly applying SCW as a mixture material in the production of cement mortar.

关键词： Silicon carbide waste Cement mortar Fluidity Strength Shrinkage

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浇筑式沥青混凝土性能影响因素研究

王宏畅,李国芬,章登精

《中国工程科学》 2013年第15卷第8期页码 70-74

摘要：

浇筑式沥青混凝土具有较高的变形随从性而在钢桥面铺装上得到了很多的应用，为研究浇筑式沥青混凝土的性能影响因素，采用4种合成级配、3种沥青用量，系统评价了各因素对浇筑式沥青混凝土性能的影响。通过流动度试验和贯入度试验确定最佳含油量，由高温车辙试验和低温弯曲试验进行路用性能检验。研究表明，级配形式和沥青含油量变化对混合料的性能指标的影响较大，因此，实际施工时应严格控制混合料的级配和沥青用量。

关键词：道路工程钢桥面铺装浇筑沥青混凝土流动度贯入度车辙

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Effect of nonionic side chain length of polycarboxylate-ether-based high-range water-reducing admixture on properties of cementitious systems

Süleyman ÖZEN, Muhammet Gökhan ALTUN, Ali MARDANI-AGHABAGLOU, Kambiz RAMYAR

《结构与土木工程前沿（英文）》 2020年第14卷第6期页码 1573-1582 doi: 10.1007/s11709-020-0680-x

摘要： Despite the large variations in the behaviors of water-reducing admixtures upon changes in their structures, most previous reports on the cement-admixture compatibility did not provide sufficient information on the structure of the admixture. Hence, the evaluation and generalization of the reports on the cement-admixture compatibility are challenging. In this study, three different polycarboxylate-ether-based water-reducing admixtures with the same free nonionic content, anionic/nonionic molar ratio, and main chain length and different side chain lengths were produced. The compatibility of these admixtures with a CEM I 42.5R-type cement was investigated. In addition, an analysis of variance was performed on the experiment results to evaluate the contributions of the admixture type, admixture/cement ratio, and elapsing time to the Marsh funnel flow time, mini-slump, slump flow, and compressive strength. The water-reducing admixtures having long or short side chains reduced the initial flow characteristics of the cementitious systems. However, the admixture having the shortest side chain was better with regard to flow retention. The side chain length of the admixture did not have significant effects on the compressive strength and water absorption capacity of the mortar mixtures and mini-slump performances of the cement paste mixtures. Regarding the behaviors of the admixtures in the cementitious systems, an optimal admixture side chain molecular weight is proposed.

关键词： water-reducing admixture side chain length cement paste fluidity compressive strength