Predetermination of potential plastic hinges on reinforced concrete frames using GFRP reinforcement

In the past, glass fiber-reinforced polymer (GFRP)-reinforcement has been successfully applied in reinforced concrete (RC) structures where corrosion resistance, electromagnetic neutrality, or cuttability were required. Previous investigations suggest that the application of GFRP in RC structures could be advantageous in areas with seismic activity due to their high deformability and strength. However, especially the low modulus of elasticity of GFRP limited its wide application as GFRP-reinforced members usually exhibit considerably larger deformations under service loads than comparable steel-reinforced elements. To overcome the aforementioned issues, the combination of steel and GFRP reinforcement in hybrid RC sections has been investigated in the past. Based on this idea, this paper presents a novel concept for the predetermination of potential plastic hinges in RC frames using GFRP reinforcement. To analyze the efficiency of the concept, nonlinear finite element simulations were performed. The results underscore the high efficiency of hybrid steel-GFRP RC sections for predetermining potential plastic hinges on RC frames. The results also indicate that the overall seismic behavior of RC structures could be improved by means of GFRP as both the column base shear force during the seismic activity as well as the plastic deformations after the earthquake were considerably less pronounced than in the steel-reinforced reference structure.     

Enhanced UV- and visible-light driven photocatalytic performances and recycling properties of graphene oxide/ZnO hybrid layers

Light induced catalytic processes have attracted significant attention during the last years for wastewater treatment due to their efficiency in decomposition of organic contaminants. In this study we report the synthesis of graphene oxide (GO)/ZnO hybrid layers with high photocatalytic efficiency using laser radiation. The results show that the hybrid layers exhibit much improved photodecomposition efficiency as compared to pure GO or ZnO both under UV and visible-light irradiation. The enhanced photocatalytic efficiency of the hybrid as compared to the reference pure ZnO and GO layers was attributed to the contribution of GO to the separation and transport of the photogenerated charge carriers. Additionally, under visible light irradiation the organic molecules can act as first sensitizers in the degradation process. The recyclability of the layers was also investigated through repetitive photodegradation cycles under UV- or visible-light irradiation. After consecutive degradation runs, the hybrid photocatalyst layers were still stable and retained high degradation efficiency, ensuring reusability. The photocatalytic activity of the layers was correlated with the gradual change of their chemical structure during consecutive degradation cycles. Owing to the high photodegradation efficiency, reusability, and ease of recovery the synthesised hybrid layers consisting of easily available materials are suitable for environmental purification applications.     

Hyperbranched Polyethylenimine Modified Waste Fiberboard Activated Carbon for Enhanced Adsorption of Hexavalent Chromium

The objective of this work is to prepare a hyperbranched polyethylenimine (HBPEI) grafted activated carbon obtained from waste fiberboard for effectively removing Cr(VI) from aqueous solution. The waste fiberboard activated carbon (WFAC) was modified by HBPEI and cross-linked with glutaraldehyde (GA). The optimal modified conditions were as follows: HBPEI molecular weight 10,000 g/mol, HBPEI/WFAC (w/w) 0.5, GA concentration 0.25%, reaction time 60 min. Both pristine WFAC and HBPEI–WFAC were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), Scanning electronic microscopy (SEM), and Roman spectra. XPS data showed the obvious increase in nitrogen (from 0.72% to 6.65%) after modification. The results of FTIR and XPS suggested that HBPEI was chemically bonded onto the WFAC by the glutaraldehyde (GA) between the amine groups of WFAC and that of HBPEI. HBPEI was also probably grafted onto WFAC through the intermolecular interaction between the carboxylate groups of WFAC and the amine groups of HBPEI. However, the BET surface area of modified WFAC declined slightly (about 200 m²/g). The I_D/I_G of modified WFAC decreased from 0.92 to 0.82, which indicated that the modification process had no significant effect on the graphitization of activated carbon. The adsorption property onto HBPEI–WFAC and the factors containing contact time, pH value, and Cr(VI) concentration were also investigated. Analysis of the Cr(VI) adsorption data was well simulated by the pseudo-second-order kinetic model and Langmuir adsorption isotherm model, and maximum Cr(VI) uptake of HBPEI–WFAC was 500 mg/g.     

Surface sedimentation and adherence of Nano‐SiO2 to improve thermal stability and flame resistance of melamine‐formaldehyde foam via sol‐gel method

Melamine‐formaldehyde foam possesses intrinsic flame retardance; however, relative poor thermal stability and a certain amount of heat release rate restrict its applications in heated environment to a degree. In the present research, sol‐gel method has been adopted to precipitate nano‐SiO₂ particles on the surface of the melamine‐formaldehyde foam's fibers to construct a protective inorganic gel layer. Taking advantages of the shielding effects of the gel layer, the thermal‐oxygen degradation of the foam can be greatly retarded during heating; hence, the thermal stability is remarkably improved, and the flame retardance is further enhanced. In addition, introducing a small amount of membrane‐forming agent in the sol‐gel system can make the depositional nano‐SiO₂ particles well adhered to avoid dusting.     

Post‐polymerization modification of bio‐based polymers: maximizing the high functionality of polymers derived from biomass

The renaissance of the bio‐based chemical industry over the last 20 years has seen an ever growing interest in the synthesis of new bio‐based polymers. The building blocks of these new polymers, so called platform molecules, contain significantly more chemical functionality than their petrochemical counterparts (such as ethene, propene and para‐xylene). As a result bio‐based polymers often contain greater residual chemical functionality in their chains, with groups such as alkenes and hydroxyls commonly observed. These functional groups can act as sites for post‐polymerization modification (PPM), thus further extending the range of applications for bio‐based polymers by tailoring the polymers' final properties. This mini‐review highlights some of the most recent and compelling examples of how to make use of bio‐based polymers with residual functional groups for PPM. It also looks at how the emerging interdisciplinary field of enzymatic polymer synthesis allows for increased functionality in polymers by avoiding side‐reactions as a result of milder reaction conditions, and additionally offers an alternative means of polymer surface modification. © 2018 Society of Chemical Industry     

丝网印刷法制备Y改性CuMn2O4尖晶石涂层研究

目的 提高SOFC金属连接件CuMn2O4尖晶石涂层高温抗氧化性能和导电性能。方法 采用溶胶-凝胶法制备Y改性CuMn2O4尖晶石粉末，采用丝网印刷技术在SUS430合金表面制备Y改性CuMn2O4尖晶石涂层。利用XRD、SEM表征Y改性CuMn2O4尖晶石粉体及涂层的物相结构及微观形貌。利用氧化增重实验研究Y改性前后CuMn2O4尖晶石涂层试样在800 ℃空气中氧化168 h的高温氧化行为，通过“四点法”测量涂层在高温氧化过程中的面比电阻值。结果 CuMn2O4尖晶石粉末的晶格常数随着稀土Y含量的增大而增大，当Y元素的含量为0.02 mol/L时，晶格常数增幅趋于平缓，此时所得粉体物相结构稳定，结晶程度较好，晶粒尺寸细小且颗粒间团聚现象较少。Y改性前后CuMn2O4尖晶石涂层试样的氧化动力学曲线均遵循抛物线氧化定律，其氧化速率常数分别为9.39×10-5、6.31×10-5 mg2/(cm4?h)。Y改性CuMn2O4尖晶石涂层试样在800 ℃氧化168 h时的面比电阻值约为26.2 m??cm2，低于未改性涂层试样的面比电阻值（约27.3 m??cm2）。结论 Y改性CuMn2O4尖晶石涂层能有效改善金属连接体的高温抗氧化性能和导电性能。     

细化变质处理对铸造A356铝合金组织性能及共晶硅生长机制的影响

研究了采用新型Al-5Ti-1B-1RE中间合金和Al-10Sr中间合金对A356铝合金进行单一或复合细化变质处理后的组织、力学性能和共晶硅生长机制的影响。结果表明：单一细化变质处理中Al-5Ti-1B-1RE中间合金对A356铝合金中α-Al相有明显的细化作用,合金的强度和维氏硬度显著提高；Al-10Sr 中间合金对共晶硅有强的变质作用,合金的伸长率明显提高；而经复合细化变质处理后α-Al相形状和尺寸变得更均匀细小,晶界更清晰,共晶硅相几乎都转变成更弥散、更细小的纤维状,片层状共晶硅也几乎完全消失,共晶硅长度由铸态40-60 μm降低到1-2 μm之间,达到完全变质效果,其力学性能显著高于铸态、单一细化变质剂处理的A356铝合金。未细化变质的A356铝合金中的共晶Si的生长方式为典型的小平面台阶生长,复合细化变质处理的共晶硅以孪晶凹槽机制生长为主,小平面生长特征逐渐减弱直至消失。     

Influence of Al addition on microstructures of Cu−B alloys and Cu−ZrB2 composites

The influence of Al addition on the microstructure of Cu−B alloys and Cu−ZrB₂ composites was investigated using scanning electron microscopy, X-ray diffraction and first-principles calculation. The results show that the eutectic B in Cu−B alloys can be modified by Al from coarse needles to fine fibrous structure and primary B will form in hypoeutectic Cu−B alloys. As for Cu−ZrB₂ composites, Al can significantly refine and modify the morphology of ZrB₂ as well as improve its distribution, which should be due to its selective adsorption on ZrB₂ surfaces. The first-principles calculation results indicate that Al is preferentially adsobed on ZrB₂ (12(__)10), then on ZrB₂ (101(__)0), and finally on ZrB₂ (0001). As a result, smaller sized ZrB₂ with a polyhedron-like, even nearly sphere-like morphology, can form. Due to Al addition, the hardness of Cu−ZrB₂ composites is greatly enhanced, but the electrical conductivity of the composites is seriously reduced.     

煤尘组分对瓦斯/煤尘复合爆炸下限的影响研究

瓦斯和煤尘复合爆炸是煤矿井下爆炸灾害的主要形式之一,研究瓦斯/煤尘复合爆炸下限变化规律,是有效防治煤矿爆炸灾害的必备条件。为研究煤尘组分对瓦斯/煤尘复合爆炸下限的影响,特选用2种组分不同的煤尘(烟煤和无烟煤)。依据EN 14034标准,使用10 kJ化学点火头在标准20L球形爆炸容器中,分别对2种煤尘的最小爆炸浓度、相同试验条件下的瓦斯爆炸下限以及煤尘与瓦斯的复合爆炸下限进行了测量。试验测得烟煤和无烟煤的最小爆炸浓度分别为50 g/m^3和70 g/m^3,瓦斯爆炸下限为4%。当煤尘中分别通入1%、2%、3%、4%的瓦斯后,烟煤最小爆炸浓度分别降低至40、20、5、0 g/m^3,无烟煤最小爆炸浓度分别降低至50、20、5、0 g/m^3。基于上述测量结果,对比分析了煤尘组分对瓦斯/煤尘复合爆炸下限变化规律的影响,并探讨了Le Chatelier、Bartknecht、Jiang等气粉复合爆炸下限预测模型对瓦斯/煤尘复合体系的适用性。结果表明:2种煤尘的最小爆炸浓度均随瓦斯浓度的增大而降低,但挥发分含量低的煤尘降幅更大,即瓦斯对低挥发分煤尘最小爆炸浓度的影响更为显著。Jiang模型预测值远远偏离实际测量值;Le Chatelier模型预测值高于实际测量值,且误差随瓦斯浓度的增大而增大;Bartknecht模型适用性相对较好,且更适用于低挥发分瓦斯/煤尘复合体系。