Preparation and characterization of eco-friendly and low-cost mullite-corundum foamed ceramics with low thermal conductivity

Mullite-corundum foamed ceramics were prepared by direct-foaming method using white clay and industrial alumina as raw materials, and calcium aluminate cement (CAC) as the binder. Effects of the calcium aluminate cement content on the phase compositions, microstructures and properties of the foamed ceramics were investigated through X-ray diffractometer (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), etc. The results showed that with increasing the calcium aluminate cement content from 0 wt% to 8 wt%, the viscosities of the initial slurries decreased, the porosities of the samples improved, the thermal conductivities decreased, and the compressive strengths increased first and then decreased. The optimized sample with 4.0 wt% CAC content had a high porosity of 80.8%, a low bulk density of 0.56 g/cm³ and a low thermal conductivity of 0.232 W/(m·K) (800 °C). On the foundation of research results, the Gong equation (GE model) and a modified GE model were used to predict the thermal conductivity at 200 °C and 800 °C of the mullite-corundum foamed ceramics with different pore characteristics and phase compositions, respectively.     

Environment-oriented low-cost Al2O3 ceramics with hierarchical pore structure fabricated from SiC solid waste

Environment-oriented low-cost Al₂O₃ reticulated porous ceramics with hierarchical pore structure were fabricated by the polymer sponge replica method combined with vacuum infiltration methods, using Al₂O₃ powders and SiC solid waste (SCSW) as raw material and a pore-forming agent. The effects of SCSW addition amount on mechanical properties, microstructure and pore size of Ceramics were investigated. The results showed that the thermal shock resistance of specimens increased gradually with addition of SCSW, however, the median pore diameter increased firstly and then decreased, due to the generation of mullite and liquid phase. After calcination, the residual stress was generated within the coating layer because of the difference in the thermal expansion coefficients of ceramic matrix and coating layer, which could improve the properties of Ceramics by deflecting and bifurcating crack growth path. The results showed that the best dosage of SCSW was 30 wt%.     

回收塑料的重新稳定化

高价值的应用是取得塑料回收在经济上成功的关键。部分应用实例说明聚烯烃的重新稳定化所带来的特点和益处及在PET回收中的产品升级的可能性，其中具体说明对材料的性能和长效性能的影响。     

平板膜MBR

文章介绍平板膜MBR在污水处理过程中的应用,包括平板膜的结构,主要参数,过滤机理及污染机理,平板膜MBR的优势、污染机理、污染防治方法及发展前景。通过全方位研究来表明平板膜MBR在污水处理比中空纤维膜MBR所具有的更优质的性能和更好的处理效果。     

复合式膜生物反应器处理制药废水的研究

对一体式与复合式膜生物反应器（MBR）处理化学合成类制药废水的厌氧反应器出水的效果进行对比研究,结果表明：在对COD和NH3-N的去除效果上,两种型式的MBR差别不大,均能保持98%和94%的高去除率,复合式MBR对总氮（TN）的去除效果高于一体式MBR,而对于总磷（TP）两种型式MBR的去除效果均不理想。     

复合式MBR与改进式MBR处理造纸废水的研究

改进式MBR和复合式IVIBR装置,在pH为 6.5～8.5、HRT为10 h、温度为29℃的条件下,稳定运行近1个月,复合式MBR的平均出水水质分别为COD 110.17mg/L、BOD510.94mg/L、色度52倍;改进式IVlBR的平均出水水质分别为COD 126.75 mg/L、BOD 518.34 mg/L、色度6l倍,略差于复合式MBR.通过上清液分析发现,主要是因为复合式MBR中的膜组件上凝胶层起了更大的拦截作用.另一方面,阻力分布试验也表明,由于浓差极化和膜污染产生的阻力,复合式MBR大约是膜自身阻力的35.23倍,改进式MBR仅是膜自身阻力的6.36倍,说明复合式MBR更易引起膜污染.     

Phase-pure iron pyrite nanocrystals for low-cost photodetectors

Earth-abundant iron pyrite (FeS₂) shows great potential as a light absorber for solar cells and photodetectors due to their high absorption coefficient (>10⁵ cm^-1). In this paper, high-quality phase-pure and single crystalline pyrite nanocrystals were synthesized via facile, low-cost, and environment friendly hydrothermal method. The molar ratio of sulphur to iron and the reaction time play a crucial role in determining the quality and morphology of FeS₂ nanocrystals. X-ray diffraction and high-resolution transmission electron microscopy confirm that phase-pure and single crystalline pyrite nanocrystals can be synthesized with high sulphur to iron molar ratio and sufficient reaction time. For the first time, a crystalline nanogap pyrite photodetector with promising photocurrent and UV-visible photoresponse has been fabricated. This work further demonstrates a facile route to synthesize high-quality FeS₂ nanomaterials and their potential in optoelectronic applications.     

Preparation of porous SiC ceramics skeleton with low-cost and controllable gradient based on liquid crystal display 3D printing

In recent years, the demand for gradient porous ceramics is increasing in engineering field. By traditional process, the disadvantage of prepared gradient porous ceramics is its low porosity and uncontrollable pore gradient, which limits the wide application of gradient porous ceramics. In this study, the gradient porous ceramic skeleton (GPCS) was prepared by combining liquid crystal display (LCD) 3D printer with liquid silicon infiltration (LSI). Experimental results showed that the mass of ceramic powder in the ceramic slurry with optimal printing performance accounts for 45% of the mass of photosensitive resin, and the thermal decomposition rate of photosensitive resin is faster in the range of 300–450 °C. Furthermore, the effect of LSI temperature on the composition, microstructure and mechanical properties of GPCS was investigated. The GPCS is expected to be applied in the fields of energy storage, heat transfer and biofouling, among others.     

Recycled Polyolefin-Based Plastic Wastes for Sound Absorption

Recycling of high-volume polyolefin-based packaging wastes in India is challenging, as they have low recycle value, high levels of contamination, and lack of direct processing methods. This work discusses a two-stage mechanical processing method for recycling the polyolefin-based plastic wastes that are not conventionally recycled. With the objective of improving specific properties like sound absorption and noise reduction, inhomogeneities were introduced in the recycled product. This was achieved by mixing polyolefin-based packaging wastes with other waste materials such as plastic-coated aluminium foils, expanded polystyrene, and coir pith in varying quantities. More than 30 times volume reduction was achieved by a two-stage compression molding process. The sound absorption properties of the recycled materials are found to be comparable to expanded polystyrene and glass wool when small quantities (2–3 wt%) of materials like expanded polystyrene waste and coir pith were added. Impact strength of the recycled material decreased with increasing amounts of secondary additives like metal foils. Flexural strength of the recycled material was found to be maximum at about 30 wt% of metal foils. The end product could find applications in the construction industry due to the sound-absorption properties and the mechanical strength.     

Recycled wastes as precursor for synthesizing wollastonite

The application of wollastonite in various industries has attracted the attention of scientists to synthetically produce it. Also, the ecological demands of a healthy and safe environment urged them to utilize the industrial wastes accumulating year after year and threatening the environment.     

聚苯乙烯再生改性专用料标准化研究

简要介绍了与聚苯乙烯再生改性专用料相关的国内外标准现状,对标准草案中的关键问题进行了分析,并提出了进一步修改标准草案的建议.     

MBR工艺处理聚酯废水的运行管理要点

介绍了厌氧-MBR-氧化塘联合工艺用于聚酯废水处理的工艺流程和处理效果。重点探讨了工艺过程中主要构筑物的运行、控制要点。介绍了MBR池在运行管理中常见的故障,进行了原因分析,并给出排除的方法。采用该法处理聚酯废水,提高了活性污泥浓度,极大地改善了聚酯废水处理中好氧过程的效率,具有良好的经济技术可行性,处理效果持续稳定。     

再生细骨料逐级取代对再生砂浆强度和微观形貌的影响

基于天然砂分计筛余百分率,采用再生细骨料按照0～0.315 mm、0～0.63 mm、0～1.25 mm、0～2.5 mm和0～5.0 mm不同粒级逐级取代天然砂制作再生砂浆,测定其在0.55、0.60、0.65水灰比下7d、14d和28 d的抗折抗压强度和微观形貌.试验结果表明:再生砂浆试件的抗折抗压强度均大于空白试件,且随着再生细骨料逐级取代率的提高而增大;当再生细骨料100％逐级取代天然砂时,龄期为14 d时的再生砂浆的强度增长最大;28 d时,再生砂浆抗压强度的降低幅度随着水灰比的增加而增加,但抗折强度的降低幅度却随着水灰比的增加而减小;随水化龄期的增加,再生砂浆中水化产物不断增多,界面过渡区越来越密实.     

Engineering design approaches for minimum fouling in submerged MBR

A contributor to success in managing membrane operations is to be able to identify suitable engineering design approaches to slow down the membrane fouling rate. Two such approaches were discussed in this study, namely: (1) offsite chemical and mechanical cleaning, and (2) air scouring. A longer subsequent operation time was observed after a membrane was cleaned chemically compared with mechanically. For air scouring during membrane operation, the investigation aimed at determining the crossflow velocity induced by coarse and fine bubble diffusers. Higher crossflow velocities were obtained with the latter. Uniformly distributed fine air bubbling might possibly have caused less uplift resistance and induced higher crossflow velocities. Such air scouring, at critical aeration intensity, was able to prolong the membrane operation for up to 8 months without needing chemical or mechanical cleaning.     

Application of MBR for hospital wastewater treatment in China

In China, the number of hospitals has increased to 19,712 in 2008, with the production of hospital wastewater reaching 1.29 × 10⁶ m³/d. Membrane bioreactor (MBR) technology presents a more efficient system at removing pathological microorganism compared with existing wastewater treatment systems. In the past 8 yr, over 50 MBR plants have been successfully built for hospital wastewater treatments, with the capacity ranging from 20 to 2000 m³/d. MBR can effectively save disinfectant consumption (chlorine addition can decrease to 1.0 mg/L), shorten the reaction time (approximately 1.5 min, 2.5-5% of conventional wastewater treatment process), and attain a good effect of inactivation of microorganism. Higher disinfection efficacy is achieved in MBR effluents at lower dose of disinfectant with less disinfection by-products (DBPs). Moreover, when capacity of MBR plants increases from 20 to 1000 m³/d, their operating cost decreases sharply.