Removal of Cd2+, Cu2+, Ni2+, and Pb2+ ions from aqueous solutions using tururi fibers as an adsorbent

This work investigates the removal of Cd²⁺, Cu²⁺, Ni²⁺, and Pb²⁺ ions from aqueous solutions using tururi fibers as an adsorbent under both batchwise and fixed‐bed conditions. It was found that modification of the tururi fibers with sodium hydroxide increased the adsorption efficiencies of all metal ions studied. The fractional factorial design showed that pH, adsorbent mass, agitation rate, and initial metal concentration influenced each metal adsorption differently. The kinetics showed that multi‐element adsorption equilibria were reached after 15 min following pseudo‐second‐order kinetics. The Langmuir, Freundlich, and Redlich–Peterson models were used to evaluate the adsorption capacities by tururi fibers. The Langmuir model was found to be suitable for all metal ions. Breakthrough curves revealed that saturation of the bed was reached in 160.0 mL with Cd²⁺ and Cu²⁺, and 52.0 mL with Ni²⁺ and Pb²⁺. The Thomas model was applied to the experimental data of breakthrough curves and represented the data well. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40883.     

High-temperature flexural strength of SiC ceramics prepared by additive manufacturing

Silicon carbide (SiC) ceramics, as a kind of candidate material for aero-engine, its high-temperature performance is a critical factor to determine its applicability. This investigation focuses on studying the high-temperature properties of SiC ceramics fabricated by using additive manufacturing technology. In this paper, SiC ceramics were prepared by combining selective laser sintering (SLS) with precursor infiltration and pyrolysis (PIP) technique. The microstructure, phase evolution, and failure mechanism after high-temperature tests were explored. SiC ceramic samples tested at room temperature (RT), 800°C, 1200°C, 1400°C, and 1600°C demonstrated bending strengths of 220.0, 226.1, 234.9, 215.5, and 203.7 MPa, respectively. The RT strength of this material can be maintained at 1400°C, but it decreased at 1600°C. The strength retention at 1400°C and 1600°C were 98% and 92%, respectively. The results indicate that the mechanical properties of SiC ceramics prepared using this method have excellent stability. As the temperature increases, the bending strength of the specimens increased slightly and reached the peak value at 1200°C, and dropped to 203.7 MPa at 1600°C. Such an evolution could be mainly due to the crack healing, and the softening of the glassy phase.     

Construction of porous cellulose tubes and the evaluations of mechanical properties and cytocompatibility

In this work, regenerated cellulose (RC) tubes with the porous structure were successfully fabricated for constructing the non-invasive detection platform of vascular microenvironment. Polyethylene oxide (PEO) as a porogen was applied to induce porous structure of cellulose tubes. Tensile and burst pressure tests were carried out to evaluate the effects of PEO molecular weight and amount on the mechanical properties of cellulose tubes. The results showed that tensile strength of RC tubes was increased with increasing PEO molecular weight. The compliance of cellulose tubes decreased with increasing the PEO content. When 120 kDa PEO was applied, the average tensile strength of RC tubes could reach 1.27 MPa. The maximum burst pressure and compliance of RC tubes could reach 488.25 ± 35 mmHg and 7.50 ± 3.7%/100 mmHg, respectively. Human umbilical vein endothelia cells (HUVECs) exhibited obvious proliferation on cellulose tubes, and the collagen coating further improve the biocompatibility. The incorporated collagen further improved adhesion of the cells and growth on cellulose tubes. This work provided a kind of cellulose-based tube material with potential application for the construction of the vitro vascular microenvironment.     

A new flame-retardant medium density fiberboard with no formaldehyde release: Wood fiber cell walls template zeolite via in situ thermocompression

Fiberboard which is not flame retardant and releases formaldehyde is widely used in residents' life, which brings serious problems. Now, we use water glass and Al₂(SO₄)₃ to form zeolite precursor, and use UP as adhesive to prepare zeolite-based flame retardant formaldehyde-free medium density fiberboard in situ within a few minutes. The molecular sieve structure was characterized by SEM, TEM, BET, and XRD. At the same time, we put forward the possible mechanism of zeolite formation according to the internal temperature and pressure test during fiberboard production. Wood fiber is coated with zeolite, which separates pyrolysis gas from air and avoids further combustion, resulting in low heat release, low smoke and toxic carbon monoxide emission, high residue, and good flame retardant performance. Furthermore, the formaldehyde emission of the formaldehyde-free flame retardant board is 0.047 mg/L, which proves that it does not contain formaldehyde.     

Regenerated cellulose/layered double hydroxide nanocomposite films with improved mechanical property

Construction of environment-friendly biomass-based nanocomposites with high performance is in great demand for developing of a sustainable low-carbon society. Here, transparent and flexible regenerated cellulose (RC)/layered double hydroxide (LDH) nanocomposite films were prepared from aqueous NaOH/urea solutions. The obtained nanocomposite films were characterized using AFM, SEM, FTIR, XRD, tensile testing, water contact angle, and thermogravimetric analysis. The results show that LDH nanoplatelets were individually dispersed with a thickness of 1 nm and surface diameter of 100 nm after ultrasonic treatment. Strong interaction existed between LDH nanoplatelets and cellulose molecules, leading to the improved thermal stability and mechanical strength of RC together with the original good properties of LDH. In particular, the nanocomposite films with 10 wt% LDH showed a 135% and 234% increase in the tensile strength and Young's modulus than those of the neat RC film. Meanwhile, the nanocomposite films exhibited high transparency. Therefore, these RC/LDH nanocomposites are promising in the fields of high-performance packaging materials, flexible display panels, and high-temperature dielectric materials.     

Fire retardant cellulose aerogel with improved strength and hydrophobic surface by one-pot method

Bio-based materials with multifunctional performance are getting immense attention nowadays for their environment friendly and renewable character. Inspired by toughening effect of graphene nanosheets and borate chemistry, a simple in-situ borate crosslinking in water and freeze-drying method was employed to fabricate a fire retarded bio-based aerogel. The structure of the material was evaluated and analysis by SEM, XRD, FTIR, Raman and XPS. Importantly, the bio-based aerogel has improved strength and adsorption properties due to unique structure. The compressive strength of rGO(reduced graphene oxide) + CMC (carboxymethyl cellulose) aerogel could reach 128 ± 2.1 kPa which is five times that of neat CMC aerogel. The bio-based aerogel can load more than 2500 times of self-weight. The adsorption capacity for organic solvents and oil of rGO+CMC aerogel is also greatly improved by a little rGO (1%) introducing due to its unique porous structure and hydrophobic nature of rGO. Additionally, rGO+CMC aerogel is also found fire resistant with relatively low thermal conductivity due to the borate and GO introduction.     

Mechanical and ablation properties of a C/C-HfB2-SiC composite prepared by high-solid-loading slurry impregnation combined with precursor infiltration and pyrolysis

An improved high-solid-loading slurry impregnation process was developed to introduce HfB₂ particles into a low-density C/C preform efficiently, and precursor infiltration and pyrolysis process was used for densification to obtain a C/C-HfB₂-SiC composite. The microstructure characterization revealed that HfB₂ particles uniformly filled the pores in the C/C preform, and SiC well densified the interstices between HfB₂ particles and the small pores in the carbon fiber bundles. After being tested, the C/C-HfB₂-SiC composite had a density of 4.07 g/cm³ and a bending strength of 344.8 MPa, and exhibited a non-brittle fracture behavior. After ablation with oxyacetylene flame at 2500 ℃ for 120 s, the mass ablation rate and linear ablation rate of the C/C-HfB₂-SiC composite were 0.5 mg/s and 0.415 μm/s, respectively. The good ablation performance is attributed to the hindering effect of the HfO₂ scale on oxygen diffusion at high temperature.     

微发泡硬质PVC/木粉体系型材的挤出

以植物纤维机制木粉取代通常的矿物填料，成功地制得了微发泡硬质PVC／木质体系的塑料型材，分析和讨论了型材的结构特点、工艺要点以及聚合物和木粉的界面改性。     

高性能木纤维增强聚丙烯复合材料的制备

采用双螺杆挤出机制备了木纤维（松木粉）增强聚丙烯（PP）复合材料，并对其力学性能及形态结构进行了研究。结果表明，用马来酸酐接枝PP（PP-g-MAH)作增容剂可有效地增加基体与木纤维之间的粘合作用，使木纤维增强PP复合材料的拉伸强度，弯曲强度和弯曲弹性碍都得到很大提高；在木纤维增强PP复合材料中加入三元乙丙橡胶（EPDM）进行增韧，可在高木纤维含量下使复合材料基本保持纯PP的力学性能。     

催化燃烧消除有毒和污染气体

用浸渍法研制了过渡金属及其氧化物系列的燃烧催化剂，研究了CO和CH4的燃烧反应，通过对催化剂活性和稳定性的测定，筛选出性能优良的催化剂，考察了浸渍液浓度，活性组分及还原温度对催化活性的影响。此催化剂可用于消除有毒和有机污染气体。