癸酸-石蜡/石墨烯气凝胶定形相变材料的制备及热物性分析

随着碳中和理念的逐步推进,调整能源供应政策,倡导低碳生活,可推动全社会的绿色发展,采用相变材料(PCMs)储存和释放热量,能够有效地利用可再生能源,可减少化石燃料带来的CO₂释放问题。本文利用石墨烯气凝胶作为相变材料的载体,分别采用不同比例的癸酸/石蜡进行有机相耦合,制备了一系列高封装率、低渗漏率的石墨烯定形相变材料。研究发现当石墨烯气凝胶定形相变材料中癸酸/石蜡为7∶3时,相变焓达到202.91J/g。经过200次循环后复合材料的相变潜热变化量在4.25%以内,渗漏率仅为3.20%。采用DSC、TG、XRD、SEM对材料进行微观结构分析说明,石墨烯气凝胶改善了相变介质的形状稳定性,有效地阻止了相变过程中耦合的有机相泄漏,使材料储放热稳定,增强了导热作用,具有良好的应用前景。     

Fabrication and properties of biocidal fibre materials

The conditions for fabricating biocidal material based on strongly basic VION AS-1 fibre containing iodine were elaborated. The elevated biocidal activity of the mateiral allows using it as the filtering component in filters for purification of drinking water with a high concentration of microorganisms which cause dangerous gastrointestinal diseases. All-Russian Scientific-Research Institute of Polymeric Materials, Mytishchi; Bioprotsess Scientific and Industrial Association, Kirov; METTEM-Tekhnologiya Closed Joint Stock Company, Balashikha. Translated fromKhimicheskie Volokna, No. 6, pp. 37–38, November–December, 1999.     

锌基复合电极原位水热合成和电化学性能研究

以硝酸锌、硝酸铝为前体,尿素为沉淀剂,采用水热法在泡沫镍表面原位生长锌基有序微纳米片状电极材料。采用X射线衍射、扫描电子显微镜、透射电子显微镜等手段对合成产物的结构和形貌进行了表征。研究结果表明,产物为少量铝掺杂的Zn_4-xAl_x（OH）₆CO₃·H₂O层状双金属氢氧化物,形貌为正六边形片状结构,直径为1~2 μm,厚度为80~200 nm。以合成的锌基复合电极为工作电极,采用三电极体系进行电化学性能测试,结果显示电极呈现典型的赝电容性质,电流密度为5 A/g条件下电极质量比电容仍高达1 022.3 F/g。     

还原氧化石墨烯气凝胶/二十烷相变材料的制备及性能

以氧化石墨烯(GO)为原料,采用胶体团聚法制备了还原氧化石墨烯气凝胶,再通过自扩散获得了还原氧化石墨烯气凝胶/二十烷(r-GO aerogel/eicosane)复合相变材料,研究了复合材料结构与性能的关系.采用热重分析仪(TGA)和差示扫描量热仪(DSC)测试了二十烷和复合材料的热性能,确认了二十烷质量分数与复合材料...     

硅酸铝纤维和玻璃纤维复合二氧化硅气凝胶材料的制备与性能

分别以硅酸铝纤维和玻璃纤维为骨架材料,采用溶胶-凝胶、常压干燥制得纤维复合二氧化硅气凝胶材料,并对材料进行了结构和性能的测试分析。结果表明,二氧化硅气凝胶附着于纤维表面,提高了材料力学强度。硅酸铝纤维复合二氧化硅气凝胶材料的隔音性能优于玻璃纤维复合二氧化硅气凝胶材料。两种纤维复合二氧化硅气凝胶材料耐高温、燃烧性能均达到A级。硅酸铝纤维复合二氧化硅气凝胶材料和玻璃纤维复合二氧化硅气凝胶材料的产烟毒性分别为AQ₁级和AQ₂级,导热系数分别为0.034 W/（m·K）和0.033 W/（m·K）。     

Fabrication of titanosilicate pillared MFI zeolites with tailored catalytic activity

Titanosilicate pillared MFI zeolite nanosheets were successfully synthesized by infiltrating the mixed tetraethyl orthosilicate (TEOS)/tetrabutyl orthotitanate (TBOT) solvent into the gallery space between adjacent MFI zeolite layers. The obtained zeolite catalysts were characterized using powder X-ray diffraction, N₂ adsorption/desorption isotherms, scanning electron microscopy, transmission electron microscopy, ultraviolet–visible spectroscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy techniques. The H₂O₂ oxidation of dibenzothiophene (DBT) was used to evaluate the catalytic performance of the obtained titanosilicate pillared MFI zeolites. The conversion of DBT and selectivity of dibenzothiophene sulfone (DBTS) were most affected by the textural properties of the zeolites. This was attributed to the DBT and DBTS molecules being larger than micropores of the MFI zeolites. The conversion of DBT and yield of DBTS could be systematically tailored by tuning the molar ratio of the TEOS/TBOT solvent. These results implied that a balance between the meso- and microporosity of zeolites and tetrahedrally coordinated Ti(IV) active sites of titanosilicate pillars can be achieved for the preparation of desired catalysts during the oxidation of bulk S compounds.     

Novel auto-photosensitive polyimides with tailored properties

An overview is given on auto-photosensitive polyimides as introduced for the first time in 1985. It is shown how development proceeded and how the chemical basis of auto-photosensitive polyimides was extended beyond BTDA. Novel “photosensitizer tetracarboxylic dianhydrides” like 2,3,6,7-thioxanthonetetracarboxylic dianhydride (TXDA) were synthesized and copolymerized into preimidized nonphotoactive polyimides containing tetracarboxylic acids like 6FDA or ODPA. Novel photosensitive polyimides were obtained that carry all essential features of BTDA based systems plus higher photospeed. They provide the ability to better tailor material properties to specific applications.     

Fabrication of Mg-doped ZnO nanofibers with high purities and tailored band gaps

The tailored doping levels towards the band gap tunability are one of the challenges to push forward the potential application of one-dimensional (1D) ZnO nanostructures in the opto/electric nanodevices. In present work, we reported the exploration of Mg-doped ZnO nanofibers via electrospinning of polyvinylpyrrolidone (PVP), Zn(CH₃COO)₂ (ZnAc) and Mg(CH₃COO)₂ (MgAc), followed by calcination in air. The resultant products were systematically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscope (HRTEM), and X-ray photoelectron spectroscopy (XPS). The optical measurements (UV–vis) of the Mg-doped ZnO nanofibers suggested that the optical band gaps of the ZnO nanofibers could be tuned from 3.33 to 3.40 eV as a function of the Mg doing levels. This tunability of the band gap of ZnO nanofibers with an intentional impurity could eventually be useful for optoelectronic applications.     

Isocyanate-crosslinked silica aerogel monolith with low thermal conductivity and much enhanced mechanical properties: Fabrication and analysis of forming mechanisms

The applications of silica aerogels are restricted due to their intrinsic fragile property. Polymerization of di-isocyanates can be templated onto the mesoporous surface of the –NH₂ group modified silica clusters, resulting in the conformal crosslinked coating on surface of silica clusters. Aminopropyltriethoxysilane (APTES), as the silica co-precursor and amine group modification agent, is involved containing tetramethyl orthosilicate (TMOS) silica precursor, while hexamethylene diisocyanate (HDI) is incorporated as the polymer crosslinking agent. The effects of different amounts of APTES on the physicochemical properties of the resulting crosslinked aerogels are investigated. The results show that the optimized APTES/TMOS volume ratio can be determined at 0.5:1. The resulting optimal crosslinked silica aerogel possesses large BET specific surface area of 150.9 m²/g, low thermal conductivity of 0.037 W/(m·K), and the Young's modulus is as large as 18 MPa under strain of 4.2%, much higher than that in the previously published works. The polymerization reaction mechanism forming the polyurethane chains has also been proposed. In addition, the interactions between silica clusters and polymer chains are studied by molecular mechanics and molecular dynamics. The interactions are mainly dependent on non-bonding energy, and the electrostatic energy has decisive impact on the combination of silica clusters and polymer chains. The density field of C, H, N, O, and Si elements overlaps with each other, indicating that the polymer crosslinked silica aerogel maintains typical three-dimensional porous structure. The N element enriches in the region between silica clusters, further verifying the formation –CONH–(CH₂)₆–CONH- polyurethane chains, which is actually responsible for the much enhanced mechanical property.     

Fabrication of low-density foam shells from resorcinol-formaldehyde aerogel

Resorcinol-formaldehyde (RF) aerogel chemistry has been used with encapsulation techniques to fabricate low-density, transparent, foam shells. To accomplish this, the gelation time was reduced from several hours to several minutes by the addition of acid following base-catalyzed RF particle growth. However, additional “annealing” of the gel for at least 20 h was needed to maximize crosslinking and minimize swelling in exchange solvents. Increasing the molar ratio of formaldehyde to resorcinol from 2 to 3 also helped to increase crosslinking. Densification of the foam shells due to dehydration during curing was greatly reduced by judicious choice of immiscible oil phases and by saturating the exterior oil phase during the annealing stage. Shells have been produced with diameters of about 2 mm, wall thicknesses ranging from 100 to 200 μm and foam densities approaching 50 mg/cc. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2111–2122, 1997     

非传统表面活性剂制备硅基介孔材料新进展

因无机多孔材料在诸多领域具有潜在的应用前景,其合成路线的研究一直备受研究者的广泛关注。本文综述了非传统表面活性剂在硅基介孔材料合成中的研究进展。阐述了有机小分子、离子液体和新型硅源等非传统表面活性剂作为模板剂制备硅基介孔材料的现状。与利用传统表面活性剂的合成路线相比,以非传统表面活性剂为模板的制备路线在合成过程中体现了诸多优势,为硅基多孔材料的合成提供了新的思路。     

Enhancing aerogel mechanical properties with incorporation of POSS

Silica aerogels consisting of nanoparticles and numerous nano-pores have many attractive attributes. However, the weak mechanical properties severely limited the practical application of the silica aerogel. In this work, a facile approach was employed to strengthen the silica aerogel while the multi-alkoxy polyhedral oligomeric silsesquioxane (POSS) joined with methyltriethoxysilane (MTES) as the co-precursor. Three kinds of stiff core POSS with different amount of alkoxy groups were chosen to prepare aerogels. The result attributes showed all aerogels owned mesoporous structure (10–20 nm), high specific surface area (760–877 m² g⁻¹) and good thermal stability. Moreover, with the introduction of POSS, the mechanical properties had been apparently enhanced. The suitable addition of functional groups and the adjustment of cross-linking density made the aerogel own more room to deform and the skeleton still strong enough to endure large deformation. In addition, new peaks appeared in the XRD patterns at the same time. The preparation strategy of composite aerogels may guide a facile way to regulate the aerogel attributes. Furthermore, the aerogel potential application in oil-water separation has also been investigated.     

Fabrication and properties of antimicrobial cellulose materials based on polyelectrolyte complexes

The effect of the structure of the reacting compounds and reaction conditions on the composition of polyelectrolyte complexes formed in the reaction of polyanions — graft copolymer of cellulose and polyacrylic acid and polymethacrylic acid sodium salt (C-gr-PAa (PMAA)) and polyhexamethyleneguanidine hydrochloride (PHMG) and polyethylenimine (PEI) — and the kinetics of their formation were investigated. The conditions that ensure complete binding of the polycation were determined and the necessity of a significant excess of polycation and long duration of the reaction for formation of complexes of stoichiometric composition was demonstrated. In studying desorption of antimicrobial substances from the polyelectrolyte complex, the effect of the process production scheme and type of cation and the significant role of diffusion factors in this process on the stability of the complex was established. Moscow State Textile Academy. Translated fromKhimicheskie Volokna, No. 3, pp. 14–19, May–June, 1999.     

Fabrication and magnetic properties of granular Co/porous InP nanocomposite materials

A novel Co/InP magnetic semiconductor nanocomposite was fabricated by electrodeposition magnetic Co nanoparticles into n-type porous InP templates in ethanol solution of cobalt chloride. The content or particle size of Co particles embedded in porous InP increased with increasing deposition time. Co particles had uniform distribution over pore sidewall surface of InP template, which was different from that of ceramic template and may open up new branch of fabrication of nanocomposites. The magnetism of such Co/InP nanocomposites can be gradually tuned from diamagnetism to ferromagnetism by increasing the deposition time of Co. Magnetic anisotropy of this Co/InP nanocomposite with magnetization easy axis along the axis of InP square channel was well realized by the competition between shape anisotropy and magnetocrystalline anisotropy. Such Co/InP nanocomposites with adjustable magnetism may have potential applications in future in the field of spin electronics.     

Antibacterial applications and safety issues of silica-based materials: A review

As the problem of bacterial contamination continues to grow in its significance, researchers have reported many antibacterial materials that are based on inorganic compounds. Of these, materials that are based on silica and its derivatives have been widely used in engineering, medicine, and food. This paper reviews the advantages, safety issues, and applications of silica and its derivatives, as reported in recent years. The information provided highlights the preparation, application, and antimicrobial efficiency of materials that are based on silica and have different structure/size. We outline the possible antimicrobial mechanisms of silica-based materials and the potential challenges that researchers may face. With a focus on increasing concerns regarding bacterial contamination in the food and medical industries, we have also proposed corresponding antibacterial material preparation strategies.     

Reactive blending as a tool for obtaining poly(ethylene terephthalate)-based engineering materials with tailored properties

The structure and properties of blends of poly(ethylene terephthalate) (PET) with poly(trimethylene terephthalate) (PTT) at PTT concentration ≤30 wt.%, obtained with three different methods: from solution, melt extrusion, and direct spinning, are investigated. Relationships between the method of preparation and properties of blends are established. All blends show glass transition temperature at values determined by composition, and crystallization properties also dependent on the preparation method. Blends obtained from solution show separated melting of components. For blends obtained from the melt only PET crystallizes. The melting temperature decreases with the residence time of the melt at high temperatures, due to occurrence of ester exchange reactions. It is shown that reactive blending of PET/PTT mixtures occurring during preparation is a versatile route for obtainment of engineering materials with good mechanical properties, high crystallinity, glass transition temperature lower than that of PET, and melting temperature that may be controlled by the processing conditions.     

Fabrication of superhydrophobic and antibacterial surface on cotton fabric by doped silica-based sols with nanoparticles of copper

The study discussed the synthesis of silica sol using the sol-gel method, doped with two different amounts of Cu nanoparticles. Cotton fabric samples were impregnated by the prepared sols and then dried and cured. To block hydroxyl groups, some samples were also treated with hexadecyltrimethoxysilane. The average particle size of colloidal silica nanoparticles were measured by the particle size analyzer. The morphology, roughness, and hydrophobic properties of the surface fabricated on cotton samples were analyzed and compared via the scanning electron microscopy, the transmission electron microscopy, the scanning probe microscopy, with static water contact angle (SWC), and water shedding angle measurements. Furthermore, the antibacterial efficiency of samples was quantitatively evaluated using AATCC 100 method. The addition of 0.5% (wt/wt) Cu into silica sol caused the silica nanoparticles to agglomerate in more grape-like clusters on cotton fabrics. Such fabricated surface revealed the highest value of SWC (155° for a 10-μl droplet) due to air trapping capability of its inclined structure. However, the presence of higher amounts of Cu nanoparticles (2% wt/wt) in silica sol resulted in the most slippery smooth surface on cotton fabrics. All fabricated surfaces containing Cu nanoparticles showed the perfect antibacterial activity against both of gram-negative and gram-positive bacteria.     

Preparation of macroporous silica-based crown ether materials for strontium separation

To develop a separation process of Sr(II), a macroporous silica-based 4,4′,(5′)-di(tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6) polymeric material, (DtBuCH18C6+Oct)/SiO₂-P, was synthesized by impregnating and immobilizing DtBuCH18C6 and 1-octanol into the pores of the macroporous SiO₂-P particles support. DtBuCH18C6 was modified with 1-octanol through hydrogen bonding. The adsorption of simulant elements of some typical fission products Ru(III), Pd(II), Ba(II), Mo(VI), La(III), Y(III), Sr(II), Cs(I) and those of non-fission products Na(I) and K(I) onto (DtBuCH18C6+Oct)/SiO₂-P were studied at 298 K. The effects of the HNO₃ concentration in a range of 0.1–5.0 M and contact time on the adsorption were investigated. (DtBuCH18C6+Oct)/SiO₂-P showed excellent adsorption ability and high selectivity for Sr(II) over all of the tested metals except Ba(II). Partitioning of Sr(II) from a 2.0 M HNO₃ solution containing ~5.0 × 10^?3 M of the tested metals was conducted utilizing (DtBuCH18C6+Oct)/SiO₂-P packed column. Pd(II), Mo(VI), Y(III), La(III), Ru(III), K(I), Cs(I), and Na(I) showed no adsorption and flowed into effluent along with 2.0 M HNO₃. Sr(II) was retained on (DtBuCH18C6+Oct)/SiO₂-P and was eluted effectively by H₂O, while Ba(II) showed similar elution behavior. The bleeding of total organic carbon leaked from (DtBuCH18C6+Oct)/SiO₂-P was evaluated. It was demonstrated that the macroporous silica-based (DtBuCH18C6+Oct)/SiO₂-P materials are promising in separation of Sr(II) from high level radioactive waste.     

Preparation and characterization of polyurethane/silica aerogel nanocomposite materials

In this investigation, silica aerogel (SA)/Rigid Polyurethane (PUR) foam composites and silica aerogel/Polyurethane (PU) composites were prepared by dry mixing of granular and grinded silica aerogels with polyol part. They were then combined with diisocyanate part. Three different types of PUR foams and an elastomeric coating grade of PU were studied as well. Results show that thermal conductivity of foams did not decrease by adding silica aerogel. It even increased for some grades which is assumed to be due to the change in cell configuration of these foams. It was also found that sound insulation performance of these cellular composites did not improve significantly. Unlike foam composites, addition of silica aerogel into elastomeric PU improved its thermal and acoustic insulation properties. Because of the more promising properties of elastomeric PU composites, further examinations including measurements of compression strength and water contact angle of silica aerogel/PU composites were also taken. Final results showed a significant improvement in general properties of PU coatings by adding little amounts of silica aerogel (1–4 wt %). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44521.     

Oil absorption performance of polymer/clay aerogel materials

Oil absorption performance of aerogels produced from poly(amide‐imides), epoxies, and acrylic polymers were dependent upon freezing conditions, which in turn dictated solid state structures of these materials. Denser aerogels have less void space, and are more efficient at filling that space with oil, supporting the hypothesis that capillary spacing plays a vital role in determining oil absorption. Lower molecular weight epoxy‐based polymers produced aerogels with small capillary radii, again allowing increasing amounts of the liquid to penetrate between the aerogel layers. Aerogels produced from acrylic emulsions outperformed the other two systems tested in terms of volume per volume absorption. The initial difficulty with these materials, the fact that they still retain some hydrophilicy and absorb water, was overcome by simple post curing treatment, which was able to reduce water absorption to near zero levels. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45844.