PVP/WPU复合电纺纤维膜的制备及其雾霾过滤性能研究

通过静电纺丝法制备了聚乙烯吡咯烷酮/水性聚氨酯(PVP/WPU)复合纤维膜。采用扫描电镜(SEM)对该复合电纺纤维膜的形貌进行分析;利用PM sensor传感器测试过滤前后的空气颗粒物浓度,对复合纤维膜的过滤效率进行表征;通过孔隙率测试确定了PVP/WPU混合纺丝液的合理配比。结果表明:当混合纺丝液中PVP与WPU的质量分数均为7%时,可制得纤维笔直交错排列、形貌较好且孔隙率适中的复合电纺纤维膜,该纤维膜对雾霾空气中的小分子颗粒具有较高的过滤效率,其中对PM2.5和PM1.0的过滤效率分别比纯PVP膜提高了15.14%和20.05%。     

TiO_2/SiO_2复合纳米纤维的GQDs改性及其对甲醛的可见光催化降解性能

采用静电纺丝法合成了TiO_2/SiO_2柔性复合纳米纤维膜,而后对其进行石墨烯量子点(GQDs)改性,制备了GQDs/TiO_2-SiO_2复合纳米纤维,其中GQDs用水热法合成。用X射线衍射仪(XRD)、电子万能材料试验机、扫描电子显微镜(SEM)、紫外-可见分光光度计(UV-Vis)对其物相组成、力学性能、微观形貌以及光催化性能进行了表征。结果表明:尺寸在7 nm~15 nm之间的GQDs松散沉积在直径为200 nm~400 nm的TiO_2/SiO_2纳米纤维上,纤维连续性好,复合薄膜有较好的力学性能;TiO_2的结晶较好,为锐钛矿相;GQDs复合后将TiO_2的本征吸收从390 nm左右延伸到了420 nm左右,拓宽了TiO_2的吸收范围。在可见光催化降解中,初始浓度为0.32 mg/m~3的甲醛气体110 min后的降解效率达到70%。     

烧结温度和TiO_2掺杂量对氧化铝基微波陶瓷性能的影响

选用Mg O–Cu O–TiO_2添加剂作为氧化铝陶瓷的烧结助剂,在空气气氛下经过常压烧结制备氧化铝(Al_2O_3)陶瓷。研究了TiO_2掺杂量和烧结温度对氧化铝陶瓷材料微观结构、相组成和介电性能的影响。结果表明:掺杂适量的TiO_2有利于Al_2O_3陶瓷晶粒生长以及致密化。随着TiO_2添加量的增加,烧结体致密度、介电常数和Q·f值都呈现先升高后降低趋势,随着温度的升高,Al_2O_3陶瓷样品致密度也呈先升高后降低趋势。当烧结温度为1 500℃、TiO_2掺杂量为0.8%(质量分数)时,Al_2O_3陶瓷样品的综合性能良好:相对密度为97.89%,介电常数为9.89,品质因数Q·f为38 028 GHz。     

纳米雾化技术构筑EVOH/TiO2-TMPS超疏水纤维膜

利用高压静电纺丝构造聚乙烯–乙烯醇(EVOH)纤维膜,在纺丝过程中利用钛酸丁酯(TBT)–乙醇溶液通过纳米雾化原位水解制得TiO_2纳米粒子,并在成膜后利用丙基三甲氧基硅烷(TMPS)表面修饰TiO_2,通过这三种微观结构构筑方法的有机协同,制得EVOH/TiO_2–TMPS纤维膜。采用扫描电子显微镜、傅里叶变换红外光谱、紫外能谱和接触角测量仪,研究纤维膜的表面形貌、化学结构、紫外光吸收能力及疏水性能。结果表明,纳米雾化技术的复合效果显著,EVOH/TiO_2–TMPS纤维膜微结构化程度明显;TiO_2成功接枝TMPS,构造出疏水TiO_2纳米粒子;原位复合的TiO_2纳米粒子使纤维膜表现出优异的紫外光吸收能力;当TBT溶液浓度为0.1 mol/L时,EVOH/TiO_2–TMPS纤维膜的接触角达到153.4°,表明成功制备了超疏水纤维膜。     

KMnO_4浓度对MnO_2结构和电容性能的影响

以KMn O_4和Mn SO_4为原料,采用水热法制备纳米Mn O_2,研究了KMn O_4浓度对Mn O_2结构和电容性能的影响。结果表明:KMn O_4浓度对Mn O_2产物的晶型、晶粒尺寸和形貌影响显著,随着KMn O_4浓度增大,产物晶型由β-Mn O_2转变为α-Mn O_2,并且Mn O_2纤维逐渐增长变粗。晶粒和纤维直径较小的α-Mn O_2的电荷转移电阻(Rct)和扩散阻抗(W)最小,从而具有最大的电容量和良好的倍率性能,在电流密度为0.05 m A/cm~2时电容量为227 F/g;β-Mn O_2的容量较低,为113 F/g,但循环性能最好,经过500次循环后容量保持率达92.0%。     

氧化石墨烯–镝掺杂二氧化钛复合光催化材料的制备及光催化性能（英文）

以氧化石墨烯(GO)、钛酸四丁酯和硝酸镝为原料,用柠檬酸络合溶胶–凝胶法原位合成氧化石墨烯–镝掺杂二氧化钛(GO/Dy~(3+)–TiO_2),再经硼氢化钠还原得到还原氧化石墨烯–镝掺杂二氧化钛(r GO/Dy~(3+)–TiO_2)复合光催化剂。利用X射线衍射、透射电子显微镜、Raman光谱、荧光光谱对r GO/Dy~(3+)–TiO_2样品进行分析表征。研究了GO的引入对TiO_2晶体结构、形貌、光生载流子寿命和光催化活性的影响。结果表明:锐钛矿相Dy~(3+)–TiO_2呈纳米颗粒状均匀分布在r GO表面;GO的引入可抑制TiO_2晶粒长大及从锐钛矿向金红石的转变;r GO/Dy~(3+)–TiO_2复合光催化剂的光催化活性明显高于Dy~(3+)–TiO_2。     

不同相对湿度下亲疏水纳米纤维膜空气过滤性能实验研究

利用静电纺丝法制备了表面静态接触角为23.6°的具有亲水功能的PAN/PVP复合纳米纤维膜、接触角为81.2°的PAN纳米纤维膜、接触角为131.9°的具有疏水功能的PAN/PVDF复合纳米纤维膜。利用自行搭建的空气过滤实验台,在40%、55%、70%三种相对湿度下对三种纳米纤维膜进行空气过滤实验,对纳米纤维膜的过滤效率、阻力损失及品质因子进行分析。结果表明：三种纳米纤维膜的过滤效率随着相对湿度的增大而升高,PAN/PVP膜和PAN膜的阻力损失随着相对湿度的增大而增加,PAN/PVDF的阻力损失随着相对湿度的增大而减小;PAN/PVP膜和PAN膜的品质因子随着相对湿度的增大而减小,PAN/PVDF膜的品质因子随着相对湿度的增大而增大,湿度越大,PAN/PVDF纳米纤维膜的过滤性能越显著。     

TiO_2-β/SBA-15复合分子筛光催化氧化脱硫

利用过饱和浸渍法制备TiO_2-β/SBA-15复合分子筛,通过XRD、SEM-EDS对复合分子筛进行表征,并将其应用于静态光催化氧化柴油脱硫实验。提出了光催化氧化脱硫的反应机理,并通过GC/AED检测器与Ba(NO_3)_2滴定实验证明了反应机理。考察了催化剂质量浓度、n(H_2O_2)/n(S)、反应温度和反应时间对静态光催化氧化脱硫实验的影响。实验结果表明,TiO_2-β/SBA-15复合分子筛具有良好的催化反应性能,当催化剂质量浓度为4 g/L、n(H_2O_2)/n(S)为2.5、反应温度为60℃、反应时间为3 h时,模拟柴油的脱硫率高达92.3%。     

室内甲醛的真空紫外-光催化降解实验研究

对真空紫外-光催化(VUV-TiO_2/UV)在较高流速(0.30～0.94 m/s)和不同相对湿度(30%～80%)条件下动态去除室内典型浓度的甲醛(<0.624 mg/m~3)进行了实验研究,并与真空紫外(VUV)和光催化(TiO_2/UV)的降解进行了比较。基于净化器串联效率模型,通过比较去除率的实验值和计算值考察了 VUV 和 TiO_2/UV 之间的复合或协同效应。结果表明,TiO_2/UV 和 VUV 能够形成优势互补,TiO_2/UV 对甲醛的一次性去除率相对较低,而 VUV 提高了 TiO_2/UV 对甲醛的去除率,低浓度时效果更加显著;同时 TiO_2/UV 能够高效去除 VUV 产生的臭氧,当反应器内空气流速大于0.6 m/s 时,VUV-TiO_2/UV 的臭氧出口浓度在国家标准值之下。VUV 和 TiO_2/UV 之间存在着微弱的复合效应。     

TiO_2/还原氧化石墨烯纳米复合物的电致化学发光性能研究

采用水热法还原氧化石墨烯的同时与TiO_2纳米粒子复合,制备TiO_2/还原氧化石墨烯纳米复合物,并在玻碳电极表面成膜。研究了膜稳定剂、复合比例、电势扫描范围及检测液pH对TiO_2/还原氧化石墨烯纳米复合物膜电致化学发光性能的影响。结果表明,Nafion作为膜稳定剂时,TiO_2/还原氧化石墨烯纳米复合物(1 wt%)膜能产生强的电致化学发光,强度是TiO_2纳米粒子膜发光强度的8倍。并且,复合物膜的电致化学发光峰电势和起置电势均明显正移。复合物膜在pH8~10范围内具有强的电致化学发光。     

Direct observation of freeze-thaw instability of latex coatings via high pressure freezing and cryogenic SEM

Despite its industrial importance, the subject of freeze-thaw (F/T) stability of latex coatings has not been studied extensively. There is also a lack of fundamental understanding about the process and the mechanisms through which a coating becomes destabilized. High pressure (2100 bar) freezing fixes the state of water-suspended particles of polymer binder and inorganic pigments without the growth of ice crystals during freezing that produce artifacts in direct imaging scanning electron microscopy (SEM) of fracture surfaces of frozen coatings. We show that by incorporating copolymerizable functional monomers, it is possible to achieve F/T stability in polymer latexes and in low-VOC paints, as judged by the microstructures revealed by the cryogenic SEM technique. Particle coalescence as well as pigment segregation in F/T unstable systems are visualized. In order to achieve F/T stability in paints, latex particles must not flocculate and should provide protection to inorganic pigment and extender particles. Because of the unique capabilities of the cryogenic SEM, we are able to separate the effects of freezing and thawing, and study the influence of the rate of freezing and thawing on F/T stability. Destabilization can be caused by either freezing or thawing. A slow freezing process is more detrimental to F/T stability than a fast freezing process; the latter actually preserves suspension stability during freezing. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 27–29, 2004 in Chicago, IL. Tied for first place in The John A. Gordon Best Paper Competition.     

Insect antifeedant properties of anthranoids from the genusVismia

Vismiones and ferruginins, representatives of a new class of lypophilic anthranoids from the genusVismia were found to inhibit feeding in larvae of species ofSpodoptera, Heliothis, and inLocusta migratoria.     

Many Drugs of Abuse May Be Acutely Transformed to Dopamine,Norepinephrine and Epinephrine In Vivo

It is well established that a wide range of drugs of abuse acutely boost the signaling of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, where norepinephrine and epinephrine are major output molecules. This stimulatory effect is accompanied by such symptoms as elevated heart rate and blood pressure, more rapid breathing, increased body temperature and sweating, and pupillary dilation, as well as the intoxicating or euphoric subjective properties of the drug. While many drugs of abuse are thought to achieve their intoxicating effects by modulating the monoaminergic neurotransmitter systems (i.e., serotonin, norepinephrine, dopamine) by binding to these receptors or otherwise affecting their synaptic signaling, this paper puts forth the hypothesis that many of these drugs are actually acutely converted to catecholamines (dopamine, norepinephrine, epinephrine) in vivo, in addition to transformation to their known metabolites. In this manner, a range of stimulants, opioids, and psychedelics (as well as alcohol) may partially achieve their intoxicating properties, as well as side effects, due to this putative transformation to catecholamines. If this hypothesis is correct, it would alter our understanding of the basic biosynthetic pathways for generating these important signaling molecules, while also modifying our view of the neural substrates underlying substance abuse and dependence, including psychological stress-induced relapse. Importantly, there is a direct way to test the overarching hypothesis: administer (either centrally or peripherally) stable isotope versions of these drugs to model organisms such as rodents (or even to humans) and then use liquid chromatography-mass spectrometry to determine if the labeled drug is converted to labeled catecholamines in brain, blood plasma, or urine samples.     

Ethanol and (−)-α-Pinene: Attractant Kairomones for Bark and Ambrosia Beetles in the Southeastern US

In 2002–2004, we examined the flight responses of 49 species of native and exotic bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae) to traps baited with ethanol and/or (−)-α-pinene in the southeastern US. Eight field trials were conducted in mature pine stands in Alabama, Florida, Georgia, North Carolina, and South Carolina. Funnel traps baited with ethanol lures (release rate, about 0.6 g/day at 25–28°C) were attractive to ten species of ambrosia beetles (Ambrosiodmus tachygraphus, Anisandrus sayi, Dryoxylon onoharaensum, Monarthrum mali, Xyleborinus saxesenii, Xyleborus affinis, Xyleborus ferrugineus, Xylosandrus compactus, Xylosandrus crassiusculus, and Xylosandrus germanus) and two species of bark beetles (Cryptocarenus heveae and Hypothenemus sp.). Traps baited with (−)-α-pinene lures (release rate, 2–6 g/day at 25–28°C) were attractive to five bark beetle species (Dendroctonus terebrans, Hylastes porculus, Hylastes salebrosus, Hylastes tenuis, and Ips grandicollis) and one platypodid ambrosia beetle species (Myoplatypus flavicornis). Ethanol enhanced responses of some species (Xyleborus pubescens, H. porculus, H. salebrosus, H. tenuis, and Pityophthorus cariniceps) to traps baited with (−)-α-pinene in some locations. (−)-α-Pinene interrupted the response of some ambrosia beetle species to traps baited with ethanol, but only the response of D. onoharaensum was interrupted consistently at most locations. Of 23 species of ambrosia beetles captured in our field trials, nine were exotic and accounted for 70–97% of total catches of ambrosia beetles. Our results provide support for the continued use of separate traps baited with ethanol alone and ethanol with (−)-α-pinene to detect and monitor common bark and ambrosia beetles from the southeastern region of the US.     

Novel polyurethane coating technology through glycidyl carbamate chemistry

Glycidyl carbamate chemistry combines the excellent properties of polyurethanes with the crosslinking chemistry of epoxy resins. Glycidyl carbamate functional oligomers were synthesized by the reaction of polyfunctional isocyanate oligomers and glycidol. The oligomers were formulated into coatings with several amine functional crosslinkers at varying stoichiometric ratios and cured at different temperatures. Properties such as solvent resistance, hardness, and impact resistance were dependent on the composition and cure conditions. Most coatings had an excellent combination of properties. Studies were carried out to determine the kinetics of the curing reaction of the glycidyl carbamate functional oligomers with multifunctional and model amines. Detailed kinetic analysis of the curing reactions was also undertaken. The results indicated that the glycidyl carbamate functional group is more reactive than a glycidyl ether group. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, on October 27–29, 2004, in Chicago, IL.     

Highly moisture-proof polysilsesquioxane coating prepared via facile sol-gel process

A highly moisture-proof polysilsesquioxane coating was obtained from a new bis-silylated precursor, which was synthesized from 3-aminopropyltriethoxysilane (APTES) and m-xylylene diisocyanate (m-XDI) in tetrahydrofuran (THF) and verified by ¹H MAS NMR. For direct comparison purposes, an SiO₂ coating was also prepared by the Stöber method using tetraethoxysilane (TEOS) as the reactant. Interestingly, the coating obtained from the polysilsesquioxane sol exhibited a much higher moisture resistance capability than its counterpart, which was attributed to its more compact feature between nanoparticles as characterized by N₂ absorption experiment and transmission electron microscopy (TEM). Furthermore, its high transparency of about 92% showed potential for application in the protection of optical crystals.