PAN基碳纳米多孔纤维的制备及吸附性能研究

以聚丙烯腈(PAN)和醋酸锌(Zn(CH3COO)2.2H2O)为溶质,N-N二甲基甲酰胺(DMF)为溶剂,采用静电纺丝法成功制备PAN/醋酸锌纳米纤维毡,并探讨醋酸锌含量(相对于PAN)对纳米纤维毡形貌和直径的影响。对PAN/醋酸锌纳米纤维毡进行预氧化、活化、碳化处理,制备得到碳纳米多孔纤维,并对其得率、孔径分布、比表面积及吸附性能进行研究。实验结果显示:预氧化温度的升高使碳纳米多孔纤维的吸附指标先增后减;在600℃~1 000℃的碳化温度范围内,碳化温度的升高使碳纳米多孔纤维的吸附性能均呈现上升趋势,且在1 000℃时达到最大。     

静电纺聚丙烯腈纳米纤维毡的炭化

用静电纺丝的方法制得聚丙烯腈纳米纤维,并在250℃预氧化,850℃炭化,得到碳纳米纤维。对静电纺纳米纤维、预氧化后纳米纤维和炭化后纳米纤维的表面形态结构用扫描电镜进行分析,并比较其强伸、导电性能,发现碳纳米纤维的导电性能大大增强。原料聚丙烯腈粉末、静电纺纳米纤维、预氧化后纳米纤维和炭化后纳米纤维的内部结构变化采用X射线衍射和红外光谱法进行分析。     

高分子质量聚丙烯腈基碳纳米纤维的制备

为获得力学性能较好的聚丙烯腈(PAN)基实心和多孔碳纳米纤维,以自制相对分子质量30万的PAN为原料,利用静电纺丝技术制备了PAN和PAN/聚甲基丙烯酸甲酯纳米纤维,经预氧化、碳化后分别获得了新型纳米纤维。利用扫描电镜观测了纳米纤维和碳纳米纤维的表面形态,并对纳米纤维和碳纳米纤维的直径分布进行了表征。结果表明:相对分子质量为30万的PAN适宜纺丝质量分数为6%,PAN纳米纤维的平均直径为1 242 nm。在PAN纺丝液中加入PMMA后,纳米纤维的平均直径下降至519 nm,且直径分布变窄;预氧化过程中施加张力可以使碳纳米纤维保持较好的纤维形状;碳化处理后的PAN和PAN/PMMA纳米纤维的直径都明显减小,前者减小为683 nm,后者为374 nm;扫描电镜照片显示,加入PMMA后PAN碳纳米纤维呈多孔结构。     

沥青和PAN的静电纺碳纳米级纤维膜的制备及表征

利用N,N-二甲基甲酰胺(DMF)为溶剂、滚轴为接收装置,通过静电纺丝法制备聚丙烯腈(PAN)和可纺沥青(SP)共混前驱体纳米级纤维膜,再对其进行预氧化和碳化,制备碳纳米级纤维膜,以有效降低碳纤维生产成本.结果 表明:在保持纺丝液质量浓度不变的条件下,纤维直径随SP质量分数的增大而减小.制得的纳米级纤维膜具有一定取向度,且经预氧化和碳化处理后,纳米级纤维膜的取向度得到提升;碳化后,沿纤维取向方向的电导率约为垂直于纤维取向方向的3倍.预氧化过程中,纳米级纤维膜因纤维大分子上形成醚键和羰基而质量增加,后又因交联和环化而质量减少.预氧化后,-C≡N环化为C=N,分子结构变得更规整,且颜色发生变化.碳化后,纤维中C元素质量分数达96.89％,结晶度比前驱体纤维高出9.94％.     

静电纺聚丙烯腈/石墨烯碳纳米纤维的结构与性能

为研究石墨烯和不同预氧化条件对碳纳米纤维结构的影响,采用静电纺丝法制备了聚丙烯腈（PNA）/ 石墨烯纳米纤维,然后通过预氧化和炭化处理获得碳纳米纤维。借助傅里叶红外变换光谱仪、X 射线衍射仪、差示扫描量热仪、激光显微拉曼光谱仪和扫描电子显微镜研究预氧化丝和碳纳米纤维的结构变化。结果表明：预氧化处理过程中,PNA分子发生脱氢、环化和氧化反应,最终形成稳定的梯形结构;随着预氧化温度的升高,PNA 纤维的相对环化率、芳构化指数和环化度逐渐提高;石墨烯的加入提高了碳纳米纤维的石墨化程度,对脱氢、环化反应有一定的抑制作用,从而降低碳纳米纤维的断裂程度;当预氧化温度为260 ℃时,新的纤维结构已基本形成。     

TiO2/PAN碳化纳米纤维膜的制备及其对腐殖酸的降解效果

以丙烯腈为原料自制聚丙烯腈(PAN)粉末,静电纺丝法制备PAN纳米纤维,采用溶胶-凝胶法负载TiO2,制备TiO2/PAN碳化纳米纤维膜.通过SEM、DG-DTG及元素分析等方法对纳米纤维进行表征.研究结果表明,用PAN质量分数为3%的纺丝液进行静电纺丝,在预氧化温度280℃及碳化温度550℃条件下可制得直径100～1...     

深冷处理温度对锡锑/碳纳米纤维负极材料锂电性能的影响

为提高锡锑/碳(SnSb/C)纳米纤维作为负极材料的锂电池的循环使用性能,利用深冷处理对SnSb/C纳米纤维进行形貌再造,比较不同深冷温度处理前后纳米纤维的形貌变化,并测试其含碳量和比表面积,通过分析电池的恒流充放电曲线研究深冷处理温度的变化对其电化学性能的影响。结果表明:当深冷处理温度为 -100 ℃时,SnSb/C纳米纤维表面粗糙度增加并出现沟壑;深冷处理加快了聚丙烯腈的预氧化反应速度,使其分解温度提前,含碳量高达75.4%,比表面积为214.0 m²/g;锂电循环过程中,因深冷处理对其形貌结构的影响,电池容量呈持续上升趋势,循环120圈后容量保持率为123.5%。     

碳纳米纤维纱的制备及表征

利用自制的静电纺装置制备了PAN纳米纤维纱,然后通过预氧化和碳化工艺得到碳纳米纤维纱,利用SEM、X-衍射和激光拉曼光谱表征了其形貌和结构,并测试了其力学性能。结果表明,经预氧化和碳化得到的碳纳米纤维纱纤维直径和纱线直径均有所减小,但成纱表面仍具有均匀的捻回分布,部分纤维之间有黏结现象并发生断裂。碳纳米纤维纱的分子结构为碳-碳双键连接的网状结构,纤维中存在乱层状的石墨结构。碳化后的纳米纤维纱的断裂强力与断裂伸长率较炭化前的PAN原纱有所降低。     

含铁杂化碳纳米纤维的制备及其在吸附铜离子上的应用

利用PAN与氯化铁的共混溶液进行静电纺丝,经预氧化和碳化得到了掺杂和未掺杂铁的碳纳米纤维。利用SEM和EDS表征了纤维形貌和组成,测试了其力学性能,并研究了杂化碳纳米纤维对Cu~(2+)吸附性能的影响。结果表明,随着纺丝液中铁含量的增加,纤维的平均直径和断裂强度逐渐减小。掺杂铁的碳纳米纤维与未掺杂的碳纳米纤维相比,其对Cu~(2+)的吸附性能显著提高。     

静电纺丝:聚丙烯腈炭化制备碳纳米纤维

用静电纺丝的方法制得聚丙烯腈纳米纤维,并在250℃下预氧化,850℃下炭化,得到碳纳米纤维.用扫描电镜观察了静电纺纳米纤维、预氧化后的纳米纤维和炭化后的纳米纤维表面形态结构的变化,采用X射线衍射和红外光谱法分析了原料聚丙烯腈粉末、静电纺纳米纤维、预氧化后的纳米纤维和炭化后的纳米纤维内部结构的变化.     

Textural Properties of Cold-set Gels Induced from Heat-denatured Whey Protein Isolates

A 9% whey protein (WP) isolate solution at pH 7.0 was heat-denatured at 80°C for 30 min. Size-exclusion HPLC showed that native WP formed soluble aggregates after heat-treatment. Additions of CaCl2 (10–40 mM), NaCl (50–400 mM) or glucono-delta-lactone (GDL, 0.4–2.0%, w/v) or hydrolysis by a protease from Bacillus licheniformis caused gelation of the denatured solution at 45°C. Textural parameters, hardness, adhesiveness, and cohesiveness of the gels so formed changed markedly with concentration of added salts or pH by added GDL. Maximum gel hardness occurred at 200 mM NaCl or pH 4.7. Increasing CaCl2 concentration continuously increased gel hardness. Generally, GDL-induced gels were harder than salt-induced gels, and much harder than the protease-induced gel.     

Occurrence of bisphenol-F-diglycidyl ether (BFDGE) in fish canned in oil

The levels of bisphenol-F-diglycidyl ether (BFDGE) were quantified as part of a European survey on the migration of residues of epoxy resins into oil from canned fish. The contents of BFDGE in cans, lids and fish collected from all 15 Member States of the European Union and Switzerland were analysed in 382 samples. Cans and lids were separately extracted with acetonitrile. The extraction from fish was carried out with hexane followed by re-extraction with acetonitrile. The analysis was performed by reverse phase HPL C with fluorescence detection. BFDGE could be detected in 12% of the fish, 24% of the cans and 18% of the lids. Only 3% of the fish contained BFDGE in concentrations considerably above 1mg/kg. In addition to the presented data, a comparison was made with the levels of BADGE (bisphenol-A-diglycidyl ether)analysed in the same products in the context of a previous study.     

Contribution of European research to risk analysis

The European Commission's, Quality of Life Research Programme, Key Action 1—Health, Food & Nutrition is mission-oriented and aims, amongst other things, at providing a healthy, safe and high-quality food supply leading to reinforced consumer confidence in the safety of European food. Its objectives also include the enhancing of the competitiveness of the European food supply. Key Action 1 is currently supporting a number of different types of European collaborative projects in the area of risk analysis. The objectives of these projects range from the development and validation of prevention strategies including the reduction of consumers risks; development and validation of new modelling approaches; harmonization of risk assessment principles, methodologies, and terminology; standardization of methods and systems used for the safety evaluation of transgenic food; providing of tools for the evaluation of human viral contamination of shellfish and quality control; new methodologies for assessing the potential of unintended effects of genetically modified (genetically modified) foods; development of a risk assessment model for Cryptosporidium parvum related to the food and water industries; to the development of a communication platform for genetically modified organism, producers, retailers, regulatory authorities and consumer groups to improve safety assessment procedures, risk management strategies and risk communication; development and validation of new methods for safety testing of transgenic food; evaluation of the safety and efficacy of iron supplementation in pregnant women; evaluation of the potential cancer-preventing activity of pro- and pre-biotic ('synbiotic') combinations in human volunteers. An overview of these projects is presented here.     

低温带皮菜籽粕微粉的不同粒级部分的功能特性

为研究低温带皮菜籽粕微粉的不同粒级部分的功能特性,以经低温脱脂的带皮菜籽粕为原料,经微粉碎后筛分成212~425μm、150~212μm和106~150μm的3个不同粒级的微粉样品,检测这些样品的吸水性、吸油性、乳化性和乳化稳定性、蛋白质体外消化率。结果表明:1 3个不同粒级的微粉样品之间的粗纤维含量存在显著差异,表明三者的结构组成成分有一定差异。23个微粉样品的乳化活性和乳化稳定性随粒度级别的减小而显著增加(P0.01)。33个微粉样品的蛋白质体外消化率随粒度级别的减小而显著增加(P0.01)。4不同粒级带皮菜籽粕微粉样品的吸水性与吸油性受其结构组成物质不同和粒度的双重影响,与粒度的相关性不明显。     

Microbiology of food taints

Fresh and processed foods are often spoilt by the presence of undesirable flavours and odours caused by microbial action. The aim of this paper is to review the current knowledge of microbiologically induced taints that occur in a wide range of foodstuffs, including meats, poultry, fish, crustaceans, milk, dairy products, fruits, vegetables, cereals and cereal products. Examples have been chosen where the compounds responsible for the taint have been identified and sufficient data obtained to demonstrate the involvement of microorganisms. However, in some cases the full identity of the causative organism may not have been elucidated. The types of microorganisms covered by this review include bacteria, fungi, yeasts, actinomycetes and cyanobacteria. Although cyanobacteria do not in general infect foods, their presence in aqueous systems and water supplies can lead to off-flavours in aquatic organisms and processed foodstuffs. Several examples of each of these processes are discussed. Wherever possible, the likely biosynthetic pathway used by the microorganism to produce the offending compound in a foodstuff is indicated.     

Analysis for organic residues from aids to polymerization used to make plastics intended for food contact

Polymers intended for food contact use have been analysed for organic residues which could be attributed to a range of substances employed as polymerization aids (e.g. initiators and catalysts). A wide range of polymers was extracted with solvents and the extracts analysed by gas chromatography-mass spectrometry (GC-MS). The overwhelming majority of substances identified were not derived from aids to polymerization but were oligomers, additives and adventitious contaminants. However, a small number of substances were identified as initiator residues. These included tetramethylsuccinonitrile (TMSN) which was observed in two polymers and it derived from recombination of two azobisisobutyronitrile (AIBN) initiator radicals. Methyl benzoate, benzoic acid, biphenyl and phenyl benzoate were detected in one poly(methyl methacrylate) sample and in two polyvinylchlorides and they are thought to be derived from benzoyl peroxide initiator. TMSN was subsequently targeted for analysis of poly-(methyl methacrylate) plastics using proton nuclear magnetic resonance spectrometry (¹     

Tests of potential functional barriers for laminated multilayer food packages. Part II: Medium molecular weight permeants

Experiments were performed to characterize the kinetics of the permeation of different medium molecular weight model permeants: bisphenol A, warfarin and anthracene, from liquid paraffin, through a surrogate potential functional barrier (25 microns-thick orientated polypropylene--OPP) into the food simulants olive oil and 3% (w/v) acetic acid. The characterization of permeation kinetics generally observed the permeation models previously reported to explain the experimental permeation results obtained for a low molecular weight group of model permeants. In general, the model permeants exhibited behaviour consistent with their relative molecular weights with respect to (a) the time taken to attain steady-state permeation into the food simulant in which they were more soluble, (b) their subsequent steady-state permeation rates, and (c) their partition between liquid paraffin and the OPP membrane.     

The development of reference materials for paralytic shellfish poisoning toxins in lyophilized mussel. I: Interlaboratory studies of methods of analysis

This paper describes the first part of a project undertaken to develop mussel reference materials for Paralytic Shellfish Poisoning (PSP) toxins. Two interlaboratory studies were undertaken to investigate the performance of the analytical methodology for several PSP toxins, in particular saxitoxin (STX) and decarbamoyl-saxitoxin (dc-STX) in lyophilized mussels, and to set criteria for the acceptance of results to be applied during the second part of the project: the certification exercise. In the first study, 18 laboratories were asked to measure STX and dc-STX in rehydrated lyophilized mussel material and to identify as many other PSP toxins as possible with a method of their choice. In the second interlaboratory study, 15 laboratories were additionally asked to determine quantitatively STX and dc-STX in rehydrated lyophilized mussel and in a saxitoxin-enriched mussel material. The first study revealed that three out of four postcolumn derivatization methods and one pre-column derivatization method sufficed in principle to determine STX and dc-STX. Most participants (13 of 18) obtained acceptable calibration curves and recoveries. Saxitoxin was hardly detected in the rehydrated lyophilized mussels and results obtained for dc-STX yielded a CV of 58% at a mass fraction of 1.86 mg/kg. Most participants (14 out of 18) identified gonyautoxin-5 (GTX-5) in a hydrolysed extract provided. The first study led to provisional criteria for linearity, recovery and separation. The second study revealed that 6 out of 15 laboratories were able to meet these criteria. Results obtained for dc-STX yielded a CV of 19% at a mass fraction of 3.49mg/kg. Results obtained for STX in the saxitoxin-enriched material yielded a CV of 19% at a mass fraction of 0.34mg/kg. Saxitoxin could not be detected in the PSP-positive material. Hydrolysis was useful to confirm the identity of GTX5 and provided indicative information about C1 and C2 toxins in the PSP-positive material. The methods used in the second interlaboratory study showed sufficiently consistent analysis results to undertake a certification exercise to assign certified values for STX and dc-STX in lyophilized mussel.     

The Ministry of Environmental Protection Issued "Feasible Technology Guidelines for Pollution Prevention and Control in Wood Pulping Process of the Paper Industry (Trial)" and Two Other Guiding Technical Documents

On December 27t＂, 2013, the Ministry of Environmenta Protection announced that, in order to implement ＂The Environmental Protection Law of the People＇ s Republic of China＂, improve the working system in environmenta protection technologies, and promote technologica advancement in pollution prevention, the Ministry of Environmental Protection sponsored the formulation of three guiding technical documents including ＂Feasible Technology Guidelines for Pollution Prevention and Contro n Wood Pulping Process of the Paper Industry （Trial）＂     

1~(st) Intelli-Tissue~ EcoEc Tissue Machine Supplied by PMP Group Successfully Put into Operation in China

正On April 29th,2014,Intelli-Tissue EcoEc tissue machine supplied by PMP Group successfully put into operation at Hebei Xuesong Paper Co.,Ltd.,this is the first such kind of paper machine of PMP Group in China.