An investigation into transition metal ion binding properties of silk fibers and particles using radioisotopes

Silk is a structural protein fiber that is stable over a wide pH range making it attractive for use in medical and environmental applications. Variation in amino acid composition has the potential for selective binding for ions under varying conditions. Here we report on the metal ion separation potential of Mulberry and Eri silk fibers and powders over a range of pH. Highly sensitive radiotracer probes, ⁶⁴Cu²⁺, ¹⁰⁹Cd²⁺, and ⁵⁷Co²⁺ were used to study the absorption of their respective stable metal ions Cu²⁺, Cd²⁺, and Co²⁺ into and from the silk sorbents. The total amount of each metal ion absorbed and time taken to reach equilibrium occurred in the following order: Cu²⁺ > Cd²⁺ > Co²⁺. In all cases the silk powders absorbed metal ions faster than their respective silk fibers. Intensive degumming of the fibers and powders significantly reduced the time to absorb respective metal ions and the time to reach equilibrium was reduced from hours to 5–15 min at pH 8. Once bound, 45–100% of the metal ions were released from the sorbents after exposure to pH 3 buffer for 30 min. The transition metal ion loading capacity for the silk sorbents was considerably higher than that found for commercial ion exchange resins (AG MP‐50 and AG 50W‐X2) under similar conditions. Interestingly, total Cu²⁺ bound was found to be higher than theoretically predicted values based on known specific Cu²⁺ binding sites (AHGGYSGY), suggesting that additional (new) sites for transition metal ion binding sites are present in silk fibers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

椰壳纤维制备活性炭纤维的研究

本文以椰壳纤维为原料,采用正交试验方法研究了(NHe)2HPO4作为活化剂,经预处理、炭化和活化过程制备活性炭纤维,其比表面积达到1268.1 m2.g-1,含有一定量的中孔孔结构,主要集中在2～4nm.通过对比分析,得出了各反应条件对反应产物性能的影响,并对活化机理进行了分析.     

原位聚合连续纤维增强聚甲基丙烯酸甲酯复合材料的界面及性能研究

通过选用含不同官能团的硅烷偶联剂3-甲基丙烯酰氧丙基三甲氧基硅烷(MPS)、γ-氨丙基三甲氧基硅烷(APS)和γ-氯丙基三甲氧基硅烷(CPS)处理玻璃纤维,然后通过原位聚合的方法制造了连续纤维增强的聚甲基丙烯酸甲酯(PMMA)复合材料。研究结果表明,经过这三种偶联剂处理的玻璃纤维与基体树脂在界面分别形成了化学键、范德华力和氢键。红外、动态力学分析和扫描电镜研究表明,复合材料的界面粘接强度顺序为:MPS>CPS>APS。MPS处理的复合材料具有最高的弯曲强度,而CPS处理的复合材料具有最佳的冲击韧性和断裂伸长率。     

棉皮纤维增强聚丁二酸丁二醇酯复合材料的热性能及力学性能研究

采用连续式蒸汽爆破法对棉皮纤维进行预处理,将其与聚丁二酸丁二醇酯(PBS)进行共混,制备了PBS/棉皮纤维复合材料。利用扫描电镜对棉皮纤维及PBS/棉皮纤维复合材料的微观形貌进行了分析,并研究了棉皮纤维含量对PBS/棉皮纤维复合材料熔融及结晶行为、热降解性能、热变形温度以及力学性能的影响。结果表明:经蒸汽爆破处理后,棉皮纤维直径变小,比表面积变大,在PBS基体中分散均匀;棉皮纤维的存在改变了PBS的熔融峰值温度,提高了其结晶度;与纯PBS相比,PBS/棉皮纤维复合材料在高温条件下的热稳定性得到改善维,卡软化温度和弯曲强度提高。     

Modeling of dimensional variations of a dune sand concrete reinforced by addition of steel fibers

Technically, the dune sand concrete (DSC) can replace the traditional concrete in some construction cases. Even economically, this material is also cheaper, since dune sand (with its large availability in the Saharan regions), is used as a single aggregate. In addition, the incorporation of steel fibers into this material can remedy its brittle behaviour and limit the microcracking caused by the high shrinkage that typically characterizes the sand concrete. Moreover, the use of the experimental design approach to model the influence of the fibers content [Vb], the filler content [LF] and the Water/Cement ratio [W/C] on the shrinkage is very attractive.

For this, tests of endogenous shrinkage (ES) and the free shrinkage (FS) were carried out on various compositions of dune sand concrete reinforced by steel fibers (FRDSC). The results are then compared with those of the dune sand concrete (DSC) taken as a concrete control. Generally, the addition of steel fibers significantly reduces the shrinkage of the dune sand concrete. At the young age, only small differences were observed when fiber contents passed from a dosage to another; however, at the long term, the fibers effect became more marked. In addition, the use of the experimental design theory was very beneficial for modeling the effect of the studied factors on the studied responses. Although [LF] and [W/C] also significantly influenced the total shrinkage of RFDSCs, [Vb] showed the greatest effect. The recorded optimums in the study field were 0.6, 200?kg/m³ and 1% were for [W/C], [LF] and [Vb] respectively.     

CO2 plasma modification of high-modulus carbon fibers and their adhesion to epoxy resins

Interfacial bond strength is often a performance-limiting factor of carbon-fiber-reinforced composites. This limitation is most prevalent when higher-modulus fibers or relatively unreactive matrix resins, such as engineering thermoplastics or high-temperature thermoset resin systems, are used. Radio-frequency (RF) glow discharge plasmas are an effective means of modifying carbon-fiber surface chemical characteristics to promote adhesion. It has been previously shown that oxidizing plasmas are especially effective compared with electro-oxidative treatments for treating carbon fiber surfaces as revealed by titrations, electron spectroscopy, wetting, and inverse gas chromatography measurements. This study evaluated the effectiveness of CO₂ plasmas on two experimental high-modulus carbon/graphite fibers and correlated the plasma surface modification with interfacial adhesion in an epoxy matrix composite system. The results show that CO₂ plasma treatment increased the surface oxygen content by nearly a factor of 2 over typical electro-oxidation treatments. The increased oxygen is mainly in the form of hydroxyl, ketone, and carboxyl-like moieties. Unidirectional composites were prepared from as-received and plasma-modified versions of each type of experimental fiber. The composites containing plasma-modified filaments exhibited 1.5-3.0 times the strength of composites fabricated with untreated or electro-oxidized filaments in transverse-flexural tests. Short-beam shear strength increased by two times over those with as-produced filaments and is equivalent to that of composites containing electro-oxidized filaments.     

Anisotropic alignment of nickel particles in a magnetic field for electronically conductive adhesives applications

Anisotropically conductive adhesives were developed by magnetic alignment of conductive nickel particles in a non-conductive epoxy matrix. Conductivity occurs in the direction of the magnetic field applied to the adhesive film. The effects of magnetic and conducting nickel filler type (i.e. powders, filaments, flakes, and fibers), resin viscosity, and the magnitude of aligning magnetic field on the electrical properties of the resulting anisotropic adhesive were investigated. The electrical resistance of the anisotropic adhesive was measured using the four-point probe method. The resistance of the filled adhesive decreased with increasing viscosity and the intensity of the magnetic field.     

Effect of polycrystalline mullite fibers on the properties of vitrified bond and vitrified CBN composites

The effect of polycrystalline mullite fibers (PMFs) on the properties of vitreous bonds and vitrified CBN composites was investigated. The results show that the addition of PMFs can increase the porosity of composites and reduce the fluidity of binders. The vitrified composites incorporating 6.4 wt% PMFs display excellent mechanical strength, which is enhanced by 21.2% compared with that of composites without PMFs sintered at the optimal sintering temperature. Meanwhile the thermal expansion coefficient of vitrified bond reduces from 6.256×10⁻⁶ °C⁻¹ to 4.805×10⁻⁶ °C⁻¹ with increasing fraction of PMFs. The improvement of mechanical strength is associated with the change of cracking mechanisms of the composites with fibrous crystals and the existence of several observed mechanisms, including fiber pull-out, fiber bridging and rupture.     

Separate Bleaching of Pulp Fractions Enriched in Earlywood and Latewood Fibers

Abstract

Unbleached softwood kraft pulp was fractionated in hydrocyclones into a fine fraction, enriched in earlywood fibers, and a coarse fraction, enriched in latewood fibers. The response to individual bleaching chemicals and the bleachability in bleaching sequences of the pulp fractions was studied.

The light absorption coefficient, light scattering coeffient, and brightness were higher in the unbleached fine fraction than in the coarse fraction. Hydrogen peroxide managed to reduce the light absorption coefficient of the earlywood enriched fine fraction more efficiently than that of the latewood enriched fraction.

In the TCF‐sequence the light absorption coefficient of the fine fraction was reduced to the level of the coarse fraction at a given consumption of bleaching chemicals. In the ECF‐sequence the difference in light absorption coefficient remained between the fractions. At a given consumption of bleaching chemicals, the fine fraction had higher brightness than the coarse fraction, 2%‐ and 1%‐units on the ISO‐scale in the TCF and ECF bleaching sequence, respectively.     

铝盐掺杂TiO2棒状纤维的制备及其室温NOx气敏性

以钛酸四丁酯为钛源、Al(NO3)3为铝盐,采用静电纺丝法在600℃焙烧条件下制备出铝盐掺杂TiO2棒状纤维.利用扫描电子显微镜、透射电子显微镜和X射线衍射仪等对纤维的形貌和组成进行了表征.研究了室温下铝盐掺杂TiO2纤维对NOx的气体敏感性能,并对其气敏机理进行了分析.结果表明:铝盐掺杂TiO2纤维为一维棒状结构,直径约为200nm.在室温条件下对NOx有较好的气敏响应,响应时间最短为6s,最低检测体积分数可达9.7×10-7.锐钛矿相的存在有利于NOx的吸附-脱附.铝盐掺杂TiO2纤维大幅提高了对NOx的气敏响应灵敏度,是一种在室温条件下极具潜力的气敏材料.