Improved surface properties of CTMP fibers with enzymatic pretreatment of wood chips prior to refining

Surface properties of chemithermomechanical pulp (CTMP) fibers produced from enzymatically pretreated eucalyptus wood chips prior to refining were investigated by Field Emission Scanning Electron Microscope (FE-SEM), Transmission Electron Microscope (TEM) and X-ray Photoelectron Spectroscopy (XPS). The results showed that in a traditional CTMP refining process most fiber disruptions occur in the middle lamella (ML) leaving behind a significant amount of hydrophobic materials on the resulting fiber surface. However, in a Bio-CTMP refining process, fiber fractures preferentially take place in the primary (P) and secondary 1 (S1) layers or the S1 and secondary 2 (S2) layers, which results in more fibrillation being generated in the subsequent refining thus improving inter-fiber bonding strength and paper strength. XPS chemical composition analysis together with pulp physical strength property showed that the surfaces of Bio-CTMP fibers become enriched with a greater proportion of carbohydrates in comparison with CTMP fiber surface, which supports FE-SEM and TEM observations.     

Effect of on-line ultrasonic treatment on the properties of carbon fiber reinforced plastic composites

The strength, performance, and application of carbon fiber reinforced plastic (CFRP) composites are directly affected by the interfacial bonding between fiber and resin. Wet winding technology is a commonly used composite productive process, and improving interfacial bonding of composites by on-line treatment has always been the focus of attention. In this paper, an on-line ultrasonic treatment system is designed and realized, the resin content of prepregs is determined by the dissolution method; standard deviation and dispersion coefficient are also calculated. The surface morphology, internal structure of prepregs, and the component of resin are observed and analyzed using a Metallurgical Microscope, scanning electron microscope (SEM), and near infrared radiation spectra (NIRS). The strength and performance of prepregs [(tensile strength, bending strength, tensile modulus of elasticity, bending modulus of elasticity, and interlaminar shear strength (ILSS)] are also tested. The results show the on-line ultrasonic treatment system can effectively improve the interfacial bonding of CFRP composites and enhance the strength and performance of CFRP composites.     

聚合物纳米粒子的制备及其新型物理水凝胶结构的AFM和SEM研究

凝胶材料是生物系统的重要组成物质,在生物模拟、仿生等方面具有重大意义.最近凝胶方面的研究日益受到关注^[1,2],高分子凝胶体系的研究也得到深入开展^[3,4].在智能水凝胶、凝胶特性基础研究和医用凝胶材料等领域已取得了较大进展.     

六方相ZnS单晶纳米线束的合成及其光学性质研究

利用丙烯酸和丙烯酸锌的共聚物作为前驱体，硫脲作为硫源，在溶剂热条件下于170 ℃反应96 h得到了ZnS纳米线束。透射电子显微镜(TEM)，选区电子衍射(SAED)和高分辨透射电子显微镜(HRTEM)测试表明这些线束是由单晶纳米线组装而成。该纳米结构具有很好的光学性质。傅立叶变换红外光谱(FTIR)结果证明纳米线被聚合物包裹。此外，对纳米线束的生长机理进行了简要讨论。     

代铬刷镀层的耐腐蚀机理的考察

对新型的代铬刷镀层Ni-Fe-W-P-S进行了耐腐蚀性能机理的分析研究。用扫描电镜(SEM)、透射电镜(TEM)、扫描隧道显微镜(STM)、X射线衍射及电子能谱(XPS)等的分析表明，基体组织为非品结构是代铬刷镀层优异耐腐蚀性的主要原因.     

Banana pulp extract mediated synthesis of Cu2O nanoparticles: An efficient heterogeneous catalyst for the ipso-hydroxylation of arylboronic acids

A green and facile novel procedure has been developed for the synthesis of Cu₂O nanoparticles within a very short reaction time using banana pulp extract as a reducing agent. The synthesized nanoparticles are well characterized by SEM (Scanning Electron Microscope), TEM (Transmission Electron Microscope) and powder XRD (X-ray Diffraction) methods. An environmental benign and highly efficient protocol for the ipso-hydroxylation of aryl and hetero arylboronic acids using bio-fabricated Cu₂O nanoparticles as a catalyst and aqueous H₂O₂ as an oxidant has also been developed. The main advantages of this protocol are the base free reaction condition, reusable and heterogeneous catalytic system, and short reaction time with excellent yields.     

用于扫描探针显微镜研究的原子级平整金基底的制备

报导了一种用于扫描深外显微镜（SPM）研究的原子级平整全基底的制备方法．采用这种方法，得到了25um2范围内，膜的平均粗糙度小平0.4nm的原子级平整基底，并且得到金以（111）面取向在云母表面沉积的实验证据，同时使用电化学循环伏安法和X光电子能谱对这种膜的自组装性能进行了考察．     

Interactions and corrosion mitigation prospective of pyrazole derivative on mild steel in HCl environment

The effectiveness of 1H?pyrazole?3,5?dicarboxylic acid 5?benzyl ester 3?phenyl ester (PCBPE) as a preventer for deterioration of IS 513 Gr. D steel in 1 M HCl medium is evaluated via weight loss, electrochemical impedance, and polarization techniques. Kinetic and thermodynamic parameters assessed the feasibility of the adsorption process at diverse temperatures. The inhibition action on mild steel has been enhanced with increasing PCBPE concentration. It is found from the polarization studies that PCBPE behaves as mixed type inhibitor in HCl medium. The adsorption process of PCBPE on mild steel surface from acid environment is favoured Langmuir adsorption isotherm. The shielding efficiency of PCBPE has been enhanced at elevated concentrations, and it has been diminished at amplified temperatures. The Atomic Force Microscope (AFM), Scanning Electron Microscope (SEM), and Energy Dispersive Spectrum (EDS) were used to establish a surface characterization of metal specimens. A quantum chemical analysis of electron density distributions in the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) demonstrated how the inhibitor undergoes adsorption on mild steel in 1 M HCl. All experimental findings substantiate the corrosion mitigation performance of PCBPE on mild steel in acidic environments.     

Preparation of microplastics with polysulfone and montmorillonite by impregnating aramid and glass fibers

Microplastics have been prepared by impregnating aramid and glass fibers with of polysulfone melts of various viscosities unfilled and filled with montmorillonite. A minimum of the melt viscosity has been found at a montmorillonite content of 1 wt %. Radial-transverse impregnation of multifilament fiber by a thermoplastic melt has been studied by the gravimetric method. Introduction into the polysulfone melt up to 1% of the filler at the initial stage of impregnation have almost no effect on the rate of the process; however, a decrease in it is observed as compared subsequently to impregnation with the melt containing no filler. It has been shown that torsional rigidity of microplastics, along with weight change, characterizes the degree of fiber impregnation.     

The detection of biomarkers in evaporite matrices using a portable Raman instrument under Alpine conditions

The binding of rhodamine 6G and hydroxy propyl β-cyclodextrin (Hβ-CD) was investigated measuring fluorescence and absorption at pH 7.0. The solid inclusion complex of Rh6G and Hβ-CD has been studied by Ultraviolet (UV) spectroscopy, Fluorimetry, Fourier Transform Infrared (FTIR), (1)H Nuclear Magnetic Resonance ((1)HNMR) and in the Scanning Electron Microscope (SEM). Association constant K(g) and K(e) were determined by the enhancement of the fluorescence of rhodamine 6G in the presence of Hβ-CD. Fluorescence of Rh6G is generally enhanced, in complexes of Rh6G and β-Cyclodextrin in aqueous solutions. The free energy change for the ground state (ΔG(g)) and for the excited state (ΔG(e)) have also been determined. The experimental results indicated that the inclusion process is an exothermic and spontaneous.     

含噁嗪环硅烷偶联剂对石英纤维/含硅芳炔复合材料性能的影响

从石英纤维(QF)、含硅芳炔树脂(PSA)分子结构特点出发,设计并合成了一种含有噁嗪环和端炔的新型硅烷偶联剂(BCA),并以BCA改善QF/PSA复合材料的界面性能。采用差示扫描量热分析(DSC)、红外光谱分析(FT-IR)、X-射线电子能谱(XPS)及扫描电镜(SEM)等测试手段表征了BCA与QF/PSA复合材料的相互作用和界面改性效果。结果表明:BCA能够分别与PSA和QF形成良好的化学键合,改善复合材料的界面黏结;经w=2.0%的BCA处理后,QF/PSA复合材料的层间剪切强度、弯曲强度分别较未处理前提高了69.1%和68.8%。     

Kinetics of heterogeneous cellulose reactions. I. Cyanoethylation of cotton cellulose

Sakurada's equation and fundamental kinetic laws were applied to the heterogeneous cyanoethylation of cellulose, performed by reacting fiber with liquid acrylonitrile, with sodium hydroxide as the catalyst. The data fit Sakurada's equation better at higher temperatures; deviation occurs at the initial stage, and the rate of reaction falls abruptly at a later stage. The degree of substitution at which the abrupt rate change occurred decreased as the temperature increased from 31 to 60°C. and also as the crystallinity of the fiber decreased. Diluting the reagent with different solvents decreased the rate of reaction and changed its transition points, but did not change the essential nature of the reaction, each segment of which fits Sakurada's equation very well. A uniform distribution of the catalyst (sodium hydroxide) throughout the fiber was attempted, and then the reaction was studied at 50°C. Diffractograms of the samples provided further evidence that the position of the rate change is associated with the change of cellulose (I) crystalline structure. Approximate energy of activation has been calculated, from the specific rate constants, between 31 and 40°C. as 10.6 kcal. and between 45 and 50°C. as 16.7 kcal. At other temperatures the determination was handicapped, due to temperature dependence of the order of reaction. An empirical relation between the constants of Sakurada's equation and the reaction temperature has been sought and correlated with the Arrhenius equation. Energies of activation, determined from this relationship, have been found to be very close to the above values. The change of order of reaction with temperature suggests that the reaction is affected by diffusion and the mechanism is interpreted as a diffusion-controlled reaction where hydrogen bonds play a significant role in diffusion.     

Swelling behaviour of succinylated fibers

The swelling behaviour of cellulosic fibers bearing various amounts of carboxylic groups introduced by succinylation was studied as a function of pH. Upon an increase of pH, the perimeter of the succinylated fibers expanded as measured with the Wilhelmy plate technique. The fibers pass two pH regimes of increased expansion, pH = 5 and pH = 9. These pH levels correlate with the conductometric titration, which reveals two inflection points in both the pH and conductivity values for the succinylated fibers. Determinations of fiber saturation points (FSP) confirm that the cell wall is largely affected by increased pH. Analysis of the fibers with ESEM (Environmental Scanning Electron Microscope) showed that bundles of fibrils were released from the surface of the succinylated fibers at higher pH. Wilhelmy measurements also showed that the surface roughness was more than doubled in fibers succinylated for 12 h as pH rose from 3.2 to 10. These results indicate that, as the charge of the fibers is increased, the swelling forces reach such levels of magnitude that they overcome the structural network forces holding the fiber wall together. The methodology applied can hence be used to quantify the fundamental gel properties of the fiber wall.     

The dynamic mechanical behavior of random-in-plane short fiber-reinforced epoxy resin composites

In the present paper, the dynamic mechanical properties of random-in-plane short fiber-reinforced epoxy resin composites were studied by using a rheometrics solids analyzer. The three-point bend testing of the four composites (glass fiber/913 epoxy resin, glass fiber/924 epoxy resin, carbon fiber/913 epoxy resin and carbon fiber/924 epoxy resin) was carried out over temperatures from −100°C to 200°C at a frequency of 10 Hz and strain 0.05%. The composites based on 924 epoxy resin, which has been designed specially for high temperature applications, have less energy loss than the 913 epoxy resinbased composites. For the same resin, the carbon fiber-reinforced composites have less energy loss than the glass fiber-reinforced composites. All the composites have less energy loss than their corresponding matrices; the greater the fiber content, the lower the energy loss. The beta transition of 913 epoxy resin has been shifted to a higher temperature after being reinforced. It was shifted from −50°C to −30°C after being reinforced with glass fiber and made a diffuse shoulder-like peak commencing at −30°C after being reinforced with carbon fiber. The 924 epoxy resin has undergone the same change in beta transition as the 913 resin, though to a smaller extent. The phenomenon suggested that interactions between the macromolecules of the epoxy resins and the molecules along the fiber's surface.     

6061铝合金微弧氧化陶瓷层生长速度的研究

以变形铝合金6061为试验材料,采用MAO240／750微弧氧化设备、TT260测厚仪和JSM6460扫描电子显微镜,研究了电流密度、占空比、样品尺寸和溶液温度等因素对铝合金微弧氧化陶瓷层生长速度的影响。结果表明：陶瓷层厚度随着时间的延长而线性增大,电流密度越大,陶瓷层生长速度越快,在相同时间内样品表面所达到的电压越高,电压的升高提高了陶瓷层被击穿继续发生内部氧化的能力;占空比大小对陶瓷层生长速度几乎无影响,而电压随着占空比的减小发生微小的上升;恒流氧化时,虽然陶瓷层的生长速度不随样品尺寸变化,但是电压随样品尺寸增大而升高;随着溶液温度的升高,溶液的导电能力增强,陶瓷层的生长速度变快。     

侧链液晶聚硅氧烷langmuir膜的原子力显微镜观察

通过原子力显微镜观测了含手性基团侧链液晶聚硅氧烷在空气/水界面上的单层膜,观测了成膜物在界面形成微畴结构以及表面压力升高时微畴聚集、重排过程,分析了纳米级微畴形成、聚集和重排的机理和规律。     

An analysis of deformation process on poly‐p‐phenylenebenzobisoxazole fiber and a structural study of the new high‐modulus type PBO HM+ fiber

This study is concerned with fiber structure of new high‐modulus type PBO fiber. Crystal modulus and molecular orientation change with stress was surveyed. Standard‐modulus type PBO (AS) fiber has hysteresis effect to applied stress while high‐modulus type PBO (HM) fiber shows reversible change. In order to raise actual PBO fiber modulus higher, nonaqueous coagulation process was adopted with conventional heat treatment. The fiber (HM+) so made gives 360 GPa in the Young's modulus and an absence of small‐angle X‐ray scattering pattern that is characteristic for aqueous‐coagulated PBO fiber with heat treatment (Zylon™ HM). The crystal structure form and crystal size for the HM+ fiber are the same as those of the HM fiber. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1605–1611, 2000     

Enhancing the inter-fiber bonding properties of cellulosic fibers by increasing different fiber charges

Cellulosic fiber has been increasingly used in many fields. The fiber charge, including the surface charge and inner charge, affects the properties of cellulosic fiber and fiber-based materials significantly. In this study, the cellulosic fiber was subjected to different treatments, including 2,2,6,6-tetramethyl-piperidine-1-oxyl radical-mediated oxidation, carboxymethyl cellulose attachment and mechanical refining, to alter the fiber charge selectively. The effects of the fiber surface charge and inner charge on fiber performances and inter-fiber bonding strength for improving the high-value application of cellulosic fibers, respectively, were discussed. The results showed that the performances of cellulosic fiber can be improved with the increase of either surface or inner fiber charges, including the increased water retention value, flexibility and inter-fiber bonding strength, but with slightly decreased drainability. An increasing bulk fiber charge showed more significant enhancement of the inter-fiber bonding strength than only an increase of the fiber surface charge on cellulosic fiber. This was because the fiber inner charge contributed to the increase of fiber flexibility and deformability, which could benefit the inter-fiber bonding indirectly. As a consequence, the bulk fiber charge enhancement was better for tensile strength improvement of handsheets (fiber-based material) than only fiber surface charge enhancement. Increasing both the surface charge and inner charge improved the tensile strength effectively with less change of the bulky fiber network than the refining treatment.     

Gibbs free energy of liquid drops on conical fibers

Small drops can move spontaneously on conical fibers. As a drop moves along the cone, it must change shape to maintain a constant volume, and thus, it must change its surface energy. Simultaneously, the exposed surface area of the underlying cone must also change. The associated surface energies should balance each other, and the drop should stop moving when it reaches a location where the free energy is a minimum. In this paper, a minimum Gibbs free energy analysis has been performed to predict where a drop will stop on a conical fiber. To obtain the Gibbs free energies of a drop at different locations of a conical fiber, the theoretical expressions for the shape of a droplet on a conical fiber are derived by extending Carroll's equations for a drop on a cylindrical fiber. The predicted Gibbs free energy exhibits a minimum along the length of the cone. For a constant cone angle, as the contact angle between the liquid and the cone increases, the drop will move toward the apex of the cone. Likewise, for a constant contact angle, as the cone angle increases, the drop moves toward the apex. Experiments in which water and dodecane were placed on glass cones verify these dependencies. Thus, the final location of a drop on a conical fiber can be predicted on the basis of the geometry and surface energy of the cone, the surface tension and volume of the liquid, and the original location where the drop was deposited.     

Preparation of poly (methyl methacrylate)/LDH nanocomposite by exfoliation-adsorption process

Exfoliated nanocomposite based on Mg, Al layered double hydroxide (Mg,Al-LDH) and poly(methyl methacrylate) (PMMA) has been prepared by exfoliation/adsorption process with acetone as co-solvent. The product was characterized by X-ray diffraction (XRD), thermal analysis and High Resolution Transmission Electronic Microscope (HREM). The results suggest that the brucite-like sheets of LDH disperse individually in the polymer matrix, and the thermal stability of the nanocomposite increases highly.