Directed growth of colloidal crystals on a hydrophobic polymer film by using hydrophilic traps

Deposition of colloidal crystal films onto a hydrophobic surface using capillary force-induced self-assembly is difficult to achieve because of wetting problems of the aqueous colloids with the substrate. We present here a method to overcome this problem. By introducing a hydrophilic trench around the hydrophobic polymer, uniform crystalline colloidal films can be deposited onto the surface of the polymer, provided a sufficient volume of suspension is used. The hydrophilic area around the polymer acts like an artificial trap that can help pin the colloidal suspension on the surface of the hydrophobic polymer surface and direct the self-assembly of colloidal spheres, which is the key to fabricate a uniform colloidal crystal film on the polymer surface.     

A study of fiber orientation in short fiber-reinforced composites with simultaneous mold filling and phase change effects

Most of the properties of injection molded short fiber-reinforced composites are highly dependent on the patterns of their fiber orientation, which are induced by the flow. On the other hand, in most practical injection molding processes, both filling and solidification of the molten suspension takes place simultaneously. This behavior indicates that both filling and phase change for solidification can occur at the same time and therefore affect the flow behavior of the suspension, hence the fiber orientation. The aim of the current work is to present a numerical analysis of fiber orientation prediction in a three-dimensional rectangular cavity considering simultaneous mold filling and phase change of the suspending polymer. To trace the flow front during the filling process, the volume of fluid method (VOF) has been used, while an enthalpy-based approach was used to model the solidification. The standard Hybrid closure model of Advani and Tucker was applied to approximate the evolved fourth order orientation tensor during the fiber orientation calculation. To validate the developed numerical model, the results of the simulation model were compared with available experimental data for the rectangular cavity. The simulation results showed that they are in good agreement with the experimental data. Hence, the numerical model could assist in decisions regarding the design of polymer composite products.     

Hollow microspheres with binary colloidal and polymeric membrane: Effect of polymer and particle concentrations

We report here the preparation of hollow microspheres with a binary shell structure consisting of a precipitated polymer film with a layer of colloidal particles embedded on its outer surface. We recently demonstrated a method for the preparation of microspheres from solid-stabilised emulsion templates using various colloidal particle systems as emulsifiers. In the present work we use colloidal silica as an emulsifier for the preparation of the emulsion template for the microspheres and study the effect of polymer and particle concentrations on the obtained structures.Observations using optical microscopy showed that decreasing the polymer concentration led to a reduction in the capsule wall thickness and apparent strength of the microspheres when dried. Importantly, all microspheres preserved their integrity when in suspension. SEM studies confirmed the differences observed in the thickness of the precipitated film at the oil/water interface. In addition, we also demonstrate that a larger particle concentration leads to microspheres with a lower degree of porosity.     

Dry separation of fine particulate sand mixture based on density-segregation in a vibro-fluidized bed

Separation of fine particulate solid materials is one of most important unit operations in industry. Utilization of gas-solid fluidized beds has been considered where particulates are released from constraints due to contacts with surrounding particulates and segregation occurs according to density, size or combination of density and size. Addition of mechanical vibration to the gas-solid fluidized bed may improve dry solid separation. In this study, we investigated the dry separation characteristics of solid particulates using a vibro-fluidized bed especially focusing on the separation of fine particulate ores (≈100 μm) with small density differences. At first, we focused on the influence of fluidizing air velocity on the efficiency of segregation. Subsequently, the influence of vibration strength, vibration amplitude and frequency on segregation behavior was investigated. We found the density segregation does not occur with either gas-fluidization or vertical vibration alone. Only the combination of these effects produces density segregation. The fluidizing air velocity is an important factor to enhance the density-segregation of the particulates with small density difference.     

金红石复相体系浓悬浮体的制备

胶态成型工艺要求制备高固相含量、低粘度的浓悬浮体。由于复杂的胶体特性，金红石典型配方中含有的多种烧结助剂对金红石粉料在水介质中的分散行为往往产生较大影响。本文采用高温煅烧金红石复相体系的方法，消除了烧结助剂对制备金红石浓悬浮体的不良影响。通过调节pH值和分散剂用量，优化了金红石粉料在水介质中的分散条件，从而成功地制备了体积分数为51．7％的金红石复相体系浓悬浮体。     

Application of a neural network approach to the electrophoretic deposition of PEEK-alumina composite coatings

Nano-size Al₂O₃-polyetheretherketone(PEEK) composite thick films have been prepared on stainless steel substrates from non-aqueous colloidal suspensions by electrophoretic deposition (EPD). The effects on the deposition efficiency of process parameters, such as the deposition time, the difference of potential applied and their interactions were studied using a neural network approach to develop a quantitative understanding of the system. Furthermore the use of the neural network was optimized in the number of epochs, hidden layers and artificial neurons in each hidden layer by a design of experiment (DOE) analysis, demonstrating that these two methods can work together improving the final results of the neural network approach. Afterwards, a MonteCarlo analysis based on a simulation of 100,000 virtual depositions has permitted to deeply investigate the effect of independent variables (e.g. deposition time and difference of potential applied) on the deposition yield (dependent variable).     

PEEK composites reinforced with zirconia nanofiller

The present investigation deals with the preparation and characterization of nanocomposites of polyether ether ketone (PEEK) containing nanosized zirconia filler up to 3 wt.% loading. It has been observed that presence of zirconia filler dispersed in polymer matrix enhances various basic and functional properties (e.g., mechanical properties, thermal stability & other physico-mechanical properties). The SEM studies reveal that the dispersion of zirconia nanofiller is uniform throughout the polymer matrix. The thermal stability of the nanocomposites has been studied by TGA. Thermal analysis of the composites shows an increase in the thermal stability with increase of nanofiller content. This may be attributed to strong interaction between polymer chains and filler particles. DMA studies show the significant improvement in storage modulus of the nanocomposites because of better interaction of zirconia particles in PEEK matrix.     

Determination of an iron suspension in water by laser-induced breakdown spectroscopy with two sequential laser pulses

We have applied laser-induced breakdown spectroscopy to quantitative analysis of colloidal and particulate iron in water. A coaxial sample flow apparatus developed in our previous work, which allowed us to control the atmosphere of laser-induced plasma, was used. Using sequential laser pulses from two Q-switched Nd:YAG lasers as excitation sources, the FeO(OH) concentration in the tens of ppb range was determined with an optimum interval between two laser pulses and an optimum delay time of a detector gate from the second pulse. The detection limit of Fe decreased substantially using two sequential laser pulse excitations: the 0.6 ppm limit of single pulse excitation to 16 ppb with sequential pulse excitation. The effects of the second laser pulse on the plasma emission were studied. The concentration of iron in fine particles in boiler water sampled from a commercially operated thermal power plant has been determined successfully by this method. The results show the capability of laser-induced breakdown spectroscopy in determining suspended colloidal and particulate impurities in a simple and quick way.     

喷射共沉积SiCp/Al复合材料的增强颗粒植入

对用喷射共沉积法制备颗粒增强复合材料中固体颗粒向金属基体的转移过程进行了计算.在考虑到颗粒所受到的拖曳力、表面力和密度差引起的浮力的条件下,推导出了增强颗粒植入沉积层的判据.以颗粒冲击沉积层液膜最小速度为表达形式的判据指出,颗粒的动能、直径和同金属的润湿条件对颗粒的植入有决定性的影响.     

Effect of Flue Gas Recirculation on Multi-Cyclones Performance in Reducing Particulate Emission from Palm Oil Mill Boiler

The effect of recirculating the flue gas on the performance of a multi-cyclones unit as particulate collector in an actual plant scale was studied. The existing multi-cyclones unit was modified by connecting a recirculation duct between the inlet and outlet gas stream of the multi-cyclones attached with an external induced (ID) fan. The particulate samplings were done following the U.S. EPA method at boiler outlet (before multi-cyclones), stack (after multi-cyclones) and recirculation duct. Result shows that the amount of recirculated particulates increases with ID fan suction power. The collection efficiency increased slightly from 68% (0% or without recirculation) to 74% (at 11% recirculation) and dropped to 67% (at 17% recirculation). Moreover, the amount of the fine particulate size fraction emitted able to be reduced one fold at 11% recirculation flow rate. However, high amount of recirculated particulates results in re-entrainment of particulates into the outlet of the multi-cyclones, hence, results in increase of particulate emission in the stack.     

聚醚醚酮的结晶与熔融行为研究

研究了PEEK在高于熔点的温度范围内处理时的结晶行为以及结晶后的熔融行为。发现处理时熔融的PEEK将同时发生交联与结晶,交联使未结晶的部分结晶受阻,结晶使尚存的晶片增厚,从而导致PEEK在DSC上出现对应于不同晶体结构的新的熔融双峰,并在此基础上提出了处理过程中PEEK结构变化的模型。此外,还发现处理后的PEEK的熔点,可高于目前已报导的平衡熔点。     

Polyetheretherketone (PEEK) for medical applications

Polyetheretherketone (PEEK) is a polyaromatic semi-crystalline thermoplastic polymer with mechanical properties favorable for bio-medical applications. Polyetheretherketone forms: PEEK-LT1, PEEK-LT2, and PEEK-LT3 have already been applied in different surgical fields: spine surgery, orthopedic surgery, maxillo-facial surgery etc. Synthesis of PEEK composites broadens the physicochemical and mechanical properties of PEEK materials. To improve their osteoinductive and antimicrobial capabilities, different types of functionalization of PEEK surfaces and changes in PEEK structure were proposed. PEEK based materials are becoming an important group of biomaterials used for bone and cartilage replacement as well as in a large number of diverse medical fields. The current paper describes the structural changes and the surface functionalization of PEEK materials and their most common biomedical applications. The possibility to use these materials in 3D printing process could increase the scientific interest and their future development as well.     

Consolidation Process of PEEK/Carbon Composite for Aerospace Applications

Processing of PEEK/carbon composites into an aerospace structural part like the space arm can be very complex and necessitates repetition of the consolidation process in order to obtain a void free structure. The objective of the present work was to evaluate the effect of successive consolidations on the PEEK/carbon composite properties in order to determine optimum consolidation conditions.It is well known that the properties of the PEEK matrix in PEEK/carbon fiber composite are dependent on the processing conditions. Since each of the successive consolidations is done at a temperature of 400°C for a period of 60 minutes, it can be predicted that after a few cycles of consolidation, such thermal treatment can lead to matrix modifications. The results of the present study indicate that successive consolidations lead to modifications of the crystallization behavior of the PEEK matrix in the composite; alteration of the mechanism of nucleation of the PEEK matrix as well as the global rate of crystallization and a reduction in the recrystallizable material was observed. Modifications in the crystallization behavior of the PEEK matrix probably result from alteration of the chemical structure of the PEEK matrix when the composite is submitted to long treatment at high temperature. In particular, under oxidizing conditions, in air for example, chain scission followed by crosslinking reactions was proposed as the mechanism responsible for the matrix evolution.The evaluation of the tensile properties and the short beam shear strength of the consolidated samples also suggests that successive consolidations can affect the mechanical behavior of the PEEK/carbon composites. The mechanical characterization indicates that up to a certain level, the evolution of the PEEK structure during the consolidation process can be beneficial in terms of tensile and interfacial performance since crosslinks are strengthening structure.     

Tailoring the morphology of raspberry-like carbon black/polystyrene composite microspheres for fabricating superhydrophobic surface

In our previous report, raspberry-like carbon black/polystyrene (CB/PS) composite microsphere was prepared through heterocoagulation process. Based on the previous study, in the present work, the morphology of raspberry-like CB/PS particle is tailored through adjusting the polarity and the concentration ratio of CB/PS colloidal suspension with the purpose to prepare particulate film for the fabrication of superhydrophobic surface. Scanning electron microscope (SEM) confirms the morphology of raspberry-like particle and the coverage of CB. Rough surfaces fabricated by raspberry-like particles with proper morphology are observed by SEM and clear evidence of superhydrophobic surface is shown. The structure of raspberry-like particle is analyzed by atom force microscope. The proposed relationship between the hydrophobicity and the structure of CB aggregates on the surface of PS microsphere is discussed in details.     

Effect of hot water immersion on the performance of carbon reinforced unidirectional poly(ether ether ketone) (PEEK) composites: Stress rupture under end-loaded bending

This paper describes the behaviour of AS4 and T700SC reinforced PEEK composites (SUPreM™ and ACP-2) under applied compressive bending strain. The effect of an increased molecular weight of the polymer matrix on the residual time under endloaded compression bending conditions is studied. Generally for a given composite material, the higher the testing temperature and the applied strain the faster the failure occurs. At test temperatures exceeding the glass transition temperature or at high strain ratios the time-to-failure for CF/PEEK composites follows a master curve. The residual times under endloaded compression bending conditions increase with increasing toughness of the PEEK matrix but decrease with increasing tensile strength of the reinforcing fibres. It seems that the better the fibre/matrix adhesion the lower is the time to failure of an endloaded composite, because more load is transferred from the matrix into the fibres.In order to simulate composite applications under ‘harsh’ conditions the CF/PEEK composites have been exposed to boiling water. PEEK is known to be highly resistant to environmental effects, but water uptake significantly influences the overall performance of CF/PEEK composites under endloaded compression bending conditions. The tensile properties of the composites have been measured as function of exposure time in boiling water. The fibre dominated uniaxial tensile strength is not/or only slightly affected by the boiling water conditioning even after extended exposure times but the transverse tensile strength decreases significantly after exposure to boiling water. The performance of SUPreM™ CF/PEEK-150 and 450 composites under endloaded compression bending conditions are positively affected by water conditioning whereas APC-2 fails at shorter residual times. The fracture behaviour under endloaded conditions is also affected by the ingress of water into the composite.The obtained results show clearly that applications of thermoplastic composites leading to large out of plane deformations can only be ‘safe’ if the maximum service temperatures of the finished part will be well below the glass transition temperature of the polymer matrix otherwise even at low bending radii a dramatic failure of the material cannot be excluded.     

SiCP/ 6061Al 合金复合材料的高温单轴棘轮行为及其时间相关特性

对T6 热处理后的SiC_P / 6061Al 合金复合材料的高温(300 ℃) 单轴应变循环特性和棘轮行为进行了实验研究, 讨论了具有两种颗粒体积分数的复合材料在高温下不同加载条件时的循环软/ 硬化特性和棘轮行为特征。实验研究表明: 颗粒增强金属基复合材料宏观上表现出与金属材料相类似的应变循环特性和棘轮变形规律, 即复合材料在非对称应力循环下也将产生一定的棘轮变形, 并随应力幅值和平均应力的增加而增加; 颗粒的引入使复合材料抵抗棘轮变形的能力增强, 棘轮变形随颗粒体积分数的升高而下降; 在高温下棘轮行为体现出明显的时间相关特性, 即棘轮应变值明显依赖于加载率和峰值保持时间, 并具有明显的蠕变-棘轮交互作用。在对该类复合材料的棘轮行为进行本构描述时必须考虑复合材料的微结构特征、加载条件以及时间效应等的影响。      

Electrophoretic deposition of Al2O3-SiC composite

A ceramic composite with Al₂O₃ particles/SiC whiskers has been prepared by electrophoretic deposition in an isopropanol suspension. In the absence of a small amount of nitric acid (0.06–0.32 M), no deposition is observed. The amount of deposition increases with increasing applied voltage and solid loading, but decreases significantly with the amount of water present. The latter result is attributed to the fact that the colloidal stability of the suspension is degraded by water. Microstructural and compositional analyses show that the SiC whiskers are uniformly distributed in the green compact when the colloidally stable suspension is used during electrophoretic forming.     

Characterization of surface-modified nanoparticles for in vivo biointeraction. A sedimentation field flow fractionation study

Sedimentation field flow fractionation (SdFFF) is an emerging high-performance analytical tool for separation and determination of size and adsorption characteristics of colloidal particles. This study demonstrates how SdFFF can be used to characterize nanoparticles prepared for in vivo applications including (1) the quantification of polymer uptake on nanoparticles where surface coverage is crucial and (2) the coupling of cell adhesive peptides containing the Arg-Gly-Asp motif (RGD). Quantitative information about polymer adhesion in order to prepare a bioinert surface and an accurate determination of ligand uptake are both of obvious importance for the understanding of, for example, relations between the number of attached molecules for biointeraction and an observed therapeutic effect. In addition, the present work highlights the necessity to perform careful characterization of commercially available particulate starting materials, in terms of size and polydispersity, prior to biological experimentation.     

Response of primary fibroblasts and osteoblasts to plasma treated polyetheretherketone (PEEK) surfaces

Polyetheretherketone (PEEK) is a synthetic polymer with suitable biomechanical and stable chemical properties, which make it attractive for use as an endoprothetic material and for ligamentous replacement. However, chemical surface inertness does not account for a good interfacial biocompatibility, and PEEK requires a surface modification prior to its application in vivo.In the course of this experimental study we analyzed the influence of plasma treatment of PEEK surfaces on the cell proliferation and differentiation of primary fibroblasts and osteoblasts. Further we examined the possibility of inducing microstructured cell growth on a surface with plasma-induced chemical micropatterning.We were able to demonstrate that the surface treatment of PEEK with a low-temperature plasma has significant effects on the proliferation of fibroblasts. Depending on the surface treatment, the proliferation rate can either be stimulated or suppressed. The behavior of the osteoblasts was examined by evaluating differentiation parameters.By detection of alkaline phosphatase, collagen I, and mineralized extracellular matrix as parameters for osteoblastic differentiation, the examined materials showed results comparable to commercially available polymer cell culture materials such as tissue culture polystyrene (TCPS). Further microstructured cell growth was produced successfully on micropatterned PEEK foils, which could be a future tool for bioartificial systems applying the methods of tissue engineering.These results show that chemically inert materials such as PEEK may be modified specifically through the methods of plasma technology in order to improve biocompatibility.The first two authors share first authorship.     

剪切载荷下温度和应变率对碳纤维增强聚醚醚酮复合材料强化行为的影响

碳纤维增强聚醚醚酮(CF/PEEK)是一种高性能热塑性复合材料,在航空航天领域有着广阔的应用前景。由于PEEK具有温度和应变率相关的非线性行为,导致CF/PEEK复合材料在基体主导的面内剪切方向也有类似的力学行为。本文在不同的温度和应变率下对CF/PEEK复合材料试件进行了剪切实验,将应力-应变曲线分为线性与非线性部分,发现温度和应变率对CF/PEEK复合材料的屈服应力有着较大的影响。随着温度从20℃升高到130℃屈服应力下降了66%左右,下降速度先快后慢,随着应变率从10?5 s?1提高到0.1 s?1屈服应力均匀增大了35%左右。将所得规律拟合背应力经验公式,修改了经典的热塑性复合材料本构模型的屈服函数。并编写VUMAT用户子程序对CF/PEEK复合材料剪切实验进行数值分析,与实验结果对比发现非线性阶段的剪切应力-应变关系及屈服点的剪切应力吻合良好,但是由于纤维和PEEK基体的浸润性较差,导致CF/PEEK复合材料内部存在孔隙缺陷,影响了CF/PEEK复合材料的初始剪切弹性行为,导致加载初始阶段存在偏差。