Excitation characteristics of magnets impregnated with paraffin wax

The Superconducting Electromagnetic Iron Separator (SEIS) based on paraffin wax vacuum pressure impregnation (VPI) technology was developed to remove magnetic impurities from coal. The superconducting coil was wound by Cu/NbTi wires. The inner and outer diameter of the coil are 928 mm and 1022 mm respectively. The height of the coil is 355 mm. The magnet generates a 3 T central field at 165 A of operating current.There are three SEIS devices that have been manufactured and tested. All the design requirements are achieved by the first device. However, the others can’t be charged to the design current in 20 min, which is a requirement of coal handing port. This paper presents the details of the VPI process and the charging tests. The excitation characteristics of three SEIS devices are shown in the results.     

石英微晶天平技术在原子层沉积碳化镍薄膜过程中的应用研究

采用等离子体增强原子层沉积技术分别以Ni (amd)₂、Ni (dad)₂为镍、碳前驱体,氢等离子体为还原剂成功沉积了碳化镍薄膜。两个沉积过程中,碳化镍薄膜厚度都随着反应循环次数的增加而线性增加。利用石英微晶天平技术对碳化镍薄膜的沉积过程进行了原位在线测量。初步提出碳化镍薄膜的沉积机理,其中由等离子体作用产生的氢原子对沉积过程有重要作用。一方面,在等离子体中原子氢与Ni (amd)₂或Ni (dad)₂发生化学反应,生成Ni、挥发性的N-叔丁基乙酰胺盐和碳氢化合物,这些镍在镍表面上有吸附和分解的趋势。此外,原子氢对吸附的碳氢化合物脱氢生成碳化镍和大量碳物种具有促进作用。另一方面,预计它还会刻蚀碳化镍表面的无定形碳和石墨,或者将碳化镍分解成具有催化活性的金属镍。     

Fabrication and characterization of nanoporous ZnO layers for sensing applications

In this contribution we employ a low temperature method for the deposition of thin and highly porous layers based on ZnO nanocrystallites. The method is based on coating of a substrate with ZnO suspension and thereafter the application of quasi static pressure on the sample. A high temperature step becomes redundant and the temperature does not exceed 120 °C during the whole process. The porosity, the specific surface area and the pore size distribution can be influenced by the variation of the process pressure. The influence of oxygen and water vapor on the photoresponse is investigated and a model explaining the observed behavior is discussed.     

Kinetics of photocatalytic reduction of Pb(II) on nanocrystalline TiO2 coatings: A quartz crystal microbalance study

Pb(II) is a highly toxic substance, exposure to which can cause various diseases. To better understand the application of TiO₂ as a photocatalyst for removing Pb(II) from wastewater, quartz crystal microbalance (QCM) technique was employed to in situ investigate the reduction behavior of Pb(II) on nanocrystalline TiO₂ coatings under N₂. The processes of Pb(II) reduction at various concentrations of HCOOH and in the presence of different organic additives were monitored, and the corresponding kinetics was proposed. The obtained results showed that the kinetics of Pb(II) reduction on TiO₂ coatings was closely related to the organic additives. The HCOOH showed a higher efficiency for Pb(II) reduction in comparison with other organic additives, and the reduction-rate constant reached 0.54 × 10⁻³ s⁻¹ which was two times higher than that exhibited in the presence of C₂H₅OH. QCM measurement provides an useful method for monitoring the reduction process of Pb(II) on TiO₂ coatings.     

石英晶体微天平质量检测量研究

基于石英晶体微天平质量检测原理,通过分析石英谐振器表面的振动位移,得出决定其电极表面每一点处质量灵敏度的物理量为该点处的振动加速度。在此基础上,基于石英谐振器的巴特沃斯-范·戴克等效电路模型提出一种计算石英晶体谐振器表面振荡幅度的方法,最终得到石英晶体微天平在整个检测过程中能检测到的平均质量。用10MHz的石英晶体微天平进行了数值验证,计算值与其理论上能达到的pg级检测限基本相吻合。     

A sensor of alcohol vapours based on thin polyaniline base film and quartz crystal microbalance

Thin films of polyaniline base, emeraldine base (EB), coating on the quartz crystal microbalance (QCM) electrode were used as a sensitive layer for the detection of a number of primary aliphatic alcohols such as ethanol, methanol, 2-propanol and 1-propanol vapours. The frequency shifts (Δf) of the QCM were increased due to the vapour adsorption into the EB film. Δf were found to be linearly correlated with the concentrations of alcohols vapour in part per million (ppm). The sensitivity of the sensor was found to be governed by the chemical structure of the alcohol. The sensor shows a good reproducibility and reversibility. The diffusions of different alcohols vapour were studied and the diffusion coefficients (D) were calculated. It is concluded that the diffusion of the vapours into the EB film follows Fickian kinetics.     

Role of hydrophobicity on the adsorption of synovial fluid proteins and biolubrication of polycarbonate urethanes: Materials for permanent meniscus implants

Both absorption and release of synovial fluid components lubricate the porous natural meniscus, whereas only adsorption can lubricate non-porous meniscus prostheses. The aim of this study was to establish the adsorption characteristics of the synovial fluid proteoglycan 4 (PRG4) and albumin on modified and unmodified polycarbonate urethane (PCU) and determine the effects on the coefficient of friction. PCU was modified with surface-tethered C18 chains (mPCU). Self-assembled monolayers (SAM) on gold were also used to generate higher and lower hydrophobicities. Protein adsorption and coefficients of friction were measured by quartz crystal microbalance and colloidal probe atomic force microscope. PRG4 formed a thick viscoelastic layer and significantly decreased the coefficient of friction on PCU and mPCU, with an exceptionally low coefficient of friction measured on mPCU (0.02 ± 0.02) due to its soft surface. Albumin formed a thin rigid layer with a much higher coefficient of friction on mPCU (1.14 ± 0.19). Albumin blocked PRG4 adsorption when simultaneously added to PCUs, and coefficients of friction of 0.48 ± 0.24 (PCU) and 0.49 ± 0.17 (mPCU) were measured. Albumin adsorption on hydrophobic substrates (water contact angle ⩾70° ± 4°) dramatically increased the coefficient of friction (3.41 ± 1.21 on hydrophobic SAM), indicating that increased hydrophobicity through hydrocarbon surface modification of PCU carries tribological risks.     

Protection of polymer from atomic-oxygen erosion using Al2O3 atomic layer deposition coatings

Thin films of Al₂O₃ grown using atomic layer deposition (ALD) techniques can protect polymers from erosion by oxygen atoms. To quantify this protection, polyimide substrates with the same chemical repeat unit as Kapton^® were applied to quartz crystal microbalance (QCM) sensors. Al₂O₃ ALD films with varying thicknesses were grown on the polyimide substrates. The ALD-coated polyimide materials were then exposed to a hyperthermal atomic-oxygen beam. The mass loss versus oxygen-atom exposure time was measured in situ by the QCM. Al₂O₃ ALD film thicknesses of ∼ 35 Å were found to protect the polymer from erosion.     

Comparison of some coating techniques to fabricate barrier layers on packaging materials

Atomic layer deposition (ALD), electron beam evaporation, magnetron sputtering and a sol-gel method were used to deposit thin aluminum oxide coatings onto two different fiber-based packaging materials of commercial board grades coated with synthetic and biodegradable polymers. Significant decreases in both the water vapor and oxygen permeation rates were observed. With each technique the barrier performance was improved. However, among the techniques tested ALD was found to be most suitable. Our results moreover revealed that biodegradable polylactic acid-coated paperboard with a 25-nm thick layer of aluminum oxide grown by ALD on top of it showed promising barrier characteristics against water vapor and oxygen.     

Solventless dry powder coating for sustained drug release using mechanochemical treatment based on the tri-component system of acetaminophen,carnauba wax and glidant

Objective: Solventless dry powder coating methods have many advantages compared to solvent-based methods: they are more economical, simpler, safer, more environmentally friendly and easier to scale up. The purpose of this study was to investigate a highly effective dry powder coating method using the mechanofusion system, a mechanochemical treatment equipped with high compressive and shearing force.Materials and methods: Acetaminophen (AAP) and carnauba wax (CW) were selected as core particles of the model drug and coating material, respectively. Mixtures of AAP and CW with and without talc were processed using the mechanofusion system.Results: Sustained AAP release was observed by selecting appropriate processing conditions for the rotation speed and the slit size. The dissolution rate of AAP processed with CW substantially decreased with an increase in talc content up to 40% of the amount of CW loaded. Increasing the coating amount by two-step addition of CW led to more effective coating and extended drug release. Scanning electron micrographs indicated that CW adhered and showed satisfactory coverage of the surface of AAP particles.Conclusion: Effective CW coating onto the AAP surface was successfully achieved by strictly controlling the processing conditions and the composition of core particles, coating material and glidant. Our mechanochemical dry powder coating method using the mechanofusion system is a simple and promising means of solventless pharmaceutical coating.     

Deposition of silicon doped and pure hydrogenated amorphous carbon coatings on quartz crystal microbalance sensors for protein adsorption studies

In this study hydrogenated amorphous carbon films (a-C:H) and silicon doped hydrogenated amorphous carbon films (a-C:H:Si) with different hydrogen and silicon contents were deposited onto sensors of a quartz crystal microbalance with dissipation detection (QCM-D). The resulting films were investigated with regard to their structural and elemental compositions using Raman spectroscopy, elastic recoil detection analysis and Rutherford backscattering spectroscopy. Furthermore the surface free energy (SFE) of the films was determined using contact angle measurements. The polar part of SFE of the a-C:H:Si films was found to be adjustable by the silicon content in these films and increased by increasing amounts of silicon. Carbon films with a broad range of chemical composition showed similar structure and properties when deposited on QCM-D sensors as compared with the deposition on silicon wafers. Subsequently, the amorphous carbon coated QCM-D sensors were used to study the adsorption of human serum albumin. These QCM-D results were related to the surface properties of the films.     

以不同PAN系炭纤维布制备燃料电池气体扩散层之研究

采用石墨化PAN系炭纤维布制备了高分子电解质燃料电池气体扩散层。通过电学实验、X-ray绕射与元素分析考察了所制气体扩散层的性能。结果表明：随热处理温度的升高，气体扩散层的电阻率降低，L2增加，d（x）2减小。高温处理后的炭纤维布作为高分子电解质燃料电池气体扩散层显示了较高的电池效能。     

Evolution of coating layers during high-temperature annealing and their effects on magnetic behavior of Fe(Si) soft magnetic composites

Low-loss Fe(Si) soft magnetic composites (SMCs) with atomic-layer-deposition coated layer were successfully prepared in this work. The continuous, compact and uniform Al₂O₃ layer is found to form tight bonding with the powder base. Evolution of the coating layers has been investigated under different annealing temperatures and closely linked to the magnetic performance of the composites. Results indicate that 1100 °C was the optimal annealing temperature, at which the Fe(Si) SMCs showed lowest core loss of 1237 mW/cm³ and the highest permeability of 99.7 simultaneously (100 mT/100 kHz). Integrity of the coating layer ensures the maximum grain growth and stress removal of powder particles at the highest possible temperature, so as to reduce the hysteresis loss. Formation of high resistivity oxides and silicates (Al₂O₃, Fe₂SiO₄ and 3Al₂O₃·SiO₂) after annealing result in a low inter-particle eddy current loss. Besides, high temperature vacuum annealing is helpful to eliminate impurity atoms and decrease the anomalous eddy current loss. The improvement in effective permeability caused by high-temperature annealing is mainly attributed to the relaxation of residual stresses and the reduction of defects. While excessive temperature leads to the decomposition and destruction of the insulation layer, resulting in a significant increase in hysteresis loss, inter-particle and anomalous eddy current loss.     

Preparations of TiO2 nanocrystal coating layers with various morphologies on Mullite fibers for infrared opacifier application

TiO₂ nanorods coatings (TONC) were prepared on the surface of Mullite fibers by seed-hydrothermal method, which were designed as infrared opacifier. The influences of different tetrabutyl-titanate amount on the TONC morphologies, crystalline and optical properties were investigated. Effective specific extinction (e*) was used to characterize their masking ability. The TONC morphologies could be adjusted from nanoparticles to nanorods, which had direct influence on their optical properties. In the 3 μm-6 μm range of infrared light, e* of TONC could be improved up to 2-4 folds compared with that of Mullite fibers. Present study indicated TONC is a promising infrared opacifier.     

Study of the effect of process parameters for n-heptylamine plasma polymerization on final layer properties

Plasma polymerization processes are widely used to chemically functionalize surfaces, which properties can be tuned by different operating variables. In this study, thin amine-containing polymer layers were produced on solid substrates in a custom-made cylindrical plasma polymerization reactor by radio frequency glow discharges of n-heptylamine vapours. Carefully planned experiments were conducted to evaluate the importance of four different process parameters on the chemical composition and thickness of the resulting films. The parameters investigated were: 1) deposition time, 2) power of the glow discharge, 3) distance between the electrodes, and 4) monomer pressure. Possible interactions between these variables were investigated through the use of statistical analyses (i.e., factorial design). This study reveals that n-heptylamine plasma polymer (HApp) layer thickness is influenced by the power of the glow discharge and the deposition time, as assessed by surface plasmon resonance and atomic force microscopy step height measurements. Also, the atomic ratio of nitrogen to carbon atoms on the treated surfaces is mainly influenced by the power of the glow discharge, as revealed by X-ray photoelectron spectroscopy. Quartz crystal microbalance analysis also confirmed that HApp layers are stable when immersed in aqueous solution.     

Formation mechanisms of zinc,molybdenum, sulfur and phosphorus containing reaction layers on a diamond-like carbon (DLC) coating

Diamond-like carbon (DLC) coatings are nowadays successfully applied on industrial components like pistons, piston rings and bearings in lubricated tribological contacts due to friction and wear reducing effects. In contradiction thereto, todays lubricants and additives are designed for tribological steel/steel contacts, whereby the knowledge on tribochemical layer formation on steel surfaces is comprehensive in contrast to the physical-chemical interactions between diamond-like carbon coatings, lubricants and additives. Therefore the formation mechanisms of zinc, molybdenum, sulfur and phosphorus containing reaction layers on a zirconium modified diamond-like carbon coating a-C : H : Zr (ZrC_g) in lubricated tribological contacts were analyzed by means of pin-on-disc (PoD) tribometer by varying the distances from s = 200 m–3,000 m under boundary and mixed friction conditions at T = 90 °C and a contact pressure p = 1,300 MPa regarding the application of diamond-like carbon coatings on gears. The base lubricant poly-alpha-olefin (PAO) was formulated using the anti-wear (AW) and extreme pressure (EP) additive zinc dialkyldithiophosphate (ZnDTP) and the friction modifier (FM) additive molybdenum dialkyldithiophosphate (MoDTP). The chemical composition of the tribochemical reaction layers by means of and Raman spectroscopy and x-ray photoelectron spectroscopy (XPS) as well as for the thickness differ significantly by varying the additivation.     

Influence of the solvent evaporation rate on the β-Phase content of electrosprayed PVDF particles and films studied by a fast Multi-Overtone QCM

A combination of an electrospray setup and a quartz crystal microbalance with dissipation monitoring (QCM-D) was employed to study the drying of droplets of poly(vinylidene fluoride) (PVDF) dissolved in dimethylformamide (DMF). A novel variant of the QCM was used, which interrogates the resonance frequency and the resonance bandwidth on four overtones at the same time, achieving a time resolution of 2 ms. This instrument allowed to elucidate the mechanism of β-phase formation in electrospray deposition of PVDF. When the distance between the nozzle and the substrate was small, the droplets landed in a partially wet state, as evidenced from an increase in the resonance bandwidth. No such increase in bandwidth was observed when the distance was large. From the flight time (milliseconds) and the drying time on the substrate (seconds), one concludes that drying in the plume is faster than drying on the substrate. IR spectra show that the β–phase content is close to 100 % for particles, which dried in the plume. It is less than 50 % for particles having dried on the substrate. Fast drying promotes the formation of the β-phase. Follow-up experiments with thicker films on steel substrates also show increased β-phase content for larger distances.