5052 铝合金表面钛锆基转化膜的制备及耐蚀性

目的研究铝合金表面非铬酸盐高耐蚀性转化膜的制备工艺。方法以K2Zr F6和K2Ti F6为主盐,KMn O4为氧化剂,Na F为成膜促进剂,在5052铝合金表面制备化学转化膜。采用SEM,EDS,FT-IR,XPS对转化膜的形貌、结构以及成分进行分析,通过硫酸铜点滴实验、全浸蚀实验和极化曲线对转化膜的耐蚀性进行研究。结果获得了土黄色转化膜,主要由Al F3·3H2O,Al Ox/Al,Al2O3,Mn O2和Ti O2组成。转化处理后,铝合金的腐蚀电位正移了约591 m V,腐蚀电流密度由1.10μA/cm2降低为0.48μA/cm2。经过封闭处理后,腐蚀电流密度降低为0.04μA/cm2,耐蚀性明显提高。结论以K2Zr F6和K2Ti F6为主盐在铝合金表面形成的土黄色化学转化膜具有良好的耐蚀性。     

The physical and mechanical properties of composite cements manufactured with calcareous and clayey Greek diatomite mixtures

The aim of the present study is to test diatomite rocks as alternative pozzolanic materials that could be used for the manufacturing of pozzolanic cements in Greece. The diatomite rocks used occur in Samos Island and in the Elassona, Greece. The Samos diatomites were mainly consisted of calcite and opal-A, whereas the Elassona diatomite consisted of opal-A, clay minerals, feldspars and quartz. As a result, the Samos samples were rich in CaO and SiO₂, while the Elassona ones were rich in SiO₂, Al₂O₃ and Fe₂O₃. The specific surface of the laboratory-produced cements was high, with the grindability of the Elassona diatomites being lower than that of Samos. The water demand of all blended cements was higher than that of the laboratory produced OPC. The late compressive strength of most diatomite cements studied was improved with respect to the lab OPC.     

New 3D stratified Si-Ca-P porous scaffolds obtained by sol-gel and polymer replica method: Microstructural,mineralogical and chemical characterization

The aim of this research was to develop and characterize a novel stratified porous scaffold for future uses in bone tissue engineering. In this study, a calcium silicophosphate porous scaffold, with nominal composition 29.32 wt% SiO₂ – 67.8 wt% CaO – 2.88 wt% P₂O₅, was produced using the sol-gel and polymer replication methods. Polyurethane sponges were used as templates which were impregnated with a homogeneous sol solution and sintered at 950 °C and 1400 °C during 8 h. The characteristics of the 3D stratified porous scaffolds were investigated by Scanning Electron Microscopy, X-Ray Diffraction, Fourier Transform Infrared Spectrometry, Diametric Compression of Discs Test and Hg porosimetry techniques. The result showed highly porous stratified calcium silicophosphate scaffolds with micro and macropores interconnected. Also, the material has a diametrical strength dependent on the number of layers of the stratified scaffolds and the sintering temperature.     

故宫石质螭首健康状况无损检测及评估预研究

目的通过无损检测方法评估故宫石质螭首风化和安全程度。方法首先在现场选取6个螭首进行无损检测,获取各项风化指标(表面风化程度、裂缝大致情况、孔洞、回弹强度、酥粉质量)和安全等级指标(裂缝性质、裂缝数量等具体值,超声波波速、回弹强度)。在实验室模拟风化、破损试验,建立超声波波速、回弹强度与抗折强度的曲线关系。最后通过德尔菲法建立评价体系,采用加权平均法获得各螭首的风化等级、安全等级。结果石材的抗折强度、超声波波速和回弹强度的曲线关系式为fk=0.0004V~(0.4393)R~(2.9302)。确定了6个螭首的风化程度和安全状况水平,其中构件2的表面风化程度最弱、最安全;构件6的安全情况最差,急需采取有效防范措施。结论该无损检测和健康程度评估研究方法是一种简单、快速、可量化的评价方法,其成果可用于石质文物健康状况的检测和评估工程,以获得其风化等级、安全等级,并作为文物管理决策的依据。     

Mechanical properties improvements in two-phase and three-phase composites using carbon nano-fiber dispersed resin

Static strength tests were carried out for cured carbon nano-fiber (CNF) dispersed resin as tow-phase composites and for CFRP laminates using CNF dispersed resin as three-phase composites. To obtain these CFRP laminates, the CNF dispersed resin was impregnated to CF reinforcement and cured by hot press. The CNF used was a cup-stacked type of nano-fiber, CARBERE^®, made by GSI CREOS Corporation, Japan. Two CNF aspect ratios of 10 and 50 were employed. These fiber lengths of the CNF were controlled about 1000 nm (AR10) and 5000 nm (AR50), respectively. The CNF was dispersed to EPIKOTE 827^® epoxy resin in two values of CNF weight ratios, 5 and 10% to the resin. TORAYCA^® C6343 plain woven fabric was used for reinforcement of the CFRP laminates. The cure condition with the agent of aromatic amine EPIKURE W^® was 100 °C for two hours followed by a post cure of 175 °C for 4 h. The static strength tests led to the conclusion that the dispersion of CNF into epoxy improves mechanical properties of the tow-phase composites, and that CFRP laminates with CNF dispersed resin also exhibit higher compressive strength than CFRP laminates without CNF as control. Possibilities of improvement in mechanical properties were confirmed in the two and three-phase composites. Moreover, a proportional tendency in strength improvements to CNF weight content was found in the two present composites so far in the present test results.     

Boron bridged NiN4B2Cx single-atom catalyst for superior electrochemical CO2 reduction

Single-atom nickel catalysts hold great promise in the application of electrocatalytic carbon dioxide reduction reaction (CO₂RR), but suffer from the sluggish kinetics and serious competitive hydrogen evolution reaction (HER), which restrict their overall catalytic performance. Herein, we report a boron-bridging strategy to manipulate the atomic coordination structure and construct a single-atom nickel catalyst with an active center of NiN₄B₂ to realize excellent CO₂RR performance. Density functional theory analysis suggests that the unique NiN₄B₂ sites with tuned electronic structure facilitate the adsorption of CO₂ molecules and effectively suppress the HER pathway by increasing corresponding energy barrier. As-obtained Ni-SAs@BNC catalyst with a NiN₄B₂ structure exhibits significantly enhanced catalytic activity and selectivity than commonly used single-atom nickel catalysts with a NiN₄ structure, especially at high applied potentials. A high current density of up to (214 ± 21) mA cm⁻² at a potential of −1.2 V with a high CO Faraday efficiency (FE_CO) of ∼97% was achieved in a flow cell. This work inspires new insights into the rational design of atomic coordination structure of single-atom catalysts with tunable electronic structure for superior electrocatalytic activities.     

Preparation and characterisation of dry thin native protein trehalose films on titanium-coated cyclo-olefin polymer (COP) foil generated by spin-coating/drying process and applied for protein transfer by Laser-Induced-Forward Transfer (LIFT)

Laser-Induced-Forward Transfer (LIFT) is a non-contact method for transferring bioactive substances such as proteins from a so-called LIFT target, here a titanium-coated cyclo-olefin polymer (COP) foil, to a surface of a solid work piece, e.g. a medical implant. The quality of the surface coating of the LIFT target, i.e. its homogeneity and the bioactivity of the ingredients to be transferred, is crucial for the quality and the efficiency of the overall process. Here, aqueous trehalose solutions containing the proteins streptavidin, green fluorescent protein (GFP), and bovine serum albumin were used in a spin-coating/drying process to render dry thin native protein trehalose films on titanium-coated COP foils. The homogeneity of the layer thicknesses was characterised by spectroscopic ellipsometry and the homogeneity of the GFP distribution within the layer was monitored by fluorescence scan analyses. The bioactivity of the embedded proteins was probed after short- and long-term storage by FT-IR spectroscopy in spectral reflection method and biological activity tests based on fluorescence scan analyses. After application of the LIFT process, the transferred proteins were tested in their bioactivity by fluorescence scan analyses and their topology by AFM analysis, proving that highly functional LIFT targets can be prepared by the chosen method.     

Flexible MXene Framework as a Fast Electron/Potassium-Ion Dual-Function Conductor Boosting Stable Potassium Storage in Graphite Electrodes

Graphite anodes show great potential for potassium storage, however, their capacity fades quickly owing to substantial interlayer expansion/shrinkage (i.e., up to 60%) induced structural degradation. Here, Ti₃C₂T_x MXene nanosheets are used as a fast electron/potassium-ion dual-function conductor to construct the framework of all-integrated graphite nanoflake (GNF)/MXene (GNFM) electrodes. The continuous MXene framework constructs a 3D channel for fast electron/potassium-ion transfer and endows GNFM electrodes with a high structural stability. Owing to this unique MXene framework, GNFM electrodes exhibit much enhanced potassium storage performances than that of the conventional polymer-bonded electrodes even at high mass loadings. Moreover, GNFM electrodes also show impressive cyclability in non-flammable electrolytes and are further used as anodes to assemble novel non-flammable potassium-ion capacitors that show an excellent cyclability and high energy/power densities (113.1 Wh kg^–1 and 12.2 kW kg^–1). New insights into phase transition mechanism in GNFM electrodes are verified by operando XRD. Density functional theory calculations demonstrate that MXene can promote electron transfer and potassium diffusion in the heterointerface between GNF and MXene. Therefore, the results demonstrate that all-integrated GNFM electrodes designed with MXene as multifunctional frameworks provide a new paradigm for producing efficient potassium storage anodes.     

Low-temperature synthesis of nanosized disordered carbon spheres as an anode material for lithium ion batteries

Disordered carbons in the order of nanometers were prepared by a hydrothermal reaction route. X-ray diffraction studies indicated a highly disordered carbon structure. SEM and TEM results revealed that these disordered carbons have a perfect spherical morphology, smooth surface and uniform particle size of about 100 nm. The lithium intercalation property of the products was also investigated. The results showed that the products delivered lithium insertion and deinsertion capacities of 1233 and 491 mA h g^− 1 respectively during the first cycle. Subsequent cycles showed a remarkable improvement in cycling efficiency with a 10th cycle efficiency of 98%. The correlation between microstructure, morphology and electrochemical behavior of such carbons was discussed.     

Eis and XPS study of surface modification of 316LVM stainless steel after passivation

The effects of surface finish, nitric acid passivation and ageing in air on corrosion resistance of 316LVM stainless steel in 0.5% H₂SO₄ have been investigated by EIS, potentiodynamic polarization measurements and XPS. The results indicate that a smoother surface exhibits to a higher corrosion resistance. The effectiveness of the passivation treatment strongly depends on nitric acid concentration, passivation time and temperature. The passivation treatment significantly increases the corrosion resistance due to a high Cr content in the passive film and increased film thickness. Ageing after passivation increases the corrosion resistance whereas ageing before passivation has little effect.