HDPE／PA—6防渗合金的研制及应用

本文介绍了阻隔容器用HDPE/PA-6防渗合金的工艺技术,包括配方选择、相容剂的选择及最佳工艺条件的确定。将制成的改性粒料吹塑成小型中空容器,并进行了二甲苯、汽油防渗试验。     

Localized corrosion of Al90Fe5Gd5 and Al87Ni8.7Y4.3 alloys in the amorphous, nanocrystalline and crystalline states: resistance to micrometer-scale pit formation

The role of isothermal aging on the localized corrosion behavior of Al₉₀Fe₅Gd₅ and Al₈₇Ni_8.7Y_4.3 alloys was characterized in 0.6 M NaCl solution. The pitting (E_pit) and repassivation (E_rp) potentials were both increased ∼400 mV by the presence of transition and rare earth metal additions in supersaturated solid solution and amorphous structure. A statistical distribution in E_pit observed on small electrodes was due, in part, to the sensitivity of this critical potential to the presence of a population of critical surface flaws that serve as pit initiation sites. Mechanistic insight on the spacing of critical flaws was enabled by varying the tested electrode surface area. E_rp was not dependent on electrode surface area due to the similarity of pit depths in all electrode sizes. The critical potentials were also characterized after heat treating the amorphous ribbons isothermally at 150 °C for 25 h and 550 °C for 1 h. The former produced Al-rich nanocrystals embedded in the remaining amorphous matrix while the latter produced a fully crystalline condition containing intermetallic phases. Notably, the improved resistance to the formation of micrometer-scale pits was not lost compared with the fully amorphous condition when small Al-rich nanocrystals were present in an amorphous matrix. However, improvement in pitting corrosion resistance was completely lost in the fully crystallized condition as indicated by values for E_pit and E_rp that were similar to those of high purity, polycrystalline aluminum.     

The kinetics of hydrogen transport through amorphous Pd82−yNiySi18 alloys (y=0-32) by analysis of anodic current transient

Hydrogen transport through amorphous Pd_82−yNi_ySi₁₈ alloys (y=0-32) was investigated in 0.1 M NaOH solution by analysis of the anodic current transient. It was found that the anodic current transient shows the non-Cottrell behaviour, but its shape and value remain nearly constant regardless of the hydrogen discharging potential. From the coincidence of the anodic current transient theoretically calculated with that experimentally measured, it is suggested that the change in surface concentration of hydrogen with time is uniquely given by the rate of hydrogen transfer from absorbed state at the electrode sub-surface to adsorbed state on the electrode surface. This means that neither the ‘constraint of constant concentration’ nor the ‘constraint by Butler-Volmer behaviour’ is effective at the electrode surface during hydrogen extraction. On the basis of the theoretical current-time relation under the ‘constraint by hydrogen transfer of absorbed state to adsorbed state’, the hydrogen diffusivity was determined to have an almost constant value of (1.3±0.4)×10⁻⁸ cm² s⁻¹, irrespective of the Ni content and in the absence of Ni. On the other hand, it is inferred that the rate constant of hydrogen transfer decreases markedly with increasing Ni content due to the Ni(OH)₂ layer formed on the electrode surface.     

Plane stress fracture toughness of physically aged plasticized PETG as assessed by the essential work of fracture (EWF) method

The plane stress fracture toughness of amorphous copolyester (PETG) sheets plasticized by various amount of neopentylglycol dibenzoate (NPGDB in 0, 5, 10 and 20 wt%) was studied in as-received (AR) and rejuvenated (RJ) states by adopting the essential work of fracture (EWF) method. EWF tests were performed on deeply double-edge notched tensile loaded (DDEN-T) specimens at various deformation rates (2,10 and 100 mm/min) at room temperature. It was established that physical aging strongly affected the EWF terms. The specific yielding-related EWF increased with increasing deformation rate and decreased with increasing plasticizer content. The specific non-essential work and its necking-related constituent, which changed parallel to each other, remained constant up to 10 wt% NPGDB content and decreased afterwards. The plastic zone in the DDEN-T specimens was formed by cold drawing which is governed by the entanglement structure. This was demonstrated by the shape recovery of the plastic zone in the broken DDEN-T specimens after heating them above the T_g of the related PETG compound.     

Low-temperature synthesized amorphous quasi-high-entropy carbonate electrocatalyst with superior surface self-optimization for efficient water oxidation

Anionic High-entropy materials have seldom been reported as a new library of water oxidation electrocatalysts owing to great difficulty in uniformly distributing multiple elements with different physicochemical properties and harsh synthesis conditions. Herein, a series of amorphous quasi-high-entropy carbonates for the first time is prepared via a facile low-temperature hydrothermal route. The optimized CoCrFeMnMoCO₃ with hydrothermal treatment of 6 h can serve as a promising oxygen evolution reaction (OER) electrocatalyst for water splitting on account of amorphous structure rendering more exposed active sites, superior synergistic effect realizing surface component self-optimization, high-valence ferritic species (Fe^(3+δ)+) providing high catalytic activity and high-entropy stabilization guaranteeing long-term OER performance, thus exhibiting the low overpotentials of 302 and 355 mV at the current densities of 10 and 100 mA cm⁻², respectively, the small Tafel slope of 36.7 mV dec⁻¹, and excellent durability longer than 38 h, dramatically exceeding its corresponding crystalline counterpart and benchmark RuO₂ catalyst, as well as yielding the current density of 10 mA cm⁻² with impressive low voltage of 1.56 V while used as bifunctional electrocatalyst for overall water splitting. This study lights a broad avenue to design other anionic high-entropy materials as promising OER catalysts.     

Progress in non-traditional machining of amorphous alloys

Amorphous alloys are a new type of multi-functional advanced material with the properties of general metal materials and glass, which are also called metallic glasses. They have good comprehensive properties, such as a wide application range, low cost, and high reusability. Using reasonable process parameters, non-traditional machining can not only realize the machining of complex amorphous parts, but also avoid the crystallization and oxidation of amorphous alloys, realizing tasks that cannot be accomplished by traditional machining. Therefore, this review systematically summarizes the research status and development potential of amorphous alloys fabricated using non-traditional machining methods. First, we introduce the principles of laser machining, ultrasonic machining, electrical discharge machining, electrochemical machining, and other non-traditional machining methods for amorphous alloys. Subsequently, the influence of the machining parameters and other external conditions on the machining effect is summarized. The machining cost, machining efficiency, and environmental impact of these non-traditional machining methods were compared. Finally, non-traditional machining technology for amorphous alloys is summarized and discussed.     

Synthesis of pure AlON: Eu,Mg phosphors by a mechanochemical activation route

Pure AlON: Eu²⁺, Mg²⁺ phosphors have been synthesized by a novel mechanochemical activation route. In the process of mechanical milling, the starting powder mixtures are mostly transformed into an amorphous phase with homogeneous elemental distribution at the atomic level, which significantly promotes the synthesis of AlON phase at a low reaction temperature. The firing temperature higher than 1500 °C would lead to the appearance of EuMgAl₁₀O₁₇ impurity phase. This is why pure AlON: Eu²⁺, Mg²⁺ phosphors could not be obtained by the traditional solid state reaction method, which requires higher firing temperature. The pure AlON: Eu²⁺, Mg²⁺ phosphors show comparable luminescence intensity, compared with that synthesized by the solid-state reaction method.     

Preparation and Dissolution Profiles of the Amorphous,Dihydrated Crystalline,and Anhydrous Crystalline Forms of Paclitaxel

The selection of pharmaceutical polymorphisms in the final production step is very important in terms of product recovery, properties, and storage. The amorphous, dihydrated crystalline, and anhydrous crystalline forms of paclitaxel were prepared using precipitation, spray drying, and colloid formation methods. These methods were found to be highly efficient and convenient, giving high recovery, short processing time, and good stability, as compared with conventional methods such as freeze drying, evaporation, recrystallization, and melting. The polymorphic natures of the resulting paclitaxel samples were confirmed by XRPD, IR, TGA, DSC, and SEM. The dissolution rates of the paclitaxel samples were studied in pharmaceutical solvents, which included cotton seed oil, corn oil, tricaprylin, and tributyrin. For each solvent, all of the amorphous paclitaxel samples showed much higher dissolution rates than the dihydrated crystalline, anhydrous crystalline, and commercial forms, and can be used for clinical applications that demand improvements in drug delivery.     

Injection-Compression Molded Part Shrinkage Uniformity Comparison between Semicrystalline and Amorphous Plastics

Both semicrystalline polypropylene (PP) and amorphous polystyrene (PS) parts were molded by injection-compression molding. The Taguchi method was utilized to investigate the effects of six processing parameters, including mold temperature, compression speed, compression time, compression distance, delay time, and compression force, on part shrinkage uniformity (SU), which was represented by standard deviation of shrinkage. Analyses of means and variance showed that the compression force is the most important parameter for SU of both parts. The compression distance is the second most significant parameter of SU on the PS parts, but it is the least important parameter on the PP part. The optimal processing parameters for improving the SU of both parts were found and verified experimentally.     

Effect of welding parameters on porosity distribution of dual laser beam bilateral synchronous welding in 2219 aluminum alloy T-joint

The dual laser beam bilateral synchronous welding (DLBSW) for T-joint is limited to develop for the porosity defect in joint. In order to investigate the effect of porosity in T-joint, the DLBSW experiment of 2219 Aluminum Alloy T-joint is carried out. While, the distribution of porosity is scanned by X-ray non-destructive testing (NDT) and the size of porosity is measured by particle size analysis software Nano measurer 1.2. The morphology of pore in fracture and the elemental concentration around the pore are investigated by scanning electron microscopy (SEM) and energy spectrometer (EDS). Furthermore, the analysis results of porosity distribution show that the optimal parameter is 3700?W of laser power and 2.5?m/min of welding rate, under which the number of porosities reaches the minimum. The main factor, caused the fracture of weld seam, is the concentrated porosities in T-joint. In addition, technical porosity is mainly found in the center of the weld seam or at the bottom of the weld seam, and it can be eliminated by improving welding parameters. Metallurgical porosity mainly exists at the edge and the top of the weld seam, including hydrogen porosity and metal vapor porosity which formed by the burning of metal elements.