Gas exchange in modified atmosphere packaging. 1: A new theoretical approach for micro-perforated packs

Gas transport and exchange through the perforations in micro-perforated packs used in modified atmosphere packaging were numerically modelled by using Stephan-Maxwell laws, and, outside these perforations, by Fick's law. the model accounts simultaneously for oxygen, carbon dioxide, nitrogen, argon and water vapour. Fruit and vegetable respiration was approximated by Michaelis-Menten kinetics depending on oxygen concentration with an uncompetitive inhibition due to carbon dioxide. Concentration equilibrium was reached after 2 to 3 days, depending on the void volume and on the diffusion properties of the packs. the equilibrium concentrations were dependent on the number of perforations, their diameter, the thickness of the film and the temperature. However, a pack which makes 10% oxygen possible within the pack at 10°C might induce anaerobiosis at 20°C.     

High-temperature coating for titanium aluminides using the pack-cementation technique

The practical application of titanium aluminide metal-matrix composites (MMCs) at high temperatures requires suitable surface coatings to provide the needed oxidation resistance. Without a coating, the titanium aluminide alloys suffered from rapid oxidation attack at elevated temperatures, particularly under thermal cyclic conditions. The pack-cementation coating process was utilized to aluminize the surface region of a Ti₃Al-base alloy to TiAl₃, the most oxidation-resistant phase. With the existence of an adherent conversion coating, a thin protective alumina scale formed on the outer surface, and a significant improvement in the corrosion resistance was observed. Excellent coating efficiency and geometric flexibility were demonstrated in this study by the pack-cementation technique. Further development of the cementation process will focus on the elimination of surface cracking in the coating.     

气相缓蚀干燥材料的研究进展

叙述了钼酸铵-硅胶-聚乙烯气相缓蚀干燥材料研究的进展，用这种材料包装黑色与有色金属制件可有效地防止制件的点蚀、麻蚀和失泽。     

Improvement in the oxidation resistance of TiAl by preoxidation in a SiO2-powder pack

The resistance of TiAl coupons to cyclic oxidation at 1300 K in a flow of purified oxygen under atmospheric pressure has been significantly improved by preoxidation. The preoxidation was performed by heating the specimens, buried in a silica powder and encapsulated in a silica tube under a vacuum of 1.3×10^–3 Pa at 1200 K for 100 ks. After 20 cycles (400 hr) of oxidation the mass gain was still very small, and correspondingly the scale thickened very slightly. This superior oxidation resistance is attributable to the formation of a scale very rich in alumina by the preoxidation under a very low-oxygen partial pressure. This low-oxygen partial pressure may be near the dissociation pressure of silica and much lower than that attained by modern vacuum pumps.     

Oxidation resistance coatings of Mo−Si−B alloys via a pack cementation process

Oxidation behavior of Si pack cementation coatings on a three-phase Mo−Si−B alloy was examined. During Si pack cementation of a three-phase Mo−Si−B alloy, a MoSi₂ outer layer was synthesized on the exterior layer. Following oxidation in air of the pack-coated alloys at 1200°C, the MoSi₂ phase layer was consumed and replaced by the Mo₅Si₃ (or T₁) phase. The synthesized T₁ phase provided excellent oxidation resistance when exposed to high temperatures. The silicide-coated alloys exhibit higher oxidation resistance compared with uncoated Mo−Si−B alloys. The enhanced oxidation behavior and its mechanism are discussed in terms of the thicknesses of the oxide layers under exposure to high temperatures.     

小套管二次固井工艺技术

随着油田开发时间的延长，各种因素导致的油水井套管损坏日益严重，直接影响了油田的开发和经济效益。利用小套管二次固井工艺，在因套管损坏而报废的油水井上，采取封堵、打通道措施，全井或部分悬挂小套管后，采取延时固井法封固环空，二次射孔投产，达到恢复油水井生产的目的。在平方王、林凡家2个油田实施了12井(次)，成功地恢复了10口注水井，为套管损坏井的治理探索出了一条新途径，成为老油田挖潜增效的一个重要手段。     

Modeling and Optimization of Heat Dissipation Structure of EV Battery Pack

In order to solve the problems of high temperature and inconsistency in the operation of electric vehicle (EV) battery pack,computational fluid dynamics (CFD) simulation method is used to simulate and optimize the heat dissipation of battery pack.The heat generation rate at different discharge magnifications is identified by establishing the heat generation model of the battery.In the forced air cooling mode,the Fluent software is used to compare the effects of different inlet and out-let directions,inlet angles,outlet angles,outlet sizes and inlet air speeds on heat dissipation.The simulation results show that the heat dissipation effect of the structure with the inlet and outlet on the same side is better than that on the different sides;the appropriate inlet angle and outlet width can improve the uniformity of temperature field;the increase of the inlet speed can improve the heat dissipation effect significantly.Compared with the steady temperature field of the initial structure, the average temperature after structure optimization is reduced by 4.8益and the temperature difference is reduced by 15.8℃,so that the battery can work under reasonable temperature and temperature difference.     

High-Temperature-Oxidation Behavior of Iron–Aluminide Diffusion Coatings

Aluminide diffusion coatings were oxidized in air under atmospheric pressure under isothermal and cyclic conditions. The high-temperature efficiency of the pack-aluminized alloys was tested by comparing their oxidation behavior in the temperature range 800–1080°C. The k _p values deduced from the parabolic plots of weight-gain curves showed that α-Al₂O₃ composed the major phase of the oxide scale on samples oxidized at T > 1000°C. For lower temperatures, transient-alumina phases were observed. The aluminide materials also exhibited excellent resistance to cyclic oxidation at 1000°C. The second aim of this study was to dope the aluminide compounds obtained by a pack-cementation process with yttria, which was introduced by metal-organic chemical-vapor deposition (MOCVD). The beneficial effect of the reactive-element-oxide coating is strongly dependent on its mode of introduction, since the oxidation resistance is drastically increased when the Y₂O₃ coating was applied prior to the aluminization process. When applied after the aluminization, the reactive element gave negative effects on the high-temperature oxidation behavior of the iron aluminides. The oxide morphologies, X-ray diffraction patterns and two-stage experiments helped to understand the oxide-scale-growth mechanisms.     

Microstructural study on oxidation of aluminized coating on inconel 625

The high-temperature oxidation behavior of aluminized Inconel 625 has been examined using scanning electron microscopy (SEM) and fine-probe spot and linescan energy dispersive spectroscopy (EDS) microanalysis techniques. The formation of adherent slowly growing metallic coatings is essential for protection against severe environments. The coated (aluminized) and uncoated samples were subsequently oxidized in air at 1000 and 1100 °C to examine the performance of the aluminized coating. The micro-structural changes that occurred in both coated and uncoated samples were examined. It was found that coated samples showed superior performance against high-temperature oxidation, as compared to the uncoated samples. The coated samples revealed uniform and adherent oxidized layer, as compared to the uncoated samples. The oxidation behavior and multilayered microstructural morphology observed in the coated samples can be attributed to the interdiffusion and variation in kinetics of oxidation.     

Development and growth of boron-modified and germanium-doped titanium-silicide diffusion coatings by the halide-activated,pack-cementation method

A halide-activated, cementation pack has been developed to codeposit either silicon and boron or else silicon and germanium in a single processing/reaction step to grow Ti-silicide diffusion coatings on commercially pure (CP) titanium, Ti-22Al-27Nb, and Ti-20Al-22Nb. Since boron is nearly insoluble in TiSi₂, a TiB₂ layer is localized at the surface of the B-modified silicide coatings. The thickness of the TiB₂ layer is controlled by the choice of boron activity and halide activator in the pack. Germanium is soluble in the Ti-silicide layers but inhomogeneously distributed in the Ge-doped silicide coating. The germanium content is controlled by choices of the Si-to-Ge ratio and the halide activator in the pack. The growth kinetics for the five-layered B-modified silicide coatings are generally similar to the undoped silicide coatings. The growth mechanism for the five-layered Ge-doped silicide coatings is generally different from the undoped silicides. The growth of dual-layer Ti-boride coatings was also studied.