Effects of chromium on the corrosion and electrochemical behaviors of ultra high strength steels

The effects of chromium on the corrosion and the electrochemical behaviors of ultra high strength steels were studied by the salt spray test and electrochemical methods. The results show that ultra high strength steels remain martensite structures and have anodic dissolution characteristic with an increase of chromium content. There is no typical passive region on the polarization curves of an ultra high strength stainless steel, AerMet 100 steel, and 300M steel. However, chromium improves the corrosion resistance of the stainless steel remarkably. It has the slowest corrosion rate in the salt spray test, one order of magnitude less than that of AerMet 100 and 300M steels. With the increase of chromium content, the polarization resistance becomes larger, the corrosion potential shifts towards the positive direction with a value of 545 mV, and the corrosion current density decreases in electrochemical measures in 3.5wt% NaCl solutions. Because of the higher content of chromium, the ultra high strength stainless steel has a better corrosion resistance than AerMet 100 and 300M steels.

Direct deposition of graphene nanowalls on ceramic powders for the fabrication of a ceramic matrix composite

Uniform mixing of ceramic powder and graphene is of great importance for producing ceramic matrix composite. In this study, graphene nanowalls(GNWs) are directly deposited on the surface of Al2 O3 and Si3 N4 powders using chemical vapor deposition system to realize the uniform mixing. The morphology and the initial stage of the growth process are investigated. It is found that the graphitic base layer is initially formed parallel to the powder surface and is followed by the growth of graphene nanowalls perpendicular to the surface. Moreover, the lateral length of the graphene sheet could be well controlled by tuning the growth temperature. GNWs/Al2 O3 powder is consolidated by using sparking plasma sintering method and several physical properties are measured. Owing to the addition of GNWs, the electrical conductivity of the bulk alumina is significantly increased.

Microstructure and texture evolution of Mg–3Zn–1Al magnesium alloy during large-strain electroplastic rolling

Large-strain deformation by single electroplastic rolling （EPR） was imposed on AZ31 magnesium alloy strips. During EPR at low temperature （150-250℃）, numerous twins formed in the alloy. After EPR at a high temperature （350℃）, the number of twins reduced and some dynamic recrystallization （DRX） grains formed at grain boundaries and twinned regions. The synergic thermal and athermal effects generated by electropulsing, which promoted dislocation motion, induced a few small DRX grains, and ductile bandings were mainly re- sponsible for large-strain deformation during EPR. The inclination angle of the basal pole stemmed from the counterbalance of the inclina- tion direction of the basal pole between the DRX grains and deformed coarse grains.

Characteristics of Electroencephalogram Arousals of Sleep- disordered Breathing Children at Different Sleep Stages

Sleep-disordered breathing （SDB） is the most common sleep- related disorder, and it can seriously affect sleep conditions, growth, and neurocognitive function. Recent research even demonstrates that hypertensive patients with SDB are at an increased risk of developing resistant hypertension.

Magnetic Properties of Co 2D Antidot Arrays with Hexagonal Holes Using Colloidal Crystal Template Method

In this work, Co 2D antidot arrays with well-ordered hexagonal holes ranging in size from 1.3 to 6.2 μm were fabricated by colloidal crystal template method. The geometry configuration and magnetic properties of the samples were investigated. An enormous increase in coercivity and squareness, as compared with the corresponding continuous film, was observed. Magnetic properties of Co 2D antidot arrays showed a close dependence on pore diameter. According to geometric calculation, the effect of the pore diameter on magnetic properties was also discussed. The Co 2D antidot arrays obtained by this method are promising candidates for high-density information storage.