Search

Microstructure evolution and mechanical properties of the aging treated AlN/AZ91 composites were systematically investigated by optical microscopy (OM), high resolution scanning electron microscopy (HRSEM) with an energy dispersive spectrum (EDS), and high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM). The results show that the higher fracture elongation (14 ± 1%) and ultimate tensile strength (275 ± 6 MPa) were simultaneously obtained in the peak-aged AlN/AZ91 composites. Comparied with AZ91 matrix alloy, the strength was increased by about 44% and the elongation was approximately five times higher, which mainly attributed to the precipitation of nano-sized γ-Mg 17 Al 12 phase and the activation of non-basal slip systems induced by in-situ AlN particles at room temperature. However, the in-situ formation of AlN reinforcements consumed part of Al element in the matrix alloy, which resulted into the volume fraction decreasing of γ-Mg 17 Al 12 precipitates, and then the age hardening and strengthening efficiency were reduced in the AlN/AZ91 composites. On the other hand, the mismatch of thermal expansion coefficient between AlN particles and AZ91 matrix generated high density dislocations around AlN particles, which promoted the precipitation of γ-Mg 17 Al 12 phase, and then the peak aging time and temperature were decreased. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metal Materials & Engineering is the property of Northwest Institute for Nonferrous Metal Research and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Lithium ion batteries play a prominent role as an energy storage device with increasing importance in various sectors. Based on reasonable power and energy density of Li-ion batteries, they occupy a huge market share on consumer market such portable electronic devices and electro mobility. Besides that, stationary applications have a strong market development. One key role could be grid support in an energy system with high share of renewable energy. In this case balancing power such as primary control reserve may utilize lithium battery systems as most promising technology because of its efficiency and cost structure. In this paper a correlation between cycling at various states of charges (SOC) and its capacity loss of commercial lithium ion batteries are shown. The investigated chemistry consists of a graphite based anode and LiNi 0.80 Co 0.15 Al 0.05 O 2 (NCA) oxide based cathode. Using cyclic voltammetry allows showing the physico chemical impact of degradation mechanism. One aspect is the change in crystal structure of the cathode material NCA by cycling around specific SOC with small depth of discharge (DOD). There is a correlation between lithium ion battery lifetime with NCA based cathode and SOC dependent cycling with small DODs, which has a huge impact on optimization battery storage systems for single or multi use cases. [ABSTRACT FROM AUTHOR]

YAl 2p /Mg-14Li-1Al composite was made by a stir-casting technique. The aging behavior of the composite was investigated using hardness test, differential scanning calorimetry, and X-ray diffraction. The results show that the microhardness variations of both the matrix alloy and its composite are related to the precipitation and decomposition of θ-MgLi 2 Al phase. The strengthening of the composite is from the addition of YAl 2 particulates and the precipitation in matrix alloy. The former contribution is stable, but the latter is unstable and depends on the aging behavior. The addition of YAl 2 particulates delays occurring of the aging behavior of composite. [ABSTRACT FROM AUTHOR]

Abstract: Three statistical poly(L-lactide-co--caprolactone) (PLCL) copolymers of 70% L-lactide content having different chain microstructures ranging from moderate blocky to random ( and 0.92, respectively) were characterized by DSC, GPC and 1H and 13C NMR. The results demonstrate that higher randomness character () limits the capability of crystallization of LA-unit sequences shifting the melting temperature of the copolymers to lower values and reducing the crystallinity fraction substantially. The effect of different distributions of sequences of PLCL on crystallization and phase behavior was also studied for different storage times at room temperature () by DSC. The mechanical properties were evaluated by tensile tests during aging. The PLCL showing a random character closest to the Bernoullian distribution of sequences () was found to exhibit higher strain capability and strain recovery values and is less prone to supramolecular arrangements. However, as a result of aging, L-lactide sequence blocks in the other PLCLs of smaller randomness character tend to crystallize prompting to a double behavior indicative of the existence of phase separation into two compositionally different amorphous phases. Physical aging leads also to dramatic changes in tensile behavior of the moderate blocky PLCLs that evolved from being an elastomeric to be partly a glassy semicrystalline thermoplastic, and, thus, can eventually condition its potential uses for medical devices. [Copyright &y& Elsevier]