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Juan P. Escobedo Ellen K. Cerreta Daniel T. Martinez Carl P. Trujillo Ricardo A. Lebensohn George T. Gray III 《Metallurgical and Materials Transactions A》2014,45(13):5877-5882
The influence of temperature on the dynamic tensile behavior of Zr has been investigated. Bullet-shaped Zr samples with two different textures were dynamically extruded at room temperature and 523 K (250 °C). A higher ductility was measured for samples deformed at elevated temperature as compared to those extruded at room temperature. This difference in ductility is discussed in terms of zirconium’s ability to accommodate plastic deformation via thermally enhanced slip activity, as evidenced by examination of the deformed microstructures. 相似文献
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Clay aerogels have many advantages as one of the lowest density family of materials current technology can provide; they possess very low thermal conductivities, high porosities, and high surface areas. Although the mechanical properties of native clay aerogels are rather low, incorporating water‐dispersible polymers into the clay gel before they are processed into aerogel forms can easily produce more robust, low‐density composites. Various processing modifications and additives can be employed to strengthen the aerogel material, but currently, the materials have some notable weaknesses in abrasion resistance, water absorption, and flexural properties. In this study, we employed a low‐cost rubber coating material to quickly and efficiently address all three of these problems. After coating, the aerogels gained significant mechanical reinforcement, a 20‐fold increase in flexural modulus and a 15‐fold increase in yield stress, while exhibiting an increase of only 8% in the thermal conductivity. Improvements such as these can improve the commercial applicability of clay/polymer aerogels as thermal insulation materials. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
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Rocco P. Viggiano III Edward E. Ball Ronald E. Park Karl W. Haider David A. Schiraldi 《应用聚合物科学杂志》2015,132(39)
The feasibility of incorporating ground recycled polyurethane (PU) foam into clay/polymer aerogels was demonstrated, and a range of compositions were prepared and characterized to determine the effect of variation in the formulations on density and mechanical properties of the resulting materials. This study followed a modified combinatorial approach. Initially, experiments were performed in water using either sodium exchanged montmorillonite or laponite clay, poly(vinyl alcohol) (PVOH) solution as the polymer binder, and the recycled PU foam. Freezing and freeze‐drying the aqueous gels produced aerogels, which were characterized through density and mechanical testing, scanning electron microscopy, and thermal gravimetric analysis. The study was expanded by exploring alternative binder chemistries, including the use of an alginate polymer in place of the PVOH or adding a polyisocyanate as a crosslinking agent for PVOH. The effect of recycled PU foam content, clay type and level, and binder type and level on the mechanical properties of the aerogels were determined and will be discussed herein. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42586. 相似文献
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Claire D. Stevenson Andrew D. Ramsey Owen T. Nevin William Sinclair 《Landscape Research》2013,38(4):553-559
Abstract The grey squirrel Sciurus carolinensis is thought to have contributed to the decline of red squirrel S. vulgaris populations in the UK through resource competition and disease spread. This study used mtDNA sequencing to assess patterns of grey squirrel dispersal in the UK. Patterns of genetic variation within the dloop sequence were characterised for seven grey squirrel populations. Infiltration directions and potential barriers to dispersal are identified and discussed, with a focus on Cumbria, a county at the forefront of grey squirrel expansion. Understanding the dynamics of grey squirrel dispersal will aid their management at a landscape scale and enhance the conservation of red squirrels. 相似文献