AI 5083//10 wt% SiCp nano composites have been synthesized by means of high energy ball milling followed by spark plasma sintering （SPS）. Nano composites produced via this method exhibited near-theoretical density w...AI 5083//10 wt% SiCp nano composites have been synthesized by means of high energy ball milling followed by spark plasma sintering （SPS）. Nano composites produced via this method exhibited near-theoretical density while retaining the nano-grained features. X-ray diffraction （XRD） analysis indicated that the crystalline size of the ball milled AI 5083 matrix was observed to be～25 nm and it was coarsened up to～30 nm after SPS. Nano indentation results of nano composites demonstrated a high hardness of～280 HV with an elastic modulus of 126 GPa. Wear and friction characteristics with addition of SiCp reinforcement exhibited significant improvement in terms of coefficient of friction and specific wear rate to that of nano structured AI 5083 alloy. The reduction in specific wear rate in the nanocomposite was mainly due to the change of wear mechanism from adhesive to abrasive wear with the addition of SiCp which resulted in high hardness associated with nano-grained microstructure.展开更多
ZrCoSb based half-Heusler(HH)alloys have been widely studied as a p-type thermoelectric(TE)material for power generation applications in the mid-temperature regime.However,their intrinsically high thermal conductivity...ZrCoSb based half-Heusler(HH)alloys have been widely studied as a p-type thermoelectric(TE)material for power generation applications in the mid-temperature regime.However,their intrinsically high thermal conductivity has been found to be detrimental for the improvement in their thermoelectric figure-of-merit(ZT),which presently is far below unity.In the current work,a state-of-the-art ZT~1.1 at 873 K was realized in an optimized composition of nanostructured Zr1-xHfxCoSb_(0.9)Sn_(0.1) HH alloys by employing compositional modulation i.e.grain-by-grain compositional variations,which leads to a substantial increase in its power factor coupled with a concurrent decrease in its thermal conductivity.Significant reduction in the phonon mean-free-path is observed on Hf substitution,which is comparable to the average crystallite size(~25 nm),thus leading to a very low thermal conductivity of~2.2Wm^(-1)K^(-1) at 873 K,which is amongst the lowest reported in HH alloys.The TE device characteristics,estimated using cumulative temperature dependence model for quantitative evaluation of TE performance,yielded an output power density of~10 Wcm2 with a leg efficiency of~10%in the optimized composition of nanostructured Zr_(1-x)Hf_(x)CoSb_(0.9)Sn_(0.1) HH alloys,which is comparable to the reported efficiencies of other state-of-the-art TE materials.展开更多
基金supported by Council of Scientific and Industrial Research(CSIR)under its network project(CSIR-NWP-51)entitled"Nanostructured Advanced Materials(NAM)"
文摘AI 5083//10 wt% SiCp nano composites have been synthesized by means of high energy ball milling followed by spark plasma sintering （SPS）. Nano composites produced via this method exhibited near-theoretical density while retaining the nano-grained features. X-ray diffraction （XRD） analysis indicated that the crystalline size of the ball milled AI 5083 matrix was observed to be～25 nm and it was coarsened up to～30 nm after SPS. Nano indentation results of nano composites demonstrated a high hardness of～280 HV with an elastic modulus of 126 GPa. Wear and friction characteristics with addition of SiCp reinforcement exhibited significant improvement in terms of coefficient of friction and specific wear rate to that of nano structured AI 5083 alloy. The reduction in specific wear rate in the nanocomposite was mainly due to the change of wear mechanism from adhesive to abrasive wear with the addition of SiCp which resulted in high hardness associated with nano-grained microstructure.
基金the Board of Research in Nuclear Sciences,India for the financial support under the Scheme:37(3)/14/22/2016-BRNS with BSC.Nagendra S.Chauhan acknowledges CSIR-Senior Research Fellowship.(Grant No:31/001(0430)/2014-EMR-1)The technical support rendered by Dr.Vidya Nand Singh,Mr.Radhey Shyam,and Mr.Naval Kishor Upadhyay is also gratefully acknowledged.
文摘ZrCoSb based half-Heusler(HH)alloys have been widely studied as a p-type thermoelectric(TE)material for power generation applications in the mid-temperature regime.However,their intrinsically high thermal conductivity has been found to be detrimental for the improvement in their thermoelectric figure-of-merit(ZT),which presently is far below unity.In the current work,a state-of-the-art ZT~1.1 at 873 K was realized in an optimized composition of nanostructured Zr1-xHfxCoSb_(0.9)Sn_(0.1) HH alloys by employing compositional modulation i.e.grain-by-grain compositional variations,which leads to a substantial increase in its power factor coupled with a concurrent decrease in its thermal conductivity.Significant reduction in the phonon mean-free-path is observed on Hf substitution,which is comparable to the average crystallite size(~25 nm),thus leading to a very low thermal conductivity of~2.2Wm^(-1)K^(-1) at 873 K,which is amongst the lowest reported in HH alloys.The TE device characteristics,estimated using cumulative temperature dependence model for quantitative evaluation of TE performance,yielded an output power density of~10 Wcm2 with a leg efficiency of~10%in the optimized composition of nanostructured Zr_(1-x)Hf_(x)CoSb_(0.9)Sn_(0.1) HH alloys,which is comparable to the reported efficiencies of other state-of-the-art TE materials.
