| Carbon fiber reinforced cement-based composites(CFRC)were a new type of functional materials,which was mainly applied in the areas of low grade thermal power generation,large scale and low cost energy harvesting or efficient heating.At present,the low CFRC-Seebeck coefficient was one of the main causes leading to the low thermoelectric performance,which limited the application of CFRC in the areas of large-scale energy harvesting or high efficiency heating.In this paper,the optimization approaches of enhancing the Seebeck coefficient of CFRC were obtained by measuring the Seebeck coefficient of matallic oxide,ball milling treatment of metal oxides,ball milling metal oxides-expanded graphite,high content metal oxide cement-based composites and the CFRC containing high content metallic oxide.And the simulation experiment of CFRC solar radiation energy harvesting was studied,which converted heat energy into electrical energy.(1)The Seebeck coefficient of metal oxide,metal oxide milled for 12 h and expanded graphite-metal oxide milled for 12 h were investigated.The results shown that the Seebeck coefficient of MnO2 and Ni2O3 were 2.28 mV/℃ and 2.57 mV/℃ respectively.And the Seebeck coefficient of MnO2 and Ni2O3 milled for 12 h were 2.57mV/℃ and 21 mV/℃ respectively.The Seebeck coefficient of MnO2 and Ni2O3 were enhanced by milled for 12 h,and the Seebeck coefficient of Ni2O3 was significantly higher than that of MnO2.The Seebeck coefficient 13.00 mV/℃ and the conductivity6.70 S/cm of 5.0 wt% expanded graphite-ball milling MnO2 were obtained.And the Seebeck coefficient of 3.0 wt% expanded graphite-ball milling Ni2O3 was enhanced into22.00 mV/℃,which conductivity was 7.75 S/cm.The addition of expanded graphite into ball milling metal oxides significantly improved the conductivity of composites,but the enhancement of Seebeck coefficient was not significant.(2)The high mass fraction of metallic oxide had been added into cement matrix or carbon fiber reinforced cement-based composites.In which,the metallic oxide included Ni2O3,Fe2O3,Co2O3 and MnO2.When the contents of metallic oxide were 75 wt%,the Seebeck coefficient of cement-based composites were 59.00 mV/o C,11.50 mV/℃,2.80 m V/℃,1.90 mV/℃,respectively.As the contents of metallic oxide were decreased to60 wt%,the Seebeck coefficient of metallic oxide reinforced cement-based composites were 43.00 m V/℃,8.20 mV/℃,2.80 mV/℃,0.10 mV/ ℃,successively.For CFRC,the Seebeck coefficient were 300.00 mV/℃,86.00 mV/o C,56.00 mV/℃,13.00 mV/ ℃ with metallic oxide(Co2O3,Ni2O3,MnO2,Fe2O3)contents of 45 wt%.When the contents of metallic oxide(Co2O3,Ni2O3,Fe2O3,MnO2)were up to 75 wt%,the Seebeck coefficient of CFRC were 275.00 mV/℃,25.00 mV/℃,6.80 mV/℃,6.00 mV/ ℃,respectively.The contents of metal oxide had great influence on the Seebeck coefficient of cement-based composites and CFRC.The Seebeck coefficient of CFRC had been increased several orders of magnitude(about 3-4 orders)by adding the metallic oxide.Compared with cement-based composites,metallic oxide had prominent enhancement effect on the Seebeck coefficient of CFRC.(3)Seebeck coefficient,electrical conductivity and thermal conductivity of CFRC were measured to obtain the thermoelectric figure of merit and maximum power output.The CFRC specimen with 1.0 wt% carbon fiber possesses the maximum figure of merit of 1.334×10-7 at 27°C.The harvested energy of CFRC per square meter was up to8.4×10-6J over 420 minutes irradiation,while its surface temperature reserved 68°C.4-5 μw powers could be achieved by one square meter CFRC slab with thickness of 20 mm,under a temperature difference of about 62 ℃. |
