预处理方法对炭化木基复合相变储能材料性能的影响

Effect of Pretreatment Methods on Properties of Carbonized Wood-based Composite Phase Change Energy Storage Materials

以天然轻木(NW)为原料,采用水热预处理和酸性亚氯酸钠预处理方法分别脱除半纤维素和木质素,制得脱半纤维素轻木(HW)和脱木质素轻木(LW);再经炭化后分别得到未处理炭化木(CW)、脱木质素炭化木(CLW)和脱半纤维素炭化木(CHW);进一步封装石蜡(PW)后制得炭化木基复合相变储能材料CLWP和CHWP。采用SEM、FT-IR、XRD、TG/DTG和N 2吸附/脱附等方法,分析了化学成分脱除和炭化过程对轻木基体的影响。研究结果表明:脱半纤维素和脱木质素处理均不会破坏轻木原有的三维多孔蜂窝状结构,也不会破坏纤维素的结构,且HW的热稳定性优于LW;而经炭化处理后炭化木的体积明显变小,CHW的体积收缩率为56%,低于CLW(60%);同时CHW比表面积达到了127.2 m^(2)/g,高于CLW的102.9 m^(2)/g。CLWP和CHWP的封装效率分别为93.2%和96.1%,熔融潜热分别为187.6和193.7 J/g,石蜡很好地填充在2种炭化木的微米级孔道中,封装过程中仅发生物理结合,不存在化学反应。在模拟太阳光照下,CHWP和CLWP均能利用太阳光将自身温度加热至55℃以上,且CHWP在加热和冷却过程中温度均略高于CLWP,表明脱半纤维素预处理的炭化木所制备的复合相变储能材料具有更优的光热转换效率及温度调节能力。

Using natural balsa(Ochroma lagopus)wood(NW)as raw material,hemicellulose and lignin were removed by hydrothermal pretreatment and acidic sodium chlorite pretreatment to produce the desiccated hemicellulose balsa wood(HW)and the desiccated lignin balsa wood(LW).Then,carbonization was performed to obtain the untreated carbonized wood(CW),the delignified carbonized wood(CLW)and the delignified hemicellulose carbonized wood(CHW).Eventually,the charred wood-based composite phase change energy storage materials(CLWP and CHWP)were produced after further encapsulation of paraffin wax(PW).The effects of chemical composition removal and charring processes on the balsa wood matrix were analyzed by SEM,FT-IR,XRD,TG/DTG and N 2 adsorption/desorption isotherms.The results showed that both dehemicellulose and delignification treatments would neither destroy the original three-dimensional porous honeycomb structure of balsa wood nor the structure of cellulose.Moreover,the thermal stability of HW was better than that of LW.Whereas the volume of charred wood became significantly smaller after charring treatment,the volume shrinkage rate of CHW was 56%,which was lower than that of CLW(60%).Meanwhile,the specific surface area of CHW reached 127.2 m^(2)/g,which was higher than that of CLW at 102.9 m^(2)/g.The encapsulation efficiencies of CLWP and CHWP were 93.2%and 96.1%and the latent heats of fusion were 187.6 and 193.7 J/g,respectively.Paraffin wax filled in the micron-sized pores of the two kinds of charred woods well,and only physical binding occurred during encapsulation without chemical reactions.Under the simulated solar illumination,both CHWP and CLWP could use sunlight to heat themselves to above 55℃,and the temperature of CHWP was slightly higher than that of CLWP during both heating and cooling,indicating that the composite phase change energy storage materials prepared from the desiccated hemicellulose pretreated charred wood had better photothermal conversion efficiency and temperature regulation ability.