【作者】 张萍；

【导师】 陈照峰；

【作者基本信息】 南京航空航天大学 ， 材料学， 2020， 硕士

【摘要】 真空绝热板(Vacuum Insulation Panel,VIP)利用真空绝热原理,使板内具有极高的真空度以大幅降低VIP内部对流换热,并采取多种措施来降低其板内固体热传导,最大程度的综合减弱板内热传递,从而使得VIP的初始导热系数可低至1.5m W/(m·K),是目前已知的导热系数最低的材料,在冷链保温等领域有着重要的应用前景。国内VIP产品由于起步较晚,尚存在着许多关键技术未攻克,VIP的成本、寿命等问题仍需进一步研究。本文制备了一种基于秸秆粉的低成本绿色VIP,并深入研究了VIP芯材中各组分的含量对芯材的微结构以及VIP隔热性能、压缩回弹率的影响,并对其老化性能及寿命预测进行了探索。本文主要以气相二氧化硅粉末、秸秆粉、碳化硅和粘胶纤维为原料,采用干粉混合工艺、模压工艺以及真空封装工艺制备了复合芯材VIP,采用孔径与比表面积分析仪分析了复合芯材的孔结构及孔隙率,采用扫描电子显微镜和透射电子显微镜对芯材的微观结构进行了分析,采用导热系数测试仪对复合芯材VIP的隔热性能进行了测试及分析。主要成果如下:(1)研究了秸秆粉作为第二相隔热粉末的含量对复合芯材的孔结构及复合芯材VIP的隔热性能及压缩回弹率的影响。秸秆粉添加量为0～35wt.%的复合芯材,其孔径大小为182.2～205.4nm,孔隙率为78.5～85.2%,与不含秸秆粉的气相二氧化硅VIP相比其成本降低了5.24%～36.67%。复合芯材VIP的压缩率为39.55%～50.27%,回弹率为28.03%～38.55%,导热系数为5.5～7.4 m W/(m·K)。(2)研究了干燥温度和工艺对复合芯材隔热性能的影响。秸秆粉/气相二氧化硅复合芯材的最佳干燥工艺为140℃烘干60min。干燥温度过低或过高,均会导致VIP导热系数升高。(3)研究了复合芯材VIP的内压与水分含量对其导热系数的影响规律,建立了VIP导热系数公式并对其寿命进行了预测。秸秆粉/气相二氧化硅复合芯材VIP的导热系数在内压0.1～10000Pa范围内具有较低的气压敏感性,VIP服役的初期,其导热系数主要受水分含量影响;在服役后期,其导热系数主要受内压影响。基于秸秆粉的含量,复合芯材VIP在25℃、相对湿度为31%R.H.的环境下的使用寿命为7～32年。更多还原

【Abstract】 The Vacuum Insulation Panels use the principle of vacuum insulation to make the panels have a very high degree of vacuum to greatly reduce the convective heat transfer inside the VIP.Various measures are taken to reduce the solid heat transfer.Weaken the heat transfer in VIP,so that the initial thermal conductivity of VIP can be as low as 1.5 m W/(m·K).It is the currently known material with the lowest thermal conductivity,and has important application prospects in cold chain insulation and other fields.Due to the late start of domestic VIP products,there are still many key technologies that have not been conquered,and the issues of VIP cost and life need to be further studied.The goal of this article is to prepare a low-cost green VIP.The effects of the contents of each component on the microstructure of the core material,the thermal insulation properties of the VIP,and the compression and rebound rate are studied.At the same time,the VIPs’ aging performance and life prediction are explored.In this paper,fumed silica powder,straw powder,silicon carbide,and viscose fibers are used as raw materials.The VIP with hybrid core material is prepared by dry powder mixing process,molding process,and vacuum packaging process.The pore structure and porosity of the composite core material were analyzed by aperture and specific surface area analyzer,and the microstructure of the core material was analyzed by scanning electron microscope and transmission electron microscope,the thermal insulation performance of the VIP with hybrid core material was tested and analyzed using the thermal conductivity tester.The main results are as follows:(1)The effects of the content of the second phase insulation powder on the pore structure of core material and the thermal insulation performance and compression rate,rebound rate of the composite core material VIP were studied by changing the content of straw powder in the hybrid core material.The composite core material with an amount of 0wt.% to 35 wt.% straw powder addition has a pore size of 182.2nm to 205.4 nm,a porosity of 78.5% to 85.2%,and a cost reduction of 5.24% to 36.67%compared with fumed silica VIP without straw powder.The compression rate of the composite core material VIP is 39.55% to 50.27%,the rebound rate is 28.03% to 38.55%,and the thermal conductivity is 5.5 to 7.4 m W/(m ? K).(2)The influence of the drying process on the thermal insulation performance of the hybrid core material was investigated by changing the drying temperature.The results showed that the best drying process for the straw powder/fumed silica composite core material was 140 °C for 60 minutes.Too low or too high temperature will cause VIP’s thermal conductivity to increase.(3)Through experimental research and theoretical analysis,the influence of internal pressure and moisture content of the hybrid core material VIP on its thermal conductivity was discussed.The formula of VIP thermal conductivity was established and its service life was predicted.The results showed that the thermal conductivity of the straw powder/fumed silica hybrid core material VIP has a low pressure sensitivity within the range of 0.1Pa to 10000 Pa of internal pressure.In the early stage of VIP service,its thermal conductivity is mainly affected by the moisture content.In the later period,its thermal conductivity is mainly affected by the internal gas.The composite core material VIP has a service life of 7 years to 32 years in an environment of 25 °C and a relative humidity of 31% R.H.更多还原