摘要
随着军事和民用技术的快速发展,对航空、户外等领域所用器件在复杂环境下的稳定性提出了更为严格的要求.这些器件经常需要在较大的温度变化范围内工作,而温度变化所带来的材料体积变化是器件结构受损,功能失效的重要原因之一.因此,如航空航天设备中所用的精密结构件不仅需要具有优秀的导电、导热性能,还需要保证其在温度变化过程中具有较低的热膨胀系数.因此,研究制备具有近零膨胀性能的材料便成为解决这些问题的重要方法之一.在本研究中,作者通过改变烧结温度,制备出一系列介孔铁电PbTiO3(PTO)陶瓷,通过测试结果展示了材料的热导率、热膨胀系数与烧结温度的关系.进一步通过三维重构技术(Tomography)与高角度环形暗场像(high angle annular dark field,HAADF),分析了改变烧结温度对于介孔尺寸、分布密度的影响,以及单个介孔表面附近的铁电屏蔽效应影响范围,从而解释了烧结温度的变化与介孔的分布密度、尺寸大小以及热膨胀行为之间的紧密联系.随着烧结温度的降低,介孔对材料铁电屏蔽效应的总区域占比逐渐升高,从而使材料正膨胀系数增大,导致材料表现出近零膨胀.为进一步提高材料的热导率,提升材料的多功能性,将这一材料与石墨烯进行复合,通过改变烧结温度与石墨烯的复合比例,进一步使材料的热膨胀系数趋近于零膨胀,并通过调整烧结温度与复合比例,得到膨胀系数低至 7×10-7℃-1,热导率比单相陶瓷提升约 65%的近零膨胀复合陶瓷.这种材料可以在芯片封装,航天器外壳,通讯设备等材料领域得到进一步广泛应用的空间.
Abstract
With the rapid development of military and civilian technologies,more stringent requirements have been imposed on the stability of devices used in aviation and outdoor environments under complex conditions.These devices often need to be operated within a large temperature range.The volume change of these devices caused by temperature fluctuations is one of the important reasons for their structure damage and functional failure.Materials with near-zero thermal expansion are one kind of important ones to solve above-mentioned problems.In this study,we prepared a series of mesoporous ferroelectric PbTiO3(PTO)ceramics by changing the sintering temperature.The relationship between thermal conductivity,coefficient of thermal expansion and sintering temperature was demonstrated.Three-dimensional reconstruction technology(Tomography)and high-angle annular dark-field imaging(HAADF)were used to investigate the effect of sintering temperature on mesoporous size,distribution density,and the range of ferroelectric shielding effects near single mesopore polarization surfaces.The relationship between sintering temperature and the distribution density,size,and thermal expansion behavior of mesopores was discussed.As the sintering temperature decreased,the increase of the total area proportion of mesopores to ferroelectric shielding effects led to an increase in the positive thermal expansion coefficient,corresponding to near-zero thermal expansion properties.To further improve the thermal conductivity and reduce the coefficient of thermal expansion,the PTO material was coupled with graphene materials.By changing the sintering temperature and graphene content,the coefficient of thermal expansion was further reduced.By adjusting the sintering temperature and composite ratio,a near-zero expansion composite ceramic with a low coefficient of thermal expansion of 7×10-7℃-1 and a thermal conductivity about 65%higher than that of a single-phase ceramic was obtained.This material has further extensive applications in chip packaging,spacecraft shells,and communication equipment.
基金项目
国家重点研发计划(2017YFB0703100)
浙江省自然科学基金重大项目(LD21E020002)
万方数据