【作者】 芦玉峰；

【导师】 肖加余； 堵永国；

【作者基本信息】 国防科学技术大学 ， 材料科学与工程， 2007， 博士

【摘要】 本文以低温烧结法制备化学计量比和高Ba含量的两组BaO-Al₂O₃-SiO₂（BAS）系微晶玻璃。设计了一种利用X射线衍射（X-ray diffraction）法测定微晶玻璃各相含量的方法。根据玻璃工艺学的基本原理,设计了化学计量比和高热膨胀系数的BAS系基础玻璃。系统研究了ZrO₂、单斜晶种对两组BAS系微晶玻璃中六方钡长石析晶和六方钡长石向单斜钡长石的晶型转变的影响。在此基础上,分别研究了晶化时间和ZrO₂含量对BAS系微晶玻璃热膨胀系数的影响,通过控制其析出晶相的种类和含量,实现了BAS系微晶玻璃热膨胀系数在较大范围内的系列化。最后,以丝网印刷、生带包覆/压制和多层共烧为基本的制备技术,研制了基于0Cr18Ni9不锈钢基板的BAS系微晶玻璃介质层和C_f/SiC复合材料的BAS系微晶玻璃抗氧化涂层,并对其性能进行了考核。采用设计的XRD方法,同时利用标准卡片上的“参比强度”值,可测定微晶玻璃中的各相含量。与Rietveld法相比,这种方法测得的结晶度的偏差小于3.2%,测得的各晶相含量的偏差小于2.6%。利用自建的定标直线测定了BAS系微晶玻璃中单斜钡长石相对于刚玉（α-Al₂O₃）的参比强度,为1.74。综合考虑成分对熔化温度、澄清温度和热膨胀系数的影响,确定了高Ba含量的BAS系基础玻璃的成分。通过添加适量B₂O₃以降低玻璃的熔炼温度。为尽量保持BAS系微晶玻璃优良高温性能,确定B₂O₃的合适添加量为6 wt%。对比研究发现,ZrO₂作为成核剂,在化学计量比BAS系微晶玻璃中促进六方钡长石向单斜钡长石的晶型转变效果最明显,同时在高热膨胀系数的BAS系微晶玻璃中能有效抑制六方钡长石向单斜钡长石的晶型转变。利用研究相变动力学的新方法（包括Ozawa等转化率法和最概然相变机理函数）分析差示扫描量热（Differential scanning calorimetry）数据,研究了六方钡长石在整个析晶过程中的非等温转变动力学。利用设计的方法分析XRD数据,研究了六方钡长石向单斜钡长石的晶型转变的等温转变动力学。进而系统研究了ZrO₂、单斜晶种对化学计量比和高Ba含量两组BAS系微晶玻璃中,六方钡长石析晶和六方钡长石向单斜钡长石的晶型转变的影响。研究发现:各设计成分的BAS系微晶玻璃中,六方钡长石的析出为整体析晶。不加成核剂,六方钡长石向单斜钡长石的晶型转变为整体析晶;添加晶种后主要转变为表面析晶。添加1-2%ZrO₂时,在晶型转变初期主要表现为表面析晶;随着晶型转变过程的进行或ZrO₂含量的增加,主要表现为整体析晶。各设计成分BAS系玻璃的最概然析晶机理函数为SB（m,n）函数,析晶过程中存在自催化的相变机制。在化学计量比BAS系微晶玻璃中,添加1-2%的ZrO₂,析晶峰值温度、析晶活化能和Avrami指数较低,六方钡长石的含量较高、晶粒较细,能显著促进六方钡长石向单斜钡长的石晶型转变。在化学计量比BAS系微晶玻璃中添加1%的ZrO₂,在850℃时保温12 h,实现了六方钡长石向单斜钡长石的完全转变。在高Ba含量的BAS系玻璃中添加2%ZrO₂能抑制晶型转变,在850℃时保温100 h不发生转变。在两组BAS系玻璃中添加晶种均有助于降低析晶活化能,促进六方钡长石和单斜钡长石的析出。单斜晶种的添加量为1%时,活化能最小,高Ba含量BAS系玻璃中的析晶峰值温度也最低。添加1%晶种的化学计量比BAS系微晶玻璃,在850℃保温2h,全部转变为单斜钡长石。在化学计量比BAS系玻璃中,通过改变ZrO₂含量,或控制晶化时间,能调节微晶玻璃中单斜钡长石和六方钡长石的相对含量,从而实现了热膨胀系数在3.1-6.67×10^-6℃^-1（40-200℃）范围内的系列化。而在高Ba含量BAS系微晶玻璃中,通过控制晶化时间,也能调节单斜钡长石和六方钡长石的相对含量,从而实现了热膨胀系数在5.21-9.70×10^-6℃^-1（40-200℃）范围内的系列化。在0Cr18Ni9不锈钢基板上,采用添加了ZrO₂的高Ba含量BAS系微晶玻璃,制备了大功率厚膜电路介质层。通过加入适量MgO和CaO部分取代BaO,抑制了晶体相的析出,BAS系微晶玻璃的烧结性能得到明显改善。成分优化后的BAS系玻璃的工程热膨胀系数为（8.08-13.97）×10^-6℃^-1（40-700℃）,较好地满足了与0Cr18Ni9不锈钢基板热膨胀系数匹配的要求。最佳配方的介质浆料制得的介质层满足国家标准的要求。部分成果已经用于合作单位的工业化生产。利用两层不同软化温度和不同热膨胀系数的BAS系微晶玻璃制备了两种双层同组分和一种双层不同组分的C_f/SiC复合材料抗氧化涂层。对比热冲击后的质量损失率和强度保留率发现,这些涂层对提高C_f/SiC复合材料的抗氧化性能均具有一定作用。更多还原

【Abstract】 Two groups of BaO-Al₂O₃-SiO₂ （BAS） glass-ceramics with stoichiometric and nonstoichiometric celsian composition were fabricated by sintering at low temperature. According to the principle of quantitative analysis by X-ray Diffraction （XRD）, a new method to determinate the crystallinity of glass-ceramics was proposed. Based on the principle of glass technology, main compositions of the two groups of BAS glass with stoichiometric and nonstoichiometric celsian were designed. The effects of ZrO₂ and celsian seeds on crystallization and phase transformation characteristics of the two groups of BAS glass-ceramics were investigated. By controlling the kinds and quantity of crystal phases in these glass-ceramics, Thermal Expansion Coefficient （TEC） of them can easily be designed over a wide range. By taking advantage of this result,a dielectric coating from the BAS glass-ceramics was prepared on 0Crl8Ni9 stainless steel surface, as well, an anti-oxidation coating also from them was prepared on carbon fiber reinforced silicon carbide （C_f/SiC） composite.The new method to determinate the crystallinity of glass-ceramics was proposed only with the intensity data for glass phase diffraction. Mass fractions of crystal-phases was calculated using "Reference Intensity Values" on Joint Committee on Powder Diffraction Standards （JCPDS） . Comparing the results calculated by the method with those by the Rietveld method, the maximum deviation of the crystallinities from experiments is 3.2 %, the maximum experimental deviation of each crystal-phase mass fractions is 2.6 %. Relative toα-Al₂O₃, Reference Intensity Values of monoclinic celsian in the BAS glass-ceramics is 1.74, which is calculated by the so-called calibrated curve method.The basic compositions of nonstoichiometric BAS glasses were designed, through considering effects of oxides in the glasses on their melting temperature, clarified temperature and TECs. B₂O₃ was selected to ruduce the melting temperature of stoichiometric BAS glasses. To preserve the glass performances at high temperature, an appropriate additive fraction of B₂O₃ may be 6 %.ZrO₂ was chosen as nucleation agent. The agent can boost phase transformation from hexacelsian to monoclinic celsian in the stoichiometric BAS glass-ceramics. Reversely, it will restrain the transformation in the nonstoichiometric BAS ones.The effects of ZrO₂ and celsian seeds on crystallization and phase transformation characteristics of the two groups of BAS glass-ceramics were investigated by Differential Scanning Calorimetry （DSC）,XRD and dilatometry, according to the isoconversional method of Ozawa and the Johnson-Mehl-Avrami equation. Crystallization characteristic of hexacelsian in each sample is bulk nucleation. Crystallization of monocelsian in the sample doped with celsian seeds characterizes surface nucleation, while it is bulk nucleation in the sample without nucleation agent. The earlier stage crystallization characteristic of monocelsian in the sample doped with 1 %-2 % ZrO₂ is surface nucleation. The crystallization characteristic of monocelsian became bulk nucleation in the later period with 1 %-2 % ZrO₂ or with higher ZrO₂ content. It is the autocatalytic kinetic model, i.e., Sestak-Berggren function, not the JMA function or the Kissinger function, that can most properly describe the processes studied for the all glasses investigated.It is revealed that a content of 1 %-2 % ZrO₂ is the most effective for crystallization and phase transformation in the BAS glass-ceramics investgated. Crystallized at 850℃for 12 h, stoichiometric BAS glass-ceramics doped with 1 % ZrO₂ is completely transformed into monocelsian. No monocelsian in nonstoichiometric BAS glass-ceramics doped with 2 % ZrO₂ can be detected when the glass-ceramics were crystallized at 850℃for 100 h. Crystallization and phase transformation in each formula for the two groups of BAS glass-ceramics doped with the seeds were able to be accelerated greatly. Crystallized at 850℃for 2 h, stoichiometric BAS glass-ceramics doped with 1 % seeds is completely transformed into monocelsian.For the stoichiometric BAS glass-ceramics, by optimizing the content of ZrO₂ or controlling the crystallization time, proportions between monoclinic celsian and hexacelsian quantity can be adjusted. Consequently, TECs from 3.1×10^-6℃^-1 to 6.67×10^-6℃^-1 （40-200℃） can easily be tailored. For the nonstoichiometric BAS glass-ceramics, by controlling the crystallization time, proportions between monoclinic celsian and hexacelsian quantity can similarly be adjusted. Also, TECs from 5.21×10^-6℃^-1to 9.70×10^-6℃^-1（40-200℃） can easily be tailored.The nonstoichiometric BAS glass-ceramics doped with ZrO₂ were employed to prepare thick film dielectric coatings on 0Crl8Ni9 stainless steel substrate. BaO is partially substituted by MgO and CaO in the BAS glass-ceramics, which can decrease the sintering temperature and increase the crystallization temperature, and thus restrain the crystallization. As a result, the sintering processability are obviously modified. TEC of the thick film for the BAS glass-ceramics can match that of 0Crl8Ni9 stainless steel substrate. The coating can meet the requirement of thick film circuit for multilayer co-firing technology. Some results from the present work have been applied into production of the cooperating company.Two different compositions of BAS glass-ceramics, with different soften points and TECs, were employed to prepare three structures of coatings. The all coatings have protection functions for C_f/SiC composite.更多还原