成核-生长型液-液分相对无铅低温熔剂性能的影响

Influence of Nucleation-growth Liquid-liquid Phase Partition on Properties of Lead-free Low Temperature Frit

采用高温熔制结合低温热处理制备成核-生长型液-液纳米级分相的低温熔剂,研究了分相结构对熔剂的光泽度、光泽损失、显微维氏硬度等性能的影响,用HSM和DSC研究熔剂高温变化过程中的特征点并找出了合适的热处理工艺参数,根据XRD分析了熔剂的晶相组成,用SEM和TEM观察了分相显微形貌,根据FTIR分析了分相的显微结构,根据熔剂的性能研究了分相结构改善其性能的机理。结果表明:与水淬工艺样品相比,适当的热处理可调控分散相的尺寸、体积分数和分布,使熔剂的显微硬度和耐磨性显著提高。随着热处理温度的提高熔剂的光泽损失呈"Z"字形变化,而显微硬度的变化趋势与其相反。热处理温度为630℃时光泽损失最小(26.4%),显微硬度最大(6202 MPa),耐磨等级达到3级(750转)。随着热处理温度的提高分散相的液滴尺寸和体积分数呈开口向下的抛物线变化。分相使碱-硼-铈富集在分散相中,分散相的尺寸和体积分数越大则连续相中的游离氧减少,即O/Si比减小,[SiO_(4)]及桥氧增多,网络聚合度提高。同时,熔剂具有致密的表面层,分相结构存在于熔剂内部,富碱-硼-铈相以滴状分散嵌入在富硅氧连续相中,富硅氧对碱硼相的保护使熔剂的耐磨性和显微硬度提高。

The nucleation-growth type liquid-liquid nano-phase partitioned low-temperature frits were prepared via a two-step process: high-temperature melting and low-temperature heat treatment. The influence of the phase-partition on the gloss, gloss loss, microhardness and other properties of the ABS* leadfree low-temperature frit were assessed by means of high temperature microscopy, differential scanning calorimetry, X-ray diffractometer, scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. The results show that the size, volume fraction and distribution of the dispersed phase can be effectively adjusted with the aid of appropriate heat treatment processes.The heat-treated frits present microhardness and wear resistance much higher than those of the waterquenched ones. With the increasing heat treatment temperature, the gloss loss of the frits experienced a "Z" shaped variation and the microhardness experienced a reverse trend. Being heat treated at 630℃,the frit presents the smallest gloss loss of 26.4%, the largest hardness of 6202 MPa, whilst its wear resistance can be classified as grade 2(750 revolutions). The size and the volume of the phase-partition generated dispersive droplets show a downward parabola-like variation as the heat treatment temperature increases. The phase partition facilitates the enrichment of alkali, cerium and boron in the dispersed phase.As the size and volume fraction of the dispersed phases in the frit increases, the free oxygen in the continuous matrix decreases, that is, the O/Si ratio decreases, while the amount of [SiO_(4)] and bridge oxygen increases and the polymerization degree of the network increases. Besides the frit has a dense surface layer, namely the phase-partitioning structure exists inside the frit. The phase rich in alkali, cerium and boron dispersed and embedded in the Si-rich continuous matrix as droplets, in other words the former is protected by the later one. Therefore, the wear resistance and microhardness of the frits were enhanced.