High-temperature reactivity in the ZrW2O8-Cu system
High-temperature reactivity in the ZrW2O8-Cu system
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DOI：
10.1016/s1359-6462(96)00481-2
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发表时间：
1997-05-01
影响因子：
6
通讯作者：
Dunand, DC
中科院分区：
文献类型：
--
作者：
Verdon, C;Dunand, DC
钨酸锆（ZrW，OJ）在0.3 ~ 1050 K的温度范围内具有负的热膨胀系数（CTB）。这种性质在大约30年前就有报道（1），但直到最近才解决了这种化合物的结构，进行了低温CTE测量，并提出了负CTE的物理解释（2）。钨酸锆在1105 ℃和1257 ℃之间是稳定的（3），在室温下是亚稳定的，当在空气中加热到750 ℃以上时分解成基本氧化物ZrO和WOs（4）。除了负CTE的基本物理利益之外，该材料对于低热膨胀应用具有很大的技术利益。然而，其复杂的合成，包括在1200 ℃以上的温度下加热许多天，阻碍了其在工程应用中的大规模使用。最近发现的合成（2）的更快速前体方法可能会改变这种情况。作为复合材料中的增强体，钨酸锆可以比具有正CTB的陶瓷更有效地降低复合材料的总体热膨胀。如果使用金属基体，所得复合材料还将表现出高导热性，应用于微电子设备的散热器（CTE与硅或氧化铝的CTE匹配）或受热波动（零CTE）影响的高精度光学元件（5）。作为基质，铜是主要的候选者，因为它在所有金属中具有仅次于银的第二高热导率，并且因为它可以在由ZrW，O，.此外，铜已经广泛用于电子工业，并且易于焊接。
Zirconium tungstate (ZrW, OJ exhibits the unusual property of a negative coefficient of thermal expansion (CTB) over a Iwide range of temperature, from 0.3 to 1050 K. This property was reported about thirty years ago (l), but only recently were the structure of this compound solved, the low-temperature CTE measurement performed and a physical explanation for the negative CTE proposed (2). Zirconium tungstate, which is stable between 1105 C and 1257 C (3), is metastable at room temperature and decomposes into the base oxides ZrO, and WOs when heated above 750 C in air (4). Beside the fundamental physical interest of a negative CTE, the material is of great technological interest for low thermal expansion applications. However its complicated synthesis, which includes many days of heating at temperature above 12OO” C, has prevented its large-scale use in engineering applications. The recent discovery of a more rapid precursor approach to the synthesis (2) is likely to change this situation. As a reinforcement in a composite, zirconium tungstate can reduce the overall thermal expansion of the composite much more effectively than a ceramic with positive CTB. If a metallic matrix is used, the resulting composite will also exhibit high thermal conductivity, with applications such as heat sink for microelectronics devices (CTE matching that of silicon or alumina) or high precision optical elements subjected to thermal fluctuation (zero CTE)(5). As a matrix, copper is prime candidate, because it has the second highest thermal conductivity of all metals after silver, and because it can be easily processed within the temperature window imposed by the metastability of ZrW, O,. Moreover, copper is already widely used in electronics industry and can be easily soldered.