材料期刊网

NZP材料因其具有可调节的低热膨胀性在在热冲击方面有潜在应用,而且NZP材料还具有良好的化学和热稳定性,还经常被作为陶瓷核废料中放射性核元素的封装和固定的候选材料.NZP型晶体结构允许使用大量的离子替代,使其产生了热膨胀的可调性以及离子导电性.然而,NZP在整块材料中制作起来非常困难,因为其过程需要保证高温和很长的烧结时间.通过对磷酸盐玻璃使用玻璃反应烧结工艺,在一种低温替代路线中获得了含有钨(IV)、锡(IV)的NZP结晶相.通过使用微波加热以及传统的熔炼和铸造技术,制备了一种含有适量NaPO3-Sn(II)O-W(VI)O3化合物的玻璃.粉碎后,玻璃粉末压于室温下冷却.将绿色的弹丸在烧结反应温度下分别经历不同的时间段进行固化.差热(DTA)实验中,结果显示不同的参数影响着NZP相的性能.在特定条件如玻璃的初始位置小于100 μm的玻璃颗粒度及在大气环境下固化,能够得到一种含有单一晶相的玻璃陶瓷,且晶相具有NZP型晶体结构.烧结过程中需要有氧的存在,但氧分压的提高并没有使NZP相的含量有所改善.此外,温度要严格控制高于710 ℃,保证获得的NZP玻璃陶瓷中不含有任何次晶相.

NZP materials because of its adjustable low thermal expansion has potential applications in the thermal shock, and NZP materials also has good chemical and thermal stability, also are frequently used as a ceramic radioactive element in waste package and fixed candidate materials.The NZP-type crystal structure allows a large number of ionic substitutions which leads to ceramics with adjustable thermal expansion properties or interesting ionic conductivity.However, NZP is difficult to fabricate into monoliths because it requires both high temperatures and long sintering times.An alternative low temperature route to obtain a tungsten(IV) and tin(IV) containing NZP crystalline phase uses a process of glass reactive sintering of a phosphate glass.Using a microwave oven, a glass with the appropriate composition in the NaPO3-Sn(II)O-W(VI)O3 ternary diagram is prepared by a conventional melting and casting technique.After crushing, the glass powder is pressed at room temperature.The green pellet is cured during various times at temperatures where glass reactive sintering takes place.DTA experiments, we have shown that different parameters influence the achievement of NZP phase.Consequently,specific conditions, such as initial glass composition,lass particle size lower than 100 μm, curing conducted under air, are required to obtain a glass-ceramic with a single crystalline phase with the NZP-type crystal structure.Sintering process requires the presence of aerobic, but the improvement of oxygen partial pressure of NZP phase content didn't make improvement.In addition, to strictly control the temperature higher than 710 ℃, guaranteed the NZP does not contain any phase of glass ceramic.