中文摘要：

以TiO2纳米球（TiNSs）和纳米管（TiNTs）为分散相,去离子H_2O为连续相,通过“两步法”制备混合TiO2-H_2O纳米流体,研究了TiNSs和TiNTs浓度比以及纳米粒子总浓度对混合纳米流体稳定性和导热性能的影响。采用相对吸光度变化评价了混合纳米流体的稳定性,使用闪光法导热仪测量了混合纳米流体的导热系数。结果显示,混合纳米流体相对吸光度变化随TiNTs浓度增大先减小后增大,说明混合纳米流体稳定性先提高后下降;TiNSs和TiNTs浓度比相同时,混合纳米流体相对吸光度变化随纳米粒子总浓度增加而减小,说明其稳定性有所提高。制备完成后静置,混合纳米流体导热系数相比单组份TiNSs纳米流体下降幅度较小。从TiNSs和TiNTs间的空位作用力及粘度变化的角度分析了混合纳米流体稳定性变化的原因。

英文摘要：

Hybrid TiO2-H2O nanofluids were prepared by dispersing TiO2 nanospheres （TiNSs） and nanotubes （TiNTs） in deionized water. Influence of TiNSs/TiNTs concentration ratio and total TiO2 concentration on sta-bility and thermal conductivities were investigated. Stability of hybrid nanofluids was evaluated by relative ab-sorbance change, and thermal conductivities were measured by Nanoflash. The results indicated that relative ab-sorbance change of hybrid nanofluids first decreased and then increased with increase in TiNTs concentration, which revealed that stability of hybrid nanofluids first improved and then deteriorated. Relative absorbance change of hybrid nanofluids decreased with increase in total TiO2 concentration, which revealed stability im-provement of hybrid nanofluids. Hybrid nanofluids showed smaller decrease in thermal conductivities compared to individual TiNSs nanofluids after a period of time. Stability of hybrid nanofluids was analyzed by depletion in-teraction and viscosity enhancement.