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The development and design of fillers aid in improving the tribological performances of friction materials. Herein, the effects of the aspect ratio of mullite whisker on the tribological properties were studied. Mullite whiskers were prepared by the sol–gel process and the aspect ratio of the whisker was controlled by introducing aluminum fluoride (AlF3). The aspect ratio increased significantly at first and then decreased with increasing the contents of AlF3. The experimental results show that higher aspect ratio whiskers stabilized the friction coefficient while increased the wear rate. In addition, the composite with mullite whisker grown in excessive AlF3 (20%) resulted in a higher friction coefficient compared to adding inadequate AlF3 (10%). The Scanning Electron Microscope (SEM) and Energy Dispersive X‐Ray Spectroscopy (EDX) results indicated that higher aspect ratio of whisker was more likely to fall off from matrix which sequentially being compacted and formed contact plateaus during the friction process. In conclusion, it was found that abrasive wear and adhesive wear were the dominant wear mechanism. Highlights: The aspect ratio of mullite whisker was controlled within the range of 6 ~ 21.The tribological properties of whiskers reinforced composites were studied.The morphology of the mullite whisker affects the friction stability.The flaky mullite whisker can improve wear resistance of the composites. [ABSTRACT FROM AUTHOR]

A composite-hydroxide mediated (CHM) method was utilized for the synthesis of CuO peony-flower nanostructures under temperatures ranging between 25 and 160 °C. The CHM mechanism was confirmed through X-ray Powder Diffraction (XRD) and a Thermo-Gravimetric Differential Scanning Calorimeter (TG-DSC). Cu(NO3)2 was shown to transform into Cu(OH)2 in the mixed alkalis (NaOH/KOH); the reaction was facilitated by the solvent properties of the mixed alkalis. Cu(OH)2 subsequently consumed H2O in the adsorption of the mixed alkalis at 25∼65 °C. At higher reaction temperatures (>65 °C), the Cu(OH)2 was seen to decompose at an accelerated rate. Therefore, crystalline CuO could be obtained not only above 65 °C but also at 25 °C. The crystal morphology and structure of CuO were examined through Filed Emission Scanning Electron Microscopy (FE-SEM) and Transmission Electron Microscopy (TEM). It was determined that the CuO peony-flower had a polycrystalline structure composed of single crystalline CuO petals. Using the Selected Area Electron Diffraction (SAED) results, the rings were indexed as (002), (111), (112), (202) and (−113), which was in agreement with the XRD results. With increasing temperature, the CuO flower petals self-assembled through random aggregation and gathered CuO nanorod parts, which led to incomplete CuO flower petals through orientated aggregation. Prolonged reaction time led to the growth of CuO flower petals in the direction of [001]. An ideal CuO flower structure was observed through TEM observation. [ABSTRACT FROM AUTHOR]