Dao Tuong Ly Kiet, Tieu Anh Kiet, Tran Bach Hoang, Pham Sang The
Faculty of Engineering and Information Sciences, University of Wollongong, Northfields Avenue, Wollongong, New South Wales 2522, Australia.
School of Chemical and Process Engineering, Faculty of Engineering and Physical Sciences, University of Leeds, 211 Clarendon Road, Woodhouse, Leeds LS2 9JT, United Kingdom.
Langmuir. 2022 Jul 12;38(27):8416-8427. doi: 10.1021/acs.langmuir.2c01022. Epub 2022 Jun 25.
In this work, several phosphate-intercalated Mg-Al layered double hydroxides (LDHs) were synthesized and evaluated as solid lubricant additives in polyalphaolefin (PAO-4) by means of tribotesting on coupled GCr15/cast iron contacts. The effects of test parameters such as normal loads, additive concentrations, and substrate surface roughness were investigated, while the LDH crystal structure received considerable attention. Several types of structural disorder after anion exchange were identified based on X-ray diffraction (XRD) analysis. The unstable structures promote feasible shearing during sliding to improve friction and wear. In addition, antiwear properties correlate well with the anion charge number or the quantity of anion in the interlayer region. Overall, the tribological performance increased in the order HPO-LDH < PO-LDH < PO-LDH < (PO)-LDH. (PO)-LDH demonstrated the best antiwear performance with a reduction of 69% of the ball volume loss compared to PAO-4 oil due to the synergy of the disordered stacking LDH sheets and flexible ring structure of the (PO) anion. Furthermore, on polished surfaces, the coefficient of friction (COF) of the (PO)-LDH sample dropped significantly by 26%, while the wear loss reduction of more than 80% was also substantial compared to the base oil sample. A performance comparison between the best-performing LDH additive was also conducted against popular nanomaterials, such as hexagonal boron nitride (BN), graphene nanoplatelets (GNPs), and titanium oxide (TiO). The performance of (PO)-LDH was close to that of GNPs.
在本研究中，合成了几种磷酸根插层的Mg-Al层状双氢氧化物（LDH），并通过在GCr15/铸铁对偶接触面上进行摩擦试验，评估其作为聚α烯烃（PAO-4）中固体润滑剂添加剂的性能。研究了诸如法向载荷、添加剂浓度和基体表面粗糙度等试验参数的影响，同时对LDH晶体结构给予了相当多的关注。基于X射线衍射（XRD）分析，识别出了阴离子交换后的几种结构无序类型。这些不稳定结构在滑动过程中促进了可行的剪切，从而改善了摩擦和磨损。此外，抗磨性能与阴离子电荷数或层间区域阴离子数量密切相关。总体而言，摩擦学性能按HPO-LDH＜PO-LDH＜PO-LDH＜(PO)-LDH的顺序增加。由于无序堆叠的LDH片层与(PO)阴离子的柔性环结构协同作用，(PO)-LDH表现出最佳的抗磨性能，与PAO-4油相比，球体积损失减少了69%。此外，在抛光表面上，(PO)-LDH样品的摩擦系数（COF）显著下降了26%，与基础油样品相比，磨损损失减少超过80%也很显著。还对性能最佳的LDH添加剂与流行的纳米材料，如六方氮化硼（BN）、石墨烯纳米片（GNP）和氧化钛（TiO）进行了性能比较。(PO)-LDH的性能与GNP相近。
