γ輻照誘導(dǎo)表面氧化對(duì)聚醚醚酮（PEEK）摩擦學(xué)性能的影響
Infuence of gamma irradiation?induced surface oxidation on tribological property of polyetheretherketone (PEEK)
Liqiang Chai，Beibei Zhang，Li Qiao，Peng Wang，Lijun Weng
DOI：10.1007/s00289-021-03825-4
文章鏈接：
https://link.springer.com/article/10.1007/s00289-021-03825-4
摘要：
本文研究了被劑量高達(dá)20MGy的伽馬射線(xiàn)照射過(guò)后的半結(jié)晶材料PEEK表面降解和內(nèi)部結(jié)構(gòu)變化對(duì)其摩擦學(xué)行為的影響。通過(guò)X射線(xiàn)光電子能譜分析發(fā)現(xiàn)受照射的PEEK樣品表面上C=O和O-C=O官能團(tuán)的百分比含量增加，這表明PEEK表面降解主要形式是輻射誘導(dǎo)的氧化導(dǎo)致的。通過(guò)掃描電鏡結(jié)果發(fā)現(xiàn)，當(dāng)輻照劑量超過(guò)10 MGy時(shí)，PEEK樣品會(huì)出現(xiàn)微孔、微裂紋等表面形貌缺陷，同時(shí)摩擦實(shí)驗(yàn)發(fā)現(xiàn)，由于表面氧化層的存在，輻照后的PEEK表面靜摩擦系數(shù)增大。此外，當(dāng)劑量超過(guò)1MGy時(shí)，輻照后PEEK表面的穩(wěn)態(tài)動(dòng)摩擦系數(shù)逐漸降低。表面氧化產(chǎn)物起三體滾動(dòng)作用，導(dǎo)致動(dòng)摩擦系數(shù)下降。然而，與未輻照樣品相比，相應(yīng)的磨損率增加了一個(gè)數(shù)量級(jí)。
關(guān)鍵詞：伽馬輻照；表面氧化；PEEK；摩擦磨損
Abstract:
In this paper, the semicrystalline PEEK was irradiated in the atmosphere by gamma rays with a dose up to 20 MGy. The influence of the surface degradation and the internal structural changes on the tribological behavior of PEEK was investigated. X-ray photoelectron spectroscopy analysis shows an increase in the percentage of C=O and O–C=O functional groups on the surface of irradiated PEEK samples. It reveals that irradiation-induced oxidation is the primary form of degradation on the PEEK surface. Scanning electron microscopy results indicate that the surface morphology defects such as micropores and microcracks appear when the irradiation dose exceeds 10 MGy. The friction experiments show that the static friction coefficient of the irradiated PEEK surface increases due to the existence of the surface oxide layer, and the appearance of a shorter run-in period attributes to the formation of uniform and stable transfer film in the initial stage of friction. In addition, when the dose is more than 1 MGy, the steady-state dynamic friction coefficient of the irradiated PEEK surface gradually decreases. The surface oxidation products play a rolling effect of three bodies, resulting in the fall of the dynamic friction coefficient. However, the corresponding wear rate increases by one order of magnitude compared to that of the unirradiated sample.
Keywords：Gamma irradiation；Surface oxidation；PEEK；Friction and wear
圖1 原始和 20 MGy 劑量輻照 PEEK 的表面和轉(zhuǎn)移膜的拉曼光譜
圖2 不同輻射劑量前后PEEK去除氧化層的磨損率
圖3 不同輻照劑量去除氧化層前后PEEK的平均穩(wěn)態(tài)摩擦系數(shù)。插圖顯示去除氧化層前后PEEK a和b的相應(yīng)摩擦系數(shù)曲線(xiàn)
結(jié)論：在這項(xiàng)工作中，研究了環(huán)境空氣中高達(dá)20MGy劑量的伽馬射線(xiàn)輻照PEEK的表面和內(nèi)部結(jié)構(gòu)的變化。還詳細(xì)討論了伽馬輻射引起的表面降解對(duì)PEEK摩擦學(xué)性能的影響。可以得出以下結(jié)論：
1.輻射引起的氧化是PEEK表面降解的主要形式。隨著輻照劑量的增加，表面出現(xiàn)氧化降解層，表面形貌缺陷增多。
2.力學(xué)性能測(cè)試表明，輻照氧化導(dǎo)致PEEK表面硬度降低。
3.摩擦結(jié)果表明，輻照氧化導(dǎo)致靜摩擦系數(shù)增大，動(dòng)摩擦系數(shù)減小。表面氧化產(chǎn)物起三體滾動(dòng)作用，導(dǎo)致動(dòng)摩擦系數(shù)下降。
4.輻照后PEEK的磨損率在1MGy以上時(shí)增加。輻照誘導(dǎo)的表面微缺陷和氧化簇引起的磨粒磨損導(dǎo)致輻照后 PEEK 在高劑量下的耐磨性下降。
Conclusions:
In this work, the changes of surface and internal structure of PEEK irradiated by gamma ray up to 20 MGy dose in the ambient air are studied. The infuence of gamma irradiation-induced surface degradation on tribological property of PEEK is also discussed in detail. The conclusions can be drawn as follows:
1. Irradiation-induced oxidation is the primary form of degradation on the PEEK surface. As the irradiation dose increases, surface oxidation degradation layers appear and the surface morphology defects increase.
2. The mechanical performance test shows that irradiation-induced oxidation results in a decrease in the surface hardness of PEEK.
3. The friction results show that the irradiation-induced oxidation leads to an increase in the static friction coefcient and a decrease in the dynamic friction coefcient. The surface oxidation products play a rolling efect of three-body resulting in the fall of the dynamic friction coefcient.
4. The wear rate of the irradiated PEEK increases when the dose is more than 1 MGy. Irradiation-induced surface microdefects and the abrasive wear caused by oxidized clusters result in the deterioration of wear resistance of the irradiated PEEK at high doses.
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