高达50%的PM2.5排放是由于来自汽车行业的颗粒物。废气和非废气排放都会造成城市地区的污染。燃料不完全燃烧,或由于燃烧过程中的高温导致的润滑剂降解,负责废气排放。非排气的涉及刹车,轮胎和路面磨损排放和道路再悬挂的贡献。本研究旨在通过包括光谱工具在内的大量技术,为磨损摩擦产品的详细化学表征提供一种方法学方法。热重分析(TGA),色谱,形态和元素分析。在类似于全球轻型车辆测试程序(WLTP)制动循环的负载下的噪声&振动不平顺性(NVH)测试之后,收集源自制动衬块材料的磨损的灰尘样品。TGA表明,在氧化环境中的测试过程中,只有一小部分燃烧。证明样品主要由金属组成(超过90%)。Fe表现出最高的浓度(50-80%,甚至以氧化物的形式)。还有其他种类的金属,如锌,Al,Mg,Si,S,Sn,Mn,少量出现(每个约1-2%)。该发现通过X射线衍射(XRD)分析得到证实。碎片的有机部分,通过拉曼光谱进行研究,具有明显的芳香特征,可能是由于制动循环试验期间发生的氧化现象。值得注意的是,用有机溶剂提取粉尘样品,首次揭示了超细颗粒(UFP)的存在,即使在几个纳米(纳米颗粒)的范围内,和多环芳烃(PAHs),被认为是剧毒化合物。有毒有机碳和金属的同时存在引起了对非废气排放和强制性的关注,对它们的结构和详细组成有了深刻的了解。
Up to 50 % of total PM2.5 emissions are due to particles derived from the automotive sector, and both exhaust and non-exhaust emissions contribute to the pollution of urban areas. Fuel incomplete combustion, or lubricant degradation due to high temperatures during the combustion process, are responsible for exhaust emissions. The non-exhaust ones concern brakes, tires and road surface-wear emissions and road resuspension contribution. The present study aims to provide a methodological approach for a detailed chemical characterization of wear friction products by means of a large array of techniques including spectroscopic tools, thermogravimetric analysis (TGA), chromatography, morphological and elemental analysis. The dust sample derived from the wear of a brake pad material was collected after a Noise & Vibration Harshness (NVH) test under loads similar to a Worldwide Light vehicle Test Procedure (WLTP) braking cycle. The TGA shows that only a small fraction is burned during the test in an oxidizing environment, testifying that the sample consists mostly of metals (more than 90 %). Fe exhibits the highest concentrations (50-80 %, even in the form of oxides). Also other kinds of metals, such as Zn, Al, Mg, Si, S, Sn, Mn, occur in small quantities (about 1-2% each). This finding is confirmed by X-ray diffraction (XRD) analysis. The organic fraction of the debris, investigated by means of Raman spectroscopy, has an evident aromatic character, probably due to oxidative phenomena occurring during the braking cycle test. Noteworthy, the extraction of the dust sample with organic solvents, revealed for the first time the presence of ultrafine particles (UFPs), even in the range of few nanometers (nanoparticles), and polycyclic aromatic hydrocarbons (PAHs), recognized as highly toxic compounds. The simultaneous presence of toxic organic carbon and metals makes of concern the non-exhaust emissions and mandatory a deep insight on their structure and detailed composition.