Browsing by Author "Aikebaier, Aizimaiti"

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Open Access
Application of triboelectric charging effect for engine lubricating oil degradation monitoring
(2019-01) Aikebaier, Aizimaiti
Lubrication of machine parts is necessary to prevent friction and wear in machine operation. Even the slightest reduction of friction and wear cause a huge positive impact in the economy since almost all machines in our current industry suffer from the energy and material losses caused by these events. Therefore, maintaining good and stabilized lubrication is vital for this purpose. However, oxidation of lubricants upon operation brings about unwanted changes in its chemical and physical properties and causes lubrication performance to deteriorate. Thus, a better understanding of lubricant condition and its variation under different parameters can enable technologists to make informed decisions to ensure lubrication excellence and optimization of the lubricant's renewal time. However, current methods for detection of oil deterioration lack practicality and exibility. In this study, a novel method was put forward to estimate the remaining service life of several types of commercially available engine lubricants using triboelectri fication. A Triboelectric sensor (TES) was developed and this TES was given different open circuit voltage (Voc) values according to the different oxidation time of lubricant oils. These results were then correlated with FTIR-ATR analyses of the oils. Additionally, we reported the dynamic viscosity changes of engine oil samples upon oxidation. We believe the results presented in this thesis convey the basis for establishing a TES for straightforward detection of deterioration of engine oil.
Open Access
Thermal conductivity measurements in nanosheets via bolometric effect
(IOP Publishing Ltd, 2020) Çakıroğlu, Onur; Mehmood, Naveed; Çiçek, Mert Miraç; Rasouli, Hamid Reza; Durgun, Engin; Kasırga, T. Serkan; Aikebaier, Aizimaiti
Thermal conductivity measurement techniques for materials with nanoscale dimensions require fabrication of very complicated devices or their applicability is limited to a class of materials. Discovery of new methods with high thermal sensitivity are required for the widespread use of thermal conductivity measurements in characterizing materials' properties. We propose and demonstrate a simple non-destructive method with superior thermal sensitivity to measure the in-plane thermal conductivity of nanosheets and nanowires using the bolometric effect. The method utilizes laser beam heating to create a temperature gradient, as small as a fraction of a Kelvin, over the suspended section of the nanomaterial with electrical contacts. Local temperature rise due to the laser irradiation alters the electrical resistance of the device, which can be measured precisely. This resistance change is then used to extract the temperature profile along the nanomaterial using thermal conductivity as a fitting parameter. We measured the thermal conductivity of V2O3 nanosheets to validate the applicability of the method and found an excellent agreement with the literature. Further, we measured the thermal conductivity of metallic 2H-TaS2 for the first time and performed ab initio calculations to support our measurements. Finally, we discussed the applicability of the method on semiconducting nanosheets and performed measurements on WS2 and MoS2 thin flakes.
Open Access
Why does wood not get contact charged? Lignin as an antistatic additive for common polymers
(American Chemical Society, 2020) Özel, Mertcan; Demir, Fatma; Aikebaier, Aizimaiti; Kwiczak-Yiğitbaşı, Joanna; Baytekin, H. Tarık; Baytekin, Bilge
Contact electrification (CE), or the development of surface charges upon contact and separation, is a millennia-old scientific mystery and the source of many problems in the industry. Since the 18th century, efforts to understand CE have involved ranking materials according to their charging propensities. In all these reports, wood, an insulator, turns out to be surprisingly immune to CE. Here, we show that this unique antistatic nature of wood is attributable to its lignin content, i.e., lignin removal from wood ceases the antistatic property, and (re)addition brings it back. The antistatic action of lignin (also an insulator) is proposed to be related to its radical scavenging action and can be explained through the bond-breaking mechanism of CE. Our results also show that lignin, a sustainable, low-cost biopolymer, can be used as an antistatic additive in some representative examples of elastomers and thermoplastics, displaying the universal nature of its antistatic action.