Friction and wear of the sliding components in an automobile cause an increase in both fuel consumption and emission.Many engine components involved with sliding contact are all susceptible to scuffing failure at some...Friction and wear of the sliding components in an automobile cause an increase in both fuel consumption and emission.Many engine components involved with sliding contact are all susceptible to scuffing failure at some points during their operating period.Therefore,it is important to evaluate the effects of various surface coatings on the tribological characteristics of the piston ring and cylinder block surface of a diesel engine.Wear and scuffing tests were conducted using a friction and wear measurement of the piston ring and cylinder block in a low friction diesel engine.The frictional forces,wear amounts and cycles to scuffing in the boundary lubricated sliding condition were measured using the reciprocating wear tester.The tester used a piece of the cylinder block as the reciprocating specimen and a segment of the piston ring material as the fixed pin.Several coatings on the ring specimen were used,such as DLC,TiN,Cr-ceramic and TiAlN,in order to improve the tribological characteristics of the ring.The coefficients of friction were monitored during the tests,and the wear volumes of the piston ring surfaces with various coatings were compared.Test results show that the DLC coating exhibits better tribological properties than the other coatings.The graphite structure of this coating is responsible for the low friction and wear of the DLC film.The TiN and DLC coatings show better scuffing resistance than the other coatings.The TiN and Cr-ceramic coated rings show good wear resistance and high friction.展开更多
The Ni-rich Li[Ni0.6Co0.2Mn0.2]O2 surface has been modified with H3PO4. After coating at 80 ℃, the products were heated further at a moderate temperature of 500 ℃ in air, when the added H3PO4 transformed to Li3PO4 a...The Ni-rich Li[Ni0.6Co0.2Mn0.2]O2 surface has been modified with H3PO4. After coating at 80 ℃, the products were heated further at a moderate temperature of 500 ℃ in air, when the added H3PO4 transformed to Li3PO4 after reacting with residual LiOH and Li2CO3 on the surface. A thin and uniform smooth nanolayer （〈 10 nm） was observed on the surface of Li[Ni0.6Co0.2Mn0.2]O2 as confirmed by transmission electron microscopy （TEM）. Time-of-flight secondary ion mass spectroscopic （ToF-SIMS） data exhibit the presence of LIP＋, LiPO-, and Li2PO2＋ fragments, indicating the formation of the Li3PO4 coating layer on the surface of the Li[Ni0.6Co0.2Mn0.2]O2. As a result, the amounts of residual lithium compounds, such as LiOH and Li2CO3, are significantly reduced. As a consequence, the LigPO4-coated Li[Ni0.6Co0.2Mn0.2]O2 exhibits noticeable improvement in capacity retention and rate capability due to the reduction of residual LiOH and Li2CO3. Further investigation of the extensively cycled electrodes by X-ray diffraction （XRD）, TEM, and ToF-SIMS demonstrated that the LiBPO4 coating layers have multi-functions： Absorption of water in the electrolyte that lowers the HF level, HF scavenging, and protection of the active materials from deleterious side reactions with the electrolyte during extensive cycling, enabling high capacity retention over 1,000 cycles.展开更多
文摘Friction and wear of the sliding components in an automobile cause an increase in both fuel consumption and emission.Many engine components involved with sliding contact are all susceptible to scuffing failure at some points during their operating period.Therefore,it is important to evaluate the effects of various surface coatings on the tribological characteristics of the piston ring and cylinder block surface of a diesel engine.Wear and scuffing tests were conducted using a friction and wear measurement of the piston ring and cylinder block in a low friction diesel engine.The frictional forces,wear amounts and cycles to scuffing in the boundary lubricated sliding condition were measured using the reciprocating wear tester.The tester used a piece of the cylinder block as the reciprocating specimen and a segment of the piston ring material as the fixed pin.Several coatings on the ring specimen were used,such as DLC,TiN,Cr-ceramic and TiAlN,in order to improve the tribological characteristics of the ring.The coefficients of friction were monitored during the tests,and the wear volumes of the piston ring surfaces with various coatings were compared.Test results show that the DLC coating exhibits better tribological properties than the other coatings.The graphite structure of this coating is responsible for the low friction and wear of the DLC film.The TiN and DLC coatings show better scuffing resistance than the other coatings.The TiN and Cr-ceramic coated rings show good wear resistance and high friction.
文摘The Ni-rich Li[Ni0.6Co0.2Mn0.2]O2 surface has been modified with H3PO4. After coating at 80 ℃, the products were heated further at a moderate temperature of 500 ℃ in air, when the added H3PO4 transformed to Li3PO4 after reacting with residual LiOH and Li2CO3 on the surface. A thin and uniform smooth nanolayer （〈 10 nm） was observed on the surface of Li[Ni0.6Co0.2Mn0.2]O2 as confirmed by transmission electron microscopy （TEM）. Time-of-flight secondary ion mass spectroscopic （ToF-SIMS） data exhibit the presence of LIP＋, LiPO-, and Li2PO2＋ fragments, indicating the formation of the Li3PO4 coating layer on the surface of the Li[Ni0.6Co0.2Mn0.2]O2. As a result, the amounts of residual lithium compounds, such as LiOH and Li2CO3, are significantly reduced. As a consequence, the LigPO4-coated Li[Ni0.6Co0.2Mn0.2]O2 exhibits noticeable improvement in capacity retention and rate capability due to the reduction of residual LiOH and Li2CO3. Further investigation of the extensively cycled electrodes by X-ray diffraction （XRD）, TEM, and ToF-SIMS demonstrated that the LiBPO4 coating layers have multi-functions： Absorption of water in the electrolyte that lowers the HF level, HF scavenging, and protection of the active materials from deleterious side reactions with the electrolyte during extensive cycling, enabling high capacity retention over 1,000 cycles.
