Tribology of Slip Surfaces in Journal Bearings

Boundary slip can be triggered by certain engineered surfaces. Journal bearings with slip surfaces have markedly different performances compared with traditional journal bearings. In order to reasonably utilise boundary slip to improve the tribological performances of journal bearings, including hydrodynamic and hybrid journal bearings, it is necessary to draw out the impact laws of boundary slip on the performances of journal bearings. The design criterion of slip surfaces is presented in this chapter; only a well-designed slip surface could improve the tribological performances of journal bearings. This chapter could provide a valuable guide for the design of slip surfaces in journal bearings

Low-Temperature Synthesis of Superconducting Nanocrystalline MgB

Magnesium diboride (MgB2) is considered a promising material for practical application in superconducting devices, with a transition temperature near 40 K. In the present paper, nanocrystalline MgB2 with an average particle size of approximately 70 nm is synthesized by reacting LiBH4 with MgH2 at temperatures as low as 450°C. This synthesis approach successfully bypasses the usage of either elemental boron or toxic diborane gas. The superconductivity of the nanostructures is confirmed by magnetization measurements, showing a superconducting critical temperature of 38.7 K

Control of Domain Structures in Multiferroic Thin Films through Defect Engineering

Domain walls (DWs) have become an essential component in nanodevices based on ferroic thin films. The domain configuration and DW stability, however, are strongly dependent on the boundary conditions of thin films, which make it difficult to create complex ordered patterns of DWs. Here, it is shown that novel domain structures, that are otherwise unfavorable under the natural boundary conditions, can be realized by utilizing engineered nanosized structural defects as building blocks for reconfiguring DW patterns. It is directly observed that an array of charged defects, which are located within a monolayer thickness, can be intentionally introduced by slightly changing substrate temperature during the growth of multiferroic BiFeO3 thin films. These defects are strongly coupled to the domain structures in the pretemperatureâ change portion of the BiFeO3 film and can effectively change the configuration of newly grown domains due to the interaction between the polarization and the defects. Thus, two types of domain patterns are integrated into a single film without breaking the DW periodicity. The potential use of these defects for building complex patterns of conductive DWs is also demonstrated.Engineered structural defects are used as nanosized building blocks for configuring domainâ wall patterns in multiferroic BiFeO3 thin films. By utilizing the interaction between the polarization and the defects, two types of twinning domain structures are integrated into a single film without breaking the domainâ wall periodicity.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146435/1/adma201802737-sup-0001-S1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146435/2/adma201802737_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146435/3/adma201802737.pd

Size-Dependent Structural Distortions in One-Dimensional Nanostructures

No abstract.Keywords: Composites, Inorganic synthesis, Chalcogenides, Binary nanoparticle superlattices, Stability, Misfit layer compounds, Nanomaterials, Nonodisperse nanocrystals, Nanocrystal superlattices, Gold, Organization, Shape, Hybrid material

Comparison of the Influences of Surface Texture and Boundary Slip on Tribological Performances

Close attentions have been widely paid to the engineering textured and slip surfaces for improving bearing tribological performances. Comparison studies on the tribological characteristics of slip and textured surfaces are carried out in this work. The analysis results point out that the influences of surface texture and boundary slip on tribological performances of slider bearing are strongly similar. For the determinate surface textures, there is one and only value of slip velocity to make the tribological performances of textured and slip surfaces in agreement. The corresponding relation between the slip velocity and the texture structure parameters is also obtained, and the size of slip velocity is directly related to the texture geometry parameters including its position parameters. This study will help us to further understand the relationship between boundary slip and surface texture and also the slip phenomenon

Experimental investigation and seasonal performance assessment of a frost-free ASHP system with radiant floor heating

Air source heat pumps (ASHPs) have been increasingly used to promote energy savings and reduce environmental pollution. However, the evaporator frosting is one of the largest problems in ASHP systems during the heating operation. To examine this issue, a novel frost-free ASHP system has been developed. Nonetheless, the system performance and energy consumption are significantly dependent on the climate conditions. This research aims to identify the characteristics of the novel frost-free ASHP system with radiant floor heating in three different climate zones, China. TRNSYS 17.0 software was employed to investigate the seasonal performance of the new system based on the typical envelope thermal characteristic parameters in the entire heating period in three cities, i.e. Beijing (cold A zone), Xi\u27an (cold B zone), and Chengdu (hot summer and cold winter zone), located in different climate zones, China. The results showed that the heating seasonal performance factors (HSPFs) of the studied system were 3.9%, 1.9% and 9% higher than the conventional system in Xi\u27an, Beijing and Chengdu, respectively. It was concluded that the system could operate effectively and reduce substantial energy consumption in comparison with the conventional ASHP system for space heating in cold climate zones