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The Al2O3/Ti(C,N) ceramic material added micron ZrO2 whisker and nano coated CaF2@Al(OH)3 powder was fabricated. The micron ZrO2 whisker was for the toughening and reinforcing phase and the nano coated CaF2@Al(OH)3 powder was the lubricant. For obtaining a ceramic material with optimal comprehensive mechanical properties and friction properties, the influences of different compositions of the ZrO2 whisker and nano coated CaF2@Al(OH)3 powder on the microstructure and mechanical properties were analyzed, respectively. The result demonstrated that as the addition of the ZrO2 whisker was 6 vol% and the addition of the nano coated CaF2@Al(OH)3 powder was 10 vol%, the optimal self-lubricating ceramic material had optimal mechanical properties. The hardness of the ceramic material was 16.72 GPa, the flexural strength was 520 MPa and the fracture toughness reached 7.16 MPa·m1/2. The formation of the intragranular structure, whisker toughening and the phase transition of ZrO2 were the main mechanisms. [ABSTRACT FROM AUTHOR]

Aiming to improve the performance of self‐lubricating ceramic tools, an advanced self‐lubricating ceramic composite was developed. Core‐shell structure CaF2@Al2O3 powders were synthesized by liquid‐phase non‐uniform nucleation method. Al2O3/Ti(C,N)/CaF2@Al2O3 composite made by adding CaF2@Al2O3 powders exhibited notable improvements in microstructure and mechanical properties as compared with Al2O3/Ti(C,N)/CaF2 composite made by adding uncoated CaF2 powders. The core‐shell coated self‐lubricating ceramic tool with different content of CaF2@Al2O3 was designed and prepared by hot pressing sintering process. The results show that when the content of CaF2@Al2O3 is 10 vol%, The composite has the best mechanical properties, the flexural strength, and the fracture toughness and the hardness is 680 MPa, 6.50 MPa·m1/2, and 17.29 GPa. Compared with the tool material with only CaF2 solid lubricant added, the above performances were increased by 8.91%, 29.48%, and 14.50% respectively. The influence of different CaF2@Al2O3 content on the physical and mechanical properties and microstructure of the tool material was analyzed. [ABSTRACT FROM AUTHOR]

Aiming at the contradiction between the lubricating performance and mechanical performance of self-lubricating ceramic tools. CaF2@Al(OH)3 particles were prepared by the heterogeneous nucleation method. An Al2O3/Ti(C,N) ceramic tool with CaF2@Al2(OH)3 particles and ZrO2 whiskers was prepared by hot press sintering (frittage). The cutting performances and wear mechanisms of this ceramic tool were investigated. Compared with the Al2O3/Ti(C,N) ceramic tool, the Al2O3/Ti(C,N)/ZrO2/CaF2@Al(OH)3 ceramic tool had lower cutting temperatures and surface roughness. When the cutting speed was increased from 100 m/min to 300 m/min, a lot of CaF2 was smeared onto the surface of the ceramic tool, and the flank wear of the Al2O3/Ti(C,N)/ZrO2/CaF2@Al(OH)3 ceramic tool was reduced. The main wear mechanisms of the Al2O3/Ti(C,N)/ZrO2/CaF2@Al(OH)3 ceramic tool were adhesive wear and micro-chipping. The formation of solid lubricating film and the improvement of fracture toughness by adding ZrO2 whiskers and CaF2@Al(OH)3 were important factors for the Al2O3/Ti(C,N)/ZrO2/CaF2@Al(OH)3 ceramic tool to have better cutting performances. [ABSTRACT FROM AUTHOR]

In self-lubricating ceramic tools, adding CaF2 will significantly reduce the mechanical properties of ceramic tools. Based on heterogeneous nucleation theory, we have recently prepared aluminum hydroxide (Al(OH)3) coating on calcium fluoride (CaF2) through a liquid-phase heterogeneous nucleation method. By adding CaF2@Al(OH)3 coated powder to replace CaF2 powder, the self-lubricating ceramic tools maintain higher lubricity while also having better mechanical properties. The coating process was further confirmed by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, we used the molecular simulation software to simulate the suspension system of CaF2, Al(NO3)3·9H2O, and Al(OH)3 to study the process of Al(OH)3 coating on the surface of CaF2 particle to form CaF2@Al(OH)3 powders with core-shell structure. Further, the formation and evolution of Al(OH)3 molecules on the surface of CaF2 were analyzed. [ABSTRACT FROM AUTHOR]

With the rapid development of next-generation sequencing technology, ever-increasing quantities of genomic data pose a tremendous challenge to data processing. Therefore, there is an urgent need for highly scalable and powerful computational systems. Among the state-of–the-art parallel computing platforms, Apache Spark is a fast, general-purpose, in-memory, iterative computing framework for large-scale data processing that ensures high fault tolerance and high scalability by introducing the resilient distributed dataset abstraction. In terms of performance, Spark can be up to 100 times faster in terms of memory access and 10 times faster in terms of disk access than Hadoop. Moreover, it provides advanced application programming interfaces in Java, Scala, Python, and R. It also supports some advanced components, including Spark SQL for structured data processing, MLlib for machine learning, GraphX for computing graphs, and Spark Streaming for stream computing. We surveyed Spark-based applications used in next-generation sequencing and other biological domains, such as epigenetics, phylogeny, and drug discovery. The results of this survey are used to provide a comprehensive guideline allowing bioinformatics researchers to apply Spark in their own fields. [ABSTRACT FROM AUTHOR]

Abstract Due to the poor mechanical properties of solid lubricants, direct addition to the ceramic matrix will reduce the mechanical properties of the material. In this study, Al(OH) 3 was coated on the surface of nano CaF 2 by non-uniform nucleation method and added to Al 2 O 3 /Ti(C,N) ceramic matrix. Al 2 O 3 /Ti(C,N)/CaF 2 @Al 2 O 3 was prepared by vacuum hot pressing sintering. Compared with the material directly added with nano-solid lubricant, the mechanical properties of ceramic tools added with coated nano-solid lubricant have been significantly improved. Among them, when the content of coated nano-solid lubricant is 10 vol%, the ceramic material has better comprehensive mechanical properties. SEM observation shows that the cross-sectional particle distribution of nano-coated powder ceramic material is relatively uniform and has good compactness. The fracture mode of ceramic materials is a mixed fracture mode of intergranular fracture and transgranular fracture. Highlights • Al 2 O 3 was coated on the surface of nano CaF 2 by non-uniform nucleation method. • The mechanical properties of ceramic tools coated with nano-solid lubricants were significantly improved. • The microstructure of ceramic materials with coated nano-powders was studied. [ABSTRACT FROM AUTHOR]