Al-MWCNT nanocomposite synthesized via spark plasma sintering: effect of powder milling and reinforcement addition on sintering kinetics and mechanical properties

In this work, the effect of mechanical milling of aluminium (Al) powder and subsequent addition of multiwalled carbon nanotubes (MWCNTs) as reinforcement followed by powder mixture consolidation via spark plasma sintering has been investigated. Grain growth during sintering, densification behaviour and mechanical properties (microhardness and compressive properties) were analyzed to complement the study of sintering kinetics. The results showed that for milled Al powder compact, densification started at a lower temperature as compared to the as-received powder compact. This is attributed to large specific surface area of milled Al powders and high amount of diffusivity path created during the milling. The addition of MWCNTs, reinforcement of high hardness and compressive strength, constricted Al particle deformation, sliding and rearrangement during compaction, thereby hindering densification. This behaviour was confirmed by observed increase in Tstart and Tend, the temperature at which densification started and ended, respectively, for nanocomposites containing MWCNTs. Mechanical properties were significantly improved as a result of milling. Microhardness and compressive strength of the milled powder compact increased by 97% and 53%, respectively. MWCNTs pinned grain boundaries and caused dislocation generation and accumulation, which led to further improvement in mechanical properties. However, Al-1.0 wt% CNT showed reduction in microhardness due to inefficient dispersion of MWCNTs leading to large amounts of porosity. Keywords: Al nanocomposite, Multiwalled carbon nanotube, Mechanical milling, Spark plasma sintering, Sintering behaviour, Compression tes

Theories of motivation: A comprehensive analysis of human behavior drivers

This paper explores theories of motivation, including instinct theory, arousal theory, incentive theory, intrinsic theory, extrinsic theory, the ARCS model, self-determination theory, expectancy-value theory, and goal-orientation theory. Each theory is described in detail, along with its key concepts, assumptions, and implications for behavior. Intrinsic theory suggests that individuals are motivated by internal factors like enjoyment and satisfaction, while extrinsic theory suggests that external factors like rewards and social pressure drive behavior. Arousal theory says that to feel motivated, people try to keep an optimal level of activation or excitement. Incentive theory suggests that behavior is driven by the promise of rewards or the threat of punishment. The ARCS model, designed to motivate learners, incorporates elements of attention, relevance, confidence, and satisfaction. Self-determination theory proposes that individuals are motivated by their needs for autonomy, competence, and relatedness. The expectation-value theory suggests that behavior is influenced by individuals' beliefs about their ability to succeed and the value they place on the task. The goal-orientation theory suggests that individuals have different goals for engaging in a behavior. By understanding these different theories of motivation, educators, coaches, managers, and individuals may analyze what drives behavior and how to harness it to achieve their goals. In essence, a nuanced comprehension of these diverse motivation theories equips individuals across varied domains with a strategic toolkit to navigate the complex landscape of human behavior, fostering a more profound understanding of what propels actions and how to channel these insights toward the attainment of overarching goals

An agile system to enhance productivity through a modified value stream mapping approach in industry 4.0: A novel approach

10.3390/su132111997Sustainability (Switzerland)13211199