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相关概念视频

Network Covalent Solids02:18

Network Covalent Solids

Network covalent solids contain a three-dimensional network of covalently bonded atoms as found in the crystal structures of nonmetals like diamond, graphite, silicon, and some covalent compounds, such as silicon dioxide (sand) and silicon carbide (carborundum, the abrasive on sandpaper). Many minerals have networks of covalent bonds.
To break or to melt a covalent network solid, covalent bonds must be broken. Because covalent bonds are relatively strong, covalent network solids are typically...
Ferromagnetism01:31

Ferromagnetism

Materials like iron, nickel, and cobalt consist of magnetic domains, within which the magnetic dipoles are arranged parallel to each other. The magnetic dipoles are rigidly aligned in the same direction within a domain by quantum mechanical coupling among the atoms. This coupling is so strong that even thermal agitation at room temperature cannot break it. The result is that each domain has a net dipole moment. However, some materials have weaker coupling, and are ferromagnetic at lower...
Work01:14

Work

Work is a fundamental concept of mechanical engineering and has many applications. Understanding how work is calculated and the different types of work can help us better understand physical processes and provide insights into complex problems.
Work is defined as the result of a force acting on an object, causing it to move along the line of action of force. It is also defined as the process of transferring energy through the application of force on an object, resulting in its displacement.
Softwoods and Hardwoods01:28

Softwoods and Hardwoods

Softwoods and hardwoods, derived from different types of trees, are distinguished by their leaf structures and cellular compositions, each serving unique purposes in construction and manufacturing. Softwoods come from cone-bearing trees with needle-like leaves and are predominantly composed of longitudinal cells called tracheids and a smaller proportion of radial cells known as rays. Due to their cellular structure, softwoods are commonly used in construction for structural frames, sheathing,...
Toughness and Hardness of Aggregate01:22

Toughness and Hardness of Aggregate

Toughness and hardness are critical properties of aggregate materials used in concrete, particularly on pavement surfaces and industrial flooring subjected to heavy loads. Toughness is defined as the aggregate's resistance to failure by impact and is measured by the aggregate impact value (AIV). For this, the aggregate impact value test is performed, wherein the impact is delivered by a standard hammer, which falls freely under its own weight onto the aggregates. The aggregates fragment in the...
Mechanical Characteristics of Steel01:18

Mechanical Characteristics of Steel

The mechanical characteristics of steel are assessed through various tests that evaluate its strength, toughness, and flexibility. These tests include tension, torsion, impact, bending, and hardness assessments, each providing crucial information about steel's suitability for specific applications.
The tension test is fundamental for determining tensile strength. In this test, a steel specimen is stretched using a gripping device until it breaks. The data collected during this test are used to...

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相关实验视频

Updated: Jul 7, 2026

Quantitative Hardness Measurement by Instrumented AFM-indentation
08:21

Quantitative Hardness Measurement by Instrumented AFM-indentation

Published on: November 22, 2016

为什么是硬的

J J Gilman

    Science (New York, N.Y.)
    |September 10, 1993
    PubMed
    概括
    此摘要是机器生成的。

    像这样的共价固体由于有限的位移运动而易碎. 这种脆性是由类似于化学替代的原子过程解释的,揭示了为什么这些材料抵抗变形.

    科学领域:

    • 材料科学 材料科学 材料科学
    • 固态物理 固态物理
    • 化学物理 化学物理

    背景情况:

    • 协价固体,如,表现出硬度和脆性,与金属和离子盐不同.
    • 在共价固体中,脱位运动受到限制,只发生在高温下.
    • 这种现象的明确解释一直是难以捉摸的,尽管它在材料力学中的重要性.

    研究的目的:

    • 为共价固体的脆性提供令人满意的解释.
    • 阐明控制这些材料中脱位运动的原子层次机制.
    • 将共价固体的机械特性与它们的结合特性联系起来.

    主要方法:

    • 异位运动和化学替代反应之间的类比.
    • 使用相关性图表进行原子过程分析.
    • 研究原子结合对称性在材料变形中的作用.

    主要成果:

    • 脆弱性的关键原子过程类似于化学替代反应.
    • 分析显示出高电阻应力和高激活能量用于位运动.
    • 脱位扭曲运动破坏了原子结合对称性,这一过程在能量上是不利的.

    结论:

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    相关实验视频

    Last Updated: Jul 7, 2026

    Quantitative Hardness Measurement by Instrumented AFM-indentation
    08:21

    Quantitative Hardness Measurement by Instrumented AFM-indentation

    Published on: November 22, 2016

    Determining the Mechanical Strength of Ultra-Fine-Grained Metals
    05:04

    Determining the Mechanical Strength of Ultra-Fine-Grained Metals

    Published on: November 22, 2021

    Microhardness Measurements on Tooth and Alveolar Bone in Rodent Oral Disease Models
    06:16

    Microhardness Measurements on Tooth and Alveolar Bone in Rodent Oral Disease Models

    Published on: April 26, 2024

    • 观察到的共价固体的脆性基本上与一种类似于原子替代的过程有关.
    • 高电阻应力和激活能量是这个过程的直接后果.
    • 在脱位运动过程中,原子结合对称的破坏解释了材料对变形的抵抗.