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  • What is X-ray diffraction, and what is it used for?

    什麽是X光繞射(XRD)?它能夠做什麽?在 X 光繞射實驗中,

  • In an X-ray diffraction experiment, a sample is placed into the center of an instrument and illuminated with a beam of X-rays.

    樣品放置在儀器的中心,受到一束 X 光照射。

  • The X-ray tube and detector move in a synchronized motion.

    X 光光管和探測器同步的移動,

  • The signal coming from the sample is recorded and graphed,

    記錄了從樣品散射出來的訊號並做成圖譜。

  • where peaks are observed related to the atomic structure of the sample.

    圖譜中的繞射峰提供了樣品原子結構的訊息。

  • Most materials are made up of many small crystals like sand on a beach.

    大多數的材料都是由許多小晶體組成的, 這就像沙灘上的沙一樣。

  • Each of these crystals is composed of a regular arrangement of atoms,

    這些小晶體裏面都有許多整齊排列的原子,

  • and each atom is composed of a nucleus surrounded by a cloud of electrons.

    而每個原子裏面包含了一個原子核和圍繞在周圍的電子雲,

  • It's at this scale that the story of X-ray diffraction begins.

    X 光繞射就是在這個原子尺度下發生的。

  • X-rays are high-energy light with a repeating period called the wavelength.

    X 光是一種周期性高能光束線,它的周期稱爲波長。

  • Since the wavelength of an X-ray is similar to the distance between atoms in a crystal,

    由於 X 光的波長與晶體中的原子間距接近,

  • a special interference effect called "diffraction" can be used to measure the distance between the atoms.

    形成了一種可以利用來量測原子間距的特殊干涉現象, 稱爲繞射。

  • Interference occurs when X-rays interact with each other.

    當X射線相遇發生交互作用時,就會產生干涉現象。

  • If the waves are in alignment, the signal is amplified. This is called "constructive interference".

    如果相位相同,訊號會被加强,稱爲建設性干涉。

  • If the waves are out of alignment, the signal is destroyed. This is called "destructive interference".

    相反的,如果相位相反,則會消弱,稱爲破壞性干涉。

  • When an X-ray encounters an atom, its energy is absorbed by the electrons.

    當X光擊中電子時,它的能量會被電子吸收。

  • Electrons occupy special energy states around an atom. Since this is not enough energy for the electron to be released,

    電子在原子的周圍占據了特定能態的軌道。由於能量不足以讓電子脫離,

  • the energy must be re-emitted in the form of a new X-ray, but the same energy as the original.

    這些能量會以二次 X 光的形式釋放,能量大小與原始 X 光相同。

  • This process is called "elastic scattering".

    這個過程稱爲彈性散射。

  • In a crystal, the repeating arrangement of atoms form distinct planes separated by well-defined distances.

    在晶體中,周期性排列的原子形成了等間距的晶面。

  • When the atomic planes are exposed to an X-ray beam, X-rays are scattered by the regularly spaced atoms.

    當 X 光照射到晶面,就會被規則排列的原子散射。

  • Strong amplification of the emitted signal occurs at very specific angles

    散射 X 光會在特定的角度產生非常强烈的建設性干涉訊號。

  • where the scattered waves constructively interfere. This effect is called "diffraction".

    這個效應,就稱爲繞射現象。

  • The angle between the incident and the scattered beam is called 2-theta.

    入射光和散射光之間的夾角稱爲 2theta 角。

  • In order for constructive interference to occur, the scattered waves must be in alignment,

    要形成建設性干涉,散射光必須與入射光同相。

  • meaning that the second wave must travel a whole number of wavelengths.

    也就是説第二條光線必須比第一條光線多走一個波長的距離。

  • In this case, one half of a wavelength is traveled on the incident side,

    這時,半個波長會在入射側,而另外半個波長會在散射側,這樣可以凑成額外一個波長。

  • and one half on the scattered side, yielding one additional wavelength.

    到了下一條光線,入射側和散射側各多一個波長,

  • In the case of the next X-ray, one wavelength has traveled on

    這樣就有兩個波長的光程差。 這樣的叠加現象會在整個晶體裏出現,

  • both the incident and the scattered side resulting in two wavelengths.

    繞射現象發生的角度位置是由紅色的三角形決定。

  • This reinforcement occurs throughout the crystal.

    三角形上方的角度稱爲 theta 角, 是入射光跟散射光之間夾角的一半。

  • The exact angle at which diffraction occurs will be determined from the red triangle.

    三角形的長邊是晶面間距,而短邊就是半波長的距離。

  • The angle at the top is theta, half the angle between the incident and scattered beams.

    繞射角的晶面間距正好形成正弦函數的關係。

  • The long side is the distance between the atomic planes and the short side we know is one half of a wavelength.

    如果我們把等式移項就能得到布拉格定律(Bragg's Law)。

  • The relationship between the diffraction angle,

    這個定律是以 Sir William Henry Bragg 和 William Lawrence Bragg 這對父子檔命名的。

  • and the spacing between the atoms can be determined by applying the sine function.

    他們在 1915 年因爲X光繞射在晶體結構分析的成就, 得到諾貝爾獎。

  • Rearranging this equation yields an equation commonly known as "Bragg's Law",

    如今,X光繞射分析技術被廣汎的應用在各種材料,

  • named after Sir William Henry and William Lawrence Bragg, the father-son team who won the Nobel Prize in 1915

    包括單晶磊晶薄膜、多晶粉末混合物,

  • for their work analyzing crystal structures with X-ray diffraction.

    甚至是無序的非晶質材料。

  • This technique of X-ray diffraction is used today for a wide variety of materials, ranging from

    X光繞射幫助科學家研發新藥品,

  • single crystal epitaxial thin films, to polycrystalline mixtures of powders, and even randomly oriented amorphous materials.

    根據礦物組成鑒定岩石種類,

  • X-ray diffraction helps scientists to develop new pharmaceuticals, classify rock formations

    瞭解原子排列對儲能材料的影響。

  • based on their mineral components and understand how the arrangement of atoms

    當科學家把材料工程推向原子層次時,X光繞射分析也成爲越來越重要的工具。

  • affects the behavior of energy storage materials.

    先進的儀器設計讓X光繞射分析更易於使用, 功能也越來越强大。

  • As scientists push their ability to engineer materials on the atomic level,

  • X-ray diffraction becomes an increasingly important tool in their toolbox.

  • Advances in equipment design have made X-ray diffraction easier to use, and more powerful than ever.

What is X-ray diffraction, and what is it used for?

什麽是X光繞射(XRD)?它能夠做什麽?在 X 光繞射實驗中,

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什麽是X光繞射(What is X-ray Diffraction?)

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    lovegastar 發佈於 2022 年 08 月 04 日
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