XRD

Question 0

What is XRD and what is it used for?

Answer 0

The diffraction of short wavelengths, 0.1 nm, used to investigate single crystals and fine grain crystalline powers (Powder XRD).

Question 1

How is XRD used to identify chemical composition of a sample?

Answer 1

A unique diffraction pattern is produced from a specific arrangement of atoms, thus acting as a fingerprint for a particular compound.

Question 2

Powder XRD is a quick analytical method for….

Answer 2

Identifying crystalline compounds.

Question 3

XRD penetrates solid material to provide info about….

Answer 3

The materials atomic structure and chemical composition.

Question 4

X-rays are generated by an electron beam being…

Answer 4

Accelerated towards a metal target.

Question 5

Unlike in SEM, the positive electrode plays a major part. It is usually made from….

Answer 5

Copper or tungsten.

Question 6

The X-rays in the X-ray source consist of a continuous range and wavelengths. This is….

Answer 6

Background radiation.

Question 7

X-rays originate from the collisions between the electrons in the electron beam and the….

Answer 7

Metal atoms In the positive electrode.

Question 8

The interaction between the metal atoms in the positive electrode and the electrons in the electron beam results in deceleration of the electrons and as a result….

Answer 8

X-rays are emitted over a continuous range of wavelengths in all directions.

Question 9

Super imposed on background are intense peaks of X-ray radiation at specific wavelengths. These are dependent on the….

Answer 9

Metal used for the positive electrode.

Question 10

The radiation of X-rays of specific wavelengths generated from falling electrons is used to…

Answer 10

Obtain diffraction patterns from the sample.

Question 11

XRD can be used on paintings to….

Answer 11

Determine chemical composition of inorganic pigments.

Question 12

XRD was used to determine DNA structure by….

Answer 12

Revealing a clear structure of tissue, enabling DNA to recognised as a double helix structure.

Question 13

The generated X-rays pass out of the xray source through a thin window, the window…..

Answer 13

Acts as a filter to remove unwanted radiation.

Question 14

After passing through the window from the source, the x-rays are then further filtered to give a ….l

Answer 14

Single wavelength (monochromatic) using a metal filter.

Question 15

The x-rays are focused using a series of curved mirrors before they hit the….

Answer 15

Sample to be analysed.

Question 16

The output from and XRD is a series of peaks representing…..

Answer 16

Xray intensity as a function of the angle 2sin0

Question 17

Info obtained from Braggs law is converted electronically into a series of peaks which represent….

Answer 17

Xray intensity, angle of incidence and reflection (2sin0)

Question 18

Atoms with more electrons scatter more strongly, resulting in…..

Answer 18

A higher intensity of peaks.

Question 19

Braggs law equation….

Answer 19

d = n(wavelength) / 2 sin (0)

Question 20

Sample prep for powder XRD….

Answer 20

Powder is 10 micrometer in size.
An inorganic solid.
A few 100ml of sample is used.
Surface must be flat to prevent uneven interaction of X-rays.

Question 21

Incident X-rays can interact either by….

Answer 21

Reflection or transmission.

Question 22

After interaction, the X-rays are scattered and measured by a detector. The scattering from atoms arranged in….

Answer 22

Planes ins measured.