Oleh :

Sri Mulyati (1021207007)Ayu Azhari (1021207008)

Emelia Karnila (1021207013)Citra Buhatika (1021207015)

Dosen Pembimbing : Prof. Dr. Novesar Jamarun

PERSIAPAN SAMPEL XRD

Sample preparation methodsmust

Simple

Low cost

Rapid

Reproducible

An ideal sample would be:- Representative of the material- Homogenous- Of infinite thickness- Without surface irregularities- With small enough particles for the

wavelengths being measured

Quality of Sample Preparation

SAMPLES

METAL POWDER LIQUID

XRF onlyXRD and XRF

XRD Working Concept

When a monochromatic x-ray beam with wavelength is incident on the lattice planes in a crystal planes in a crystal at an angle , diffraction occurs only when the distance traveled by the rays reflected from successive planes differs by a complete number n of wavelengths. By varying the angle , the Bragg’s Law conditions are satisfied by different d-spacing in polycrystalline materials. Plotting the angular positions and intensities of the resultant diffraction peaks produces a pattern which is characterised of the sample. Where a mixture of different phases is present, the diffractogram is formed by addition of the individual patterns.

XRF Working Concept

In X-ray fluorescence spectroscopy, the process begins by exposing the sample to a source of x-rays. As these high energy photons strike the sample, they tend to knock electrons out of their orbits around the nuclei of the atoms that make up the sample. When this occurs, an electron from an outer orbit, or “shell”, of the atom will fall into the shell of the missing electron. Since outer shell electrons are more energetic than inner shell electrons, the relocated electron has an excess of energy that is expended as an x-ray fluorescence photon.  This fluorescence is unique to the composition of the sample. The detector collects this spectrum and converts them to electrical impulses that are proportional to the energies of the various x-rays in the sample’s spectrum.

X-RAY ANALYSIS

METAL

CHIPS

REMELT

CAST

POLISHING

BELT GRINDER/LATHE

INGOT

SOLUTION

LIQUID

POWDER

GRINDING FUSION SOLUTION

PELLET

GLASS BEAD LIQUID

X-RAY ANALYSIS

PRESS

SolidsPressed powders

Fused beadsLiquids

Sample types

- metal alloys, plastics & glass- relatively easy to prepare by cutting,

machining, milling % fine polishing- Avoid smearing of soft metals (e.g. Pb) - Polishing may introduce contamination

from the polishing material- do not have particle size problems- Surface needs to be flat- Surface needs to be homogeneous- Surface defects are more critical for light

elements if good accuracy is required.

Solid

- Typical samples types that are prepared as pressed powders include rocks, soil, slag, cements, alumina, fly ash, etc.

- Particle size of powder needs to be controlled for light element analysis

- If necessary, powders are ground to achieve a particle size of < 50 µm

- Grinding can be introduce contamination (e.g. Fe from a chrome steel mill)

- Binding agents (e.g. wax or cellulose) can be used to increase sample strength to avoid breakage in the spectrometer

- Ground powders are pressed into a solid tablet under pressure using a hydraulic press & 40 mm die

- Relatively slow method (≈5 minutes per sample) but relatively low cost

- Pressed powders suffer from particle size problems for light elements

Pressed powders

- Typical samples that are prepared as fused beads include rocks, cements, iron ores, etc. when higher accuracy is required.

- Weighed sample is mixed with flux- Sample and flux are melted at ≈ 1000 oC- Melt is poured into a 40 mm mold- Bead surface needs to be homogenous (constant color

without cracks)- Slow (10-15 minutes/sample)- High cost- Important benefit is that particle size problems

disappear (fusion process results in a homogeneous glass)

- An additional benefit is that the melting flux (usually Na or Li borate) dilutes the sample, reducing matrix variations, resulting in higher accuracy

- Disadvantage –reduced sensitivity for trace elements

Fused beads

- Typical samples include environmental (waters, mud) & oils

- Easiest to prepare- Should have a constant volume that exceeds

maximum penetration depth- Sample is poured into a liquid cell fitted with a

thin plastic window - Range of window materials to suit different

liquids- Fill to a constant height (e.g. 20 mm) to avoid

errors from variable depth- Choose the correct thickness and material to suit

the chemistry of the sample being measured- Na is lightest element that can be detected in

liquids.

Liquid

Hal-hal yang harus diperhatikan dalam Persiapan Sampel XRD

Kualitas data yang didapat tidak akan lebih baik dibanding kualitas sampel dan kualitas persiapan dan pengendapan.

Keberhasilan analisis struktural difraksi dari powder tergantung pada keaslian sampel dan kondisi eksperimental.

Langkah-langkah yang harus diperhatikan

Waktu penggilingan: beberapa detik hingga menit.

Caution!Memperpanjang waktu penggilingan akan menghasilkan luas permukaan spesifik ( dengan rekonstruksi atau tranformasi permukaan), penggabungan partikel, kehilangan kekristalan atau bahkan reaksi kimia (transisi fasa, desolvasi, polimerisasi).

Other Tricks Untuk membuat material plastik yang rapuh, bisa

dilakukan penggilingan dalam lingkungan larutan nitrogen.

Pengulangan pemanasan sampel (10-30 min) pada 1/3 m.p sampel untuk menghindari kecacatan.

Penggunaan cairan kimia inert untuk menghindari cluster dari partikel lunak.

Pengayakan antara 25-75 µm, juga dibawah tekanan atau di dalam flux dari cairan inert.

CAUTION! Hindari kontaminasi oleh alu atau penggiling. Masalah oleh material lentur.

Deposisi Sampel – Plat Datar (Bragg-Bentano)

Plastik, aluminium atau glass sample holder: sampel kering dalam ruang berongga.

Metoda Lain untuk Deposisi Sampel(Bragg-Bentano)

Pengabuan kering Pengabuan dalam minyak, pelumas, silikon, dll. Back filling or side loading Pencampuran dengan inert powder (gandum, cabosil). Volatile inert liquids (acetone, ethanol, etc). Non volatile suspending inert liquids (amyl acetate, +5%

collodion). Non volatile suspending inert liquids (amyl acetate, +5%

collodion). Spray drying (with “spherical particles) Thin film (for transparent materials and indexing procedures

…).

NOTE!Often it is better to use a zero background plate as

sample holder (Si or SiO2 monocrystal).

Bragg Bentano…

Other methodes for sample deposition (Transmission)

• Dusting on transparent films, with or without, lacquers or inert liquids.

• Dusting on metals (C,Ni) grids

Other methodes for sample deposition (Debye-Scherrer)

• Kapiler direndam dalam cairan “ligan” (minyak atau parafin) dan dalam powder terdispersi. Pencampuran cairan dan powder juga dapat membantu pengendapan.

• Kapiler diisi oleh gravity dengan powder kering dan wadah ultrasonik.

• Kapiler secara eksternal ditutupi dengan powder yang lengket.

• Kapiler ditutup denga gas inert atau cairan induk untuk sampel yang tidak stabil.

Sample preparation for powder diffraction

1. Coarse grinding. Use the "Little Smasher" to reduce the size of larger chips to approximately sand-size (less than 1 or 2 mm).

2. Transfer no more than about 2 g of the coarse grind to the steel container for grinding in the Spex Mixer. The container should be no more than 20% full.

3. Add a steel ball to the container and put on the lid.

4. Mount the grinding container into the mixer, fasten snugly, close the lid and turn on the mixer for at least 5 minutes. Hard samples may require a longer grinding time.

5. After grinding is complete, transfer the powder to a piece of weighing paper and sieve it through the 270 mesh sieve.

6. Be sure to clean the grinding ves7. If insufficient sample was reduced to < 270 mesh,

return the oversize fraction to the grinder for another run.

8. Mount the powder in the sample holder according to the procedure in the manual in the drawer beneath the sample preparation materials.

9. Clean the mounting materials and put them away.10.Please clean the tables, take your samples and your

stuff.

Sample preparation for retained austenite analysis

1. Cutting the sample with a water cooled abrasive disk. Cutting process must not damage or change the sample as this would lead to erroneous results.

2. Sample mounting with cold or hot mounting method.

3. Grinding samples on SiC papers with grit size of 180, 240, 320, 400 and 600.

4. Mechanical polishing with 3 um diamond paste.

5. 3 min electropolishing to remove interfering oxides and eliminate any plastically deformed surface layer.

6. Specimens must be cleaned after each step, all grains from one grinding and polishing step must be completely removed from the specimen to avoid contamination, which would reduce the efficiency of the next preparation step.

Preparation of small amounts of the powders

1. Small amounts of the fine powder sample are pressed into the indentation of an acrylic glass sample holder.

2. Very small sample amounts (micro gram or less) of powdered specimen are loaded into thin walled glass capillaries. Use Mark tubes of 1.0 or 0.3 mm diameter and 0.01 mm wallthickness.

3. To reduce the background scattering from the glass wall, powdered samples are also dusted on thin foils and fixed by a light touch of hair spray.

4. Individual, tiny particles are placed under microscopic control with the help of a very fine needle on a strip of 3 µm Mylar, which has been previously coated with a fine trace of hair spray.

5. Side-Drifted (plastic) These Plexiglas mounts have a 1 x 2 cm specimen well 1 mm deep machined from one edge of the mount.

Grain size and surface roughness

Uniformity of sample

Contamination through the sample preparation

Factor of errors in Sample Preparation

Grain size and surface roughness

Uniformity of sample

Casting condition of the sample in the molding.

Sand molding

Metal molding

X-ray intensities differ according to the molding method which comesIn the measurement of light elements.

Quenching casting which makes the metallic composition fine produces good results

Sample polishing

NiK intensity CrK intensity

50# emery paper 0.686 0.974

100# emery paper 0.699 0.983

240# emery paper 0.704 0.989

Mirror polishing 0.709 0.993

Uniformity of sample

Contamination during polishing

Contamination effect when carbon steel and Ni-Cr alloy polish after polishing stainless steel.

As the contamination form the polishing belt to the sample, the re contamination From The material of the polishing belt and from the remaining trace elements of polished Sample.

Ni Cr Fe

% Conc 0.55 0.21 2.10

% Contamination 0.05 0.03 0.38

Powder Sample

Different grinding condition cause variation in particle size distribution which leads to variation in X-Ray intensity.