This lecture contains four sections as reading information.

Transcription

1 Sample Preparation: The Backloading Technique This lecture contains four sections as reading information. Basic XRD Course 1

2 Sample Preparation: The Backloading Technique Basic XRD Course 2

3 Sample Preparation: The Backloading Technique This presentation gives a description of the preparation of powder samples in PW1811 sample holders according to the backloading technique. The preparation of samples for analysis is of critical importance if accurate and fast results are to be obtained, and the procedures detailed in this section should be careful followed. Additionally, the introduction of errors such as contamination, material loss, alteration of composition, especially of the sample surface, and change of lattice type during the course of sample preparation and afterwards, should be avoided. Contamination of the sample can be caused by dust, by material from a previous sample that remained in the sample preparation equipment, or by material from the sample preparation equipment resulting from abrasion. Material loss is attributed to non-quantitative transfer in concentration determining operations (dilution, binder addition), loss of a small fraction of particle size as dust, and material remaining in the sample preparation equipment. Alteration of composition is attributed to losses of material particles, which are of different composition to the average composition. For example magnetic particles, fine dust, and volatile substances. Also, alteration of composition is attributed to physical or chemical alteration. That is, by decomposition during preparation such as oxidation, loss of combined water or carbon dioxide by overheating and pick-up of water or carbon dioxide from the air, or by the addition of materials of different composition such as by contamination. Basic XRD Course 3

4 Sample Preparation: The Backloading Technique The PW1770/10 powder sample preparation kit is designed for powder samples of the PW18xx sample holder series. It consists of a sample preparation table, on which the sample holder ring (PW1811/16 or PW1811) is clamped, a powder press block, a dusting brush and a Stanley knife blade. Basic XRD Course 4

5 Sample Preparation: The Backloading Technique To prepare a powder sample in a PW1811 sample holder, proceed as follows: 1. Clamp the sample holder ring (PW1811/16 or PW1811/27) securely to the preparation table. Basic XRD Course 5

6 Sample Preparation: The Backloading Technique 2. Spread the powder in the holder ring so that the powder is heaped up into a conical shape inside the holder ring. Basic XRD Course 6

7 Sample Preparation: The Backloading Technique 3. Press the powder down firmly into the holder ring using the powder press block. Ensure that a firm and even pressure is applied by hand to the press block. Basic XRD Course 7

8 Sample Preparation: The Backloading Technique 4. During pressing, some powder flows out of the holder ring. Use a knife blade to scrape the powder back into the holder ring and press down again using the powder press block. Basic XRD Course 8

9 Sample Preparation: The Backloading Technique 5. Remove all surplus powder above the rim of the holder using the knife blade. Basic XRD Course 9

10 Sample Preparation: The Backloading Technique 6. Clean off all remaining surplus powder from the holder using the dusting brush. Basic XRD Course 10

11 Sample Preparation: The Backloading Technique 7. Place the bottom plate (PW1811/00) onto the holder ring and clamp it into position. Basic XRD Course 11

12 Sample Preparation: The Backloading Technique 8. Remove the complete sample holder from the preparation table by turning the sample preparation table upside down and pressing the spring-loaded knob. The sample must show a smooth and flat sample surface, flush with the sample holder ring surface. Note: When the sample holders are used in X Pert PRO systems, the reference plane of the holder must always be kept clean. Any spilled powder must be removed before loading the sample. The reference plane is the outer rim of the holder, where it is in contact with the three ball bearings in the ball bearings in the measuring position. The sample is now ready for use. Basic XRD Course 12

13 Sample Preparation: The Backloading Technique Glass capillaries can be attached with a little bit of modeling wax at the tips onto a silicon wafer (PW1817/32), which gives a very low background intensity. The silicon wafer can then be mounted in the PW1813/32 sample holder. This method is an alternative to using the capillary spinner in the transmission geometry. Basic XRD Course 13

14 Sample Preparation: The Backloading Technique Small amounts of powder can also be attached to a silicon wafer with a drop of alcohol or a smear of petroleum jelly (Vaseline). Note: Silicon supports must be cleaned carefully before use, preferably using an ultrasonic bath. Basic XRD Course 14

15 Sample Preparation: Samples for Transmission Geometry This presentation describes the preparation of powder samples that will be measured using transmission geometry. Basic XRD Course 15

16 Sample Preparation: Samples for Transmission Geometry Powder or paste-like samples can be placed between two Kapton foils, which are then clamped in the sample holder. Capillaries are used when the samples to investigate are sensitive to oxygen or humidity, or are dangerous to the operator s health. Samples are also prepared in glass capillaries when the conventional powder sample preparation methods give rise to the presence of preferred orientation (texture). During preparation, the same precautions should be considered as described for the preparation of circular samples. Basic XRD Course 16

17 Sample Preparation: Samples for Transmission Geometry When the sample material is prepared, ensure that you have the complete set of the PW1818/xx sample holders and rings and two Kapton foils. Basic XRD Course 17

18 Sample Preparation: Samples for Transmission Geometry Place one Kapton foil over the insert and clamp it with the smaller white ring. Now you can spread a small amount of sample material, for instance a powder or a paste-like substance, onto the Kapton foil. Basic XRD Course 18

19 Sample Preparation: Samples for Transmission Geometry Cover the sample with the second Kapton foil and clamp it onto the insert using the larger white ring. Use a pair of scissors to trim the foil to the size of the outside of the insert ring. Basic XRD Course 19

20 Sample Preparation: Samples for Transmission Geometry Now you can bring the insert into its position in the PW1818/40 sample holder ring and fix it using the circular steel spring. Basic XRD Course 20

21 Sample Preparation: Samples for Transmission Geometry The sample is now ready for use with a PW3064/60 or PW3076/00 sample spinner. Basic XRD Course 21

22 Sample Preparation: Samples for Transmission Geometry For the preparation of capillary samples, the following items are used: Glass capillaries, inner diameter mm Wax tablets Dusting brush Spatula Night light (alternatively candle can be used) Lighter Plastic coffee cup Furthermore, on the picture a goniometer head, a set of capillary holders and a screw driver for alignment purpose are shown. Basic XRD Course 22

23 Sample Preparation: Samples for Transmission Geometry The plastic coffee cup is used as a capillary sample preparation table. A strip is cut from the cup. Basic XRD Course 23

24 Sample Preparation: Samples for Transmission Geometry A hole is pierced in the bottom of the cup. Basic XRD Course 24

25 Sample Preparation: Samples for Transmission Geometry A glass capillary can be inserted in the hole. Basic XRD Course 25

26 Sample Preparation: Samples for Transmission Geometry The coffee cup is used as a capillary sample preparation table. The powder can now be inserted into the capillary. Use the spatula to pick up small amounts of powder and put it carefully into the capillary. Basic XRD Course 26

27 Sample Preparation: Samples for Transmission Geometry The filling of the capillary can be observed through the opening cut into the cup. Tap the cup gently to ensure that the powder sinks to the bottom of the capillary. Basic XRD Course 27

28 Sample Preparation: Samples for Transmission Geometry When the capillary is full, take it out of the cup and seal the open end using a small flame from a night light or a candle. Basic XRD Course 28

29 Sample Preparation: Samples for Transmission Geometry Melt some wax or use a little bit of molten candle-wax to fill the capillary holder, the part that you will use to mount the capillary onto the goniometer head. Basic XRD Course 29

30 Sample Preparation: Samples for Transmission Geometry Fix the capillary in the capillary holder. When the wax or the candle-wax is solidified, the capillary is ready for use. Be very careful and ensure that the capillary is mounted in such a way, that it is aligned with the capillary holder. This makes alignment of the capillary with respect to the X-ray beam easier. Basic XRD Course 30

31 Sample Preparation: Samples for Transmission Geometry The capillary sample can now be mounted into the goniometer head. This goniometer head fits on the PW3063 PreFIX capillary spinner stage. Alignment with respect to the X-ray beam is done on the goniometer with the use of an alignment microscope. Basic XRD Course 31

32 Sample Preparation: Stationary Sample Holders This presentation gives a description of the preparation of powder samples in PW1172/01 sample holders according to the backloading technique. The preparation of samples for analysis is of critical importance if accurate and fast results are to be obtained, and the procedures detailed in this section should be careful followed. Additionally, the introduction of errors such as contamination, material loss, alteration of composition, especially of the sample surface, and change of lattice type during the course of sample preparation and afterwards, should be avoided. Contamination of the sample can be caused by dust, by material from a previous sample that remained in the sample preparation equipment, or by material from the sample preparation equipment resulting from abrasion. Material loss is attributed to non-quantitative transfer in concentration determining operations (dilution, binder addition), loss of a small fraction of particle size as dust, and material remaining in the sample preparation equipment. Alteration of composition is attributed to losses of material particles, which are of different composition to the average composition. For example magnetic particles, fine dust, and volatile substances. Also, alteration of composition is attributed to physical or chemical alteration. That is, by decomposition during preparation such as oxidation, loss of combined water or carbon dioxide by overheating and pick-up of water or carbon dioxide from the air, or by the addition of materials of different composition such as by contamination. Basic XRD Course 32

33 Sample Preparation: Stationary Sample Holders PW1172/01 The PW1172/01 (set of 25) sample holders are aluminum holders for powder samples with a volume of 15 mm x 20 mm x 1.8 mm, available for use with X Pert PRO systems without a spinner, but with a PW3071/60 bracket stage for flat samples or with a PW3074/00 multipurpose sample stage. One back plate per sample holder is included, allowing the back-loading technique to be employed in this type of sample holders. Application General powder analysis. Powders, with a particle size less than 25 µm and a small or average density, can usually be analyzed without a binder. Basic XRD Course 33

34 Sample Preparation: Stationary Sample Holders Sample preparation equipment used to prepare specimen for the PW1172/01 sample holders comprises: Cover glass Mortar and pestle Stanley knife blade Adhesive tape Basic XRD Course 34

35 Sample Preparation: Stationary Sample Holders To prepare a powder sample in a PW1172/01 sample holder, proceed as follows: 1. Use self-adhesive tape to secure a glass plate to the front side of the sample holder. Basic XRD Course 35

36 Sample Preparation: Stationary Sample Holders 2. Spread the powder in the holder. Basic XRD Course 36

37 Sample Preparation: Stationary Sample Holders 3. Use a microscope glass to press in the powder. Basic XRD Course 37

38 Sample Preparation: Stationary Sample Holders 4. Remove the surplus of powder above the rim of the holder with a Stanley knife or glass plate. Basic XRD Course 38

39 Sample Preparation: Stationary Sample Holders 5. Secure the back cover to the holder. Basic XRD Course 39

40 Sample Preparation: Stationary Sample Holders 6. Turn the sample holder upside down and remove the glass cover. The sample holder must show a smooth and flat sample surface, which is flush with the sample holder ring. The sample is now ready for use. Note 1: To protect the sample, the front glass plate should not be removed before measuring. Note 2: Insert the sample into the sample stage (PW3071/60 or PW3074/60) only until the sample material is just free from the reference plane of the sample stage. If you push it any further, the sample material could be contaminated with that of previous samples and Al lines from the sample holder may appear in your diffractogram. Basic XRD Course 40

41 Sample Preparation: Stationary Sample Holders Irregular shaped flat samples, pressed pellets or other small solid samples may also be mounted onto the PW1172/01 sample holder. A small amount of plasticine or modeling wax can be used to hold the sample in place. Basic XRD Course 41

42 Sample Preparation: Prepared for Every Sample Basic XRD Course 42

43 Sample Preparation: Prepared for Every Sample The PW18xx range of sample holders is designed for a wide range of sample types up to 44 mm in diameter. These sample holders can be used with the PW3064 PreFIX sample spinner, the PW3072 stationary sample stage or in the PW3061/21 sample holder for solids, which fits on the PW3060/20 all-purpose MRD cradle. They can also be loaded into a sample magazine for the PW3065 sample changers for automatic measurements in X Pert PRO systems. Samples to be loaded in these sample holders can vary in size and shape and can be solids, beads, loose powders etc. The outer rim of the upper surface of the holders is used as a reference plane to ensure optimal accuracy of the sample height. This presentation gives an overview of the various types of sample holders that are available for PANalytical X-ray diffraction systems. Information about application and sample type is included. Basic XRD Course 43

44 Sample Preparation: Prepared for Every Sample PW1811 The PW1811 sample holders consist of a bottom plate (PW1811/00) and a sample holder ring (PW1811/16 or PW1811/27). These sample holders are intended for the manual or semi-automatic preparation of powder samples, which can be either frontloaded or backloaded. The bottom plate supports the powder and enables the automatic loading. The cavity has a diameter of 16 or 27 mm and a height of 2.4 mm. Application PW1811 sample holders are used for general powder analysis. Powders with a particle size less than 25 µm and a small or average density can usually be analyzed without a binder. Basic XRD Course 44

45 Sample Preparation: Prepared for Every Sample PW1770/10 The PW1770/10 powder sample preparation kit is an indispensable tool for preparing powder samples in PW1811 sample holders. It consists of: Sample preparation table onto which the sample holder ring (PW1811/16 or PW1811/27) is clamped Powder press block Dusting brush Stanley knife blade Basic XRD Course 45

46 Sample Preparation: Prepared for Every Sample Sample prepared with the back-loading technique When the sample is prepared according to the backloading technique, the sample surface is flat and flush with the sample holder surface. Such a surface is a requirement for accurate phase analysis using X-ray diffraction in the Bragg-Brentano geometry. Basic XRD Course 46

47 Sample Preparation: Prepared for Every Sample PW1812/00 The PW1812/00 is a general-purpose sample holder for solid samples or powders on a solid support. It consists of a steel loading plate, on which solid samples can be mounted. The samples can be fixed with the use of modeling wax or plasticine. The diameter of the cavity is 44 mm, the maximum sample height is 6.5 mm. Application Analysis of solid samples: irregularly shaped solid materials, metal parts, ceramics, slabs of rock, pressed pellets, or a mounting plate (for example PW1817/32) with a powder specimen. The PW1812/00 can also hold powder samples pressed into a collapsible aluminum cup (PW1526/50). Basic XRD Course 47

48 Sample Preparation: Prepared for Every Sample Mounting of non-standard samples Samples that are irregular in size and shape can be mounted in the sample holder with a little bit of wax or plasticine. The top surface of the outer rim of the sample holder is the reference plane for accurate sample height alignment. Correct sample height alignment is of utmost importance in focusing diffraction geometries, like the Bragg-Brentano geometry. Basic XRD Course 48

49 Sample Preparation: Prepared for Every Sample PW1812/35 The PW1812/35 is a sample pressing ring which can be used with (semi-) automatic sample preparation equipment with a piston diameter of 35 mm. The powder is spread directly into the ring. The top and bottom profiles and the external shape of the ring are compatible with automatic/robotic sample handling equipment, e.g. the PW3065 sample changer used in X Pert PRO systems. Application Automatic analysis of pressed powders, e.g. in the cement industry or process control applications. They fit in PANalytical X-ray spectrometers as well. Basic XRD Course 49

50 Sample Preparation: Prepared for Every Sample PW1813 PW1813 sample holders are designed to mount thin circular solid samples, such as pressed pellets, metal plates, membrane filters or powder sample mounting plates. The PW1813 sample holder consists of a sample holder ring and a bottom plate with a spring to mount flat, circular samples. An aluminum support plate is provided to mount membrane filters. The PW1813 sample holder ring is available in three inner ring diameters sizes: PW1813/26: for samples with a diameter within the range of mm PW1813/32: for samples with a diameter within the range of mm PW1813/40: for samples with a diameter within the range of mm The maximum sample thickness is 6.0 mm. Applications Analysis of air filters for occupational/environmental dust with filter sizes 25 mm (1 inch), 32 mm (1¼ inch) and 38 mm (1½ inch). Pressed pellets, metal plates and other solid objects which fit in the dimensions as given above. The minimum 2Theta angle for each type is dependent on the divergence slit and mask dimensions. Basic XRD Course 50