XRD Proposal

TIR Solar Energy, Inc. XRD Proposal

XRD: Looking Deeper into Quality Control and Characterization of Our ProductsChris DowdyLead, Quality Control Systems [email protected]

Overview

TIR Solar Energy has of late dealt with a large increase of defective solar cells. Of particular note is last year’s six month delay of the South Florida Solar Field Project in Clewiston. The defects on this one project alone cost the company over one half million dollars. As a response, the Quality Control Department has been tasked with determining the cause of these failures. Eliminating them is an imperative. All aspects of our photovoltaic cells were examined and reexamined through on location means and offsite contracted tests. After this myriad of checks, the Quality Control Department has come to a verdict. The titanium dioxide (TiO2 or titania)

nanoparticles used in the solar cells are often faulty. In short, the crystalline structure of the titania nanoparticles for the faulty solar cells are in the wrong phase structure to produce an electric current easily from photonic energy. It appears that during annealing, the phase of some of the titanium dioxide is changing from the needed anatase phase to the much less photon accepting rutile phase [1]. This phase change drastically affects the ability of the solar cell to produce electric power and appears to be the root of the failure problems [1, 2, 3]. In order to improve quality controls for this problem in the production process, this department is proposing the purchase of an X-ray diffractometer (XRD) for regular

Submitted: March 22, 2016

Executive SummaryThe recent spike in solar cell failures experienced by TIR Solar Energy has been attributed to inconsistent titanium dioxide particles used in solar cell production. To institute proper quality controls of this material and to minimize further failures in the field, the purchase of an X-ray diffractometer (XRD) has been proposed. In particular, Quality Control is suggesting the purchase of a Rigaku MiniFlex600 Benchtop XRD Instrument and accessories for just under $95,000.

Page 2 of 33 XRD Proposal

product testing. An XRD is an ideal instrument for testing and determining the crystal phase of a material. An XRD will be able to determine the phase of the titania TIR is producing and allow for the proper adjustments as needed in the production process. An XRD employs X-rays to reflect off of each atomic layer in a sample material [4, 5]. Since the wavelength of an X-ray in in the Ångstrom (Å, 10-10 meters) range, they can penetrate substances into the deeper layers of their atomic structure [4]. Through the use of geometry and some computer software, the intensity of the X-rays and their angles of reflection can verify the crystalline structure of a material. In particular, powder X-ray diffraction analyzes many small crystallites of a material (in TIR’s case, micron sized particles and nanoparticles) measures the intensity of the X-ray diffraction as a function of the angle the X-ray enters the sample [4, 5]. Routine uses of this powder X-ray diffraction technique will be critical in the quality control process for TIR going forward.

What follows is a detailed explanation of XRD metrology, physics and usage as it will affect the processes and quality control at TIR Solar Energy.

Instrument Metrology

Not long after the detection of X-rays by Wilhelm Röntgen in 1895, the scientific world began discovering novel ways to use them [4, 5, 6]. Their very short wavelengths enabled them to travel through different media. And their high energy allowed them to be recorded on photographic film. One interesting application of these two properties was discovered by Max von Laue in 1912. He realized that the lattice network of atoms inside a crystal could be used as a diffraction grating for X-rays and these diffraction patterns could be recorded on photographic film [4, 5, 6]. However, von Laue’s work was later given more thorough meaning and usefulness by Lawrence Bragg. He interpreted von Laue’s work to mean that each plane of atoms in a crystal is another surface from which the deep penetrating X-rays could reflect [4, 5]. X-rays strike each successive plane of atoms in a crystal, diffracting first off the surface layer, then the one below it, and so on. Bragg also formulated that a strong signal from the X-rays would be present if the rays reflecting from all the surfaces were in phase [5]. From this physical phenomenon, Bragg constructed what is today referred to as Bragg’s Law:

nλ=2dsinθ(1)

X-rays of wavelength λ reflect from different surfaces in the lattice of a crystal (d = distance between each surface). These X-rays, entering the crystal at an angle (θ) will diffract out of the crystal at the angle of 2θ. Further, all of the X-rays exiting the material will be in phase with constructive interference if the extra distance that the

Figure 1. Electromagnetic Spectrum [7].

Figure 1.


penetrating X-rays travel is a whole number integer (n) times the wavelength (λ). Figure 2 is a diagram of what Bragg’s Law states.

The process starts with two known variables, λ and θ. Further, by starting X-ray diffraction at a small angle (θ ≤ 5°), n is not a whole number and less than 1. The sample is slowly tilted to increase θ. When the diffracted X-rays are first in phase and producing a strong signal, n equals 1 and the distance between the surfaces (d) in the lattice of the crystal can be determined as the only unknown in the Bragg’s Law formula. The ability to determine the lattice spacing between the vary atoms that constitute a crystal birthed the modern science of crystallography [4]. In particular, Powder XRD runs the same test over a sample that has been ground into a fine powder (particles of > 10 μm). The powder (about a tenth of a gram) is packed onto the sample stage, ideally in many different orientations. As the XRD scans the sample powder, the fluctuations in X-ray intensity are recorded and graphed as 2θ versus intensity [4]. The resulting diffractogram (the graph of intensity peaks) is compared against broad databases of known materials for sample and phase identification [6]. One such database is run by The International Centre for Diffraction Data (http://www.icdd.com/index.htm).

For our purposes here at TIR, qualitative phase analysis of titania particles will allow differentiation between their phase and efficacy for solar energy production. These particles, in both nanoscale and micron sized aggregates, will be best examined using the powder XRD method. Titania is a crystal that has been well characterized and these diffractograms are readily available. There are, however, some unavoidable errors or artifacts that can occur in XRD analysis. Two particular artifacts are of note for qualitative phase analysis of TiO2. The first artifact is libration, or the subtle circular motion of terminal atoms in a crystal lattice network [8]. Libration, depending on the motion of the atoms, can require adjustments of 0.001 to 0.1 Å. The effects of libration are pronounced at high temperatures. Therefore, it is recommended that our testing take place after chilling the materials [8]. The second artifact in play for our purposes is the background data from the sample holder inside the XRD. This will be mitigated by using a “zero-background holder.” Silicon (510) oriented is used for this proposal. A brief explanation of XRD hardware seems appropriate at this time. The XRD produces X-rays in a cathode tube. Inside the cathode tube, a heated filament releases electrons

that accelerate rapidly toward the anode (made from Cu in this proposal). The electrons transmit as a result of a high

Figure 2. Diagram of Bragg’s Law [4].

Figure 2.

Figure 3.

Figure 3. Diagram of X-ray cathode tube [4].


voltage difference between the cathode and anode [4, 6]. As the transmitted electrons hit the Cu atoms, some accelerated electrons dislodge the Cu electrons from their lower electron shells. As electrons from the outer electron shells of Cu move down to fill these holes and achieve more stability, energy is released in the form of X-rays [4, 6].

These X-rays come in three wavelengths and are characteristic for the anode material [4, 5, 6]. The unique wavelengths are labeled Kα1, Kα2, and Kβ, based on from which electron shell the “hole-filling” electron originated. The wavelengths of Kα1

(1.54056 Å) and Kα2 (1.54439 Å) are very close and the difference will be considered negligible the purposes of TIR. The wavelength of Kβ (1.39222 Å) is filtered out by a nickel foil [4]. After leaving the X-ray cathode tube, the X-ray beam, travels through soller slits and a divergence slit to position the beam onto the sample. The X-ray beam then diffracts off of the sample and through more slits and a filter before striking the X-ray detector [4, 9].

The XRD instrument in this proposal moves the beam source and detector as a θ/θ rate while scanning the sample. The software connected to the XRD then interprets the data from the detector and constructs a diffractogram (a plot of 2θ vs. X-ray intensity). This diffractogram is the signature that helps identify the phase of the sample based upon accepted reference samples [6, 9]. Due to the straightforward qualitative phase analysis needs of TIR, no additional accessories or software packages will be needed.

TiO2 Specific Physics

For Quality Control purposes, titania particles need to be characterized by their crystalline phase, either anatase (desired phase) or rutile (undesirable phase). As a means of regular quality control, a sample of titania nanoparticles will be removed from each synthesized lot and dried. The dried, aggregated nanoparticles will be ground into a powder and analyzed in the XRD. Figure 6 is a side by side of the normal diffractograms for both anatase and rutile titania.

Figure 4. Diagram of X-ray emission from an atom [4].

Figure 4.

Figure 5.

Figure 5. Diagram of the X-ray beam path inside an XRD [4].

Figure 6.


The rutile and anatase phases share intensity peaks at 2θ = 28°, 36°, 42°, 54°, 57°, and minor peak pairs at 63°, 64° and 69°, 70°. The anatase phase has noticeably unique intensity peaks at 2θ = 25°, 48°. The rutile phase has a unique intensity peak at 2θ = 39° [10]. The two phases have diffractograms that are similar. However, enough difference exists between them to use the XRD for definitive quality control. The difference is due to different planes in the anatase crystal lattice compared to the rutile. These different planes produce different reflection intensity points in the XRD scan. Anatase titania has a bravais lattice structure of tetragonal I (body centered) [11], while rutile titania has a bravais lattice structure of tetragonal P (body centered) [12].

The lattice structure of anatase has an atom in the center of the unit cell and, therefore, has more planes that can be formed inside the lattice [4]. The increase in planes upon which the X-rays can diffract is the reason that anatase has more intensity peaks than rutile in Figure 6. The increase in number of lattice planes is also the reason the XRD can characterize anatase versus rutile titania. Figure 8 and Figure 9 are diagrams of the atomic lattice of anatase titania and rutile titania, respectively. White balls represent titanium and red balls represent oxygen.

Figure 6. Plot of relative intensity peaks for anatase and rutile TiO2 [10].

Figure 7.

Figure 7. Diagram of rutile and anatase bravais lattice structures [4].

Rutile Anatase

Figure 8.


Understanding the lattice network of anatase and rutile titania helps further interpret the diffractograms in Figure 6. The noticeably unique intensity peaks on the anatase diffractogram are recorded as A(101) and A(200) [10]. The ‘A’ refers to anatase. However, the three numbers in

parentheses refer to the Miller indices [4]. In the short, the Miller indices refer to ways a unit cell of a crystal lattice can be divided into different planes. The three numbers in a Miller index should be thought of as individual numbers, not a three digit number. Each individual number refers to how many times one axis of the unit cell is divided in 3-D space. The first number refers to the conventional x-axis, the second to the y-axis and the third to the z-axis. (Note: x, y and z, popularly known geometry terms, are commonly referred to as a, b and c in crystallography terms. [4]) Therefore, the intensity peak at A(101) means the XRD detected a diffraction from the plane dividing the a axis and c axis of the of the crystal lattice unit cell. Unfortunately, with limited access to graphic software, this proposal cannot illustrate the (101) plane. However, the intensity peak at A(200) is illustrated in Figure 10, bisecting the a axis.

This data means that the XRD detected constructive X-ray interference as a result of diffracting with this plane of atoms in the

Figure 8. Diagram of the atomic lattice of anatase titania [11].

Figure 9.

Figure 9. Diagram of the atomic lattice of rutile titania [12].

Figure 10.

Figure 10. Illustration of a Miller index of (200) [4].


crystal. For the quality control purposes of TIR, since this plane of atoms does not exist in the rutile phase, the existence of this intensity peak would prove qualitatively that the titania produced in this lot was in the correct phase for our applications. Thankfully, current XRD instruments come equipped with software that rapidly interpret these X-ray intensity peaks as differing planes, saving researchers much time and effort by comparing the scanned results to standard reference data.While this qualitative analysis for titania appears straightforward, several issues can arise in the process creating artifacts that must be considered in the collected data. First, the sample must be scanned at the appropriate speed. Several publications caution against scanning samples too quickly [4, 13], despite manufacturer claims of “faster analysis” [14]. While state of the art instruments are no doubt more efficient than their predecessors, rushing through scientific investigation has never been a recipe for success. The second issue that can arise with a fine powder sample is that the sample can fall of the stage in some diffractometers. In diffractometers where the stage rotates at the angle θ and the detector rotates at 2θ, spilling the sample can be a common problem [4]. To alleviate this concern, Quality Control is proposing a vertically orientated XRD where the stage is stationary. In this XRD set up, the detector and the X-ray beam source move at a θ/θ rate. The proper geometry is maintained, however, the sample is not inclined to spill [14]. As well, the sample preparation process itself can create artifacts in the data. Great care should be taken in the milling procedure. Particles ideally should measure between 5 μm to 10 μm [4, 6]. Over milling can create coarse particles and actually

breakdown the crystal structure of the material. Without a proper crystal structure, XRD is not a useful measurement technique [4, 6]. 10 minutes of milling at 200 rpm is recommended for these tests. Also, the powder sample needs to be packed lightly flat without causing the sample to take on a single crystal orientation. Rough sample surfacess can broaden X-ray spectra readings and lower reflection intensities [4, 6]. The ideal scenario for powder XRD is that the crystallite particles are extremely small and the lattice orientations are all random [4, 5, 6, 8, 13]. A recommended flattening technique is discussed in the “Procedures” section below.

Recommended Instrument

The type of crystalline characterization being recommended in this proposal is fairly basic in the realm of XRD. The Quality Control Department is requesting an instrument to simply determine the crystal phase of synthesized titania nanoparticles (the desirable anatase phase or the problematic rutile phase). Because powder XRD is easily set up for qualitative phase analysis the needs for this proposal are not overly stringent. A simple, modern XRD instrument will meet the needs of TIR. Quality Control was looking for an instrument with the following minimum specification (reasoning stated in the sections above):

A vertical set up (θ/θ rotation of X-ray beam and detector, keeping the sample base level and avoiding powder spills).

Compact space needs (as the Quality Control Lab is a moderate sized room).


User-friendly software which connects to highly reviewed reference data samples.

Use of Cu in the X-ray tube for a characteristic spectrum of Kα1 (1.54056 Å) and Kα2 (1.54439 Å).

Full range angle scanning (0° ≤ 2θ ≤ 140°).

The ability to scan at variable speeds (1°/min ≤ 2θ/min ≤ 10°/min).

Affordable pricing.As well, the Quality Control Department had the following preferences when seeking out the proper XRD unit:

An XRD instrument that could operate without the need of a heat exchange cooler (as space is limited in the Quality Control Lab).

A Kβ X-ray filter that comes standard.As a result of these conditions, the Quality Control Department originally proposed the purchase of a Rigaku MiniFlex300 Benchtop XRD Instrument. This device is small enough to be placed on a tabletop, yet powerful enough to provide the quality control measures TIR needs [14]. In its standard package, the Miniflex300 meets or exceeds every one of the requirements and preferences listed above. However, for the same price, TIR could buy the Rigaku Miniflex600 (600 watt model). There are two main differences between these models: First, the 600 has twice the X-ray intensity of the 300 which will allow for much better analysis. Second, because of the higher wattage, the 600 does need a separate heat exchange cooler, which comes with the machine at no extra cost. While the smaller footprint was a preference for the purchase, Quality Control has decided that the increased X-ray beam power for no extra cost is work reorganizing the lab. Therefore, the purchase of a Rigaku Miniflex600 XRD is

endorsed. Below is a list of how this machine stacks up against the specifications and requirements listed above:

Vertical Set Up – The Miniflex600 has the desired θ/θ X-ray tube to detector set up at a 15 cm radius in the sample chamber [14].

Compact Space – The Miniflex600 has dimensions of 0.56 m x 0.53 m x 0.7 m (w x d x h) [14]. It is smaller than a meter in all directions so it will easily fit on a table in the lab.

User-friendly software – This XRD comes with the PDXL software package [14]. Upon investigation, the Quality Control Department is confident that this software is both useful and usable. As well, it readily links to the International Centre for Diffraction Data Powder Diffraction File for reference [4, 6].

Cu Characteristic X-ray Spectrum – The Miniflex600 comes standard with a Cu anode in the X-ray tube [14].

Full Range Angle Scanning – This XRD offers a scanning range even greater than the desired specifications. The Miniflex600’s scanning range is -3° ≤ 2θ ≤ 145° [14].

Variable Scanning Speeds – The Rigaku Miniflex600, as a standard option, offers a greater range of scanning speeds than required. This XRD has scanning speeds of 0.01°/min to 100°/min (2θ) [14]. No Heat Exchange Cooler – This XRD, operating at 600 watts does require an external cooler. However, at no extra cost, the Department has decided to reorganize the Quality Control Lab to accommodate the added equipment.

Kβ X-ray Filter – The Miniflex600 offers a nickel foil Kβ X-ray filter as a standard feature.

X


Further, the Rigaku Miniflex600, through the use of standard features, would give TIR Quality Control an additional method to evaluate the size dimensions of TiO2

nanoparticles. Currently, this quality control measurement is performed exclusively on the company’s scanning electron microscope (SEM). However, for certain situations and following the best practice of redundant verification, this second method of size measurement could be very useful. A brief discussion of why XRD could be useful in nanoparticle size measurement is found in APPENDIX A. As the base model for an XRD unit, it is affordably priced in its category at $75,782. The full Miniflex600 quote from Rigaku can be found in APPENDIX B. As well, the entire Bill of Materials for this request, including accessories and peripheral equipment, is included in APPENDIX C.

Procedures

Below are the proposed procedures for operating the XRD and running the necessary quality control tests.

Safety Precautions (Adapted from Yale University.) [15]1. Read the Operator’s Manuel of the

equipment prior to initial use. As well, this document should be reviewed yearly.

2. Visually inspect the XRD prior to every use for any noticeable cracks or breaks in the shielding.

3. The X-ray tube should never be turned on when the sample chamber is open.

4. Workers are encouraged not to linger near the machine while a test is being

run. However, they should check for warning lights on a regular basis.

5. A sign must be posted near the XRD stating, “Caution! High Intensity X-ray Bean in Use!”

6. Workers using the XRD should wear radiation monitoring badges.

Sample Preparation1. A 5 mL aliquot from each daily lot of

titanium dioxide nanoparticles will be gathered and freeze dried.

2. Grind the sample to a fine powder in the planetary ball mill (10 minutes at 200 rpm) [6]. Powder particles ≤ 10 μm are preferred [4, 6].

3. Place onto the sample surface. Carefully flatten the sample powder surface with a glass slide. The top surface of the powder should be flat to achieve a random distribution of lattice orientations [6].

The instructions for operating the Rigaku Miniflex600 cited below are adapted from the XRD Research Lab at Princeton University.

* Instructions for using the Rigaku Miniflex600 X-ray Diffractometer (XRD)

Startup 1. Turn on main switch to XRD in the back.2. IMPORTANT: Ensure no sample is being

X-rayed before sliding open the door of the XRD. Load the sample into the XRD chamber.

3. When the green ready light turns on, turn X-ray tube on. The green ready light will go out and the X-ray light will take 10-15 sec to turn on.

Sample Testing


1. Boot up the computer, if not started already. (User: Administrator, Password: TIRXRD) Double-click “Standard Measurement” from the desktop.

2. Fill in the condition line(s), from left to right. Click or double-click the cell to alter the parameters as needed).

3. Toggle between “No” and “Yes” on whether or not to use the condition line.

4. Toggle between “No” and “Yes” on whether or not to print the output.

5. Input the “Folder Name.” This is the directory path where the data will be saved.

6. Set the “File name.” 7. Set the “Sample Name.” This is the

description of the sample for identification purposes.

8. Set the “Condition.” Specify the conditions of the scan (Default: 5° to 140° 2θ, 0.01 degree step size, 0.6 sec dwell time). The total time required for the scan will be 67.5 min. Each numerical tab is a different condition setting. For custom settings, change parameters in later numbers.

9. Press the yellow “Execute Measurement” button in the upper left of the window to begin scan.

Shut Down1. After the data is collected, it will be

saved in the chosen directory. Use PDXL (User: Administrator, No password needed) to analyze patterns. The PDXL User manual is available through the “Help” menu.

2. Turn off the X-ray tube and computer when finished. Wait 15 min for X-ray tube to cool down before switching off the main power supply.

Basic Instructions for Operation of PDXL Software

Starting the Software1. Double click on the PDXL icon, located on

desktop or found in “Start Menu.” (User: Administrator, No password needed)

2. In the “Flow” column on the left, click “Data Process.” Confirm on the right column that “Auto” is selected in the “Analysis – Data process” bar.

Opening a File1. Click on “File,” then “Load Measurement

Data.” 2. Find and select the folder, where your

data is stored.

Identifying Crystalline Phases1. Click on “Data Process” on the left side of

the “Flow” window.2. Click on “Auto Search…” in the right side

of the “Analysis – Identification (Auto Search)” window.

3. Within the “Sub-file” tab, select “All sub-files.”

4. Select the “Elements” filter tab. A periodic table will open up.

5. Select the “Other” tab. Click the “Default” button and check the “Show only phases with RIR” value box.

6. Click the “Execute” button when ready to initiate the search.

7. The “Candidate phase” window will populate with best (low) figure of merit (FOM) values. Select both “Titanium Dioxide - Rutile” and “Titanium Dioxide- Anatase.”

8. Once candidate phases are chosen, click “Set” in the lower right. Peaks shown in the “Information” window will have the appropriate phases assigned to them (scroll to the right to see them).


9. Click on “Load Card Info…” on the left

side of the “Flow” window. This transitions from searching the database to being able to look at how the chosen/set candidate phases match up to the test spectrum. Click “Card Info…” in the “Information” window on the right side. A card search window will pop up. Notice that while this search window is open, there is additional labeling on the spectrum. The candidate phases have markings where the peaks are registered in the database.

10. Pull up database card information as needed. This allows you to visualize how the pattern changes with different crystal symmetries. Clicking the checkbox of a particular search result will overlay the database information on the spectrum data.

11. Record the titania phase of the sample.

Loading Crystal Structure Parameters1. Click the “Phase Information” tab in the

“Information” window, then the “Crystal Structure” information tab.

2. Select the phase candidate for which you wish to import crystal information, then click “Import CIF…” to select the .cif file and import the crystal structure parameters.

Saving Data

1. Click “File,” then “Export Graph As,” then “CSV Format.”

2. Choose the location where the file should be stored.

3. Type in a filename. Click “OK.”

* Princeton University, Rigaku Miniflex600 XRD Instructions,https://iac.princeton.edu/manuals/Rigaku_Miniflex_XRD%20(new).pdf

Data Output

Data recorded from an XRD typically comes in one or both of two formats: As a diffractogram (illustrated and explained previously in Figure 6 on page 4) or as a peak list [4]. A peak list is a simple table that displays the pertinent data from the XRD analysis. An example of a peak list for anatase titanium dioxide is found in Table 1. The peak list states at one glance which 2θ angles showed intensity peaks, what those peaks were and the d-spacing between the lattice points for that diffraction intensity. The peak list is a useful tool. This is the data that the PDXL software uses to compare against the reference database and

Table 1.

Table 1. Peak list for anatase titanium dioxide [16].

https://iac.princeton.edu/manuals/Rigaku_Miniflex_XRD%20(new).pdf

https://iac.princeton.edu/manuals/Rigaku_Miniflex_XRD%20(new).pdf


determine the phase of the titania sample. As mentioned earlier when discussing the diffractogram, the data recorded from a

rutile titania has clear distinctions from anatase titania, meaning XRD analysis is the ideal method for quality control in this area.

Conclusion

In response to the recent failures of TIR manufactured solar panels due to wrong phased rutile titanium dioxide, the quality control mechanisms used by the company must adapt. As outlined extensively above, X-ray diffraction analysis is the best method for phase determination in crystalline structures like titania. Therefore, the Quality Control Department is proposing the purchase of a Rigaku Miniflex600 XRD at a total price just under $100,000. While the Quality Control Department realizes this is a significant investment for the company, its fruits outweigh the costs of continued and multiplied solar cell failures in the field.


References

[1] Jeffryes, Clayton, Jeremy Campbell, Haiyan Li, Jun Jiao, and Gregory Rorrer. 2011. "The Potential of Diatom Nanobiotechnology for Applications in Solar Cells,Batteries,and Electroluminescent Devices." The Royal Society of Chemistry. doi:10.1039/c0ee00306a.

[2] Information, National Center for Biotechnology, Medicine, U S National Library of and Pike, 8600 R. "TITANIUM DIOXIDE | O2Ti - PubChem.", accessed March 15, 2016, https://pubchem.ncbi.nlm.nih.gov/compound/titanium_dioxide#section=Top..

[3] Mohammadi, M. R., A. Mohammadi, and D. J. Fray. 2008. "Sol–gel Nanostructured Titanium Dioxide: Controlling the Crystal Structure, Crystallite Size, Phase Transformation, Packing and Ordering." Microporous and Mesoporous Materials 112 (1): 392-402. doi:10.1016/j.micromeso.2007.10.015. http://www.sciencedirect.com/science/article/pii/S1387181107006014.

[4] Ermrich, Martin. 2013. X-ray Powder

Diffraction: XRD for the Analyst. 2nd ed. Almelo, The Netherlands: PANalytical.

[5] "Cambridge Physics - X-ray Diffraction.", accessed March 15, 2016, http://www-outreach.phy.cam.ac.uk/camphy/xraydiffraction/xraydiffraction5_1.htm.

[6] Dutrow, Barbara L. and Clark, Christine M. "X-ray Powder Diffraction (XRD)." X-ray Powder Diffraction (XRD)., accessed March 15, 2016,

http://serc.carleton.edu/research_education/geochemsheets/techniques/XRD.html.

[7] Shapley, Patricia. "Light and the Electromagnetic Spectrum." University of Illinois., accessed March 15, 2016, http://butane.chem.uiuc.edu/pshapley/GenChem2/A3/3.html.

[8] MIT OpenCourseware. 2012. "Artefacts." 83 (1): 231-234. doi:10.1111/j.1600-0390.2012.00695.x. http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0390.2012.00695.x/abstract.

[9] Barnes, Paul, Csoka, Tony and Jacques, Simon. "Bragg's Law." Birkbeck College, University of London., accessed March 15, 2016, http://pd.chem.ucl.ac.uk/pdnn/powintro/braggs.htm.

[10] Zhao, A. S., S. Zhou, Y. Wang, J. Chen, C. R. Ye, and N. Huang. 2014. "Molecular Interaction of Fibrinogen with Thermally Modified Titanium Dioxide Nanoparticles." RSC Advances 4 (76): 40428-40434.

[11] "TiO2 - Anatase: Interactive 3D Structure is Loaded." The University of Liverpool., accessed March 16, 2016, http://www.chemtube3d.com/solidstate/_anatase(final).htm.

[12] "TiO2 - Rutile: Interactive 3D Structure is Loaded." The University of Liverpool., accessed March 16, 2016, http://www.chemtube3d.com/solidstate/_rutile(final).htm.

[13] Spurr, Robert A. and Howard Myers. 1957. "Quantitative Analysis of Anatase-Rutile Mixtures with an X-ray Diffractometer." Analytical Chemistry 29 (5): 760-762. http://web.stanford.edu/group/glam/xlab/Paper_2.pdf.


[14] "Benchtop X-ray Diffraction (XRD) Instrument | Rigaku - X-ray Analytical Instrumentation." Rigaku Corporation., accessed March 16, 2016, http://www.rigaku.com/en/products/xrd/miniflex.

[15] Yale Environmental Health and Safety. "X-ray Diffraction Safety." ehs.yale.edu., last modified December 12, accessed March 21, 2016, http://ehs.yale.edu/training/X-ray-diffraction-safety.

[16] Theivasanthi, T. and M. Alagar. 2013. "Titanium Dioxide (TiO2) Nanoparticles XRD Analyses: An Insight." . http://arxiv.org/abs/1307.1091.


APPENDIX A – Using an XRD for Sizing Powder Particles*

An XRD can be used to size particles in addition to defining the crystal lattice structure. The shape of the reflectivity curve (produced by the measurement of the reflection intensity versus 2θ) leads to analyzable characteristics. Characteristics being analyzed include layer thickness, layer density, surface/interface roughness, and quality of layers/interfaces. When analyzed particles are very small (in the nanoscale world), the reflectivity curve can also be used to determine the average size of the particles. These complex calculations are done through the use of the software included with the XRD.

The XRD is an effective instrument for measuring the size of crystallite particles and in some ways to be preferred to many other instruments. First, XRD allows for the analysis of layers of particles rather than having to disperse particles into a single layer needed for other analysis methods. Second, XRD determines whether the particle is a single crystal or a composite of crystals. This data can be very important for characterization purposes. As well, XRD is able to determine the average crystallite size rather than the merely the particle size. The crystallite size is generally smaller than the particle size and often useful data.

ReferenceErmrich, Martin. 2013. X-ray Powder Diffraction: XRD for the Analyst. 2nd ed. Almelo, The

Netherlands: PANalytical.

*Compiled with assistance from Holly Pafford, Joseph Zarth and Shelby Sims.


APPENDIX B – Quote from Rigaku



















APPENDIX C – Bill of Materials

Item Cost

Rigaku MiniFlex600 XRD $75,782 http://www.rigaku.com/en/products/xrd/miniflex

Planetary Ball Mill $2,890 http://www.amazon.com/Ultrafine-Powder-Grinder-Planetary-50-100ml/dp/B01B51WIIE

Titanium Dioxide Powder NIST Reference Material $684 https://www-s.nist.gov/srmors/view_detail.cfm?srm=8988

PDF-4, International Centre for Diffraction Data $8,660 http://www.icdd.com/products/2016-ICDD-Price-List.pdf

Radiation Badges $400 http://www.chpdosimetry.com/products.php

Sub-Total: $88,416Tax (7%): $6190

Total: $94,606

Documents

XRD Proposal