This research was funded by the International Research Training Group (IRTG) &#8220;Diffusion in porous Materials&#8221;. We acknowledge the technical support from Gert Klotzsche and stimulating discussions with Steven Reichhardt, Thomas Meissner, Damian Rybicki, Tobias Herzig, Natalya Georgieva, Jonas Kohlrautz, and Michael Jurkutat.

1. Mounting and Aligning of the 6H-SiC Large Cone Boehler-type Anvils
<ol>
	<li>Fix the piston and x-y plate in the mounting tools and insert the Boehler-type anvils in the seating area.</li>
	<li>Make sure each anvil sits firmly in the backing plates.</li>
	<li>Using epoxy resin, (e.g., Stycast 1266), glue both anvils to their seats. Cure for 12 h at RT, or 65 &#186;C in a furnace for 2 hr.</li>
	<li>For a sufficient anvil alignment, use the M1 set-screws to align the backing plates and monitor the parallelism of both anvils. If the anvils were found to be non-parallel, remove the epoxy resin and restart at point 1.2.</li>
</ol>
2. Gasket Preparation
<ol>
	<li>Drill 1 mm holes into a chip of annealed Cu-Be (Cu 98 w%, Be 2 wt%, thickness of 0.5 mm) for the brass guide pins.</li>
	<li>Insert three 5 mm long pieces of 1 mm diameter non-insulated copper wire into the holes, which are distributed along the anvil, to serve as guide pins for the Cu-Be gasket.</li>
	<li>Check for proper grounding between the guide pins and the cell body. Typically, a DC resistance of about 0.1 &#937; is desired. Improve with an application of a small amount of conductive silver.</li>
	<li>Place the Cu-Be chip on top of the moissanite anvil and close the cell.</li>
	<li>Using a hydraulic press, pressurize the gasket to about 1/8th of the culet diameter for maximized working stability. Monitor the actual thickness of the indentation using a micrometer caliper.</li>
	<li>Drill a hole of the appropriate diameter (&#189; of the culet diameter) in the center of the indentation.</li>
	<li>Carve two channels into the pre-indented gasket. The channels should be deep enough to accommodate the 18 &#181;m copper wire of the micro-coil.</li>
	<li>Harden the prepared gasket at 617 K for 2 to 3 hr in a furnace.</li>
</ol>
3. Preparing and Loading of the Micro-coil
<ol>
	<li>Use a piece of 1 mm copper wire and thread it through the feed-through of the piston. Fix the copper wire with epoxy resin and cure it according to step 1.3.</li>
	<li>Choose an awl (see list of materials) which has the desired diameter for the micro-coil and fix it between a pair of rotatable chuck-jaws.</li>
	<li>Glue (with e.g., varnish from SCB, see list of materials) one end of the 18 &#181;m copper wire onto the chuck jaws, while holding the other end and rotate the chuck jaw so that the wire is coiled onto the awl.</li>
	<li>When the micro-coil is of the desired geometry, fix the other end of the wire onto the glue as well.</li>
	<li>Use diluted varnish to fix the coil by applying a small amount on top of the windings.</li>
	<li>Remove the coil carefully from the awl using Teflon tape.</li>
	<li>Place some epoxy resin (see point 1.3), without any additives, in the channels of the gasket.</li>
	<li>Place the micro-coil inside the sample chamber and fix the leads into the channels.</li>
	<li>Cure the epoxy resin according to step 1.3.</li>
	<li>Solder one lead of the micro-coil to the hot wire and the other to a guide pin.</li>
	<li>Add some silver conductive paste on top of each junction. Curing typically takes some minutes.</li>
	<li>Seal both junctions with a small amount of epoxy resin.</li>
	<li>Cure the epoxy according to step 1.3.</li>
	<li>Now, check the DC resistance of the coil after every step.</li>
	<li>Place the sample in the micro-coil. Be aware that any unnecessary physical contact may destroy the coil.</li>
	<li>Add finely ground ruby powder to the sample for pressure calibration.</li>
	<li>Finally, flood the sample chamber with an appropriate pressure medium. Use paraffin oil to ensure nearly-hydrostatic conditions up to 9 GPa.</li>
	<li>Close the cell carefully.</li>
</ol>
4. Applying and Monitoring Pressure
<ol>
	<li>At first, slightly tighten the M3 Allen countersunk screws.</li>
	<li>For pressurization fix the cell in a vise. Now, tighten two opposing screws pairwise.</li>
	<li>Place the pressurized cell in an appropriate cell holder.</li>
	<li>Adjust the position of the cell so that the laser beam reaches the sample chamber.</li>
	<li>Use the fine-adjustment table to focus the ruby powder in the laser beam.</li>
	<li>Monitor the ruby photoluminescence spectrum using the corresponding spectrometer software.</li>
	<li>Extract the actual pressure in the sample cavity from the observed spectral shift of the ruby R1 and R2 lines.</li>
	<li>Equilibrate the pressurized cell for at least 12 hr before NMR measurements are started.</li>
</ol>
5. Performing NMR Experiments
<ol>
	<li>Mount the pressure cell onto a typical NMR probe. Manufacture appropriate cell holders in a mechanical workshop.</li>
	<li>Solder the hot wire to the probe. Check for proper electrical contact between the cell and the probe.</li>
	<li>Now, perform standard NMR experiments. Draw attention to the fact that the micro-coil is very sensitive to the applied radio-frequency power.</li>
</ol>

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E., Stillwell, R. L., Purcell, K. M., Tozer, S. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nonmetallic+gasket+and+miniature+plastic+turnbuckle+diamond+anvil+cell+for+pulsed+magnetic+field+studies+at+cryogenic+temperatures.">Nonmetallic gasket and miniature plastic turnbuckle diamond anvil cell for pulsed magnetic field studies at cryogenic temperatures.</a> High Pressure Research. 31 (4), 533-543 (2011).</li><li>Pravica, M., Silvera, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NMR+Study+of+Ortho-Para+Conversion+at+High+Pressure+in+Hydrogen.">NMR Study of Ortho-Para Conversion at High Pressure in Hydrogen.</a> Physical Review Letters. 81 (19), 4180-4183 (1998).</li><li>Haase, J., Goh, S. K., Meissner, T., Alireza, P. L., Rybicki, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+sensitivity+nuclear+magnetic+resonance+probe+for+anvil+cell+pressure+experiments.">High sensitivity nuclear magnetic resonance probe for anvil cell pressure experiments.</a> Rev Sci Instrum. 80 (7), 73905 (2009).</li><li>Meissner, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+Approach+to+High-Pressure+Nuclear+Magnetic+Resonance+with+Anvil+Cells.">New Approach to High-Pressure Nuclear Magnetic Resonance with Anvil Cells.</a> J Low Temp Phys. 159 (1-2), 284-287 (2010).</li><li>Meier, T., Herzig, T., Haase, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Moissanite+Anvil+Cell+Design+for+Giga-Pascal+Nuclear+Magnetic+Resonance.">Moissanite Anvil Cell Design for Giga-Pascal Nuclear Magnetic Resonance.</a> Rev Sci Instrum. 85 (4), 43903 (2014).</li><li>Boyer, R. F., Collings, E. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Materials Properties Handbook: Titanium Alloys. , (1994).</li><li>Xu, J. -. a., Yen, J., Wang, Y., Huang, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ultrahigh+pressures+in+gem+anvil+cells.">Ultrahigh pressures in gem anvil cells.</a> High Pressure Research. 15 (2), 127-134 (1996).</li><li>Xu, J. -. a., Mao, H. -. k., Hemley, R. J., Hines, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+moissanite+anvil+cell+a+new+tool+for+high-pressure+research.">The moissanite anvil cell a new tool for high-pressure research.</a> J Phys Condens Matter. 14 (44), 11543-11548 (2002).</li><li>Xu, J. -. a., Mao, H. -. k., Hemley, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+gem+anvil+cell+high-pressure+behaviour+of+diamond+and+related+materials.">The gem anvil cell high-pressure behaviour of diamond and related materials.</a> J Phys Condens Matter. 14 (44), 11549-11552 (2002).</li><li>Meissner, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nuclear+magnetic+resonance+at+up+to+10.1+GPa+pressure+detects+an+electronic+topological+transition+in+aluminum+metal.">Nuclear magnetic resonance at up to 10.1 GPa pressure detects an electronic topological transition in aluminum metal.</a> J Phys Condens Matter. 26 (1), 15501 (2014).</li><li>Meissner, T., Goh, S. K., Haase, J., Williams, G. r. a. n. t. . V. M., Littlewood, P. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-pressure+spin+shifts+in+the+pseudogap+regime+of+superconducting+YBa2Cu4O8+as+revealed+by+17O+NMR.">High-pressure spin shifts in the pseudogap regime of superconducting YBa2Cu4O8 as revealed by 17O NMR.</a> Phys Rev B. 83 (22), (2011).</li><li>Goh, S. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+pressure+de+Haas&#8211;van+Alphen+studies+of+Sr2RuO4+using+an+anvil+cell.">High pressure de Haas&#8211;van Alphen studies of Sr2RuO4 using an anvil cell.</a> Current Applied Physics. 8 (3-4), 304-307 (2008).</li><li>Tateiwa, N., Haga, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluations+of+pressure-transmitting+media+for+cryogenic+experiments+with+diamond+anvil+cell.">Evaluations of pressure-transmitting media for cryogenic experiments with diamond anvil cell.</a> Rev Sci Instrum. 80 (12), 123901 (2009).</li><li>Hahn, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spin+Echoes.">Spin Echoes.</a> Phys Rev. 80 (4), 580-594 (1950).</li><li>Boehler, R., Ross, M., Boercker, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Melting+of+LiF+and+NaCl+to+1+Mbar+Systematics+of+Ionic+Solids+at+Extreme+Conditions.">Melting of LiF and NaCl to 1 Mbar Systematics of Ionic Solids at Extreme Conditions.</a> Physical Review Letters. 78 (24), 4589-4592 (1997).</li><li>Funamori, N., Sato, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+cubic+boron+nitride+gasket+for+diamond-anvil+experiments.">A cubic boron nitride gasket for diamond-anvil experiments.</a> Rev Sci Instr. 79 (5), 053903 (2008).</li><li>Forman, R. A., Piermarini, G. J., Barnett, J. D., Block, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pressure+measurement+made+by+the+utilization+of+ruby+sharp-line+luminscence.">Pressure measurement made by the utilization of ruby sharp-line luminscence.</a> Science. 176 (4032), 284-285 (1972).</li></ol>

The authors have nothing to disclose.

A new and promising method to perform NMR at Giga-Pascal pressures was described. This method opens up the door to a broad variety of NMR experiments due to its excellent sensitivity and resolution. Nevertheless, several steps described in the protocol section are crucial to the outcome of the experiment. Especially, the preparation of the micro-coil and its fixation in the Cu-Be gasket is very difficult and requires some experience. In the following, some important tips are given, which should help a first successful application of the technique.
All presented data were obtained using a commercial Apollo or Bruker NMR spectrometers for solid state NMR applications. The magnets were standard wide-bore Bruker magnets with magnetic fields ranging from 7.03 to 17.6 T. Simple home-built NMR probes used for standard NMR experiments were retrofitted to hold the anvil cells.
The cell chassis of the LAC-TM2 should be manufactured according to the blue prints given in the supplementary. Special attention has to be paid to the production of the piston and its corresponding duct in the cell&#39;s shell in order to avoid any kind of clearance. Typically, an accuracy of better than 10 &#181;m is desired to ensure a sufficient working stability of the pressure cells under load. A good machine shop can achieve a dimensional accuracy of 0.01 to 0.015 mm. The required M4 Allen countersunk bolts can either be manufactured as well, or purchased from special companies (e.g., see materials list). Throughout the whole cell preparation, use non-magnetic tools since every contamination with ferromagnetic materials will affect the outcome of the experiments. Therefore, use either a titanium scalpel or a glass-writing diamond when carving the channels into the Cu-Be gasket.
For the steps in number 3, several special tools are needed for best results. For preparing the micro-coil, either a set of chuck jaws or a lathe can be used. For the winding of the micro-coil, conical awls can be used (typically in diameters of 180 &#181;m to 450 &#181;m). For sample loading, a piece of wire or a very sharp needle should be employed. It is important to note that the total height of the coil must not exceed the thickness of the gasket&#39;s pre-indentation. Typically, micro-coils made of 3 to 5 turns (using an 18 &#181;m copper wire) have a height of less than 100 &#181;m, sufficient for 1,000 &#181;m and 800 &#181;m culet anvils. It is crucial to monitor the DC resistance of the micro-coil at every step following step 3.10. Typically, the expected resistance should be around 1 &#937; across the cell, if the resistance breaks down to k&#937; or even M&#937;, the cell must be opened and the procedure restarted, beginning at step 3.1.
A deformation of the RF micro-coil should be avoided. Empirically, it was found that at pressures above 6 GPa, the Cu-Be gasket starts to flatten with pressure, decreasing the height of the sample hole easily below 50 &#181;m, deforming most micro-coils with more than 4 turns considerably. If anvils with a smaller culet size are to be used in order to reach higher pressures, the resulting sample chamber will be reduced in volume considerably (stemming from the requirements of the gasket design for maximized working stability). For example, by going from a pair of 1 mm to 0.8 mm culet anvils, the sample volume will be reduced from about 10 nl to 3 nl and the number of turns of the micro-coil will decrease from 6 to 4 (if 18 &#181;m copper wire is used). This will typically result in a reduction of the SNR by about one order of magnitude.
At this point we want to stress, that the choice of the gasket material can be crucial. The introduced Cu-Be gaskets may not be suited if pressures above 10 GPa are desired since the above mentioned deformation of the sample cavity will eventually destroy the RF micro-coil. An alternative gasket material may be rhenium, which has a much higher mechanical strength and is non-magnetic. Another established approach was introduced by Boehler et.al.29where the inner metallic region of the gasket was substituted with a diamond/epoxy mixture;other groups30 used cubic boron nitride as gasket materials; in order to improve the height to diameter ratio of the sample cavity. This approach was found to be superior to the formerly used metallic gaskets. At this point, the authors gathered some experience with this promising technique which will be published elsewhere.
The threads and bolts of the titanium screws as well as the Allen set keys will wear off after some pressure runs. Therefore, they need to be revised by a machine shop or completely replaced. Choosing the right pressure medium for the experiment is crucial. The pressure calibration, step 4.4, can easily be done using a commercially available optical spectrometer system to observe pressure induced shifts of the R1 and R2 lines of the ruby powder. Further information about this well-known technique is given in the literature31. The loss of hydrostaticity is indicated by a drastic increase in the line-width of the ruby photoluminescence of the R1 and R2 spectra. Best results can be achieved by using liquid nitrogen, liquid noble gases or a 4:1 methanol/ethanol mixture, which are supposed to provide hydrostatic conditions up to pressures in the range of 10 GPa.
The limits of that technique, with respect to standard NMR experiments, lies on the inaccessibility of any magic angle spinning techniques. This drastically limits the resolution to about 5 ppm. On the other hand, NMR measurements on 1H are, at the moment, not recommendable due to the vast variety of spurious proton signals stemming dominantly from the epoxy resin and the polyurethane insulation of the micro-coil as well as the mostly used pressure transmitting medium. Another important point to mention here is that the success of each experiment depend on the samples intrinsic spin relaxation times which sets the length of each acquisition time. Since a fast spectral accumulation is desired in order to reduce the total measurement time, sample with a very long T1 should be avoided.
It has to be pointed out, that 1H-NMR might not be feasible with our design due to the extensive use of epoxy resins, varnishes, and insulated wire for the micro-coils. Nevertheless, if experiments on protons are desired one needs to by-and-large substitute the 1H containing materials (or use 2H for synthesis where possible).
All other approaches for NMR under high hydrostatic pressures suffered from low SNR and therefore rather long required data acquisition times, which rendered a lot of experiments impossible. The shown micro-coil approach overcomes those obstacles by the coil&#39;s dramatically improved filling factor and we have shown that NMR on highly correlated and uncorrelated electron systems is possible.
Finally, we believe that our new anvil cell technique represents a major development in modern condensed matter research. We have shown that this approach enables researchers to perform high sensitivity NMR experiments at pressures up to 10 GPa. First applications prove the power that anvil cell NMR brings to the study of the electronic and chemical structure of modern materials.

Since Percy Bridgman&#39;s hallmark experiments of condensed matter under high hydrostatic pressures at the beginning of the last century, the field of high pressure physics has evolved rapidly1. A large number of intriguing phenomena are known to occur under pressures of several GPa2. In addition, the response of condensed matter systems to high pressure has taught us a lot about their electronic ground and excited states3,4.
Unfortunately, techniques for the investigation of the electronic properties of condensed matter at Giga-Pascal pressures are rare, with x-ray or DC resistance measurements leading the way5. In particular, the detection of electronic or nuclear magnetic moments with electron spin (ESR) or nuclear magnetic resonance (NMR) experiments, is bound to be almost impossible to implement in a typical high-pressure anvil cells where one needs to retrieve the signal from a tiny volume enshrined by anvils and a sealing gasket.
Several groups have tried to solve this problem by using complex arrangements, e.g., two split-pair radio-frequency (RF) coils wound along the flanks of the anvils6; a single or double loop hair-pin resonator7,8; or even a split rhenium gasket as a RF pick-up coil9, see Figure 1. Unfortunately, those approaches still suffered from a low signal-to-noise ratio (SNR), limiting the experimental applications to large-&#947; nuclei such as 1H10. The interested reader may be referred to other high-pressure resonant tank circuit experiments11&#8211;15. Pravica and Silvera16 report the highest pressure achieved in an anvil cell for NMR with 12.8 GPa, who studied the ortho-para conversion of hydrogen.
With great interest in applying NMR to study the properties of quantum solids, our group was interested in having NMR available at high pressures, as well. Finally, in 2009 it could be demonstrated that high-sensitivity anvil cell NMR is indeed possible if a resonating radio-frequency (RF) micro-coil is placed directly in the high-pressure cavity enclosing the sample17. In such an approach, the NMR sensitivity is improved by several orders of magnitude (mostly due to the dramatic increase in filling factor of the RF coil), which made even more challenging NMR experiments possible, e.g.,17O NMR on powder samples of a high-temperature superconductor at up to 7 GPa18. Superconductivity in these materials can be greatly amplified by the application of pressure, and it is now possible to follow this process with a local electronic probe that promises fundamental insight into the governing processes. Another example for the power of NMR under high pressure emerged from what were believed to be routine referencing experiments: in order to test the introduced new anvil cell NMR, one of the best known materials was measured &#8211; simple aluminum metal. As the pressure was increased, an unexpected deviation of the NMR shift from what one would expect for a free-electron system was found. Repeated experiments, also under increased pressures, showed that the new results were indeed reliable. Finally, with band structure calculations it was then found that the results are the manifestation of a topological transition of the Fermi surface of aluminum, which could not be detected by calculations years ago, when the computing power was low. Extrapolation of the findings to ambient conditions showed that the properties of this metal that is used almost everywhere are influenced by this special electronic condition.
In order to pursue a number of different applications specially designed anvil cells (previous cells had been imported from the Cavendish Laboratory and retrofitted for NMR) have been developed. Currently, the used home-built chassis are capable of reaching pressures up to 25 GPa using a pair of 800 &#181;m culet 6H-SiC anvils. NMR experiments were successfully conducted up to 10.1 GPa, so far. The NMR performance of this new cells was shown to be excellent19. The main component is Titanium-Aluminum(6)-Vanadium(4) with an extra low interstitial level (grade 23), providing a yield strength of about 800 MPa20. Due to its non-magnetic properties (the magnetic susceptibility &#967; is about 5 ppm) it is an adequate material for the anvil cell chassis. The overall dimensions of the introduced cells (see Figure 2 for an overview of all home-built anvil cell designs) are small enough to fit into regular standard bore NMR magnets. The smallest design, the LAC-TM1, which is only 20 mm in height and 17 mm in diameter, fits also typical small, cold-bore magnets (30 mm bore diameter). The LAC-TM2, which is the latest chassis the authors designed, uses four M4 Allen countersink bolts (made out of the same alloy as the cell chassis) as pressure driving mechanism, allowing for a smooth control of the internal pressure (blue prints attached in supplementary section).
Typically, diamond anvils are used in order to generate highest pressures of above 100 GPa. Xu and Mao21&#8211;23 have demonstrated that moissanite anvils provide a cost effective alternative in high-pressure research, up to pressures of about 60 GPa. Therefore, moissanite anvils were used for the introduced GPa NMR approach. The best results were achieved with customized large-cone 6H-SiC anvils from the anvil department of Charles &#38; Colvard. With those cells, for pressures up to 10.1 GPa, the use of 800 &#181;m culet anvils was found to result in very good NMR sensitivity. For comparison, Lee et al. report a SNR of 1 for 1H NMR of tap water, while the SNR of the introduced micro-coil approach showed a value of 25 for 1/7 of their volume, even at a somewhat lower magnetic field.
With this new approach to high-sensitivity anvil cell NMR one can pursue many applications that promise exciting new insight into the physics and chemistry of modern materials. However, as always, sensitivity and resolution ultimately limit the application of NMR, in particular, if one is interested in much higher pressures that demand smaller culet sizes. Then, one has not only to optimize the cell design with even smaller RF coils, but also think about methods for increasing nuclear polarization.

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high-sensitivity nuclear magnetic resonance at giga-pascal pressures: a new tool for probing electronic and chemical properties of condensed matter under extreme conditions

Nuclear Magnetic Resonance (NMR) is one of the most important techniques for the study of condensed matter systems, their chemical structure, and their electronic properties. The application of high pressure enables one to synthesize new materials, but the response of known materials to high pressure is a very useful tool for studying their electronic structure and developing theories. For example, high-pressure synthesis might be at the origin of life; and understanding the behavior of small molecules under extreme pressure will tell us more about fundamental processes in our universe. It is no wonder that there has always been great interest in having NMR available at high pressures. Unfortunately, the desired pressures are often well into the Giga-Pascal (GPa) range and require special anvil cell devices where only very small, secluded volumes are available. This has restricted the use of NMR almost entirely in the past, and only recently, a new approach to high-sensitivity GPa NMR, which has a resonating micro-coil inside the sample chamber, was put forward. This approach enables us to achieve high sensitivity with experiments that bring the power of NMR to Giga-Pascal pressure condensed matter research. First applications, the detection of a topological electronic transition in ordinary aluminum metal and the closing of the pseudo-gap in high-temperature superconductivity, show the power of such an approach. Meanwhile, the range of achievable pressures was increased tremendously with a new generation of anvil cells (up to 10.1 GPa), that fit standard-bore NMR magnets. This approach might become a new, important tool for the investigation of many condensed matter systems, in chemistry, geochemistry, and in physics, since we can now watch structural changes with the eyes of a very versatile probe.

Figure 3 shows how the completely assembled pressure cell, the wiring, and the mounting onto a typical NMR probe look like. In the following, several experiments will be reviewed which should enable the reader to gather a broad overview about the benefits and limits of the introduced technique.
<img alt="Figure 1" src="/files/ftp_upload/52243/52243fig1highres.jpg" /> 
Figure 1.&#160;Various Approaches for high pressure NMR: (A) Split pair coil encompassing the anvil flanks as well as a rhenium gasket from Bertani et al. (Reproduced with permissions from Bertani et al.4. Copyright 1992, AIP Publishing LLC.) (B) Hair-pin resonator from Lee et al. (Reproduced with permissions Lee et al.6. Copyright 1992, AIP Publishing LLC.) (C) Pravica et al. introduced a method using a split gasket together with a one turn cover inductor as a radio-frequency pick-up coil. (Reproduced with permissions from Pravica et al.7) <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52243/52243fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" src="/files/ftp_upload/52243/52243fig2highres.jpg" /> 
Figure 2.&#160;Various high pressure anvil cell designs for NMR: All designed cell chassis consist of a simple piston-cylinder set-up without further anvil alignment mechanisms with exception of a planar adjustable conical anvil backing plate. The cylindrical cells TM0 and TM1 are particularly suitable for NMR investigations of single crystals where a proper crystal alignment can be achieved by rotating the cells along their symmetry axis. The overall dimension of all chassis does not exceed 40 mm, enabling them to be used in standard wide-bore NMR magnets. The dimensions of the smallest design (TM1) enables it to be used even for small-bore magnets (overall dimensions 20 mm x 18 mm).
<img alt="Figure 3" src="/files/ftp_upload/52243/52243fig3highres.jpg" /> 
Figure 3.&#160;(A) Photograph of the high-pressure region with a 4-turn micro-coil filled with a liquid gallium sample, ruby powder and pressure transmitting medium. (B) Mounted LAC-TM1 on a home-built NMR probe.&#160;(C) Schematic wiring of the probe connecting the micro-coil in the high-pressure region, see also29. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52243/52243fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
I) 27Al NMR of aluminum powder up to 10.1 GPa24 and 17O NMR of YBa2Cu4O8 up to 6.4 GPa25 
The first experiments were conducted using a Beryllium-Copper diamond anvil cell design from the Cavendish Laboratory at Cambridge University, which was widely used for de Haas-van Alphen measurements26. The cell was readied for high-sensitivity NMR experiments in Leipzig and representative results will be discussed now.
The first set of experiments concern the investigation of metallic aluminum that was believed to be a suitable reference compound. Two different anvil cells were used, equipped with anvils of 1,000 &#181;m culet diameter for pressures up to 4.2 GPa, and with anvils of 800 &#181;m culets for pressures up to 10.1 GPa. The corresponding micro-coils were solenoids with 10 turn (300 &#181;m diameter), and 9 turns (200 &#181;m diameter), for the 1 mm and 0.8 mm culet anvils, respectively. The diameter of the insulated Cu wire was 15 &#181;m. The pressure cells were loaded with finely crushed aluminum powder (3N purity, 325 mesh) and a small ruby chip serving as a pressure sensor. As pressure transmitting media, Daphne 7373 and glycerin were used, providing hydrostatic conditions up to at least 5 GPa27. NMR measurements were conducted in magnetic fields of 7.03 T, 11.75 T, and 17.6 T at RT (field dependent measurements were necessary to investigate the line broadening mechanism). The quality factor Q of the resonance circuit was about 16 for all cells. With nutation experiments, the &#960;/2 pulse length were determined to be about 2 &#181;s at approximately 1 Watt average RF pulse power. Those parameters lead to an average RF magnetic field amplitude B1 in the resonating micro-coil of about B1=&#960;/(2&#947;nt&#960;/2)= 11 mT (the gyromagnetic ratio of 27Al is 6.98&#8729;107 radT-1s-1). This estimate is only a factor of 3 smaller than the theoretical figure, B1=[(&#181;0QP)/(2&#969;Vcoil)]&#189;= 35 mT, and shows that most of the RF power indeed drives the Al resonance and good sensitivity for detection can be expected, as well. For example, at 6.3 GPa, 1024 signals were accumulated to give satisfactorily spectra. With a pulse repetition time of approximately 50 ms, the total measurement time was only about 1 min&#160;per spectrum. The shifts were referenced to an aqueous AlCl3 sample.
<img alt="Figure 4" src="/files/ftp_upload/52243/52243fig4highres.jpg" /> Figure 4.&#160;27Al NMR on metallic aluminum powder: (A) acquired spectra up to 10.1 GPa; (B) the observed total line-widths (red squares) increased from about 77 ppm up to 145 ppm at 10.1 GPa; (C) recorded free induction decays at magnetic fields of 11.74 T (blue), 17.6 T (red) and the difference between both (green); (D) obtained spin echoes at elevated pressure for different pulse separation times. Reprinted Figure 1 from Meissner et al.23 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52243/52243fig4highres.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The most important result was an unexpected deviation of the Knight shift (1640 ppm at ambient pressure) from the free-electron behavior as the pressure increased. As subsequent band-structure calculations revealed this is due to a Lifshitz transition of the Fermi surface that was hitherto unknown. Additionally an unusual increase of the field-independent line-width at high pressures was discovered that could not be explained yet. It may be caused by a structurally forbidden quadrupole interaction, or it may signal onset of an indirect inter-nuclear magnetic dipole coupling due to the approaching van-Hove singularity. Alternatively pressure gradients may be behind this finding, but since different transmitting media give similar results and with the line-widths being field independent, only deviations from the cubic structure can explain the results.
This example shows that one can even learn important details about well-known systems, information that can be quantitatively tested subsequently leads to the calibration of state-of-the-art computation. For example, since only s-like electrons dominate the shift, we even learn about how they participate in changes at the Fermi surface.
The second set of experiments concerns 17O NMR of the high-temperature superconductor YBa2Cu4O8. These experiments were the driving force behind the development of high-sensitivity anvil cell NMR. The temperature-dependent NMR shifts are largely known for this and other superconductors, even for different doping levels. However, since these systems are yet not fully understood, one is interested in having another suitable parameter at hand that one can vary while investigating how it influences the NMR signals. Since it is known that the 17O NMR in these systems is dominated by the electronic spins (and no orbital effects), it lends itself for pressure-dependent studies. Here, anvil cells with 1 mm (2 to 3 GPa) and 0.8 mm (4.2 to 6.3 GPa) culet moissanite anvils were used. The dimensions of the micro-coils were similar to those used for the metal aluminum experiments described above. While the samples were enriched with 17O, such experiments on powder samples are still rather challenging. The measurements were carried out at magnetic fields of 11.75 T at temperatures from 85 K to RT. NMR signals were recorded by accumulating Hahn echoes28. By varying the RF pulse power, the &#960;/2- and &#960;-pulse durations were found to be 1.7 &#181;s and 3.4 &#181;s, respectively. The pulse separation was typically 30 &#181;s. At RT, the Q-factor was about 12. The B1-field was 25 mT at an average RF pulse power of 1 W, in good accordance with the predicted value (43 mT). Usual acquisition times were about 14 hr for one spectrum. This rather long measurement time is due to the relatively low Larmor frequency and the low number of resonant 17O nuclei in the powder sample. Again, these first experiments proved to provide very exciting results. This material (YBa2Cu4O8) was the &#8220;drosophila&#8221; for extensive NMR experiments, earlier. It is a stoichiometric material, but shows the pseudogap feature that is so characteristic for this class of materials, but it is not understood. By applying pressure, the temperature dependence of the shift changes significantly. The pseudogap feature disappears gradually as the pressure increases, similar to what happens if one increases the doping level for other systems. Furthermore, and quite unexpected, it was found that this happens by a change of two shift components: one of them decreases slightly (it has the temperature dependence of the ambient pressure signal), the second component that behaves like that of a metal is hardly visible at ambient pressure, but is tremendously amplified with pressure and dominates the shift at the highest pressure of 6.4 GPa.
<img alt="Figure 5" src="/files/ftp_upload/52243/52243fig5highres.jpg" /> 
Figure 5.&#160;17O NMR on YBa2Cu4O8 up to 6.4 GPa.&#160;Upper Panel: Observed 17O NMR spectrum at 6.3 GPa at 110 K. The observed line-width was about 1,500 ppm. Lower: recorded oxygen NMR spectra. Four distinct 17O signals could be identified (stemming from the planar, apex and chain oxygens) even at higher pressures at temperatures between 105 and 110 K. Reprinted Figure 2 with permission from Meissner et al.24 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52243/52243fig5highres.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
With such stunning results the authors decided to engage deeper into designing home-built high-sensitivity anvil cell devices.
II) 69,71Ga-NMR of liquid gallium at 1.8 GPa
In order to quantify the performance of the introduced moissanite anvil cells in more detail, liquid gallium was chosen as a test sample. The liquid gallium sample was obtained with a purity level of 5N. Loading of the micro-coil was achieved by liquifying a small piece of gallium and subsequently filling it into the micro-coil. For obtaining the data shown in this report, no isotopically enhanced sample were used; the natural abundance of the 69Ga and 71Ga isotopes was found to be sufficient.
The liquid state of gallium exists at elevated pressures up to 2 GPa. Therefore, very sensitive high-resolution measurement can be carried out on this system. Figure 6 shows some typical 69,71Ga-NMR spectra at RT and 1.8 GPa pressure. The measurements were carried out at a magnetic field of 11.74 T using an anvil cell equipped with two 800 &#181;m culet 6H-SiC Boehler-type anvils, and a 4-turn micro-coil of 200 &#181;m inner diameter made of 18 &#181;m diameter copper wire. The Q-factor was about 18 at 120.5 MHz and 150.3 MHz. The lengths of the &#960;/2 pulses were investigated at an average RF pulse power of about 150 mW, and were determined as 3 &#181;s and 2 &#181;s for 69Ga and 71Ga, respectively. The corresponding magnetic field amplitudes were found to be 28 mT and 25 mT in excellent agreement with the estimates. Experimentally, the signal-to-noise ratios were found to be SNR(69Ga) = 0.8 and SNR(71Ga) = 0.5 at a noise bandwidth of 1 MHz. Following the calculations of ref. 19, the expected SNR was calculated to be 1 and 1.2 for 69Ga and 71Ga, respectively. It was estimated that only 4.6&#8729;1016 and 3&#8729;1016 resonant nuclei for 69Ga and 71Ga contributed to the NMR signals (the filling factor of the micro-coil was approximately 50 %).
<img alt="Figure 6" src="/files/ftp_upload/52243/52243fig6highres.jpg" /> Figure 6.&#160;69Ga and 71Ga NMR of liquid gallium at 1.8 GPa.&#160;Recorded NMR spectra of both NMR active gallium nuclei (blue: 69Ga, red: 71Ga) at 1.8 GPa at RT (main frame). The resonance shift was obtained by comparing the signal frequencies with an aqueous Ga(NO3) solution. Left inset: obtained results from a nutation experiment of both nuclei at 150 mW average pulse power. Right inset: obtained data from a &#960; - &#960;/2 inversion recovery experiment. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52243/52243fig6highres.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The left inset of Figure 6 shows a typical result of a nutation experiment with varying pulse length. The right inset of Figure 6 shows the dependence of the observed signal intensities obtained in a &#960;-&#960;/2 inversion recovery experiment for increasing pulse separation times. Using a single exponential law, the spin-lattice relaxation rates R1 were determined to R169 = 1740 s-1 and R171 = 2020 s-1. All spectra were recorded at a magnetic field of 11.74 T and are accumulations of 500 scans. This leads to a total data acquisition time of only 3 s for a satisfactorily spectrum (the pulse repetition time (RT) was chosen to suffice the relationship: RT &#8805; 5/R1). A detailed analysis of this data will be given elsewhere.
<img alt="Figure S1" fo:content-width="3in" src="/files/ftp_upload/52243/52243supfig1highres.jpg" width="300" /> 
Supplementary Figure 1.&#160;Blueprints of the LAC-TM2 Piston. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52243/52243supfig1highres.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure S2" fo:content-width="3in" src="/files/ftp_upload/52243/52243supfig2highres.jpg" width="300" /> 
Supplementary Figure 2. Blueprints of the LAC-TM2 Shell. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52243/52243supfig2highres.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure S3" fo:content-width="3in" src="/files/ftp_upload/52243/52243supfig3highres.jpg" width="300" /> 
Supplementary Figure 3.&#160;Blueprints of the LAC-TM2 XY. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/52243/52243supfig3highres.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

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High-Sensitivity Nuclear Magnetic Resonance at Giga-Pascal Pressures: A New Tool for Probing Electronic and Chemical Properties of Condensed Matter under Extreme Conditions

Nuclear magnetic resonance is one of the most important spectroscopic tools. Here, the development of a new approach under high pressure, currently up to 10.1 GPa, is presented. This opens a new window into condensed matter physics and chemistry, where high-pressure research is of great importance.

Nuclear Magnetic Resonance (NMR) is one of the most important techniques for the study of condensed matter systems, their chemical structure, and their ...

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11.5K Views.  University of Leipzig. Nuclear magnetic resonance is one of the most important spectroscopic tools. Here, the development of a new approach under high pressure, currently up to 10.1 GPa, is presented. This opens a new window into condensed matter physics and chemistry, where high-pressure research is of great importance.

Video: High-Sensitivity Nuclear Magnetic Resonance at Giga-Pascal Pressures: A New Tool for Probing Electronic and Chemical Properties of Condensed Matter under Extreme Conditions

Probing and Mapping Electrode Surfaces in Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) are potentially the most efficient and cost-effective solution to utilization of a wide variety of fuels beyond hydrogen 1-7. The performance of SOFCs and the rates of many chemical and energy transformation processes in energy storage and conversion devices in general are limited primarily by charge and mass transfer along electrode surfaces and across interfaces. Unfortunately, the mechanistic understanding of these processes is still lacking, due largely to the difficulty of characterizing these processes under in situ conditions. This knowledge gap is a chief obstacle to SOFC commercialization. The development of tools for probing and mapping surface chemistries relevant to electrode reactions is vital to unraveling the mechanisms of surface processes and to achieving rational design of new electrode materials for more efficient energy storage and conversion2. Among the relatively few in situ surface analysis methods, Raman spectroscopy can be performed even with high temperatures and harsh atmospheres, making it ideal for characterizing chemical processes relevant to SOFC anode performance and degradation8-12. It can also be used alongside electrochemical measurements, potentially allowing direct correlation of electrochemistry to surface chemistry in an operating cell. Proper in situ Raman mapping measurements would be useful for pin-pointing important anode reaction mechanisms because of its sensitivity to the relevant species, including anode performance degradation through carbon deposition8, 10, 13, 14 ("coking") and sulfur poisoning11, 15 and the manner in which surface modifications stave off this degradation16. The current work demonstrates significant progress towards this capability. In addition, the family of scanning probe microscopy (SPM) techniques provides a special approach to interrogate the electrode surface with nanoscale resolution. Besides the surface topography that is routinely collected by AFM and STM, other properties such as local electronic states, ion diffusion coefficient and surface potential can also be investigated17-22. In this work, electrochemical measurements, Raman spectroscopy, and SPM were used in conjunction with a novel test electrode platform that consists of a Ni mesh electrode embedded in an yttria-stabilized zirconia (YSZ) electrolyte. Cell performance testing and impedance spectroscopy under fuel containing H2S was characterized, and Raman mapping was used to further elucidate the nature of sulfur poisoning. In situ Raman monitoring was used to investigate coking behavior. Finally, atomic force microscopy (AFM) and electrostatic force microscopy (EFM) were used to further visualize carbon deposition on the nanoscale. From this research, we desire to produce a more complete picture of the SOFC anode.

We present a unique platform for characterizing electrode surfaces in solid oxide fuel cells (SOFCs) that allows simultaneous performance of multiple characterization techniques (e.g. in situ Raman spectroscopy and scanning probe microscopy alongside electrochemical measurements). Complementary information from these analyses may help to advance toward a more profound understanding of electrode reaction and degradation mechanisms, providing insights into rational design of better materials for SOFCs.

Solid oxide fuel cells (SOFCs) are potentially the most efficient and cost-effective solution to utilization of a wide variety of fuels beyond hydrogen ...

Synthesis and Microdiffraction at Extreme Pressures and Temperatures

High pressure compounds and polymorphs are investigated for a broad range of purposes such as determine structures and processes of deep planetary interiors, design materials with novel properties, understand the mechanical behavior of materials exposed to very high stresses as in explosions or impacts. Synthesis and structural analysis of materials at extreme conditions of pressure and temperature entails remarkable technical challenges. In the laser heated diamond anvil cell (LH-DAC), very high pressure is generated between the tips of two opposing diamond anvils forced against each other; focused infrared laser beams, shined through the diamonds, allow to reach very high temperatures on samples absorbing the laser radiation. When the LH-DAC is installed in a synchrotron beamline that provides extremely brilliant x-ray radiation, the structure of materials under extreme conditions can be probed in situ. LH-DAC samples, although very small, can show highly variable grain size, phase and chemical composition. In order to obtain the high resolution structural analysis and the most comprehensive characterization of a sample, we collect diffraction data in 2D grids and combine powder, single crystal and multigrain diffraction techniques. Representative results obtained in the synthesis of a new iron oxide, Fe4O5 1 will be shown.

The laser heated diamond anvil cell combined with synchrotron micro-diffraction techniques allows researchers to explore the nature and properties of new phases of matter at extreme pressure and temperature (PT) conditions. Heterogeneous samples can be characterized in situ under high pressure by 2D mapping and combined powder, single-crystal and multigrain diffraction approaches.

High pressure compounds and polymorphs are investigated for a broad range of purposes such as determine structures and processes of deep planetary ...

Measuring Material Microstructure Under Flow Using 1-2 Plane Flow-Small Angle Neutron Scattering

A new small-angle neutron scattering (SANS) sample environment optimized for studying the microstructure of complex fluids under simple shear flow is presented. The SANS shear cell consists of a concentric cylinder Couette geometry that is sealed and rotating about a horizontal axis so that the vorticity direction of the flow field is aligned with the neutron beam enabling scattering from the 1-2 plane of shear (velocity-velocity gradient, respectively). This approach is an advance over previous shear cell sample environments as there is a strong coupling between the bulk rheology and microstructural features in the 1-2 plane of shear. Flow-instabilities, such as shear banding, can also be studied by spatially resolved measurements. This is accomplished in this sample environment by using a narrow aperture for the neutron beam and scanning along the velocity gradient direction. Time resolved experiments, such as flow start-ups and large amplitude oscillatory shear flow are also possible by synchronization of the shear motion and time-resolved detection of scattered neutrons. Representative results using the methods outlined here demonstrate the useful nature of spatial resolution for measuring the microstructure of a wormlike micelle solution that exhibits shear banding, a phenomenon that can only be investigated by resolving the structure along the velocity gradient direction. Finally, potential improvements to the current design are discussed along with suggestions for supplementary experiments as motivation for future experiments on a broad range of complex fluids in a variety of shear motions.

A shear cell is developed for small-angle neutron scattering measurements in the velocity-velocity gradient plane of shear and is used to characterize complex fluids. Spatially resolved measurements in the velocity gradient direction are possible for studying shear-banding materials. Applications include investigations of colloidal dispersions, polymer solutions, and self-assembled structures.

A new small-angle neutron scattering (SANS) sample environment optimized for studying the microstructure of complex fluids under simple shear flow is ...

Flame Experiments at the Advanced Light Source: New Insights into Soot Formation Processes

The following experimental protocols and the accompanying video are concerned with the flame experiments that are performed at the Chemical Dynamics Beamline of the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory1-4. This video demonstrates how the complex chemical structures of laboratory-based model flames are analyzed using flame-sampling mass spectrometry with tunable synchrotron-generated vacuum-ultraviolet (VUV) radiation. This experimental approach combines isomer-resolving capabilities with high sensitivity and a large dynamic range5,6. The first part of the video describes experiments involving burner-stabilized, reduced-pressure (20-80 mbar) laminar premixed flames. A small hydrocarbon fuel was used for the selected flame to demonstrate the general experimental approach. It is shown how species&#8217; profiles are acquired as a function of distance from the burner surface and how the tunability of the VUV photon energy is used advantageously to identify many combustion intermediates based on their ionization energies. For example, this technique has been used to study gas-phase aspects of the soot-formation processes, and the video shows how the resonance-stabilized radicals, such as C3H3, C3H5, and i-C4H5, are identified as important intermediates7. The work has been focused on soot formation processes, and, from the chemical point of view, this process is very intriguing because chemical structures containing millions of carbon atoms are assembled from a fuel molecule possessing only a few carbon atoms in just milliseconds. The second part of the video highlights a new experiment, in which an opposed-flow diffusion flame and synchrotron-based aerosol mass spectrometry are used to study the chemical composition of the combustion-generated soot particles4. The experimental results indicate that the widely accepted H-abstraction-C2H2-addition (HACA) mechanism is not the sole molecular growth process responsible for the formation of the observed large polycyclic aromatic hydrocarbons (PAHs).

Gas sampling from laboratory-scale flames with online analysis of all species by mass spectrometry is a powerful method to investigate the complex mixture of chemical compounds occurring during combustion processes. Coupled with tunable soft ionization via synchrotron-generated vacuum-ultraviolet radiation, this technique provides isomer-resolved information and potentially fragment-free mass spectra.

The following experimental protocols and the accompanying video are concerned with the flame experiments that are performed at the Chemical Dynamics ...

In Situ Neutron Powder Diffraction Using Custom-made Lithium-ion Batteries

Li-ion batteries are widely used in portable electronic devices and are considered as promising candidates for higher-energy applications such as electric vehicles.1,2 However, many challenges, such as energy density and battery lifetimes, need to be overcome before this particular battery technology can be widely implemented in such applications.3 This research is challenging, and we outline a method to address these challenges using in situ NPD to probe the crystal structure of electrodes undergoing electrochemical cycling (charge/discharge) in a battery. NPD data help determine the underlying structural mechanism responsible for a range of electrode properties, and this information can direct the development of better electrodes and batteries.
We briefly review six types of battery designs custom-made for NPD experiments and detail the method to construct the &#8216;roll-over&#8217; cell that we have successfully used on the high-intensity NPD instrument, WOMBAT, at the Australian Nuclear Science and Technology Organisation (ANSTO). The design considerations and materials used for cell construction are discussed in conjunction with aspects of the actual in situ NPD experiment and initial directions are presented on how to analyze such complex in situ data.

In Situ Neutron Powder Diffraction Using Custom-made Lithium-ion Batteries

We describe the design and construction of an electrochemical cell for the examination of electrode materials using in situ neutron powder diffraction (NPD). We briefly comment on alternate in situ NPD cell designs and discuss methods for the analysis of the corresponding in situ NPD data produced using this cell.

Li-ion batteries are widely used in portable electronic devices and are considered as promising candidates for higher-energy applications such as electric ...

Resonance Raman Spectroscopy of Extreme Nanowires and Other 1D Systems

This paper briefly describes how nanowires with diameters corresponding to 1 to 5 atoms can be produced by melting a range of inorganic solids in the presence of carbon nanotubes. These nanowires are extreme in the sense that they are the limit of miniaturization of nanowires and their behavior is not always a simple extrapolation of the behavior of larger nanowires as their diameter decreases. The paper then describes the methods required to obtain Raman spectra from extreme nanowires and the fact that due to the van Hove singularities that 1D systems exhibit in their optical density of states, that determining the correct choice of photon excitation energy is critical. It describes the techniques required to determine the photon energy dependence of the resonances observed in Raman spectroscopy of 1D systems and in particular how to obtain measurements of Raman cross-sections with better than 8% noise and measure the variation in the resonance as a function of sample temperature. The paper describes the importance of ensuring that the Raman scattering is linearly proportional to the intensity of the laser excitation intensity. It also describes how to use the polarization dependence of the Raman scattering to separate Raman scattering of the encapsulated 1D systems from those of other extraneous components in any sample.

The paper describes a method for producing extreme nanowires by melt infiltration into carbon nanotubes and how 1D systems may be characterized and investigated using Resonance Raman Spectroscopy to determine vibrational and optical excitation energies.

This paper briefly describes how nanowires with diameters corresponding to 1 to 5 atoms can be produced by melting a range of inorganic solids in the ...

In Situ Visualization of the Phase Behavior of Oil Samples Under Refinery Process Conditions

To help address production issues in refineries caused by the fouling of process units and lines, we have developed a setup as well as a method to visualize the behavior of petroleum samples under process conditions. The experimental setup relies on a custom-built micro-reactor fitted with a sapphire window at the bottom, which is placed over the objective of an inverted microscope equipped with a cross-polarizer module. Using reflection microscopy enables the visualization of opaque samples, such as petroleum vacuum residues, or asphaltenes. The combination of the sapphire window from the micro-reactor with the cross-polarizer module of the microscope on the light path allows high-contrast imaging of isotropic and anisotropic media. While observations are carried out, the micro-reactor can be heated to the temperature range of cracking reactions (up to 450 &#176;C), can be subjected to H2 pressure relevant to hydroconversion reactions (up to 16 MPa), and can stir the sample by magnetic coupling. 
Observations are typically carried out by taking snapshots of the sample under cross-polarized light at regular time intervals. Image analyses may not only provide information on the temperature, pressure, and reactive conditions yielding phase separation, but may also give an estimate of the evolution of the chemical (absorption/reflection spectra) and physical (refractive index) properties of the sample before the onset of phase separation.

In Situ Visualization of the Phase Behavior of Oil Samples Under Refinery Process Conditions

This article describes a setup and method for the in situ visualization of oil samples under a variety of temperature and pressure conditions that aim to emulate refining and upgrading processes. It is primarily used for studying isotropic and anisotropic media involved in the fouling behavior of petroleum feeds.

To help address production issues in refineries caused by the fouling of process units and lines, we have developed a setup as well as a method to ...

A Novel Biaxial Testing Apparatus for the Determination of Forming Limit under Hot Stamping Conditions

The hot stamping and cold die quenching process is increasingly used to form complex shaped structural components of sheet metals. Conventional experimental approaches, such as out-of-plane and in-plane tests, are not applicable to the determination of forming limits when heating and rapid cooling processes are introduced prior to forming for tests conducted under hot stamping conditions. A novel in-plane biaxial testing system was designed and used for the determination of forming limits of sheet metals at various strain paths, temperatures, and strain rates after heating and cooling processes in a resistance heating uniaxial testing machine. The core part of the biaxial testing system is a biaxial apparatus, which transfers a uniaxial force provided by the uniaxial testing machine to a biaxial force. One type of cruciform specimen was designed and verified for the formability test of aluminum alloy 6082 using the proposed biaxial testing system. The digital image correlation (DIC) system with a high-speed camera was used for taking strain measurements of a specimen during a deformation. The aim of proposing this biaxial testing system is to enable the forming limits of an alloy to be determined at various temperatures and strain rates under hot stamping conditions.

This protocol proposes a novel biaxial testing system used on a resistance heating uniaxial tensile test machine in order to determine the forming limit diagram (FLD) of sheet metals under hot stamping conditions.

The hot stamping and cold die quenching process is increasingly used to form complex shaped structural components of sheet metals. Conventional ...

Orientational Transition in a Liquid Crystal Triggered by the Thermodynamic Growth of Interfacial Wetting Sheets

In liquid crystal (LC) physical chemistry, molecules near the surface play a great role in controlling bulk orientation. Thus far, mainly to achieve desired molecular orientation states in LC displays, the "static" surface property of LCs, so-called surface anchoring, has been intensively studied. As a rule of thumb, once the initial orientation of LCs is "locked" by specific surface treatments, such as rubbing or treatment with a specific alignment layer, it hardly changes with temperature. Here, we present a system exhibiting an orientational transition upon temperature variation, which conflicts with the consensus. Right on the transition, the bulk LC molecules experience the orientational rotation, with 90&#176; between the planar (P) orientation at high temperatures and the vertical (V) orientation at low temperatures in the first-order transitional manner. We have tracked thermodynamic surface anchoring behavior by means of polarizing optical microscopy (POM), dielectric spectroscopy (DS), high-resolution differential scanning calorimetry (HR-DSC), and grazing incidence X-ray diffraction (GI-XRD) and reached a plausible physical explanation: that the transition is triggered by a growth of surface wetting sheets, which impose the V orientation locally against the P orientation in the bulk. This landscape would provide a general link explaining how the equilibrium bulk orientation is affected by surface-localized orientation in many LC systems. In our characterization, POM and DS are advantageous by offering information on the spatial distribution of the orientation of LC molecules. HR-DSC gives information about the precise thermodynamic information on transitions, which cannot be addressed by conventional DSC instruments due to limited resolution. GI-XRD provides information on surface-specific molecular orientation and short-range orderings. The goal of this paper is to present a protocol for preparing a sample that exhibits the transition and to demonstrate how the thermodynamic structural variation, both in the bulk and on surfaces, can be analyzed through the abovementioned methods.

Here, we present a protocol to trigger an orientational transition of a liquid crystal in response to temperature. Methodologies are described for preparing a sample in order to observe the transition and the detailed transitional evolution.

In liquid crystal (LC) physical chemistry, molecules near the surface play a great role in controlling bulk orientation. Thus far, mainly to achieve ...

All-electronic Nanosecond-resolved Scanning Tunneling Microscopy: Facilitating the Investigation of Single Dopant Charge Dynamics

The miniaturization of semiconductor devices to scales where small numbers of dopants can control device properties requires the development of new techniques capable of characterizing their dynamics. Investigating single dopants requires sub-nanometer spatial resolution, which motivates the use of scanning tunneling microscopy (STM). However, conventional STM is limited to millisecond temporal resolution. Several methods have been developed to overcome this shortcoming, including all-electronic time-resolved STM, which is used in this study to examine dopant dynamics in silicon with nanosecond resolution. The methods presented here are widely accessible and allow for local measurement of a wide variety of dynamics at the atomic scale. A novel time-resolved scanning tunneling spectroscopy technique is presented and used to efficiently search for dynamics.

We demonstrate an all-electronic method to observe nanosecond-resolved charge dynamics of dopant atoms in silicon with a scanning tunneling microscope.

The miniaturization of semiconductor devices to scales where small numbers of dopants can control device properties requires the development of new ...