Name: methods of ex situ and in situ investigations of structural transformations: the case of crystallization of metallic glasses
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This work was supported by the Slovak Research and Development Agency under the contracts No. APVV-16-0079 and APVV-15-0621, grants VEGA 1/0182/16 and VEGA 2/0082/17, and the internal IGA grant of Palack&#253; University (IGA_PrF_2018_002). We are grateful to R. R&#252;ffer (ESRF, Grenoble) for assistance with the synchrotron experiments.

1. Preparation of a MG
NOTE: To demonstrate a broad range of diagnostic capabilities of NFS in combination with M&#246;ssbauer spectrometry, an appropriate MG composition was designed, namely (Fe3Co1)76Mo8Cu1B15 (at.%). This system shows the magnetic transition from the ferromagnetic to paramagnetic state below the onset of crystallization. Moreover, crystallites that emerge during the first crystallization step form bcc-Fe,Co pha...

<ol>
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Ex situ M&#246;ssbauer effect experiments describe a steady situation which is encountered in the investigated MG after the applied heat treatment. Each spectrum was collected for a duration of several hours at room temperature. Thus, the evolution of the originally amorphous structure was followed as a function of annealing conditions. Because M&#246;ssbauer spectrometry is sensitive to hyperfine interactions acting upon the resonant nuclei, faint details of structural and/or magnetic modifications induced by e...

Iron-based MGs prepared by rapid quenching of a melt represent industrially attractive materials with numerous practical applications1. Especially since their magnetic properties are often superior to conventional (poly)crystalline alloys2,3. To better benefit from their advantageous parameters, their response to elevated temperatures should be known. With increasing temperature, the amorphous structure relaxes and, finally, the crystallization starts. In some types of MGs, this can lead to the deterioration of their magnetic parameters and, consequently, poorer performance. There are, however, several families of iron-based MGs with special compositions4,5,6,7 in which the newly formed crystalline grains are very fine, typically below about 30 nm in size. The nanocrystals stabilize the structure and thus, preserve acceptable magnetic parameters over a wide temperature range8,9. These are the so-called nanocrystalline alloys (NCA).
The long-term performance reliability of MGs, especially under elevated temperatures and/or tough conditions (ionizing radiation, corrosion, etc.) demands thorough knowledge of their behavior and individual physical parameters. Because MGs are amorphous, the assortment of analytical techniques that are suitable for their characterization is rather limited. For example, diffraction methods provide broad and featureless reflections that can be used only for the verification of amorphicity.
It is noteworthy that several, usually indirect methods exist that provide fast and non-destructive characterization of MGs (e.g., magnetostrictive delay line sensing principle). This method provides fast characterization of structural and stress states including the presence of inhomogeneities. It was advantageously applied to fast and non-destructive characterization along the whole length of MG ribbons10,11.
More detailed insight into disordered structural arrangement can be achieved via hyperfine interactions that sensitively reflect the local atomic arrangement of the resonant atoms. Moreover, variations in topological and chemical short-range order can be revealed. In this respect, the methods like nuclear magnetic resonance (NMR) spectrometry and/or M&#246;ssbauer spectrometry, both performed on 57Fe nuclei, should be considered12,13. While the former method provides response exclusively to magnetic dipole hyperfine interactions, the latter is sensitive also to the electric quadrupole interactions. Thus, M&#246;ssbauer spectrometry makes simultaneously available information on both the structural arrangement and magnetic states of the resonant iron nuclei14.
Nevertheless, to achieve reasonable statistics, the acquisition of a M&#246;ssbauer spectrum usually takes several hours. This restriction should be considered especially when temperature-dependent experiments are envisaged. Elevated temperature that is applied during the experiment causes structural modifications in the investigated MGs15. Consequently, only ex situ experiments performed at room temperature upon samples that were first annealed at certain temperature and then returned to ambient conditions provide reliable results.
The evolution of MG structures during heat treatment is routinely studied by analytical techniques which enable rapid data acquisition as for example X-ray diffraction of synchrotron radiation (DSR), differential scanning calorimetry (DSC), or magnetic measurements. Though in situ experiments are possible, the obtained information concerns either structural (DSR, DSC) or magnetic (magnetic data) features. However, in the case of DSC (and magnetic measurements) the identification of the type of (nano)grains that emerge during the crystallization is not possible. On the other hand, DSR data do not indicate the magnetic states of the investigated system. A solution to this situation is a technique that makes use of hyperfine interactions: NFS of synchrotron radiation16. It belongs to a group of methods that exploits nuclear resonant scattering processes17. Due to extremely high brilliance of radiation obtained from the third generation of synchrotrons, temperature NFS experiments under in situ conditions became feasible18,19,20,21,22,23.
Both M&#246;ssbauer spectrometry and NFS are governed by the same physical principles related to nuclear resonance among energy levels of 57Fe nuclei. Nevertheless, while the former scans hyperfine interactions in the energy domain, the latter provides interferograms in the time domain. In this way, the results obtained from both methods are equivalent and complementary. To evaluate the NFS data, a reasonable physical model must be established. This challenging task can be accomplished by the help of M&#246;ssbauer spectrometry which provides the first estimate. Complementarity between these two methods means that in situ NFS inspects transient states and M&#246;ssbauer spectrometry reflects the stable states, viz. the initial and/or the final state of a material studied ex situ.
This article describes in detail selected applications of these two less common methods of nuclear resonances: here, we apply them to the investigation of structural modifications that occur in a (Fe2.85Co1)77Mo8Cu1B14 MG exposed to heat treatment. We hope that this article attracts the interest of researchers to use these techniques for the investigation of similar phenomena and eventually with different types of materials.

<table border="0" cellpadding="0" cellspacing="0" width="728">
	<tbody>
		<tr height="30">
			<td height="30" style="height:30px;width:216px;">stable isotope, 57Fe</td>
			<td style="width:147px;">Isoflex USA</td>
			<td style="width:119px;">iron-57</td>
			<td style="width:247px;">metallic form</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">standard eletrolytic Fe, 99.95 %</td>
			<td style="width:147px;">Sigma Aldrich (Merck)</td>
			<td style="width:119px;">1.03819</td>
			<td>fine powder</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">electrolytic Co, 99.85 %</td>
			<td style="width:147px;">Sigma Aldrich (Merck)</td>
			<td style="width:119px;">1.12211</td>
			<td>fine powder</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">electrolytic Cu, 99.8 %</td>
			<td style="width:147px;">Sigma Aldrich (Merck)</td>
			<td style="width:119px;">1.02703</td>
			<td>fine powder</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">electrolytic Mo, 99.95 %</td>
			<td style="width:147px;">Sigma Aldrich (Merck)</td>
			<td style="width:119px;">1.12254</td>
			<td>fine powder</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">crystalline B, 99.95 %</td>
			<td style="width:147px;">Sigma Aldrich (Merck)</td>
			<td style="width:119px;">266620</td>
			<td>crystalline</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">calibration foil for M&#246;ssbauer spectrometry, bcc-Fe</td>
			<td style="width:147px;">GoodFellow</td>
			<td style="width:119px;">564-385-23</td>
			<td>foil 0.0125 mm, purity 99.85 %</td>
		</tr>
		<tr height="44">
			<td height="44" style="height:44px;width:216px;">HNO3 acid, ANALPURE Ultra</td>
			<td style="width:147px;">Analytika Praha, Czech Republic</td>
			<td style="width:119px;">UAc0061a</td>
			<td>concentration 67 %, volume 500 mL</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">spectrometer for atomic absorption spectrometry</td>
			<td style="width:147px;">Perkin Elmer 1100, Germany</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">spectrometer for optical emmission spectrometry with inductively coupled plasma</td>
			<td style="width:147px;">Jobin Yvon 70 Plus, France</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">X-ray diffractometer</td>
			<td style="width:147px;">Bruker D8 Advance, USA</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">differential scanning calorimeter</td>
			<td style="width:147px;">Perkin Elmer DSC 7, Germany</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
	</tbody>
</table>

methods of ex situ and in situ investigations of structural transformations: the case of crystallization of metallic glasses

We demonstrate the use of two nuclear-based analytical methods that can follow the modifications of microstructural arrangement of iron-based metallic glasses (MGs). Despite their amorphous nature, the identification of hyperfine interactions unveils faint structural modifications. For this purpose, we have employed two techniques that utilize nuclear resonance among nuclear levels of a stable 57Fe isotope, namely M&#246;ssbauer spectrometry and nuclear forward scattering (NFS) of synchrotron radiation. The effects of heat treatment upon (Fe2.85Co1)77Mo8Cu1B14 MG are discussed using the results of ex situ and in situ experiments, respectively. As both methods are sensitive to hyperfine interactions, information on structural arrangement as well as on magnetic microstructure is readily available. M&#246;ssbauer spectrometry performed ex situ describes how the structural arrangement and magnetic microstructure appears at room temperature after the annealing under certain conditions (temperature, time), and thus this technique inspects steady states. On the other hand, NFS data are recorded in situ during dynamically changing temperature and NFS examines transient states. The use of both techniques provides complementary information. In general, they can be applied to any suitable system in which it is important to know its steady state but also transient states.

The XRD pattern in Figure 2 exhibits broad featureless diffraction peaks. The observed reflections demonstrate that the produced ribbon of the (Fe2.85Co1)77Mo8Cu1B14 MG is XRD amorphous.
Due to its sensitivity, XRD has some limitations in unveiling surface crystallization. The presence of crystallites amounting to less than about 2-3%...

Watch this Scientific Journal Video about Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses at JoVE.com

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

Here, we present a protocol to describe ex situ and in situ investigations of structural transformations in metallic glasses. We employed nuclear-based analytical methods which inspect hyperfine interactions. We demonstrate the applicability of M&#246;ssbauer spectrometry and nuclear forward scattering of synchrotron radiation during temperature-driven experiments.

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

We demonstrate the use of two nuclear-based analytical methods that can follow the modifications of microstructural arrangement of iron-based metallic ...

This method can help answer key questions on the evolution of crystallization in iron-based metallic glasses with respect to varying time and/or temperature. The main advantage of this procedure is the use of two complementary nuclear-based analytical methods that can follow structural and magnetic transformations through hyperfine interactions. Mossbauer spectroscopy performed ex situ describes how the structural arrangement and magnetic microstructure appears after annealing at certain temperature and time, so it reflects a static situation.The method of nuclear forward scattering of synchrotron radiation provides data which are recorded in situ during dynamically changing temperature and thus inspects transient states. Demonstrating the procedure will be Dr.Irena Janatova, a junior research fellow from our laboratory. First cast a previously-prepared melt upon the rotating quenching wheel of an apparatus for planar flow casting under ambient conditions.Check the amorphous nature of the produced ribbons by performing X-ray diffraction in Bragg-Brentano geometry. Use a copper anode and record the diffraction pattern from 20 to 100 degrees of 2-theta with an angular step of 0.05 degrees and acquisition of 20 seconds for one point. Next prepare small pieces of the produced ribbons with a total mass of about three to five milligrams and place them into a DSC instrument.Perform the DSC experiment with a temperature ramp of 10 Kelvin per minute at a temperature range of 50 to 700 degrees Celsius under argon atmosphere. Determine the temperature of the onset of crystallization, which is taken at the kink of the most pronounced peak on the DSC curve. Choose five temperatures of annealing that cover both the pre-crystallization and crystallization regions on the DSC for further ex situ annealing.Following this, prepare five groups of seven-centimeter long pieces of the as-quenched ribbon. For ex situ annealing, set the destination temperature on a furnace and wait for 15 minutes for its stabilization. Following this, insert pieces of the ribbon into the evacuated and thermally-stabilized zone by opening a seven to 10-millimeter gap between the two blocks and sliding the ribbons directly into the center of the heated zone.Close the gap immediately so that the temperature of the sample achieves the furnace temperature in less than five seconds within a 0.1 Kelvin difference. After annealing, remove the heated ribbons and place them on a cold substrate inside the vacuum system to ensure fast cooling of the samples to room temperature. Prepare six to eight pieces of one-centimeter long ribbons for each sample for Mossbauer spectrometry experiments.Assemble the ribbons side-by-side using adhesive tape over the ends of the ribbons. Attach them to an aluminum holder to form a compact area of about one by one centimeters squared. Note the different appearance of both sides of the ribbons.Be sure that all ribbons are positioned on the aluminum holder with the same side upwards. Next insert the aluminum holder with the sample into the detector of the instrument. Prior to the measurement, thoroughly wash the inner detector volume with a stream of the detection gas for 10 to 15 minutes to expel all residual air.After washing, adjust the gas flow through the detector by a needle valve to three milliliters per minute. Next connect a high voltage to the detector. Record the CEMS and CXMS Mossbauer spectra using a constant acceleration spectrometer equipped with a Cobalt 57 radioactive source embedded in a rhodium matrix.Operate the spectrometer with a gas detector at room temperature according to the manual. For NFS experiments, place an approximately six-millimeter long ribbon of the investigated metallic glass in a vacuum furnace. Following this, record the NFS time-domain patterns during continuous heating of the sample to a temperature of up to 700 degrees Celsius with a ramp of 10 degrees per minute, using one-minute time intervals for acquisition of experimental data during the entire in situ annealing process.Finally, evaluate the NFS experimental data using suitable software. Mossbauer spectrometry allows direct identification of the type of structural arrangement, specifically crystalline versus amorphous as shown here. CEMS spectra taken from the air and wheel sides of the ribbons are displayed here.They show increasing contribution of the crystalline components after ex situ annealing. Comparison of the amounts of crystallites from CEMS and CXMS techniques is shown here. The crystallization starts after annealing at 410 degrees Celsius.NFS patterns that contain in time domain the same information on hyperfine interactions as Mossbauer spectra in energy domain but are recorded over a shorter time are shown here. The contour plot of NFS time domain patterns recorded during in situ heating of as-quenched ribbons is shown here. It exhibits a magnetic transition at the Curie temperature and the onset of crystallization.Examples of NFS patterns are shown here. The evolution of the total relative amount of nanocrystals with temperature is shown here. The onset of crystallization is marked with TX1.Total number of counts of the individual NFS time domain patterns with respect to the temperature of the in situ NFS experiment show three well distinguished regions that evolve during dynamically changing temperature. Mossbauer spectrometry unveils fine details of structural and/or magnetic transformations induced by heat treatment. However, the time needed for recording one spectrum can extend over several hours, which limits this technique to ex situ experiments.Using ex situ Mossbauer experiments, we can investigate the local structure and magnetic arrangement in a material under static conditions. These can be inspected before and/or after temperature treatment. Following the procedure of nuclear forward scattering, rapid data acquisition is ensured by extremely brilliant synchrotron radiation.Thus, in situ experiments can be performed during temperature treatment and immediate states of a material can be inspected under dynamic conditions. After watching this video, you should have a good understanding of benefits of the in situ nuclear forward scattering technique of synchrotron radiation. It is complementary with ex situ Mossbauer spectroscopy from the viewpoint of the obtained results and conditions under which they are achieved.These techniques pave the way for researchers in other fields that are associated with structural and/or magnetic transitions, especially when existence of intermediate states is foreseen.

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In-situ Tapering of Chalcogenide Fiber for Mid-infrared Supercontinuum Generation

Supercontinuum generation (SCG) in a tapered chalcogenide fiber is desirable for broadening mid-infrared (or mid-IR, roughly the 2-20 &mu;m wavelength range) frequency combs1, 2 for applications such as molecular fingerprinting, 3 trace gas detection, 4 laser-driven particle acceleration, 5 and x-ray production via high harmonic generation. 6 Achieving efficient SCG in a tapered optical fiber requires precise control of the group velocity dispersion (GVD) and the temporal properties of the optical pulses at the beginning of the fiber, 7 which depend strongly on the geometry of the taper. 8 Due to variations in the tapering setup and procedure for successive SCG experiments-such as fiber length, tapering environment temperature, or power coupled into the fiber, in-situ spectral monitoring of the SCG is necessary to optimize the output spectrum for a single experiment.
	In-situ fiber tapering for SCG consists of coupling the pump source through the fiber to be tapered to a spectral measurement device. The fiber is then tapered while the spectral measurement signal is observed in real-time. When the signal reaches its peak, the tapering is stopped. The in-situ tapering procedure allows for generation of a stable, octave-spanning, mid-IR frequency comb from the sub harmonic of a commercially available near-IR frequency comb. 9 This method lowers cost due to the reduction in time and materials required to fabricate an optimal taper with a waist length of only 2 mm.
	The in-situ tapering technique can be extended to optimizing microstructured optical fiber (MOF) for SCG10 or tuning of the passband of MOFs, 11 optimizing tapered fiber pairs for fused fiber couplers12 and wavelength division multiplexers (WDMs), 13 or modifying dispersion compensation for compression or stretching of optical pulses.14-16

In-situ Tapering of Chalcogenide Fiber for Mid-infrared Supercontinuum Generation

We describe a method for in-situ tapering of As2S3 fibers to achieve efficient mid-infrared supercontinuum generation. By tapering while monitoring the supercontinuum&#x2019;s spectrum, the spectral width can be maximized for a fiber taper. In-situ fiber tapering can be applied to optimize the performance of other fiber-based devices.

Supercontinuum  generation (SCG) in a tapered chalcogenide fiber is desirable for broadening mid-infrared  (or mid-IR, roughly the 2-20 &mu;m wavelength ...

Printing Fabrication of Bulk Heterojunction Solar Cells and In Situ Morphology Characterization

Polymer-based materials hold promise as low-cost, flexible efficient photovoltaic devices. Most laboratory efforts to achieve high performance devices have used devices prepared by spin coating, a process that is not amenable to large-scale fabrication. This mismatch in device fabrication makes it difficult to translate quantitative results obtained in the laboratory to the commercial level, making optimization difficult. Using a mini-slot die coater, this mismatch can be resolved by translating the commercial process to the laboratory and characterizing the structure formation in the active layer of the device in real time and in situ as films are coated onto a substrate. The evolution of the morphology was characterized under different conditions, allowing us to propose a mechanism by which the structures form and grow. This mini-slot die coater offers a simple, convenient, material efficient route by which the morphology in the active layer can be optimized under industrially relevant conditions. The goal of this protocol is to show experimental details of how a solar cell device is fabricated using a mini-slot die coater and technical details of running in situ structure characterization using the mini-slot die coater.

Printing Fabrication of Bulk Heterojunction Solar Cells and In Situ Morphology Characterization

Here, we present a protocol to fabricate organic thin film solar cells using a mini-slot die coater and related in-line structure characterizations using synchrotron scattering techniques.

Polymer-based materials hold promise as low-cost, flexible efficient photovoltaic devices. Most laboratory efforts to achieve high performance devices ...

In Situ Synthesis of Gold Nanoparticles without Aggregation in the Interlayer Space of Layered Titanate Transparent Films

Combinations of metal oxide semiconductors and gold nanoparticles (AuNPs) have been investigated as new types of materials. The in situ synthesis of AuNPs within the interlayer space of semiconducting layered titania nanosheet (TNS) films was investigated here. Two types of intermediate films (i.e., TNS films containing methyl viologen (TNS/MV2+) and 2-ammoniumethanethiol (TNS/2-AET+)) were prepared. The two intermediate films were soaked in an aqueous tetrachloroauric(III) acid (HAuCl4) solution, whereby considerable amounts of Au(III) species were accommodated within the interlayer spaces of the TNS films. The two types of obtained films were then soaked in an aqueous sodium tetrahydroborate (NaBH4) solution, whereupon the color of the films immediately changed from colorless to purple, suggesting the formation of AuNPs within the TNS interlayer. When only TNS/MV2+ was used as the intermediate film, the color of the film gradually changed from metallic purple to dusty purple within 30 min, suggesting that aggregation of AuNPs had occurred. In contrast, this color change was suppressed by using the TNS/2-AET+ intermediate film, and the AuNPs were stabilized for over 4 months, as evidenced by the characteristic extinction (absorption and scattering) band from the AuNPs.

In Situ Synthesis of Gold Nanoparticles without Aggregation in the Interlayer Space of Layered Titanate Transparent Films

Here, we present a protocol for the in situ synthesis of gold nanoparticles (AuNPs) within the interlayer space of layered titanate films without the aggregation of AuNPs. No spectral change was observed even after 4 months. The synthesized material has expected applications in catalysis, photo-catalysis, and the development of cost-effective plasmonic devices.

Combinations of metal oxide semiconductors and gold nanoparticles (AuNPs) have been investigated as new types of materials. The in situ synthesis of AuNPs ...

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 ...

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia (YSZ) Scaffolds by In Situ Carbon Templating Xerogels

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) scaffolds with tunable specific surface areas up to 80 m2&#183;g-1. An aqueous solution of a zirconium salt, yttrium salt, and glucose is mixed with propylene oxide (PO) to form a gel. The gel is dried under ambient conditions to form a xerogel. The xerogel is pressed into pellets and then sintered in an argon atmosphere. During sintering, a YSZ ceramic phase forms and the organic components decompose, leaving behind amorphous carbon. The carbon formed in situ serves as a hard template, preserving a high surface area YSZ nanomorphology at sintering temperature. The carbon is subsequently removed by oxidation in air at low temperature, resulting in a porous, nanostructured YSZ scaffold. The concentration of the carbon template and the final scaffold surface area can be systematically tuned by varying the glucose concentration in the gel synthesis. The carbon template concentration was quantified using thermogravimetric analysis (TGA), the surface area and pore size distribution was determined by physical adsorption measurements, and the morphology was characterized using scanning electron microscopy (SEM). Phase purity and crystallite size was determined using X-ray diffraction (XRD). This fabrication approach provides a novel, flexible platform for realizing unprecedented scaffold surface areas and nanomorphologies for ceramic-based electrochemical energy conversion applications, e.g. solid oxide fuel cell (SOFC) electrodes.

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia YSZ Scaffolds by In Situ Carbon Templating Xerogels

A protocol for fabricating porous, nanostructured yttria-stabilized-zirconia (YSZ) scaffolds at temperatures between 1,000 &#176;C and 1,400 &#176;C is presented.

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) ...

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and forging. Adoption of this technique is proceeding despite disagreement concerning the underlying mechanism responsible for EAD. The experimental procedure described herein enables a more explicit study compared to previous EAD research by removing thermal effects, which are responsible for disagreement in interpreting previous EAD results. Furthermore, as the procedure described here enables EAD observation in situ and in real time in a transmission electron microscope (TEM), it is superior to existing post-mortem methods that observe EAD effects post-test. Test samples consist of a single crystal copper (SCC) foil having a free-standing tensile test section of nanoscale thickness, fabricated using a combination of laser and ion beam milling. The SCC is mounted to an etched silicon base that provides mechanical support and electrical isolation while serving as a heat sink. Using this geometry, even at high current density (~3,500 A/mm2), the test section experiences a negligible temperature increase (&#60;0.02 &#176;C), thus eliminating Joule heating effects. Monitoring material deformation and identifying the corresponding changes to microstructures, e.g. dislocations, are accomplished by acquiring and analyzing a series of TEM images. Our sample preparation and in situ experiment procedures are robust and versatile as they can be readily utilized to test materials with different microstructures, e.g., single and polycrystalline copper.

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Isolating electrical and thermal effects on electrically assisted deformation (EAD) is very difficult using macroscopic samples. Metallic sample micro- and nanostructures together with a custom test procedure have been developed to evaluate the impact of applied current on the formation without joule heating and evolution of dislocations on these samples.

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and ...

Measuring the Densities of Aqueous Glasses at Cryogenic Temperatures

We demonstrate a method for determining the vitreous phase cryogenic temperature densities of aqueous mixtures, and other samples that require rapid cooling, to prepare the desired cryogenic temperature phase. Microliter to picoliter size drops are cooled by projection into a liquid nitrogen-argon (N2-Ar) mixture. The cryogenic temperature phase of the drop is evaluated using a visual assay that correlates with X-ray diffraction measurements. The density of the liquid N2-Ar mixture is adjusted by adding N2 or Ar until the drop becomes neutrally buoyant. The density of this mixture and thus of the drop is determined using a test mass and Archimedes principle. With appropriate care in drop preparation, management of gas above the liquid cryogen mixture to minimize icing, and regular mixing of the cryogenic mixture to prevent density stratification and phase separation, densities accurate to &#60;0.5% of drops as small as 50 pL can readily be determined. Measurements on aqueous cryoprotectant mixtures provide insight into cryoprotectant action, and provide quantitative data to facilitate thermal contraction matching in biological cryopreservation.

A protocol for determining the vitreous phase densities of micro- to pico-liter size drops of aqueous mixtures at cryogenic temperatures is described.

We demonstrate a method for determining the vitreous phase cryogenic temperature densities of aqueous mixtures, and other samples that require rapid ...

In Situ Monitoring of the Accelerated Performance Degradation of Solar Cells and Modules: A Case Study for Cu(In,Ga)Se2 Solar Cells

The levelized cost of electricity (LCOE) of photovoltaic (PV) systems is determined by, among other factors, the PV module reliability. Better prediction of degradation mechanisms and prevention of module field failure can consequently decrease investment risks as well as increase the electricity yield. An improved knowledge level can for these reasons significantly decrease the total costs of PV electricity. 
In order to better understand and minimize the degradation of PV modules, the occurring degradation mechanisms and conditions should be identified. This should preferably happen under combined stresses, since modules in the field are also simultaneously exposed to multiple stress factors. Therefore, two 'Combined Stress test with in situ measurement' setups have been designed and constructed. These setups allow the simultaneous use of humidity, temperature, illumination, and electrical biases as independently controlled stress factors on solar cells and minimodules. The setups also allow real-time monitoring of the electrical properties of these samples. This protocol presents these setups and describes the experimental possibilities. Moreover, results obtained with these setups are also presented: various examples about the influence of both deposition and degradation conditions on the stability of thin film Cu(In,Ga)Se2 (CIGS) as well as Cu2ZnSnSe4 (CZTS) solar cells are described. Results on the temperature dependency of CIGS solar cells are also presented.

In Situ Monitoring of the Accelerated Performance Degradation of Solar Cells and Modules: A Case Study for CuIn,GaSe2 Solar Cells

Two &#39;Combined Stress test with in situ measurement&#39; setups, which allow real-time monitoring of accelerated degradation of solar cells and modules, were designed and constructed. These setups allow the simultaneous use of humidity, temperature, electrical biases, and illumination as independently controlled stress factors. The setups and various experiments executed are presented.

The levelized cost of electricity (LCOE) of photovoltaic (PV) systems is determined by, among other factors, the PV module reliability. Better prediction ...

In Situ High Pressure Hydrogen Tribological Testing of Common Polymer Materials Used in the Hydrogen Delivery Infrastructure

High pressure hydrogen gas is known to adversely affect metallic components of compressors, valves, hoses, and actuators. However, relatively little is known about the effects of high pressure hydrogen on the polymer sealing and barrier materials also found within these components. More study is required in order to determine the compatibility of common polymer materials found in the components of the hydrogen fuel delivery infrastructure with high pressure hydrogen. As a result, it is important to consider the changes in physical properties such as friction and wear in situ while the polymer is exposed to high pressure hydrogen. In this protocol, we present a method for testing the friction and wear properties of ethylene propylene diene monomer (EPDM) elastomer samples in a 28 MPa high pressure hydrogen environment using a custom-built in situ pin-on-flat linear reciprocating tribometer. Representative results from this testing are presented which indicate that the coefficient of friction between the EPDM sample coupon and steel counter surface is increased in high pressure hydrogen as compared to the coefficient of friction similarly measured in ambient air.

In Situ High Pressure Hydrogen Tribological Testing of Common Polymer Materials Used in the Hydrogen Delivery Infrastructure

A test methodology for quantifying tribological properties of polymers used in hydrogen infrastructure service is demonstrated and characteristic results for a common elastomer are discussed.

High pressure hydrogen gas is known to adversely affect metallic components of compressors, valves, hoses, and actuators. However, relatively little is ...

Experimental Procedure for Laboratory Studies of In Situ Burning : Flammability and Burning Efficiency of Crude Oil

A new method for the simultaneous study of the flammability and burning efficiency of fresh and weathered crude oil through two experimental laboratory setups is presented. The experiments are easily repeatable compared to operational scale experiments (pool diameter &#8805;2 m), while still featuring quite realistic in situ burning conditions of crude oil on water. Experimental conditions include a flowing water sub-layer that cools the oil slick and an external heat flux (up to 50 kW/m2) that simulates the higher heat feedback to the fuel surface in operational scale crude oil pool fires. These conditions enable a controlled laboratory study of the burning efficiency of crude oil pool fires that are equivalent to operational scale experiments. The method also provides quantitative data on the requirements for igniting crude oils in terms of the critical heat flux, ignition delay time as a function of the incident heat flux, the surface temperature upon ignition, and the thermal inertia. This type of data can be used to determine the required strength and duration of an ignition source to ignite a certain type of fresh or weathered crude oil. The main limitation of the method is that the cooling effect of the flowing water sub-layer on the burning crude oil as a function of the external heat flux has not been fully quantified. Experimental results clearly showed that the flowing water sub-layer does improve how representative this setup is of in situ burning conditions, but to what extent this representation is accurate is currently uncertain. The method nevertheless features the most realistic in situ burning laboratory conditions currently available for simultaneously studying the flammability and burning efficiency of crude oil on water.

Experimental Procedure for Laboratory Studies of In Situ Burning : Flammability and Burning Efficiency of Crude Oil

Here, we present a protocol to simultaneously study the flammability and burning efficiency of fresh and weathered crude oil under conditions that simulate in situ burning operations on the sea.

A new method for the simultaneous study of the flammability and burning efficiency of fresh and weathered crude oil through two experimental laboratory ...