LH gratefully acknowledges financial support by an US National Science Foundation Graduate Research Fellowship under Grant No. 1148897. Electron microscopy characterization and SPS processing at UC Davis was financially supported by a University of California Laboratory Fee award (#12-LR-238313). Work at the Molecular Foundry was supported by the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

1. Sample Preparation of Single Crystal Strontium Titanate
NOTE: Single crystal STO is supplied with a (100) surface polished to a mirror finish.
<ol>
	<li>Section STO into 5x5 mm2 pieces using diamond wire saw.</li>
	<li>Ultrasonically clean samples at 50-60 Hz consecutively in baths of acetone, isopropanol, and methanol for fifteen minutes each.</li>
	<li>Remove STO from methanol bath to immediately place on hot plate held at a temperature of 200 &#176;C. Heating the sample after cleaning prevents formation of evaporation spotting from the alcohol.</li>
	<li>Place samples for ten minutes in buffered hydrofluoric acid (pH=4), a 6:1 solution of ammonium fluoride and 49% hydrofluoric acid.22 This solution etches the STO, forming a predominantly (100) TiO2 terminated surface. If the optically flat side of the single crystal has a rainbow patina, the sample has been over-etched and should not be used.</li>
	<li>After ten minutes in the etchant solution, rinse samples in deionized (DI) water and then in isopropanol. Dry using clean house air.</li>
</ol>
2. Bicrystal Formation via Spark Plasma Sintering Apparatus
NOTE: For 5x5 mm2 crystal use a 30 mm diameter graphite die. If a die with a diameter smaller than 30 mm is used, the bicrystal catastrophically fractures during bonding. Optimal die size as well as pressure exerted by the SPS apparatus is highly dependent on the size of the crystals.
<ol>
	<li>Place a 30 mm circle of graphite paper on a graphite plunger with a 30 mm diameter. Graphite paper prevents STO from bonding to the graphite plunger during the experiment.</li>
	<li>Stack two 5x5 mm2 STO single crystals with their optically flat surfaces placed facing inward to form the bicrystal boundary. Center the stack on top of the graphite paper and plunger.</li>
	<li>Rotate the top single crystal around the &#60;100&#62; axis to a chosen misorientation angle. The &#60;100&#62; axis is perpendicular to the optically flat surface of crystal.</li>
	<li>Slide the graphite die over the plunger and crystals. Place a second 30 mm diameter circle of graphite paper and then 30 mm diameter plunger over the stacked STO crystals.</li>
	<li>Stack the combined plungers and die onto the graphite spacers in SPS apparatus (Figure 1).</li>
	<li>Apply a uniaxial force of 3 kN to minimize contact resistance using the z-axis control buttons. Throughout the experiment, the user must keep the force at 3 kN via the z-axis control buttons.</li>
	<li>Insert k-type thermocouple into graphite die at the small hole, shown in Figure 1. The thermocouple extends through the die to the sample.</li>
	<li>Set the chamber pressure of the SPS apparatus to ~10 Pa using the vacuum push buttons.</li>
	<li>Select bond temperature, time, and heating rates via program instrument control software (Table 1). For the bonding temperature and time, use a heating rate of 70-80 &#176;C/min and a cooling rate of 50 &#176;C/min.</li>
	<li>Set 12 s on, 2 s off DC pulse using the instrument sintering button. A pulsed bias of ~ 4 V and direct current of ~550 A are applied incrementally to the sample once the program is set to run.</li>
	<li>Press the start button on the machine.</li>
	<li>Remove the sample when the program ends. After bicrystal formation, the sample will appear grey-black due to the reducing environment of the SPS apparatus.</li>
	<li>Use a high temperature furnace at a temperature of 1,200 &#176;C for 140 h, apply no pressure during this procedure, to anneal and re-oxidize the sample in air. Annealing parameters were selected according to previous work done by Hutt et al. in which bicrystals formed in high vacuum13. After annealing, the sample reveals an off-white color and is oxidized.</li>
</ol>
3. Sample Preparation of Bicrystal for Electron Beam Imaging
<ol>
	<li>Cross-section bicrystal with diamond wire saw into 5x1 mm2 sections.</li>
	<li>Polish cross-section samples with diamond lapping film. The grit size on the diamond lapping film is gradually decreased from 9 &#181;m to 0.1 &#181;m. Change to smaller grit size once scratches are uniform across the surface. Use a counter clockwise platen motion for 9 &#181;m to 6 &#181;m lapping film. Use a counter clockwise platen motion with an oscillating sample head for 6 &#181;m to 0.1 &#181;m lapping film.</li>
	<li>Polish cross-section samples with colloidal silica for two minutes using a mat cloth. Continuously pour colloidal silica onto the mat with counter clockwise platen motion and oscillating sample head.</li>
	<li>Fifteen seconds before removing the sample, stop pouring colloidal silica and pour DI water onto platen. Pour DI water for fifteen seconds, remove sample, and immediately rinse sample in DI water for 1 min. If this procedure is not followed, the colloidal silica will bond the sample&#39;s surface and obscure the grain boundary during scanning electron microscopy (SEM).</li>
	<li>Once the sample is polished to an optically smooth surface, ultrasonically clean samples consecutively in baths of acetone, isopropanol, and methanol for fifteen minutes each.</li>
	<li>Remove STO from methanol bath to immediately place on hot plate held at a temperature of 200 &#176;C. Heating the sample after cleaning prevents formation of evaporation spotting from the alcohol.</li>
	<li>Mount sample polished surface up onto a sample stub using colloidal graphite.</li>
	<li>Sputter coat sample surface with 2-3 nm of carbon. Use the following parameters for the carbon coater: a pulse resolution of 0.2 nm/pulse, current step rate of 0.2 A/pulse, pulse current of 40 A, pulse length of 2 s, and maximum pulses of 50.</li>
</ol>
4. Cleaning the FIB Copper Grid
NOTE: Improper cleaning of the FIB grid can lead to carbon contamination of the lamella in the TEM.
<ol>
	<li>Place copper FIB grid in an acetone and then isopropanol bath for 1 h each.</li>
	<li>Plasma clean copper FIB grid for 10 min.</li>
</ol>
5. Preparation of Transmission Electron Microscopy (TEM) Lamella via Focused Ion Beam (FIB) Apparatus
NOTE: All parameters used in FIB preparation are typed or selected from a drop down menu in the FIB apparatus software.
<ol>
	<li>Place STO sample and copper FIB grid in FIB apparatus. The stage is at 7 mm.</li>
	<li>Find a region of interest along the interface between the two single crystals, i.e., the grain boundary.</li>
	<li>Select Patterning dialogue box. In Patterning Control, select the Rectangle Patterning Tool with application property C-e-dep surface. Insert C-dep for gas injection. Deposit a 15&#215;2&#215;2 &#181;m3 protective layer of carbon using the electron beam at a voltage of 5.0 kV, a current of 13.0 nA, and a tilt angle of 0&#176;. Retract C-dep.</li>
	<li>Select Patterning dialogue box. In Patterning Control, select the Rectangle Patterning Tool with application property W-dep. Insert W-dep for gas injection. Deposit 15&#215;2&#215;2 &#181;m3 protective layer of tungsten using the ion beam at a voltage of 30.0 kV, a current of 0.3 nA, and a tilt angle of 52&#176;. Retract W-dep.</li>
	<li>Select Patterning dialogue box. In Patterning Control, select the Regular Cross Section Patterning Tool with application property Si. Use 22&#215;25&#215;15 &#181;m3 for the bottom pattern and of 22&#215;27&#215;15 &#181;m3 for the top pattern at a voltage of 30.0 kV, a current of 30.0 nA, and a tilt angle of 52&#176; via the ion beam. The pattern will create a trench mill on both sides of the protective layer.</li>
	<li>Select Patterning dialogue box. In Patterning Control, select the Clean Cross Section Patterning Tool with application property Si. Use 22&#215;3&#215;60 &#181;m3 for the top and bottom pattern at a voltage of 30.0 kV and a current of 1.0 nA via the ion beam. The tilt angle is 53.5&#176; for the bottom pattern and 50.5&#176; for the top pattern. The pattern cleans the surface of the trenched lamella from the curtaining pattern that results from the regular cross section patterning.</li>
	<li>Cut a J-pattern into the sample using the Rectangle Patterning tool with application property Si. Use 2 &#181;m for the width at a voltage of 30.0 kV and a current of 1.0 nA via the ion beam.</li>
	<li>Select Easy Lift dialogue box. Insert the micromanipulator to the park position. Lower the micromanipulator and attach the sample to the copper FIB grid via a tungsten weld using the process detailed in 5.4.</li>
	<li>Using the steps detailed in 5.7, &#181;cut a U-pattern, continuing from the original J-pattern, in the sample using the ion beam at a voltage of 30.0 kV and a current of 1.0 nA.</li>
	<li>Lift the lamella via the micromanipulator above the bulk sample.</li>
	<li>Rotate the micromanipulator 180&#176;, so the grain boundary is no longer parallel to ion beam, but perpendicular to the ion beam.</li>
	<li>Tungsten weld the lamella to a copper FIB grid using the steps detailed in 5.4 with the ion beam at a voltage of 30.0 kV and a current of 0.3 nA.</li>
	<li>Cut the micromanipulator from the lamella using the steps detailed in 5.7 with the ion beam at a voltage of 30.0 kV and a current of 1.0 nA.</li>
	<li>Repeat the steps detailed in 5.3. Deposit a 15&#215;2&#215;4 &#181;m3 protective layer of carbon using an electron beam at a voltage of 5.0 kV, a current of 13.0 nA, and a tilt angle of 0&#176;.</li>
	<li>Repeat the steps detailed in 5.4. Deposit 15&#215;2&#215;8 &#181;m3 protective layer of tungsten using an ion beam at a voltage of 30.0 kV, a current of 0.3 nA, and a tilt angle of 52&#176;.</li>
	<li>With the ion beam, thin the sample to approximately 200 nm using a voltage of 30.0 kV and a systematically decreasing current of 0.5 nA, 0.3 nA, and 0.1 nA. At this stage, a cleaning cross section pattern is used and the sample is tilted to an angle of 52 &#177;&#177; 1.5&#176;.</li>
	<li>With the ion beam, thin the sample to electron transparency using a voltage of 5.0 kV and a current of 77.0 pA. At this stage, a rectangle pattern is used with a tilt angle of 52 &#177; 3&#176;.</li>
	<li>Remove amorphous damage incurred from the FIB by cleaning the sample at a voltage of 500 eV and a current of 150 &#181;A.</li>
	<li>Place TEM sample in TEM holder and insert holder in scanning transmission electron microscope (STEM). Select &#39;Capture&#39;, image sample grain boundary.</li>
</ol>

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We have nothing to disclose.

The bonding temperature of 1,200 &#176;C was chosen to maximize diffusion as small changes in temperature can greatly impact the kinetics of all diffusion bonding mechanisms. A temperature of 1,200 &#176;C is outside the brittle-ductile transition temperature range of STO. However, the sample underwent brittle fracture at this temperature. The catastrophic failure of the STO bicrystal was not unexpected as STO has ~ 0.5% ductility at 1,200 &#176;C. Also, the sample was held at a pressure of 140 MPa throughout the heating...

Spark plasma sintering (SPS) is a technique in which application of high uniaxial pressure and pulsed direct current leads to the rapid densification of powder compacts1. This technique also leads to the successful formation of composite structures from various materials, including silicon nitride/silicon carbide, zirconium boride/silicon carbide, or silicon carbide, with no additional sintering aids required2,3,4,5. The synthesis of these composite structures by conventional hot-pressing had been challenging in the past. While application of a high uniaxial pressure and fast heating rate via the SPS technique enhances consolidation of powders and composites, the phenomenon causing this enhanced densification debated in the literature2,3,6,7. There also exists only limited information regarding the influence of electric fields on grain boundary formation and the resulting atomic structures of grain boundary cores8,9. These core structures determine the functional properties of SPS sintered materials, including electric breakdown of high voltage capacitors and the mechanical strength and toughness of ceramic oxides10. Therefore, understanding the fundamental grain boundary structure as a function of SPS processing parameters, such as applied current, is necessary for the manipulation of a material&#39;s overall physical properties. One method to systematically elucidate the fundamental physical mechanisms underpinning SPS is the formation of specific grain boundary structures, i.e., bicrystals. A bicrystal is created by manipulation of two single crystals, which are then diffusion bonded with specific misorientation angles11. This method provides a controlled way to investigate the fundamental grain boundary core structures as a function of processing parameters, dopant concentration, and impurity segregation12,13,14.
Diffusion bonding is dependent on four parameters: temperature, time, pressure, and bonding atmosphere15. Conventional diffusion bonding of strontium titanate (SrTiO3, STO) bicrystals typically occurs at a pressure below 1 MPa, within a temperature range of 1,400-1,500 &#176;C, and time scales ranging from 3 to 20 hours13,14,16,17. In this study, bonding in a SPS apparatus is achieved at significantly lower temperature and time scales in comparison to conventional methods. For polycrystalline materials, reduced temperature and time scales via SPS significantly limits grain growth, thereby providing advantageous control of a material&#39;s properties through manipulation of its microstructure.
The SPS apparatus, for a 5&#215;5 mm2 sample, exerts a minimum pressure of 140 MPa. Within the conventional diffusion bonding temperature range, Hutt et al. report instantaneous fracture of STO when the bonding pressure exceeds 10 MPa18. However, STO exhibits temperature dependent plasticity behavior, indicating bonding pressure can exceed 10 MPa at specific temperatures. Above 1,200 &#176;C and below 700 &#176;C, STO exhibits some ductility, at which stresses greater than 120 MPa can be applied without instantaneous fracture of the sample. Within the intermediate temperature range of 700-1,200 &#176;C, STO is brittle and experiences instantaneous fracture at stresses greater than 10 MPa. At 800 &#176;C, STO has minor deformability prior to fracture at stresses less than 200 MPa19,20,21. Hence, bonding temperatures for STO bicrystal formation via SPS apparatus must be selected according to the plasticity behavior of the material.

<table border="0" cellpadding="0" cellspacing="0" width="1429">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:373px;">Strontium titanate single crystal (100)</td>
			<td style="width:187px;">MTI Corporation</td>
			<td style="width:427px;">STOa101005S1-JP</td>
			<td style="width:443px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:373px;">Buffered oxide etch, hyrofluoric acid 6:1</td>
			<td style="width:187px;">JT Baker</td>
			<td style="width:427px;">&#160;MBI 1178-03</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:373px;">Scanning electron microscope (SEM)</td>
			<td style="width:187px;">FEI</td>
			<td>Model: 430 NanoSEM</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">SPS apparatus&#160;</td>
			<td>Sumitomo Coal Mining Co</td>
			<td>Model: Dr. Sinter 5000 SPS Apparatus</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">High Temperature Furnace</td>
			<td>Thermolyne</td>
			<td>Model: 41600</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ultrasonic Cleaner</td>
			<td>Bransonic</td>
			<td>Model: 221</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:373px;">Mechanical polisher</td>
			<td style="width:187px;">Allied High Tech Products</td>
			<td>15-2100-TEM</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:373px;">Diamond lapping film</td>
			<td style="width:187px;">3M</td>
			<td>660XV&#160;</td>
			<td>1 um to 9 um Grit Size</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:373px;">Diamond lapping film</td>
			<td style="width:187px;">3M</td>
			<td style="width:427px;">661X</td>
			<td>0.5 um to 0.1 um Grit Size</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:373px;">Colloidal silica</td>
			<td style="width:187px;">Allied High Tech Products</td>
			<td>180-20000</td>
			<td>.05 um Grit Size</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:373px;">Sputter coater</td>
			<td style="width:187px;">QuorumTech</td>
			<td>Model: Q150RES</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Focused ion beam (FIB) instrument&#160;</td>
			<td style="width:187px;">FEI</td>
			<td>Model: Scios dual-beamed focused ion beam (FIB) instrument&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Nanomill TEM specimen preparation system</td>
			<td style="width:187px;">Fischione Instruments</td>
			<td>Model: 1040</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Transmission electron microscope (TEM)&#160;</td>
			<td style="width:187px;">JEOL</td>
			<td>Model: JEM2500 SE&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Scanning transmission electron microscope (STEM)</td>
			<td style="width:187px;">FEI</td>
			<td>Model: TEAM 0.5&#160;</td>
			<td></td>
		</tr>
	</tbody>
</table>

spark plasma sintering apparatus used for the formation of strontium titanate bicrystals

A spark plasma sintering apparatus was used as a novel method for diffusion bonding of two single crystals of strontium titanate to form bicrystals with one twist grain boundary. This apparatus utilizes high uniaxial pressure and a pulsed direct current for rapid consolidation of material. Diffusion bonding of strontium titanate bicrystals without fracture, in a spark plasma sintering apparatus, is possible at high pressures due to the unusual temperature dependent plasticity behavior of strontium titanate. We demonstrate a method for the successful formation of bicrystals at accelerated time scales and lower temperatures in a spark plasma sintering apparatus compared to bicrystals formed by conventional diffusion bonding parameters. Bond quality was verified by scanning electron microscopy. A clean and atomically abrupt interface containing no secondary phases was observed using transmission electron microscopy techniques. Local changes in bonding across the boundary was characterized by simultaneous scanning transmission electron microscopy and spatially resolved electron energy-loss spectroscopy.

Bonding temperature, time, and misorientation angle were all altered to determine optimum parameters needed for the maximum possible bonded interface fraction of the STO bicrystal (Table 1). The interface was considered &#39;bonded&#39; when the grain boundary was not visible during SEM imaging (Figure 2a). A &#39;non-bonded&#39; interface was exhibited when a dark image contrast or voids were present at the boundary location (Figure 2b)....

Watch this Scientific Journal Video about Spark Plasma Sintering Apparatus Used for the Formation of Strontium Titanate Bicrystals at JoVE.com

Spark Plasma Sintering Apparatus Used for the Formation of Strontium Titanate Bicrystals

A viable technique for the formation of strontium titanate bicrystals at high pressure and fast heating rate via the spark plasma sintering apparatus is developed.

A spark plasma sintering apparatus was used as a novel method for diffusion bonding of two single crystals of strontium titanate to form bicrystals with ...

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Research

JoVE Journal

Engineering

9.8K Views.  University of California, Davis. A viable technique for the formation of strontium titanate bicrystals at high pressure and fast heating rate via the spark plasma sintering apparatus is developed. 

Video: Spark Plasma Sintering Apparatus Used for the Formation of Strontium Titanate Bicrystals

Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses

Early plasma is generated owing to high intensity laser irradiation of target and the subsequent target material ionization. Its dynamics plays a significant role in laser-material interaction, especially in the air environment1-11.
Early plasma evolution has been captured through pump-probe shadowgraphy1-3 and interferometry1,4-7. However, the studied time frames and applied laser parameter ranges are limited. For example, direct examinations of plasma front locations and electron number densities within a delay time of 100 picosecond (ps) with respect to the laser pulse peak are still very few, especially for the ultrashort pulse of a duration around 100 femtosecond (fs) and a low power density around 1014 W/cm2. Early plasma generated under these conditions has only been captured recently with high temporal and spatial resolutions12. The detailed setup strategy and procedures of this high precision measurement will be illustrated in this paper. The rationale of the measurement is optical pump-probe shadowgraphy: one ultrashort laser pulse is split to a pump pulse and a probe pulse, while the delay time between them can be adjusted by changing their beam path lengths. The pump pulse ablates the target and generates the early plasma, and the probe pulse propagates through the plasma region and detects the non-uniformity of electron number density. In addition, animations are generated using the calculated results from the simulation model of Ref. 12 to illustrate the plasma formation and evolution with a very high resolution (0.04 ~ 1 ps).
Both the experimental method and the simulation method can be applied to a broad range of time frames and laser parameters. These methods can be used to examine the early plasma generated not only from metals, but also from semiconductors and insulators.

An experimental method to examine the early plasma evolution induced by ultrashort laser pulses is described. Using this method, high quality images of early plasma are obtained with high temporal and spatial resolutions. A novel integrated atomistic model is used to simulate and explain the mechanisms of early plasma.

Early plasma is generated owing to high intensity laser irradiation of target and the subsequent target material ionization. Its dynamics plays a ...

Encapsulation and Permeability Characteristics of Plasma Polymerized Hollow Particles

In this protocol, core-shell nanostructures are synthesized by plasma enhanced chemical vapor deposition. We produce an amorphous barrier by plasma polymerization of isopropanol on various solid substrates, including silica and potassium chloride. This versatile technique is used to treat nanoparticles and nanopowders with sizes ranging from 37 nm to 1 micron, by depositing films whose thickness can be anywhere from 1 nm to upwards of 100 nm. Dissolution of the core allows us to study the rate of permeation through the film. In these experiments, we determine the diffusion coefficient of KCl through the barrier film by coating KCL nanocrystals and subsequently monitoring the ionic conductivity of the coated particles suspended in water. The primary interest in this process is the encapsulation and delayed release of solutes. The thickness of the shell is one of the independent variables by which we control the rate of release. It has a strong effect on the rate of release, which increases from a six-hour release (shell thickness is 20 nm) to a long-term release over 30 days (shell thickness is 95 nm). The release profile shows a characteristic behavior: a fast release (35% of the final materials) during the first five minutes after the beginning of the dissolution, and a slower release till all of the core materials come out.

We have used plasma enhanced chemical vapor deposition to deposit thin films ranging from a few nm to several 100 nm on nano-sized particles of various materials. We subsequently etch the core material to produce hollow nanoshells whose permeability is controlled by the thickness of the shell. We characterize the permeability of these coatings to small solutes and demonstrate that these barriers can provide sustained release of the core material over several days.

In this protocol, core-shell nanostructures are synthesized by plasma enhanced chemical vapor deposition. We produce an amorphous barrier by plasma ...

Characterization of Recombination Effects in a Liquid Ionization Chamber Used for the Dosimetry of a Radiosurgical Accelerator

Most modern radiation therapy devices allow the use of very small fields, either through beamlets in Intensity-Modulated Radiation Therapy (IMRT) or via stereotactic radiotherapy where positioning accuracy allows delivering very high doses per fraction in a small volume of the patient. Dosimetric measurements on medical accelerators are conventionally realized using air-filled ionization chambers. However, in small beams these are subject to nonnegligible perturbation effects. This study focuses on liquid ionization chambers, which offer advantages in terms of spatial resolution and low fluence perturbation. Ion recombination effects are investigated for the microLion detector (PTW) used with the Cyberknife system (Accuray). The method consists of performing a series of water tank measurements at different source-surface distances, and applying corrections to the liquid detector readings based on simultaneous gaseous detector measurements. This approach facilitates isolating the recombination effects arising from the high density of the liquid sensitive medium and obtaining correction factors to apply to the detector readings. The main difficulty resides in achieving a sufficient level of accuracy in the setup to be able to detect small changes in the chamber response.

A growing number of radiation therapy devices offer the advantage of delivering the dose through very small beams to the tumor, allowing for increased conformity and higher doses per fraction. Many different detectors can be used for the dosimetry of these small fields. In the present study, the effect of ion recombination is investigated for a liquid ionization chamber using a stereotactic radiation therapy system.

Most modern radiation therapy devices allow the use of very small fields, either through beamlets in Intensity-Modulated Radiation Therapy (IMRT) or via ...

How to Ignite an Atmospheric Pressure Microwave Plasma Torch without Any Additional Igniters

This movie shows how an atmospheric pressure plasma torch can be ignited by microwave power with no additional igniters. After ignition of the plasma, a stable and continuous operation of the plasma is possible and the plasma torch can be used for many different applications. On one hand, the hot (3,600 K gas temperature) plasma can be used for chemical processes and on the other hand the cold afterglow (temperatures down to almost RT) can be applied for surface processes. For example chemical syntheses are interesting volume processes. Here the microwave plasma torch can be used for the decomposition of waste gases which are harmful and contribute to the global warming but are needed as etching gases in growing industry sectors like the semiconductor branch. Another application is the dissociation of CO2. Surplus electrical energy from renewable energy sources can be used to dissociate CO2 to CO and O2. The CO can be further processed to gaseous or liquid higher hydrocarbons thereby providing chemical storage of the energy, synthetic fuels or platform chemicals for the chemical industry. Applications of the afterglow of the plasma torch are the treatment of surfaces to increase the adhesion of lacquer, glue or paint, and the sterilization or decontamination of different kind of surfaces. The movie will explain how to ignite the plasma solely by microwave power without any additional igniters, e.g., electric sparks. The microwave plasma torch is based on a combination of two resonators &#8212; a coaxial one which provides the ignition of the plasma and a cylindrical one which guarantees a continuous and stable operation of the plasma after ignition. The plasma can be operated in a long microwave transparent tube for volume processes or shaped by orifices for surface treatment purposes.

This movie shows how an atmospheric plasma torch can be ignited by microwaves with no additional igniters and provides a stable and continuous plasma operation suitable for plenty of applications.

This movie shows how an atmospheric pressure plasma torch can be ignited by microwave power with no additional igniters. After ignition of the plasma, a ...

Capillary-based Centrifugal Microfluidic Device for Size-controllable Formation of Monodisperse Microdroplets

Here, we demonstrate a simple method for the rapid production of size-controllable, monodisperse, W/O microdroplets using a capillary-based centrifugal microfluidic device. W/O microdroplets have recently been used in powerful methods that enable miniaturized chemical experiments. Therefore, developing a versatile method to yield monodisperse W/O microdroplets is needed. We have developed a method for generating monodisperse W/O microdroplets based on a capillary-based centrifugal axisymmetric co-flowing microfluidic device. We succeeded in controlling the size of microdroplets by adjusting the capillary orifice. Our method requires equipment that is easier-to-use than with other microfluidic techniques, requires only a small volume (0.1-1 &#181;l) of sample solution for encapsulation, and enables the production of hundreds of thousands number of W/O microdroplets per second. We expect this method will assist biological studies that require precious biological samples by conserving the volume of the samples for rapid quantitative analysis biochemical and biological studies.

Here, we demonstrate a simple production method for size-controllable, monodisperse, water-in-oil (W/O) microdroplets using a capillary-based centrifugal microfluidic device. This method requires only a small sample volume and enables high-yield production. We expect this method will be useful for rapid biochemical and cellular analyses.

Here, we demonstrate a simple method for the rapid production of size-controllable, monodisperse, W/O microdroplets using a capillary-based centrifugal ...

Applying X-ray Imaging Crystal Spectroscopy for Use as a High Temperature Plasma Diagnostic

X-ray spectra provide a wealth of information on high temperature plasmas; for example electron temperature and density can be inferred from line intensity ratios. By using a Johann spectrometer viewing the plasma, it is possible to construct profiles of plasma parameters such as density, temperature, and velocity with good spatial and time resolution. However, benchmarking atomic code modeling of X-ray spectra obtained from well-diagnosed laboratory plasmas is important to justify use of such spectra to determine plasma parameters when other independent diagnostics are not available. This manuscript presents the operation of the High Resolution X-ray Crystal Imaging Spectrometer with Spatial Resolution (HIREXSR), a high wavelength resolution spatially imaging X-ray spectrometer used to view hydrogen- and helium-like ions of medium atomic number elements in a tokamak plasma. In addition, this manuscript covers a laser blow-off system that can introduce such ions to the plasma with precise timing to allow for perturbative studies of transport in the plasma.

X-ray spectra provide a wealth of information on high temperature plasmas. This manuscript presents the operation of a high wavelength resolution spatially imaging X-ray spectrometer used to view hydrogen- and helium-like ions of medium atomic number elements in a tokamak plasma.

X-ray spectra provide a wealth of information on high temperature plasmas; for example electron temperature and density can be inferred from line ...

An Atmospheric Pressure Plasma Setup to Investigate the Reactive Species Formation

Non-thermal atmospheric pressure (&#39;cold&#39;) plasmas have received increased attention in recent years due to their significant biomedical potential. The reactions of cold plasma with the surrounding atmosphere yield a variety of reactive species, which can define its effectiveness. While efficient development of cold plasma therapy requires kinetic models, model benchmarking needs empirical data. Experimental studies of the source of reactive species detected in aqueous solutions exposed to plasma are still scarce. Biomedical plasma is often operated with He or Ar feed gas, and a specific interest lies in investigation of the reactive species generated by plasma with various gas admixtures (O2, N2, air, H2O vapor, etc.) Such investigations are very complex due to difficulties in controlling the ambient atmosphere in contact with the plasma effluent. In this work, we addressed common issues of &#39;high&#39; voltage kHz frequency driven plasma jet experimental studies. A reactor was developed allowing the exclusion of ambient atmosphere from the plasma-liquid system. The system thus comprised the feed gas with admixtures and the components of the liquid sample. This controlled atmosphere allowed the investigation of the source of the reactive oxygen species induced in aqueous solutions by He-water vapor plasma. The use of isotopically labelled water allowed distinguishing between the species originating in the gas phase and those formed in the liquid. The plasma equipment was contained inside a Faraday cage to eliminate possible influence of any external field. The setup is versatile and can aid in further understanding the cold plasma-liquid interactions chemistry.

An experimental setup was created for the helium-operated kHz frequency plasma jet. The setup includes a cage for the plasma power supply and jet and an in-house built reactor to monitor plasma-induced reactive species without the interference of the ambient atmosphere.

Non-thermal atmospheric pressure (&#39;cold&#39;) plasmas have received increased attention in recent years due to their significant biomedical potential. ...

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 ...

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 ...

New Application of an Atmospheric Pressure Plasma Jet as a Neuro-protective Agent Against Glucose Deprivation-induced Injury of SH-SY5Y Cells

The atmospheric pressure plasma jet (APPJ) has attracted the attention of many researchers from multiple disciplines in recent years because its emissions include multiple types of reactive nitrogen species (RNS) and reactive oxygen species (ROS). Our previous study has shown the cytoprotective effect of the APPJ against oxidative stress-induced injuries. The aim of the present study is to provide a detailed in vitro treatment protocol regarding the neuroprotective applications of helium APPJs on glucose deprivation-induced injury in SH-SY5Y cells. The SH-SY5Y human neuroblastoma-derived cell line was maintained in RPMI 1640 medium supplemented with 15% fetal calf serum. The culture medium was then changed to RPMI 1640 without glucose before APPJ treatment. After a 1 h incubation in a cell incubator, cell viability was determined using Cell Counting Kit 8. The results showed that, compared to the glucose deprivation group, cells treated with APPJ exhibited significantly increased cell viability in a dose-dependent manner, with 8 s/well observed as an optimal dose. Meanwhile, helium flow had no effect on the glucose deprivation-induced cell impairment. Our results indicated that APPJ could be potentially used as a treatment method for the diseases in the central nervous system related to glucose deprivation. This protocol could also be used as a cytoprotective application for other cells with different impairments, but the cell culture and APPJ treatment conditions should be readjusted, and the treatment dose must be relatively low.

A protocol for the neuroprotective application of low-dose atmospheric pressure plasma treatment on glucose deprivation-induced SH-SY5Y injuries.

The atmospheric pressure plasma jet (APPJ) has attracted the attention of many researchers from multiple disciplines in recent years because its emissions ...