Name: determination of aggregate surface morphology at the interfacial transition zone (itz)
Uploaded: 2019-12-16T15:00:00
Description: Watch this Scientific Journal Video about Determination of Aggregate Surface Morphology at the Interfacial Transition Zone ITZ at JoVE.com

The authors gratefully acknowledge the financial support from the National Key R&#38;D Program of China (2017YFB0309904), National Natural Science Foundation of China (Grant Nos. 51508090 and 51808188), 973 Program (2015CB655100), State Key Laboratory of High-Performance Civil Engineering Materials (2016CEM005). Also, greatly appreciate Jiangsu Research Institute of Building Science Co., Ltd and the State Key Laboratory of High-Performance Civil Engineering Materials for funding the research project.

1. Preparation of the model concrete with a single ceramic particle
<ol>
	<li>Mold preparation
	<ol>
		<li>Use a brush to clean the mold (25 mm x 25 mm x 25 mm) and ensure that the inner surfaces of the mold are impurity-free.</li>
		<li>Use another brush to uniformly apply diesel oil on the inner surfaces of the mold for easier mold-release. 
		NOTE: Here, we did not use the common mold for mortar or concrete preparation. As the ceramic particle is around 15 mm in diameter, a cubic plastic mold around 30 mm in le...

<ol>
	<li>Scrivener, K. L., Crumbie, A. K., Laugesen, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Interfacial+Transition+Zone+(ITZ)+Between+Cement+Paste+and+Aggregate+in+Concrete.">The Interfacial Transition Zone (ITZ) Between Cement Paste and Aggregate in Concrete.</a> Interface Science. 12 (4), 411-421 (2004).</li><li>Scrivener, K. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Backscattered+electron+imaging+of+cementitious+microstructures:+understanding+and+quantification.">Backscattered electron imaging of cementitious microstructures: understanding and quantification.</a> Cement and Concrete Composites. 26 (8), 935-945 (2004).</li><li>Houst, Y. F., Sadouki, H., Wittmann, F. 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The X-CT technique was applied to roughly determine the geometrical center of the ceramic particle to ensure that the analyzed surface is through the equator of the particle. Thus, the overestimation of the ITZ thickness caused by the 2D artifacts could be avoided38. Herein, the accuracy of obtained results is highly dependent on the flatness of the examined surfaces. Generally, a longer grinding and polishing time contributes to an adequately smooth surface for testing. However, due to the varyin...

At the mesoscopic scale, cement-based materials can be regarded as a three-phase composite comprised of the cement paste, the aggregate, and the interfacial transition zone (ITZ) between them1,2. The ITZ is often treated as a weak link since its increased porosity could act as channels for the ingress of aggressive species3,4 or provide easier pathways for crack growth5,6,7,8,9,10,11. Subsequently, it is of great interest to precisely characterize the properties of the ITZ to evaluate and predict the macro performance of the cement-based materials.
To investigate the ITZ, there has been excessive research on its microstructural features, forming mechanisms, and influencing factors12,13,14 using both experimental and numerical methods. Various techniques have been coupled for ITZ characterization including: mechanical tests, transport tests, mercury intrusion porosimetry (MIP) tests15,16 and nano-indentation17. It is widely accepted that the ITZ is mainly caused by the wall effect, as well as water film, micro-bleeding, one side growth, and gel syneresis18.
With the development of digital image processing method (DIP) in the last two decades19, the morphological characteristics of the ITZ (e.g., volume fraction, thickness, and porosity gradient) can be quantitatively determined. Based on examination of the plane sections using scanning electron microscopy (SEM) with a backscattered electron detector (BSE), the three dimensional (3D) features of ITZ can be derived from the 2D results via stereology theory20. Like the SEM-BSE technique, the nano-indentation technique is also based on the examination of polished surfaces, but it more focuses on the elastic modulus of the existing phases21. However, in both SEM-BSE analysis and the nano-indentation test, the ITZ thickness may be overestimated as the examined cross section rarely goes through the normal direction from an aggregate surface22. However, coupling this with fluorescent 3D confocal microscopy, the overestimation of ITZ could be eliminated and a real ITZ porosity and anhydrous cement content could be obtained23.
Previous studies of influencing factors mainly focused on the cement paste, ignoring the role of the aggregate and its surface texture24,25,26. Since the shape and morphological properties of the aggregate have been extensively described based on quantitative analysis of digital slices obtained from SEM or X-ray computed tomography (X-CT)27,28. However, no research focusing on the effect of the aggregate surface texture on the formation of ITZ region has been performed.
Hereby, we present a protocol to investigate the effect of aggregate surface morphology on the ITZ microstructure formation based on quantitative analysis of SEM-BSE images and a K-means clustering algorithm. A model concrete sample was prepared with spherical ceramic particle acting as the coarse aggregate. X-CT was used to roughly determine the relative location of the particle in the opaque cement matrix before halving the sample. After processing to obtained SEM-BSE images, the uneven distribution of ITZ around single aggregate was observed. Also, an index surface roughness (SR) describing the aggregate surface texture at the pixel level was defined. The K-means clustering algorithm, originally used in the area of signal processing and now widely used for image clustering29,30, was introduced to established a relationship between surface roughness (SR) and porosity gradient (SL).

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			<td>&#934;15 mm</td>
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			<td>Nissin Corporation</td>
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			<td>Buehler</td>
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		</tr>
		<tr>
			<td>High precision cutting machine</td>
			<td>Buehler</td>
			<td>2215</td>
			<td></td>
		</tr>
		<tr>
			<td>Image J</td>
			<td>National Institutes of Health</td>
			<td>1.52o</td>
			<td></td>
		</tr>
		<tr>
			<td>Isopropyl alcohol</td>
			<td>Sinopharm</td>
			<td>M0130-241</td>
			<td></td>
		</tr>
		<tr>
			<td>Matlab</td>
			<td>MathWorks</td>
			<td>R2014a</td>
			<td></td>
		</tr>
		<tr>
			<td>Paper</td>
			<td>Deli</td>
			<td>A4</td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic box</td>
			<td>Beichen</td>
			<td>3630</td>
			<td></td>
		</tr>
		<tr>
			<td>Plastic mold</td>
			<td>Youke</td>
			<td>a=b=c=25mm</td>
			<td></td>
		</tr>
		<tr>
			<td>Polished flannelette</td>
			<td>Buehler</td>
			<td>242150, 00242050, 00242100</td>
			<td></td>
		</tr>
		<tr>
			<td>Release agent</td>
			<td>Buehler</td>
			<td>20-8186-30</td>
			<td></td>
		</tr>
		<tr>
			<td>Scanning Electron Microscopy</td>
			<td>FEI</td>
			<td>Quanta 250</td>
			<td></td>
		</tr>
		<tr>
			<td>Scrape knife</td>
			<td>Jinzheng Building Materials</td>
			<td>CD-3</td>
			<td></td>
		</tr>
		<tr>
			<td>SiC paper</td>
			<td>Buehler</td>
			<td>P180, P320, P1200</td>
			<td></td>
		</tr>
		<tr>
			<td>Ultrasonic cleaner</td>
			<td>Zhixin</td>
			<td>DLJ</td>
			<td></td>
		</tr>
		<tr>
			<td>Vacuum box</td>
			<td>Heheng</td>
			<td>DZF-6020</td>
			<td></td>
		</tr>
		<tr>
			<td>Vacuum drying oven</td>
			<td>ZK</td>
			<td>ZK30</td>
			<td></td>
		</tr>
		<tr>
			<td>Vibrating table</td>
			<td>Jianyi</td>
			<td>GZ-75</td>
			<td></td>
		</tr>
		<tr>
			<td>Wooden stick</td>
			<td>Buehler</td>
			<td>20-8175</td>
			<td></td>
		</tr>
		<tr>
			<td>X-ray Computed Tomography</td>
			<td>YXLON</td>
			<td>Y.CT PRECISION S</td>
			<td></td>
		</tr>
	</tbody>
</table>

determination of aggregate surface morphology at the interfacial transition zone (itz)

Here, we present a comprehensive method to illustrate the uneven distribution of the interfacial transition zone (ITZ) around the aggregate and the effect of aggregate surface morphology on the formation of ITZ. First, a model concrete sample is prepared with a spherical ceramic particle in roughly the central part of the cement matrix, acting as a coarse aggregate used in common concrete/mortar. After curing until the designed age, the sample is scanned by X-ray computed tomography to determine the relative location of the ceramic particle inside the cement matrix. Three locations of the ITZ are chosen: above the aggregate, on the side of the aggregate, and below the aggregate. After a series of treatments, the samples are scanned with a SEM-BSE detector. The resultant images were further processed using a digital image processing method (DIP) to obtain quantitative characteristics of the ITZ. The surface morphology is characterized at the pixel level based on the digital image. Thereafter, K-means clustering method is used to illustrate the effect of surface roughness on ITZ formation.

The porosity distribution of ITZ regions above the aggregate, on the side of the aggregate, and below the aggregate are compared and shown in Figure 432. The porosity of the ITZ above the upper surface appears to be smaller than that on the side or above the aggregate, indicating a denser ITZ microstructure, while the ITZ below the aggregate is always the most porous due to micro-bleeding. Figure 432 shows that eve...

Watch this Scientific Journal Video about Determination of Aggregate Surface Morphology at the Interfacial Transition Zone ITZ at JoVE.com

Determination of Aggregate Surface Morphology at the Interfacial Transition Zone ITZ

Hereby, we proposed a protocol to illustrate the effect of aggregate surface morphology on the ITZ microstructure. The SEM-BSE image were quantitatively analyzed to obtain ITZ's porosity gradient via digital image processing and a K-means clustering algorithm was further employed to establish a relationship between porosity gradient and surface roughness.

Determination of Aggregate Surface Morphology at the Interfacial Transition Zone (ITZ)

Here, we present a comprehensive method to illustrate the uneven distribution of the interfacial transition zone (ITZ) around the aggregate and the effect ...

determination-aggregate-surface-morphology-at-interfacial-transition

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Civil Engineering

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Unit 1

Aggregates and Water

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Experimental Measurement of Settling Velocity of Spherical Particles in Unconfined and Confined Surfactant-based Shear Thinning Viscoelastic Fluids

An experimental study is performed to measure the terminal settling velocities of spherical particles in surfactant based shear thinning viscoelastic (VES) fluids. The measurements are made for particles settling in unbounded fluids&#160;and fluids between parallel walls. VES fluids over a wide range of rheological properties are prepared and rheologically characterized. The rheological characterization involves steady shear-viscosity and dynamic oscillatory-shear measurements to quantify the viscous and elastic properties respectively. The settling velocities under unbounded conditions are measured in beakers having diameters at least 25x the diameter of particles. For measuring settling velocities between parallel walls, two experimental cells with different wall spacing are constructed. Spherical particles of varying sizes are gently dropped in the fluids and allowed to settle. The process is recorded with a high resolution video camera and the trajectory of the particle is recorded using image analysis software. Terminal settling velocities are calculated from the data.
The impact of elasticity on settling velocity in unbounded fluids is quantified by comparing the experimental settling velocity to the settling velocity calculated by the inelastic drag predictions of Renaud et al.1&#160;Results show that elasticity of fluids can increase or decrease the settling velocity. The magnitude of reduction/increase is a function of the rheological properties of the fluids and properties of particles. Confining walls are observed to cause a retardation effect on settling and the retardation is measured in terms of wall factors.

This paper demonstrates the experimental procedure to measure terminal settling velocities of spherical particles in surfactant-based shear thinning viscoelastic fluids. Fluids over a wide range of rheological properties are prepared and settling velocities are measured for a range of particle sizes in unbounded fluids and fluids between parallel walls.

An experimental study is performed to measure the terminal settling velocities of spherical particles in surfactant based shear thinning viscoelastic ...

Laboratory Drop Towers for the Experimental Simulation of Dust-aggregate Collisions in the Early Solar System

For the purpose of investigating the evolution of dust aggregates in the early Solar System, we developed two vacuum drop towers in which fragile dust aggregates with sizes up to ~10 cm and porosities up to 70% can be collided. One of the drop towers is primarily used for very low impact speeds down to below 0.01 m/sec and makes use of a double release mechanism. Collisions are recorded in stereo-view by two high-speed cameras, which fall along the glass vacuum tube in the center-of-mass frame of the two dust aggregates. The other free-fall tower makes use of an electromagnetic accelerator that is capable of gently accelerating dust aggregates to up to 5 m/sec. In combination with the release of another dust aggregate to free fall, collision speeds up to ~10 m/sec can be achieved. Here, two fixed high-speed cameras record the collision events. In both drop towers, the dust aggregates are in free fall during the collision so that they are weightless and match the conditions in the early Solar System.

We present a technique to achieve low-velocity to intermediate-velocity collisions between fragile dust aggregates in the laboratory. For this purpose, two vacuum drop-tower setups have been developed that allow collision velocities between &#60;0.01 and ~10 m/sec. The collision events are recorded by high-speed imaging.

For the purpose of investigating the evolution of dust aggregates in the early Solar System, we developed two vacuum drop towers in which fragile dust ...

Taking Advantage of Reduced Droplet-surface Interaction to Optimize Transport of Bioanalytes in Digital Microfluidics

Digital microfluidics (DMF), a technique for manipulation of droplets, is a promising alternative for the development of &#8220;lab-on-a-chip&#8221; platforms. Often, droplet motion relies on the wetting of a surface, directly associated with the application of an electric field; surface interactions, however, make motion dependent on droplet contents, limiting the breadth of applications of the technique.
Some alternatives have been presented to minimize this dependence. However, they rely on the addition of extra chemical species to the droplet or its surroundings, which could potentially interact with droplet moieties. Addressing this challenge, our group recently developed Field-DW devices to allow the transport of cells and proteins in DMF, without extra additives.
Here, the protocol for device fabrication and operation is provided, including the electronic interface for motion control. We also continue the studies with the devices, showing that multicellular, relatively large, model organisms can also be transported, arguably unaffected by the electric fields required for device operation.

The protocol for fabrication and operation of field dewetting devices (Field-DW) is described, as well as the preliminary studies of the effects of electric fields on droplet contents.

Digital microfluidics (DMF), a technique for manipulation of droplets, is a promising alternative for the development of &#8220;lab-on-a-chip&#8221; ...

Ambient Method for the Production of an Ionically Gated Carbon Nanotube Common Cathode in Tandem Organic Solar Cells

A method of fabricating organic photovoltaic (OPV) tandems that requires no vacuum processing is presented. These devices are comprised of two solution-processed polymeric cells connected in parallel by a transparent carbon nanotubes (CNT) interlayer. This structure includes improvements in fabrication techniques for tandem OPV devices. First the need for ambient-processed cathodes is considered. The CNT anode in the tandem device is tuned via ionic gating to become a common cathode. Ionic gating employs electric double layer charging to lower the work function of the CNT electrode. Secondly, the difficulty of sequentially stacking tandem layers by solution-processing is addressed. The devices are fabricated via solution and dry-lamination in ambient conditions with parallel processing steps. The method of fabricating the individual polymeric cells, the steps needed to laminate them together with a common CNT cathode, and then provide some representative results are described. These results demonstrate ionic gating of the CNT electrode to create a common cathode and addition of current and efficiency as a result of the lamination procedure.

A method of fabricating, in ambient conditions, organic photovoltaic tandem devices in a parallel configuration is presented. These devices feature an air-processed, semi-transparent, carbon nanotube common cathode.

A method of fabricating organic photovoltaic (OPV) tandems that requires no vacuum processing is presented. These devices are comprised of two ...

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 ...

Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and non-destructively reveals the hydrogen density distribution at surfaces, at interfaces, and in the volume of solid materials with high depth resolution. The technique applies a 15N ion beam of 6.385 MeV provided by an electrostatic accelerator and specifically detects the 1H isotope in depths up to about 2 &#956;m from the target surface. Surface H coverages are measured with a sensitivity in the order of ~1013 cm-2 (~1% of a typical atomic monolayer density) and H volume concentrations with a detection limit of ~1018 cm-3 (~100 at. ppm). The near-surface depth resolution is 2-5 nm for surface-normal 15N ion incidence onto the target and can be enhanced to values below 1 nm for very flat targets by adopting a surface-grazing incidence geometry. The method is versatile and readily applied to any high vacuum compatible homogeneous material with a smooth surface (no pores). Electrically conductive targets usually tolerate the ion beam irradiation with negligible degradation. Hydrogen quantitation and correct depth analysis require knowledge of the elementary composition (besides hydrogen) and mass density of the target material. Especially in combination with ultra-high vacuum methods for in-situ target preparation and characterization, 1H(15N,&#945;&#947;)12C NRA is ideally suited for hydrogen analysis at atomically controlled surfaces and nanostructured interfaces. We exemplarily demonstrate here the application of 15N NRA at the MALT Tandem accelerator facility of the University of Tokyo to (1) quantitatively measure the surface coverage and the bulk concentration of hydrogen in the near-surface region of a H2 exposed Pd(110) single crystal, and (2) to determine the depth location and layer density of hydrogen near the interfaces of thin SiO2 films on Si(100).

We illustrate the application of 1H(15N,&#945;&#947;)12C resonant nuclear reaction analysis (NRA) to quantitatively evaluate the density of hydrogen atoms on the surface, in the volume, and at an interfacial layer of solid materials. The near-surface hydrogen depth profiling of a Pd(110) single crystal and of SiO2/Si(100) stacks is described.

Nuclear reaction analysis (NRA) via the resonant 1H(15N,&#945;&#947;)12C reaction is a highly effective method of depth profiling that quantitatively and ...

Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution for future high-speed reentry missions. But despite the advancements made since Apollo, heat flux prediction remains an imperfect science and engineers resort to safety factors to determine the TPS thickness. This goes at the expense of embarked payload, hampering, for example, sample return missions. 
Ground testing in plasma wind-tunnels is currently the only affordable possibility for both material qualification and validation of material response codes. The subsonic 1.2MW Inductively Coupled Plasmatron facility at the von Karman Institute for Fluid Dynamics is able to reproduce a wide range of reentry environments. This protocol describes a procedure for the study of the gas/surface interaction on ablative materials in high enthalpy flows and presents sample results of a non-pyrolyzing, ablating carbon fiber precursor. With this publication, the authors envisage the definition of a standard procedure, facilitating comparison with other laboratories and contributing to ongoing efforts to improve heat shield reliability and reduce design uncertainties.
The described core techniques are non-intrusive methods to track the material recession with a high-speed camera along with the chemistry in the reactive boundary layer, probed by emission spectroscopy. Although optical emission spectroscopy is limited to line-of-sight measurements and is further constrained to electronically excited atoms and molecules, its simplicity and broad applicability still make it the technique of choice for analysis of the reactive boundary layer. Recession of the ablating sample further requires that the distance of the measurement location with respect to the surface is known at all times during the experiment. Calibration of the optical system of the applied three spectrometers allowed quantitative comparison. At the fiber scale, results from a post-test microscopy analysis are presented.

Development of new ablative materials and their numerical modeling requires extensive experimental investigation. This protocol describes procedures for material response characterization in plasma flows with the core techniques being non-intrusive methods to track the material recession along with the chemistry in the reactive boundary layer by emission spectroscopy.

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution ...

Preparation of Liquid-exfoliated Transition Metal Dichalcogenide Nanosheets with Controlled Size and Thickness: A State of the Art Protocol

We summarize recent advances in the production of liquid-exfoliated transition metal dichalcogenide (TMD) nanosheets with controlled size and thickness. Layered crystals of molybdenum disulphide (MoS2) and tungsten disulphide (WS2) are exfoliated in aqueous surfactant solution by sonication. This yields highly polydisperse mixtures containing nanosheets with broad size and thickness distributions. However, for most purposes, specific sizes (in terms of both lateral dimension and thickness) are required. For example, large and thin nanosheets are desired for (opto) electronic applications, while laterally small nanosheets are interesting for catalytic applications. Therefore, post-exfoliation size selection is an important step that we address here. We provide a detailed protocol on the efficient size selection in large quantities by liquid cascade centrifugation and the size and thickness quantification by statistical microscopic analysis (atomic force microscopy and transmission electron microscopy). The comparison of MoS2 and WS2 shows that both materials are size-selected in a similar way by the same procedure. Importantly, the dispersions of size-selected nanosheets show systematic changes in their optical extinction spectra with size due to edge and confinement effects. We show how these optical changes are related quantitatively to the nanosheets dimensions and describe how mean nanosheets length and layer number can be extracted reliably from the extinction spectra. The exfoliation and size selection protocol can be applied to a broad range of layered crystals as we have previously demonstrated for graphene, gallium sulphide (GaS) and black phosphorus.

A protocol for the liquid exfoliation of layered materials to nanosheets, their size selection and size measurement by microscopic and spectroscopic techniques is presented.

We summarize recent advances in the production of liquid-exfoliated transition metal dichalcogenide (TMD) nanosheets with controlled size and thickness. ...

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 ...

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 ...