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 length is used for sample preparation. Ensure that the size of plastic mold is larger than the ceramic particle.</li>
	</ol>
	</li>
	<li>Molding the model concrete
	<ol>
		<li>Weigh 1,000 g of cement and 350 g of water with an electronic balance (the designed water to cement mass ratio is 0.35).</li>
		<li>Wipe the 5 L mixing pot with a wet towel to moisten it. Add 350 g of water and 1,000 g of cement into the mixing pot sequentially. Place the mixing pot on the mixer and raise it to the stirring position.</li>
		<li>Mix at 65 rpm for 90 s, and let the mixture stand still for 30 s. During this period, scrape off the paste on the inner wall of the pot. Then, mix at 130 rpm for another 60 s.</li>
		<li>Remove the pot from the mixer and put the ceramic particle into the paste, manually mixing it with the cement paste thoroughly.</li>
		<li>Half fill the mold with well mixed fresh cement paste.</li>
		<li>Place the ceramic particle on the top surface of the cement paste and fill the rest of the mold with cement paste. Wipe off excess cement paste with a scraper knife and vibrate the mold on a vibrating table for 1 min at 50 &#177; 3 Hz.</li>
		<li>Seal the mold surface with cling film to prevent moisture evaporation.</li>
	</ol>
	</li>
	<li>Curing
	<ol>
		<li>Cure the specimen in a curing room for 24 h (20 &#177; 1 &#176;C and 95% &#177; 5% relative humidity).</li>
		<li>Remove the specimen from the mold and further cure the specimen for 28 d under the same environmental conditions.</li>
	</ol>
	</li>
</ol>
2. Scanning electron microscopy preparation
<ol>
	<li>Determination of the ceramic particle inside the matrix
	<ol>
		<li>Scan the specimen with X-ray computed tomography to obtain a stack of slices31.</li>
		<li>Roughly choose the slice where the ceramic particle appears to be largest. Fit the boundary of the ceramic particle with a circle and determine the center of the circle as the geometrical center of the ceramic particle. Due to the gray value difference between cement matrix and ceramic particle, a rough boundary of the particle appears on each CT slice (Figure 1).</li>
	</ol>
	</li>
	<li>Cutting
	<ol>
		<li>Cut the cubic specimen into two parts through the geometrical center of the ceramic particle in a cutting machine. Figure 132 is a schematic map showing the cutting direction. 
		NOTE: The ceramic particle was split into two equal parts, while the specimen was not cut into two exactly equal halves. If the ceramic particle is in the exact center of the cubic specimen, the specimen will be split into two equal halves. However, in a real situation, the ceramic particle typically is not in the exact center of the specimen.</li>
	</ol>
	</li>
	<li>Hydration termination
	<ol>
		<li>Immerse the two parts into isopropyl alcohol (&#8805;99.5%) for 3 days at room temperature to remove the unbounded water and terminate the internal hydration process. Replace the isopropyl alcohol solution every 24 h.</li>
		<li>Place the two parts in the vacuum drying even for 7 days to dry the sample at temperature of 40 &#176;C.</li>
	</ol>
	</li>
	<li>Solidifying the microstructure
	<ol>
		<li>Use a finger to smear the inner surface of two cylindrical plastic molds (31 mm in diameter and 25 mm in height) with demolding paste. The molds are all bottom removable.</li>
		<li>Place each piece of the sample into each mold with the surface to be examined facing downward.</li>
		<li>In a paper cup, weigh 50 g of low viscosity epoxy resin and add another 5 g of hardener. Manually stir the mixture with a wooden stick for 2 min.</li>
		<li>Put the mold into the cold mounting machine along with the paper cup with the mixture.</li>
		<li>Start the vacuum on the cold mounting machine and pour the epoxy resin into the mold until it merges with each sample.</li>
		<li>Keep the mold in the cold mounting machine for 24 h until the epoxy resin hardens.</li>
		<li>Remove the bottom of each mold and squeeze out the sample. Store the sample in a vacuum drying oven.</li>
	</ol>
	</li>
	<li>Grinding and polishing
	<ol>
		<li>Grind the sample with SiC paper and alcohol as a lubricant on an automatic polishing machine at the speed of 300 rpm in the following sequence for 3 min each: 180 grit, 300 grit, 600 grit, and 1200 grit.</li>
		<li>Attach the flannelette to the turntable of the automated polishing machine.</li>
		<li>Polish the sample on the flannelette with diamond paste of 3 &#956;m, 1 &#956;m, and 0.25 &#956;m for 15 min at the speed of 150 rpm, each.</li>
		<li>Remove the debris in an ultrasonic cleaner with alcohol as the cleaning solvent after each grinding and polishing step.</li>
		<li>Store each sample in a plastic box of similar size to the sample with each surface to be examined facing up to avoid cause any scratches on the testing surface.</li>
		<li>Keep the boxes containing the samples in a vacuum dry oven32. 
		NOTE: The grinding and polishing process could be completed on an automated polishing machine and at most 6 samples could be polished at the same time. The grinding and polishing time should be carefully chosen to obtain an extremely smooth surface for the SEM without creating height differences between the cement paste and the aggregate. A typical sample is shown in Figure 232.</li>
	</ol>
	</li>
</ol>
3. Backscattered image acquisition and processing
<ol>
	<li>Acquisition
	<ol>
		<li>Spray a thin layer of gold foil on the surface to be examined in a vacuum environment with an automatic sputter coater.</li>
		<li>Place a strip of adhesive tape on the side of the sample to connect the testing surface and opposite surface and place the sample on the test bench with the testing surface facing upward.</li>
		<li>Move the sample to focus the lens on region 1 as labelled in Figure 232.</li>
		<li>Vacuum the SEM and change to backscattered electron mode. Set the magnification at 1,000x and carefully adjust the brightness and contrast before capturing images.</li>
		<li>Move the lens along the direction of the aggregate boundary to another position of the aggregate and take another image. Repeat this moving and imaging process at least 15 times so that enough images can be obtained for statistical analysis.</li>
		<li>Move the lens to region 2 and region 3 and repeat the imaging process. 
		NOTE: Each image should include three phases: the matrix, the aggregate, and the ITZ. Since ITZ is a narrow section existing between another two phases and hard to be distinguished, each image should include both the cement matrix and the aggregate.</li>
	</ol>
	</li>
	<li>Processing
	<ol>
		<li>Pre-treat the image with a best fit and 3 x 3 median filter three times to reduce the noise and enhance the boundary of different phases on ImageJ.</li>
		<li>Manually capture the boundary of the ceramic particle and cut off this part from the original image using ImageJ.</li>
		<li>Roughly determine the upper threshold value of pore phases by setting different threshold values and segmenting the image to compare with the original one.</li>
		<li>Obtain the gray-scale distribution of the remaining part of the image. Choose two approximatively linear parts of the distribution curve just around the roughly determined upper threshold value of pore phases. Fit these two parts with linear curve and the intersection point will be set as the exact upper threshold value of this image (see Figure 3c32).</li>
		<li>Use this value to do the segmentation and compare the binary image with original gray-scale image for final threshold value determination.</li>
		<li>Convert the gray-scale image to a binary image with white (gray value = 255) representing pore phase and black (gray value = 0) representing solid phases. 
		NOTE: The exact determination of threshold value is called the overflow point method33 since the brightness and contrast are kept the same for different images obtained from same sample. Once the upper threshold value is precisely determined, this value could be applied to other images obtained from the same sample.</li>
	</ol>
	</li>
</ol>
4. Data processing
<ol>
	<li>ITZ thickness determination
	<ol>
		<li>Delineate twenty 20 successive strips that are 5 &#956;m in width (use the included strip_delineation.m file), along the captured boundary in the direction of starting from aggregate surface and going into the bulk paste (see Figure 3d32).</li>
		<li>Count the number of pixels with a gray value lower than the threshold in each strip and normalize the values by the number of total voxels contained in each strip. Each normalized value will be viewed as the porosity of each strip.</li>
		<li>Repeat the counting and normalization process for all the images. Average the porosity profiles of the same strip number from different images.</li>
		<li>Draw the porosity distribution graph as a function of distance away from aggregate surface. Determine the inflection point on the curve where porosity become stable as the thickness of the ITZ. 
		NOTE: The number of strips and width of each strip could vary; make sure that the total width of the delineated strips includes all of the ITZ. According to previous research, the ITZ thickness ranges between 20-50 &#956;m13. Even in some model concrete samples with an enlarged ITZ, this value does not exceed 70 &#956;m34,35.</li>
	</ol>
	</li>
	<li>Aggregate surface roughness (SR) characterization
	<ol>
		<li>Save the manually captured boundary as a curve. Fit the irregular boundary with both straight line and circle arc according to the Eq. (1) and Eq. (2) based on least square algorithm. 
		<img align="center" alt="Equation 1" src="/files/ftp_upload/60245/60245eq1.jpg" /> (1) 
		<img align="center" alt="Equation 2" src="/files/ftp_upload/60245/60245eq2.jpg" /> (2) 
		with (a,b) being the center of the fitting circle.</li>
		<li>Define the deviations between original irregular boundary and fitting smooth curve as the surface roughness (SR).</li>
		<li>For straight line, calculate the SRs by averaging the absolute value of the perpendicular distance of the center of each pixel on the boundary to the fitting line: 
		<img align="center" alt="Equation 3" src="/files/ftp_upload/60245/60245eq3.jpg" /> (3) 
		with n being the number of pixels included in each boundary and (xi, yi) being the coordinates of the ith pixel on the boundary.</li>
		<li>For a circle arc, define SRC as: 
		<img align="center" alt="Equation 4" src="/files/ftp_upload/60245/60245eq4.jpg" /> (4)</li>
		<li>Compare the value of SRS and SRC for each boundary and determine the minimum value as the final surface roughness for this curve (use the included surface_roughness_calculation.m file). 
		NOTE: The surface roughness of boundary should be defined against a smooth baseline curve. Both straight line and circle line were used for the following reason. Though the boundary of the spherical ceramic particle appears like a circle in 2D, some local regions appear to be more appeal to a straight line.</li>
	</ol>
	</li>
	<li>K-means clustering
	<ol>
		<li>Define a slope index (SL) to describe the porosity gradient within the interfacial transition zone according to the Eq. (5). 
		<img align="center" alt="Equation 5" src="/files/ftp_upload/60245/60245eq5.jpg" /> (5) 
		where &#966;max is the value of the porosity in the first strip (0 &#956;m to 5 &#956;m) and &#966;min is the value of the porosity in the sixth strip (25 &#956;m to 30 &#956;m).</li>
		<li>Combine the SR and SL of each boundary to be an observation. And for total n boundaries and ITZs, there exist n observations to be saved as a cluster {(SR1,SL1),(SR2,SL2), ... , (SRn,SLn)}.</li>
		<li>Apply a K-means clustering36,37 algorithm (use the included k_means_clustering.m file) to all the observations and subdivide them into 2 clusters: rough and smooth aggregate surface group, respectively.</li>
		<li>Average the porosity distributions of ITZ in rough and smooth cluster, respectively. Compare the average porosity distribution between two clusters. 
		NOTE: Herein, K-means clustering is a method of vector quantization, which is originally used in signal processing and currently widely applied to cluster analysis in data mining. The aim of the method is to subdivide the observations into 2 or more subgroups.</li>
	</ol>
	</li>
</ol>

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R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+advances+in+X-ray+microtomography+applied+to+materials.">Recent advances in X-ray microtomography applied to materials.</a> International Materials Reviews. 53 (3), 129-181 (2013).</li><li>Lyu, K., Garboczi, E. J., She, W., Miao, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+rough+vs.+smooth+aggregate+surfaces+on+the+characteristics+of+the+interfacial+transition+zone.">The effect of rough vs. smooth aggregate surfaces on the characteristics of the interfacial transition zone.</a> Cement and Concrete Composites. 99, 49-61 (2019).</li><li>Wong, H. S., Head, M. K., Buenfeld, N. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pore+segmentation+of+cement-based+materials+from+backscattered+electron+images.">Pore segmentation of cement-based materials from backscattered electron images.</a> Cement &amp; Concrete Research. 36 (6), 1083-1090 (2006).</li><li>Liao, K. -. Y., Chang, P. -. K., Peng, Y. -. N., Yang, C. -. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+study+on+characteristics+of+interfacial+transition+zone+in+concrete.">A study on characteristics of interfacial transition zone in concrete.</a> Cement and Concrete Research. 34 (6), 977-989 (2004).</li><li>Barnes, B. D., Diamond, S., Dolch, W. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+contact+zone+between+portland+cement+paste+and+glass+&#8220;aggregate&#8221;+surfaces.">The contact zone between portland cement paste and glass &#8220;aggregate&#8221; surfaces.</a> Cement &amp; Concrete Research. 8 (2), 233-243 (1978).</li><li>Hamerly, G., Elkan, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alternatives+to+the+k-means+algorithm+that+find+better+clusterings.">Alternatives to the k-means algorithm that find better clusterings.</a> Proceedings of the eleventh international conference on Information and knowledge management, ACM. , 600-607 (2002).</li><li>Celebi, M. E., Kingravi, H. A., Vela, P. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> A comparative study of efficient initialization methods for the k-means clustering algorithm. , 200-210 (2013).</li><li>Lu, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+mortars+using+real-shaped+sand+particles+and+uniform+thickness+interfacial+transition+zones:+Artifacts+seen+in+2D+slices.">Three-dimensional mortars using real-shaped sand particles and uniform thickness interfacial transition zones: Artifacts seen in 2D slices.</a> Cement and Concrete Research. , (2018).</li><li>Gao, Y., De Schutter, G., Ye, G., Huang, H., Tan, Z., Wu, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Porosity+characterization+of+ITZ+in+cementitious+composites:+Concentric+expansion+and+overflow+criterion.">Porosity characterization of ITZ in cementitious composites: Concentric expansion and overflow criterion.</a> Construction and Building Materials. 38, 1051-1057 (2013).</li><li>Celebi, M. E., Kingravi, H. A., Vela, P. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+comparative+study+of+efficient+initialization+methods+for+the+k-means+clustering+algorithm.">A comparative study of efficient initialization methods for the k-means clustering algorithm.</a> Expert Systems with Applications. 40 (1), 200-210 (2013).</li></ol>

We hereby confirm that this manuscript is our original work and all the authors listed have approved the manuscript and have no interest conflicts on this paper.

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).

<table><tbody><tr><td>Auto Sputter Coater</td><td>Cressington</td><td>108 Auto/SE</td><td></td></tr><tr><td>Automatic polishing machine</td><td>Buehler</td><td>Phoenix4000</td><td></td></tr><tr><td>Brush</td><td>Huoniu</td><td>3#</td><td></td></tr><tr><td>Cement</td><td>China United Cement Corporation</td><td>P.I. 42.5</td><td></td></tr><tr><td>Cement paste mixer</td><td>Wuxi Construction and Engineering</td><td>NJ160</td><td></td></tr><tr><td>Ceramic particle</td><td>Haoqiang</td><td>&amp;Phi;15 mm</td><td></td></tr><tr><td>Cling film</td><td>Miaojie</td><td>65300</td><td></td></tr><tr><td>Cold mounting machine</td><td>Buehler</td><td>Cast N&#039; Vac 1000</td><td></td></tr><tr><td>Conductive tape</td><td>Nissin Corporation</td><td>7311</td><td></td></tr><tr><td>Cup</td><td>Buehler</td><td>20-8177-100</td><td></td></tr><tr><td>Cutting machine</td><td>Buehler</td><td>Isomet 4000</td><td></td></tr><tr><td>Cylindrical plastic mold</td><td>Buehler</td><td>20-8151-100</td><td></td></tr><tr><td>Diamond paste</td><td>Buehler</td><td>00060210, 00060190, 00060170</td><td></td></tr><tr><td>Diesel oil</td><td>China Petroleum</td><td>0#</td><td></td></tr><tr><td>Electronic balance</td><td>Setra</td><td>BL-4100F</td><td></td></tr><tr><td>Epoxy resin</td><td>Buehler</td><td>20-3453-128</td><td></td></tr><tr><td>Hardener</td><td>Buehler</td><td>20-3453-032</td><td></td></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...

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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 ...

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8.0K Views.  Southeast University. 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.

Video: Determination of Aggregate Surface Morphology at the Interfacial Transition Zone ITZ

Characterization of Surface Modifications by White Light Interferometry: Applications in Ion Sputtering, Laser Ablation, and Tribology Experiments

In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. From the measured surface, 3D topographic maps can be subsequently analyzed using a variety of software packages to extract the information that is needed.
In this article we describe how white light interferometry, and optical profilometry (OP) in general, combined with generic surface analysis software, can be used for materials science and engineering tasks. In this article, a number of applications of white light interferometry for investigation of surface modifications in mass spectrometry, and wear phenomena in tribology and lubrication are demonstrated. We characterize the products of the interaction of semiconductors and metals with energetic ions (sputtering), and laser irradiation (ablation), as well as ex situ measurements of wear of tribological test specimens.
Specifically, we will discuss:
<ol class="lroman">
	<li>Aspects of traditional ion sputtering-based mass spectrometry such as sputtering rates/yields measurements on Si and Cu and subsequent time-to-depth conversion.</li>
	<li>Results of quantitative characterization of the interaction of femtosecond laser irradiation with a semiconductor surface. These results are important for applications such as ablation mass spectrometry, where the quantities of evaporated material can be studied and controlled via pulse duration and energy per pulse. Thus, by determining the crater geometry one can define depth and lateral resolution versus experimental setup conditions.</li>
	<li>Measurements of surface roughness parameters in two dimensions, and quantitative measurements of the surface wear that occur as a result of friction and wear tests.</li>
</ol>
Some inherent drawbacks, possible artifacts, and uncertainty assessments of the white light interferometry approach will be discussed and explained.

White light microscope interferometry is an optical, noncontact and quick method for measuring the topography of surfaces. It is shown how the method can be applied toward mechanical wear analysis, where wear scars on tribological test samples are analyzed; and in materials science to determine ion beam sputtering or laser ablation volumes and depths.

In materials science and engineering it is often necessary to obtain quantitative measurements of surface topography with micrometer lateral resolution. ...

Measurement of Aggregate Cohesion by Tissue Surface Tensiometry

Rigorous measurement of intercellular binding energy can only be made using methods grounded in thermodynamic principles in systems at equilibrium. We have developed tissue surface tensiometry (TST) specifically to measure the surface free energy of interaction between cells. The biophysical concepts underlying TST have been previously described in detail1,2. The method is based on the observation that mutually cohesive cells, if maintained in shaking culture, will spontaneously assemble into clusters. Over time, these clusters will round up to form spheres. This rounding-up behavior mimics the behavior characteristic of liquid systems. Intercellular binding energy is measured by compressing spherical aggregates between parallel plates in a custom-designed tissue surface tensiometer. The same mathematical equation used to measure the surface tension of a liquid droplet is used to measure surface tension of 3D tissue-like spherical aggregates. The cellular equivalent of liquid surface tension is intercellular binding energy, or more generally, tissue cohesivity. Previous studies from our laboratory have shown that tissue surface tension (1) predicts how two groups of embryonic cells will interact with one another1-5, (2) can strongly influence the ability of tissues to interact with biomaterials6, (3) can be altered not only through direct manipulation of cadherin-based intercellular cohesion7, but also by manipulation of key ECM molecules such as FN8-11 and 4) correlates with invasive potential of lung cancer12, fibrosarcoma13, brain tumor14 and prostate tumor cell lines15. In this article we will describe the apparatus, detail the steps required to generate spheroids, to load the spheroids into the tensiometer chamber, to initiate aggregate compression, and to analyze and validate the tissue surface tension measurements generated.

We describe a method of measuring binding energy, expressible as tissue surface tension, between cells within 3D tissue-like aggregates. Differences in tissue surface tension have been demonstrated to correlate with invasiveness of lung, muscle, and brain tumors, and are fundamental determinants of establishing spatial relationships between different cell types.

Rigorous measurement of intercellular binding energy can only be made using methods grounded in thermodynamic principles in systems at equilibrium.  We ...

Bioengineering

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 ...

Visually Based Characterization of the Incipient Particle Motion in Regular Substrates: From Laminar to Turbulent Conditions

Two different experimental methods for determining the threshold of particle motion as a function of geometrical properties of the bed from laminar to turbulent flow conditions are presented. For that purpose, the incipient motion of a single bead is studied on regular substrates that consist of a monolayer of fixed spheres of uniform size that are regularly arranged in triangular and quadratic symmetries. The threshold is characterized by the critical Shields number. The criterion for the onset of motion is defined as the displacement from the original equilibrium position to the neighboring one. The displacement and the mode of motion are identified with an imaging system. The laminar flow is induced using a rotational rheometer with a parallel disk configuration. The shear Reynolds number remains below 1. The turbulent flow is induced in a low-speed wind tunnel with open jet test section. The air velocity is regulated with a frequency converter on the blower fan. The velocity profile is measured with a hot wire probe connected to a hot film anemometer. The shear Reynolds number ranges between 40 and 150. The logarithmic velocity law and the modified wall law presented by Rotta are used to infer the shear velocity from the experimental data. The latter is of special interest when the mobile bead is partially exposed to the turbulent flow in the so-called hydraulically transitional flow regime. The shear stress is estimated at onset of motion. Some illustrative results showing the strong impact of the angle of repose, and the exposure of the bead to shear flow are represented in both regimes.

Two different methods for characterizing the incipient particle motion of a single bead as a function of the sediment bed geometry from laminar to turbulent flow are presented.

Two different experimental methods for determining the threshold of particle motion as a function of geometrical properties of the bed from laminar to ...

Pore-scale Imaging and Characterization of Hydrocarbon Reservoir Rock Wettability at Subsurface Conditions Using X-ray Microtomography

In situ wettability measurements in hydrocarbon reservoir rocks have only been possible recently. The purpose of this work is to present a protocol to characterize the complex wetting conditions of hydrocarbon reservoir rock using pore-scale three-dimensional X-ray imaging at subsurface conditions. In this work, heterogeneous carbonate reservoir rocks, extracted from a very large producing oil field, have been used to demonstrate the protocol. The rocks are saturated with brine and oil and aged over three weeks at subsurface conditions to replicate the wettability conditions that typically exist in hydrocarbon reservoirs (known as mixed-wettability). After the brine injection, high-resolution three-dimensional images (2 &#181;m/voxel) are acquired and then processed and segmented. To calculate the distribution of the contact angle, which defines the wettability, the following steps are performed. First, fluid-fluid and fluid-rock surfaces are meshed. The surfaces are smoothed to remove voxel artefacts, and in situ contact angles are measured at the three-phase contact line throughout the whole image. The main advantage of this method is its ability to characterize in situ wettability accounting for pore-scale rock properties, such as rock surface roughness, rock chemical composition, and pore size. The in situ wettability is determined rapidly at hundreds of thousands of points. 
The method is limited by the segmentation accuracy and X-ray image resolution. This protocol could be used to characterize the wettability of other complex rocks saturated with different fluids and at different conditions for a variety of applications. For example, it could help in determining the optimal wettability that could yield an extra oil recovery (i.e., designing brine salinity accordingly to obtain higher oil recovery) and to find the most efficient wetting conditions to trap more CO2 in subsurface formations.

This protocol is presented to characterize the complex wetting conditions of an opaque porous medium (hydrocarbon reservoir rock) using three-dimensional images obtained by X-ray microtomography at subsurface conditions.

In situ wettability measurements in hydrocarbon reservoir rocks have only been possible recently. The purpose of this work is to present a protocol to ...

Surface Properties of Synthesized Nanoporous Carbon and Silica Matrices

In this work, we report the synthesis and characterization of ordered nanoporous carbon material (also called ordered mesoporous carbon material [OMC]) with a 4.6 nm pore size, and ordered silica porous matrix, SBA-15, with a 5.3 nm pore size. This work describes the surface properties of nanoporous molecular sieves, their wettability, and the melting behavior of D2O confined in the differently ordered porous materials with similar pore sizes. For this purpose, OMC and SBA-15 with highly ordered nanoporous structures are synthesized via impregnation of the silica matrix by applying a carbon precursor and by the sol-gel method, respectively. The porous structure of investigated systems is characterized by an N2 adsorption-desorption analysis at 77 K. To determine the electrochemical character of the surface of synthesized materials, potentiometric titration measurements are conducted; the obtained results for OMC shows a significant pHpzc shift toward the higher values of pH, relative to SBA-15. This suggests that investigated OMC has surface properties related to oxygen-based functional groups. To describe the surface properties of the materials, the contact angles of liquids penetrating the studied porous beds are also determined. The capillary rise method has confirmed the increased wettability of the silica walls relative to the carbon walls and an influence of the pore roughness on the fluid/wall interactions, which is much more pronounced for silica than for carbon mesopores. We have also studied the melting behavior of D2O confined in OMC and SBA-15 by applying the dielectric method. The results show that the depression of the melting temperature of D2O in the pores of OMC is about 15 K higher relative to the depression of the melting temperature in SBA-15 pores with a comparable 5 nm size. This is caused by the influence of adsorbate/adsorbent interactions of the studied matrices.

Here we report the synthesis and characterization of ordered nanoporous carbon (with a 4.6 nm pore size) and SBA-15 (with a 5.3 nm pore size). The work describes the surface and textural properties of nanoporous molecular sieves, their wettability, and the melting behavior of D2O confined in the materials.

In this work, we report the synthesis and characterization of ordered nanoporous carbon material (also called ordered mesoporous carbon material [OMC]) ...

Chemistry

Multiscale Structures Aggregated by Imprinted Nanofibers for Functional Surfaces

Multiscale surface structures have attracted increasing interest owing to several potential applications in surface devices. However, an existing challenge in the field is the fabrication of hybrid micro-nano structures using a facile, cost-effective, and high-throughput method. To overcome these challenges, this paper proposes a protocol to fabricate multiscale structures using only an imprint process with an anodic aluminum oxide (AAO) filter and an evaporative self-aggregation process of nanofibers. Unlike previous attempts that have aimed to straighten nanofibers, we demonstrate a unique fabrication method for multiscale aggregated nanofibers with high aspect ratios. Furthermore, the surface morphology and wettability of these structures on various liquids were investigated to facilitate their use in multifunctional surfaces.

Presented is an easy method to fabricate nano-micro multiscale structures, for functional surfaces, by aggregating nanofibers fabricated using an anodic aluminum oxide filter.

Multiscale surface structures have attracted increasing interest owing to several potential applications in surface devices. However, an existing ...

Studying Surfactant Effects on Hydrate Crystallization at Oil-Water Interfaces Using a Low-Cost Integrated Modular Peltier Device

We introduce an approach to study the formation and growth of hydrates under the influence of nonionic surfactants. The experimental system includes a temperature regulator, visualization techniques, and inner pressure measurements. The temperature control system contains a low-cost, programmable temperature regulator made with solid-state Peltier components. Along with the temperature control system, we incorporated visualization techniques and internal pressure measurements to study hydrate formation and inhibition in the presence of nonionic surfactants. We studied the hydrate-inhibiting ability of nonionic surfactants (sorbitane monolaurate, sorbitane monooleate, PEG-PPG-PEG, and polyoxyethylenesorbitan tristearate) at low (i.e., 0.1 CMC), medium (i.e., CMC), and high (i.e., 10 CMC) concentrations. Two types of crystals were formed: planar and conical. Planar crystals were formed in plain water and low surfactant concentrations. Conical crystals were formed in high surfactant concentrations. The results of the study show that conical crystals are the most effective in terms of hydrate inhibition. Because conical crystals cannot grow past a certain size, the hydrate growth rate as a conical crystal is slower than the hydrate growth rate as planar crystal. Hence, surfactants that force hydrates to form conical crystals are the most efficient. The goal of the protocol is to provide a detailed description of an experimental system that is capable of investigating the cyclopentane hydrate crystallization process on the surface of a water droplet in the presence of surfactant molecules.

We present a protocol to study the formation of hydrates in the presence of nonionic surfactants on the interface of a water droplet submerged in cyclopentane. The protocol consists of building a low-cost, programmable, temperature regulator. The temperature control system is combined with visualization techniques and internal pressure measurements.

We introduce an approach to study the formation and growth of hydrates under the influence of nonionic surfactants. The experimental system includes a ...

Visualizing Solution Structure at Solid-Liquid Interfaces using Three-Dimensional Fast Force Mapping

Amongst the challenges for a variety of research fields are the visualization of solid-liquid interfaces and understanding how they are affected by the solution conditions such as ion concentrations, pH, ligands, and trace additives, as well as the underlying crystallography and chemistry. In this context, three-dimensional fast force mapping (3D FFM) has emerged as a promising tool for investigating solution structure at interfaces. This capability is based on atomic force microscopy (AFM) and allows the direct visualization of interfacial regions in three spatial dimensions with sub-nanometer resolution. Here we provide a detailed description of the experimental protocol for acquiring 3D FFM data. The main considerations for optimizing the operating parameters depending on the sample and application are discussed. Moreover, the basic methods for data processing and analysis are discussed, including the transformation of the measured instrument observables into tip-sample force maps that can be linked to the local solution structure. Finally, we shed light on some of the outstanding questions related to 3D FFM data interpretation and how this technique can become a central tool in the repertoire of surface science.

Here, we present a protocol for using three-dimensional fast force mapping - an atomic force microscopy technique - for visualizing solution structure at solid-liquid interfaces with the subnanometer resolution by mapping the tip-sample interactions within the interfacial region.

Amongst the challenges for a variety of research fields are the visualization of solid-liquid interfaces and understanding how they are affected by the ...

Atomic Force Microscopy Cantilever-Based Nanoindentation: Mechanical Property Measurements at the Nanoscale in Air and Fluid

An atomic force microscope (AFM) fundamentally measures the interaction between a nanoscale AFM probe tip and the sample surface. If the force applied by the probe tip and its contact area with the sample can be quantified, it is possible to determine the nanoscale mechanical properties (e.g., elastic or Young&#39;s modulus) of the surface being probed. A detailed procedure for performing quantitative AFM cantilever-based nanoindentation experiments is provided here, with representative examples of how the technique can be applied to determine the elastic moduli of a wide variety of sample types, ranging from kPa to GPa. These include live mesenchymal stem cells (MSCs) and nuclei in physiological buffer, resin-embedded dehydrated loblolly pine cross-sections, and Bakken shales of varying composition.
Additionally, AFM cantilever-based nanoindentation is used to probe the rupture strength (i.e., breakthrough force) of phospholipid bilayers. Important practical considerations such as method choice and development, probe selection and calibration, region of interest identification, sample heterogeneity, feature size and aspect ratio, tip wear, surface roughness, and data analysis and measurement statistics are discussed to aid proper implementation of the technique. Finally, co-localization of AFM-derived nanomechanical maps with electron microscopy techniques that provide additional information regarding elemental composition is demonstrated.

Quantifying the contact area and force applied by an atomic force microscope (AFM) probe tip to a sample surface enables nanoscale mechanical property determination. Best practices to implement AFM cantilever-based nanoindentation in air or fluid on soft and hard samples to measure elastic modulus or other nanomechanical properties are discussed.

An atomic force microscope (AFM) fundamentally measures the interaction between a nanoscale AFM probe tip and the sample surface. If the force applied by ...