scholarly journals Development of a quantification method for fouling deposits using phosphorescence

2021 ◽  
Author(s):  
H. Deponte ◽  
W. Augustin ◽  
S. Scholl
Keyword(s):  
Surface Coverage ◽  
Surface Structures ◽  
New Method ◽  
Hydraulic Efficiency ◽  
Fouling Resistance ◽  
Structured Surfaces ◽  
Particulate Fouling ◽  
Quantification Method ◽  
Experimental Findings ◽  
Reduced Surface

AbstractParticulate fouling on structured surfaces is typically quantified using the integral thermal or mass-based fouling resistance. The observed geometries may be structures that can improve the heat transfer in heat exchangers (e.g., dimples), cavities in components, or more complex geometries. However, due to limited accessibility or the requirement for a locally resolved measurement, the existing quantification methods may not be applicable to structured surfaces. For this reason, a new method is needed for the quantification for fouling deposits. In this study, dimpled surfaces were evaluated by measuring the integral thermal and mass-based fouling resistance and comparing it with the local fouling resistance inside and around the dimple. This comparison was carried out online with the Phosphorescent Fouling Quantification method developed for this purpose, using phosphorescent particles to quantify the deposited mass. The mass-based fouling resistance can be calculated using computer-aided image analysis. The measurements for the evaluation were conducted on dimpled surfaces, which produced a characteristic fouling pattern. With the new method a reduced surface coverage from up to 33.3 % was observed, which led to lower fouling resistances downstream of the dimple compared to a plain surface. These results confirm earlier numerical and experimental findings, suggesting an advantage of dimpled surfaces over other surface structures with respect to thermo-hydraulic efficiency as well as reduced fouling. Thus, the Phosphorescent Fouling Quantification method provides the possibility of calculating values for local fouling resistances on structured surfaces, as well as the possibility of optimizing surface structures to minimize fouling propensity.

Hierarchical Nano/Micro-structured Surfaces with High Surface Area/Volume Ratios

2021 ◽  
pp. 1-36
Author(s):  
Ketki Lichade ◽  
Yizhou Jiang ◽  
Yayue Pan
Keyword(s):  
Surface Structure ◽  
Surface Area ◽  
Light Trapping ◽  
High Surface ◽  
High Surface Area ◽  
Three Dimensional ◽  
Structure Design ◽  
Surface Structures ◽  
Structured Surfaces ◽  
Design And Manufacture

Abstract Recently, many studies have investigated additive manufacturing of hierarchical surfaces with high surface area/volume (SA/V) ratios, and their performance has been characterized for applications in next-generation functional devices. Despite recent advances, it remains challenging to design and manufacture high SA/V ratio structures with desired functionalities. In this study, we established the complex correlations among the SA/V ratio, surface structure geometry, functionality, and manufacturability in the Two-Photon Polymerization (TPP) process. Inspired by numerous natural structures, we proposed a 3-level hierarchical structure design along with the mathematical modeling of the SA/V ratio. Geometric and manufacturing constraints were modeled to create well-defined three-dimensional hierarchically structured surfaces with a high accuracy. A process flowchart was developed to design the proposed surface structures to achieve the target functionality, SA/V ratio, and geometric accuracy. Surfaces with varied SA/V ratios and hierarchy levels were designed and printed. The wettability and antireflection properties of the fabricated surfaces were characterized. It was observed that the wetting and antireflection properties of the 3-level design could be easily tailored by adjusting the design parameter settings and hierarchy levels. Furthermore, the proposed surface structure could change a naturally-hydrophilic surface to near-superhydrophobic. Geometrical light trapping effects were enabled and the antireflection property could be significantly enhanced (>80% less reflection) by the proposed hierarchical surface structures. Experimental results implied the great potential of the proposed surface structures for various applications such as microfluidics, optics, energy, and interfaces.

Relaxations at GaN (1010) and (110) Surfaces

1996 ◽  
Vol 449 ◽  
Author(s):  
Alessio Filipetti ◽  
Manuela Menchi ◽  
Andrea Bosin ◽  
Giancarlo Cappellini
Keyword(s):  
Bond Length ◽  
Rotation Angle ◽  
Surface Structures ◽  
Small Energy ◽  
Zinc Blende ◽  
Length Contraction ◽  
Experimental Findings ◽  
Formation Energies ◽  
Surface Bond ◽  
Good Agreement

ABSTRACTWe present an ab-initio calculation of GaN wurtzite (1010) and zinc-blende (110) surface structures and formation energies. Our method employs ultrasoft pseudopotentials and plane-wave basis. These features enable us to obtain accurate results using small energy cut-off and large supercells. The (110) surface shows a Ga-N surface dimer rotation of ∼ 14°, i.e. about one half that of the ordinary III–V non-nitride compounds, and a 5% contraction of the surface bond-length (more than the double that occurring in GaAs). For the (1010) surface, a layer rotation angle of about 11° and a bond-length contraction of 6% has been found. Zinc-blende GaAs (110) and wurtzite ZnO (1010) surfaces have been studied as well, for the sake of comparison. GaAs results are in good agreement with the experimental findings. For ZnO a large bond contraction and a rotation angle of around 11% result. Thus, our findings place GaN closer in behaviour to the highly ionic II–VI compounds than to the non-nitride III–V semiconductors.

The Experimental Investigation of Fouling Phenomenon in Heat Exchangers by Heat Transfer Resistance Monitoring (HTRM) Method

2009 ◽  
Author(s):  
M. Izadi ◽  
D. K. Aidun ◽  
P. Marzocca ◽  
H. Lee
Keyword(s):  
Heat Transfer ◽  
Sodium Bicarbonate ◽  
Calcium Chloride ◽  
Heat Exchangers ◽  
Evaluation System ◽  
Quantitative Information ◽  
Fouling Resistance ◽  
Transfer Resistance ◽  
Accelerated Corrosion ◽  
Particulate Fouling

The aim of this paper is to describe a monitoring system for fouling phenomenon in tubular heat exchangers. This system is based on a physical model of the fouling resistance. A mathematical model of the fouling resistance is developed based on the applied thermal heat, the inside heat transfer coefficient, and geometrical characteristics of the heat exchanger under consideration. The resulting model is a function of measured quantities such as water and tube wall temperatures, fluid flow velocities, and some physical properties of the fluid flowing inside the tubes such as viscosity, conductivity, and density. An on-line fouling evaluation system was prepared and the heat transfer resistance for selected solutions was measured in real time by this system. The effect of concentration and chemical reactions on fouling is studied experimentally by using different contaminants such as sodium bicarbonate, calcium chloride, and their mixture. Accelerated corrosion was observed for the calcium chloride-0.4g/l solution due to the presence of chlorine ions. This corrosion-fouling can be mitigated by adding sodium bicarbonate. However, calcium carbonate is formed as the result of the chemical reaction between calcium chloride and sodium bicarbonate which activates two other fouling categories, particulate fouling and crystallization. The inside surface of the tube is analyzed by analytical microscopy after the experiment to investigate different fouling categories. Experimental results provide quantitative information of liquid-side fouling on heat transfer surfaces, and its effects on the thermal efficiency. Experimental data is significantly important for the design, and for formulating operating, and cleaning schedules of the equipment.

Application of variothermal heating concepts for the production of microstructured films using the extrusion embossing process

2012 ◽  
Vol 32 (2) ◽  
Author(s):  
Walter Michaeli ◽  
Stephan Eilbracht ◽  
Micha Scharf ◽  
Claudia Hartmann ◽  
Kirsten Bobzin ◽  
...  
Keyword(s):  
Temperature Profile ◽  
Large Scale ◽  
Cost Effective ◽  
Processing Parameters ◽  
Surface Structures ◽  
Structured Surfaces ◽  
Heating Systems ◽  
External Heating

Abstract The application of the extrusion embossing process is a fast and cost-effective way to produce large-scale films with structured surfaces. In principle, microscopic and macroscopic surface structures can be manufactured this way. Particularly for the fabrication of microscopic structures, the reproduction accuracy can be remarkably improved by applying variothermal heating concepts for the embossing roll. In this article, two possible heating concepts are investigated: one laser-based and another using an inductor. The generated temperature profile along the circumference of the embossing roll is studied, taking the material of the embossing roll as well as different processing parameters into account. Both external heating systems (laser vs. inductor) are tested and compared. Furthermore, the improvement of the accuracy of the replicated microstructures is examined.

scholarly journals Durable superoleophobic polypropylene surfaces

2016 ◽  
Vol 374 (2073) ◽  
pp. 20160193 ◽  
Author(s):  
Philip S. Brown ◽  
Bharat Bhushan
Keyword(s):  
High Temperature ◽  
Plastic Material ◽  
Polymer Surface ◽  
Polymer Surfaces ◽  
Surface Structures ◽  
Structured Surfaces ◽  
Mechanical Durability ◽  
Plastic Containers

Polypropylene (PP) is a popular plastic material used in consumer packaging. It would be desirable if such plastic containers were liquid repellent and not so easily fouled by their contents. Existing examples of superoleophobic surfaces typically rely on poorly adhered coatings or delicate surface structures, resulting in poor mechanical durability. Here, we report a facile method for creating superoleophobic PP surfaces via incorporation of nanoparticles (NPs) into the polymer surface. A solvent–NP–PP mixture was spin coated at high temperature to achieve the necessary roughness. Such surfaces were further functionalized with fluorosilane to result in a durable, super-repellent surface. They were also found to exhibit some repellency towards shampoos. This method of incorporating NPs into polymer surfaces could also prove useful in improving the anti-bacterial, mechanical and liquid-repellent properties of plastic devices. This article is part of the themed issue ‘Bioinspired hierarchically structured surfaces for green science’.

Wetting on Regularly Structured Surfaces from “Core−Shell” Particles: Theoretical Predictions and Experimental Findings

Langmuir ◽  
2008 ◽  
Vol 24 (20) ◽  
pp. 11895-11901 ◽  
Author(s):  
Alla Synytska ◽  
Leonid Ionov ◽  
Victoria Dutschk ◽  
Manfred Stamm ◽  
Karina Grundke
Keyword(s):  
Core Shell ◽  
Structured Surfaces ◽  
Theoretical Predictions ◽  
Shell Particles ◽  
Experimental Findings

scholarly journals In vitro cell migration quantification method for scratch assays

2019 ◽  
Vol 16 (151) ◽  
pp. 20180709 ◽  
Author(s):  
Ana Victoria Ponce Bobadilla ◽  
Jazmine Arévalo ◽  
Eduard Sarró ◽  
Helen M. Byrne ◽  
Philip K. Maini ◽  
...  
Keyword(s):  
Experimental Data ◽  
Cell Migration ◽  
Cell Monolayer ◽  
Leading Edge ◽  
New Method ◽  
Scratch Assay ◽  
Standard Methods ◽  
Migration Rates ◽  
Quantification Method

The scratch assay is an in vitro technique used to assess the contribution of molecular and cellular mechanisms to cell migration. The assay can also be used to evaluate therapeutic compounds before clinical use. Current quantification methods of scratch assays deal poorly with irregular cell-free areas and crooked leading edges which are features typically present in the experimental data. We introduce a new migration quantification method, called ‘monolayer edge velocimetry’, that permits analysis of low-quality experimental data and better statistical classification of migration rates than standard quantification methods. The new method relies on quantifying the horizontal component of the cell monolayer velocity across the leading edge. By performing a classification test on in silico data, we show that the method exhibits significantly lower statistical errors than standard methods. When applied to in vitro data, our method outperforms standard methods by detecting differences in the migration rates between different cell groups that the other methods could not detect. Application of this new method will enable quantification of migration rates from in vitro scratch assay data that cannot be analysed using existing methods.

scholarly journals Heterogeneous conversion of NO<sub>2</sub> and NO on HNO<sub>3</sub> treated soot surfaces

2004 ◽  
Vol 4 (5) ◽  
pp. 6747-6767
Author(s):  
J. Kleffmann ◽  
P. Wiesen
Keyword(s):  
Active Sites ◽  
Surface Coverage ◽  
Heterogeneous Reaction ◽  
High Surface ◽  
Product Formation ◽  
Atmospheric Humidity ◽  
Mixing Ratios ◽  
Upper Limit ◽  
Atmospheric Processing ◽  
Experimental Findings

Abstract. In the present study, the heterogeneous conversion of nitrogen oxide (NO) and nitrogen dioxide (NO2) was studied at atmospheric humidity levels on flame soot surfaces, which were treated with gaseous nitric acid (HNO3). In addition, the heterogeneous reaction of HNO3 on soot was investigated at atmospheric humidity. For the treatment of soot by pure HNO3 only reversible uptake with a surface coverage of ~1–2×1014 HNO3 cm−2 was observed for HNO3 mixing ratios in the range 250–800 ppbv. Only for higher HNO3 mixing ratios of >800 ppbv the formation of NO and NO2 was observed. The results were not affected by the addition of NO. In none of the experiments with HNO3 the formation of nitrous acid (HONO) was observed. For HNO3 mixing ratios <600 ppbv the upper limit yields for HONO, NO2 and NO were found to be <0.2%, <0.5% and <1%, respectively. Compared to untreated soot, the product formation of the reaction of NO2 with soot was not significantly affected when the soot surface was treated with gaseous HNO3 prior to the experiment. Only for high surface coverage of HNO3 the formation of HONO was suppressed in the initial phase of the reaction, probably caused by the blocking of active sites by adsorbed HNO3. Under the assumption that the experimental findings for the used model flame soot can be extrapolated to atmospheric soot particles, the results show that the reactions of HNO3 and HNO3+NO on soot surfaces are unimportant for a "renoxification" of the atmosphere and do not represent an atmospheric HONO source. In addition, the integrated HONO yield of ca. 1014 cm−2 in the reaction of NO2 with soot is not significantly influenced by simulated atmospheric processing of the soot surface by HNO3, and is still too small to explain HONO formation in the atmosphere.

High-resolution, extended views of membrane surfaces revealed by fracture-flip

1989 ◽  
Vol 47 ◽  
pp. 738-739
Author(s):  
Pedro Pinto da Silva
Keyword(s):  
High Resolution ◽  
Colloidal Gold ◽  
Cell Membranes ◽  
Freeze Fracture ◽  
Surface Structures ◽  
New Method ◽  
Deep Etching ◽  
Membrane Surfaces ◽  
Routine Identification ◽  
Freeze Etching

I will describe a new method — fracture-flip — that uses commercially available equipment to produce extended views of cell and membrane surfaces. The resolution of this new method permits the routine identification of surface structures down to 5 nm diameter. Moreover, in contrast to freeze-etching/deep-etching, extended views are easily obtained.Conceptally, fracture-flip derives from label-fracture, another method developed in my laboratory. With label-fracture we showed that, after freeze-fracture, the exoplasmic (E) halves of cell membranes are stabilized by, and remain attached to, their platinum/carbon replicas. This allows the observation of co-incident views of the Pt/C replica of the E face, and of the distribution of colloidal gold labeled receptors or antigens. This is the sequence of steps in fracture-flip:

scholarly journals Inversion of friction anisotropy in a bio-inspired asymmetrically structured surface

2018 ◽  
Vol 15 (138) ◽  
pp. 20170629 ◽  
Author(s):  
Halvor T. Tramsen ◽  
Stanislav N. Gorb ◽  
Hao Zhang ◽  
Poramate Manoonpong ◽  
Zhendong Dai ◽  
...  
Keyword(s):  
Gait Pattern ◽  
Surface Structures ◽  
Substrate Stiffness ◽  
Substrate Roughness ◽  
Friction Anisotropy ◽  
Anisotropic Friction ◽  
Structured Surfaces ◽  
Preferred Direction ◽  
Design Paradigm ◽  
Robotic Applications

Friction anisotropy is an important property of many surfaces that usually facilitate the generation of motion in a preferred direction. Such surfaces are very common in biological systems and have been the templates for various bio-inspired materials with similar tribological properties. So far friction anisotropy is considered to be the result of an asymmetric arrangement of surface nano- and microstructures. However, here we show by using bio-inspired sawtooth-structured surfaces that the anisotropic friction properties are not only controlled by an asymmetric surface topography, but also by the ratio of the sample–substrate stiffness, the aspect ratio of surface structures, and by the substrate roughness. Systematically modifying these parameters, we were able to demonstrate a broad range of friction anisotropies, and for specific sample–substrate combinations even an inversion of the anisotropy. This result highlights the complex interrelation between the different material and topographical parameters on friction properties and sheds new light on the conventional design paradigm of tribological systems. Finally, this result is also of great importance for understanding functional principles of biological materials and surfaces, as such inversion of friction anisotropy may correlate with gait pattern and walking behaviour in climbing animals, which in turn may be used in robotic applications.

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