Field Immersion Test Research Articles

Effects of Reaction Parameters on the Geometry and Crystallinity of Hydrothermally Synthesized ZnO Nanorods for Bio-Fouling Applications

In this present work, we have successfully synthesized vertical aligned ZnO nanorod arrays (ZnO NRs) on conductive stainless-steel substrate. These ZnO NRs were obtained by using a low temperature, low cost, and eco-friendly hydrothermal approach. The effect of the sol-gel deposited ZnO seed layer on the vertical alignment ZnO NRs has been thoroughly studied. Characterizations of the seed layer and the as-obtained nanorods were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), high-resolution transmission electron microscopy (HR-TEM), and water contact angles (WCA) measurement. SEM analysis shows that these nanorods were grown with a high uniformity and density over the entire substrate. TEM and XRD studies confirmed the hexagonal wurtzite structure of ZnO nanorods. Finally, field immersion tests using the optimized samples were conducted in a coastal sea environment to study biofouling settlement. To the best of our knowledge, there are few articles that investigate the influence of the seed layer deposited on stainless steel on the formation of vertically aligned nanorods for antifouling applications. The novelty of this work is manifested by optimizing the ZnO seed layer to obtain either thick or fine ZnO nanorods (NRs). Moreover, another novelty of this study is the use of the hydrothermal deposition of ZnO NRs on stainless steel for biofouling to replace paints in marine applications.

New method for the mechanical characteristics of self-weight collapsibility testing of loess foundation based on centrifugal model test

The mechanical characteristics of self-weight collapsibility of loess is mainly studied through laboratory tests, numerical simulations, and field immersion tests. However, a laboratory test under the lateral restraint condition cannot reflect the 3D stress state of soil and the influence of lateral extrusion deformation. The numerical simulation method is complex, and the calculation results depend on the accuracy of the constitutive model of loess deformation. Although the field immersion test produces results consistent with the stress and deformation conditions of actual foundations, the test cycle is long, and the cost is high. To overcome these issues, based on the strong self-weight collapsible loess in Ili, Xinjiang, and the variation laws of its physical and mechanical properties along the buried depth, a site is generalized and layered, and typical soil layers are selected to prepare a centrifugal model. A centrifugal model test is then conducted on the self-weight collapsible loess foundation. Taking the regional correction coefficient as the index, the rationality of the new method is verified by comparing the results of the centrifugal model test with those of the laboratory test and field immersion test.

Development, Optimization, Biological Assays, and In Situ Field Immersion of a Transparent Piezoelectric Vibrating System for Antifouling Applications

This paper presents the development and experimentations of transparent vibrating piezoelectric micromembranes dedicated to protecting immersed measurement instruments from marine biofouling. As any surface immersed is subject to the adhesion and settlement of organisms, especially in seawater, transparent materials quickly become opaque, resulting in deteriorated accuracy for optical sensors. According to this, we developed a transparent vibrating membrane to promote biofouling detachment in order to reduce the data quality drift and the frequency of maintenance operations on deployed optical sensors. In the first part, the design, the materials, and the steps to manufacture demonstrators are described. Then, the electromechanical characterizations of the demonstrators are carried out and interpreted with the support of FEM simulations. The last part describes the laboratory bioassays and the field immersion tests. Laboratory bioassays assess the antifouling potential of the vibrating piezoelectric membranes by exposing their surface to a suspended bacterial solution. In situ assays allow the membrane to perform in the Mediterranean Sea to assess their effectiveness in real conditions. Laboratory bioassays showed a great potential against the adhesion and settlement of a bacterial solution, while in situ tests confirmed the antifouling effect of piezoelectric vibrating micromembrane. Nevertheless, in situ experimentations revealed troubles with the piezo driver actuating the vibrating membranes, and tests should be carried out again with an improved piezo driver to reveal the full potential of the vibrating membranes. These are the first steps to set up an efficient antifouling vibrating system for immersed optical sensors.

What governs marine fouling assemblages on chemically-active antifouling coatings?

From an environmental perspective, there is a need to reduce the amount of biocides in chemically-active antifouling (AF) coatings, as these biocides can cause severe damage to marine life. In this study, six active molecules known as booster biocides were added at 3 wt% in solvent and aqueous-based acrylic paints. DCOIT, dichlofluanid, zinc pyrithione, copper pyrithione, tralopyril and zineb were used alone and mixed with a lower amount of copper (I) oxide and copper thiocyanate (10 wt%) than is currently used or with zinc oxide fillers. Field immersion tests were carried out in the Atlantic Ocean (Ste Anne du Portzic) and the Mediterranean Sea (Toulon), with contrasting physicochemical properties of water and macrofoulers' biodiversity. Microscopic analyses showed that AF coatings reduced the bacterial density differently for short immersion times at Ste Anne du Portzic. After four/five months of immersion, results, including multidimensional analyses, showed first specific patterns in the macrofoulers' assemblages depending on the site. In addition, the structure of macrofoulers' assemblages was affected by the biocide itself and by the combination of the biocide and the binder. When efficient, AF coatings appeared to decrease the richness with a strongest effect at Toulon. DCOIT was the most performing booster biocides whatever the immersion site and the polymer binder used. DCOIT was found to be efficient against marine bacteria and macrofoulers at Ste Anne du Portzic. The combination of zinc pyrithione with ZnO fillers in an aqueous-based AF paints exhibited the highest activity in the Mediterranean Sea over 16 months of immersion.

Cement-Improved Wetting Resistance of Coarse Saline Soils in Northwest China

Abstract Wetting-induced collapse of coarse saline soil foundations is a frequently encountered problem in the inland basin of Northwest China, but this particular behavior and relevant treatment have not been given adequate attention. Specimens treated by silicate cement were used in wetting collapse testing at conventional foundation loads, with five cement contents and four curing durations considered. The results indicate that in the case of no curing, the collapsible deformation during wetting declines at higher cement contents, and a stepwise development of deformation was noticed over the wetting duration. Specimens treated by cement after curing exhibit a decrease in the compressive deformation during wetting, and part of them show volume expansion instead. The complex hydrolysis and hydration reaction of cement in the process of curing primarily accounts for this. Moreover, the collapsibility coefficient varies within a narrow range in the noncuring case, proving the limited influence of cement inclusion; however, a gentle range, from 2.0 to 4.0 %, can be found after curing, beyond which it slightly varies. An elastoplastic model was established, incorporating a variable boundary seepage equation, and was then used for modeling a field immersion test. The rationality of the model was verified by comparing the measured and simulated results, including the degree of saturation and vertical displacement. The optimal depth and width for cement treatment was discussed in view of the practical engineering.

Modeling of wetting deformation of coarse saline soil with an improved von Wolffersdorff model

Assessment of wetting-induced deformation of coarse saline soil is required to facilitate the settlement control of infrastructures such as the transmission lines in Northwest China. The coarse saline soil exhibits high internal friction angle like common gravels and the cohesion up to 34.6 kPa, as revealed by direct shear tests. Laboratory wetting tests indicate that significant deformation occurs after water immersion, and the higher the water content, the lower the wetting deformation (or the lower the wetting collapsibility coefficient), and the shorter it takes to reach the deformation stability standard (0.01 mm/h). An improved von Wolffersdorff model and water-solute coupled transport model were used to simulate the settlement of coarse saline soil foundation during field immersion test. The effective wetting range (Sr > 60%) rapidly expands in coarse saline soil layer after water immersion, from bulb-shaped wetting front to disc-shaped, like the profiles of pore water pressure. Solute moves synchronously with water, primarily in the mode of convective diffusion. Compared with the limited horizontal deformation, settlement of foundation mainly occurs in the vertical direction, and increases with stepwise load.

Study on the method for determination of the maximum depth of loess collapsible under overburden pressure

Determination of the maximum depth of loess collapsible under overburden pressure is an important issue in the mechanics of loess and engineering research. The maximum depth of loess collapsible under overburden pressure is determined by testing the coefficient of collapsibility under overburden pressure, which differs from a trial pit field immersion test. Such a field test, however, is costly and therefore inadvisable for wide application in engineering practice. To identify a new laboratory test method for determination of the depth of loess collapsible under overburden pressure, loess samples were collected from the north suburb of Xi’an City, Shaanxi Province, China. Compression tests and tests of the coefficient of collapsibility (also referred to as hydrocollapse) under overburden pressure (also referred to as saturated self-weight stress) were conducted on these samples, and then their pore volumes and pore ratios were measured. From an in-depth analysis of the test results, a method was proposed for determination of the depth of loess collapsible under overburden pressure, namely the depth can be determined based on the variation of pore volumes or pore ratios with depth. The results from this paper for determination of the depth of loess collapsible under overburden pressure, which were verified by examples, are highly consistent with those from field tests. The method proposed in this paper is not only feasible but also less expensive and requires less time for test completion compared with field tests. Therefore, the method should be further investigated and considered for wider application.

A new method for evaluating loess collapsibility and its application

Collapsibility affects loess engineering stability. Currently, there are two methods used to determine the collapsibility of loess: the traditional indoor collapsibility test (indoor test) method and the field immersion test (field test) method. However, for the same loess site, the collapse values under overburden pressure obtained by the two methods are quite different. For sites that cannot be tested in situ, it is easy to misjudge the collapsibility of the loess foundation when depending only on indoor test results. To improve the accuracy of the indoor collapsibility determination, the characteristics of the compression curves obtained from confined compression tests at six different loess sites are analyzed in this paper. The compression curves of loess under different states are normalized and described by the composite power exponential model. The collapsibility of loess is closely related to its structure. A new method for analyzing and evaluating the collapsibility of loess is proposed; the method combines the relationship between the compression characteristics and initial structural properties of loess and the relationship between the initial structural properties and physical comprehensive indexes. To verify the applicability and accuracy of the new method, the collapse values under overburden pressure of two test sites along the Xi'an Metro Line 5 were calculated using the physical indexes of loess at different depths and compared with the values calculated from the indoor test and field-measured values. The results show that the calculated value of the new method is closer to the measured value of the field test than is the calculated value of the indoor test, and the new method can correctly determine the collapsibility type and grade of the site. The new method provides a simple and feasible means by which to correctly and quickly evaluate site collapsibility in loess engineering, which is beneficial for conducting loess site collapsibility evaluations under full operation to develop and implement the measures of foundation treatment in loess areas. The method can be used as a reference at loess sites where field tests cannot be performed.

Studies of Deformation Properties of Collapsible Loess Foundation under Overburden Pressure with Large Thickness by Centrifugal Model Test

At present, laboratory test and field immersion test are the primary methods to study the collapsibility characteristics of loess foundation. However, the stress state of laboratory test usually does not conform to the actual in-site situation, while the field immersion tests are expensive and difficult to operate. Thus, a new economical and efficient method which can reflect the actual engineering is urgently needed. Centrifugal model test, which is the best physical model test, has been extensively used in various fields of geotechnical engineering. However, centrifugal model test is seldom used in the simulation of collapsibility characteristics of loess foundation. In this paper, centrifugal model tests of natural water content foundation and saturated foundation are carried out for the collapsible loess with strong self-weight collapsibility located in Yili Region in Xinjiang, China. The collapsible deformation of loess foundation based on double-line method is obtained. The results show that the amount of foundation collapsibility simulated by low head saturation method is the closest to that of field immersion test, which verifies the feasibility of using centrifugal model test to simulate collapsible deformation of Loess foundation.

Experimental study on settling characteristics of thick self-weight collapsible loess in Xinjiang Ili region in China using field immersion test

To study the settling characteristics of Ili loess, a field immersion test was implemented on thick collapsible loess with seepage holes to speed up the collapse. The loess at the test site belongs to the Q3eol stratum and had a thickness of 30 m. The on-site settlement, the degree of saturation, and other observations, such as surface cracks and dolinas, were continuously monitored. The experimental results show that Ili loess is a typically collapsible eolian soil with a large thickness, strong water sensitivity, low anti-erosion capability, and strong self-weight collapsibility. The collapsibility of the Ili loess was basically eliminated by the field immersion test. One primary reason was the significant reduction in the numerous trellis pores. In comparison with other similar tests, a much higher settling rate and self-weight collapsible settlement were observed. The correction coefficient of collapsibility for Ili loess is 1.64, which is calculated as the measured self-weight collapsible settlement divided by the calculated value. It is a key parameter for evaluating the loess collapsibility in the area. A four-stage settling trend was characterized; it is distinguishable from other regular five-stage models. It was confirmed that the pre-immersion method with seepage holes is an effective method of foundation treatment for the Ili loess region.

Polymer brushes on structural surfaces: a novel synergistic strategy for perfectly resisting algae settlement.

The current paper reports a novel model of a marine antibiofouling surface based on polymer brushes on a wrinkled silicone elastomer. Polymer brushes (POEGMA and PSPMA) were grafted via surface-initiated atom transfer radical polymerization (SI-ATRP). Successful grafting was verified with various characterization techniques including infrared spectroscopy, X-ray photoelectron spectroscopy and contact angle measurements. A series of laboratory static and dynamic bioassays as well as field immersion tests were carried out to systematically investigate the relationship between surface chemistry, surface topography and antifouling properties. The results indicated that the adhesion of marine organisms was strongly influenced by the surface chemistry composition and surface topography structure. The synergistic effect of the surface chemistry, surface topography and bulk properties of the substrates endowed the new marine coatings with excellent antifouling properties.

Comparison studies on the anticorrosion and overall performance of solvent/water based epoxy-copper reinforced composite coatings

The influence of using two types of carrier agent namely, water and solvent, on the overall performance of epoxy resin has been investigated. Furthermore, four different loading rates of copper pigments (Cu) have been successfully embedded into two developed polymeric matrices and the changes occurred in the structure, thermal, fouling ability, morphology, and the anticorrosion performance have been studied. Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), field immersion test, scanning electron microscope (SEM), and electrochemical impedance spectroscopy (EIS) were used to evaluate the formulated coating systems. The results revealed that, the incorporation of Cu pigments did not significantly affect the efficiency of the room temperature curing process and further led to enhancement on the thermal stability of both developed epoxy resins. However, utilizing Cu pigments with solvent based epoxy (SB) showed better antifouling and anticorrosion properties compered to Cu composites prepared with water based epoxy resin (WB). The electrochemical behavior up to 30 days of immersion in 3.5% NaCl solution confirmed that the SB resin loaded with Cu pigments at 10% PVC, SB 10, demonstrated excellent barrier and anticorrosion properties. Neat WB coating (WB 0) was found to have the best performance among all WB coating systems.

Charged hydrophilic polymer brushes and their relevance for understanding marine biofouling

The resistance of charged polymers to biofouling was investigated by subjecting cationic (PDMAEMA), anionic (PSPMA), neutral (PHEMA-co-PEG10MA), and zwitterionic (PSBMA) brushes to assays testing protein adsorption; attachment of the marine bacterium Cobetia marina; settlement and adhesion strength of zoospores of the green alga Ulva linza; settlement of barnacle (Balanus amphitrite and B. improvisus) cypris larvae; and field immersion tests. Several results go beyond the expected dependence on direct electrostatic attraction; PSPMA showed good resistance towards attachment of C. marina, low settlement and adhesion of U. linza zoospores, and significantly lower biofouling than on PHEMA-co-PEG10MA or PSBMA after a field test for one week. PDMAEMA showed potential as a contact-active anti-algal coating due to its capacity to damage attached spores. However, after field testing for eight weeks, there were no significant differences in biofouling coverage among the surfaces. While charged polymers are unsuitable as antifouling coatings in the natural environment, they provide valuable insights into fouling processes, and are relevant for studies due to charging of nominally neutral surfaces.

Poly(dimethyl siloxane) (PDMS) network blends of amphiphilic acrylic copolymers with poly(ethylene glycol)-fluoroalkyl side chains for fouling-release coatings. II. Laboratory assays and field immersion trials

Amphiphilic copolymers containing different amounts of poly(ethylene glycol)-fluoroalkyl acrylate and polysiloxane methacrylate units were blended with a poly(dimethyl siloxane) (PDMS) matrix in different proportions to investigate the effect of both copolymer composition and loading on the biological performance of the coatings. Laboratory bioassays revealed optimal compositions for the release of sporelings of Ulva linza, and the settlement of cypris larvae of Balanus amphitrite. The best-performing coatings were subjected to field immersion tests. Experimental coatings containing copolymer showed significantly reduced levels of hard fouling compared to the control coatings (PDMS without copolymer), their performance being equivalent to a coating based on Intersleek 700™. XPS analysis showed that only small amounts of fluorine at the coating surface were sufficient for good antifouling/fouling-release properties. AFM analyses of coatings under immersion showed that the presence of a regular surface structure with nanosized domains correlated with biological performance.

Bioassays and field immersion tests: a comparison of the antifouling activity of copper-free poly(methacrylic)-based coatings containing tertiary amines and ammonium salt groups

This paper focuses on the activity spectrum of three dimethylalkyl tertiary amines as potential active molecules and the corresponding ammonium salt-based antifouling (AF) paints. Bioassays (using marine bacteria, microalgae and barnacles) and field tests were combined to assess the AF activity of coatings. Bioassay results demonstrated that the ammonium salt-based paints did not inhibit the growth of microorganisms (except the dimethyldodecylammonium-based coatings) and that the tertiary amines were potent towards bacteria, diatoms, and barnacle larvae at non-toxic concentrations (therapeutic ratio, LC50/EC50, < 1). The results from field tests indicated that the ammonium salt-based coatings inhibited the settlement of macrofouling and the dimethylhexadecylammonium-based coatings provided protection against slime in comparison with PVC blank panels. Thus, results from laboratory assays did not fully concur with the AF activity of the paints in the field trial.

Microbiologically Induced Corrosion of UNS N04400 in Seawater

Abstract Laboratory and field immersion tests were conducted on UNS N04400 (Mone 400) to assess its susceptibility toward microbial attack in Arabian Gulf seawater. Specimens were exposed to chlorinated and nonchlorinated seawater for periods up to four months. Other tests included exposure of UNS N04400 to a prepared culture of sulfate-reducing bacteria (SRB). The results indicated that SRB attack initiated beneath a black sulfide-rich deposit, overlaid by a green chloride-rich deposit, and a beige-colored calcareous scale was on all specimen surfaces after long exposure periods. The black layer was comprised mainly of one or more iron-nickel sulfides (Fe, Ni)xSy and nickel sulfide (Ni3S4), whereas the green layer was essentially CuCl2 × 3Cu(OH)2 with a low concentration of NiCl2. These deposits were in the form of nodules scattered on the surface, and, when removed, circular attacked areas or cavities were revealed. Scanning electron microscopy examinations of these areas indicated severe intergranular ...