Immersion Time Research Articles

Performance of magnesium oxysulfate (MOS) cement prepared by MgCl2·6 H2O replacing MgSO4·7 H2O

Despite the influence of Cl- on the properties of cement-based materials, water containing Cl- is more convenient for manufacturing cement-based materials in special areas such as islands and reef construction, compared to fresh water. However, research on the effects of Cl- on the properties of magnesium oxysulfate (MOS) cement was limited. In this paper, MOS cement was prepared by replacing MgSO4·7 H2O with MgCl2·6 H2O to investigate the effect of Cl- on the evolution of MOS cement properties. The mechanical properties, water resistance, phase composition, and microstructure of MOS cement were analyzed. When the replacement rate of MgSO4·7 H2O with MgCl2·6 H2O reached 5 %, MOS cement achieved its highest compressive strength of 77.5 MPa after curing for 90 days, despite a reduction in flexural strength due to MgO hydration. After immersion in water, the trend of compressive strength change in MOS cement remained insensitive to increasing immersion time. During the curing process, Cl- facilitated the formation of hexagonal Mg(OH)2 by participating in the hydration products formation process of MOS cement. Hexagonal Mg(OH)2 contributed to matrix construction and became connected with the 5Mg(OH)2·MgSO4·7 H2O phase. Additionally, Cl- promoted the formation of the modified 5Mg(OH)2·MgSO4·7 H2O phase, known as Mg-S-O-H-Cl phase. After immersion in water, the Mg-S-O-H-Cl phase displayed stability, showcasing their capacity to maintain compressive strength relative stability despite adverse factors such as ions leaching (including Mg2+, SO42-, and Cl-) and the phase transformation of MgO.

Water-rock interfacial softening model of cemented soft rock: An experimental and numerical study

Cemented soft rock is prone to softening when exposed to water, and its mechanical properties deteriorate rapidly, which is an important reason to induce the instability and failure of engineering soft rock mass. The softening mechanism of soft rock is essentially the deterioration of microstructure caused by the change of water-rock interface. Considering the general characteristics of soft rock, the microstructural evolution characteristics and element loss over varying immersion time are then compared and analyzed. The Interfacial Cemented Bonding (ICB) structure is proposed to describe the evolution of water-rock interface. Based on the diffusion theory, the theoretical equation describing the evolution of water-rock interface is derived and compared with the experimental results. The meso-softening damage factor (MSDF) of soft rock is proposed and introduced into a numerical method to establish a strength degradation discrete element method (SD-DEM) model. The results show that the softening process of soft rock is accompanied by the shedding and suspension of particles and the dissolution of soluble substances. Besides, the softening of soft rock has obvious nonlinear dynamic characteristics. The fitting degree between the theoretical values and the experimental results is relatively high, which verifies the reliability and rationality of the dissolution-diffusion interfacial softening model. The numerical results are in good agreement with the experimental ones. This study provides a new idea for understanding the mechanism of water-induced softening characteristics and strength degradation of soft rock.

Optical and Electrical Properties of Spin Coated Bilayer Graphene

Graphene is a 2D material with high transparency, high carrier mobility, and high electrical conductivity [1-4]. In this work, a thin graphene layer was coated on Si through spin coating, and dip coating technique.Graphene ink was prepared by expanding the graphite flakes through microwave irradiation followed by ultrasonic liquid phase exfoliation. 5 mg of the resulting graphene was dispersed in 1 ml of IPA through a probe sonication technique to obtain the graphene suspension/ink. To form the graphene/Si junction, pieces of 3 x 3 cm2 of n-type Si were used. In addition, same size of fused silica were used to measure the reflectance of deposited graphene. The graphene layer in the first sample was formed by spin coating 40 µl of graphene ink on the Si and the fused silica at a speed of 200 rpm for 40 s. The second sample was prepared by dip coating technique, where 13 ml of the graphene ink was added to 47 ml of IPA, followed by dipping Si and the fused silica pieces with a speed of 20 mm/min till they immersed completely and were kept for 1 min and were moved up at the same speed and dried at room temperature. This dip-coating process was repeated 10 times for each sample.The morphology of graphene-coated area was analyzed using the SEM technique. The SEM images of the spin-coated shows that the surface is fully covered with graphene flakes of different sizes stacked on each other with varied orientations, this shows the ability to obtain a continuous coating of graphene by spin coating. Also, Hall effect measurements were performed, and it showed that the conductivity of the Si substrate was 1.95x10-2 ohm-1cm-1, and it increased to 2.74 ohm-1cm-1 after adding the graphene. Finally, the reflectance of the graphene on fused silica was measured using a UV-VIS spectrophotometer, and it showed that the reflectance decreased from 8% to 4% in the range from 360 to 860 nm after adding the graphene.For dip-coated sample, the SEM image shows some voids, and empty areas linked with by graphene structure with a width of few microns, this shows that the dip-coating process needs to be optimized to get a full coverage of the surface. The electrical measurement of this sample showed that the conductivity increased to 2.66 ohm-1cm-1 after the dip coating of graphene. For the reflectance measurements, it was observed that the graphene has decreased the reflectance to 6-7% in the range from 360 to 860 nm.Finally, spin coating at higher speed, and less amount of graphene can be tested, to obtain a thinner graphene layer. For the dip coating process, higher graphene concentration in IPA, and longer immersion time will be investigated to get a better coverage.

Standardization of Process Variables for the Development of Osmo-dehydrated Coconut Haustorium

Background: Coconut (Cocos nucifera L.) is considered a highly valuable and beneficial perennial crop in our country. The basal portion of the coconut embryo enlarges during germination and forms a spongy structure, haustorium, which is an excellent source of essential nutrients. Since consumer preference is shifting towards healthy food and processed coconut products have immense scope in this sector, the study was conducted to standardize the process variables for osmo-dehydration of coconut haustorium and to evaluate the nutritional qualities of the osmo-dehydrated product. Methods: The present study involved the development of osmo-dehydrated coconut haustorium by standardizing the process variables, viz., osmotic solution concentration and immersion time. Mass transfer, physical, biochemical and sensory parameters were analysed to evaluate the nutritional qualities and consumer acceptance. Result: The results on biochemical properties revealed that an increase in concentration and time of immersion increased TSS, total sugar, reducing sugar, ash and mineral content. The process variables were standardized for the development of osmo-dehydrated coconut haustorium with optimum mass transfer characters, better nutritional qualities and consumer acceptance, which has application in the food industry.

A green zwitterionic bi-continuous membranes prepared by dual-bath procedure for mitigating biofouling during bacterial removal from water

This work explores the possibility of forming green microfiltration antifouling membranes based on polyvinylidene fluoride (PVDF) and a zwitterionic copolymer derivative of sulfobetaine methacrylate (SBMA), utilizing gamma-valerolactone (GVL) as the solvent and a mixture of ethanol and water as non-solvents. Efforts were initially focused on adjusting the immersion time of the matrix polymer in alcohol alone to obtain a porous structure, and 15 s were sufficient to achieve a symmetric, open porous morphology. Next, the polymer/copolymer/solvent blend was characterized. While it did not show the characteristics of a fully miscible system, DLS and visual observations revealed the obtaining of a homogeneous (relatively narrow particle size) and transparent to translucent system. Thus, membranes could be cast, and were shown to be stable. The addition of the copolymer maintained the physical characteristics of microfiltration membranes, but an FT-IR analysis revealed its effect on the dominant crystalline polymorph (switching from β to α). The membrane wettability was enhanced in an important extent with a dynamic water contact angle (WCA) gradually falling to < 40° (while the virgin membrane's WCA remained about 138° all test long), and a hydration capacity reaching about 530 mg/cm3 against <10 mg/cm3 for the virgin membrane. It reflected on the antifouling abilities of the membranes as tested using bovine serum albumin, fibrinogen, Escherichia coli, and Stenotrophomonas maltophilia, with relative decreases in adsorption during static tests measured to be 95 %, 70 %, 91 % and 98 %, respectively. Finally, compared to the virgin membrane, the modified membrane featured improved flux recovery (32 % vs. 11 %), significantly higher rejection (98.9 % vs. 89.1 %) and lower irreversible fouling tendency (68 % vs. 89 %) during cyclic water/bacterial solution filtration in dead-end mode, making it potentially suitable for addressing bacterial pollution in wastewater.

Development of a glycine-MWCNT nanohybrid via electropolymerization for enhanced electrochemical detection of diclofenac

In this study, electropolymerization of glycine (Gly) was carried out to enhance the sensitivity of the carbon paste electrode (CPE) blended with multi-walled carbon nanotubes (MWCNTs) for electroanalysis of diclofenac (DCF). Analytical applications and electrochemical performance were examined using various voltammetric methods, including differential pulse voltammetry and cyclic voltammetry. Atomic force, scanning electron microscopy, dispersive X-ray, X-ray diffraction, and Raman spectroscopy were used to ascertain the surface topology of the modifier. The modified sensor with high electrocatalytic properties could electrochemically oxidize DCF, resulting in an enhanced current compared to the bare CPE when an anodic peak was detected at 0.77 V peak potential for the bare CPE, consisting of 0.1 mM DCF and 2.11 µA peaks current. The working electrode CPE was then modified with MWCNT and glycine. For MWCNT/CPE, a peak was seen at 5.20 µA and 0.75 V, and a more intense peak was observed for poly(Gly)-MWCNT/CPE at 11.52 µA and 0.74 V. The poly(Gly)-MWCNT/CPE exhibited a five-fold enhancement of peak current compared to bare CPE. The modified electrode displayed fast electron transfer, reproducibility, and repeatability. The study explored how factors like immersion time, pH variation, scan speed, and substance concentration could influence the peak current of DCF. Methods such as differential pulse voltammetry and cyclic voltammetry were utilized to examine the electrochemical oxidation behavior of DCF. The concentration variation is 0.5 µM to 7.0 µM, and the detection limit was 7.96 × 10-8 M. The rate constant (ks) for the electrochemical process was 1.710 s-1. The DCF of pharmacological and biological test substances was measured using the constructed modified electrode.

Investigating intermittent immersion during osmotic dehydration of mango (Mangifera indica L. Moench). Part A: Determination of optimal conditions for mango (Mangifera indica L. Moench) dehydration impregnation by immersion (D2I) and intermittent immersion (D3I)

This work aimed to determine the optimum conditions for dehydration impregnation by immersion (D2I) and by intermittent immersion (D3I) of mango (Mangifera indica) slices measuring 4 × 1 × 1 cm3. To this end, the Doehlert response surface plan was used, with the following factors for D2I: the volume of D2I solution/fruit mass ratio (6/1–13/1 mL/g), the process time (120–360 min) and the Brix degree of the solution (45–65 °Brix) and with the following factors for D3I: immersion time (20–60 min), process time (60–300 min) and de-immersion time (7–25 min). The temperature was fixed according to literature at 35 °C. The optimum responses obtained for the D2I process were (47.63 ± 1.79) g/100 g (w-b) for water loss, and (6.67 ± 1.04) g/100 g (w-b) for solute gain, for optimum operating conditions of 6/1 mL/g; 245 min and 61.6°Brix respectively for the immersion ratio, process time and solute concentration of the hypertonic solution. The optimum responses obtained for D3I process were (47.98 ± 2.12) g/100 g (w-b) for water loss, and (4.31 ± 0.052) g/100 g (w-b) for solute gain (SG), for operating conditions of 21; 270; and 9 min, respectively for immersion time, process time and de-immersion time. The Student's t-test on the predicted and experimental optima of WL and SG revealed valuable insights for comparing these two processes. The present study will undoubtedly introduce a new dynamic to the osmotic dehydration systems for fruits and vegetables.

Syzygium polyanthum (Wight) Walp. leaf extract as a sustainable corrosion inhibitor for carbon steel in hydrochloric acidic environment

This study focuses on an investigation of the corrosion inhibition behavior of Syzygium polyanthum (Wight) Walp. leaf extract (SPWE) of carbon steel in 1.0 M hydrochloric acid medium. Electrochemical methods demonstrated a corrosion inhibition efficiency of 94.65 ± 0.94 % when 2000 ppm extract is added to the corrosive solution. Furthermore, surface analysis results indicated that with the absence of an inhibitor, the steel surface suffered severe corrosion, while the corrosion density was slow, and a film was observed on the surface after applying the SPWE into a corrosive environment. The film formed by the chemical and physical adsorption of compounds such as polyphenol, flavonoid, alkaloid, and tannin onto the carbon steel surface has been qualitatively and quantitatively analyzed in this study. Notably, increased immersion time and reaction temperature led to significant desorption of molecules, reflecting characteristic of physical adsorption. However, the corrosion inhibition efficiency of SPWE remained effective, particularly within the temperature range of 25–35 °C. Therefore, this study provides an efficient inhibitor for carbon steel corrosion in 1.0 M hydrochloric acidic environment that could be possibly added to the corrosion inhibitor system.

New aryl-himachalene benzylamines derivatives as eco-friendly corrosion inhibitors at low concentration for brass 62/38 in 200 ppm NaCl: Experimental, analyses and theoretical approach

This study investigates the inhibitory effect of eco-friendly synthesized aryl-himachalene benzylamines derivatives, namely (±)-N-((3,5,5,9-tetramethyl -6,7,8,9-tetrahydro-5H-benzo [7] annulen-2yl)methyl)aniline (AHB) and (±)-4-bromo-N-((3,5,5,9-tetramethyl-6,7,8,9-tetrahydro-5H-benzo[7]annulen-2-yl)methyl)aniline (AHBBR) at low concentration on the brass 62/38 (B62/38) corrosion in 200 ppm NaCl solution, employing electrochemical techniques, surface analyses and theoretical investigations. The experimental measurements indicated that these compounds exhibit as good inhibitions, where their inhibition efficiency growth with their concentrations, reaching 88.69 % and 93.35 % at 100 ppm AHB and AHBBR, respectively. I-E measurements designated that the tested products react like a mixed-inhibitor type. In addition, the EIS measurements showed the establishment of a protective layer on the B62/38 region. The effects of the temperature solution and immersion time on their performance were investigated. It is found that they decrease slowly with temperature, while they improve with the immersion time until 12 h. In the same way, it is found that these molecules react on B62/38 surface according to Langmuir isotherm adsorption. Complementary, SEM/EDX analysis established the development of an organic defending film on the B62/38 area, confirming the compound's potential as effective corrosion inhibitors. Finally, the theoretical investigations confirm the anti-corrosion character of the tested compounds according to their mode of adsorption.

OPTIMIZATION OF CONCENTRATION AND SOAKING TIME OF HARRIS HEMATOXYLIN IN DNA BAND EXAMINATION USING ELECTROPHORESIS

Background: Deoxyribonucleic acid (DNA) molecules can be effectively visualized when stained and observed under ultraviolet light during the electrophoresis process. The commonly used dye Ethidium bromide (EtBr) is considered hazardous due to its potential to cause mutations, cancer, and congenital disabilities. Various alternative dyes have been reported, one of which is hematoxylin. Hematoxylin compounds do not have mutagenic potential and are easier to apply than EtBr. However, there is no optimal variation in concentration and duration of staining for clear and effective visualization of DNA bands. Purpose: To find the concentration and staining time of harris hematoxylin staining for DNA bands from agarose gel electrophoresis. Method: An experimental method with a group comparison statistical design. The amplified DNA I6S rRNA gene from Escherichia coli (584 bp), which had undergone electrophoresis, was stained using harris hematoxylin dye at 0.01%; 0.02%; 0.03%; 0.04%; and 0.05% concentrations and immersion times soaking times of 10, 15, 20, and 30 minutes variations. The intensity of the DNA bands was analyzed using ImageJ. The staining power of the experimental groups was compared to the intensity of control dye and given a grading score of 1 - 4. The experiment was repeated twice, and the mean grading score was calculated. The highest mean value was considered the most optimal value. Result: A concentration of 0.02% showed relatively constant staining intensity for each soaking time. A mean value of 3.5 was obtained for a 0.01% concentration for 15 minutes. A 0.03% and 0.04% concentrations for 20 minutes. Conclusion: The highest mean value of 4 was obtained for Harris hematoxylin at 0.05% for 15 minutes.

ZnO Nanoparticles Enhance the Antimicrobial Properties of Two-Sided-Coated Cotton Textile.

Cotton textiles improved with metal oxide nanoparticles acquire additional features that may enhance their action against antimicrobial-resistant pathogens due to the unique properties and characteristics of the nanoparticles. The main objective of this work is to evaluate the antimicrobial features of two-sided-coated cotton textiles with ZnO nanoparticles. Nanoparticles were deposited using green chemistry technology with low-temperature oxygen plasma. ZnO particles formed stable structures on textile fibers. The optimal deposition parameters (150 W plasma power, 120 min immersion time) achieved the best effects against Gram-negative and Gram-positive bacteria and microscopic fungi. Two-sided-coated cotton with ZnO nanoparticles showed high antibacterial action on Gram-negative and Gram-positive bacteria. Modification with zinc oxide inhibited the growth of Candida albicans by more than half.

Solution-Induced surface modification and secondary grains growth for high-performance and stable perovskite solar cells

Enhancing the quality of perovskite layer and refining the interface between the perovskite layer and the hole transport layer (HTL) represent pivotal strategies for optimizing the efficiency and stability of perovskite solar cells (PSCs). We accomplished this by employing a solution isopropanol (IPA), capable of selectively dissolving residual unreacted methylammonium and formamidine salts on the perovskite surface while preserving the integrity of lead iodide. Through control of the immersion time, we facilitated secondary crystal growth on the top of perovskite film. The resultant treated film exhibited a markedly suitable bandgap position and a diminished presence of residual trips. The IPA-treated sample led to a noteworthy photovoltaic conversion efficiency (PCE) of 23.34 %, compared to 21.46 % efficiency for untreated control sample. Furthermore, under sustained illumination at AM 1.5G with 25 % relative humidity, the uncovered IPA-treated sample retained an impressive 92 % of their initial efficiency after 1000 h. Further scrutiny revealed that this solution-based treatment effectively passivated trips, enhanced perovskite film quality, established novel built-in electric fields, and mitigated charge carrier recombination. This work provides a simple perovskite film treatment approach that does not require complex molecular engineering and can be applied not only to PSCs but also to other perovskite optoelectronic devices.

Effective amendment of cadmium in water and soil before and after aging of nitrogen-doped biochar: Preparation optimization, removal efficiency and mechanism

Nitrogen-doped biochar (NBC) is a green material for remediating heavy metal pollution, but it undergoes aging under natural conditions, affecting its interaction with heavy metals. The preparation conditions of NBC were optimized using response surface methodology (RSM), and NBC was subjected to five different aging treatments to analyze the removal efficiency of Cd(II) and soil remediation capability before and after aging. The results indicated that NBC achieved optimal performance with a mass ratio of 5:2.43, an immersion time of 10.66 h, and a pyrolysis temperature of 900 °C. Aging diminished NBC's adsorption capacity for Cd(II) but did not change the main removal mechanism of monolayer chemical adsorption. Freeze-thaw cycles (FT), UV aging (L), and composite aging (U) treatments increased the proportion of bioavailable-Cd, and all aging treatments facilitated the conversion of potentially bioavailable-Cd to non-bioavailable-Cd. The application of NBC and five aged NBCs reduced the proportion of bioavailable-Cd in the soil through precipitation and complexation, increasing the proportion of non-bioavailable-Cd. Aging modifies the physicochemical properties of NBC, thus influencing soil characteristics and ultimately diminishing NBC's ability to passivate Cd in the soil. This study provides reference for the long-term application of biochar in heavy metal-contaminated environments.

Manufacture of phase diffraction gratings by acid immersion

In this work, the manufacturing, characterization, and optical testing of phase diffraction gratings is performed. The fabrication is carried out in a very simple way: by immersion of a common amplitude diffraction gratings on acid and a posterior chemical procedure. The process makes it achievable for almost any scientist, since expensive equipment is not required. We have tested three different acids and evaluated the engraving depth (phase retardation) in terms of the immersion time. With this analysis, phase diffraction gratings with the desired phase delay could be manufactured. The quality of the gratings has been evaluated by means of their profiles and histograms of the surface, using confocal microscopy. To conclude, we have measured the near-field behavior of one of the phase gratings and compared it with that obtained analytically, showing high agreement.

Underwater Acoustic Camouflage by Wettability Transition on Laser Textured Superhydrophobic Metasurfaces

AbstractThe superhydrophobicity of submerged surfaces typically pertains to the trapped air film at the liquid–solid interface, subject to wettability transitions from a Cassie–Baxter state to more unstable states that gradually collapse to high retention regimes, which are energetically more favorable. In this work, the dynamic evolution of those transient metastable states is correlated to the underwater acoustic performance of laser textured superhydrophobic surfaces, resolving the dependence of the ultrasound spectral response with the immersion time to capture the genuine contribution of the hierarchical subwavelength morphology, regardless of the air layer effects. Acoustic wave attenuation of the incident ultrasound energy is extensively quantified in transmission, accounting for instantaneous broadband sound blocking (&gt;30 dB) within the spectral range 0.5–1.5 MHz. As a result of the air layer detachment with the immersion time, transmission coefficients increase accordingly, while acoustic fields in reflection unexpectedly evolve toward stealthiness and naïve acoustic camouflage, mostly ascribable to dissipative mechanisms at air layer interfaces. The intrinsic decay of the air layer effect is tentatively determined at different frequencies, since quantitative understanding of the transient lifetime governing underwater surface wettability is critical to design stable superhydrophobic character of laser induced subwavelength metastructures on the most promising acoustic materials – from eco‐friendly natural to artificial.

Alkaloid extract of seed Citrullus colocynthis as novel green inhibitor for mild steel corrosion in one molar HCl acid solution: DFT and MC/MD approaches

The study was designed to explore the corrosion prevention capabilities of Citrullus colocynthis seeds alkaloid-rich extract (CSEA) on MS in a 1 M HCl environment by use of electrochemical and theoretical methods. Notably, Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization were used to probe the impact of immersion time and temperature. Energy-dispersive X-ray spectroscopy (EDX) and spanning electron microscopy (SEM) were used to confirm the presence of a protective layer on the substrate surface. Density functional theory (DFT) method was used to optimize the investigated species by use of B3LYP/6–31 + G(d, p) level of theory. The global and local quantum chemical reactivity descriptors were calculated to explore the inhibition corrosion efficiency and to identify the most favorable sites for electrophilic and nucleophilic attacks. Monte Carlo (MC) and molecular dynamics simulation (MDS) methods were used to study the interactions between corrosion inhibitor and metal surface. Noteworthy, results showed that CSEA exhibited an impressive inhibition efficiency, which reached 94.3% with a concentration of 2 g/L at 298 K. Potentiodynamic polarization revealed that the extract acted as a mixed-type inhibitor. Nyquist graphs showed that charge-transfer resistance and dæouble-layer capacitance both rised with increasing CSEA concentration, suggesting better inhibition efficiency. Notably, the Langmuir adsorption isotherm is well-aligned with the adsorption of inhibitor compounds. Importantly, all aforementioned theoretical methods were in agreement with the experimental findings. The outcome of the present work supported using Citrullus colocynthis seeds alkaloid-rich extract as ecofriendly agents to prevent corrosion.

Influence of the activation time of magnesium surfaces on the concentration of active hydroxyl groups and corrosion resistance

Magnesium alloys have been extensively studied as degradable biomaterials for clinical applications due to their biocompatibility and mechanical properties. However, their poor corrosion resistance can lead to issues such as osteolysis and the release of gaseous hydrogen. This study investigated the influence of the activation time of magnesium surfaces in a sodium hydroxide (NaOH) solution on the concentration of active hydroxyl groups and corrosion resistance. The results indicated that immersion time significantly influences the formation of a corrosion-resistant film and the distribution of surface hydroxyl groups. Specifically, specimens treated for 7.5 h exhibited the highest concentration of hydroxyl groups and the most uniform oxide film distribution. Electrochemical tests demonstrated capacitive behavior and passive surface formation for all evaluated times, with the 7.5-h immersion in NaOH yielding superior corrosion resistance, lower current density, and a more efficient and thicker protective film. SEM and EDS analyses confirmed increased formation of Mg(OH)₂ for samples treated for 5 and 7.5 h, while a 10-h treatment resulted in a brittle, porous layer prone to degradation. Statistical analysis using ANOVA and Fisher's LSD test corroborated these findings. The optimal 7.5-h alkali treatment enhanced magnesium's corrosion resistance and surface properties, making it a promising candidate for orthopedic implants. However, further studies are necessary to assess biocompatibility and physiological responses before clinical implementation.

Tribological behaviors and wettability evolution of phenolic resin-impregnated graphite materials under water immersion condition

This study investigated the tribological behaviors of two phenolic resin-impregnated graphite samples and one non-impregnated sample under dry and water immersion using a reciprocating testing device. The frictional configuration involved a steel hemisphere sliding against the surface of the graphite samples. The influence of water immersion time before each formal test on friction coefficients was discussed. The wettability evolution during the test processes and the difference in porosity, which could significantly affect water infiltrating into the sample matrix and frictional interfaces, were associated with the variation in tribological behaviors. The worn surface morphology and element analysis results indicated that the shallow valleys and pores on the surface of graphite were gradually filled by wear debris from both the graphite samples and the harder counterpart. Based on these experimental results, a tribological mechanism of the phenolic resin-impregnated graphite materials under water immersion was developed.

Effect of Aggregate-to-Binders Ratio on Water Resistance of Red-Mud-Modified Magnesium Phosphate Repair Mortar

The aggregate-to-binders ratio (A/Bs) is an important parameter for the design and preparation of repair mortars. In this paper, the influences of A/Bs on the physical and mechanical properties of red-mud-modified magnesium phosphate repair mortar (RMPM) were systematically investigated. By exploring the capillary absorption characteristics of RMPM, the effect mechanism of A/Bs on its water resistance and mechanical properties was further clarified. The results indicated that the fluidity of fresh RMPM reduced with an increase in A/Bs, and its setting time was first shortened and then prolonged. The compressive strength, flexural strength, interfacial bonding strength, and water resistance of RMPM increased and then decreased with the increasing A/Bs and reached the maximum when the A/Bs was 1.0. The capillary absorption of RMPM was a linear correlation with the square root of the immersion time, and whose slope, that is, the capillary absorption coefficient, and capillary porosity decreased and then increased with the increase in A/Bs. Capillary porosity had a linear relationship with the strength retention rate, which indicated that A/Bs produced a significant effect on the water resistance of RMPM by modifying its capillary pore characteristics. When the A/Bs was 1.0, RMPM had the lowest capillary absorption coefficient and capillary porosity, and thus possesses appropriate mechanical properties and water resistance.

Study of corrosion behaviour of polyurethane-ZnO/Zn composite coatings in NaCl solutions

In order to evaluate the corrosion performance of polyurethane-ZnO/Zn coatings for LY12 aluminium alloy sheets in 3.5 % NaCl solution. Firstly, the composite coatings were prepared and the optimum stick-fill ratio was obtained. Secondly, the corrosion characteristics were characterised by SEM, EDS and electrochemistry for different immersion times and the electrochemical behaviour was investigated by open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and kinetic potential polarisation curves (PP). The results show that the coating with a viscosity-fill ratio of 1:4 has a uniform distribution, the corrosion potential Ecorr is more positive, the corrosion current density icorr is the smallest, |Z|0.01Hz maintains the highest, and the coating has a good anti-corrosion performance. After soaking in 3.5 % NaCl solution for 20 days, the coating reaction resistance increased from 1.71 × 104 Ωcm2 to 6.59 × 1017 Ωcm2, and the self-corrosion current decreased from 5.12 × 10−5 A/cm2 to 5.01 × 10−7 A/cm2, indicating that the corrosion resistance of LY12 aluminium alloy sheet in the solution increased.