Sliding Angle Values Research Articles

New insights into the mechanism causing the loss of anti-corrosion property of superhydrophobic titanium surfaces

In this paper, we provide new insights into the mechanism causing the loss of anti-corrosion property of superhydrophobic titanium (SHP Ti) during potentiodynamic polarization (PDP) measurements. The water contact angle and sliding angle values of the SHP Ti, produced by a facile two-step process: anodizing and coating, were >160° and 6±2°, respectively. The anodization of Ti resulted in randomly distributed micro-clusters of TiO2-xCly covering the Ti surface homogeneously while the low surface energy organic coatings were inhomogeneous in coverage and specifically distributed over the micro-clusters alone of the anodized titanium surface. The electrochemical impedance (EIS) analysis of the SHP CP-Ti samples has shown more than an order of magnitude improvement in their barrier /polarization resistance (Rp) values at ∼ 100 MΩ.cm2 suggesting the effectiveness of the SHP coatings as a barrier against corrosion in neutral chloride environments. However, the Rp values (∼ 10 M Ω.cm2) of the SHP coatings obtained from the PDP analysis were an order of magnitude lower than the Rp values derived from the EIS. SHP CP-Ti samples showed dual passive range behaviour with an initial narrow passive region due to the porous anodized TiO2-xCly layer while the later stage passivity due to the barrier TiO2 layer, where the outer anodized porous TiO2-xCly layer was less effective against corrosion in neutral chloride media. Detailed analysis showed that in PDP, the sample lost its SHP because of the permeation of electrolyte into the hierarchical surface, due to its sensitivity to polarization, owing to the lower thickness of the organic layers. The mechanism involved in the loss of SHP and the limitation of the PDP technique for the corrosion analysis of SHP / organic coatings on metal surfaces is highlighted.

Antibiofouling Slippery Liquid Impregnated Pulsed Plasma Poly(styrene) Surfaces

AbstractBiofouling is a major global environmental and economic challenge wherein organisms settle on solid surfaces submerged in natural waters. This leads to the spread of invasive marine species around the globe, accelerates surface deterioration through microbially‐induced corrosion, and inflates maritime vessel fuel consumption which leads to greater greenhouse gas emissions. In this study, pulsed plasma poly(styrene) nanocoatings impregnated with eco‐friendly liquids are produced that yield slippery surfaces through aromatic–aliphatic intermolecular interactions (water droplet contact angle hysteresis and sliding angle values ≈1–2°). The antibiofouling performance of these slippery surfaces is demonstrated using laboratory‐based marine bioassays and real‐world field trials in freshwater (pond water) and seawater (ocean) environments. Low‐cost and substrate‐independent pulsed plasmachemical deposition combined with eco‐friendly liquid impregnation provides a sustainable approach to tackling environmental biofouling.

Effect of adding coconut shell charcoal powder on clay impermeable layer small dam core material

Clay soil is widely chosen to be used as a waterproof core layer material in ponds because there is a tendency to have water-tight properties. However, in general conditions, clay soil has several weaknesses and causes problems in civil construction, such as low shear strength and high plasticity. The existence of this condition is certainly a consideration to improve the mechanical properties of the clay when it is to be used as a waterproof core layer in the reservoir. This effort is carried out to increase the shear strength of the soil and reduce its permeability so that it can meet the requirements as soil for an impermeable core layer. The permeability coefficient for the minimum pond core material is less than or equal to 1x10-6 cm/sec. In this study, coconut shell charcoal was used as a stabilizing agent for clay soil. The percentage variations of the coconut shell charcoal mixture used were 0%, 5%, 10%, 15%, and 20%. This study aims to determine the effect of coconut shell charcoal powder on the permeability coefficient, and the shear strength of clay soil which will be used as the core material of the watertight reservoir. The tests carried out in this study were atterberg limit testing, grain gradation analysis, compaction, shear strength, and permeability. Based on the results of testing with soil samples varying from a mixture of 0% to 20% coconut shell charcoal, it was found that the best addition of coconut shell charcoal for shear strength testing was a mixture variation of 15% with a cohesion value of 0.353 kg/cm2 and a mixture variation of 20 % with a sliding angle value of 43.2580. Whereas in the permeability test on the coconut shell charcoal mixture of 15% is the best addition of coconut shell charcoal with a permeability coefficient of 2.106x10-7 cm/second.

Low-cost superhydrophobic coating on aluminum alloy with self-cleaning and repellency to water-based mixed liquids for anti-corrosive applications

This work seeks to develop a low-cost superhydrophobic coating on 5052 aluminum alloy using a combination of methods. First, top-down with acid etching with dilute HCl solution for a few minutes. Second, bottom-up by simple deposition of layered double hydroxide (LDH) film; Third, chemical modification of the surface with stearic acid. Through the applied methodology, it is possible to obtain superhydrophobic coatings with a contact angle of 164° and sliding angles of 1°. The obtained coating also shows high repellency and low sliding angle value for different commercial liquid foods such as orange juice, grape juice, chocolate milk, iced tea, isotonic, and cola-based soda. The Tafel method reveals that corrosion inhibition efficiency is 97.7 % and 97.4 % after 24 h of exposure in 0.6 mol/L NaCl solution and cola-based soda medium (pH = 2,5), respectively. The immersion test for 21 days (3 weeks) in distilled water and NaCl solution (0.6 mol/L) shows a change of the wettability characteristic on the coated specimens to hydrophobic and hydrophilic at the end of the experiment, respectively. Future work intends to incorporate harder particles that can further improve the mechanical durability of the LDH-based superhydrophobic coating, aiming at the application as food contact materials.

Construction of superhydrophobic graphene-based coating on steel substrate and its ultraviolet durability and corrosion resistance properties

For the first time, a facile and environmentally friendly approach for producing high-quality graphene from the biomass of banana leaves is described in this paper. Two rough coats of Ni-graphene, Ni@G, and Ni-graphene doped with chromium, Ni@Cr-G, were created on steel substrates by electrostatic deposition. These coatings were then submerged in an ethanolic solution of myristic acid, MA, to produce a superhydrophobic, SHP, surface. The Raman spectra demonstrated that the generated graphene was of high quality. Fourier transform infrared spectroscopy findings confirm the modification of the Ni@G coating by MA, Ni@G@MA, and the modification of the Ni@Cr-G composite with MA, Ni@Cr-G@MA. The results of the scanning electron microscope revealed that the created SHP coatings have nanoscale features. The wettability results showed that the water contact angle values for Ni@G@MA and Ni@Cr-G@MA coatings are 158° and 168°, while the water sliding angle values for both coatings are 4.0 o and 1.0°, respectively. The atomic force microscopy results show that both Ni@G and Ni@Cr-G coatings increase the roughness of the steel. The chemical and mechanical stability of the Ni@Cr-G@MA coating was higher than those of the Ni@G@MA coating. The coated steel by Ni@Cr-G@MA exhibits UV stability up to 110 h, while the SHP-coated steel by Ni@G@MA exhibits UV stability for 60 h. The potentiodynamic polarization results show that the value of the corrosion current density for bare steel is 13 times that of steel coated with Ni@G@MA, and 21 times that of coated steel with Ni@Cr-G@MA. The electrochemical impedance spectroscopy, EIS, results show that the charge transfer resistance for steel coated with Ni@G@MA is 38 times that of bare steel, while steel coated with Ni@Cr-G@MA is 57 times that of bare steel. Potentiodynamic polarization and EIS results show that the SHP Ni@Cr-G@MA film exhibits higher corrosion resistance than Ni@G@MA film.

Nature‐Inspired Substrate‐Independent Omniphobic and Antimicrobial Slippery Surfaces

Inspired by the carnivorous Nepenthes pitcher plant, a range of highly liquid repellent lubricant‐infused surfaces has been devised (low water droplet contact angle hysteresis and sliding angle values). This entails matching functional pulsed plasma polymer nanolayers with appropriate slippery lubricants. A molecular‐level structure–behavior relationship is developed, highlighting the importance of favorable aromatic–aliphatic intermolecular interactions between the coating and lubricant. Fluorinated lubricant‐infused pulsed plasma polymer nanocoatings resist wetting by liquids, spanning a wide range of surface tensions (including pentane, motor oil, and water, i.e., omniphobicity). In the case of natural antimicrobial compound‐infused functional plasma polymer surfaces (e.g., the essential oil cinnamaldehyde), multifunctional performance is attained combining high liquid repellency (self‐cleaning) with simultaneous strong antibacterial activity against both Gram‐positive Staphylococcus aureus and Gram‐negative Escherichia coli (log10 reduction > 7). In addition, these lubricant‐infused functional pulsed plasma polymer surfaces easily repel a variety of everyday liquids (including foodstuffs such as tomato ketchup and honey).

Fluorine Free Bio-Based Polybenzoxazine Coated Substrates for Oil-Water Separation and Anti-Icing Applications

Eugenol (E) based mono-functional benzoxazine(E-x) monomers were prepared using different long-chain monoamines(x = ba, ha, dda, oda) and fluorine substituted aromatic monoamine (x = fa). The molecular structure of the monomers developed was characterized by FTIR and NMR spectral analysis. Further, the prepared monomers were coated over the cotton fabric and studied for their surface behavior. The poly(E-dda) coated cotton fabric exhibits the higher value of water contact angle (WCA = 151°) than that of other samples coated with polybenzoxazines(E-ba, E-ha,E-oda, and E-fa). Furthermore, poly(E-dda) coated cotton fabrics also displayed the lower value of surface energy of 15.6 mN/m with a lower sliding angle value(11°) than those of other coated cotton fabric samples. The formation of rough surfaces on the fabric was ascertained from microstructure analysis and thereby contributes to superhydrophobicity along with pH robustness. Subsequently, the oil-water separation efficiency and flux of the poly(E-dda) coated cotton fabric was found to be 98% and 5800 L/m2h respectively. It was also observed that the specimen of a glass substrate coated with poly(E-dda) exhibited the delayed ice formation. Data obtained from different studies, it is suggested that the eugenol-dodecylamine(E-dda) based benzoxazine can be effectively employed as an alternate to fluorine-based polymers.

Development of durable superhydrophobic cotton fabrics coated with silicone/stearic acid using different cross-linkers

Nano/micro-scaled surface roughness has been broadly applied for the development of water repellent merchandise. However, the sophisticated procedures, costly and harmful materials employed in the majority of superhydrophobic surface modification techniques have limited their usage. Herein, we develop a mechanically durable superhydrophobic cotton fabric via simple modification of surface roughness using cheap and nontoxic composite. Commercial RTV (Room Temperature Vulcanized) silicone and stearic acid were employed for the surface roughness control. Simple pad-dry-cure and spray-coating approaches were employed to create highly water repellent cotton fabric with high contact angles. Depending on RTV and fatty acid ratio, it was possible to obtain a rough surface with a hierarchical morphology. The stearic fatty acid was admixed with RTV to be effectively applied via both pad-dry-cure and spray-coating techniques onto a pre-treated cotton fabric surface using three different cross-linkers, including citric acid, 3-Isocyanatepropyltriethoxysilane (IPES) and tetraethylorthosilicate (TEOS). The wetting performance was found to depend on the concentration of RTV in toluene as a solvent introducing surface roughness with static water contact angle near to 170° and low sliding angle values as low as 4°. The surface morphological properties of the coated cotton substrates were explored by scanning electron microscopy (SEM). The superhydrophobic performance was investigated employing both of wettability time static water contact angle measurements. The chemical composition of coated cotton substrates was studied employing Fourier-transform infrared spectroscopy (FTIR) and energy-dispersive X-ray analysis (EDAX). Both mechanical and antimicrobial properties of the treated fabrics were investigated. The coated cotton substrates exhibited improved superhydrophobic performance without adversely affecting on its pristine physico-mechanical characteristics. The comfort properties of coated cotton fabrics were also examined by exploring their bending length and air permeability. The results demonstrated durable superhydrophobic performance of the coated samples, presenting a good chance for a large-scale production of superhydrophobic garments for a variety of industrial applications.

Efficient one-step fabrication of superhydrophobic nano-TiO2/TMPSi ceramic composite coating with enhanced corrosion resistance on 316L

TiO2 Nanoparticle/Trimethoxy(propyl)silane (TMPSi) ceramic composite coating was deposited on 316L steel using a one-step electrophoretic deposition (EPD) method. Silane coupling agent (TMPSi) was added to the EPD bath in different concentrations (from 0.5 to 15 vol %) to decrease the surface energy of the deposited coating. TiO2 coating is hydrophilic whereas by adding varying concentrations of TMPSi, the obtained nanocomposite coating showed much better hydrophobicity. Surface wettability was measured by water contact angle (WCA) and sliding angle (SA) tests. Moreover, the effect of TMPSi concentration was determined by comparing the WCA and SA values. Surface morphology was studied through Field Emission Scanning Electron Microscopy (FESEM), and the presence of micro/nano meter roughness on the surface was confirmed. The distribution of elements were investigated by EDS analysis in which their uniform dispersion was observed. Corrosion behavior of 316L samples before and after the coating process was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests in 3.5 wt % NaCl solution. The polarization curve proved that the superhydrophobic ceramic nanocomposite coatings (WCA = 168° and SA = 3.1°) were able to decrease the corrosion rate of bare 316L (from 12.180 to 5.621 (μm per year)).

Development of mechanically durable hydrophobic lanolin/silicone rubber coating on viscose fibers

We report on a simple technique for the production of mechanically durable water-repellent layer on viscose fibers via spray-coating of a lanolin-silicon rubber solution in petroleum ether. Depending on the silicon rubber solution concentration, it was achievable to gain surfaces with hierarchical morphology. Extracted lanolin was admixed with a mixture of a room temperature vulcanizing silicon rubber and petroleum ether to afford the silicon rubber-lanolin formulation, which was applied successfully onto viscose fabrics employing spray-coat procedure. The surface characteristics of the spray-coated viscose fibers were studied by scanning electron microscope, energy dispersive X-ray analysis, and static water contact and sliding angle measurements. The alteration in the chemical composition of viscose-treated fabric was studied using Fourier-transform infrared spectroscopy. The wetting behavior was found to be a function of silicon rubber concentration in ether solution affording coatings with high static water contact angle and low sliding angle values. The treated viscose fabric exhibited excellent ultraviolet protection and enhanced hydrophobicity without adverse effect on its inherent physico-mechanical properties. The comfort characteristics of spray-coated viscose fibers were also evaluated by studying their air-permeability and stiffness. The results displayed durable water-repellent properties of the treated viscose, introducing a good opportunity for a large-scale manufacture of water-repellent textiles for a diversity of industrial purposes.

Experimental Study of Factors Controlling Tilt-Test Results Performed on Saw-Cut Rock Joints

Abstract One of the main inputs when estimating the shear strength of rock discontinuities, according to most existing strength criteria, is what is known as the basic friction angle, which is a parameter that responds to the frictional resistance of a planar, unfilled, and nonweathered rock joint. The basic friction angle can be estimated according to various procedures, although the tilt test is the simplest and possibly the most popular approach. With a view to standardizing tilt-test procedures, the present study provides experimental results regarding the influence of factors such as tilting rate, machine vibrations, and rock surface wear and roughness on sliding angle values. The tilting rate has been statistically and experimentally proved to scantily affect tilt test results when using motorized tilting tables and, by observing certain cutting guidelines, it is possible to expect reasonably representative and reproducible results. Nevertheless, the effect of wear associated with repeated testing and of microroughness significantly affects the resulting basic friction angle values. General recommendations are provided regarding better control of the studied factors as well as test results.

Superhydrophobic surface on aeronautical materials via the deposition of nanoparticles and a PDMS seal

This paper reports a stable superhydrophobic surface on resin composites through the coprecipitation process of hydroxyethyl cellulose and modified Zn-particles, subsequently with the use of PDMS seal. Surface morphologies and chemical compositions are investigated with SEM, EDS, and FT-IR. As expected, the prepared surface has the water repellency with the contact angle of 153° and the sliding angle of 1°, respectively. According to the comparison of different specimens when after the liquid impingement test, it can be reasonably demonstrated that appropriate PDMS seal improves the stability with regard to superhydrophobic surfaces. When superhydrophobic surface is soaked chronically and impinged strongly by water, its water repellency is going to reduce. However, further surface modification introduced by combustion leads to excellent water repellency again. And the sliding angle value of further modified surface is below 1°. The preparation of superhydrophobic surface is also applicable to a paper. This superhydrophobic paper is less flammable than the untreated paper. In addition, the as-prepared superhydrophobic surface exhibits good self-cleaning ability towards avoiding different types of contaminants.

Fabrication of superhydrophobic composite coating based on fluorosilicone resin and silica nanoparticles.

Composite superhydrophobic coating built with film former and filler is attracting much attention for its facile and convenient fabrication, but significant limitations and disadvantages still remain. In this paper, a composite superhydrophobic coating is introduced which can be cured at room temperature and made by dispersing modified silica nanoparticles with 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane in fluorosilicone resin. Silica content and dispersion time showed obvious influences on the morphology and topography of composite coating by reuniting dispersed nanoparticles to form peaks on the surface. Excessively large distances between these peaks would decrease water contact angle value. Increasing slope of peaks, appropriate distance between peaks and decreasing diameter size of peaks would diminish sliding angle value. Formation mechanism of the composite coating based on fluorosilicone resin and modified nanoparticles was explained using interpenetrating polymer model.

Hydrothermal synthesis of urchin-like alumina for fire-extinguishing powders

Alumina with an urchin-like morphology has been synthesized from Al2(SO4)3/CO(NH2)2/H2O/isopropanol mixture via hydrothermal route followed by calcination. Raman spectra and SEM images have shown the urchin-like structure to be formed of γ-AlOOH phase with the component ratio Al3+/CO(NH2)2/H2O = 1:(2–3):(100–200). The increase in CO(NH2)2 content has resulted in the formation of needle-like crystals of NH4Al(OH)2CO3. Structural transformations of alumina during hydrothermal synthesis have been investigated by SEM and TEM methods. The 5–10 μm urchin-like alumina particles have been found to be composed of 100–200-nm-thick sheets. The alumina samples have been studied by low-temperature nitrogen adsorption method. The adsorption–desorption isotherms and pore size distributions have shown that pore structure of the urchin-like alumina is formed by the slit pores with two open ends. It has been found that after treatment with chlorosilanes the surface of the urchin-like alumina becomes superhydrophobic, the average contact and sliding angle values being 154° and 5°, respectively. Addition of 5 wt% of the hydrophobized urchin-like alumina particles to the model fire-extinguishing powder has made the powder hydrophobic, the average contact angle being increased up to 151°. Introduction of 5 wt% of the hydrophobized urchin-like alumina particles to ammonium dihydrophosphate has resulted in a decrease in the cohesion strength for ammonium dihydrophosphate fire-extinguishing powder from 0.415 to 0.104 kPa. The hydrophobized urchin-like alumina particles can be used as functional additives to the fire-extinguishing powders for the improved flowability and water repellency to be achieved.

Fabrication and Properties of Superhydrophobic Surfaces Based on Low-Density Polyethylene/Ethylene–Propylene–Diene Terpolymer Thermoplastic Vulcanizate

ABSTRACTA simple, effective, and inexpensive method has been developed to fabricate superhydrophobic surfaces based on low-density-polyethylene/ethylene–propylene–diene terpolymer thermoplastic vulcanizate. Field emission scanning electron microscope research showed that the rough microstructure could be fabricated successfully in the thermoplastic vulcanizate surface where metallographic sandpaper was used as molding template; moreover, the micrometer scale plastic deformation of thermoplastic vulcanizate matrix could be observed obviously, leading to the increasing surface roughness. Wettability test showed that the series rough thermoplastic vulcanizate surfaces that were molded with sandpapers had strong hydrophobic property; furthermore, the sliding angle value was less than 10°. Metallographic sandpaper template exhibited well re-used property.

Facile spray-coating process for the fabrication of tunable adhesive superhydrophobic surfaces with heterogeneous chemical compositions used for selective transportation of microdroplets with different volumes.

In this paper, tunable adhesive superhydrophobic ZnO surfaces have been fabricated successfully by spraying ZnO nanoparticle (NP) suspensions onto desired substrates. We regulate the spray-coating process by changing the mass percentage of hydrophobic ZnO NPs (which were achieved by modifying hydrophilic ZnO NPs with stearic acid) in the hydrophobic/hydrophilic ZnO NP mixtures to control heterogeneous chemical composition of the ZnO surfaces. Thus, the water adhesion on the same superhydrophobic ZnO surface could be effectively tuned by controlling the surface chemical composition without altering the surface morphology. Compared with the conventional tunable adhesive superhydrophobic surfaces, on which there were only three different water sliding angle values: lower than 10°, 90° (the water droplet is firmly pinned on the surface at any tilted angles), and the value between the two ones, the water adhesion on the superhydrophobic ZnO surfaces has been tuned effectively, on which the sliding angle is controlled from 2 ± 1° to 9 ± 1°, 21 ± 2°, 39 ± 3°, and 90°. Accordingly, the adhesive force can be adjusted from extremely low (∼2.5 μN) to very high (∼111.6 μN). On the basis of the different adhesive forces of the tunable adhesive superhydrophobic surfaces, the selective transportation of microdroplets with different volumes was achieved, which has never been reported before. In addition, we demonstrated a proof of selective transportation of microdroplets with different volumes for application in the droplet-based microreactors via our tunable adhesive superhydrophobic surfaces for the quantitative detection of AgNO3 and NaOH. The results reported herein realize the selective transportation of microdroplets with different volumes and we believe that this method would potentially be used in many important applications, such as selective water droplet transportation, biomolecular quantitative detection and droplet-based biodetection.

Sliding behavior of oil droplets on nanosphere stacking layers with different surface textures

Two facile coating techniques, gravitational sediment and spin coating, were applied for the creation of silica sphere stacking layers with different textures onto glass substrates that display various sliding abilities toward liquid drops with different surface tensions, ranged from 25.6 to 72.3 mN/m. The resulting silica surface exhibits oil repellency, long-period durability > 30 days, and oil sliding capability. The two-tier texture offers a better roll-off ability toward liquid drops with a wide range of γ L, ranged from 30.2 to 72.3 mN/m, i.e., when the sliding angle (SA) < 15°, the oil droplet start to roll off the surface. This improvement of sliding ability can be ascribed to the fact that the two-tier texture allows for air pockets (i.e., referred to as the Cassie state), thus favoring the self-cleaning ability. Taking Young–Duprè equation into account, a linearity relationship between sine SA and work of adhesion ( W ad) appears to describe the sliding behavior within the W ad region: 2.20–3.03 mN/m. The smaller W ad, the easier drop sliding (i.e., the smaller SA value) takes place on the surfaces. The W ad value ∼3.03 mN/m shows a critical kinetic barrier for drop sliding on the silica surfaces from stationary to movement states. This work proposes a mathematical model to simulate the sliding behavior of oil drops on a nanosphere stacking layer, confirming the anti-oil contamination capability.

Transparent water repellent silica films by sol–gel process

Non-wettable surfaces with high contact angles and facile sliding angle of water droplets have received tremendous attention in recent years. The present paper describes the room temperature (∼27 °C) synthesis of dip coated water repellent silica coatings on glass substrates using iso-butyltrimethoxysilane (iso-BTMS) as a co-precursor. Emphasis is given to the influence of the hydrophobic reagent (iso-BTMS) on the water repellent properties of the silica films. Silica sol was prepared by keeping the molar ratio of tetraethoxysilane (TEOS) precursor, methanol (MeOH) solvent, water (H 2O) constant at 1:16.53:8.26 respectively, with 0.01 M NH 4F throughout the experiment and the molar ratio of iso-BTMS/TEOS ( M) was varied from 0 to 0.965. The effect of M on the surface structure and hydrophobicity has been researched. The static water contact angle values of the silica films increased from 65° to 140° and water sliding angle values decreased from 42° to 16° with an increase in the M value from 0 to 0.965. The water repellent silica films are thermally stable up to a temperature of 280 °C and above this temperature the film shows hydrophilic behavior. The water repellent silica films were characterized by the Fourier Transform Infrared (FT-IR) Spectroscopy, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), % of optical transmission, thermal and chemical aging tests, humidity tests, static and dynamic water contact angle measurements.

Diurnal variation in the effects of alcohol and in the brain 5-hydroxytryptamine metabolism in mice.

Abstract: Adult male mice show diurnal variation in their performance in the tilted‐plane test and in their open field behaviour. Maximum sliding angle and minimum open field ambulation values were found at 04.00 hrs, minimum sliding angle and maximum open field ambulation values at 20.00 hrs. Diurnal variation was also found in the effects of ethyl alcohol. Its effect on the sliding angle values was greatest at 20.00 hrs and at 12.00 hrs, and on the open field ambulation at 16.00 hrs. The effects of alcohol were thus more pronounced when the activity level of the animals was high. No clear diurnal variation was found in the brain levels of 5‐hydroxytryptamine (5‐HT) and 5‐hydroxyindole acetic acid (5‐HIAA). The brain level of 5‐HIAA showed a trend to a negative correlation (r8 = −0.43) with the open field ambulation scores recorded at the same time of the day. The results indicate that the adrenergic and/or serotonergic brain mechanisms may be important in mediating the effects of alcohol.