The production process of prosthetic restorations runs in two stages. In the first stage, the prosthetic foundation is produced of metal
alloys. In the second stage, a facing material is applied on the produced element. In both stages, the wettability is significantly important,
as well as the free surface energy relating to it. The quality of the obtained cast depends on the surface phenomena occurring between the
metal alloy and the material of which the casting mould is made. The performed examinations also point to a relation between the ceramics
joint and the base, depending on the wetting angle.
The aim of the presented paper was to examine influence of the composition of a Ti(C,N)-type coating on bases made of the Ni-Cr
prosthetic alloy on the wettability and the surface free energy.
The test material were disks made of the Ni-Cr alloy with the diameter of 8 mm. The disks were divided into five groups, which were
covered with Ti(C,N) coatings, with different amounts of C and N in the layer. In order to determine the surface free energy (����), the
wetting angle was measured. Two measure liquids were applied: distilled water and diiodomethane.
The obtained results of the measurements of the water-wetting angles suggest that together with the increase of the ratio of nitrogen to
carbon in the Ti(C,N) coating, the surface hydrophobicity increases as well. In all the samples, one can see a large difference between the
energy values of the polar and the apolar components. The high values of the polar components and the low values of the apolar ones make
it possible to conclude that these surfaces exhibit a greater affinity to the polar groups than to the apolar ones.
On the basis of the analysis of the surface free energy, one can state that covering the alloy with Ti(C,N)-type coatings should not decrease
the adhesion of the ceramics to the alloy, whereas TiC coatings should lead to the latter’s improvement. Due to their hydrophilicity, TiC
coatings should decrease the adhesion of bacteria to the surface and hinder the formation of a bacterial biofilm.
In agriculture, the mixing of pesticides in tanks is a common practice. However, it is necessary to previse possible physical-chemical implications of this practice, which may affect the efficiency of the treatments performed. Therefore, the objective of this study was to evaluate the effects of the addition of acaricide to insecticidal spray mixtures on the formation of spray droplets and the interaction with citrus leaves. The experimental design was totally randomized, in a (2 × 3 + 1) factorial scheme for seven treatments. Factor A corresponded to the spray mixture used (isolate or in the mixture). Factor B corresponded to the insecticides tested (lambda-cyhalothrin + thiamethoxam, phosmet, and imidacloprid) and the control consisted of a spray mixture with spirodiclofen only. Nine replications were performed for characterization of the spray droplet size spectrum and four replications for the analysis of the surface tension and the contact angle. The mixture of pesticides showed positive results in terms of application safety. The addition of acaricide to insecticide spray mixtures reduced the surface tension and contact angle of droplets on the adaxial surface of orange leaves. There was an increment in volume median diameter (VMD), a significant reduction in the volume of droplets with drift-sensitive size and improvement in the uniformity of droplet size. Therefore, the addition of acaricide to an insecticide spray mixture positively influenced spray droplet formation and the interaction with citrus leaves providing better coverage and droplet size fractions with an appropriate size for safe and efficient application.
The pool boiling characteristics of dilute dispersions of alumina, zirconia and silica nanoparticles in water were studied. These dispersions are known as nanofluids. Consistently with other nanofluid studies, it was found that a significant enhancement in Critical Heat Flux (CHF) can be achieved at modest nanoparticle concentrations (<0.1% by volume). Buildup of a porous layer of nanoparticles on the heater surface occurred during nucleate boiling. This layer significantly improves the surface wettability, as shown by a reduction of the static contact angle on the nanofluid-boiled surfaces compared with the pure-water-boiled surfaces. CHF theories support the nexus between CHF enhancement and surface wettability changes. This represents a first important step towards identification of a plausible mechanism for boiling CHF enhancement in nanofluids.
Significant differences in the physical and mechanical properties exist between the rock masses on two sides of an ore-rock contact zone, which the production tunnels of an underground mine must pass through. Compared with a single rock mass, the mechanical behavior of the contact zone composite rock comprising two types of rock is more complex. In order to predict the overall strength of the composite rock with different contact angles, iron ore-marble composite rock sample uniaxial compression tests were conducted. The results showed that composite rock samples with different contact angles failed in two different modes under compression. The strengths of the composite rock samples were lower than those of both the pure iron ore samples and pure marble samples, and were also related to the contact angle. According to the stress-strain relationship of the contact surface in the composite rock sample, there were constraint stresses on the contact surface between the two types of rock medium in the composite rock samples. This stress state could reveal the effect of the constraint stress in the composite rock samples with different contact angles on their strengths. Based on the Mohr-Coulomb criterion, a strength model of the composite rock considering the constraint stress on the contact surface was constructed, which could provide a theoretical basis for stability researches and designs of contact zone tunnels.