Search results

Filters

  • Journals
  • Authors
  • Keywords
  • Date
  • Type

Search results

Number of results: 7
items per page: 25 50 75
Sort by:
Download PDF Download RIS Download Bibtex

Abstract

One of the biggest challenges facing a designer of paper structures is its low resistance to moisture and water. Paper is a hydrophilic material that absorbs moisture from the outside. This causes the hydrogen bonds between the cellulose molecules to loosen and as a result a rapid decrease in strength parameters. In order to be able to use paper as a construction material, there is a need to select and evaluate the effectiveness of the appropriate impregnant, as well as to know its impact on the mechanical properties of the impregnated paper. The paper analyzes the effect of the use of various impregnations, including wood oil, yacht lacquer, and fire-retardant agent impregnation, on the tensile strength of several types of cellulose-derived materials, e.g. corrugated board, solid board, paper cores, and honeycomb board. The effectiveness of the impregnation was also assessed using the method of measuring the contact angle of the reference and impregnated surfaces.
Go to article

Authors and Affiliations

Paweł Niewiadomski
1
ORCID: ORCID
Anna Karolak
1
Marta Oleksiak
1
Agnieszka Chowaniec-Michalak
1

  1. Wrocław University of Science and Technology, Wybrze˙ze Wyspia´nskiego 27, 50-370 Wrocław, Poland
Download PDF Download RIS Download Bibtex

Abstract

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.

Go to article

Authors and Affiliations

K. Banaszek
L. Klimek
Download PDF Download RIS Download Bibtex

Abstract

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.

Go to article

Authors and Affiliations

Jaqueline Franciosi Della Vechia
Renata Thaysa Santos
Fabiano Griesang
Cícero Mariano Santos
Marcelo Costa Ferreira
Daniel Junior Andrade
Download PDF Download RIS Download Bibtex

Abstract

The goal of this paper is to measure the non-wetting to wetting transition temperatures of liquid tin on surfaces of different steel samples in vacuum with residual pressure of 10–8 bar. The experiments were conducted on four steels (C45, S103, CK60 and EN1.4034) of varying compositions using pure tin (99.99%) by the sessile drop method. Non-wetting to wetting transition (contact angle decreasing below 90°) by liquid tin was observed as function of increasing temperature in the range of 820-940 K for low alloyed steels C45, S103 and CK60, while it was considerably higher (around 1130 K) for high chromium EN1.4034 steel. It is concluded that at about the same temperatures, the surfaces of the steel samples are spontaneously deoxidized due to the combined effect of high temperature, low vacuum and C-content of steels. After the oxide layer is removed, the contact angles of liquid tin on steel surfaces were found in the range of 45-80° for low alloyed C45, S103 and CK60 steels and around 20° for high chromium EN1.4034 steel. These relatively high contact angle values compared to other metal/metal couples (such as liquid Cu on steels) are due to the formation of not fully metallic intermetallic compounds (FeSn and FeSn2) at the interface (such do not form in the Cu/Fe system).
Go to article

Authors and Affiliations

D. Varanasi
1
K.E. Aldawoudi
1
P. Baumli
1
D. Koncz-Horvath
1
G. Kaptay
1

  1. University of Miskolc, Institute of Physical Metallurgy, Metal Forming and Nanotechnology, 3515 Miskolc-Egyetemvaros, Hungary
Download PDF Download RIS Download Bibtex

Abstract

Controlling the bubble size is a major concern in enhancing transport performance in gas-liquid systems. The role of wettability of diffuser surface on bubble size is the subject of the current work. The study inspects the contact angle of a set of liquids on HP ceramic diffusers using the Washburn method. The results demonstrate that organic liquids like toluene, methanol–water (1:1 v/v), ethanol– water (1:1 v/v) and decane have small contact angles of 12.9°, 37.5°, 24.4° and 22.5° respectively. Water has a lower wettability than the organic compounds where the contact angle was about 67.4°. The effect of wettability of the bubble size is investigated by measuring the size of air bubble produced using the same diffuser material. The results of bubble size measurement demonstrates that with liquids of small contact angle, i.e. good wetting properties, small bubble sizes are produced in comparison with liquids with a higher contact angle. The study demonstrates the viability of Washburn method in characterization of wettability of porous diffuser, which was verified by measuring the bubble size produced. A high reduction in bubble size can be obtained by a carefully chosen diffuser material that provides better wettability.
Go to article

Authors and Affiliations

Atheer M.G. Al-Yaqoobi
1
William B. Zimmerman
2

  1. Chemical Engineering Department, College of Engineering, University of Baghdad, Baghdad, Al-jadriya, Iraq
  2. Department of Chemical and Biological Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, UK
Download PDF Download RIS Download Bibtex

Abstract

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.

Go to article

Authors and Affiliations

S.J. Kim
I.C. Bang
J. Buongiorno
L.W. Hu
Download PDF Download RIS Download Bibtex

Abstract

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.

Go to article

Authors and Affiliations

Qihu Wang
Jie Wang
ORCID: ORCID
Yicheng Ye
Wei Jiang
Nan Yao

This page uses 'cookies'. Learn more