Adhesion Problems Research Articles

Enhancing the potential of employing thermosetting powder recyclates as filler in LLDPE by structural modifications

Abstract Potential of using powder coating recyclates as filler material for polyethylene compounds was investigated. Due to their strong adhesion to the metal surface during compounding at extrusion temperatures higher than 100°C, the coating powder recyclates were chemically modified to facilitate its processing by extrusion and injection molding at higher temperatures. For this purpose, the coating powder recyclates were first hydrolyzed with addition of an alcohol as swelling agent. The deactivated recyclates were mixed at different ratios with the matrix polymer, a linear low-density polyethylene (LLDPE). The mixtures obtained were then compounded by extrusion and subsequently injection molded to plates to produce specimens for testing. The resulting samples were characterized mechanically by tensile, bending, and impact strength tests. In summary, the powder coatings recyclates can be processed as filler for thermoplastic material, without any adhesion problems up to 160°C and 180°C in the extruder and in the injection molding machine, respectively.

Steel to Concrete Bond Transferring in CFST Columns Connected to Beams through the Concrete

An important innovation in structural design in the last thirty years has been the use of steel-concrete composite columns, with particular diffusion of tubular profiles. These elements are known in the technical Literature as concrete filled steel tube (CFST) and the metal profiles that characterize the external jacket are usually circular, square or rectangular.A relevant issue that must be considered is the transfer of shear stresses by adhesion between steel and concrete in composite columns. The problem of adhesion, and thus its formulation, depends primarily on the type of technology used to connect beams to columns. In particular, two different models can be produced: the first case where the beams are connected only to the metal external jacket of the pillar (i.e. steel beams connected with bolted flanges to the column), and the second where beams and columns are connected also in the concrete matrix (i.e. the case of beams in steel-concrete technology, or traditional reinforced concrete beams).International Standards, regarding the problem of adhesion in jacketed columns, only referee to the first connection type, giving a constant value for adhesion coefficient along the transferring length, with no dependence to the size of the section, and indicate transferring lengths independently from the type of beam-to-column connection and the shape of the section. In the Paper are hence proposed expressions that quantify the fundamental values that govern the action transfer mechanism by adhesion in CFST, such as the transfer length, the perimeter of the active transfer and the shear stress distribution, as a function of the slenderness ratio and of the type of connection adopted. All this has been carried in order to produce a model for the estimation of bond stresses for the second of the two construction system mentioned above.

Johnson-Kendall-Roberts adhesive contact for a toroidal indenter.

The unilateral axisymmetric frictionless adhesive contact problem for a toroidal indenter and an elastic half-space is considered in the framework of the Johnson-Kendall-Roberts theory. In the case of a semi-fixed annular contact area, when one of the contact radii is fixed, while the other varies during indentation, we obtain the asymptotic solution of the adhesive contact problem based on the solution of the corresponding unilateral non-adhesive contact problem. In particular, the adhesive contact problem for Barber's concave indenter is considered in detail. In the case when both contact radii are variable, we construct the leading-order asymptotic solution for a narrow annular contact area. It is found that for a v-shaped generalized toroidal indenter, the pull-off force is independent of the elastic properties of the indented solid.

Influence of Mo–N as diffusion barrier in Mo back contacts for Cu(In,Ga)Se2 solar cells

In a recent article, we have shown that a high selenium amount (selenium partial pressure) during the stacked elemental layer process is beneficial for the Cu(In,Ga)Se2 absorber layer in terms of Ga/In interdiffusion and Ga enhancement at near-surface regions. For highly efficient Cu(In,Ga)Se2 thin film solar cells in the stacked elemental layer process a certain MoSe2 thickness at the interface between Mo and Cu(In,Ga)Se2 is necessary. However, the high selenium supply leads to back contact corrosion, which results in adhesion problems of the film and an increase of the series resistance of the solar cell device. Introduction of a thin diffusion barrier against selenium penetration at the interface between Cu(In,Ga)Se2 absorber layer and Mo back contact is a possible solution which may ensure homogeneous back contact properties while allowing high selenium supply during the stacked elemental layer process. In this work, a new approach for an alternative back contact system is presented which includes a functional Mo–N layer. During the Mo sputtering process, the implementation of a reactive N2 gas process is easily possible. According to structural analysis just a thin self-limited MoSe2 layer with a constant thickness is formed during the stacked elemental layer process at the back contact. It is further demonstrated that a thin Mo–N barrier layer leads to an improved fill factor in the current–voltage characteristic of the cell, whereas thicker barrier layers negatively affect the series resistance of the cell.

Anti-adhesion effects of liquid-infused textured surfaces on high-temperature stainless steel for soft tissue

Soft tissue adhesion on the electrosurgical instruments can induce many serious complications, such as failure of hemostasis and damage to the surrounding soft tissue. The soft tissue adhesion is mainly caused by the high temperature on the instrument surface generally made of stainless steel. Nepenthes inspired liquid-infused surfaces (LIS), highly promising for anti-adhesion, have attracted considerable interests. In this paper, we investigated the anti-adhesion effects of LIS on high-temperature stainless steel for soft tissue for the first time, aiming to develop a new approach to solve the soft tissue adhesion problem. The textured surface, acting as the holding structures, was fabricated by photolithography-assisted chemical etching. Silicone oil, with good biocompatibility and high-temperature resistance, was chosen as the infused liquid. The adhesion force measurements for soft tissue on the LIS at high temperatures indicated that the soft tissue adhesion force was decreased by approximately 80% at 250°C. Besides, the cycle tests of soft tissue adhesion force demonstrated the excellent stability of prepared LIS. We anticipate that LIS will be of great promise for practical applications on the electrosurgical instruments.

Periodic adhesive contact between an elastic anisotropic layer and a wavy rigid halfspace

The paper presents solutions to the periodic adhesive contact problem between an elastic anisotropic layer and a wavy rigid half-space. Different systems including rigid, soft substrate and infinite elastic layer with orientation effect are considered in the paper. The periodic Green function in the form of Fourier series is obtained to formulate an integral equation of the contact pressure. The relation between the contact pressure and the relative approach is derived analytically. The results show that the adhesion effect depends strongly on both material orientation of the elastic layer and the substrate stiffness. These results are in particular useful for the design of new tunable adhesive systems.

A simple method for solving adhesive and non-adhesive axisymmetric contact problems of elastically graded materials

An efficient method is presented for solving axisymmetric, frictionless contact problems between a rigid punch and an elastically non-homogeneous, power-law graded half-space. Provided that the contact area is simply-connected profiles of arbitrary shape can be considered. Moreover, adhesion in the framework of the generalized JKR-theory can be taken into account. All results agree exactly with those given by three-dimensional contact theories. The method uses the fact that three-dimensional contact problems can be mapped to one-dimensional ones with a properly defined Winkler foundation; hence, the method is to be understood as an extension of the method of dimensionality reduction (MDR). A prerequisite of its applicability forms the generality of contact stiffness regardless of the geometry of the axisymmetric profile, which is proved. All the necessary mapping rules are derived and their ease of use explained by a recent example.

Two Kinds of Contact Problems in Dodecagonal Quasicrystals of Point Group 12 mm

In this paper, two kinds of contact problems in 2-D dodecagonal quasicrystals were discussed using the complex variable function method: one is the finite frictional contact problem, the other is the adhesive contact problem. The analytic expressions of contact stresses in the phonon and phason fields were obtained for a flat rigid punch, which showed that: (1) for the finite frictional contact problem, the contact stress exhibited power-type singularities at the edge of the contact zone; (2) for the adhesive contact problem, the contact stress exhibited oscillatory singularities at the edge of the contact zone. The distribution regulation of contact stress under punch was illustrated; and the low friction property of quasicrystals was verified graphically.

Hybrid Silver Mesh Electrode for ITO-Free Flexible Polymer Solar Cells with Good Mechanical Stability.

Herein, we report a tailored Ag mesh electrode coated with poly(3,4-ethylenedioxythiophene) (PEDOT) polymer on a flexible polyethylene terephthalate (PET) substrate. The introduction of this highly conductive polymer solves the existing problems of Ag mesh-type transparent conductive electrodes, such as high pitch, roughness, current inhomogeneity, and adhesion problems between the Ag mesh grid and PEDOT polymer or PET substrate, to result in excellent electron spreading from the discrete Ag mesh onto the entire surface without sacrificing sheet conductivity and optical transparency. Based on this hybrid anode, we demonstrate highly efficient flexible polymer solar cells (PSCs) with a high fill factor of 67.11 %, which results in a power conversion efficiency (PCE) of 6.9 % based on a poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b'] dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl) carbonyl]thieno[3,4-b]thiophenediyl}):[6,6]-phenyl-C71 -butyric acid methyl ester bulk heterojunction device. Furthermore, the PSC device with the Ag mesh electrode also exhibits a good mechanical bending stability, as indicated by a 70 % retention of the initial PCE after 500 bending cycles compared with the PSC device with a PET/indium tin oxide electrode, which retained 0 % of the initial PCE after 300 bending cycles.

Plasma surface Cu alloyed layer as a lubricant on stainless steel sheet: Wear characteristics and on-job performance in incremental forming

To solve the problems of poor forming and easy adhesion of the stainless steel, Cu alloyed layer on the stainless steels was prepared by the double glow plasma surface alloying technique. The experimental results indicated that the supersaturated copper dispersedly precipitated in grain interior and crystal boundaries and formed the vermicular structure. The tribological tests indicated that the friction coefficient of the Cu alloyed layer was lower than that of the stainless steels. The wear rate of stainless steel in the presence of Cu alloyed layer was approximately 2-fold lower than that in the absence of the alloyed layer. The results of the incremental forming indicated that the ploughing phenomenon was not observed on the stainless steel in the presence of Cu alloyed layer during the incremental forming, while the stainless steel presented the deep ploughing. Therefore, Cu alloyed layer on stainless steel exhibited excellent self-lubrication and forming properties.

Nanogap Embedded Transistor for Investigation of Charge Properties in DNA

A new structure to investigate the charge trapping characteristics of a DNA is proposed. The structure of the proposed device is a field effect transistor (FET) with a nanogap in the dielectric layer. With the proposed device, the charge trapping characteristics of the DNA are confirmed without any adhesion problems and electrical contact instability. The extraction of both electron and hole trapping characteristics were analyzed with an n-channel and a p-channel FET, respectively. The results showed that guanine has plenty of hole trap sites with a shallow energy level, which explains why hole hopping dominantly occurs in the guanine base.

Critical investigation of high performance spin-coated high-κ titania thin films based MOS capacitor

We report the tunable dielectric constant of titania films with low leakage current density. Titanium dioxide (TiO2) films of three different thicknesses (36, 63 and 91 nm) were deposited by the consecutive steps of solution preparation, spin-coating, drying, and firing at different temperatures. The problem of poor adhesion between Si substrate and TiO2 insulating layer was resolved by using the plasma activation process. The surface roughness was found to increase with increasing thickness and annealing temperature. The electrical investigation was carried out using metal-oxide-semiconductor structure. The flat band voltage (VFB), oxide trapped charge (Qot), dielectric constant (κ) and equivalent oxide thicknesses are calculated from capacitance–voltage (C–V) curves. The C–V characteristics indicate a thickness dependent dielectric constant. The dielectric constant increases from 31 to 78 as thickness increases from 36 to 91 nm. In addition to that the dielectric constant was found to be annealing temperature and frequency dependent. The films having thickness 91 nm and annealed at 600 °C shows the low leakage current density. Our study provides a broad insight of the processing parameters towards the use of titania as high-κ insulating layer, which might be useful in Si and polymer based flexible devices.

Effects of surface tension on the adhesive contact between a hard sphere and a soft substrate

In the present paper, the adhesive contact between a rigid sphere and a compliant elastic substrate with surface tension is analyzed. Using the minimum potential energy principle and considering both the effects of surface tension and adhesion, explicit solutions are obtained for the contact radius and the indent depth for the case without external loading. It is found that surface tension evidently alters the pressure distribution in the contact region and tends to decrease both the contact radius and the indent depth. The present model establishes a bridge between the JKR model for adhesive contact problems and the Young-Laplace's law of surface tension.

Singular perturbation by bending for an adhesive obstacle problem

A free boundary problem arising from materials science is studied in one-dimensional case. The problem studied here is an obstacle problem for the non-convex energy consisting of a bending energy, tension and an adhesion energy. If the bending energy, which is a higher order term, is deleted then "edge" singularities of the solutions (surfaces) may occur at the free boundary as Alt-Caffarelli type variational problems. The main result of this paper is to give a singular limit of the energy utilizing the notion of $\Gamma$-convergence, when the bending energy can be regarded as a perturbation. This singular limit energy only depends on the state of surfaces at the free boundary as seen in singular perturbations for phase transition models.

A Method to Ensure Long-term Adhesion Quality of Al-LDPE-Al Hybrid Sandwich Panels

The adhesion problem of aluminum polyethylene sandwich panels is analyzed within the scope of this study. The theoretical necessary adhesion value for maximum shear stress is calculated. A selected area of the panel is scanned with a peeling test. The set limit value of adhesion led to no customer claims within the observed period of six months. The condition of machine elements and the recycled material quality of polyethylene are also determined.

Factors affecting the floto-elutriation process efficiency of a copper sulfide mineral

Coarse mineral particles exhibit poor conventional flotation efficiency because of many factors, including the low carrying capacity of bubbles, bubble/particle adhesion problems due to cell turbulence, and low degrees of liberation (low hydrophobicity). Many attempts to improve the recovery of coarse fractions have been explored, such as floto-elutriation operating at a high solid content while dispersed in a fluidized (or expanded) bed formed with a continuous injection of compressed air and an uprising water flow. This work analyzed the comparative performances of floto-elutriation (FE) and conventional flotation (CF) on a classified copper sulfide mineral feed as an example of a difficult-to-liberate low-grade ore. Contrary to expectations, CF and FE (Hydrofloat) displayed similar particle recovery rates with feed size distributions for P80s of 130, 240 and 280μm. However, metallurgical recoveries from classified fractions of −297+210μm were 25% higher in FE than in CF and as expected, coarse (+297μm) particles were not recovered in the CF, but in the FE. The recovery of fine fractions in the FE process was due to high hydraulic entrainment and surprisingly the recovery of intermediate and liberated fractions (+74−149μm) was very low, due to its low air hold-up. However, the enhancement of the holdup in FE increased the recovery of these mid-sized fractions. Because of the hydraulic carryover caused by the bubbles and water elutriation, the metallurgical grades obtained in all cases were very low compared to conventional bench flotation. It is believed that this FE equipment works better with coarse, narrowly classified particles and high-grade feeds and that performance decreases for low-grade ores requiring high liberation. Certain features of these findings are visualized.

A three‐dimensional surface stress tensor formulation for simulation of adhesive contact in finite deformation

SummaryA three‐dimensional surface adhesive contact formulation is proposed to simulate macroscale adhesive contact interaction characterized by the van der Waals interaction between arbitrarily shaped deformable continua under finite deformation. The proposed adhesive contact formulation uses a double‐layer surface integral to replace the conventional double volume integration to compute the adhesive contact force vector. Considering nonlinear finite deformation, we have derived the surface stress tensor and the corresponding tangent stiffness matrix in a Galerkin weak formulation. With the surface stress formulation, the adhesive contact problems are solved in the framework of nonlinear continuum mechanics by using the standard Lagrange finite element method. Surface stress tensors are formulated for both interacting bodies. Numerical examples show that the proposed surface contact algorithm is accurate, efficient, and reliable for three‐dimensional adhesive contact problems of large deformations for both quasi‐static and dynamic simulations. Copyright © 2015 John Wiley & Sons, Ltd.

Улучшение адгезии в системе полиэтилентерефталат-древесина

Wood-plastic composite material is primarily a mixture of various natural (cellulose, lignin, etc.) and synthetic polymers (polyethylene, polypropylene, polyethylene terephthalate, etc.) In close interaction of molecules of different polymers behave in relation to each other in different ways: some are attracted, others repelled. Some polymers tend to join with each other in a chemical reaction, other chemically neutral. This phenomenon is called compatibility. The problem of compatibility of chemically different materials is well illustrated by a well-known example of the interaction of oil and water. Water droplets roll on the surface oil and oiled steel needle does not want to sink. In practice cannot be completely hydrophilic or hydrophobic substances, as well as oleophobic and oleophilic. Every substance has a greater or lesser degree of hydrophilicity, hydrophobicity, uliopilaste and oleophobicity. Chemistry gives you the opportunity to resolve the problem of adhesion of wood and synthetic polymers in a lot of ways, including modifying resin or (and) particles of wood (chemical, thermo-mechanical, mechanochemical, and even plasma irrad-iation processing). Modification of the basic raw materials are rather widely, since they have a good perspective. The article presents the research results of the bonding strength of the polyethylene terephthalate – wood and method of its improvement. To determine the adhesion strength in the system binder – filler were used the special samples for testing shear. The three selected wood species: pine, birch and oak. As the polymer component used PCM. The experiment was conducted on a tensile testing machine CDM a-10 with the use of special mounting of the sample. It is established that the adhesive bonding strength of the polyethylene terephthalate-wood is very low. Processing glyoxal filler enhances the adhesion strength of wood to the polymer. Depending on the breed and the direction of fibers fixed in improving adhesion 6-23 times.

Titanium Oxide Adhesion Layer for High Temperature Annealed Si/Si3N4/TiO x /Pt/LiCoO2 Battery Structures

This work describes the influence of a high annealing temperature of about 700°C on the Si(substrate)/Si3N4/TiO x /Pt/LiCoO2 multilayer system for the fabrication of all-solid-state lithium ion thin film microbatteries. Such micro-batteries typically utilize lithium cobalt oxide (LiCoO2) as cathode material with a platinum (Pt) current collector. Silicon nitride (Si3N4) is used to act as a barrier against Li diffusion into the substrate. For a good adherence between Si3N4 and Pt, commonly titanium (Ti) is used as intermediate layer. However, to achieve crystalline LiCoO2 the multilayer system has to be annealed at high temperature. This post-treatment initiates Ti diffusion into the Pt-collector and an oxidation to TiO x , leading to volume expansion and adhesion failures. To solve this adhesion problem, we introduce titanium oxide (TiO x ) as an adhesion layer, avoiding the diffusion during the annealing process. LiCoO2, Pt and Si3N4 layers were deposited by magnetron sputtering and the TiO x layer by thermal oxidation of Ti layers deposited by e-beam technique. As-deposited and annealed multilayer systems using various TiO x layer thicknesses were studied by scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) and x-ray photoelectron spectroscopy (XPS). The results revealed that an annealing process at temperature of 700°C leads to different interactions of Ti atoms between the layers, for various TiO x layer thicknesses (25–45 nm).

ATUAÇÃO DO ENFERMEIRO COM PACIENTES COM DIABETES MELLITUS NA MELHORIA DA QUALIDADE DE VIDA

Objetivo: Analisar as condições que afetam a qualidade de vida de pacientes com diabetes mellitusconforme suas limitações. Materiais e métodos: Trata-se de uma revisão integrativa da literatura, a coletade dados foi realizada no período de fevereiro a agosto de 2014. Utilizou-se os descritores qualidade devida, diabetes mellitus e enfermagem. A amostra final constituiu-se por 7 (sete) artigos pertencentes àsbases de dados LILACS, BENDENF e MEDLINE, com recorte temporal entre os anos 2009 a 2014. Aanálise e discussão dos dados procederam-se de forma descritiva. Resultados: Os conteúdos dos artigosselecionados foram agrupados em três categorias analíticas: “fatores e aspectos associados ao diabetes queinterferem na qualidade de vida”, “dificuldades de adesão ao tratamento” e “conhecimentos da enfermagemsobre ações desenvolvidas no atendimento dos pacientes diabéticos”. O estudo evidenciou que muitaspessoas diabéticas não possuem conhecimento sobre a cronicidade e as inúmeras situações impostaspela doença, há dificuldades de adesão aos elementos que fazem parte da terapêutica: o tratamentomedicamentoso, exercício físico e plano alimentar. Estudos mostraram, ainda, que os enfermeiros possuemcompetência interpessoal, conhecimento, habilidade e capacidade para interagir com o paciente, aceitandoseus problemas, crenças e desejos. Considerações finais: Para que sejam atendidas as expectativas emrelação ao tratamento, controle da doença e uma qualidade de vida digna aos portadores de diabetes, osenfermeiros têm a missão de desenvolver estratégias que convençam o paciente a aderir ao tratamento, amudar seu estilo de vida, conscientizá-los sobre a patologia, e desenvolver o autocuidado.