Surface modification of silica: 1. Thermodynamic aspects and effect on elastomer reinforcement

A thorough investigation of the interactions between silica and elastomers was conducted with the specific aim of understanding how the degree of modification with bis-triethoxysilylpropyltetrasulfane (TESPT) influences the surface energy of the filler and the tensile properties of technical compounds. The results of a thermodynamic study carried out by Inverse Gas Chromatography (IGC) at infinite dilution on silica modified with different amounts of TESPT indicate that from 6 to 8 wt% of grafted TESPT the surface activity of silica is considerably reduced and prevents particle fillers from interacting with each others. Tensile measurements at very low and high deformations carried out on vulcanised compounds loaded with silica, either unmodified or modified with different amounts of TESPT, confirm our thermodynamic predictions and further support the role of TESPT in promoting interactions between filler and elastomer, in achieving better dispersions and in improving mechanical properties.     

Chromatographic estimation of filler surface energies and correlation with photodegradation of kaolin filled polyethylene

Inverse gas chromatography (IGC) has been used to investigate the surface properties of two calcined kaolins and of polyethylene composites containing calcined kaolin. The results reveal differences in the two kaolins that were not found in XPS spectra nor in their influence on the melting behaviour of the polymer. The kaolin that had a markedly higher surface energy and stronger Lewis acid behaviour was found to shower greater photooxidative degradation in accelerated weathering tests. This novel application of IGC derived surface characterisation of solids further extends the usefulness of the method in this type of work.     

反相气相色谱法表征PVC/纳米碳酸钙复合材料的表面性质

在30～60℃温度下,采用反气相色谱技术分析聚氯乙烯/纳米碳酸钙复合材料(PVC/NC)的表面色散自由能与表面路易斯酸碱性质,得出该材料在此温度区间的表面色散自由能。结果表明,PVC/NC的表面色散自由能随温度的升高而线性降低;PVC/NC为弱碱性路易斯两性聚合物其,路易斯酸常数Ka为0.20碱,常数Kb为0.39。     

Surface Modification and Planar Defects of Calcium Carbonates by Magnetic Water Treatment

Powdery calcium carbonates, predominantly calcite and aragonite, with planar defects and cation–anion mixed surfaces as deposited on low-carbon steel by magnetic water treatment (MWT) were characterized by X-ray diffraction, electron microscopy, and vibration spectroscopy. Calcite were found to form faceted nanoparticles having 3x (0[`1] 1 4 0\bar{1} 1 4 ) commensurate superstructure and with well-developed {1 1[`2] 0 1 1\bar{2} 0 } and {10[`1] 4 10\bar{1} 4 } surfaces to exhibit preferred orientations. Aragonite occurred as laths having 3x (0[`1] 1 0\bar{1} 1) commensurate superstructure and with well-developed (0[`1] 1 0\bar{1} 1 ) surface extending along [100] direction up to micrometers in length. The (hkil)-specific coalescence of calcite and rapid lath growth of aragonite under the combined effects of Lorentz force and a precondensation event account for a beneficial larger particulate/colony size for the removal of the carbonate scale from the steel substrate. The coexisting magnetite particles have well-developed {011} surfaces regardless of MWT.     

Cohesive Hamaker Constants and Dispersive Surface Energies of RDX,PETN, TNT,and Ammonium Nitrate‐Based Explosives

Inverse gas chromatography (IGC) was used to characterize dispersive surface energies γ_S^D and cohesive Hamaker constants A_ii for RDX, PETN, TNT, ammonium nitrate (AN), and AN‐based explosives at 303 K. The γ_S^D for RDX at 303 K is compared to previous studies and generally found to be in good agreement, substantiating the use of NESTT training materials to characterize explosives via IGC. Additionally, the effect of the amount of fuel in the AN mixtures on γ_S^D is examined using simple linear regression. Finally, the IGC‐predicted A_ii values are compared to Lifshitz estimations for A_ii of RDX, PETN, TNT, and AN.     

纳米碳酸钙的制备技术与表面改性方法

简述了我国纳米碳酸钙技术发展现状。介绍了纳米碳酸钙的生产技术路线,探讨了其中的碳化工艺和表面改性方法。目前我国有鼓泡碳化、喷雾碳化和超重力碳化等的碳化工艺,可采用钛酸酯、铝酸酯等偶联剂和脂肪酸、磷酸酯等表面活性剂对纳米碳酸钙进行表面改性。     

Atmospheric pressure plasma surface modification of titanium for high temperature adhesive bonding

In this investigation surface treatment of titanium is carried out by plasma ion implantation under atmospheric pressure plasma in order to increase the adhesive bond strength. Prior to the plasma treatment, titanium surfaces were mechanically treated by sand blasting. It is observed that the contact angle of de-ionized water decreases with the grit blast treatment time. Optical microscopy and scanning electron microscopic (SEM) analysis of untreated and atmospheric plasma treated titanium are carried out to examine the surface characteristics. A substantial improvement in the surface energy of titanium is observed after the atmospheric pressure plasma treatment. The surface energy increases with increasing exposure time of atmospheric pressure plasma. The optimized time of plasma treatment suggested in this investigation results in maximum adhesive bond strength of the titanium. Unmodified and surface modified titanium sheets by atmospheric pressure plasma were adhesively bonded by high temperature resistant polyimide adhesive. The glass transition temperature of this adhesive is 310 °C and these adhesively bonded joints were cured at high temperature. A substantial improvement in adhesive bond strength was observed after atmospheric pressure plasma treatment.     

The effect of cataphoretic and powder coatings on the strength and failure modes of EN AW-5754 aluminium alloy adhesive joints

The aim of this study is to determine the effect of cataphoretic and powder coatings and also the method of application the primer on the adherends surface on the strength and failure modes of EN AW-5754 aluminium alloy adhesive joints. The study is performed on lap joints made of EN AW-5754 aluminium alloy, subjected to three different types of surface treatment; namely a) polyurethane cataphoretic coating, b) powder coating based on black mat RAL 9005 UL polyester resin and c) no coating. The tested adhesive joints were made using a one-component polyurethane adhesive Terostat 8596, which was dedicated for automotive and cured under a constant load of 0.018 MPa at 20 ± 2 °C. In addition, this study investigates the effect of the application of Terostat 8519P adhesion promoter which is a liquid polyurethane-based primer containing solvents and which is corresponding to Terostat 8596 polyurethane adhesive. Terostat 8519P adhesion promoter was applied in two different ways: a) to one substrate and b) to both substrates. The produced adhesive joints were subjected to strength tests using the Zwick/Roell Z150 testing machine. The examination of fracture in the tested adhesive joints was performed in accordance with the EN ISO 10365 standard. The shear strength results have demonstrated that both the method of application of the adhesion promoter (Terostat 8519 P) and the presence of cataphoretic coating had an influence on adhesive joints strength. The use of the adhesion promoter significantly affects the strength of both uncoated EN AW-5754 aluminium alloy adhesive joints and the adhesive joints subjected to powder coating. The use of the adhesion promoter has a less significant effect on the cataphoretic-coated samples.     

Surface modification and characterisation of a coal-based activated carbon

Surface modification of a coal-based activated carbon (F400) was performed using thermal and chemical methods. Nitric acid oxidation of the conventional sample produced samples with weakly acidic functional groups and the presence of such groups was confirmed by Fourier transform infra red (FTIR) spectroscopy, pH titration, zeta potential measurements and sodium uptake capacity results. There was a significant loss in microporosity of the oxidised samples which was caused by humic substances that were formed as a by-product during the oxidation process. Thermal treatment produced a carbon with some basic character while amination of the thermally treated carbon gave a sample containing some amino (–NH₂) groups and these groups were detected by X-ray photoelectron spectroscopy (XPS) analysis.     

Surface modification of calcium carbonates studied by inverse gas chromatography and the effect on mechanical properties of filled polypropylene

Inverse gas chromatography (IGC) has been used to characterize the surfaces of a pure calcitic calcium carbonate as well as samples that had been treated with sodium polyacrylate and/or stearic acid. The dispersive components of the surface free energy for the pure material agreed well with related literature data. Polar contributions to the surface interactions with a range of probes were determined. The results show that the surface treatments reduced the polarities of the surfaces and that modification with stearic acid produced a non-polar, low-energy surface. Some mechanical properties of the polypropylene composites containing the modified calcium carbonates were found to correlate well with the filler surface energies. Copyright © 2004 Society of Chemical Industry     

Plasma etching treatment for surface modification of boron-doped diamond electrodes

Boron-doped diamond (BDD) thin film surfaces were modified by brief plasma treatment using various source gases such as Cl₂, CF₄, Ar and CH₄, and the electrochemical properties of the surfaces were subsequently investigated. From X-ray photoelectron spectroscopy analysis, Cl and F atoms were detected on the BDD surfaces after 3 min of Cl₂ and CF₄ plasma treatments, respectively. From the results of cyclic voltammetry and electrochemical AC impedance measurements, the electron-transfer rate for Fe(CN)₆^3−/4− and Fe^2+/3+ at the BDD electrodes was found to decrease after Cl₂ and CF₄ plasma treatments. However, the electron-transfer rate for Ru(NH₃)₆^2+/3+ showed almost no change after these treatments. This may have been related to the specific interactions of surface halogen (C-Cl and C-F) moieties with the redox species because no electrical passivation was observed after the treatments. In addition, Raman spectroscopy showed that CH₄ plasma treatment of diamond surfaces formed an insulating diamond-like carbon thin layer on the surfaces. Thus, by an appropriate choice of plasma source, short-duration plasma treatments can be an effective way to functionalize diamond surfaces in various ways while maintaining a wide potential window and a low background current.     

Catalytic properties and surface modification of hexaaluminate microcrystals for combustion catalyst

Spinel oxide (Mn₃0₄) surface layers were produced on hexaaluminate microcrystals by means of the air-oxidation process. The surface layer completely covered the basal plane of hexagonal facets as evident from HREM observation and CO₂ chemisorption measurement. The catalytic activity of as prepared Mn₃0₄/hexaaluminate composites for methane combustion was evaluated as functions of the Mn₃0₄loading and the metal composition of the spinel surface layer. It was revealed that the air oxidationderived composites showed the excellent specific activities superior to those of the corresponding Mn₃0₄/hexaaluminates prepared from the conventional evaporation-to-dryness process. Partial substitution of Fe for Mn of the surface layer was effective in enhancing combustion activity in a whole temperature range.     

The effect of primary particle surface energy on agglomeration rate in fluidised bed wet granulation

The effect of primary particle surface wettability by a binder solution on the rate of agglomeration in a fluid-bed top-spray granulation process was investigated. A model system consisting of hydrophilic and hydrophobic spherical primary particles with a narrow size distribution, and an aqueous solution of hydroxy propyl-cellulose (HPC) as binder, was used. The surface energy of the primary particles was measured by inverse gas chromatography (IGC) and their wettability was characterised by static and dynamic contact angle. Granulation was carried out in a desktop fluid-bed granulator and the resulting granule size distribution and granule microstructure were analysed. The hydrophobic particles gave a wider granule size distribution (larger maximum granule size) than hydrophilic ones under otherwise identical conditions, and the granules were notably rounder and more compact. However, the fraction of un-granulated fines was also higher in the case of hydrophobic primary particles. SEM analysis of granule microstructure revealed that the hydrophilic particles were coated by the binder solution, which left a smaller amount of binder available to form bonds at particle contacts. On the other hand, all of the binder was found to form solid bridges in the case of hydrophobic primary particles. A population balance model was used to explain the observed granulation behaviour.     

Wetting Behavior of Ibuprofen Racemate Surfaces

The wetting behavior and detailed surface energetics of a racemate crystalline system were measured via contact angle measurements and inverse gas chromatography at finite concentrations. The advancing contact angles for water, diiodomethane, formamide, and ethylene glycol were measured on specific facets for racemic ibuprofen and S-(+)-ibuprofen single macroscopic crystals, and were found to be facet dependent for both systems. This observation demonstrates that variation in molecular orientation within the crystal lattice results in variations in exposed surface chemistry for differing facets, which results in anisotropic wetting behavior as previously reported. Surface free energy profiles of the ibuprofen racemates determined using a novel inverse gas chromatography method showed that powder samples (75–150 µm particle diameter) exhibited relatively homogeneous surface energies, with similar values of γ_SV ^d to those obtained by the contact angle analysis. These results lead us to conclude that ibuprofen exhibited a low level of surface heterogeneity, with the dominant facet of these powders exhibiting a low γ_SV ^d, with high energetic sites estimated to be < 3% of exposed available surface.     

Tailorable shielded compliance of thermal barrier coatings through laser texturing and microstructural modification: microfeature design and validation

Thermal barrier coatings (TBCs) are widely used for protecting components from an aggressive environment and excessive temperatures. However, the top coat can lack thermal compliance and environmental resistance, promoting premature failure. This study provides an approach to design, produce, and evaluate the novel shielded-compliant TBCs to address these challenges. Top coat laser grooving can lower thermal mismatch levels and hinder crack propagation, whereas laser glazing can enhance strength and anti-corrosion performance. Material analysis for the glazed layer revealed large columnar grains alongside a stress-free structure compared to the as-sprayed coating. The digital image correlation (DIC) in-situ heating test showed vertical cracks after glazing already to be effective stress relief features, with the controlled grooves showing the most prominent compliance, as suggested by finite element analysis (FEA). Such a concept may be applied to any coating where increased thermal compliance or environmental protection is needed, making it a highly versatile tool.     

PP-g-PMMA表面性质的反相气相色谱分析

采用反相气相色谱探针技术研究了聚丙烯接枝聚甲基丙烯酸甲酯共聚物的表面物理化学性质,包括探针分子在聚合物表面吸附热力学函数、比保留体积以及分子间相互作用参数。探讨了共聚物中极性链段聚甲基丙烯酸甲酯的含量与其表面性质的关系。结果表明接枝共聚物表面组成中随聚丙烯接枝聚甲基丙烯酸甲酯含量的增加,其表面能增大,表面分子链与探针分子的相互作用增强,表面吸附能力也增强。     

Surface modification of polyimide by combining swelling and TiO2 photocatalytic treatments for adhesion improvement of electroless Cu

In order to enhance the adhesion strength between the PI film and the electroless copper film, a combination of swelling and TiO₂ photocatalytic treatments was used to modify polyimide (PI) film. The effects of the swelling solution composition and TiO₂ photocatalytic condition on the surface performance were investigated. After the optimal swelling and photocatalytic treatment, the surface contact angle of the PI film decreased from 85 to 28.7°, and the surface average roughness of the PI film only increased from 1.3 to 13.6?nm, indicating no obvious change for the surface topography of PI film after the photocatalytic treatment. However, the adhesion strength between electroless copper film and the PI film reached to 0.6?KN·m^?1. The FT-IR spectra and XPS analyses indicated that –COOH group was formed on the PI surface after the treatment, and the surface hydrophilicity was improved, which improved the adhesion strength between the PI film and the electroless copper film.     

Characterisation of the surface thermodynamic properties of cement components by inverse gas chromatography at infinite dilution

The surface thermodynamic properties of three main inorganic compounds formed during hydration of Portland cement: calcium hydroxide (Ca(OH)₂), ettringite (3CaO·Al₂O₃·3CaSO₄·32H₂O) and calcium-silicate-hydrates (C-S-H), respectively, and one mineral filler: calcium carbonate (CaCO₃), have been characterised by inverse gas chromatography at infinite dilution (IGC-ID) at 35 °C. The thermodynamic properties have been investigated using a wide range of non-polar (n-alkane series), Lewis acidic (CH₂Cl₂ and CHCl₃), Lewis basic (diethyl ether) and aromatic (benzene) and n-alkene series molecular probes, respectively. The tested samples are fairly high surface energy materials as judged by the high dispersive contribution to the total surface energy (the dispersive components γ_s^d range from 45.6 up to 236.2 mJ m^− 2 at 35 °C) and exhibit amphoteric properties, with a predominant acidic character. In the case of hydrated components (i.e. ettringite and C-S-H), the surface thermodynamic properties have been determined at various temperatures (from 35 up to 120 °C) in order to examine the influence of the water content. The changes of both dispersive and specific components clearly demonstrate that the material surface properties are activated with temperature. The changes in the acid-base properties are correlated with the extent of the overall water loss induced by the thermal treatment as demonstrated by thermogravimetric analysis (TGA). The elemental surface composition of these compounds has been determined by X-ray photoelectron spectroscopy (XPS).     

Surface modification of water treatment equipment for reducing CaSO4 scale formation

Scale formation has been recognised as a widespread problem in membrane filtration and water desalination processing for water treatment. In this paper, the effect of surface energy of Ni-P-PTFE composite coatings on the microstructure and adhesion of CaSO₄ deposits was investigated. The surface energies of the Ni-P-PTFE coatings were altered by changing the PTFE proportion in the coatings. Initial experimental results showed that the surface energy of the coatings had a significant influence on the microstructure and adhesion of CaSO₄ deposits. The Ni-P-PTFE coatings have a potential for reducing CaSO₄ scale formation on water treatment equipment.     

Dielectric and Chromatographic Characterization of Polyethylene Glycols as Stationary Phases

Abstract

Three types of polyethylene glycols of different molecular weights namely, 600, 4000 and 20000, were evaluated as liquid stationary phases in gas liquid chromatography. Thus, the retention mechanism for the studied polymer stationary phases, 15% by weight on chromosorb PAW and their thermodynamic parameters have been investigated via inverse gas chromatography. The effect of polymer molecular weight on their efficiency as liquid stationary phases for the gas chromatographic separation of different types of hydrocarbons is also studied. The dielectric constant of dilute solutions for the studied polymers as dissolved in solvent chloroform was studied corresponding to their polarities. Two different modes of clusters were determined due to the solute-solute and solute-solvent interaction through hydrogen bonds.

All studied polymers have higher performance for separation of cyclic and aromatic compounds. Good chromatographic separation of n-alcohols is obtained toward polyethylene glycol (PEG20000) of relatively higher molecular weight. The saturated hydrocarbons can be separated very efficiently using low molecular weight polyethylene glycol (PEG600).