Surface Treatment Of Particles Research Articles

Effect of particle surface treatment and blending method on flexural properties of injection-molded cenosphere/HDPE syntactic foams

The present work on cenosphere/high-density polyethylene (HDPE) syntactic foams aims at understanding the effect of surface treatment of cenospheres and functionalization of HDPE on flexural properties. Cenospheres are treated with silane, and HDPE is functionalized with 10 % dibutyl maleate. Effects of mechanical and Brabender mixing methods are also studied. Flexural test specimens are cast with 20, 40, and 60 wt% of cenospheres using injection molding. The flexural modulus and strength are found to increase with increasing cenosphere content. Particle breakage increases with the cenosphere content, and the measured properties show increased dependence on processing method. Brabender mixing resulted in 70 and 41 % higher modulus and strength for 60 wt% cenospheres than HDPE. Modulus of syntactic foams is predicted by two theoretical models. Bardella–Genna model provides close estimates for syntactic foams having 20 and 40 wt% cenospheres, while predictions are higher for higher cenosphere content, likely due to particle breakage during processing. The uncertainty in the properties of cenospheres due to defects contributes to the variation in the predicted values.

Effects of Silica Nanoparticle Addition on Dynamic Properties of Poly(lactic acid)

Bioplastics are plastics derived from renewable sources such as corn starch or microbe and biodegradable plastics are plastics that are capable of being decomposed by bacteria or other living organisms. Poly (lactic acid) (PLA) is a typical and biodegradable bioplastic. It has been recognized as a promising alternative material for petroleum-based polymers. In order to increase Young’s modulus, in the present study, silica nanoparticles were added to PLA. The effects of the addition of silica nanoparticles and the surface treatment of nanosilica particles on dynamic properties of nanoparticle added PLA were examined using tensile split Hopkinson pressure bar method and the Izod impact strength tests.

Nano-TiO2 reinforced PEEK/PEI blends as biomaterials for load-bearing implant applications.

Biocompatible ternary nanocomposites based on poly(ether ether ketone) (PEEK)/poly(ether imide) (PEI) blends reinforced with bioactive titanium dioxide (TiO2) nanoparticles were fabricated via ultrasonication followed by melt-blending. The developed biomaterials were characterized using FT-IR, SEM, XRD, DSC, TGA, and DMA. Further, their water-absorption, tensile, tribological, dielectric, and antibacterial properties were evaluated. PEI acts as a coupling agent, since it can interact both with PEEK via π-π stacking and polar interactions as well as with the nanoparticles through hydrogen bonding, as corroborated by the FT-IR spectra, which resulted in a homogeneous titania dispersion within the biopolymer blend without applying any particle surface treatment or polymer functionalization. A change from promotion to retardation in the crystallization rate of the matrix was found with increasing TiO2 concentration, while its crystalline structure remained unaltered. The nanoparticles stiffened, strengthened, and toughened the matrix simultaneously, and the optimal properties were achieved at 4.0 wt % TiO2. More interesting, the tensile properties were retained after steam sterilization in an autoclave or exposure to a simulated body fluid (SBF). The nanocomposites also displayed reduced water absorption though higher thermal stability, storage modulus, glass transition temperature, dielectric constant, and dielectric loss compared to the control blend. Further, remarkable enhancements in the tribological properties under both SBF and dry environments were attained. The nanoparticles conferred antibacterial action versus Gram-positive and Gram-negative bacteria in the presence and the absence of UV light, and the highest inhibition was attained at 4.0 wt % nanoparticle concentration. These nanocomposites are expected to be used in long-term load-bearing implant applications.

Influence of the grafting topology of hydrophobic silica surfaces on the mechanical properties of silicone high consistency rubbers

Silica-filled rubber materials exhibit stress softening and hysteresis under cyclic loadings. These phenomena are usually associated with both the Payne and Mullins effects. To better characterize these properties, five model silicas were produced and used in industrial-like high consistency rubber (HCR) formulations: the native (hydrophilic) silica and four chemically modified silicas for which both the content of surface silanols and the nature of the grafted silicone chains differ. Silica − polydimethylsiloxane HCR elastomer with constant silica content and optimal dispersion was tested via static (uniaxial tensile tests, cyclic and monotonic) and dynamic tests. The Payne and Mullins effects as well as the ultimate properties were evaluated as a function of particle surface treatment. It was found that the Payne amplitude decreases with the content of grafted chains, whereas the Mullins effect and ultimate strain decrease with an increase in molar mass between crosslinks. Finally, the ultimate strength is optimal as long as silica is surface treated, albeit independent of surface grafting topology. © 2015 Society of Chemical Industry

A new coating method for alleviating surface degradation of LiNi0.6Co0.2Mn0.2O2 cathode material: nanoscale surface treatment of primary particles.

Structural degradation of Ni-rich cathode materials (LiNi(x)M(1-x)O2; M = Mn, Co, and Al; x > 0.5) during cycling at both high voltage (>4.3 V) and high temperature (>50 °C) led to the continuous generation of microcracks in a secondary particle that consisted of aggregated micrometer-sized primary particles. These microcracks caused deterioration of the electrochemical properties by disconnecting the electrical pathway between the primary particles and creating thermal instability owing to oxygen evolution during phase transformation. Here, we report a new concept to overcome those problems of the Ni-rich cathode material via nanoscale surface treatment of the primary particles. The resultant primary particles' surfaces had a higher cobalt content and a cation-mixing phase (Fm3̅m) with nanoscale thickness in the LiNi0.6Co0.2Mn0.2O2 cathode, leading to mitigation of the microcracks by suppressing the structural change from a layered to rock-salt phase. Furthermore, the higher oxidation state of Mn(4+) at the surface minimized the oxygen evolution at high temperatures. This approach resulted in improved structural and thermal stability in the severe cycling-test environment at 60 °C between 3.0 and 4.45 V and at elevated temperatures, showing a rate capability that was comparable to that of the pristine sample.

The Rheokinetics of a Bisphenol a Epoxy Oligomer during Curing in the Presence of a Solid Filler Surface

An investigation was made of model dressed and undressed solid and hollow glass spheres on the rheokinetics during the curing of epoxy binder based on ED-20. It was established that the introduction of solid undressed glass spheres in a quantity of over 15 wt% slightly accelerates the curing process (∼15%) of composites. For the first time it was shown experimentally that the surface treatment of glass particles with a dressing agent containing terminal amine groups leads to an increase in the curing rate owing to the chemical interaction of reaction groups of the dressing agent and epoxy oligomer.

Effect of Particle Loading, Temperature and Surface Treatment on Moisture Absorption of CFB Fly Ash Reinforced Thermoset Composite

Effect of Particle Loading, Temperature and Surface Treatment on Moisture Absorption of CFB Fly Ash Reinforced Thermoset Composite

Are There Generalizable Trends in the Release of Airborne Synthetic Clay Nanoparticles from a Jet Milling Process?

Despite recent efforts to assess the release of nanoparticles to the workplace during different nanotechnology activities, the existence of a generalizable trend in the particle release has yet to be identified. This study aimed to characterize the release of synthetic clay nanoparticles from a laboratory-based jet milling process by quantifying the variations arising from primary particle size and surface treatment of the material used, as well as the feed rate of the machine. A broad range of materials were used in this study, and the emitted particles mass (PM2.5) and number concentrations (PNC) were measured at the release source. Analysis of variance, followed by linear mixed-effects modeling, was applied to quantify the variations in PM2.5 and PNC of the released particles caused by the abovementioned factors. The results confirmed that using materials of different primary size and surface treatment affects the release of the particles from the same process by causing statistically-significant variations in PM2.5 and PNC. The interaction of these two factors should also be taken into account as it resulted in variations in the measured particles release properties. Furthermore, the feed rate of the milling machine was confirmed to be another influencing parameter. Although this research does not identify a specific pattern in the release of synthetic clay nanoparticles from the jet milling process generalizable to other similar settings, it emphasizes that each tested case should be handled individually in terms of exposure considerations.

A comparative evaluation of bond strength of feldspathic porcelain to nickel-chromium alloy, when subjected to various surface treatments: An in vitro study.

Purpose of the Study:The purpose was to evaluate the effect of various surface treatments and sandblasting with different particle size on the bond strength of feldspathic porcelain with predominantly base metal alloys, using a universal testing machine.Materials and Methods:Totally, 40 specimen of nickel-chromium alloy were prepared in an induction casting machine. The groups divided were as follows: Group I-sandblasted with 50 μ Al2O3, Group II-sandblasted with 110 μ Al2O3, Group III-sandblasted with 250 μ Al2O3 and Group IV-sandblasted with 250 μ Al2O3, followed by oxidation and again sandblasted with 250 μ Al2O3. The dimensions of each specimen were adjusted so as to maintain the thickness of ceramic at 1 mm. The specimen were loaded on the assembly of the universal testing machine, and a cross head speed of 0.5 mm/min was used to apply a compressive force at the junction of metal and feldspathic porcelain. The force application continued until adhesive fracture occurred, and the readings of the load applied to that particular specimen were recorded.Results:The means for shear bond strength for Group I, II, III and IV were found to be (226.92 ± 1.67), (233.16 ± 3.85), (337.81 ± 16.97) and (237.08 ± 4.33), respectively. Means of shear bond strength among the groups were compared using one-way analysis of variance test. Comparison between individual groups were made with Tukey's Honestly Significant Difference post-hoc test.Conclusion:Different particle size and surface treatment have an important role on the bond strength of ceramic-metal interface. Greater particle size demonstrated higher bond strength.

Fabrication of silicon carbonitride-covered boron nitride/Nylon 6,6 composite for enhanced thermal conductivity by melt process

The surface-treated boron nitride (BN) particles are prepared with polysilazane (PSZ) by using a dip-coating method to fabricate a thermally conductive interface material. PSZ-BN particles are generated by crosslinking of PSZ on BN and heat treatment of the formed PSZ-BN at700 °C to convert PSZ-BN to SiCNO-BN. The SiCNO-BN particles are fabricated with Nylon 6,6 by using an extruder and injection molding method. The interfacial adhesion between the BN particles and the Nylon 6,6 matrix is enhanced by surface treatment of the BN particles. The surface-treated BN/Nylon 6,6 composites exhibit thermal conductivity ranging from 0.3270 to 0.4230W/mK (through-plane) and 1.6510 to 4.960W/mK (in-plane), which is higher than that in the case of loading with pristine BN/Nylon 6,6 composites at the same weight fraction. The tensile strength and tensile modulus increase from 59.13 and 1.67GPa with the use of pristine BN to 69.15 and 2.10GPa with incorporation of SiCNO-BN into the Nylon 6,6 composite.

Rheological and dynamic mechanical properties of polymer-bonded magnets based on Sm2Co17 and polyamide-12

The rheological and dynamic mechanical properties of polymer-based composites of Sm2Co17 and polyamide-12 with different particle loadings, sizes, and surface treatments are reported. Sm2Co17 parti ...

ANTICORROSION PROPERTIES OF PEROVSKITES SURFACE-MODIFIED WITH CONDUCTING POLYMERS IN ALKYDE COATINGS

The effect of pigment particle surface treatment with polyaniline and polypyrrole on the corrosion inhibiting properties of organic paints was investigated. Mixed oxides possessing the spinel and perovskite structures were synthesised for the study. Coatings based on an alkyde resin were prepared for the investigation of the corrosion protection properties of the pigments, the surfaces of which had been provided with a polyaniline and polypyrrole layers. Laboratory corrosion tests were applied to the paint films. Polyaniline phosphate was found preferable to polypyrrole as the modifying agent of the pigment surface regarding the pigment’s corrosion inhibiting efficiency.

Structure of silane layer formed on silica particle surfaces by treatment with silane coupling agents having various functional groups

The surface treatment of spherical silica particles with silane coupling agents having various organic functional groups was conducted and the effect of the alkoxy group number on the molecular flexibility of the silane chain with multilayer coverage was investigated using 1H-pulse nuclear magnetic resonance spectroscopy. The silica particles were treated with 2-propanol solution and heated at 120 °C for 24 h after solvent evaporation to accelerate the polycondensation reaction of silanol groups. For multilayer coverage, flexible linear chain and rigid network structures were expected to form on the surface from the di- and trialkoxy structures, respectively. However, the rigid network structure was formed from both the di- and trialkoxy structures with glycidoxy, amino, and methacryloxy functional silanes. Ring opening of the epoxy group occurred, followed by reaction to form the network structure, even with the dialkoxy structure of the glycidoxy functionality. Ring opening of the epoxy group could be reduced by pH adjustment of the treatment solution and the linear chain structure was formed from the dialkoxy structure. In the case of amino and methacryloxy functional groups, hydrogen bonds were formed between the amino or methacryloxy groups and the silanol groups on the silica surface or silane molecules.

Controlling foam morphology of polystyrene via surface chemistry, size and concentration of nanosilica particles

Controlling cell morphologies of polymeric foams is an important part of controlling foam properties. In this study, the effects of particle size, particle content, and particle surface chemistry on cell nucleation in nanosilica/polystyrene (PS) composites are investigated. A theoretical hypothesis on the effect of nanoparticle size on cell nucleation in PS matrix foam was examined. The surface chemistry of nanosilica particles was studied by modifying them with Vinyltriethoxysilane (VTES) silane coupling agent. The microcellular porous materials of neat and composite PS were prepared by batch foaming technique (pressure quench) using supercritical carbon dioxide (ScCO2) as a blowing agent. It was found that the size of the pores decreases and the cell density increases with the decrease in nanosilica size and the increase of silica loading. It was also observed that the surface treatment of the nanosilica particles have substantial effect on the decrease of the cell size and the increase of the cell density.

Effect of surface treatment of pigment particles with polypyrrole and polyaniline phosphate on their corrosion inhibiting properties in organic coatings

The effect of pigment particle surface treatment with conductive polymers on the corrosion inhibiting properties of organic paints was investigated. Mixed oxides possessing the spinel and perovskite structures were synthesised for the study. Natural graphite and pigments based on ferric oxide and silicate were studied. Coating materials based on a water-based epoxy resin were prepared for the investigation of the corrosion protection properties of the pigments, the surfaces of which had been provided with a conductive polymer layer. Laboratory corrosion tests were applied to the paint films. A commercial corrosion protection pigment, based on modified zinc phosphate, served as the corrosion protection efficiency standard. Polyaniline phosphate was found preferable to polypyrrole as the modifying agent of the pigment surface regarding the pigment's corrosion inhibiting efficiency. Surface treatment with the conductive polymers is also beneficial to the mechanical properties of the paint.

Silicon carbonitride covered SiC composites for enhanced thermal conductivity and electrical insulation

Surface-treated silicon carbide (SiC) particles were prepared with polysilazane (PSZ) and its amorphous silicon carbonitride (SiCNO) ceramic coatings on the SiC surface using a dip-coating method. Moisture-crosslinking of PSZ on the SiC produced PSZ–SiC particles, and heat treatment of the PSZ–SiC at 800 °C converted the PSZ–SiCNO. The surface treatment of the SiC particles enhanced interfacial adhesion with the silicone-based matrix. The thermal transport properties of these composites were investigated and then, interpreted with Agari's model. An analysis of the coefficients of this model indicated that the surface treatment of SiC particles facilitates the formation of conducting paths. The electrical properties of the composites also demonstrated the effect of the amorphous Si–C–N–O network on the SiC surface.

Fabrication of surface-treated SiC/epoxy composites through a wetting method for enhanced thermal and mechanical properties

• SiC/epoxy composites is prepared by the wetting method. • The surface treatment of SiC particles results in an enhanced wettability of epoxy. • The measured thermal conductivity is correlated with theoretical models. • Storage modulus reveals that the wetting process results in enhanced mechanical properties. Silicon carbide (SiC)/epoxy composites were prepared by a wetting method. To increase the dispersion of dropped epoxy resin on top of the SiC cake, a surface oxidation treatment was applied to the SiC particles. The surface treatment of the SiC particles was applied for an enhanced wettability of the epoxy resin due to a secondary interaction between SiC and epoxy. The thermal transport properties of the composites were maximized at 70 wt.% of SiC during the wetting process because of the limited porosity of the SiC cake. The measured thermal conductivity as a function of the filler concentration correlated with Agari’s model. The results, based on the coefficient obtained by Agari’s model, indicated that the wetting method for the production of the composites combined with a surface treatment of SiC particles facilitates the formation of conducting paths. Storage modulus results also revealed that the wetting process results in enhanced mechanical properties of the composites.

Methanol Oxidation at Diamond-Supported Pt Nanoparticles: Effect of the Diamond Surface Termination

The electrocatalytic reactivity of Pt nanoparticles supported on high-pressure, high-temperature diamond particles toward adsorbed CO, methanol, and formic acid oxidation is investigated employing differential electrochemical mass spectrometry (DEMS). Surface treatment of diamond particles, employed as dimensionally stable electrocatalyst supports, leads to materials with surfaces featuring mainly hydrogen (HDP) or oxygen-based functional groups (ODP). Pt nanoparticles with average diameter below 5 nm were generated by impregnation of the modified diamond particles. The voltammetric responses associated with the oxidation of adsorbed CO appeared unaffected by the surface termination of the diamond support. However, significant differences were observed for methanol oxidation in acid solutions, with Pt/HDP producing smaller current densities than Pt/ODP and a commercially available Pt catalyst (Pt/E-TEK). DEMS studies show higher conversion efficiencies to CO2 for Pt/ODP and Pt/E-TEK, while Pt/HDP exhibite...

A New Promising Nucleating Agent for Polymer Foaming: Applications of Ordered Mesoporous Silica Particles in Polymethyl Methacrylate Supercritical Carbon Dioxide Microcellular Foaming

The introduction of inorganic particles to improve the cell morphology of polymeric foams has been studied for decades. To this end, identifying an ideal nucleating agent and understanding the methodology to control nucleation have always been the focus of this field. In this study, spherical ordered mesoporous silica (OMS) particles were synthesized and applied as a potential nucleating agent in polymethyl methacrylate (PMMA) supercritical carbon dioxide (scCO2) microcellular foaming. These particles were modified with a silane containing fluorine to enhance their affinity with scCO2. For comparison, solid silica (SS) particles with almost similar particle size and surface treatment have also been studied. It was found that both of them could be well dispersed in the PMMA matrix, and exhibited excellent heterogeneous nucleation performance during the foaming process. The addition of a nucleating agent greatly increased the cell density and decreased the average cell diameter, and more importantly, there was no increase in the bulk density. Compared to SS particles, OMS particles showed higher nucleation efficiency. The addition of 5.0 wt % of OMS particles reduced the average cell diameter of PMMA foam from 1.62 to 0.66 μm and increased the cell density from 2.3 × 1011 cells/cm3 to 3.7 × 1012 cells/cm3, while for the composite foams with a similar content of SS particles, the cell diameter and cell density are 1.19 μm and 6.12 × 1011 cells/cm3, respectively. We speculated that the mesoporous structure of OMS particles might trap the CO2 forming gas cavities. The pre-existing gas cavities resulted in a lower nucleation energy barrier. The superior nucleation effect of the OMS particles became more significant when the foaming process was conducted at low foaming temperature, low saturation pressure, and/or high pressure drop rate.

Influences of the alkoxy group number and treatment condition on the structure of glycidoxy functional silane-treated layer on silica particles analyzed by 1H pulse NMR

The surface treatment of spherical silica particles using a silane coupling agent with a glycidoxy group was conducted and the effect of the alkoxy group number on the molecular mobility of the silane chain was investigated by 1H pulse nuclear magnetic resonance (NMR). Silanes with di-alkoxy and tri-alkoxy structures were used, and the silica particles were treated with 2-propanol solution and heated at 120 °C for 24 h after solvent evaporation. The surface coverage of the silica surface was in the range from two to three layers. For multilayer coverage, linear chain and network structures were expected to form on the surface by polycondensation reaction using the di- and tri-alkoxy structures, respectively. However, the relaxation times for silane chains with both di- and tri-alkoxy structures measured by pulse NMR were short, which indicates that both silane chains formed rigid network structures. Fourier transform infrared spectroscopic analysis revealed that ring opening of the epoxy group occurred, followed by reaction to form the network structure, even with the di-alkoxy structure. Ring opening of the epoxy group could be reduced by setting the heating temperature at 80 °C. There was a significant difference in flexibility between the silane-layers with di- and tri-alkoxy structures after heating at 80 °C, as reflected by the relaxation time.