Effect of nano‐modified SiO2/Al2O3 mixed‐matrix micro‐composite fillers on thermal,mechanical, and tribological properties of epoxy polymers

Thermo‐mechanically durable industrial polymer nanocomposites have great demand as structural components. In this work, highly competent filler design is processed via nano‐modified of micronic SiO₂/Al₂O₃ particulate ceramics and studied its influence on the rheology, glass transition temperature, composite microstructure, thermal conductivity, mechanical strength, micro hardness, and tribology properties. Composites were fabricated with different proportions of nano‐modified micro‐composite fillers in epoxy matrix at as much possible filler loadings. Results revealed that nano‐modified SiO₂/Al₂O₃ micro‐composite fillers enhanced inter‐particle network and offer benefits like homogeneous microstructures and increased thermal conductivity. Epoxy composites attained thermal conductivity of 0.8 W/mK at 46% filler loading. Mechanical strength and bulk hardness were reached to higher values on the incorporation of nano‐modified fillers. Tribology study revealed an increased specific wear rate and decreased friction coefficient in such fillers. The study is significant in a way that the design of nano‐modified mixed‐matrix micro‐composite fillers are effective where a high loading is much easier, which is critical for achieving desired thermal and mechanical properties for any engineering applications. Copyright © 2016 John Wiley & Sons, Ltd.     

Surface modification of titanium alloy with the Ti3Al + TiB2/TiN composite coatings

Laser cladding of the Ti₃Al + TiB₂ pre‐placed alloy powder on the Ti–6Al–4 V alloy in nitrogen protective atmosphere can form the Ti₃Al + TiB₂/TiN composite coating, which can dramatically improve the wear resistance of the Ti–6Al–4 V alloy surface. In this study, the Ti₃Al + TiB₂/TiN composite coatings on the Ti–6Al–4 V alloy have been researched by means of X‐ray diffraction, SEM and energy dispersive spectrometry. It was found that there is a metallurgical combination between the Ti₃Al + TiB₂/TiN composite coating and the substrate. The microhardness of the Ti₃Al + TiB₂/TiN composite coatings were 3 ~ 4 times higher than that of the Ti–6Al–4 V alloy because of the actions of the Ti₃Al + TiB₂/TiN hard phases and the grain refinement strengthening. Moreover, the wear mass losses of the Ti₃Al + TiB₂/TiN composite coatings were much lower than that of the substrate. Copyright © 2011 John Wiley & Sons, Ltd.     

Study of mechanical and tribological properties of nylon 66‐titanium dioxide microcomposite

Nylon 66 microcomposites with various weight percentage of titanium dioxide (TiO₂) were prepared by a twin screw extruder and investigated for mechanical and tribological properties. Mechanical properties of the composite such as tensile strength/modulus, flexural strength/modulus, impact, and compressive strength first showed an increase up to 6 wt% TiO₂ followed by a decrease at higher filler loading. The value of heat deflection temperature increased with the increase in wt% of TiO₂. Sliding wear tests were performed on pin‐on‐disk equipment under different loads, sliding velocity, and sliding distance combinations. It was found that micro‐TiO₂‐Nylon 66 composite exhibited reduced wear and coefficient of friction up to 6 wt% TiO₂. Micro‐TiO₂ at 2 wt% was most effective in improving the tribological properties of plain nylon 66. The worn surfaces were examined by scanning electron microscopy to understand the wear mechanism. The optimal combination from 2 wt% to 6 wt% micro‐TiO₂‐Nylon 66 can be used depending upon the application requiring improvement in tribological or mechanical properties, respectively.     

Interphase structure development in impact modified PP/Mg(OH)2 composites reactively processed with 1,3‐phenylene dimaleimide

Interphase modification of impact modified isotactic poly(propene) (IMPP)/magnesium hydroxide (Mg(OH)₂) composites, via use of the reactive modifier 1,3 phenylene dimaleimide (BMI) has led to the formation of composites that have strength and toughness more than twice that of the unmodified composite. These significant improvements in properties were found (via response surface analysis, DSC and matrix extraction‐DRIFTS studies) to be due to encapsulation of the filler particles with the elastomeric poly(ethene‐co‐propene) impact modifier phase of the IMPP. Acceptable processing characteristics can be realised together with excellent mechanical properties, via judicious addition of a lubricant (a fatty acid amide/ester blend) to the formulation.     

Thermal resistance and mechanical stability of tungsten oxide filled polymer composite radiation shields

Abstract

The influence of tungsten oxide on thermal and mechanical properties of Isophthalic polyester was studied in detail. Ultrasonication technique was successful in dispersing WO₃ filler particles upto 40?wt% into the polymer matrix and was confirmed through the Scanning Electron Microscopy technique. The mechanical strength of the composites was found to increase with increase in the WO3 content and is acting as a reinforcer. About 77.4%, 65.4% and 7–8 times increase was observed in tensile, flexural and compressive strength respectively with respect to pristine. The thermogram of the composites reveal two stages of degradation. Maximum weight loss was observed in the first stage of degradation in almost all the composites. The initial degradation temperature of the composites range from 151?°C–226?°C. Activation energy was estimated using Horowitz–Metzger kinetic theory and was found to range from 25.31 to 78.58?kJ/Mol. The 50?wt% WO3 filled composite exhibits excellent thermal stability and mechanical strength. Thus, WO₃ filler particles were successful in enhancing the thermal and mechanical strength of Isophthalic polyester.     

Preparation and properties of polysulfone/TiO2 composite ultrafiltration membranes

The influence of inorganic filler TiO₂ nanoparticles on the morphology and properties of polysulfone (PS) ultrafiltration membranes was investigated. PS/TiO₂ composite membranes were prepared by a phase‐inversion method. TiO₂ nanoparticles modified by sodium dodecyl sulfate were uniformly dispersed in an 18 wt % PS casting solution. The addition of TiO₂ resulted in an increase in the pore density and porosity of the membrane skin layer. The pore size distribution changed from the log‐normal distribution to the bimodal distribution because of the presence of TiO₂ nanoparticles, and some large pores were observed when the concentration of the filler was over 3 wt %. The skin layer was gradually thickened; meanwhile, the morphology sublayer changed from macrovoids to spongelike pores, in comparison with PS membranes without the filler. The addition of TiO₂ also induced increases in the hydrophilicity, mechanical strength, and thermal stability. The ultrafiltration experiments showed when the concentration of TiO₂ was less than 2 wt %, the permeability and rejection of the membrane was enhanced and then decreased drastically with a higher filler concentration (>3%). © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 879–887, 2006     

Effect of SiC/nano‐CeO2 on wear resistance and microstructures of Ti3Al/γ‐Ni matrix laser‐cladded composite coating on Ti–6Al–4V alloy

The Ti–6Al–4V alloy is an important aviation material, but has a poor resistance to slide wear. Laser cladding of the Al₃Ti + Ni/Cr/C + TiB₂/Al₂O₃ + SiC/nano‐CeO₂ preplaced powders on the Ti–6Al–4V alloy can form the Ti₃Al/γ‐Ni matrix composite coating, which improves the wear resistance of the substrate. In this study, the Al₃Ti + Ni/Cr/C + TiB₂/Al₂O₃ + SiC/nano‐CeO₂ laser‐cladded coating was researched by means of X‐ray diffraction, scanning electron microscopy, and energy dispersive spectrometry. The experimental results indicate that under the action of SiC/nano‐CeO₂, this composite coating exhibited a fine microstructure. Furthermore, the proper content of nano‐CeO₂ decreased the crack tendency. The results above indicated that, it is feasible to improve the tribological property of the Al₃Ti + Ni/Cr/C + TiB₂/Al₂O₃ laser‐cladded coating by adding of SiC/nano‐CeO₂. Copyright © 2011 John Wiley & Sons, Ltd.     

Investigation of sub‐micron size cenosphere fillers and filler loading on the mechanical and tribological peculiarity of polyester composites

This paper investigates the effect of sub‐micron size cenosphere filler and filler loading on mechanical and dry sliding wear property of polyester composites. Composites are fabricated by filling with 10 and 20 wt% of 800 and 200‐nm size of cenosphere filler particles. Neat polyester composite is also prepared for comparison analysis. Dry sliding wear test is conducted for these composites over a range of sliding distance with different sliding velocities and applied loads on a pin‐on‐disc wear test machine. Taguchi methodology and analysis of variance (ANOVA) is used to analyze the friction and wear characteristics of the composites. The artificial neural network (ANN) approach is implemented to the friction and wear data for corroboration. In this work, mechanical properties of composites such as hardness, tensile strength, tensile modulus, flexural strength, and compressive strength revealed that mechanical properties and wear resistance of the composites increase with a decrease in the particle size. The measured Young's moduli are comparable to standard theoretical prediction models. The morphology of worn composite specimens has been examined by scanning electron microscopy to understand the dominant wear mechanisms. Finally, optimal factor settings are determined using a genetic algorithm (GA). Copyright © 2017 John Wiley & Sons, Ltd.     

Ethylene/silane copolymers prepared with a metallocene catalyst as polymeric additives in polyethylene/aluminum trihydroxide composites

Metallocene catalyst based polyethylene‐co‐7‐octenyldimethyl phenyl silane (PE/Si? Ph ) and its post‐treated functional forms PE/Si? X ( X = Cl , F , OCH₃ , OCH₂CH₃ ) were used as additives in PE/ATH composites. The impact strength of the composites was significantly increased after a small addition (0.5–3.0 wt %) of the functionalized form of the copolymer (PE/Si? X ). The thermal study of the composites gave us more information about the additive's behavior at the filler/matrix interphase and correlation to the mechanical properties was found. According to this thermal data, the original untreated form of PE/Si? Ph also seemed to interact weakly with the ATH‐filler particles, which was seen in an altered interphase at the filler/matrix boundary layer. The interaction was not strong enough to improve the impact strength of composites but an increase was observed in some other mechanical properties (tensile stress, yield strain). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5597–5608, 2005     

Characterization of Nanocomposite Coatings in the System Ti–B–N by Analytical Electron Microscopy and X-Ray Photoelectron Spectroscopy

 Superhard nanocomposite coatings of different composition in the quasi-binary system TiN–TiB₂ were deposited onto stainless steel sheets by means of unbalanced DC magnetron co-sputtering using segmented TiN/TiB₂ targets. The chemistry and microstructure of a TiB_0.6N_0.7 coating was investigated using X-ray and electron diffraction, photoelectron spectroscopy, energy-filtering transmission electron microscopy, and electron energy-loss spectrometry. High resolution elemental mapping of the elements Ti, B, N, and O with energy-filtering TEM reveals a homogeneous distribution on the nanometer scale. X-Ray and electron diffraction exhibit only TiN crystallites of nanometer size, but no information on the boron-rich phase. The near-edge fine structures of the BK and NK ionization edges in the EELS spectra of the Ti–B–N coatings were used to derive information on the phases by comparing the edges with those of reference compounds. It was found that the TiN nanocrystals occur together with TiO _x particles; the grains are embedded in a strongly disordered or quasi-amorphous matrix consisting mainly of TiB₂ particles and, near the steel substrate, also boron oxide (B₂O₃).     

Studies on UV‐stability of poly(MMA‐co‐M12‐co‐BPMA)/TiO2composite particles prepared by ultrasonically initiated emulsion polymerization

In this paper, poly(methyl methacrylate‐co‐sodium sulfopropyl lauryl maleate‐co‐2‐hydroxy‐4‐(3‐methacryloxy‐2‐hydroxylpropoxy) benzophenone)/TiO₂ (i.e., poly(MMA‐co‐M12‐co‐BPMA)/TiO₂) composite particles were prepared by ultrasonically initiated emulsion polymerization. To study the dispersion and UV‐stability of the composite particles, laser diffraction particle size analyzer (LDPSA), ultraviolet‐visible absorption spectroscopy (UV‐vis), UV‐vis diffuse reflectance spectroscopy (DRS), differential scanning calorimeter (DSC), and the weight loss measurement were used. The results indicate that the dispersion of the poly(MMA‐co‐M12‐co‐BPMA)/TiO₂ composite particles prepared by ultrasonically initiated emulsion polymerization is good. And the composite particles can absorb UV light; the ultraviolet absorption strength of poly(MMA‐co‐M12‐co‐BPMA) grafted onto the surface of TiO₂ has not changed after UV irradiation while that of PMMA changed significantly. The UV absorption strength, weight loss, and Tg changes are in the order PMMA> poly(MMA‐co‐M12‐co‐BPMA) >PMMA grafted onto TiO₂> poly(MMA‐co‐M12‐co‐BPMA) grafted onto TiO₂. These results show that the ultrasonically initiated emulsion polymerization will enhance the UV stability of composite particles, and the UV‐stability of PMMA can be enhanced by the introduction of the organic UV‐stabilizer BPMA and the inorganic UV‐stabilizer titanium dioxide into the PMMA chains by covalent bond, and the effect of the BPMA and the TiO₂ used together is better than that used, respectively. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation and characterization of SiO<Subscript>2</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–Na<Subscript>2</Subscript>O glass coated cBN abrasive particles via sol–gel route

SiO₂–Al₂O₃–Na₂O glass coated cubic boron nitride (cBN) abrasive particles were prepared by sol–gel technique. The results indicated that SiO₂–Al₂O₃–Na₂O glass was excellent material for oxidation protection of cBN abrasive grains because coefficient of thermal expansion of this glass closely matched that of cBN materials. The single particle compressive strength and impact toughness of this glass coated cBN abrasive particles were significantly increased. For the application of glass coated cBN abrasives to vitrified grinding wheels, it was evident that the glass coating provided high bonding strength between cBN abrasive grains and vitrified bond system.     

Conversion‐coating treatment applied to in situ TiB2p reinforced Al?Si‐alloy composite for corrosion protection

In this work, continuous conversion coatings on the surface of in situ TiB₂ particulate reinforced A356 composite were formed successfully by cerium surface treatment for the first time. Scanning electron microscope (SEM) analysis showed that the conversion coatings were inhomogeneous and could be divided into two types of regions, namely, fine crack region and noncrack region. Many cerium‐rich nano‐nodules were uniformly distributed in the whole coatings. Energy dispersive spectroscopy (EDS) analysis testified that the crack coatings mainly covered the interdendritic sites occupied by TiB₂ particulates and Si phases. X‐ray photoelectron spectroscopy (XPS) analysis indicated that the conversion coatings were composed of CeO₂, Ce₂O₃, Ce(OH)₄, Ce(OH)₃, and a little amount of Al₂O₃. The electrochemical polarization tests showed that the cerium‐conversion treatment markedly improved the corrosion resistance of in situ TiB_2p/A356 composite in chloride environment, and the protection degree of the coatings was superior to that of conventional chromate‐conversion coating. According to these results, the formation mechanism of cerium‐conversion coatings was discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Preparation of NiCrBSi‐WC brazed coating and its microstructure characteristics

WC–Ni composite coatings were developed by the powder cloth and the vacuum brazing technology. The wear resistance and the corrosion resistance of the brazed WC–Ni coatings were investigated. The peeling coating samples were prepared by using solder mask during brazing. The microstructures for the powder cloth and for the brazed coatings were characterized by scanning electron microscopy. The distribution of elements in the different area of the brazed coatings was determined by energy dispersive X‐ray maps. It shows that the segregation of chromium carbides occurs during brazing. Apart from penetrating into the interspaces of WC particles, the Ni‐based filler can also infiltrate and spread on the substrate surface. Copyright © 2012 John Wiley & Sons, Ltd.     

Characterization of Nanocomposite Coatings in the System Ti–B–N by Analytical Electron Microscopy and X-Ray Photoelectron Spectroscopy

Summary.  Superhard nanocomposite coatings of different composition in the quasi-binary system TiN–TiB₂ were deposited onto stainless steel sheets by means of unbalanced DC magnetron co-sputtering using segmented TiN/TiB₂ targets. The chemistry and microstructure of a TiB_0.6N_0.7 coating was investigated using X-ray and electron diffraction, photoelectron spectroscopy, energy-filtering transmission electron microscopy, and electron energy-loss spectrometry. High resolution elemental mapping of the elements Ti, B, N, and O with energy-filtering TEM reveals a homogeneous distribution on the nanometer scale. X-Ray and electron diffraction exhibit only TiN crystallites of nanometer size, but no information on the boron-rich phase. The near-edge fine structures of the BK and NK ionization edges in the EELS spectra of the Ti–B–N coatings were used to derive information on the phases by comparing the edges with those of reference compounds. It was found that the TiN nanocrystals occur together with TiO _x particles; the grains are embedded in a strongly disordered or quasi-amorphous matrix consisting mainly of TiB₂ particles and, near the steel substrate, also boron oxide (B₂O₃). Received October 4, 2001. Accepted (revised) January 10, 2002     

Polypropylene filled with flame retardant fillers: mechanical and fracture properties

Two grades of isotactic polypropylene (homopolymer and block copolymer) were filled with magnesium and aluminium hydroxides, and studied focusing the mechanical and fracture characteristics of the composites. As expected, dispersion of such fillers in PP resulted in improved stiffness and reduced tensile yield strength. By one hand, the composites fracture resistance was characterised at low strain rate applying the J‐integral concept; the resistance to crack growth initiation (J_IC) was found decreasing as the Mg(OH)₂ concentration was raised in the copolymer PP matrix. By the other hand, the linear‐elastic fracture mechanics (LEFM) parameters were determined by means of instrumented impact tests at 1 m/s on the homopolymer PP filled with uncoated Al(OH)₃ particles. The higher the Al(OH)₃ mean particle size, the lower the composite fracture energy (G_IC). In the opposite, with commercial surface‐coated filler grades it was not possible to achieve LEFM conditions to characterise the fracture toughness of filled PP at 1 m/s, because the Mg(OH)₂ surface coating, which is applied in practice to improve the melt processing, acts increasing the composite plasticity and reducing the tensile yield strength.     

Enhanced surface free energy of UHMWPE fibers and its interfacial adhesion behavior to PI resins

Mechanical properties of composites made up of ultra‐high‐molecular‐weight polyethylene (UHMWPE) fiber, polyimide (PI), and TiO₂ particles were investigated. The hybrid composite of 20 vol% of UHMWPE fiber with TiO₂ showed tensile strength greater than UHMWPE fiber/PI composite. A positive hybrid effect in tensile strength is obtained. It is observed that addition of small amount of TiO₂ to UHMWPE fiber/PI increased the tensile strength of the composite by 28%. With increase in TiO₂ loading to 1 to 3 vol%, the impact strength of the hybrid composite is increased from 55 KJ/m² to 69 KJ/m². This maximum value is more than one and a half times greater than the impact strength of neat UHMWPE fiber/PI composite.     

Enhanced Thermal Stability in SiO2/Carbon Filler Derived from Rice Husk via Microwave Treatment for Electronic Packaging Application

Here we report the effect of microwave treatment on a silica–carbon (SiO₂ /C) filler derived from rice husk and the function of the microwave‐treated filler in an epoxy matrix for electronic packaging applications. Thermogravimetric analysis revealed improved thermal stability of the SiO₂ /C filler upon microwave treatment. X‐ray diffraction analysis indicated partial SiC formation after the microwave treatment. For packaging applications, compared to that of the pure epoxy polymer, the thermal conductivity of the epoxy–SiO₂ /C composite was improved by 178% at 40 wt % content of the microwave‐treated SiO₂ /C filler. Furthermore, an improvement of 149% in storage modulus and 17.6°C in glass transition temperature of the epoxy–SiO₂ /C composites was realized. The improvement in thermal stability of SiO₂ /C filler could be achieved via a simple microwave treatment, which in turn enhanced the thermal stability, thermal conduction, and thermomechanical strength of the electronic packaging materials.     

Electrorheological properties of carbon nanotube/polyelectrolyte self‐assembled polystyrene particles by layer‐by‐layer assembly

Sulfonated polystyrene (PS) particles were prepared by the sulfonation of PS microspheres with H₂SO₄. Then, composite particles were synthesized by layer‐by‐layer (LbL) self‐assembly with funtionalized multiwall carbon nanotubes (fMCNTs) and polyelectrolytes on sulfonated PS particles. The amount of fMCNTs on PS particles was adjusted by controlling the number of fMCNT layers by LbL self‐assembly. Composite particles were characterized by ζ‐potential analysis, scanning electron microscopy, and thermal analysis. The electrorheological (ER) properties of composite particles in insulating oil was investigated with varying the number of fMCNT layers under controlled electric fields. It was observed that the number of fMCNT layers was a critical factor to determine the ER properties of composite particles. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1058–1065, 2008     

Enhancement of the thermal and mechanical properties of a surface‐modified boron nitride–polyurethane composite

Thermoplastic polyurethane (PU) elastomer, prepared from poly(tetramethylene glycol) and methyl diphenyl diisocyanate, was blended with boron nitride (BN) to fabricate a thermally conductive interface material. BN treated by a silane coupling agent (BN―NH₂) and PU‐grafted BN were prepared to fabricate a composite that has better thermal conductivity and mechanical strength. The surface‐modified filler showed enhanced dispersibility and affinity because of the surface treatment with functional groups that affected the surface free energy, along with the structural similarity of the doped crystallized diisocyanate molecule with the matrix. The thermal conductivity increased from 0.349 to 0.467 W mk^?1 on 20 wt% PU‐grafted BN loading that is a 1.34‐fold higher value than in the case of pristine BN loading at the same weight fraction. Moreover, the number of BN particles acting as defects, thereby reducing the mechanical strength, is decreased because of strong adhesion. We can conclude that these composite materials may be promising materials for a significant performance improvement in terms of both the thermal and mechanical properties of PU‐based polymers. Copyright © 2014 John Wiley & Sons, Ltd.