Effect of nanodiamond surface functionalization using oleylamine on the scratch behavior of polyacrylic/nanodiamond nanocomposite

Addition of hard particles such as nanodiamonds to polymers to improve their physical and mechanical properties is very common. However, nanodiamonds are usually hydrophilic so their tendency to form agglomerates in a polymeric matrix is quite strong. In this study, the effect of nanodiamond surface modification on its uniform dispersion in a polymeric matrix such as polyacrylic-base polymer clear coat was investigated. For this purpose, detonation nanodiamond (DND) with an average particle diameter of 4–6 nm was used. To improve dispersion of as-received DND (AR-DND) in the polymeric matrix, the surfaces of the particles were modified by heat treatment (oxidation) in air and followed by functionalization using oleylamine (OLA) as surfactant. So, nanocomposites with different contents of AR-DND, HT-DND and OLA treated HT- DND (OLA-HT-DND) particles were produced. Their characterizations were investigated by employing many analytical methods such as: Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and thermo-gravimetry analysis (TGA). Scratch resistance test and study of coating surfaces, using scanning tunneling microscopy (STM), were carried out on the polymeric nanocomposites. The results showed that the surface-functionalized nanodiamonds are highly dispersive and stable in the polymeric matrix. In addition, scratch resistance was increased with the addition of nanoparticles.     

Effect of heat treatment on the microstructural change of syndiotactic polystyrene/poly(styrene-co-vinyloxazolin)/clay nanocomposite

The fabrication of a syndiotactic polystyrene (sPS)/organoclay nanocomposite was conducted via a stepwise mixing process using poly(styrene-co-vinyloxazolin) (OPS), i.e. melt intercalation of OPS into organoclay followed by blending with sPS. The effects of several parameters, including type of organoclay and mixing temperature on the microstructure of the nanocomposite were investigated through X-ray diffraction patterns and rheological properties. The microstructure of the nanocomposite mainly depended on the arrangement type of the organic modifiers in the clay gallery. Using organoclays having lateral a bilayer arrangement exfoliated structure was obtained, whereas intercalated structure were obtained when organoclay with a paraffinic monolayer arrangement was employed in our sPS/OPS/organoclay system. In this work, a simple heat treatment on a previously prepared OPS/organoclay nanocomposite induced microstructural evolution with a favorable direction from intercalation to exfoliation. This phenomenon is attributed to a strong interaction between OPS and the clay surfaces, which is revealed by plateau behavior of the storage modulus in rheological properties. When heat is applied to the OPS/organoclay, the OPS chains and clay layers move together by promoted thermal motion of OPS chains, which results in disordering of stacked clay layers and exfoliation.     

Effect of normal scratch load and HF etching on the mechanical behavior of annealed and chemically strengthened aluminosilicate glass

Micro-cracks generated by hard body scratch are a major cause of strength decrease for silicate glass. The influence of normal scratch load on the cracking patterns and flexural strength of annealed glass (AG) and chemically strengthened glass (CSG) were studied. With the increase of the normal load, the load capacity of scratched AG specimens decreased to about 40 MPa at 20gf immediately. However, the residual strength of CSG decreased to a steady value of 145 MPa as the scratch load increased to 500gf. Then the effect of hydrofluoric acid (HF) etching on the surface morphology and mechanical properties of the 500gf scratched glass were investigated. After 8min (for CSG) and 16 min (for AG) acid treatment, the flexural strength of CSG and AG increased to a considerable value of 900 MPa, which is 3.6 and 5.5 times higher than the flexural strength of undamaged specimens. Microscopic observations show that the blunting and eliminating of median cracks as well as the formation of new surfaces are the main causes of strength enhancement.     

Effect of heat treatment on the tribological behavior of 2D carbon/carbon composites

The effect of high temperature heat treatment on the tribological behavior of carbon/carbon (C/C) composites has been investigated. C/C composite preforms were made from 1K PAN plain carbon cloth, and densified using rapid directional diffusion (RDD) CVI processes. Four specimens treated at 1800, 1800+2000, 2000, and 2300 °C, respectively, were prepared. A ring-on-ring specimen configuration was used to simulate aircraft brakes. The brake initial angular velocity ranged from 1800 to 7500 rpm (6.2-26.0 m s⁻¹ average linear sliding velocity). The specific pressure and moment of inertia were 392-784 kPa and 0.25-0.31 kg m², respectively (1.9-42.3 MJ m⁻² kinetic energy loading per unit friction surface area). The results showed that the stability of the brake moment-time curves increased with increasing heat treatment temperature (HTT) for the four composites, and those treated at 2300 °C possessed the lowest initial brake moment peak ratio values (from 1.1 to 1.3). The high degree of graphitization and low shear forces of the matrix carbon resulting from the high HTT could allow friction films to develop and reduce those values under the present brake conditions. The friction coefficients of four RDD CVI C/C composites decreased with an increase in specific pressure. The resulting changes in the friction coefficient of the four composites due to the specific pressure changes have basically nothing to do with the interface temperature under those conditions. According to the practical brake conditions, the friction properties of RDD CVD C/C composites could be improved by regulating the structure of the brake discs, changing the specific pressure exerted on the discs and the heat treatment. The linear wear rates of the four materials increased with increasing HTT. The composites treated at 2000 °C had both high enough friction coefficients and the lower linear wear rates. The different heat treatment methods at 2000 °C had no obvious effect on the friction and wear properties of RDD CVI C/C composites.     

Effect of silane functionalization of montmorillonite on epoxy/montmorillonite nanocomposite

Mechanical and dynamic mechanical properties of various montmorillonite (MMT)/epoxy nanocomposites were investigated. 3-aminopropyltriethoxysilane functionalized MMT was compared with commercial pristine MMT and ammonium salt substituted MMT. Qualitative evidence of silane functionalization was confirmed by FT-IR. XRD and TEM were used to characterize the degree of intercalation of MMT in epoxy nanocomposite. Tensile stress and elongation of MMT/epoxy nanocomposite were improved significantly by the silane functionalization of MMT. Dynamic mechanical analysis showed that silane functionalization of MMT resulted in active interactions between MMT and epoxy.     

Investigation of the corrosion protection behavior of natural montmorillonite clay/bitumen nanocomposite coatings

The influence of clay particles on the corrosion properties of bituminous coating was studied. Different percentages of natural montmorillonite clay (Cloisite Na⁺) were added to emulsified bitumen in water to make 2 wt.%, 3 wt.% and 4 wt.% of clay/bitumen nanocomposite coatings. The coatings were applied on steel 37. Optical microscopy and transmission electron microscopy (TEM) were employed to study the structure of nanocomposite. To investigate the anti-corrosion properties of the coated panels, electrochemical impedance spectroscopy (EIS) was used. The findings indicated that the addition of clay nanolayers improved corrosion resistance of the coatings. Moreover, increasing clay loading up to 4 wt.%, increased the corrosion resistance.     

Effect of heat treatment on the microstructure and strength of yttrium silicate matrix-modified SiCf/SiC composites

Yttrium silicate was introduced into the matrix of SiC_f/SiC composites via the slurry impregnation and reactive chemical vapor infiltration (RCVI) methods to improve the water and oxygen corrosion resistance of the modified composite materials. The effects of heat treatment on the modified matrix and strength of the composites were systematically investigated. The results showed that the modified matrix was composed of a mixture of yttrium monosilicate, yttrium disilicate, and silicon carbide. The modified yttrium silicate matrix (named Y-Si-O matrix) and the silicon carbide matrix were laminated and well combined. After heat treatment, the amount of Y-Si-O in the mixed matrix increased. The modified composites with yttrium silicate had a similar flexural strength as SiC_f/SiC composites (∼400 MPa). After treated at 1000 °C – 1300 °C, the strength of the modified composites increased by 17 %–26 %. The highest strength was measured for composites treated at 1200 °C.     

Review on the effect of heat exchanger tubes on flow behavior and heat/mass transfer of the bubble/slurry reactors

Bubble/Slurry bubble column reactors(BCR/SBCR) are intensively used as multiphase reactors for a wide range of application in the chemical, biochemical and petrochemical industries. Most of these applications involve complicate gas–liquid/gas–liquid–solid flow behavior and exothermic process, thus it is necessary to equip the BCR/SBCR with heat exchanger tubes to remove the heat and govern the performance of the reactor. Amounts of experimental and numerical studies have been carried out to describe the phenomena taking place in BCR/SBCRs with heat exchanger tubes. Unfortunately, little effort has been put on reviewing the experiments and simulations for examining the effect of internals on the performance and hydrodynamics of BCR/SBCR. The objective of this work is to give a state-of-the-art review of the literature on the effects of heat exchanger tubes with different types and configurations on flow behavior and heat/mass transfer, then provide adequate information and scientific basis for the design and the development of heat exchanger tubes in BCR/SBCR, ultimately provide reasonable suggestions for better comprehend the performance of different heat exchanger tubes on hydrodynamics.     

Effect of heat treatment on synthetic carbon precursors

Carbonaceous materials obtained from polyethyleneterephthalate (PET), a potential precursor for polymer-based carbon, were studied after heat treatment at 750, 900 and 1200 °C in an inert atmosphere. The carbon content increases to more than 95% (w/w) already at the lowest temperature applied. The surface area decreases from 242 to 14.7 m²/g between 750 and 1200 °C, causing also a reduced pore volume and the conversion of open to closed pores. The pore structure exhibits a gate effect. The carbon matrix contains both amorphous and semicrystalline regions. The spatial extent of the latter can be described by a Maxwellian distribution with a maximum of 12 Å at the lowest and 17 Å at the highest temperature values. Increasing the temperature from 900 to 1200 °C does not increase the size of these domains but yields a more ordered carbon skeleton. In the WAXS spectrum a flat diffuse peak about 3.5-4.0 Å corroborates that the graphitic domains are of colloidal size. The immersional wetting enthalpies determined in water, methanol and benzene indicate that the surface has an amphoteric character and that the carbon structure and surface chemistry are strongly affected by the heat treatment processes.     

Effect of SiC coating and heat treatment on the thermal radiation properties of C/SiC composites

The effects of SiC coating and heat treatment on the emissivity were investigated for 2D C/SiC composites prepared by CVI in the 6–16 μm range. SiC coating had an obvious effect on the spectral emissivity of the composites but caused just 5% difference in the total emissivity. A radiation transport model was applied to explain those changes caused by SiC coating. Heat treatment affected the thermal radiation properties of the composites through the microstructure evolution. Base on the complementary analytical techniques, the changes in the emissivity were attributed to a good graphitization degree of carbon phases, large β-SiC grain sizes and high α-SiC content resulting in high emissivity.     

Effect of heat treatment on the performance of TiO2-Pt/CNT catalysts for methanol electro-oxidation

TiO₂-Pt/CNT catalysts before and after heat treatment were prepared. Their catalytic activities for methanol and CO electro-oxidation were studied in detail. The results showed that the proper amount of hydrous TiO₂ in TiO₂-Pt/CNTs (e.g. heated at 200 °C for 2 h) was favorable for enhancing the catalytic activity of Pt/CNTs, which provided evidence for bi-functional mechanism. The studies on the catalysts with different TiO₂/Pt molar ratio displayed that the optimum molar ratio varied with the increase of heat treatment temperature. It was found that the optimum molar ratio of TiO₂/Pt was at 1:2 for the catalysts without heat treatment and was at 1:1 for the catalysts by heat treatment at 500 °C. This fact was ascribed to the difference in compact degree between TiO₂ and Pt/CNTs before and after heat treatment. Considering the influence of heating temperature, it was found that TiO₂-Pt/CNT catalyst heated at 200 °C for 2 h had better catalytic activity for methanol oxidation.     

热处理对聚乙烯醇薄膜性能的影响

对聚乙烯醇薄膜进行了热处理,并测试了热处理后薄膜的力学、光学及电学性能,结果表明:增加热处理时间与升高热处理温度对改变聚乙烯醇薄膜的力学性能、光学性能和表面电阻率等效;随着热处理时间的增加或热处理温度的升高,其力学性能增强,光学性能略有下降,表面电阻率增大。     

Effect of nanoparticles on heat capacity of nanofluids based on molten salts as PCM for thermal energy storage

In this study, different nanofluids with phase change behavior were developed by mixing a molten salt base fluid (selected as phase change material) with nanoparticles using the direct-synthesis method. The thermal properties of the nanofluids obtained were investigated. These nanofluids can be used in concentrating solar plants with a reduction of storage material if an improvement in the specific heat is achieved. The base salt mixture was a NaNO₃-KNO₃ (60:40 ratio) binary salt. The nanoparticles used were silica (SiO₂), alumina (Al₂O₃), titania (TiO₂), and a mix of silica-alumina (SiO₂-Al₂O₃). Three weight fractions were evaluated: 0.5, 1.0, and 1.5 wt.%. Each nanofluid was prepared in water solution, sonicated, and evaporated. Measurements on thermophysical properties were performed by differential scanning calorimetry analysis and the dispersion of the nanoparticles was analyzed by scanning electron microscopy (SEM). The results obtained show that the addition of 1.0 wt.% of nanoparticles to the base salt increases the specific heat of 15% to 57% in the solid phase and of 1% to 22% in the liquid phase. In particular, this research shows that the addition of silica-alumina nanoparticles has a significant potential for enhancing the thermal storage characteristics of the NaNO₃-KNO₃ binary salt. These results deviated from the predictions of the theoretical model used. SEM suggests a greater interaction between these nanoparticles and the salt.     

Effect of current density and deposition time on microstructure and corrosion resistance of Ni-W/TiN nanocomposite coating

Ni-W/TiN nanocomposite coatings were successfully prepared via pulse electroplating from an electrolyte containing suspended TiN nanoparticles. The effects of applied current density and deposition time on microstructure, morphology, composition, hardness and electrochemical behaviors of the obtained coatings were investigated. Results showed that the current density and deposition time affect remarkably the electrochemical co-deposition process and then the structure and characteristics of the composites. It illustrated that the nanocomposites are uniform, compact and crack-free. The nanocomposites prepared at I_a =?3?A?dm^?2 and t?=?20?min had the finest structure, showing a fine and smooth surface. EDS mapping and XPS spectra illustrated that the TiN nanoparticles had been homogeneously dispersed throughout the coating. 2.34?wt% TiN nanoparticles were embedded in Ni–W (68.56?wt% Ni and 29.1?wt%?W) alloy matrix at I_a=?3.0?A?dm^?2. The inclusion of TiN nanoparticles in Ni–W could promote the nucleation and cause a distinct microstructural change. The crystallite size was in the range of 11–15?nm. The average roughness value (R_a) is 65.7?nm and 73.8?nm for coating formed at 20?min and 40?min, respectively. The electrochemical measurements illustrated that I_a =?3–5?A?dm^?2 and t?=?40–60?min was the optimal operating parameters for the excellent anti-corrosion properties of Ni–W/TiN nanocomposites. The embedded TiN in Ni–W matrix could fill defects then improve its corrosion resistance. This electrodeposited Ni–W/TiN nanocomposites possess excellent hardness and superior corrosion resistance, and is expected to be applied in aggressive environment as a protective coating.     

Synthesis of La1-xGdxFe1-yCoyO3/r-GO nanocomposite with integrated features for the treatment of hazardous industrial effluents

Solar-light triggered semiconductive materials with a small bandgap, a low electron-hole pair recombination rate, and quicker charge carrier characteristics are very efficient catalysts for hazardous industrial effluent treatment. Herein, we adopted wet-chemical and ultra-sonication techniques to prepare binary metal (Gd & Co) doped Lanthanum ferrite (GCLFO) nanoparticles and their reduced-graphene (r-GO) based nanocomposite (GCLFO/r-GO) as an ideal photocatalyst. The binary metal doping and composite formation strategies were adopted primarily to facilitate the electronic excitation and accelerate the charge transport characteristics of the finally obtained photocatalyst. Prepared solid samples were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), Raman, Fourier transform-infrared (FT-IR), current-voltage (I–V), BET (Brunauer, Emmett, and Teller), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy. An improvement in the photo-degradation of Phenol Red (PR) dye by GCLFO/r-GO nanocomposite was observed. The increased photocatalytic activity of the GCLFO/r-GO nanocomposite is primarily a result of doping, nanotechnology, and composite formation strategies. These strategies tune the bandgap of the nanocomposite sample, increase its surface area, and decrease its electrical resistivity. Highly encouraging photocatalytic findings suggest that using multiple strategies to prepare an ideal photocatalytic material with integrated features is a very efficient approach.     

Preparation of PANI/epoxy/Zn nanocomposite using Zn nanoparticles and epoxy resin as additives and investigation of its corrosion protection behavior on iron

Conducting polyaniline, zinc and epoxy resin solely have anticorrosive properties by different mechanisms on metallic substrates. In this work the triple hybrid of PANI/epoxy/Zn nanocomposite was prepared as a thin layer coating (70 ± 5 μm) on iron coupons and its anticorrosion performance was investigated in HCl (0.1 M) as corrosive solution. Epoxy resin and zinc nanoparticles were applied as additives in the PANI matrix to improve the mechanical properties of PANI coating and investigate their synergetic effects on the anticorrosion performance of PANI coating. At first PANI/Zn nanocomposite coatings with different Zn contents were prepared and the zinc content optimized so that the coating achieve the best anticorrosion performance. Accordingly the iron coupons coated by PANI/Zn coating having 4 wt% Zn content showed more noble open circuit potential and lower corrosion current values. Then epoxy resin was applied as additive to the optimized formulation of PANI/Zn coating in different weight percents (0–20 wt%) and the anticorrosion performance of the related PANI/epoxy/Zn triple hybrid nanocomposite coatings was evaluated. Results showed that the addition of epoxy resin causes to the decreasing of corrosion current of iron samples coated by PANI/epoxy/Zn nanocomposite. An optimum range of 3–7 wt% was obtained for the epoxy content in the composition of PANI/epoxy/Zn nanocomposite in which the coating exhibits the best anticorrosion performance. Iron metal coupon was elementally analyzed and the PANI/Zn and PANI/epoxy/Zn nanocomposites were characterized using Fourier Transform Infrared spectroscopy, X-ray diffraction patterns and Scanning Electron Microscopy techniques.     

Effect of heat treatment atmosphere on the piezoresistivity of indium tin oxide ceramic strain sensor

Indium tin oxide (ITO) strain sensors were prepared by RF magnetron sputtering, and then heat treated in nitrogen and air atmosphere, respectively. The effect of air and N₂ heat treatment on the piezoresistivity of ITO ceramic strain sensors were investigated at 1200 °C. It was found that although both the ITO ceramic strain sensors heat treated in N₂ and air had similar temperature coefficient of resistance (TCR), the ITO strain sensor heat treated in N₂ had better resistance stability. In addition, the ITO strain sensor heat treated in N₂ had a smaller but more stable gage factor, compared to that in air. These observations were attributed to the increased content of Sn⁴⁺ donors and the enhanced photon scattering due to smaller grain sizes after the incorporation of nitrogen into ITO lattice.     

Effect of alumina nanoparticles in the fluid on heat transfer in double-pipe heat exchanger system

This study was performed to investigate the convective heat transfer coefficient of nanofluids made of several alumina nanoparticles and transformer oil which flow through a double pipe heat exchanger system in the laminar flow regime. The nanofluids exhibited a considerable increase of heat transfer coefficients. Although the thermal conductivity of alumina is not high, it is much higher than that of the base fluids. The nanofluids tested displayed good thermal properties. One of the possible reasons for the enhancement on heat transfer of nanofluids can be explained by the high concentration of nanoparticles in the thermal boundary layer at the wall side through the migration of nanoparticles. To understand the enhancement of heat transfer of nanofluid, an experimental correlation was proposed for an alumina-transformer oil nanofluid system.     

Investigation of surface modification of rutile TiO2 nanoparticles with SiO2/Al2O3 on the properties of polyacrylic composite coating

Surface modification and characterization of TiO₂ nanoparticles as an additive in a polyacrylic clear coating were investigated. For the improvement of nanoparticles dispersion and the decreasing of photocatalytic activity, the surface of nanoparticles was modified with binary SiO₂/Al₂O₃. The surface treatment of TiO₂ nanoparticles was characterized with FTIR. Microstructural analysis was done by AFM. The size, particle size distribution and zeta potential of TiO₂ nanoparticles in water dispersion was measured by DLS method. For the evaluation of particle size and the stability of nanoparticles in water dispersions with higher solid content the electroacoustic spectroscopy was made. To determine the applicability and evaluate the transmittance of the nano-TiO₂ composite coatings UV–VIS spectroscopy in the wavelength range of 200–800 nm was employed. The results showed that surface treatment of TiO₂ nanoparticles with SiO₂/Al₂O₃ improves nanoparticles dispersion and UV protection of the clear polyacrylic composite coating.     

Effect of clay treatment on structure and mechanical behavior of elastomer-containing polyamide 6 nanocomposite

The effect of clay organophilization on mechanical behavior and structure of PA6/EPR blends was studied. It has been shown that the modification of clay affected simultaneously the degree of PA6 matrix reinforcement, size and structure of dispersed EPR. The localization of clay with less polar treatment in the interfacial area brought an important new effect consisting intensification of toughening effect of dispersed elastomer by formation of “core-shell” particles. Basic aspects governing formation of this advantageous structure are reported.The best balanced mechanical behavior was achieved when combining two differently modified clays, whereas the clay with less polar treatment is preblended with EPR. In this way, a high degree of matrix reinforcement (exfoliation of clay with more polar treatment) was combined with favorable size and structure of dispersed EPR phase. Additionally, at lower clay content, synergy between clay and elastomer phase, monitoring itself by enhancement of toughness, was found.