Preparation by melt mixing and characterization of isotactic polypropylene/SiO2 nanocomposites containing untreated and surface‐treated nanoparticles

In the present study two series of isotactic polypropylene (iPP)/SiO₂ nanocomposites containing 1, 2.5, 5, 7.5, and 10 wt % SiO₂ nanoparticles were prepared by melt‐mixing on a twin‐screw corotating extruder. In the first series untreated fumed silica nanoparticles were used, whereas in the second nanoparticles were surface‐treated with dimethyldichlorosilane. In both cases, the average size of the primary nanoparticles was 12 nm. Tensile and impact strength were found to increase and to be affected mainly by the type and content of silica nanoparticles. A maximum was observed, corresponding to samples containing 2.5 wt % SiO₂. These findings are discussed in light of the SEM and TEM observations. By increasing the amount of nanoparticles, large aggregates of fumed silica could be formed, which may explain the reduction of mechanical properties with higher concentrations of SiO₂. However, it was found that surface‐treated nanoparticles produced larger aggregates than did those derived from untreated nanoparticles, despite the increased adhesion of the iPP matrix, as was postulated from yield strength. This behavior negatively affected mechanical properties. In addition, an effort was made to determine if toughening theories, mainly the critical interparticle distance for rubber toughening or composites, also might be applicable in nanocomposites. From DSC measurements it was demonstrated that silica nanoparticles acted as effective nucleating agents, increasing the crystallization rate and the degree of crystallinity of iPP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2684–2696, 2006     

Enhanced interfacial strength and mechanical properties of carbon fiber composites by introducing functionalized silica nanoparticles into the interface

Introducing nanoparticles onto the surface of carbon fibers (CFs) is a useful method for enhancing the quality of fiber-matrix interface. In this work, a liquid sizing agent containing functionalized silica nanoparticles (SiO₂) was well prepared to improve interfacial strength and mechanical properties of composites. In order to enhance the dispersion of SiO₂ nanoparticles in sizing agent, SiO₂ nanoparticles were chemically grafted with 3-aminopropyltriethoxysilane (APS), and then silanized silica (SiO₂-APS) was introduced into the interphase by a conventional sizing process as well. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) confirmed the successful preparation of SiO₂-APS. Scanning electron microscopy (SEM) showed that a uniform distribution of SiO₂-APS on the fiber surface and the increased surface roughness. The sized fibers (CF/SiO₂-APS) exhibited a high surface free energy and good wettability based on a dynamic contact angle testing. Interfacial microstructure and mechanical properties of untreated and sized CFs composites were investigated. Simultaneous enhancements of interlaminar shear strength (ILSS) and impact toughness of CF/SiO₂-APS composites were achieved, increasing 44.79% in ILSS and 31.53% in impact toughness compared to those of untreated composites. Moreover, flexural strength and modulus of composites increased by 32.22 and 50.0% according to flexural test. In addition, the hydrothermal aging resistance of CF/SiO₂-APS composites has been improved significantly owing to the introduced Si-O-Si bonds at the interface.     

Alumina ceramic tool material with enhanced properties through the addition of bionic prepared nano SiC@graphene

Graphene-coated SiC nanoparticles containing graphene floating bands (SiC@G) were prepared by a liquid-phase laser irradiation technique, and SiC@G nanoparticles with high dispersivity were incorporated into an Al₂O₃ matrix. An Al₂O₃-based composite ceramic tool was prepared by spark plasma sintering (SPS), and the effects of SiC@G nanoparticles on the mechanical and cutting properties and microstructure of the materials were further investigated. Analysis of the cross-sectional morphology shows that SiC@G nanoparticles containing graphene floating bands were homogeneously dispersed in the composite, which resulted in tighter bonds between the Al₂O₃ particles. This particular core-shell structure increased the contact area between the graphene and the matrix due to the formation of a graphene 3D mesh by extrusion, which enhanced the difficulty of relative sliding of graphene. Second, this special core-shell structure also made the crack propagation path more tortuous, further increasing the energy consumed in the fracture process, which is conducive to improving the mechanical properties of ceramic tools. The addition of SiC@G nanoparticles improves the mechanical properties of Al₂O₃-based composite ceramic tools. The fracture toughness (7.2 Mpa·m^1/2) and flexural strength (709 MPa) increased by 75.6% and 28.7%, respectively. Cutting experiments with Al₂O₃/SiC/G composite ceramic tool and Al₂O₃/SiC@G composite ceramic tools on 40Cr hardened steel were performed. The results prove that the addition of SiC@G nanoparticles improves the cutting life by 18.1% and reduces the cutting force and friction coefficient by 6.3% and 14.8%, respectively.     

Effect of TiO2 nanoparticles on the horizontal hardness properties of Sn-3.0Ag-0.5Cu-1.0TiO2 composite solder

The improvement in the hardness of Sn-3.0Ag-0.5Cu solder alloy reinforced with 1.0 wt % TiO₂ nanoparticles was evaluated by nanoindentation. A specific indentation array was performed on four different horizontal cross sections of the composite solder with different heights and diameters, in order to verify the mixing homogeneity of TiO₂ nanoparticles within the Sn-3.0Ag-0.5Cu solder paste during the ball milling process. The phase analysis indicated successful blending of the Sn-3.0Ag-0.5Cu with the TiO₂ nanoparticles. According the scanning electron microscopy micrographs, presence of the TiO₂ nanoparticles reduced the size of the Cu₆Sn₅ and Ag₃Sn intermetallic compound phases. Incorporation of the 1.0 wt % TiO₂ nanoparticles improved the hardness values up to 26.2% than that of pure SAC305. The hardness values increased gradually from the top cross sections towards adjacent to the solder/substrate interface. The mechanism of the hardness improvement attained by the TiO₂ nanoparticles addition were also investigated on the horizontal cross sections of the samples.     

Reinforcement of the mechanical properties in nitrile rubber by adding graphene oxide/silicon dioxide hybrid nanoparticles

Graphene oxide (GO) and silicon dioxide (SiO₂) nanoparticles have been hybridized for improving the mechanical and dynamic mechanical properties of nitrile rubber (NBR). SiO₂ nanoparticles were homogeneously dispersed on the surface and between layers of GO, and the new hybrid nanoparticles formed (GO/SiO₂₎ had better thermal stability than GO. To evaluate the mechanical properties, GO/SiO₂/NBR nanocomposites were prepared by solution blending and mechanical solution methods. It was observed that tensile strength increased in a larger grade in GO/SiO₂/NBR nanocomposites than that in GO/NBR and SiO₂/NBR nanocomposites, while the elongation at break only changes smoothly. Moreover, dynamics measurements also indicated that the elasticity increased after adding GO/SiO₂ hybrid nanoparticles in NBR. From morphology's analysis of GO/SiO₂/NBR and GO/NBR nanocomposites, it is was conclude that the hybridization of the GO/SiO₂ was the determining factor for the reinforcement of the mechanical properties and elasticity of the NBR. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46091.     

3D printing ceramic cores for investment casting of turbine blades,using LCD screen printers: The mixture design and characterisation

The primary objective of this study is to demonstrate the possibility of developing silica, alumina, and zircon-based photocurable ceramic suspensions that can be used for visible light photopolymerization (> 450 nm) and to optimise the binder formulations for the purpose of LCD-based ceramic 3D printing applications. Reference ceramic components for this work are ceramic cores employed in the investment casting of high-pressure turbine blades and vanes. Arguably, one of the most critical steps in photoinduced ceramic 3D printing is developing suitable ceramic suspensions, having high ceramic loading, low viscosity, and short curing times. Ceramic suspensions with four different novel binder formulations and commercial ceramic powders used in core manufacturing (SiO₂, Al₂O₃ and ZrSiO₄) were investigated to achieve the best trade-off between: (1) their curing performance (cure depth and curing speed), (2) rheological properties of the binder mixtures at the solid loadings of 60 vol.% for SiO₂, 55 vol.% for ZrSiO₄, and 45 vol.% for Al₂O₃; and (3) the green body mechanical properties of the mixtures after printing. The effect of ceramic particles on the selected binders was examined individually, and the correlation between cure depth (C_d), volumetric loading, and curing speed are evaluated. The results show all binders designed in this study provide an adequate cure depth, even at high ceramic loadings. When the curing behaviour of all unloaded binder mixtures from the previous study [1] compared with the 10 vol.% SiO₂ loaded mixtures, the cure depth of all formulated binder mixtures increased 50–55 % and the curing thickness of 60 vol.% SiO₂ loaded suspensions were still slightly higher than their unloaded counterparts. The rheology outcomes indicate that lower viscosity binders always result in lower viscosity of the ceramic loaded inks, even without taking the effect of dispersants into account. Besides, the addition of N-Vinyl-2-Pyrrolidone (NVP) monofunctional monomer to the binder mixtures significantly reduces the viscosity and changes the normally linear relationship of the mix viscosity and its silica loading content. Among the binder formulations loaded with 60 vol.% of SiO₂, the formulation providing the lowest viscosity and highest mechanical property consists of 5 wt.% of NVP, 45 wt.% of HDDA and 50 wt.% of Photocentric 34 resin. Although this binder mixture showed the highest green flexural strength when loaded by 55 vol.% ZrSiO₄, all other mixtures loaded with zircon flour also demonstrated a near-fluid behaviour, below 200 s^?1. In Al₂O₃ loaded mixtures, the HDDA di-functional binder formulations present lowest viscosity and the di- and multifunctional monomer blends (HDDA-Photocentric27) showed the highest mechanical properties when used in a 50/50 ratio. This work summarises the best binder choices for silica, alumina and zircon based ceramic suspensions used in core printing for investment casting applications through LCD screen printing.     

The influence of Al2O3 nanoparticles addition on the microstructure and properties of bauxite self–flowing low-cement castables

In this research, the impact of Al₂O₃ nanoparticles addition on microstructure, mechanical, and physical properties of bauxite self–flowing low-cement castables were investigated. Also, the optimum amount of Al₂O₃ nanoparticles is determined. For this propose, up to 3 wt% Al₂O₃ nanoparticles were added to the bauxite castable compositions. The physical and mechanical properties of castable compositions such as bulk density (BD), apparent porosity (AP), self-flow values (SFV), and cold crushing strength (CCS) were examined. Also, the X-ray diffraction (XRD) and scanning electron microscopy (SEM/EDX) techniques were used for detection the ceramic phase's formation and microstructural analysis of the castables compositions, respectively. Results show that addition of Al₂O₃ nanoparticles up to 1 wt% improved the properties of bauxite self–flowing low-cement castables. As well as, the use of Al₂O₃ nanoparticles led to the formation of the platy and needle crystalline phases such as hibonite (CaO·6Al₂O₃), calcium dialuminate (CaO·2Al₂O₃), and mullite (3Al₂O₃·2SiO₂), between the grain boundaries of the bauxite particles. Also, Al₂O₃ nanoparticles addition led to aforementioned phase formation occur at the lower temperatures.     

Development of an aluminum/amorphous nano-SiO2 composite using powder metallurgy and hot extrusion processes

Ceramic nanoparticle reinforced aluminum matrix composites usually exhibit superior mechanical properties when compared to monolithic materials, particularly in severe working conditions such as elevated temperatures. Aluminum matrix nano-composites (AMNCs) are widely used for structural applications in aerospace and automotive industries due to their low density and high strength to weight ratio. The aim of this research was to study the effect of SiO₂ nanoparticles as the reinforcing phase on the mechanical properties of aluminum matrix composites. For this purpose, powder metallurgy and subsequent hot extrusion methods were used to prepare a reference sample and several Al-SiO₂ nano-composite rods, containing 1, 2 and 3 wt% nano-silica. Some sample preparation procedures for the manufacturing process, involved mixing, compaction, sintering, preheating and hot extrusion. Mechanical properties of the developed composites were investigated by macro- and micro-hardness, density measurement, tensile, cold compression and hot compression tests. A scanning electron microscope and an optical microscope were used for microstructural analysis of the composite and monolithic samples before and after the hot extrusion process. Experimental tests on aluminum matrix composites reinforced with nano SiO₂ particles revealed that adding just 1 wt% SiO₂ nanoparticle increases both hardness and tensile strength by 41.8% and 24.8%, respectively. In addition, the mechanical properties were seen to decrease with increases in the SiO₂ weight fraction. Density also decreased as the SiO₂ weight fraction increased. It can therefore be said that based on the findings of this study, the SiO₂ nanoparticle can be used as an effective reinforcing material for developing aluminum matrix nano-composites.     

Design and Properties of New Lead-Free Solder Joints Using Sn-3.5Ag-Cu Solder

This article aims to reduce the melting temperature of lead-free solder alloy and promote its mechanical properties. Eutectic tin-silver lead-free solder has a high melting temperature 221 ^°C used for electronic component soldering. This melting temperature, higher than that of lead–tin conventional eutectic solder, is about 183 ^°C. The effect of the melt spinning process and copper additions into eutectic Sn-Ag solder enhances the crystallite size to about 47.92 nm which leads to a decrease in the melting point to about 214.70 ^°C, where the reflow process for low heat-resistant components on print circuit boards needs lower melting point solder. The results showed the presence of intermetallic compound Ag₃Sn formed in nano-scale at the Sn-3.5Ag alloy due to short time solidification. The presence of new intermetallic compound, IMC from Ag_0.8Sn_0.2 and Ag phase improves the mechanical properties, and then enhances the micro-creep resistance especially at Sn-3.5Ag-0.7Cu. The higher Young’s modulus of Sn-3.5Ag-0.5Cu alloy 55.356 GPa could be attributed to uniform distribution of eutectic phases. Disappearance of tin whiskers in most of the lead-free melt-spun alloys indicates reduction of the internal stresses. The stress exponent (n) values for all prepared alloys were from 4.6 to 5.9, this indicates to climb deformation mechanism. We recommend that the Sn_95.7-Ag_3.5-Cu_0.7 alloy has suitable mechanical properties, low internal friction 0.069, low pasty range 21.7 ^°C and low melting point 214.70 ^°C suitable for step soldering applications.     

Tribological properties of bismaleimide composites with surface‐modified SiO2 nanoparticles

In this article, the surface of SiO₂ nanoparticles was modified by silane coupling agent N‐(2‐aminoethyl)‐γ‐aminopropylmethyl dimethoxy silane. The bismaleimide nanocomposites with surface‐modified SiO₂ nanoparticles or unmodified SiO₂ nanoparticles were prepared by the same casting method. The tribological performance of the nanocomposites was studied on an M‐200 friction and wear tester. The results indicated that the addition of SiO₂ nanoparticles could decrease the frictional coefficient and the wear rate of the composites. The nanocomposites with surface‐modified SiO₂ nanoparticles showed better wear resistance and lower frictional coefficient than that with the unmodified nanoparticles SiO₂. The specific wear rate and the steady frictional coefficient of the composite with 1.0 wt % surface‐modified SiO₂ nanoparticles are only 1.8 × 10^?6 mm³/N m and 0.21, respectively. The dispersion of surface‐modified SiO₂ nanoparticles in resin matrix was observed with transmission electron microscope, and the worn surfaces of pure resin matrix and the nanocomposites were observed with scanning electron microscope. The different tribological behavior of the resin matrix and the filled composites should be dependent on their different mechanical properties and wear mechanism. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Improving the Mechanical Properties of Poly Methyl Methacrylate Nanocomposites for Dentistry Applications Reinforced with Different Nanoparticles

Properties of poly methyl methacrylate are improved using different nanoparticles for denture applications and the best combination is selected using multi-criteria decision-making methods. For these purposes, poly methyl methacrylate is melt compounded with TiO₂, SiO₂, and Al₂O₃ nanoparticles and then injection molded. The results of mechanical tests revealed that by addition of TiO₂ and SiO₂, the impact strengths of poly methyl methacrylate were increased 229 and 62%, respectively. Also, the results indicated a significant improvement in Young’s modulus and hardness. The implementation of multi-criteria decision-making methods illustrated that TiO₂ nanoparticles are the best candidate for improving the properties of poly methyl methacrylate for dental applications.     

Influence of ceramic phase content and its morphology on mechanical properties of MgO–C refractories under high temperature nitriding

To evaluate the influences of ceramic phase content and its morphology on the mechanical properties of MgO–C refractories, pre-prepared Si powder-phenolic resin loaded with Fe₂O₃ was introduced to prepare MgO–C refractories via catalytic nitridation. The effects of nitriding temperature and Fe₂O₃ content on the phase composition, microstructure evolution and properties of MgO–C refractories were studied and compared. The results show that the increase of the nitriding temperature was conducive to the in-situ formation of the ceramic phases, and a new phase of Mg₂SiO₄ was formed at temperatures ≥1450 °C. Both the increase in nitriding temperature and the addition of catalyst could inhibit the growth of α-Si₃N₄ to promote the formation of β-Si₃N₄ and MgSiN₂. In addition, the formation of excessive ceramic phases caused samples after nitriding to expand violently and form more porous, thereby reducing the physical properties of MgO–C refractories.     

In situ hot pressing/reaction synthesis,mechanical and thermal properties of Lu2SiO5

Lu₂SiO₅ is a promising candidate of environmental barrier coatings (EBC) for silicon based ceramics due to its excellent high temperature stability. However, little information is available for the mechanical and thermal properties of Lu₂SiO₅, which frustrated evaluation of its performances for EBC applications. In this paper, dense Lu₂SiO₅ ceramic is successfully fabricated from Lu₂O₃ and SiO₂ powders by in situ hot pressing/reaction sintering at 1500 °C. Mechanical properties, including Young's modulus, bulk modulus, shear modulus, Poisson's ratio, fracture toughness, Vickers hardness, and bending strength are reported for the first time. Lu₂SiO₅ possesses excellent high temperature mechanical properties up to at least 1300 °C. Thermal stress for the case of Lu₂SiO₅ or Y₂SiO₅ coating on silicon bond coat and thermal stress resistance parameter are also estimated based on the experimental mechanical and thermal properties. The present results suggest that Lu₂SiO₅ has better reliability than Y₂SiO₅ in harsh thermal environment.     

Investigation of the mechanical properties of a photocatalytic pseudo‐paint

Photocatalytic oxidative paints (e.g., a paint containing nano‐TiO₂) are used to break down volatile organic compounds to CO₂ by photooxidation reactions. In this research, a photocatalytic oxidative pseudo‐paint was made with acrylic–styrene copolymer latex, TiO₂ pigment, calcium carbonate extender, and TiO₂ nanoparticles as a photocatalyst. To investigate the effects of the pigment, extender, and nanoparticles on the mechanical properties of the samples and their relationship to their photocatalytic activity, different contents of the particles were dispersed in the paint formulation. The tensile strengths (TSs) of the samples were measured as the mechanical properties. The samples were characterized by scanning electron microscopy analysis. We found that up to 3% nano‐TiO₂ enhanced the mechanical properties of the pigmented resin, whereas beyond this, TS decreased. In samples containing 3% nanoparticles, the incorporation of 15% TiO₂ pigment caused optimized mechanical properties, and beyond that, TS decreased because of particle agglomeration. In the absence of nanoparticles, the samples showed improvements in the mechanical properties with up to a 40% loading of pigment. The results reveal that the samples containing nano‐TiO₂ and pigment showed the same trend for the mechanical and photocatalytic properties before the critical pigment volume concentration (CPVC). However, when the extender was incorporated or TiO₂ particles were loaded beyond CPVC, the mechanical and photocatalytic properties correlation was compromised, and they were not directly correlated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42885.     

Ionic conductivity and electrochemical properties of nanocomposite polymer electrolytes based on electrospun poly(vinylidene fluoride-co-hexafluoropropylene) with nano-sized ceramic fillers

A series of nanocomposite polymer electrolytes (NCPEs) comprising nanoparticles of BaTiO₃, Al₂O₃ or SiO₂ were prepared by electrospinning technique. The nano-sized ceramic fillers were incorporated into poly(vinylidene fluoride-co-hexafluoropropylene) [P(VdF-HEP)] membranes during the electrospinning process. The resultant porous membranes are good absorbent of the liquid electrolyte and exhibit high electrolyte retention capacity. The presence of the ceramic nanoparticles has positive effect on the mechanical properties of the membranes. The ionic conductivity and the electrochemical stability window of the electrospun P(VdF-HFP)-based polymer are enhanced by the presence of the fillers. The cell Li/LiFePO₄ based on the NCPE containing BaTiO₃ delivers a discharge capacity of 164 mAh/g, which corresponds to 96.5% utilization of the active material. In comparison, the performance of Li/LiFePO₄ cells with NCPEs containing Al₂O₃ and SiO₂ was observed to be lower with respective discharge capacities of 153 and 156 mAh/g. The enhanced performance of the BaTiO₃-based-NCPE is attributed mainly to its better interaction with the host polymer and compatibility with lithium metal.     

The effect of silica (SiO2) nanoparticles and ammonia/ethylene plasma treatment on the interfacial and mechanical properties of carbon-fiber-reinforced epoxy composites

A nanoparticle dispersion is known to enhance the mechanical properties of a variety of polymers and resins. In this work, the effects of silica (SiO₂) nanoparticle loading (0–2 wt%) and ammonia/ethylene plasma-treated fibers on the interfacial and mechanical properties of carbon fiber–epoxy composites were characterized. Single fiber composite (SFC) tests were performed to determine the fiber/resin interfacial shear strength (IFSS). Tensile tests on pure epoxy resin specimens were also performed to quantify mechanical property changes with silica content. The results indicated that up to 2% SiO₂ nanoparticle loading had only a little effect on the mechanical properties. For untreated fibers, the IFSS was comparable for all epoxy resins. With ethylene/ammonia plasma treated fibers, specimens exhibited a substantial increase in IFSS by 2 to 3 times, independent of SiO₂ loading. The highest IFSS value obtained was 146 MPa for plasma-treated fibers. Interaction between the fiber sizing and plasma treatment may be a critical factor in this IFSS increase. The results suggest that the fiber/epoxy interface is not affected by the incorporation of up to 2% SiO₂ nanoparticles. Furthermore, the fiber surface modification through plasma treatment is an effective method to improve and control adhesion between fiber and resin.     

Fabrication and Dielectric,Mechanical, and Thermal Properties of Low-Density Polyethylene (LDPE) Composites Containing Surface-Passivated Silicon (Si/SiO2 Core/Shell Nanoparticles)

Composites of low-density polyethylene containing between 1 and 5?wt% of Si/SiO₂ core/shell nanoparticles were prepared by ball milling method. The thermal, mechanical, and dielectric properties of composites were investigated in terms of composition, frequency, and temperature. The results showed that the dielectric permittivity increased smoothly with a rise of Si/SiO₂ particle. The dielectric permittivity and loss decreases and increases with temperature, respectively. The resistance of composites to erosion due to partial discharge was significantly improved by adding nanoparticles. The results have demonstrated that ball milling was an effective method for producing relatively homogeneous nanocomposite up to 4?wt% Si/SiO₂.     

Comparison of microstructure,toughness, mechanical properties and work hardening of titanium/TiO2 and titanium/SiC composites manufactured by accumulative roll bonding (ARB) process

In this study, the effects of TiO₂ ceramic nanoparticles and SiC microparticles on the microstructure, mechanical properties and toughness of titanium/TiO₂ nanocomposite and titanium/SiC composite were investigated. To achieve this goal, TiO₂ and SiC ceramic particles were incorporated as the reinforcement in titanium through the ARB (accumulative roll bonding) process. By adding SiC ceramic particles, the mechanical properties of the composite and the nanocomposite were enhanced, while their toughness was decreased, as compared to TiO₂ nanoparticles. After applying 8 cycles of the ARB process, UTS in Ti/5 vol% SiC composite reached to about 1200 (MPa), as compared to that in Ti/0.5 wt% TiO₂ nanocomposite, which was about 1100 (MPa). Furthermore, toughness in the Ti/5 vol% SiC composite and the Ti/0.5 wt% TiO₂ nanocomposite was 60 and 29 J/m³, respectively. Finally, SEM and TEM images showed SiC microparticles clustering in Ti/SiC composite samples and a suitable distribution of TiO₂ nanoparticles in the Ti/TiO₂ nanocomposite. By adding TiO₂ nanoparticles, mechanical properties and work hardening coefficient were found to be increased, as compared to those of the monolithic samples. TiO₂ nanoparticles, after being distributed in the titanium matrix through the ARB process, caused pin dislocations. As clearly shown in TEM images, dislocation tangles around TiO₂ nanoparticles acted as the main mechanism improving the work hardening coefficient.     

Large electrostrictive effect and energy storage density in MnCO3 modified Na0.325Bi0.395Sr0.245□0.035TiO3 lead-free ceramics

The Na_0.325Bi_0.395Sr_{0.245□0.035}TiO₃ + x % MnCO₃ (NBST-100xMn) lead-free ceramic samples had been fabricated by solid-state reaction method. Microstructure and electrical properties with the addition of MnCO₃ had been studied in detail. The NBST-4Mn showed a low hysteresis behavior with the maximum electrostrictive coefficient (Q) of 0.0294 m⁴/C² and the recoverable energy storage density (W_rec) of 1.3 J/cm³ at 95 kV/cm. In addition, the electrostrictive effect and energy storage ability presented outstanding temperature stability and fatigue resistance, which indicated a promising lead-free ceramic for high precise actuator.     

Ultrasonic dual mode mixing and its effect on tensile properties of SiO2-epoxy nanocomposite

Dispersion of nanoparticles and its effect on the tensile properties were investigated by preparing nanocomposites via mechanical mixing (MM) and optimized ultrasonic dual mode mixing (UDMM) routes. The MM of SiO₂ nanoparticles in epoxy resin was employed using glass rod stirring and the UDMM was employed by ultrasonic vibration along with magnetic stirring to produce SiO₂-epoxy nanocomposite. Taguchi method was used for optimization of the process parameters of UDMM route considering the tensile strength of the base epoxy. Field emission scanning electron microscopy (FE-SEM) micrographs revealed an improved dispersion quality of SiO₂ nanoparticles especially for the UDMM route. Consequently, quality of dispersion affects tensile strength (max 49.2%) along with ductility and absorbed failure energy at low nanoparticle content. Moreover, elastic modulus increases with increasing content of nanoparticle, e.g. in one case 62.55% for 20?wt.% of SiO₂ nanoparticles.