Preface:
BaTiO3 is a ceramic material with excellent piezoelectric and dielectric properties, while epoxy resin is a commonly used engineering plastic with good heat resistance and mechanical properties. By combining the two, composite materials with excellent electrical and mechanical properties can be obtained.
Epoxy resins are a widely used material, but epoxy resins have limitations in terms of brittleness upon failure, so researchers explore toughening and strengthening options, such as adding a second phase or using electromagnetic fields, tailoring toughness and strength to needs and almost instantaneously.
To promote uniform dispersion and distribution, Si-BaTiO3 nanoparticles are functionalized by silane coupling agents and mixed in epoxy resin LY1564 under different content loads.
When an electric field is applied to a nanocomposite sample, real-time measurements are performed using Raman spectroscopy. This provides valuable insights into how to actively improve the mechanical properties of epoxy composites, especially in relatively low-field and thin, high-aspect ratio composite layers, which require in situ mechanical testing equipped with electric field applications, which is currently being investigated.
The effect of rubber flexibilizer on epoxy resin
Fiber-reinforced polymer (FRP) composites are commonly used in high-performance applications due to their strength and modulus. FRP composites are mainly made of thermosetting epoxy resin, have a highly crosslinked structure, and also have superior properties.
However, brittleness in the transverse direction is a reason to limit its failure, especially when exposed to shock loads or high strain rates. In order to improve the performance of polymer matrices in composite manufacturing, the researchers focused on adding micro-nano and nano-fillers, such as rubber flexibilizers.
To improve the performance of polymer matrices, researchers have explored several methods in fiber-reinforced composites. These materials include the addition of rubber tougheners or nanoparticles, as well as silica particles, carbon nanoparticles, clay and fiber coatings to the matrix.
In addition, it is challenging in composite manufacturing as an alternative method for modifying fiber properties. By adding rubber tougheners, nanoparticles, silica particles, carbon nanoparticles, clay, and fiber coatings to the polymer matrix. And by modifying the curing process, researchers can adjust the mechanical properties of fiber-reinforced composites.
This includes enhanced stiffness and toughness, which are critical for many applications. These technologies are an alternative method for modifying the properties of fibers in composite manufacturing, and in order to improve the fracture toughness of composite materials, rubber toughening agents such as core-shell rubber or liquid rubber are added to the polymer matrix.
These fortifiers help absorb energy and reduce stress concentration. Studies have shown that the addition of rubber flexibilizer to epoxy resin can significantly improve the fracture toughness of composites by up to 200%. This method is an effective way to improve the mechanical properties of composite materials without changing the fiber properties in the manufacturing process.
Although the addition of rubber tougheners to polymer matrices in composites can improve fracture toughness, once a certain concentration threshold is exceeded, it will lead to particle agglomeration, resulting in mechanical degradation and reduced strength.
Despite certain challenges, the addition of rubber flexibilizers is still a promising method to improve the mechanical properties of epoxy composites. To prevent agglomeration of rubber flexibilizers in the polymer matrix, surface modifications and a variety of flexibilizers can be used.
Couplants can improve the adhesion between particles and substrates in epoxy composites and can also lead to a decrease in elastic modulus, tensile strength, and glass transition temperature. A previous method of prestressing and strengthening epoxy matrix in a composite by heating expandable hollow microspheres.
This method is a new method that can improve the mechanical properties of composites while avoiding the potential drawbacks of other toughening methods. Phase change toughening and conversion toughening are two technologies to improve the toughness of polymer matrix composites.
Phase change toughening uses expandable microspheres to induce the volume expansion effect. The performance of the composite material is significantly improved, however this method may lead to weight gain. Compromise in mechanical properties, transition toughening involves the formation of a second stage under stress, creating a compressive force around the crack tip and resisting crack propagation.
This mechanism can effectively improve the fracture toughness of a variety of materials, including ceramic and polymer matrix composites. Preliminary steps for developing active toughening of Si-batio3-epoxy nanocomposites under relatively low electric field conditions.
Real-time in situ Raman spectroscopy was used to measure the response of silicon-batio3-epoxy nanocomposites under electric field stimulation. Current studies on the activity toughening of epoxy nanocomponents provide valuable insights.
As the electric field strength and barium titanate content increase, its strength remains consistent. The hardening tendency caused by the softening effect caused by the dipole displacement in BATIO3 in high-content nanocomposites may not be applicable to other nanocomposites.
Preheat treatment hydroxylation process
The method described here is for pretreatment and purification of barium titanate nanoparticles, rather than for incorporation of nanoparticles into epoxy matrix.
For pretreatment of barium titanate nanoparticles, 10 g of nanoparticles are added to a 230 mL solution of hydrogen peroxide (hydrogen peroxide) in a round-bottom flask. The mixture is sonicated in an ultrasonic bath for 30 min, then refluxed with 30% hydrogen peroxide solution stirred at 100 rpm for 6 h at 108 °C.
The purpose of reflux is to facilitate this process by heating without losing hydrogen peroxide, centrifugation at 4500 rpm for 15 min after 6 h, recovery of barium titanate nanoparticles, and then washing three times with deionized water. The purified barium titanate nanoparticles are dried in an oven at 80 °C for 24 h.
Preparation of silane-modified barium titanate (Si-BaTiO3).
3-Glycoxypropyltrimethoxysilane (3-GPS) was used to improve the processing performance and dispersion of barium titanate nanoparticles in nanocomposites, and the solution of silane was used to reflow barium titanate.
Mix the low pH solution with 150 mL of aqueous ethanol and deionized water (9:1) until the pH reaches 3.5-4. Add 0.1 g of 3-GPS solution to acidified solution, soak in ultrasonic bath for 30 min to form a homogeneous solution, and then add hydroxylated barium titanate powder particles to silane solution and mix under ultrasonic bath for 10 min to improve the wettability of the filler. The mixture is refluxed at ethanol boiling temperature to 78 °C at 100 rpm using a mechanical stirrer for 6 h.
After reflux, Si-BaTiO3 powder was washed 3 times with deionized water and recovered by centrifugation at 4500 rpm. Finally, the powder is dried at 110 °C for 24 h to avoid any condensation of the silanol group on the surface and crushed in a mortar and pestle to prepare the nanocomposite.
By FTIR analysis, silane treatment was confirmed. The FTIR spectra of barium titanate-400-4000 cm-1 were then measured in transmission mode by Jasco FT/IR-6200 with a resolution of 2 cm−1.
FTIR spectra peaked at 1437 cm-1 and 1630 cm−1, respectively, indicating physical absorption of water on barium carbonate and barium titanate powders, which is the result of the combustion manufacturing process. The band at 3200-3700 cm−1 confirmed the presence of hydroxyl groups in the Si-OH group.
The spectral bands at 850 cm−1 and 1250 cm−1 confirmed the success of silane modification of barium titanate, indicating vibrations of Si-O, Si-O-C2H5 and Si-O.
Preparation of silane-modified barium titanate
Epoxy resin nanosuspension with untreated barium titanate nanoparticles, prepared as follows: First, weigh the barium titanate powder with ethanol and sonicate with an ice water bath for 2 min for 10s pulse to form a homogeneous solution.
Add the weighed epoxy resin to the solution, stir under a fume hood with a mechanical stirrer at 300 rpm and 80 °C, and remove the non-precipitating particles from the ethanol. The epoxy mixture is weighed before and after solvent evaporation to ensure complete removal of ethanol.
Then the curing agent is added to the mixture according to the company's recommended weight ratio and stirred for another 3 minutes. Finally, the mixture is placed in a vacuum oven at 30 °C for 1 h to remove air bubbles at 29 inHg, thus completely removing ethanol.
The entire mixture is poured into a mold made of two pieces of glass sandwiched with a 3 mm silicone gasket sandwiched in between. This setup guarantees a uniform thickness of the specimen, which is then cured for 8 hours in an oven at 80°C according to the manufacturer's recommended method.
After cooling to room temperature, it has been scanned according to scanning calorimetry to ensure that the final degree of healing is achieved using the determined process parameters. Several studies have provided valuable properties for batio3-epoxy composites and introduced a new sensor placement method.
In another study, the researchers developed a method that involves adding piezoelectric particles to a polymer matrix and squeezing the mixture into the fibers. By using unsintered PZT and barium titanate calcined powder, the resulting ferroelectric hybrid fibers become flexible and soft.
The researchers studied the electromechanical behavior of these fibers under different electric fields and found that they could reach 10% of the maximum polarizability observed in the sintered corresponding fibers. This method has broad prospects in the development of flexible and lightweight materials with piezoelectric properties.
There are potential applications in information storage, computing, and neuromorphic systems, and it has been reported about "in-plane charged domain walls with memory behavior in ferroelectric films".
Researchers believe that there is a nonlinear relationship between the polarization of in-plane charged domain walls in ferroelectric films that remember behavior and the applied voltage and hysteresis. They used conductive atomic force microscopy (CAFM) to study the local current-voltage (I-V) properties of charged DWs.
Mount the sample on a round, metal holder and connect to the internal source electrode of the AFM. A commercial silicon tip coated with Pt is used to measure the current and the specimen is biased from an internal source. Ferroelectric films exhibit memory behavior, with a nonlinear relationship between polarization and applied voltage and hysteresis.
Using conductive atomic force microscopy (CAFM) to study the local current-voltage (I-V) properties of charged DWs, the sample is mounted on a round metal holder and connected to the internal source electrode of the AFM.
A commercial silicon tip coated with Pt is used to measure the current and the specimen is biased from an internal source. The bias sweep is performed in positive and negative voltage circles for 100 s (0.1 V s−1), the current measurement limit is 100 μΑ, and the material responds to an electric field with a strong polarization potential (i.e., kV/cm>10).
Electric field-induced Raman spectroscopy
Raman spectroscopy is a non-destructive technique that detects the vibrational patterns of materials. It is widely used in the characterization of materials because it can provide information about their molecular and crystal structure, as well as the presence of any residual strain.
For Raman spectroscopy measurements, the choice of excitation wavelength is critical, and 514 nm is a common choice due to its balance between resolution and signal intensity. In situ Raman spectroscopy with electrical connections was used to study the polarization behavior of nanocomposites in the presence of an applied electric field.
For this purpose, the voltage applied to the specimen varies between 0V, 6V, 9 and 24 V. The use of in situ Raman spectroscopy makes it possible to monitor in real time any changes in the vibration patterns of materials under the influence of an applied electric field.
The setup of in situ Raman spectroscopy typically involves applying a voltage to the sample using an electrode while obtaining a Raman spectrum. The development of in situ electric field equipping dielectric nanocomposites is an advanced method for studying batio3-epoxy composites and provides a remote performance cutting technique.
To achieve and quantify this response before proposing remote cutting innovations for engineering applications, the change in mechanical properties of intrinsic strain in thin epoxy nanocomposites in the presence of low electric fields.
Feasibility studies were carried out on the embedding of 1, 5 and 10 wt% barium titanate nanoparticles into epoxy nanocomposites, and high-performance grades for advanced and rigid structures were selected for epoxy grades.
summary
In the preparation of nanocomposites, Raman spectroscopy was performed to improve the interfacial particle-matrix bonding quality and its dispersion in epoxy resin.
These results show intrinsic tensile effects caused by electric fields. At the interatomic crystal level, it may contribute to mechanical softening effects and reduce mechanical properties, which need to be further studied. In order to achieve the excellent performance of BaTiO3-epoxy nanocomposites, in-depth research on material synthesis, nanocomposite process and interface strengthening is required.
In addition, the preparation and application of composite materials also need to consider factors such as durability, stability and cost-effectiveness of materials. BaTiO3-epoxy nanocomposites have broad prospects and can be applied to electronic devices, piezoelectric transducers, sensors, dielectric materials and microwave absorbing materials, but further research and development are still needed to realize their potential.