This work was supported by the Taiyuan University of Science and Technology Scientific Research Initial Funding (20182028), the doctoral starting foundation of Shanxi Province (20192006), the Natural Science Foundation of Shanxi Province (201703D111003), the Science and Technology Major Project of Shanxi Province (MC2016-01), and Project U610256 supported by National Natural Science Foundation of China.

1. Surface modification of BT fillers
<ol>
	<li>Prepare 20 mL of KH550 solution (1 wt% KH550 in 95 wt% ethanol-water solvent) and ultrasonicate for 15 min.</li>
	<li>Weigh BT nanoparticles (i.e., the filler) and KH550, respectively, so that fillers can be coated with 1, 2, 3, 4, 5 wt% of the coupling agent. Treat 1 g of BT nanoparticles in 1.057, 2.114, 3.171, 4.228, and 5.285 mL of KH550 solution by 30 min ultrasonication.</li>
	<li>Evaporate the water-ethanol solvent from the mixture at 80 &#176;C for 5 h and then at...

<ol>
	<li>Lines, M. E., Glass, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Principles and applications of ferroelectrics and related materials. , (2001).</li><li>Nalwa, H. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Handbook of low and high dielectric permittivity materials and their applications, phenomena, properties and applications. , (1999).</li><li>Kao, K. 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As discussed above, the method developed by this work could successfully improve the energy-storage performance of ceramic-polymer nanocomposites. To optimize the effect of such method, it is critical to control the amount of coupling agent used in ceramic-surface modification. For ceramic nanoparticles with a diameter of ~200 nm, it was experimentally determined that 2 wt% of KH550 could lead to a maximal energy density. For other composite systems, this conclusion may be used approximately when the fillers with the dia...

The dielectrics applied in electrical energy storage devices are mainly characterized using two important parameters: the dielectric constant (&#949;r) and the breakdown strength (Eb)1,2,3. In general, organic materials such as polypropylene (PP) exhibit a high Eb (~102 MV/m) and a low &#949;r (mostly &#60;5)4,5,6 while inorganic materials, especially ferroelectrics such as BaTiO3, exhibit a high &#949;r (103-104) and a low Eb (~100 MV/m)6,7,8. In some applications, flexibility and the ability to withstand high mechanical impacts are also important for fabricating dielectric capacitors4. Therefore, it is important to develop methods for preparing polymer-based dielectric composites, especially for the development of low-cost methods to create high-performance 0-3 nanocomposites with high &#949;r and Eb9,10,11,12,13,14,15,16,17,18. For this purpose, preparation methods based on ferroelectric polymer matrices such as the polar polymer PVDF and its correlated copolymers are widely accepted due to their higher &#949;r (~10)4,19,20. In these nanocomposites, particles with high er, especially ferroelectric ceramics, have been widely used as fillers6,20,21,22,23,24,25.
When developing methods for manufacturing ceramic-polymer composites, there is a general concern that dielectric properties can be significantly influenced by the distribution of fillers26. The homogeneity of dielectric composites is not only determined by the preparation methods, but also by the wettability between the matrix and fillers27. It has been proven by many studies that the non-uniformity of ceramic-polymer composites can be eliminated by physical processes such as spin-coating28,29 and hot-pressing19,26. However, neither of these two processes change the surface connection between fillers and matrices; therefore, the composites prepared by these methods are still limited in improving &#949;r and Eb19,27. Additionally, from a manufacturing point of view, inconvenient processes are undesirable for many applications because they can lead to much more complex fabrication processes28,29. In this regard, a simple and effective method is needed.
Currently, the most effective method to improve the compatibility of ceramic-polymer nanocomposites is based on the treatment of ceramic nanoparticles, which modifies the surface chemistry between fillers and matrices30,31. Recent studies have shown that coupling agents can be easily coated on ceramic nanoparticles and effectively modify the wettability between fillers and matrices without affecting the casting process32,33,34,35,36. For surface modification, it is widely accepted that for each composite system, there is a suitable amount of coupling agent, which corresponds to a maximal increase in energy storage density37; excess coupling agent in composites may result in a decline in the performance of products36,37,38. For dielectric composites using nano-sized ceramic fillers, it is speculated that the effectiveness of coupling agent mainly depends on the surface area of fillers. However, the critical amount to be used in each nano-sized system is yet to be determined. In short, further research is required to use coupling agents to develop simple processes for manufacturing ceramic-polymer nanocomposites.
In this work, BaTiO3 (BT), the most widely studied ferroelectric material with high dielectric constant, was used as fillers, and the P(VDF-CTFE) 91/9 mol% copolymer (VC91) was used as the polymer matrix for the preparation of ceramic-polymer composites. To modify the surface of the BT nanofillers, the commercially available 3-aminopropyltriethoxysilane (KH550) was purchased and used as a coupling agent. The critical amount of the nanocomposite system was determined through a series of experiment. An easy, low-cost, and widely applicable method is demonstrated to improve the energy density of nano-sized composite systems.

<table border="0" cellpadding="0" cellspacing="0" style="width:827px;" width="826">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">3-Aminopropyltriethoxysilane (KH550)</td>
			<td style="width:184px;">Sigma-Aldrich</td>
			<td style="width:161px;">440140</td>
			<td style="width:223px;">Liquid, Assay: 99%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">95 wt.% ethanol-water</td>
			<td style="width:184px;">Sigma-Aldrich</td>
			<td style="width:161px;">459836</td>
			<td>Liquid, Assay: 99.5%</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:259px;">BaTiO3 nanoparticles</td>
			<td style="width:184px;">US Research Nanomaterials</td>
			<td style="width:161px;">US3830</td>
			<td>In a diameter of about 200 nm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">Ferroelectric tester</td>
			<td style="width:184px;">Radiant</td>
			<td style="width:161px;">Precision-LC100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">Glass substrates</td>
			<td style="width:184px;">Citoglas</td>
			<td style="width:161px;">16397</td>
			<td>75 x 25 mm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">Gold coater</td>
			<td style="width:184px;">Pelco</td>
			<td style="width:161px;">SC-6</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">High voltage supplier</td>
			<td style="width:184px;">Trek</td>
			<td style="width:161px;">610D</td>
			<td>10 kV</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">Impedance analyzer</td>
			<td style="width:184px;">Keysight</td>
			<td style="width:161px;">4294A</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">N, N dimethylformamide</td>
			<td style="width:184px;">Fisher Scientific</td>
			<td style="width:161px;">GEN002007</td>
			<td>Liquid</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">P(VDF-CTFE) 91/9 mol.% copolymer</td>
			<td style="width:184px;"></td>
			<td style="width:161px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">Scanning Electron Microscopy (SEM)</td>
			<td style="width:184px;">JEOL</td>
			<td style="width:161px;">JSM-7000F</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:259px;">Vacuum oven</td>
			<td style="width:184px;">Heefei Kejing Materials Technology Co, Ltd</td>
			<td style="width:161px;">DZF-6020</td>
			<td></td>
		</tr>
	</tbody>
</table>

application of a coupling agent to improve the dielectric properties of polymer-based nanocomposites

In this work, an easy, low-cost, and widely applicable method was developed to improve the compatibility between the ceramic fillers and the polymer matrix by adding 3-aminopropyltriethoxysilane (KH550) as a coupling agent during the fabrication process of BaTiO3-P(VDF-CTFE) nanocomposites through solution casting. Results show that the use of KH550 can modify the surface of ceramic nanofillers; therefore, good wettability on the ceramic-polymer interface was achieved, and the enhanced energy storage performances were obtained by a suitable amount of the coupling agent. This method can be used to prepare flexible composites, which is highly desirable for the production of high-performance film capacitors. If an excessive amount of coupling agent is used in the process, the non-attached coupling agent can participate in complex reactions, which leads to a decrease in dielectric constant and an increase in dielectric loss.

The free-standing nanocomposite films with different contents of fillers were successfully fabricated as described in the protocol, and were labeled as xBT-VC91, where x is the volume percentage of BT in the composites. The effect of KH550 (coupling agent) on the morphology and microstructure of these BT-VC91 films was studied by SEM and shown in Figure 1. The SEM images of 30BT-VC91 nanocomposites with 1 and 5 wt% coupling agent are shown in Figure 1a and <stro...

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Application of a Coupling Agent to Improve the Dielectric Properties of Polymer-Based Nanocomposites

Here, we demonstrate a simple and low-cost solution-casting process to improve the compatibility between the filler and the matrix of polymer-based nanocomposites using surface modified BaTiO3 fillers, which can effectively enhance the energy density of the composites.

In this work, an easy, low-cost, and widely applicable method was developed to improve the compatibility between the ceramic fillers and the polymer ...

It was proved that the using of commercial coupling agent could modify the surface of ceramic nanofillers, therefore, good wettability on the ceramic-polymer interface was achieved, and the enhanced energy storage performances were obtained by a suitable amount of coupling agent. The method developed by this work could be used in the preparation of flexible composites, which is highly desirable for the production of high-performance film capacitors. Prepare the solution of KH550 with 95 weight percent ethanol water solvent by 15 minutes ultra-sonication.Treat the BT nanoparticles in KH550 solutions by 30 minutes ultra-sonication. In this process, measure the weights of KH550 and BT nanoparticles fillers coated with one, two, three, four, and five weight percent of coupling agent in the KH550 dilute solution with a volume of five milliliter. Evaporate the water-ethanol solvent from the matrix at 80 degrees C for five hours, and then to 120 degrees C for 12 hours in a vacuum oven.Use the dry nanoparticles as the surface modified fillers in the preparation of BTVC-91 nanocomposites. One, the DMF-based polymer solution was prepared by dissolving 0.3 grams of polymer powders in 10 milliliter DMF at room temperature by a magnetic stirring for eight hours. Two, the barium titanate nanoparticles were added into the solution, then followed with 12 hours stirring to form homogeneous suspension and ultrasonicated for 30 minutes.In the preparation process, both the unmodified barium titanate and the barium titanate coated with coupling agent were used. After that, the suspension was cast on a preheated class substrate to make films. Three milliliters of the suspension was dropped on each of the glass substrate.Five, the glass substrate with suspensions was then kept in the oven at 70 degree for eight hours to evaporate the solvent. Six, finally, the as-cast films were released from the glass substrate and obtained free-standing films were annealed at 160 degrees C in air for 12 hours. The free-standing nanocomposite films was successfully fabricated according to the protocol.It was confirmed from the SEM that the ceramic nanoparticles treated with a suitable amount of coupling agent that could be uniformly distributed in the nanocomposites during casting;while the excessive amount of coupling agent may cause interactions between ceramic nanoparticles and leading to the aggregation of fillers. For the nanocomposites with low filler content, the dielectric constant of the composites was basically unchanged with a small amount of coupling agent is used and slightly decreases with the future increasing coupling agent amount. For the nanocomposites with high filler content, the dielectric constant of the composites increase adversely with a small amount of coupling agent and sharply decrease with the future increasing coupling agent amount.In terms of dielectric loss, the nanocomposites with coupling agent have a higher dielectric loss than the nanocomposites without coupling agent. The maximal breakdown strengths was obtained when two weight percent of coupling agent was used. A lower breakdown strengths was found from the nanocomposites with a higher amount of coupling agent.Due to the enhanced breakdown strengths and our relatively high charge discharge efficiency, the maximal energy density of the nanocomposites with a small amount of coupling agent were improved. In this work, barium titanate, the most widely studied ferroelectric material with high dielectric constant were used as fillers. The PVDF-CTFE copolymer was used as a polymer matrix for the preparation of ceramic polymer composites.To modify the surface of barium titanate nanofillers, the commercially available KH550 were purchased and used as coupling agent. They critical amount of the nanocomposite system was determined by the series of experiment. An easy, low-cost, and the widely applicative method to improve the energy density of nano-sized composite system was demonstrated.

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5.7K vues.  Taiyuan University of Science and Technology. Il a été prouvé que l’utilisation de l’agent de couplage commercial pouvait modifier la surface des nanofillers en céramique, par conséquent, une bonne wettabilité sur l’interface céramique-polymère a été réalisée, et les performances améliorées de stockage d’énergie ont été obtenues par une quantité appropriée d’agent couplage. La méthode développée par ce travail pourrait être utilisée dans la préparation de composites flexibles, ce qui est hautement souha...