Synthesis, characterization and USW sensor of PEO/PMMA/PVP doped with zirconium dioxide nanoparticles

The piezoelectric phenomena uses in various helpful applications, such as printing of piezoelectric inkjet, the detection of sound and the production of high voltage electricity in different electronic devices. In present research, polyethylene oxide (PEO), poly(methyl methacrylate) (PMMA) and poly(N-vinyl pyrrolidone) (PVP) were separately dissolved in deionized water. These polymers were mixed with ratio of 0.6:0.2:0.2 wt%, respectively before loaded with 0.0, 0.02, 0.04 and 0.06 wt% of zirconium dioxide nanoparticles (ZrO2NPs) via casting method to prepare nanocomposite (NCs) films. The optical microscope (OM) showed good diffused of the NPs into matrix with homogenous distribution. The functional groups of k1 specimen were diagnosed via Fourier transformation infrared (FTIR). The ultrasonic wave (USW) properties were studied for k1 specimen with various frequencies (25, 30, 35, 40 and 45) kHz. The USW coefficients were clearly affected by the frequency varied. The USW coefficients decreased with increasing the frequency except the compressibility. The dielectric constant of the k1 sample was notable improved up to 85% with increasing of applied load. The k1 specimen was succeeded to be used as USW sensor. New NCs film presented as promising material for wide electrical and mechanical applications.


Introduction
The piezoelectric effect or USW sensor, known as the direct piezoelectric effect, is an electricity generating phenomena which occurs when a material exposed to external pressure, mechanical stress or applied force. polyethylene oxide (PEO), which is synthesized from polyether polymer (PE) [1], has many important applications in treatment of water, pipes industries, physical, medical and engineering purposes [2]. PMMA is, on the other hand, a tough and lightweight polymer with a density between 1.17 and 1.20 g/cm 3 [3]. PMMA has a promising impact strength, comparing with polystyrene and glass [3]. The white colored PVP is considered as stable materials in different temperature range applications, hygroscopic, completely soluble in water and capable of incorporation with various materials [4]. ZrO 2 NPs, in another point of view, have a quite interesting loading [6]. Furthermore, the OM images refer to good diffusion of NPs, homogeneity and surface roughness of raw material/ZrO 2 NPs composites. Figure 2. represents the FTIR spectrum of k1 specimen in the wave number range between 500 and 4500 cm − 1 . From the figure, it can obviously be seen that, the chemical functional groups that respectively appeared in the computed optical range. These functional groups were alcohol/ phenol (OH) stretching which appeared at 3284.56 cm − 1 , and (C = C) stretching at 1662.29 cm − 1 . The bands at 1437.15 cm-1, 1289.84 cm − 1 , and 1099.92 cm − 1 are corresponded to the symmetric bending of CH2, the CH wagging, and (C-O) stretching of primery alcohol respectively [6,7]. The (OH) wagging which appeared at 540 cm − 1 is accountable to the existence of ZrO 2 NPs. There is many physical interactions happened between the polymer blend

Synthesis of NCs
The PEO, PMMA and PVP polymer powders were separately dissolved in 50 mL deionized water (DI) and stirred at 60 o C via magnetic stirrer. The process continued for 1 h. before getting on homogeneous mixture. In the doping process, four different ZrO 2 NPs ratios were separately added to the polymer blend. The process then continued for another 3 h. The composite mixtures were then casted in 5 cm Petri dish. Thereafter, samples have been left to dry for 7 days. The specimens thickness were in the range between 80 and 95 μm. The method of preparation was listed in Table 1.

characterizations
The morphological properties were investigated using Nikon,Olympus 73,346 camera. Vertex 701, Bruker spectrometer has been utilized to study the chemical functional groups of k1 specimen. The density was measured using Matsu Maku GP/120S. The viscosity was measured using Brookfield viscometer. The USW properties were measured by using SV-DH-7 A/SVX-7 ultra sound instrument. The some weak agglomerations of ZrO 2 NPs were clearly appeared in (C and D) parts. The explanation of that related to the interaction that happens among ZrO 2 NPs because these NPs occupies a high surface area in small volume [6]. OM is generally used to study the compatibility or surface morphological properties among various constituents of the polymer electrolytes. The micrograph indicates with the loaded of ZrO 2 NPs, the surface clearly shows a uniformly distributed area. The micro/macro structural indications were good agreement with previous results that have referred an improvement in the amorphous phase after  Fig. 2 The FTIR spectrum of k1 specimen The USW velocity has been directly proportional with the amount of ZrO 2 NPs, but inversely proportional with frequency. This is because the USW causes various physical interaction between PEO/ PMMA/PVP polymer blend and ZrO 2 NPs molecules, lead to increase the velocity. The increasing of frequency led to decrease the USW velocities [12]. Figure 5. shows that, the relationship between the relaxation time and amplitude and frequency. The relaxation amplitude (D) was theoretically calculated by [13]:

The OM and FTIR images:
The values of relaxation time and amplitude decreased with the increasing of frequency and ZrO 2 NPs contents. The increasing of these coefficients with ZrO 2 NPs led to higher fraction between the composition layers that examined by moment of inertia [14]. The compressibility of PEO/PMMA/PVP doped with ZrO 2 NPs were theoretically calculated by Laplacian equation [15], so the values raised with higher frequency: The Young modulus (K) was calculated by [16]: and ZrO 2 NPs contents. The bond which appeared in the optical range between 600 and 800 cm − 1 corresponds to ZrO 2 NPs [8].

The USW measurements
The solution density of PEO/PMMA/PVP polymer blend against various ZrO 2 NPs contents was measured at room temperature and shown in Fig. 3. Figure 3. represents the densities of all aqueous solutions increased with the increasing of the ZrO 2 NPs contents, because the ZrO 2 NPs formed across linked (networks) among the molecules of PEO/ PMMA/PVP that occupies the spaces among molecules. Furthermore, the density of each materials increased with increasing of doping materials [9]. The USW properties were applied for testing in the region between the sender and receiver. The receiver converts USW pulses to the electrical pulses then received by oscilloscope. The apparent signal in first channel contains positive peak which represents the incident USW or initial amplitude (Ao) and the negative part in the second channel refers to receiver amplitude (A). The USW transmittance waves (T) have been computed by the following equation [10]: The density is very smaller than velocity. The USW absorption coefficient was calculated by the law of Lambert-Beer [19]: Moreover, the increasing of the dielectric constant perhaps because the increasing of ZrO 2 NPs contents [24]. This is due to of just each atom of oxygen has the same distance with the zirconia atoms. The variance in the atoms position due to mechanical stress leads to creation of an electric field and polarization respectively [25,26]. The researchers have been studied various mechanical USW properties of materials in order to enhanced the ability to absorb USW [27][28][29][30][31][32][33].

Conclusions
Novel (PEO/PMMA/PVP)-ZrO 2 NPs NCs films were successfully prepared via casting method. The OM images showed a fine diffusion of ZrO 2 NPs in the mixtures. The FTIR peaks refers strong interfacial interactions between the raw material and ZrO 2 NPs. The results revealed an enhancement of the physical properties by the increasing the ratio of ZrO2NPs contents. The enhancing of density, viscosity, USW velocity and USW absorption coefficient of the polymer blend was associated with increasing of ZrO 2 NPs. The addition of ZrO 2 NPs controlled an increase the K = ρv 2 (5) Figure 6. shows that the relationship between the USW compressibility, bulk modulus and the frequency. The USW compressibility values of PEO/PMMA/PVP increased with the increasing of frequency, this is because the propagation of USW made a random polymer chain conformation, in addition of the USW make a compression lead to reduce the elasticity of composition [17]. Furthermore, the velocity of USW is inversely proportional with compressibility. Figure 6. also represents, the bulk modulus values were lower when the frequency elevated. The specific acoustic impedance (SAI) and USW absorption coefficients behaviors were offered in Fig. 7. Figure 8. Shows that the values of SAI and USW absorption coefficient decreased with the increasing of frequency [18][19][20][21][22][23]. The SAI was calculated by [18]: SAI = ρv (6) Fig. 7 The variation of SAI and US absorption coefficient with frequency Fig. 6 The variation of compressibility and bulk modulus with frequency