Physical Society of Indonesia Articles Journal of the Physical Society of Indonesia 1.
, 116-122 .
https://doi.
org/10.
35895/jpsi.
Synthesis and Characterization of ZnO@SiOCC Composite for Microwave Absorber Applications Muhammad Fauzan1.
Aditia Nur Bakti2**.
Elvina Trivida2.
Nova Nur Elisa Dewi1.
Djoko Triyono3.
Iwan Sugihartono1* 1Physics Study Program.
FMIPA.
Universitas Negeri Jakarta.
Jl.
Rawamangun Muka.
Jakarta, 13220.
Indonesia 2Research Center for Testing Technology and Standards.
National Research and Innovation Agency.
Banten, 15314.
Indonesia 3Physics Department.
FMIPA.
Universitas Indonesia.
Kampus UI Depok.
Depok, 16424.
Indonesia (September 05, 2025.
revised October 10, 2025.
accepted 11, 2025.
published online October 13, 2.
This study aims to synthesize ZnO@SiOCC composites via biosynthesis using Moringa oleifera leaf extract and to investigate the effect of different SiOCC contents .
ure ZnO, 1%, 3%, and 5% by weigh.
on their structural and microwave absorption properties, with ZnO prepared from a Zn(NOCE)CCA4HCCO precursor and calcined at 450 AC for 2 hours.
The synthesized samples were characterized using X-ray Diffraction (XRD) and a Vector Network Analyzer (VNA).
XRD results confirmed that all samples exhibited a hexagonal wurtzite crystal structure with space group P6CEmc and showed no secondary The crystallite size decreased with increasing SiOCC content, indicating nanoparticle formation and reduced crystallinity.
VNA measurements showed that the ZnO@SiOCC sample with 3% SiOCC exhibited the best microwave absorption performance, with a minimum reflection loss (RL) value of Ae 0251 dB at a frequency of 6.
125 GHz.
These results suggest that the 3% composition achieved better impedance matching and enhanced absorption efficiency.
Keywords: ZnO@SiO2, biosynthesis, moringa oleifera, microwave absorption This is an open access article under the CC BY-NC license.
Copyright A 2025 by Author.
Published by Physical Society of Indonesia
INTRODUCTION
The rapid development of advanced technology, particularly in defense and communication systems, has increased the demand for materials capable of mitigating electromagnetic interference (EMI) and reducing radar detection (Mathur et al.
, 2.
Radar Absorbing Materials (RAM.
play a crucial role in stealth technology by converting incident electromagnetic waves into thermal energy through dielectric and/or magnetic loss mechanisms, thereby minimizing reflected signals (Taryana et , 2.
Among potential RAM candidates, zinc oxide (ZnO) has attracted significant interest due to its wide bandgap .
4 eV), high dielectric activity, non-toxicity, and environmental friendliness (Du et , 2.
However, pure ZnO often suffers from particle agglomeration and limited structural stability, which can reduce its absorption efficiency.
To address these limitations, silica (SiOCC) is introduced as a coating material to form a coreAeshell ZnO@SiOCC structure.
SiOCC, being an amorphous dielectric, can improve impedance matching, enhance particle dispersion, and induce interfacial polarization, thereby boosting microwave absorption performance (Yang et al.
, 2.
Conventional synthesis methods for ZnO@SiOCC often involve hazardous chemicals and high energy consumption, raising environmental In contrast, green synthesis approaches utilizing plant extracts have emerged as sustainable alternatives, offering eco-friendly, low-cost, and biocompatible processes (Ahmed et al.
, 2.
Moringa oleifera leaves are particularly promising as a reducing and stabilizing agent due to their high content of bioactive compounds such as flavonoids, phenolics, and terpenoids, which can facilitate the reduction of metal ions and prevent nanoparticle aggregation (Sugihartono et al.
, 2024.
Guda et al.
, 2.
Contact Author: *Iwan-Sugihartono@unj.
** adit006@brin.
ISSN: 2685- 3841 (Onlin.
2025 The Physical Society of Indonesia J.
Phys.
Soc.
Ind.
, 116-122 .
Articles Fauzan et al.
Previous studies have demonstrated that plant-mediated biosynthesis can produce nanoparticles with desirable structural and functional properties for various applications, including photocatalysis, sensing, and electromagnetic wave absorption (Asmathunisha & Kathiresan, 2012.
Iravani, 2.
This study aims to synthesize ZnO@SiOCC composites via biosynthesis using Moringa oleifera leaf extract and to investigate the effect of different SiOCC contents .
ure ZnO, 1%, 3%, and 5% by weigh.
on their structural, and microwave absorption properties.
The synthesized materials were characterized using Xray Diffraction (XRD) to determine crystal structure and crystallite size, and Vector Network Analyzer (VNA) for evaluating microwave absorption performance.
The findings are expected to contribute to the development of environmentally friendly and cost-effective RAMs with optimized structural and electromagnetic properties for defense and EMI shielding applications.
METHOD
Moringa oleifera leaves were washed with distilled water, dried at room temperature for 7 days, ground into powder, and sieved.
A total of 25 g of the powder was boiled in 250 mL of distilled water at 80 AC for 30 minutes, then filtered to obtain the extract.
A zinc nitrate hexahydrate [Zn(NOCE)CCA4HCCO] solution with a concentration of 0.
8 M was prepared and heated to 80 AC while being stirred.
Moringa oleifera extract was added dropwise, and the pH was adjusted to 10 using NaOH.
The mixture was stirred for 30 minutes to form a Zn(OH)CC precipitate.
The precipitate was washed with distilled water and ethanol, dried at 80 AC for 12 hours, and calcined at 450 AC for 2 hours to produce ZnO powder.
The ZnO@SiOCC composite was prepared by mixing 2 g of ZnO powder with SiOCC powder at variations of .
ure ZnO, 1%, 3%, and 5% by weigh.
in a mixture of 160 mL ethanol and 40 mL distilled water.
The mixture was stirred for 30 minutes, and the pH was adjusted to 9Ae10 using NaOH.
Stirring was continued for 4 hours at room temperature.
The resulting precipitate was washed with distilled water and ethanol, dried at 80 AC for 12 hours, and ground into fine powder.
X-ray Diffraction (XRD) was used to determine the crystal structure, and a Vector Network Analyzer (VNA) with the coaxial-line method in the frequency range of 4.
3Ae8.
5 GHz was used to measure microwave absorption properties.
Figure 1.
X-Ray Diffraction (XRD) pattern of ZnO@SiOCC nanoparticle synthesis results with variations in SiOCC concentration of .
ure ZnO, 1%, 3%, and 5% by weigh.
RESULTS AND DISCUSSION
1 Results 1 XRD Figure 1 shows the X-ray diffraction (XRD) pattern of ZnO@SiOCC material with variations in SiOCC concentration of .
ure ZnO, 1%, 3%, and 5% by weigh.
The diffraction pattern displays the highest intensity peaks on the .
, .
, and .
planes, which are characteristic of the wurtziteISSN: 2685- 3841 (Onlin.
2025 The Physical Society of Indonesia J.
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, 116-122 .
Articles Fauzan et al.
type hexagonal crystal structure of ZnO.
The XRD pattern does not show any additional peaks indicating a second phase or other impurity compounds.
This indicates that the addition of SiOCC does not change the main structure of ZnO and does not form new compounds.
This finding is in line with the results of research by Godavarti et al.
, which stated that phase purity can be identified from the absence of foreign peaks in the diffraction pattern.
Figure 2.
Diffraction angle shift of ZnO & ZnO@SiOCC nanoparticles with variations in SiOCC concentration of .
%, 3%, and 5%).
Based on Figure 2, the diffraction peaks for the .
, .
, and .
planes of ZnO and the ZnO@SiOCC composite .
%, 3%, and 5%) appear at similar 2 angles, indicating that the addition of SiOCC does not significantly change the d-spacing of the crystal planes.
This indicates that the ZnO crystal structure remains stable after modification with SiOCC.
XRD analysis was performed using HighScore Plus software, with reference data from JCPDS No.
01-079-0207, which refers to the hexagonal wurtzite ZnO structure.
All samples exhibit diffraction patterns consistent with a hexagonal polycrystalline crystal structure, with the space group P6CEmc.
Table 1.
Structural parameters of ZnO@SiOCC nanoparticles with (SiOCC: pure ZnO, 1%, 3%, and 5% by weigh.
Structural Parameters Sampel
2 (A)
Crystallite d-spacing .
I) FWHM (A) Micro Strain Size .
(%) hkl .
ZnO ZnO@SiO2 (SiO2: 1%) ZnO@SiO2 (SiO2: 3%) 31.
ZnO@SiO2 (SiO2: 5%) 31.
ZnO ZnO@SiO2 (SiO2: 1%) 34.
ZnO@SiO2 (SiO2: 3%) ZnO@SiO2 (SiO2: 5%) 34.
ZnO ZnO@SiO2 (SiO2: 1%) 36.
ZnO@SiO2 (SiO2: 3%) 36.
ZnO@SiO2 (SiO2: 5%) 36.
The decrease in crystallite size with increasing SiOCC addition indicates that SiOCC particles are able to inhibit the growth of ZnO grains, resulting in smaller and more finely distributed particles.
ISSN: 2685- 3841 (Onlin.
2025 The Physical Society of Indonesia J.
Phys.
Soc.
Ind.
, 116-122 .
Articles Fauzan et al.
Table 2.
Lattice parameters of ZnO@SiOCC nanoparticles (SiOCC: pure ZnO, 1%, 3%, and 5% by weigh.
Sampel ZnO Lattice Parameters ZnO@SiO2 ZnO@SiO2 ZnO@SiO2 (SiO2: 1%) (SiO2: 3%) (SiO2: 5%) a = b .
I) c .
I) = (A) (A) Volume .
IA) VNA Based on VNA measurements (Figure .
, the maximum and minimum RL values were obtained for the four samples, namely ZnO and ZnO@SiOCC (SiOCC: 1%, 3%, and 5%), as shown in Table 3.
The table shows that all samples exhibit microwave absorption capabilities, although the best absorption performance was obtained with the ZnO@SiOCC .
%) composition.
The ZnO@SiOCC sample showed the largest minimum RL value, at -2.
0251 dB at a frequency of 6.
125 GHz, indicating the highest microwave absorption capacity.
This indicates that the addition of 3% SiOCC is the optimum composition in the ZnO@SiOCC system for microwave absorption at that frequency.
Conversely, a decrease in absorption performance occurred with the addition of 5% SiOCC, which could be caused by particle agglomeration or an imbalance in the material's microstructure.
Figure 3.
The relationship curve between the RL value and the frequency range of 4.
3Ghz - 8.
5Ghz for each sample, namely pure ZnO, and ZnO with the addition of SiOCC of 1%, 3%, and 5%.
Table 3 Lattice parameters of ZnO & ZnO@SiOCC nanoparticles .
%, 3% and 5%).
RL min .
B) RL max .
B) Frequency (GH.
ZnO ZnO@SiO2 (SiO2: 1%) ZnO@SiO2 (SiO2: 3%) ZnO@SiO2 (SiO2: 5%) Figure 4 shows a comparison graph of the absorption levels of ZnO@SiOCC (SiOCC: SiOCC: pure ZnO, 1%, 3%, and 5% by weigh.
and SiOCC/CNT (SiOCC: 0.
5%, 1%, 2%).
ZIF, 1% Ni/ZIF-67.
To evaluate the microwave absorption performance of the ZnO@SiOCC nanocomposite, a comparison was made with several comparative materials that had previously been studied at BRIN in 2024, namely SiOCC/CNT materials .
ith variations of 0.
5%, 1%, and 2%).
ZIF, and 1% Ni/ZIF-67.
The VNA results show that the ZnO@SiOCC sample with a composition of 3% has the best microwave absorption performance, with a RL value of 2.
0251 dB at a frequency of 6.
125 GHz, demonstrating the best performance, among variations of ZnO & ZnO@SiOCC (SiOCC: 1%, 5%), and other comparison materials such as SiOCC/CNT (SiOCC: pure ZnO, 1%, 3%, and 5% by weigh.
ZIF, 1% Ni/ZIF67.
This study shows that the best microwave absorption (RL) performance is in ZnO@SiOCC with 3% ISSN: 2685- 3841 (Onlin.
2025 The Physical Society of Indonesia J.
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, 116-122 .
Articles Fauzan et al.
SiOCC.
This indicates that the combination of this composite with a ZnO@SiOCC core-shell structure is able to well combine the absorption strength of ZnO with the stability and smoothness of the morphology of SiOCC.
This composite produces a good combination.
Figure 4.
VNA Graph (S11 Paramete.
Table 4.
Maximum and minimum RL values for ZnO & ZnO@SiOCC (SiOCC: pure ZnO, 1%, 3%, and 5% by weigh.
S11 Parameter.
Frequency ZnO ZnO@SiO2 ZnO@SiO2 ZnO@SiO2 (GH.
(SiO2: 1%) (SiO2: 3%) (SiO2: 5%) |RL mi.
B) Table 5.
Maximum and minimum RL values for SiOCC/CNT.
Frequency (GH.
SiO2/CNT (CNT: 2%) |RL mi.
B) Discussion Based on the research data, the addition of varying SiOCC concentrations in the ZnO@SiOCC composite significantly influences the crystal structure, and microwave absorption capability of the resulting material.
XRD characterization results indicate that all samplesAiboth pure ZnO and ISSN: 2685- 3841 (Onlin.
2025 The Physical Society of Indonesia J.
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Soc.
Ind.
, 116-122 .
Articles Fauzan et al.
ZnO@SiOCC with 1%, 3%, and 5% SiOCCAiexhibit diffraction patterns characteristic of the hexagonal wurtzite crystal structure with a P6CEmc space group, without the presence of secondary phases.
This confirms that the biosynthesis method using Moringa oleifera leaf extract did not alter the primary ZnO phase (Du et al.
, 2.
Crystallite size calculations using the Scherrer equation revealed a decreasing trend with increasing SiOCC concentration.
This reduction in crystallite size indicates finer particles, which can enhance the materialAos active surface area (Yang et al.
, 2.
This phenomenon is consistent with the role of SiOCC as a shell in the coreAeshell structure, preventing excessive ZnO agglomeration and resulting in better particle dispersion.
VNA measurements demonstrated that the sample with 3% SiOCC achieved the best minimum Reflection Loss (RL) value of -2.
0251 dB at a frequency of 6.
125 GHz.
This result indicates improved impedance matching and more effective interaction between the microwaves and the material surface.
The presence of the SiOCC layer is presumed to induce interfacial polarization, which enhances the dielectric loss mechanism and thereby strengthens microwave absorption.
Thus, the XRD.
SEM, and VNA data collectively support that varying SiOCC concentrations affect both the structural and electromagnetic properties of ZnO@SiOCC composites, with the 3% SiOCC composition proving to be the optimum formulation in this study.
CONCLUSION
ZnO@SiOCC composites synthesized via a biosynthesis method using Moringa oleifera leaf extract successfully retained the hexagonal wurtzite ZnO crystal structure without forming secondary phases, while the addition of SiOCC reduced crystallite size, indicating the formation of nanoscale particles and preventing excessive agglomeration.
Among the variations tested, the 3% SiOCC sample exhibited the best microwave absorption performance with a minimum RL value of -2.
0251 dB at 6.
125 GHz, demonstrating improved impedance matching and higher absorption efficiency.
These results indicate that a 3% SiOCC composition optimally enhances both the structural and electromagnetic properties of ZnO@SiOCC, making it a promising, environmentally friendly, and cost-effective candidate for microwave absorber applications.
ACKNOWLEDGEMENT
This research was supported by the facilities, scientific, and technical support National Research and Innovation Agency through E- Layanan Sains (ELSA) BRIN.
REFERENCE