Type of contribution:
Editorial Research Paper Case Study Review Paper Scientific Data Report of Tech.
Application Mechanical Engineering for Society and Industry Vol.
No.
pp 257-267 https://doi.
org/10.
31603/mesi.
Exploring the potential of indonesian iron sand in the formation of iron nitride for magnetic applications Indra Sidharta1.
Rakhasoni Firman Syah2.
Sutikno1.
Darminto2.
Abdullah Shahab1* 1 Department of Mechanical Engineering.
Institut Teknologi Sepuluh Nopember.
Surabaya 60111.
Indonesia 2 Department of Physics.
Institut Teknologi Sepuluh Nopember.
Surabaya 60111.
Indonesia shahab_nqa@yahoo.
Highlights:
A Iron nitride materials were developed from Indonesian natural iron sands using subsequent coprecipitation and gas nitriding processes.
A Fe3O4 and Fe2O3 nanopowder synthesized from natural iron sands can be used as a precursor material for iron nitride.
A Gas nitriding of Fe3O4 powder results in the formation of both the Fe4N and Fe3N phases, achieving a maximum magnetic saturation of 75.
41 emu/g.
Abstract Article info Submitted:
2025-02-27
Revised:
2025-06-06
Accepted:
2025-06-22
Iron nitride is a transition metal material that exhibits ferromagnetic properties at room temperature, making it a suitable candidate for use in Soft Magnetic Composites (SMC) Previous research showed that iron nitride can be synthesized using nano-sized iron oxide powder derived from processed natural iron sand through gas nitriding.
Considering the abundance of iron sand in Indonesia, there is a need to carry out an investigation related to iron sand-based SMC.
Therefore, this research aims to synthesize iron nitride material using the abundant natural iron sand discovered in Indonesia.
This study used iron oxide material synthesized from locally obtained natural iron sand, in the form of Fe3O4 and Fe2O3.
Iron oxide undergoes coprecipitation and was subsequently exposed to the gas nitriding process with a holding time of 4 hours and a gas flow of 150 mL/min in NH3 gas.
The results show that iron nitride is formed after nitriding of iron oxide powders, and the phases formed include A-Fe3N and Ao-Fe4N.
The synthesized material exhibits soft magnetic properties, with saturation magnetization values ranging from the highest at 75.
41 emu/g and the lowest at 18.
9 emu/g.
Keywords: Natural iron sand.
Iron nitride.
Iron oxide.
Nitriding.
Soft magnet Introduction This work is licensed under a Creative Commons Attribution-NonCommercial 4.
International License Publisher Universitas Muhammadiyah Magelang IndonesiaAos transition to electric vehicles (EV.
is fostering a thriving ecosystem that offers promising opportunities for all stakeholders.
The development of the EVs industry has driven extensive research aimed at achieving technological breakthroughs and ensuring self-reliance in innovation .
, .
, .
One key area of research is electric motors, specifically axial flux motors.
This type of motor holds promising technological and business impact on EVs.
The impact of axial flux motor technology on the EVs industry is exemplified by the acquisition of YASA, a spin-off company from Oxford University, by the Mercedes-Benz Group in 2021 .
, .
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Research on axial flux motors has also been carried out in Indonesia .
, .
, .
However, most of the components were imported from the international market.
One of the key components that determine the performance of an axial flux motor is the stator core.
This core is typically made from electrical or silicon steel.
Additionally, soft magnetic materials such as iron-cobalt or ironnickel alloys are frequently used to enhance the efficiency of EVs.
SMC materials are the latest technology for EVs core application that offers the highest efficiency of the axial flux motor.
It can increase motor efficiency to approximately 99% due to its unique characteristics, i.
the isotropic magnetic behavior, high electrical resistivity, high magnetic permeability, low eddy current loss, low total core loss at low to high frequency, and low magnetic coercivity .
, .
, .
SMC is a composite material consisting of ferromagnetic powder particles where each powder particle is isolated by a layer or film consisting of a mixture of other materials .
, .
, .
SMC was developed using iron powder as the base material, and efforts have been made to improve the performance of iron-based SMC .
, .
Some iron-based SMC were produced commercially, but most are not readily available in Indonesia.
In line with these results.
Indonesia has great potential in developing iron powder-based SMC because the natural resources of iron minerals are quite large.
However, obtaining iron powder with high purity requires a complex production process and high costs.
Therefore, there is a need for research on alternative materials to iron powder.
When compared with iron powder which is often used as SMC, iron nitride material has a comparable magnetic property .
, .
Iron nitride is a transition metal material that has a metastable phase.
This is because iron nitride has several phases when it is in the form of bulk, thin film, and powder .
The formation of the iron nitride phase is affected by the concentration of nitrogen used.
Magnetic properties of iron nitride are excellent for SMC applications, and some iron nitride phases have soft magnetism such as Fe3N.
Fe4N, and Fe8N .
, .
, .
Iron nitride can be manufactured using various raw materials and methods.
Its production is primarily based on conventional nitriding techniques, which are commonly used in alloy steel processing .
Therefore, ball milling, gas nitriding, and plasma nitriding are widely applied for the synthesis of iron nitride .
, .
, .
Ion nitride with Fe3N phase can be synthesized using Fe3O4 powder as the starting material .
From previous research, it was also found that Fe2O3 and Fe3O4 powder can be derived from natural iron sand using the coprecipitation method .
, .
, .
, .
, .
Recently, many efforts have been done for incorporating natural resources in Indonesia, namely iron sands, for magnetic application .
, .
, .
, .
Research on natural iron sand-based iron nitride could be highly significant, particularly given Indonesia's abundant iron sand resources.
Iron nitride, particularly if derived from locally available iron sand, could offer several advantages in terms of local resource utilization, economic development, environmental sustainability, and technological innovation.
The objective of this research is to synthesize iron nitride material using the abundant natural iron sand found in Indonesia.
These results constitute a significant stride towards the development of locally sourced SMC material, with prospective applications in EVs.
Methods This research synthesized iron nitride material from iron oxide i.
Fe3O4 and Fe2O3.
Iron oxide Fe3O4 was extracted from natural iron sand obtained in a domestic market in Surabaya.
East Java.
Indonesia.
The synthesis method followed the approach reported in the reference .
Magnetic separation is a crucial step in obtaining iron sand with a high Fe3O4 content.
This enriched material can then be processed further using the coprecipitation method.
The coprecipitation method for obtaining magnetite has been used widely .
, .
, .
, to obtain nano-scale powder.
The coprecipitation process started by dissolving iron sand in hydrochloric acid (HC.
under a stirring process at 1000 RPM.
Subsequently, ammonium hydroxide (NH4OH) was added dropwise to the resulting solution to obtain the precipitates.
The final stage of the process involved washing and drying the precipitates, resulting in the production of Fe3O4 powder.
Previous research shows that Fe2O3 can be transformed into iron nitride .
, .
Therefore.
Fe2O3 was also used for iron nitride synthesis.
Fe2O3 powder was produced by heating iron oxide powder Fe3O4 phase at a temperature of 600 AC .
, .
Gas nitriding was carried out in a tube furnace at different temperatures.
Ammonia (NH.
gas was used during the heating at a flow rate of 150 mL/min.
Fe 2O3 samples were nitrided at temperatures of 600 AC, 625 AC, and 650 AC respectively with a holding time of 4 hours.
Gas nitriding Mechanical Engineering for Society and Industry.
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of the Fe3O4 sample was carried out at a temperature of 625 AC for 4 hours.
The four samples were then expressed by FN1.
FN2.
FN3, and FN4, respectively.
To analyze the content of the powder obtained.
XRD analysis was conducted using Cu-K ( = 1.
radiation with a PANalytical Xpert Pro Diffractometer.
Natural iron sand was also examined by X-ray Fluorescence (XRF) analysis, using PANalytical MiniPal4.
The magnetic properties of the samples were analyzed using Vibrating Sample Magnetometer (VSM) from Dexing Magnet Ltd.
VSM250.
The surface morphology of nitrided samples was examined using Scanning Electron Microscope (SEM) characterization, equipped with Energy Dispersive Spectroscopy (EDS) using Hitachi FlexSEM 1000.
Results and Discussion Characterization of Natural Iron Sand Natural iron sand was used as the raw material for synthesis of iron nitride materials.
The synthesis involves coprecipitation and gas nitriding process.
The iron sand was purchased from domestic market in Surabaya.
The iron sand subsequently underwent some examination prior to coprecipitation process, namely XRD.
XRF and SEM.
The examinations was carried out to obtain better information regarding the iron sand characteristics.
Figure 1 shows the result of the XRD measurement of the starting material, natural iron sand before magnetic separation.
The analysis shows that iron sand contains the Fe3O4 phase and there are contaminants in the Ti2O3 phase.
The Fe3O4 and Ti2O3 phases was compared with CIF-9009769 and CIF-1532065, respectively.
Both phases are common constituents of natural iron sand found in Indonesia, along with Fe2O3.
SiO2.
Al2O3, and TiO2 .
, .
, .
However.
Fe2O3.
SiO2.
Al2O3, and TiO2 were not detected in the XRD measurement.
Futher examination in the natural iron sand was carried out using XRF technique to obtain the elemental composition of the iron sand.
Table 1 shows the result of XRF analysis, indicating elemental composition of the iron sand.
The XRF result complements the XRD The main element of the iron sand is iron oxide and titanium oxide, as indicated by the presence of Fe and Ti in the XRF result.
Some other elements, such as Al.
Si.
Ca.
Cr.
Mn.
Cu.
Zn.
Rb.
Zr and Bi, are also detected in a small The presence of Fe.
Ti.
Al.
Si in the XRF result indicates the typical Figure 1.
iron sands obtain from Java.
XRD pattern of as suggested by works of natural iron sand as starting material .
Table 1.
Elemental composition of the natural iron sand obtained from XRF analysis, in wt% The SEM examination was carried out to investigate the morphology of the iron sand used in the experiment.
Figure 2 shows the microstructure of iron sand, observed using SEM.
The morphology of iron sand particles is rounded shape with a smooth surface.
The particle size varies between 100 Ae 400 AAm.
Natural iron sand in Indonesia has various morphology .
, .
, .
, which includes irregular, rounded, and bitetrahedral shapes, and the surface can be rough or Characterization of Fe2O3 and Fe3O4 Powders The characterization shows that the magnetic separation process needs to be improved to eliminate contaminants.
The results of the XRD analysis of powder following the process of Mechanical Engineering for Society and Industry.
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coprecipitation and heating of Fe3O4 powder are shown in Figure 3.
The resulting XRD pattern is matched against the CIF data, and quantitative analysis is then performed using MAUD After coprecipitation process, the obtained substance takes the form of Fe3O4 powder, suitability as CIF-9009769.
After the heating process.
Figure 2.
the Fe3O4 powder yields a SEM image of the Fe2O3, natural iron sands to CIF2101168.
Contaminants in iron sand in the form of Ti2O3 phase are not visible in the XRD pattern of Fe3O4 The XRD measurement results also show that Fe2O3 powder from the oxidation process of Fe3O4 powder at a temperature of 600 AC can Fe3O4 .
phase into a Figure 3.
Fe2O3 XRD pattern of:
The result is .
Fe2O3 powder.
Fe3O4 powder research of .
, .
, .
The results of refinement analysis using MAUD software are shown in Table 2.
It can be seen that the Sigma (Si.
value, reflecting the Goodness of Fitting (GoF), and Rw is in line with the MAUD The quantitative analysis derived from MAUD shows information about Fe2O3 and Fe3O4 powder.
The analysis indicates the Fe3O4 sample forms a cubic spinel system Fd-3M space group as the phase structure.
The Fe3O4 has a lattice parameter of 8.
3376 yI and a crystal size 7 nm.
The experimental result is comparable to the lattice parameter of Fe3O4 reported by reference work used .
in this coprecipitation process.
The crystal size of the Fe3O4 in this experiment is lower than the reference work.
It is likely due to the difference of pH during coprecipitation process.
The size of the crystal is influenced by pH of the process.
Higher pH tends to produce smaller crystal size, as reported by Sunaryono et al.
and Kristina et al.
Fe2O3 nano powders can be sythesized using various methods, as reported by Novita et al.
In this experiment, the Fe2O3 was produced by heating Fe3O4 nano powders, obtained in the coprecipitation process, in a muffle furnace at 600 AC.
The XRD result indicates that the Fe2O3 has a rhombohedral crystal system with space group of R-3c.
The lattice parameter of Fe2O3 measures a = 5.
03103 yI and c = 13.
7014 yI, with a crystal size of 55.
9 nm.
The lattice parameter result is similar to that reported by other works .
, .
The experiment produced Fe2O3 powder that has larger crystal size in comparison to the Fe2O3 synthesized by coprecipitation method .
, .
, .
Larger crystal size obtained in this experiment is obviously caused by the use of heating method in the synthesize of Fe2O3 powder.
Tulebayeva et al.
reported that higher annealing temperatures result in larger average nanoparticle sizes .
In the study, the starting material of Fe3O4 .
, with a crystal size of 12.
4 nm, was transformed into Fe2O3 .
, with a crystal size of 34.
6 nm, after the annealing process at 600 AC .
The result shows an increase in crystal size during the heating of the Fe3O4 powder.
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Table 2.
Data Space Powder Refinement results of the Reference Group Fe2O3 and Fe3O4 powder Fe2O3 CIF Ae R -3 c using MAUD analysis Fe3O4 CIF F d -3 m Lattice Parameter .
I) %Wt Crystal Size
(%) Rexp Rwp
Sig
(%)
(%)
Based on the XRD analysis, both iron oxide powders can be regarded as nano-sized powders.
In general, nano-sized particles have a beneficial effect on the reaction kinetics .
, .
, .
Nano-sized particles exhibit significantly higher surface area-to-volume ratios compared to larger Therefore, a faster reaction rate, enhanced diffusion, and improved reactivity are expected .
, .
Synthesis of Iron Nitride The result of the XRD measurement of the powders after the gas nitriding process is shown in Figure 4.
The XRD results show that iron nitride can be synthesized using the gas nitriding method.
Additionally, successful synthesis of iron nitride has been achieved, forming Fe 3N and Fe4N.
However, there are still contaminants from the sample in the form of Fe 2O3 and Fe3O4.
Since the formation of the two phases is also due to a non-optimal process of nitriding ammonia on the powder, contaminants are present in the powder after treatment.
Quantitative analysis was carried out using MAUD software to determine the phase composition formed in the sample.
The comparison of phase compositions in the samples is shown in Table 3.
In the results of the nitriding process.
FN2 exhibits relatively fewer contaminants compared to other temperature variations.
FN3 on the other hand, shows suboptimal results due to the predominance of contaminants over the formed iron nitride phase.
The optimal temperature for forming the Fe3N phase is found to be 625 AC.
Consequently.
FN4 yields phases of Fe4N and Fe3N.
This result is in line with prior research .
, which suggests that the Fe4N phase can arise from the Fe3N phase transformation.
Iron nitride is conventionally formed as a result of the interaction of ammonia (NH.
with the solid iron precursor at temperatures Ou 400 AC.
Both iron precursor and the resulting nitride phases act as catalysts, facilitating the dissociation of NH3 into atomic nitrogen and subsequently into molecular nitrogen and Nitridation occurs as atomic nitrogen diffuses into the metal, converting it into iron The extent of nitridation is influenced by reaction temperature and the flow rate of NH3 gas.
Recent work by JoviseviNKlug et al.
shows the transformation of iron oxide to iron nitride.
The formation of iron nitride is likely to occur through a stepwise reduction of iron Figure 4.
XRD patterns of oxide rather than a direct FN1.
FN2.
FN3 and FN4 transformation from oxide to nitride.
Table 3.
Comparison of the number
of phases formed in each variation using MAUD
Sample Variation FN1
FN2
FN3
FN4
Fe2O3 nitriding temperature 600 AC Fe2O3 nitriding temperature 625 AC Fe2O3 nitriding temperature 650 AC Fe3O4 nitriding temperature 625 AC Fe2O3 Composition Fe3O4 Fe3N Fe4N SEM examination equipped with EDS analysis was carried out on samples of FN2 and FN4 as shown in Figure 5.
From the SEM morphology results, it was shown that the particles in the two Mechanical Engineering for Society and Industry.
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powders had irregular shapes, which are formed due to the formation of the iron nitride phase.
Figure 6 shows that the morphology has an irregular lamellar texture.
The irregular shape of iron nitride was reported in the previous investigation .
Similar morphology of iron nitride is reported in the works of Zhang et al.
Gang et al.
and Liu et al.
The reference works reported that the iron nitride has irregular spherical or ellipsoidal shape as its final form.
The irregular lamellar texture of iron nitride in the FN4 sample is more profound than the one in the FN2 sample.
Another structure that can be seen in the SEM result is iron oxide.
The initial fine shape of iron oxide powder becomes coarse and changes the nitriding process .
, .
, .
EDS analysis on both samples shows that the structure is iron nitride, as shown in Figure 6.
Although EDS analysis detected trace amounts of Ti.
Al, and Cu, these elements were not observed in the XRD patterns.
This discrepancy is attributed to the higher surface sensitivity of EDS, which can detect elemental residues or minor surface contaminants not present in significant crystalline Since XRD only detects well-crystallized phases above a certain concentration threshold .
Ae5 wt%), the absence of the trace elements peaks suggests that these elements are either amorphous or below detection limits.
Figure 5.
SEM image of iron nitride The arrow shows the location of the EDS spot analysis:
FN2 sample.
FN4 sample Figure 6.
EDS results of the iron nitride samples.
Location of EDS spot analysis is indicated in Figure 5:
FN2 sample.
FN4 sample The magnetic properties of iron nitride powder can be seen from the results of the VSM analysis in the form of a hysteresis loop.
The hysteresis loop of the samples is shown in Figure 7.
Magnetic saturation value of FN4 was 75.
41 emu/g.
The saturation magnetic values of FN1.
FN2, and FN3 were 28.
6 emu/g.
94 emu/g.
9 emu/g, respectively.
The result of FN4 has the highest magnetic saturation value compared to the results of FN1.
FN2, and FN3 because the Fe4N phase is formed in the gas nitriding process.
The lowest magnetic saturation value is obtained in the FN3 sample, which consists of more Fe2O3 than iron nitride.
Therefore, a lower magnetic saturation value is achieved.
The value of saturation magnetization, retentivity, and coercivity is listed in Table 4.
The value of magnetization is related to the number of phases present in the samples.
shown in Table 3, the FN4 sample consists of Fe3O4.
Fe3N, and Fe4N.
The FN2 sample contains only Fe2O3 and Fe3N.
Fe4N has larger magnetization than Fe3N .
, .
Therefore, the FN4 has a larger magnetic saturation value than the FN2 sample.
The magnetization value of all samples is lower Mechanical Engineering for Society and Industry.
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than the result reported by other studies .
, .
, .
, .
The lower value obtained in this study is caused by the presence of contaminants in the form of the initial sample phases, namely Fe2O3 and Fe3O4.
Magnetic saturation values of the two phases are smaller than the results of Fe3N .
and Fe4N .
The effect of contaminants on magnetic saturation value has been reported in .
, and .
The decrease in magnetic saturation of the samples is attributed to the presence of contaminants i.
Fe2O3 and Fe3O4.
The coercive fields of each sample FN1.
FN2.
FN3, and FN4 are 94.
29 Oe, 104.
94 Oe, 386.
Oe, and 137.
63 Oe.
The highest coercivity value is on FN3, and the lowest is on FN1.
In principle, the coercivity value of the iron nitrides samples is higher than typical soft magnetic materials.
From the results of the coercivity field, it can be observed that coercivity increases with the rise in nitriding temperature.
Based on the XRD analysis, listed in Table 3, higher nitriding temperature yields lower amount of Fe3N.
Since Fe3N is considered to have soft magnetic behaviour, the decrease of its amount will Figure 7.
surely effect the coercivity.
Hysteresis curve of iron nitride powders Similar tendency in coercivity (FN1.
FN2.
FN3, and is also reported by Palade et FN.
Table 4.
Magnetic properties of iron nitride powders (FN1.
FN2.
FN3, and FN.
Sample FN1
FN2
FN3
FN4
Saturation Magnetization .
Retentivity .
Coercivity (O.
Conclusion In conclusion, iron nitride was successfully synthesized from natural iron sand using coprecipitation and gas nitriding methods.
Nitriding Fe2O3 powder yielded the Fe3N phase, while nitriding Fe3O4 powder yielded both the Fe4N and Fe3N phases.
These results showed the presence of contaminants in the initial powder phase.
The presence of these phases was attributed to suboptimal conditions during the gas nitriding process.
Surface morphology analysis equipped with EDS analysis showed that iron nitride has irregular shapes, typically irregular lamellar structures.
VSM testing showed that the FN4 sample has the highest magnetic saturation i.
, 75.
41 emu/g.
The lowest magnetic saturation was obtained in the FN3 sample with a value of 18.
9 emu/g.
All samples yielded lower magnetization than results reported by other investigations.
The lower magnetization value was attributed to the presence of contaminants such as Fe2O3 and Fe3O4.
Gas nitriding parameters must be optimized in order to obtain only iron nitride phases, specifically Fe4N.
AuthorsAo Declaration AuthorsAo contributions and responsibilities - The authors made substantial contributions to the conception and design of the study.
The authors took responsibility for data analysis, interpretation and discussion of results.
The authors read and approved the final manuscript.
Funding Ae No funding information from the authors.
Availability of data and materials - All data is available from the authors.
Competing interests - The authors declare no competing interests.
Additional information Ae No additional information from the authors.
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References