| ホーム | 渡辺教授 | 研究 | 業績 | 装置 | メンバー | 卒業生 | 学生業績 |
| 講義 | 学会報告 | 入学希望者 | トピックス | サイトマップ |
論文題目「Nanoparticle Synthesis of Metal-doped ZrN by Induction Thermal Plasma」
Kaiwen Zhang
| 講義 | 学会報告 | 入学希望者 | トピックス | サイトマップ |
論文題目「Nanoparticle Synthesis of Metal-doped ZrN by Induction Thermal Plasma」
Kaiwen Zhang
Introduction
Induction thermal plasma has unique advantages such as ultra-high temperature even up to 10,000 K, high cooling rate about 10^4–10^6 K/s, no contamination since less of electrode, as well as long residence time. Due to its wide range of operating parameters, induction thermal plasma can be considered as an innovative and powerful tool for synthesis of functional nanoparticles with high purity.
Zirconium nitride (ZrN) is widely used as diffusion barriers, hard coatings, and corrosion-resistant layers on optical and mechanical components. Limited oxygen resistance restricts further usage of ZrN, especially when temperature surpasses 700℃. Doping reactive elements is considered as a useful mean to inhibit oxidization because dopant ions diffuse outwardly and segregate in grain boundaries. This phenomenon reduces inward diffusion rate of the oxygen molecule effectively during high-temperature oxidation. Furthermore, doped ZrN nanoparticle has large potential on the field of photocatalyst due to the decrease of band gap energy.
Induction thermal plasma has been widely applied on the material doping. Ishigaki et al., reported the synthesis and formation mechanism of cobalt and iron-doped TiO2 nanopowder by induction thermal plasma. This research is aim to synthesize metal-doped ZrN nanoparticles with high purity and understand formation mechanism. Ta, Nb, and Al are selected as dopants because these three metals were reported to enhance electronic and mechanical properties of ZrN.
Experiment
The experiment equipment mainly consists of plasma torch, reaction chamber, power supply of 4MHz at plate power of 20 kW, and quenching tube. The raw materials are supplied as powder along with carrier gas and injected into plasma torch. Raw materials then evaporate instantly and nanoparticles are produced through homogeneous nucleation and heterogeneous condensation in the tail region of plasma flame. Final product is collected from inner chamber wall and filter.
Argon is taken as sheath gas, carrier gas, and inner gas. The mixture of ammonia and argon is used as quenching gas. Each experiment was conducted with the quenching tube fixed at 150 mm downstream from the end of the torch. The raw material is composed of ZrN and dopant materials including Ta, Nb, and aluminium nitride. ZrN and dopant materials are mixed at given composition and then fed into plasma system at feed rate of 300 mg/min.
The phase composition of product and lattice constant was detected by X-ray diffractometry (XRD, Rigaku Multiflex), operating with a Cu Kα source (λ = 0.1541 nm). Lattice constant a is calculated by the following equation, based on the Bragg’s law. Element distribution were measured by scanning TEM-energy dispersive X-ray spectrometry (STEM-EDS, JEOL JEMARM 200F). Element mole ratio and bond information were obtained by X-ray photoelectron spectroscopy (XPS).
Results
The XRD patterns of Ta, Nb, and Al-doped ZrN nanoparticles shows that the products under all experiment conditions exhibit main peak from ZrN. The peak of ZrO2 comes from passivation process and Zr2N is generated from nitridation deficiency. This result can confirm high purity of final product. Lattice constants of three different doping conditions are obtained from Bragg’s law calculation. Lattice constant of ZrN decreases when Zr4+ ions are replaced by elements with smaller ionic radius (Nb5+ and Al3+). Lattice constant does not change with doping of Ta, which has the same ionic radius as Zr4+ ions.
The XPS survey analysis of different metals-doped ZrN show that main peaks come from Zr, N, O, and dopant elements. Other peaks belong to Au from reference and carbon from conductivity type. The integrated intensity of Zr and dopant peak from survey scan analysis can provide information about mole ratio of Zr to dopant in final product. The mole ratio is similar with that of raw material, indicating most dopant elements enter final product. Narrow scan analysis of dopant elements indicate that metal-nitride bonds exist in all samples, which come from Zr4+ replacement in ZrN lattice. Metal-oxide bonds are from oxidation on particle surface.
Nanoparticle with mole ratio of Zr : Al=90 :10 is selected as representative to exhibit the particle morphology and element distribution of Zr and dopant. All particle exhibits spherical structure and average particle diameter is 10.8 nm with the standard deviation of 3.28. Element mapping image by STEM-EDS shows taht the mole ratio shows small value in all selected points. Results suggest that Zr is well overlapped by Al, indicating that elements distribute evenly in the whole particle.
Discussion
Homogeneous nucleation temperatures of metals can be calculated based on nucleation theory considering non-dimensional surface tension. When nucleation rate is above unity, nucleation can become stable. The saturation ratio at this time has dominant influence on determining nucleation temperature. Compound melting point is normally considered as nucleation temperature because compounds usually nucleate near their melting point.
The nucleation temperature of ZrN is the highest with the doping of Nb and Al, suggesting that ZrN nucleates firstly during synthesis of Nb and Al-doped ZrN. However, nucleation temperature of Ta and TaN is higher than that of ZrN. The equilibrium diagram shows that Ta amount is sufficiently small to decrease nucleation temperature of TaN, which is lower than that of ZrN. The existence of Ta vapor is observed after ZrN nucleation, indicating Ta is likely to be doped into ZrN.
Formation mechanism is clarified based on above-mentioned discussion. Raw material is evaporated in thermal plasma region. ZrN nucleates firstly at 3253 K and dopant element and Zr-N vapor then condense near ZrN nucleate from upstream to downstream of synthesis process. Passivation is finally operated to form oxidation protect layer on particle surface.
Conclusion
Metal-doped ZrN nanoparticles were successfully synthesized by induction thermal plasma. The product exhibits even element distribution, enough doping amount, and high purity. Formation mechanism was clarified based on nucleation temperature and thermal equilibrium calculation. ZrN firstly nucleates and dopant elements enter zirconium nitride during the condensation process to form final product.
国際学会
Induction thermal plasma has unique advantages such as ultra-high temperature even up to 10,000 K, high cooling rate about 10^4–10^6 K/s, no contamination since less of electrode, as well as long residence time. Due to its wide range of operating parameters, induction thermal plasma can be considered as an innovative and powerful tool for synthesis of functional nanoparticles with high purity.
Zirconium nitride (ZrN) is widely used as diffusion barriers, hard coatings, and corrosion-resistant layers on optical and mechanical components. Limited oxygen resistance restricts further usage of ZrN, especially when temperature surpasses 700℃. Doping reactive elements is considered as a useful mean to inhibit oxidization because dopant ions diffuse outwardly and segregate in grain boundaries. This phenomenon reduces inward diffusion rate of the oxygen molecule effectively during high-temperature oxidation. Furthermore, doped ZrN nanoparticle has large potential on the field of photocatalyst due to the decrease of band gap energy.
Induction thermal plasma has been widely applied on the material doping. Ishigaki et al., reported the synthesis and formation mechanism of cobalt and iron-doped TiO2 nanopowder by induction thermal plasma. This research is aim to synthesize metal-doped ZrN nanoparticles with high purity and understand formation mechanism. Ta, Nb, and Al are selected as dopants because these three metals were reported to enhance electronic and mechanical properties of ZrN.
Experiment
The experiment equipment mainly consists of plasma torch, reaction chamber, power supply of 4MHz at plate power of 20 kW, and quenching tube. The raw materials are supplied as powder along with carrier gas and injected into plasma torch. Raw materials then evaporate instantly and nanoparticles are produced through homogeneous nucleation and heterogeneous condensation in the tail region of plasma flame. Final product is collected from inner chamber wall and filter.
Argon is taken as sheath gas, carrier gas, and inner gas. The mixture of ammonia and argon is used as quenching gas. Each experiment was conducted with the quenching tube fixed at 150 mm downstream from the end of the torch. The raw material is composed of ZrN and dopant materials including Ta, Nb, and aluminium nitride. ZrN and dopant materials are mixed at given composition and then fed into plasma system at feed rate of 300 mg/min.
The phase composition of product and lattice constant was detected by X-ray diffractometry (XRD, Rigaku Multiflex), operating with a Cu Kα source (λ = 0.1541 nm). Lattice constant a is calculated by the following equation, based on the Bragg’s law. Element distribution were measured by scanning TEM-energy dispersive X-ray spectrometry (STEM-EDS, JEOL JEMARM 200F). Element mole ratio and bond information were obtained by X-ray photoelectron spectroscopy (XPS).
Results
The XRD patterns of Ta, Nb, and Al-doped ZrN nanoparticles shows that the products under all experiment conditions exhibit main peak from ZrN. The peak of ZrO2 comes from passivation process and Zr2N is generated from nitridation deficiency. This result can confirm high purity of final product. Lattice constants of three different doping conditions are obtained from Bragg’s law calculation. Lattice constant of ZrN decreases when Zr4+ ions are replaced by elements with smaller ionic radius (Nb5+ and Al3+). Lattice constant does not change with doping of Ta, which has the same ionic radius as Zr4+ ions.
The XPS survey analysis of different metals-doped ZrN show that main peaks come from Zr, N, O, and dopant elements. Other peaks belong to Au from reference and carbon from conductivity type. The integrated intensity of Zr and dopant peak from survey scan analysis can provide information about mole ratio of Zr to dopant in final product. The mole ratio is similar with that of raw material, indicating most dopant elements enter final product. Narrow scan analysis of dopant elements indicate that metal-nitride bonds exist in all samples, which come from Zr4+ replacement in ZrN lattice. Metal-oxide bonds are from oxidation on particle surface.
Nanoparticle with mole ratio of Zr : Al=90 :10 is selected as representative to exhibit the particle morphology and element distribution of Zr and dopant. All particle exhibits spherical structure and average particle diameter is 10.8 nm with the standard deviation of 3.28. Element mapping image by STEM-EDS shows taht the mole ratio shows small value in all selected points. Results suggest that Zr is well overlapped by Al, indicating that elements distribute evenly in the whole particle.
Discussion
Homogeneous nucleation temperatures of metals can be calculated based on nucleation theory considering non-dimensional surface tension. When nucleation rate is above unity, nucleation can become stable. The saturation ratio at this time has dominant influence on determining nucleation temperature. Compound melting point is normally considered as nucleation temperature because compounds usually nucleate near their melting point.
The nucleation temperature of ZrN is the highest with the doping of Nb and Al, suggesting that ZrN nucleates firstly during synthesis of Nb and Al-doped ZrN. However, nucleation temperature of Ta and TaN is higher than that of ZrN. The equilibrium diagram shows that Ta amount is sufficiently small to decrease nucleation temperature of TaN, which is lower than that of ZrN. The existence of Ta vapor is observed after ZrN nucleation, indicating Ta is likely to be doped into ZrN.
Formation mechanism is clarified based on above-mentioned discussion. Raw material is evaporated in thermal plasma region. ZrN nucleates firstly at 3253 K and dopant element and Zr-N vapor then condense near ZrN nucleate from upstream to downstream of synthesis process. Passivation is finally operated to form oxidation protect layer on particle surface.
Conclusion
Metal-doped ZrN nanoparticles were successfully synthesized by induction thermal plasma. The product exhibits even element distribution, enough doping amount, and high purity. Formation mechanism was clarified based on nucleation temperature and thermal equilibrium calculation. ZrN firstly nucleates and dopant elements enter zirconium nitride during the condensation process to form final product.
  |
| International Conference of Young Researchers on Advanced Materials Student Presentation Award (2022年9月) 「Nanoparticle Synthesis of Tantalum Oxynatiride by Induction Thermal Plasma」 |
国際学会
- Student Presentation Award Kaiwen Zhang, Yuta Tanoue, Manabu Tanaka, and Takayuki Watanabe: Nanoparticle Synthesis of Tantalum Oxynatiride by Induction Thermal Plasma, The 5th International Union of Materials Research Societies International Conference of Young Researchers on Advanced Materials, C-O4-002, p.116 (2022.8.4 Kyushu University).
- Kaiwen Zhang, Manabu Tanaka, and Takayuki Watanabe: Nanoparticle Synthesis of Heteroatoms-Doped ZrN by Induction Thermal Plasma, 32nd Materials Reserch Society of Japan, E-O6-005 (2022.12.6 Yokohama, Industry & Trade Center Building).
- Yirong Wang, Kaiwen Zhang, Kohei Yamashita, Manabu Tanaka, and Takayuki Watanabe: Synthesis of Ternary Ti1-xNbxN Nanoparticles by Induction Thermal Plasma, 32nd Materials Reserch Society of Japan, E-O5-018 (2022.12.5 Yokohama, Industry & Trade Center Building).
- Kaiwen Zhang, Manabu Tanaka, and Takayuki Watanabe: Nanoparticle Synthesis of Heteroatoms-Doped ZrN by Induction Thermal Plasma, 2022 International Industry-University-Research-Application Cooperation Conference (2022.12.10 On-Line).
- Han Chen, Kohei Yamashita, Kaiwen Zhang, Manabu Tanaka, and Takayuki Watanabe: Nanoparticle Synthesis of Transition Metal Oxynitride by Induction Thermal Plasma, Proceedings of 25th International Symposium on Plasma Chemistry, POS-7-103 (2023.5.22 Miyako Messe, Kyoto).
- Yirong Wang, Kohei Yamashita, Kaiwen Zhang, Manabu Tanaka, and Takayuki Watanabe: Nanoparticle Synthesis of Ternary Titanium Niobium Nitrides by Induction Thermal Plasmas, Proceedings of 25th International Symposium on Plasma Chemistry, POS-7-121 (2023.5.22 Miyako Messe, Kyoto).
- Kaiwen Zhang, Kohei Yamashita, Manabu Tanaka, and Takayuki Watanabe: Formation Mechanism of Metal-Doped ZrN by Induction Thermal Plasma, Proceedings of 25th International Symposium on Plasma Chemistry, POS-7-223 (2023.5.23 Miyako Messe, Kyoto).
- Kaiwen Zhang, Manabu Tanaka, and Takayuki Watanabe: Nanoparticle Formation Mechanism of Metal-Doped ZrN by Induction Thermal Plasma, 2023 International Industry-University-Research-Application Cooperation Conference (2023.12.16 On-Line).
- Yirong Wang, Kaiwen Zhang, Han Chen, Motonori Hirose, Manabu Tanaka, and Takayuki Watanabe: Synthesis of Tenary Titanium-Transition Metal Nitrides Nanoparticles by Induction Thermal Plasmas, 16th International Symposium on Advanced Plasma Science and Its Applications for Nitrides and Nanomaterials, 05aC03O (2024.3.5 Nagoya University).
- 田中学, Zhang Kaiwen, 渡辺隆行: 高周波熱プラズマを用いたTa酸窒化物ナノ粒子の組成制御, 第37回九州・山口プラズマ研究会資料集, p.12-13 (2022.11.6).
- Han Chen, Yirong Wang, Kaiwen Zhang, 廣瀨基規, 田中学, 渡辺隆行: 高周波熱プラズマを用いた高融点金属酸窒化物ナノ粒子の合成, プラズマ・核融合学会九州・沖縄・山口支部第27回支部大会研究発表論文集, p.75-76, D-2 (2023.12.10 KDDI維新ホール).
- 田中学, 陳翰, 張楷文, 王芸融, 廣瀨基規, 渡辺隆行: 高周波熱プラズマによるタンタル酸窒化物ナノ粒子の合成, 第41回プラズマプロセシング研究会, 24a-3 (2024.1.24 東京工業大学).
