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Self-pulverisation oxides added with lanthanum oxide
Accepted Manuscript Self-Pulverisation Oxides Added with Lanthanum Oxide Wakako Araki, Atsushi Yoshinaga, Yoshio Arai PII: DOI: Reference:
S0167-577X(18)31878-0 https://doi.org/10.1016/j.matlet.2018.11.111 MLBLUE 25333
To appear in:
Materials Letters
Received Date: Accepted Date:
12 October 2018 19 November 2018
Please cite this article as: W. Araki, A. Yoshinaga, Y. Arai, Self-Pulverisation Oxides Added with Lanthanum Oxide, Materials Letters (2018), doi: https://doi.org/10.1016/j.matlet.2018.11.111
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Self-Pulverisation Oxides Added with Lanthanum Oxide Wakako Araki*, Atsushi Yoshinaga, and Yoshio Arai
Department of Mechanical Engineering and System Design, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama 3388570, Japan
*Corresponding author. Tel.: +81 48 858 3435. E-mail address: [email protected] (W. Araki).
ABSTRACT In this study, a lanthanum cobaltite (LCO) “self-pulverisation” mechanism was investigated in an attempt use a novel concept when developing materials. The results confirmed that hydroxylation of a small amount of excessive La2O3 in LCO into La(OH)3 caused self-pulverisation of bulk LCO, which initially had a high mechanical strength, into very fine powders within a few weeks, from which cracks initiated and propagated. Other conventional oxides, such as stabilised zirconia. intentionally added with the La2O3, were prepared and their self-pulverisation phenomena were demonstrated.
Keywords: Self-pulverisation; Fracture, Strain; Ceramics; Powder processing
1. Introduction Milling and grinding are conventional techniques to pulverise materials from large powders or bulks to fine powders. Another method is “self”-pulverisation, when materials pulverise
themselves without external work. There are several reports on the self-pulverisation phenomenon of various materials [1-7]. For hydrogen storage materials such as a Ti-Ni alloy [1,2], the self-pulverisation of metal hydrides with a large particle size into fine powders has been observed. This is known as hydrogen decrepitation, which is attributed to a volume expansion of brittle metal hydrides during hydrogenation. For permanent magnet materials such as a Nd-Fe-B alloy [3,4], hydrogen decrepitation has been intentionally used to produce ultrafine powders along with milling for high magnetisation of sintered magnets. For cement materials, self-pulverisation of cement clinkers using C2S was studied to make fine powders with less energy because grinding cement clinkers usually consumes considerable energy [5]. Self-pulverisation of fly ash using C2S was studied for leaching alumina from the pulverised fine powder [6]. Low-rank coal [7] also self-pulverises on combustion as the inherent fuel locked in the pores of coal gets heated and expands rapidly to fragment the fuel particles. In our previous studies on lanthanum-based oxides [8,9], we unexpectedly encountered the self-pulverisation phenomenon. For example, lanthanum cobalt oxide (LaCoO3) samples prepared in a common solid solution were very rarely but occasionally self-pulverised into fine powders at room temperature a few weeks or months after sintering, even though the as-sintered samples had high mechanical strength. Self-pulverisation of materials is an extremely dangerous phenomenon, particularly if it happens unexpectedly in practical applications. However, self-pulverising materials could possibly be used as intelligent materials if they are employed under appropriate controls and used as highly-recyclable materials. In this study, the self-pulverisation mechanism of lanthanum cobaltite was investigated. In addition, the self-pulverisation of other conventional oxides such as stabilised zirconia was attempted. To our best knowledge, this is the first study to intentionally develop self-pulverising functional oxides.
2. Experimental Polycrystalline LaCoO3 (LCO) samples were prepared by solid-state reaction in the present study. The starting powders in a stoichiometric ratio, lanthanum oxide (La2O3, Wako, Japan) and cobalt oxide (Co3O4, Wako, Japan), were mixed for 24 h in a ball mill and calcined at 1473 K for 10 h. The calcined powders were sieved and then pressed into discs under 94 MPa for 5 min, followed by sintering at 1673 K for 10 h. The dimensions of the prepared discs were 24 mm × 3.0 mm. X-ray diffraction analysis (XRD-6100, Shimadzu) was performed with CuK radiation at 40 kV and 30 mA to investigate the crystal structure of the samples. The surface of the samples was observed by using a scanning electron microscope (SEM) (JSM-5600, JEOL and SU1510, Hitachi High-Technologies). Energy dispersive X-ray analysis (EDX) (XFlash 4010, Bruker) equipped in a SEM (SU1510, Hitachi High-Technologies) was also performed for chemical composition analysis. The above analyses were performed every few days until the samples were completely self-pulverised. Note that among the dozens of prepared samples, which all had a compressive strength as high as 800 MPa in our preliminary test, only a few samples were self-pulverised, whereas the others remained intact. In addition, the samples prepared using the fine powders that had previously self-pulverised always self-pulverised again within 2 weeks. (It should be noted that, although the samples were prepared under various sintering and pressing conditions in our preliminary test, these conditions did not affect the self-pulverisation phenomenon.)
3. Results and discussion One prepared LCO sample was completely pulverised within 12 days after sintering. The detailed pulverisation process of this sample, examined every few days, are explained below.
Figure 1 shows the SEM images of the surface of the sample 1, 6, 10, and 12 days after it was prepared. The insets of Fig. 1 show the appearance of this LCO sample during the self-pulverisation process. Macroscopically, the sample appeared to be an intact disc until 6 days (insets of Fig. 1(a) and (b)). At 7 days after sintering, it retained its disc shape but very fine powders began to appear. It started losing its original shape after 10 days (Fig. 1(c)), followed by a complete self-pulverisation after 12 days (Fig. 1(d)). In microscopic observations, the sample after 1 day, shown in Fig. 1(a), had a grain size of 5–10 m and no apparent fracture or crack was observed. The grain structure still appeared unchanged after 6 days, as shown in Fig. 1(b), although transgranular cracks were observed in a few grains. Some powders that appeared on the sample after 6–10 days, shown in Fig. 1(c), were smaller than the original LCO grains and had sharp edges. After 12 days, as shown in Fig. 1(d), the self-pulverised powders that had smaller grains than the original were observed. Figure 2(a)–(c) shows the XRD patterns of a self-pulverising LCO sample 1, 5, and 11 days after sintering. At 1 day after being prepared, the sample had a rhombohedral perovskite structure with a very small amount of excessive La2O3 (Fig. 2(a)). Lanthanum hydroxide (La(OH)3) was observed in the sample 5 and 11 days after being prepared. Figure 2(d) and (e) shows the SEM image and EDX element mapping of one self-pulverised LCO sample 1 day after being prepared. LCO grains with dispersions of smaller La2O3 particles were observed, which also proved the presence of the excessive La2O3 as seen in Fig. 2(a). The excessive La2O3 was probably retained in the sample after the loss of Co3O4 during the preparation process and it was hydroxylated because the sample was kept in ambient air [10]. The above results could indicate that the small amount of excessive La2O3 in LCO hydroxylated to form La(OH)3 by reacting to air humidity along with its volume expansion at a ratio of 1.73 [9]. It could then have fallen out of the sample, which caused stress concentration and a redistribution
of internal stress. This reaction process could have proceeded inward from the sample surface and have eventually caused the complete self-pulverisation. In fact, our additional experiments confirmed a significant volume expansion of the sample during self-pulverisation measured using strain gauges and a strain amplifier (FRA-5-11 and DC-204R, Tokyo Sokki) as shown in Fig. 2(f), where this sample was self-pulverised approximately 3 days after being prepared. Based on the above presumption, LCO samples intentionally added with a small amount of excessive La2O3 (1–3 mol%) were prepared and investigated. As expected, all prepared samples with the excessive La2O3 self-pulverised within 14 days like Fig. 1(d). Figure 3(a) and (b) shows an SEM image and EDX element mapping, respectively, of LCO with 1 mol% of La2O3 during self-pulverisation (3 days after being prepared). There were some agglomerations of La2O3 (or La(OH)3) of a few microns to 50 m in size in this sample, from which the cracks propagated. Figure 3(c) shows the mirror-polished surface of LCO with 3 mol% of La2O3. The dispersion of La2O3 was confirmed by EDX in the LCO sample 1 day after being prepared, and cracks propagating from La2O3 particles were clearly observed after 6 days, first intergranually and then transgranually. These results confirm that a small amount of excessive La2O3 in LCO caused self-pulverisation. Recently, crack formations in La-doped transparent Y2O3 during preparation were reported, which was also attributed to the hydroxylation of La2O3 not incorporated in the Y2O3 lattice [11]. Attempting to develop novel self-pulverising oxides, other conventional ceramics such as 3 mol%-yttria stabilised zirconia (3YSZ) (TZ-3Y, Tosoh), 8 mol%-yttria stabilised zirconia (8YSZ) (TZ-8Y), and lanthanum ferrite [8], with a small amount of excessive La2O3 (3 to 8 mol%) added, were prepared. From these, whether La2O3 could cause self-pulverisation of these oxides was investigated. Despite the high mechanical strength of the as-sintered materials, those samples completely self-pulverised within 15 days, as shown in Fig. 3(d), This can be also attributed to the
hydroxylation of the added La2O3. Our additional experiments revealed that agglomerations of La2O3 with a relatively large size (10 m~) would help the self-pulverisation because they are unincorporated in the matrix lattice.
4. Conclusion In conclusion, a small amount of excessive La2O3 could effectively facilitate self-pulverisation of various oxides because of its hydroxylation into La(OH)3 with volume expansion followed by its falling out, which is where cracks initiate and propagate. Self-pulverising oxides are expected to be used as intelligent materials and as highly-recyclable materials if the phenomenon can be controlled. Further investigation is required to precisely control the self-pulverisation phenomenon by changing the atmosphere and dispersion of La2O3 particles.
Acknowledgements This work is supported by JSPS KAKENHI Grant Number 17K18819.
References [1] Balcerzak M, Jakubowicz J, Kachlicki T, Jurczyk M. J Power Sources 2015;280;435. [2] Balcerzak M, Jurczyk M. J Mater Eng Perform 2015;24;1710. [3] Nakamura M, Matsumura M, Tezuka N, Sugimoto S, Une Y, Kubo H, Sagawa M. Mater Trans 2015;56;129. [4] Saguchi A, Takahashi W, Kaneko Y, Ishigaki N, J Jpn Soc Powder and Powder Metall 1996; 44;90. [5] Zhang X, Zhao M, Zhang Y, Constr Build Mater 2015;34;107. [6] Lin H, Wan L, Yang Y, Adv Mat Res 2012;512;1548. [7] Kumar Rayaprolu, Boilers: A Practical Reference, CRC Press, 2017. [8] Araki W, Abe T, Arai Y, J Appl Phys 2014;116;043513. [9] Araki W, Takeda K, Arai Y, J Eur Ceram Soc 2016;36;4089. [10] Fleming P, Farrell RA, Holmes JD, Morris MA, J Am Ceram Soc 2010;93;1187. [11] Mao X, Li X, Feng M, Fan J, Jiang B, Zhang L, J Eur Ceram Soc 2015;35;3137.
Figure Captions Figure 1 SEM images of self-pulverisation process of LCO: (a) 1 day, (b) 6 days, (c) 10 days, and (d) 12 days after the preparation. The insets show the appearance of the sample observed macroscopically. Arrows in (b) show the microcracks. Figure 2 Excessive La2O3 and La(OH)3 in LCO samples: (a), (b), and (c) are XRD patterns of the sample 1, 5, and 11 days after being prepared, (d) and (e) show SEM and EDX mapping images of the sample 1 day after being prepared, and (f) shows the significant expansive strain observed during the self-pulverisation process. Figure 3 Crack initiation and propagation during self-pulverisation: (a) and (b) show an SEM image and EDX element mapping, respectively, of propagating cracks from La2O3 in LCO with 1 mol% of La2O3, (c) shows the crack initiation and propagation observed on the mirror-polished surface of 3 mol% of La2O3, and (d) shows the self-pulverisation of conventional ceramics added with a small amount of La2O3.
Self-pulverisation mechanism of lanthanum cobaltite was clarified
Self-pulverisation phenomena of other oxides such as zirconia were demonstrated.
This is the first study to develop self-pulverising functional oxides.
Self-pulverisation mechanism of lanthanum cobaltite was clarified
Self-pulverisation phenomena of other oxides such as zirconia were demonstrated.
This is the first study to develop self-pulverising functional oxides.
S0167-577X(18)31878-0 https://doi.org/10.1016/j.matlet.2018.11.111 MLBLUE 25333
To appear in:
Materials Letters
Received Date: Accepted Date:
12 October 2018 19 November 2018
Please cite this article as: W. Araki, A. Yoshinaga, Y. Arai, Self-Pulverisation Oxides Added with Lanthanum Oxide, Materials Letters (2018), doi: https://doi.org/10.1016/j.matlet.2018.11.111
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Self-Pulverisation Oxides Added with Lanthanum Oxide Wakako Araki*, Atsushi Yoshinaga, and Yoshio Arai
Department of Mechanical Engineering and System Design, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama 3388570, Japan
*Corresponding author. Tel.: +81 48 858 3435. E-mail address: [email protected] (W. Araki).
ABSTRACT In this study, a lanthanum cobaltite (LCO) “self-pulverisation” mechanism was investigated in an attempt use a novel concept when developing materials. The results confirmed that hydroxylation of a small amount of excessive La2O3 in LCO into La(OH)3 caused self-pulverisation of bulk LCO, which initially had a high mechanical strength, into very fine powders within a few weeks, from which cracks initiated and propagated. Other conventional oxides, such as stabilised zirconia. intentionally added with the La2O3, were prepared and their self-pulverisation phenomena were demonstrated.
Keywords: Self-pulverisation; Fracture, Strain; Ceramics; Powder processing
1. Introduction Milling and grinding are conventional techniques to pulverise materials from large powders or bulks to fine powders. Another method is “self”-pulverisation, when materials pulverise
themselves without external work. There are several reports on the self-pulverisation phenomenon of various materials [1-7]. For hydrogen storage materials such as a Ti-Ni alloy [1,2], the self-pulverisation of metal hydrides with a large particle size into fine powders has been observed. This is known as hydrogen decrepitation, which is attributed to a volume expansion of brittle metal hydrides during hydrogenation. For permanent magnet materials such as a Nd-Fe-B alloy [3,4], hydrogen decrepitation has been intentionally used to produce ultrafine powders along with milling for high magnetisation of sintered magnets. For cement materials, self-pulverisation of cement clinkers using C2S was studied to make fine powders with less energy because grinding cement clinkers usually consumes considerable energy [5]. Self-pulverisation of fly ash using C2S was studied for leaching alumina from the pulverised fine powder [6]. Low-rank coal [7] also self-pulverises on combustion as the inherent fuel locked in the pores of coal gets heated and expands rapidly to fragment the fuel particles. In our previous studies on lanthanum-based oxides [8,9], we unexpectedly encountered the self-pulverisation phenomenon. For example, lanthanum cobalt oxide (LaCoO3) samples prepared in a common solid solution were very rarely but occasionally self-pulverised into fine powders at room temperature a few weeks or months after sintering, even though the as-sintered samples had high mechanical strength. Self-pulverisation of materials is an extremely dangerous phenomenon, particularly if it happens unexpectedly in practical applications. However, self-pulverising materials could possibly be used as intelligent materials if they are employed under appropriate controls and used as highly-recyclable materials. In this study, the self-pulverisation mechanism of lanthanum cobaltite was investigated. In addition, the self-pulverisation of other conventional oxides such as stabilised zirconia was attempted. To our best knowledge, this is the first study to intentionally develop self-pulverising functional oxides.
2. Experimental Polycrystalline LaCoO3 (LCO) samples were prepared by solid-state reaction in the present study. The starting powders in a stoichiometric ratio, lanthanum oxide (La2O3, Wako, Japan) and cobalt oxide (Co3O4, Wako, Japan), were mixed for 24 h in a ball mill and calcined at 1473 K for 10 h. The calcined powders were sieved and then pressed into discs under 94 MPa for 5 min, followed by sintering at 1673 K for 10 h. The dimensions of the prepared discs were 24 mm × 3.0 mm. X-ray diffraction analysis (XRD-6100, Shimadzu) was performed with CuK radiation at 40 kV and 30 mA to investigate the crystal structure of the samples. The surface of the samples was observed by using a scanning electron microscope (SEM) (JSM-5600, JEOL and SU1510, Hitachi High-Technologies). Energy dispersive X-ray analysis (EDX) (XFlash 4010, Bruker) equipped in a SEM (SU1510, Hitachi High-Technologies) was also performed for chemical composition analysis. The above analyses were performed every few days until the samples were completely self-pulverised. Note that among the dozens of prepared samples, which all had a compressive strength as high as 800 MPa in our preliminary test, only a few samples were self-pulverised, whereas the others remained intact. In addition, the samples prepared using the fine powders that had previously self-pulverised always self-pulverised again within 2 weeks. (It should be noted that, although the samples were prepared under various sintering and pressing conditions in our preliminary test, these conditions did not affect the self-pulverisation phenomenon.)
3. Results and discussion One prepared LCO sample was completely pulverised within 12 days after sintering. The detailed pulverisation process of this sample, examined every few days, are explained below.
Figure 1 shows the SEM images of the surface of the sample 1, 6, 10, and 12 days after it was prepared. The insets of Fig. 1 show the appearance of this LCO sample during the self-pulverisation process. Macroscopically, the sample appeared to be an intact disc until 6 days (insets of Fig. 1(a) and (b)). At 7 days after sintering, it retained its disc shape but very fine powders began to appear. It started losing its original shape after 10 days (Fig. 1(c)), followed by a complete self-pulverisation after 12 days (Fig. 1(d)). In microscopic observations, the sample after 1 day, shown in Fig. 1(a), had a grain size of 5–10 m and no apparent fracture or crack was observed. The grain structure still appeared unchanged after 6 days, as shown in Fig. 1(b), although transgranular cracks were observed in a few grains. Some powders that appeared on the sample after 6–10 days, shown in Fig. 1(c), were smaller than the original LCO grains and had sharp edges. After 12 days, as shown in Fig. 1(d), the self-pulverised powders that had smaller grains than the original were observed. Figure 2(a)–(c) shows the XRD patterns of a self-pulverising LCO sample 1, 5, and 11 days after sintering. At 1 day after being prepared, the sample had a rhombohedral perovskite structure with a very small amount of excessive La2O3 (Fig. 2(a)). Lanthanum hydroxide (La(OH)3) was observed in the sample 5 and 11 days after being prepared. Figure 2(d) and (e) shows the SEM image and EDX element mapping of one self-pulverised LCO sample 1 day after being prepared. LCO grains with dispersions of smaller La2O3 particles were observed, which also proved the presence of the excessive La2O3 as seen in Fig. 2(a). The excessive La2O3 was probably retained in the sample after the loss of Co3O4 during the preparation process and it was hydroxylated because the sample was kept in ambient air [10]. The above results could indicate that the small amount of excessive La2O3 in LCO hydroxylated to form La(OH)3 by reacting to air humidity along with its volume expansion at a ratio of 1.73 [9]. It could then have fallen out of the sample, which caused stress concentration and a redistribution
of internal stress. This reaction process could have proceeded inward from the sample surface and have eventually caused the complete self-pulverisation. In fact, our additional experiments confirmed a significant volume expansion of the sample during self-pulverisation measured using strain gauges and a strain amplifier (FRA-5-11 and DC-204R, Tokyo Sokki) as shown in Fig. 2(f), where this sample was self-pulverised approximately 3 days after being prepared. Based on the above presumption, LCO samples intentionally added with a small amount of excessive La2O3 (1–3 mol%) were prepared and investigated. As expected, all prepared samples with the excessive La2O3 self-pulverised within 14 days like Fig. 1(d). Figure 3(a) and (b) shows an SEM image and EDX element mapping, respectively, of LCO with 1 mol% of La2O3 during self-pulverisation (3 days after being prepared). There were some agglomerations of La2O3 (or La(OH)3) of a few microns to 50 m in size in this sample, from which the cracks propagated. Figure 3(c) shows the mirror-polished surface of LCO with 3 mol% of La2O3. The dispersion of La2O3 was confirmed by EDX in the LCO sample 1 day after being prepared, and cracks propagating from La2O3 particles were clearly observed after 6 days, first intergranually and then transgranually. These results confirm that a small amount of excessive La2O3 in LCO caused self-pulverisation. Recently, crack formations in La-doped transparent Y2O3 during preparation were reported, which was also attributed to the hydroxylation of La2O3 not incorporated in the Y2O3 lattice [11]. Attempting to develop novel self-pulverising oxides, other conventional ceramics such as 3 mol%-yttria stabilised zirconia (3YSZ) (TZ-3Y, Tosoh), 8 mol%-yttria stabilised zirconia (8YSZ) (TZ-8Y), and lanthanum ferrite [8], with a small amount of excessive La2O3 (3 to 8 mol%) added, were prepared. From these, whether La2O3 could cause self-pulverisation of these oxides was investigated. Despite the high mechanical strength of the as-sintered materials, those samples completely self-pulverised within 15 days, as shown in Fig. 3(d), This can be also attributed to the
hydroxylation of the added La2O3. Our additional experiments revealed that agglomerations of La2O3 with a relatively large size (10 m~) would help the self-pulverisation because they are unincorporated in the matrix lattice.
4. Conclusion In conclusion, a small amount of excessive La2O3 could effectively facilitate self-pulverisation of various oxides because of its hydroxylation into La(OH)3 with volume expansion followed by its falling out, which is where cracks initiate and propagate. Self-pulverising oxides are expected to be used as intelligent materials and as highly-recyclable materials if the phenomenon can be controlled. Further investigation is required to precisely control the self-pulverisation phenomenon by changing the atmosphere and dispersion of La2O3 particles.
Acknowledgements This work is supported by JSPS KAKENHI Grant Number 17K18819.
References [1] Balcerzak M, Jakubowicz J, Kachlicki T, Jurczyk M. J Power Sources 2015;280;435. [2] Balcerzak M, Jurczyk M. J Mater Eng Perform 2015;24;1710. [3] Nakamura M, Matsumura M, Tezuka N, Sugimoto S, Une Y, Kubo H, Sagawa M. Mater Trans 2015;56;129. [4] Saguchi A, Takahashi W, Kaneko Y, Ishigaki N, J Jpn Soc Powder and Powder Metall 1996; 44;90. [5] Zhang X, Zhao M, Zhang Y, Constr Build Mater 2015;34;107. [6] Lin H, Wan L, Yang Y, Adv Mat Res 2012;512;1548. [7] Kumar Rayaprolu, Boilers: A Practical Reference, CRC Press, 2017. [8] Araki W, Abe T, Arai Y, J Appl Phys 2014;116;043513. [9] Araki W, Takeda K, Arai Y, J Eur Ceram Soc 2016;36;4089. [10] Fleming P, Farrell RA, Holmes JD, Morris MA, J Am Ceram Soc 2010;93;1187. [11] Mao X, Li X, Feng M, Fan J, Jiang B, Zhang L, J Eur Ceram Soc 2015;35;3137.
Figure Captions Figure 1 SEM images of self-pulverisation process of LCO: (a) 1 day, (b) 6 days, (c) 10 days, and (d) 12 days after the preparation. The insets show the appearance of the sample observed macroscopically. Arrows in (b) show the microcracks. Figure 2 Excessive La2O3 and La(OH)3 in LCO samples: (a), (b), and (c) are XRD patterns of the sample 1, 5, and 11 days after being prepared, (d) and (e) show SEM and EDX mapping images of the sample 1 day after being prepared, and (f) shows the significant expansive strain observed during the self-pulverisation process. Figure 3 Crack initiation and propagation during self-pulverisation: (a) and (b) show an SEM image and EDX element mapping, respectively, of propagating cracks from La2O3 in LCO with 1 mol% of La2O3, (c) shows the crack initiation and propagation observed on the mirror-polished surface of 3 mol% of La2O3, and (d) shows the self-pulverisation of conventional ceramics added with a small amount of La2O3.
Self-pulverisation mechanism of lanthanum cobaltite was clarified
Self-pulverisation phenomena of other oxides such as zirconia were demonstrated.
This is the first study to develop self-pulverising functional oxides.
Self-pulverisation mechanism of lanthanum cobaltite was clarified
Self-pulverisation phenomena of other oxides such as zirconia were demonstrated.
This is the first study to develop self-pulverising functional oxides.