Iron-based powder for supplying iron ions

Abstract

Provided is an iron-based powder for supplying iron ions that achieves an improvement in the growth of a plant (crop) due to the dissolving of divalent iron ions as well as an increase in the yield of the obtained crop through this improvement. In the diffraction peak of X-ray diffraction of an iron-based powder constituting the iron-based powder for supplying iron ions, the lattice spacing obtained from the rocking curve corresponding to the (110) diffraction plane of the α-Fe crystal is in the range of 2.000 Å to 2.100 Å.

Description

[Technical Field]

[0001] The present invention relates to an iron-based powder for supplying iron ions, which supplies iron ions that contribute to plant growth. [Background technology]

[0002] Iron is an essential nutrient for plant growth, and plays a role in chlorophyll synthesis, energy production in mitochondria, and conversion of nitrogen fertilizer to amino acids.

[0003] Plants absorb this iron as divalent ferric ions, but if there is a shortage of iron in the soil, it can cause poor growth of new shoots, as seen in the yellowing of rice plants, and result in reduced rice yields. Taking paddy fields as an example, when fertilizer containing sulfate ions is used when there is a shortage of iron in the soil as described above, hydrogen sulfide is generated from the soil in the paddy fields, causing poor growth of rice roots and causing the rice plants to fall over due to reduced root penetration into the soil, and also reducing rice yields due to reduced absorption of nutrients from the soil. In any case, in order to improve plant growth, it is necessary to provide a stable and continuous supply of divalent iron ions, and as a means for achieving this, attention has traditionally been focused on iron ion supplying materials.

[0004] As an example of such an iron ion supplying material, Patent Document 1 discloses an iron powder that contains 80% by mass or more of iron and 0.4% to 1.5% by mass of oxygen, with 50% by mass or more of the total having a particle size of 100 μm to 10 mm, as a material that stably supplies divalent iron ions to plants.

[0005] Furthermore, Patent Document 2 discloses a plant growth promoter that comprises ferrous oxide and a chelating substance to allow plants to efficiently absorb iron. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-119685 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-123677 Summary of the Invention [Problem to be solved by the invention]

[0007] In paddy fields and fields, where moisture is present, divalent iron ions are eluted from the spread iron powder, and at the same time, the surface of the iron powder is oxidized by oxygen dissolved in the water and oxygen in the air, producing mainly iron oxyhydroxide and iron oxide.

[0008] Because such iron oxyhydroxides and iron oxides act as passive particles, the amount of divalent iron ions leaching from the iron powder decreases once the iron powder has oxidized to a certain extent. Furthermore, since iron-reducing bacteria of the genus Geobacter and Anaeromyxobacter exist in soil (Monthly Modern Agriculture, October 2020 issue), the trivalent iron in the iron oxyhydroxides and iron oxides is reduced to divalent iron by these iron-reducing bacteria, which then leaches out as divalent iron ions, but this leaching takes time.

[0009] That is, as described in Patent Document 1, when iron powder containing a large amount of metallic iron with a low oxygen concentration is spread, the surface of the iron powder is oxidized after spreading, and then iron-reducing bacteria reduce the oxidized portion. Although this contributes significantly to plant growth, it takes a relatively long time for the effect to be realized.

[0010] Furthermore, as described in Patent Document 2, when ferrous oxide is sprayed, the surface of the ferrous oxide (FeO) is first oxidized to iron oxyhydroxide or iron oxide and then reduced by iron-reducing bacteria, so the amount of eluted divalent iron ions is reduced, and even if elution occurs, it takes a long time to obtain the required amount.

[0011] The present invention aims to solve the above problems and provide an iron-based powder for supplying iron ions, which improves the growth conditions of plants (crops) by dissolving divalent iron ions, and thereby increases the yield of the crops. [Means for solving the problem]

[0012] When a solid substance is subjected to mechanical energy such as crushing, impact, or friction, its crystalline properties change. When distortion occurs in the crystalline structure of the solid, it becomes chemically activated and more susceptible to chemical reactions.

[0013] Therefore, in order to solve the above-mentioned problems, the inventors have focused on the chemical activity of iron-based powders and conducted studies with the aim of promoting the elution of divalent iron ions from the iron-based powders. As a result, they have found that divalent iron ions can be effectively eluted by controlling the lattice spacing determined from the diffraction intensity curve corresponding to the (110) diffraction plane of an α-Fe crystal. It was also found that the particle size of the chemically activated iron-based powder is not affected much by the particle size, and therefore the particle size of the iron-based powder does not necessarily have to be specified.

[0014] The present invention is based on the above findings and has the following gist and configuration. 1. An iron-based powder for supplying iron ions that supplies iron ions that contribute to plant growth, wherein the lattice spacing determined from the diffraction intensity curve corresponding to the (110) diffraction plane of an α-Fe crystal among the diffraction peaks of X-ray diffraction of the iron-based powder that constitutes said iron-based powder for supplying iron ions is in the range of 2.000 Å to 2.100 Å.

[0015] 2. Median diameter D 50 is 50 μm or more, 10 × 10 3 μm or less and maximum particle size 80 μm or more 30 × 10 3 2. The iron-based powder for supplying iron ions according to 1 above, having a particle size of 1 μm or less. [Effects of the Invention]

[0016] According to the present invention, by limiting the range of lattice spacing corresponding to the (110) diffraction plane of the α-Fe crystal of the iron-based powder, it is possible to provide an iron-ion supplying iron-based powder that has a high iron ion supplying ability that contributes to the growth of plants (crops). DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described. [Among the X-ray diffraction peaks of the iron-based powder constituting the iron-based powder for supplying iron ions, the lattice spacing determined from the diffraction intensity curve corresponding to the (110) diffraction plane of the α-Fe crystal is in the range of 2.000 Å to 2.100 Å] The reason why the iron-based powder for supplying iron ions of the present invention has a high iron ion supplying ability is presumed to be as follows. In the case of iron-based powders, when mechanical energy is applied by pulverization using a pulverizer or mixing using a mixer, distortion occurs in the crystal structure of the iron-based powder particles, improving oxygen reactivity. The distortion of the crystal structure that occurs within iron-based powder particles can be evaluated from the lattice spacing calculated from the X-ray diffraction intensity corresponding to the (110) plane of the α-Fe crystal derived from iron. When compressive stress caused by mechanical energy is applied to the crystal lattice, in which the atoms that make up the α-Fe crystal are arranged three-dimensionally, the lattice spacing increases due to uniform distortion. The effect of improving oxygen reactivity increases with increasing strain. However, if the strain is too large, the effect of iron ion elution due to oxygen reaction caused by moisture in the cultivated land becomes significantly large, and although a large amount of iron ions are eluted in a short time after application, the elution period becomes short. Since a continuous supply of iron ions is required for plant growth, it is necessary to continuously supply a stable amount of iron ions throughout the entire period from the early to late stages of growth, rather than supplying a large amount of iron ions in the early stages of growth. Therefore, the lattice spacing is set to a range of 2.000 Å to 2.100 Å, preferably 2.010 Å to 2.100 Å, and more preferably 2.020 Å to 2.100 Å.

[0018] In the present invention, the lattice spacing is measured as follows. First, X-ray diffraction measurement is performed on the iron-based powder for supplying iron ions to obtain a diffraction intensity curve corresponding to the (110) diffraction plane of the α-Fe crystal. From the diffraction angle θ and the wavelength λ of the characteristic X-rays in the diffraction intensity curve, the lattice spacing d is calculated according to Bragg's law shown in the following equation (1). 2d sinθ=n λ (1) Here, d is the lattice spacing (Å), θ is the diffraction angle (°), n is a natural number, and λ is the wavelength of the X-ray (Å).

[0019] By growing plants using an iron-based powder that satisfies the above-mentioned characteristics, effective iron ion elution can be achieved, leading to improved growth. The iron-based powder can be produced by any of the following methods: atomization (e.g., water atomization, gas atomization, etc.), pulverization, and oxide reduction. The atomization method involves spraying water or gas onto a molten metal, pulverizing it, and then cooling and solidifying it. Either water atomization or gas atomization can be used. The oxide reduction method is a method of reducing iron oxide (mill scale) or iron ore powder that is generated on the surface of a steel sheet during hot rolling of the steel material, for example. The pulverization method is a method of pulverizing small metal pieces using a pulverizer.

[0020] The term "iron-based powder" refers to a metal powder containing 50% by mass or more of Fe. The iron-based powder in the present invention preferably contains 50% by mass or more of metallic iron. The iron-based powder is preferably an iron powder. Here, the iron powder refers to a powder consisting of Fe and inevitable impurities. The inevitable impurities may include C, S, O, N, Si, Mn, P, S, Cr, Cu, etc.

[0021] The method for measuring the metallic iron content of iron-based powders conforms to JIS A 5011-2 "Method for determining metallic iron."

[0022] The iron-based powder preferably has a crystallinity of 90% by volume or more. The degree of crystallinity is calculated as follows. First, the X-ray diffraction spectrum of the iron-based powder is measured by powder X-ray diffraction using Cu-Kα characteristic X-rays. In the obtained X-ray diffraction spectrum, the crystallinity (Vcry) of the iron-based powder is calculated using the following formula (2) based on the area of ​​the broad diffraction pattern (Amo.P) derived from the amorphous phase and the sum of the areas of multiple peaks derived from the crystalline phase (Cry.P). Vcry (volume%) = Cry.P / (Amo.P + Cry.P) × 100 (2)

[0023] In the present invention, the median diameter D of the iron-based powder 50 The maximum particle size is not particularly limited as long as it does not cause any problems in handling, but the median diameter D 50 It is preferable that the median diameter D 50 is 10 x 10 3 It is preferable that the maximum particle size is 80 μm or more. It is also preferable that the maximum particle size is 30×10 3 It is preferable that the thickness is 1 μm or less.

[0024] The particle size specification in Patent Document 1 only limits the particle size to 50% or more by mass of the total iron powder, and is not an index of the particle size of the entire iron powder. In other words, Patent Document 1 allows for the mixing of extremely fine iron powder. However, if there is a large amount of extremely fine iron powder, it may be blown away by the wind during application and cultivation, reducing the amount actually applied to the soil, or reducing the amount of iron powder in the soil that can be used by plant roots, which may result in insufficient effectiveness.

[0025] Furthermore, Patent Document 1 allows for extremely coarse iron powder to be mixed in. If there is a large amount of extremely coarse iron powder, the specific surface area, which is the area per unit mass of the iron powder, becomes small.

[0026] In other words, the leaching of divalent iron ions from iron powder in soil and the oxidation of iron powder begin from the surface of the iron powder. Therefore, the larger the specific surface area of ​​the iron powder, the greater the amount of divalent iron ions leached, and the greater the iron ion leaching effect. On the other hand, if the specific surface area is small, there is a risk that sufficient iron ion leaching effect will not be achieved.

[0027] From the above considerations, it is preferable that the iron-based powder for supplying iron ions of the present invention has the following particle size. That is, the median diameter (median value of particle diameter) D of the iron-based powder for supplying iron ions 50 50 μm or more 10 × 10 3 It is preferable that the particle size is in the range of 100 μm or less, and the maximum particle size is 80 μm or more. The upper limit of the maximum particle size is not particularly limited, but it is, for example, 30×10 3 μm or less is preferable. The iron-based powder for supplying iron ions is too fine (D 50 This is because if the particle size is less than 50 μm or the maximum particle size is less than 80 μm, the iron-based powder may be blown away by the wind during application or cultivation, which may lead to a decrease in the amount actually applied to the soil and a decrease in the amount of iron-based powder in the soil that is available to plant roots.

[0028] On the other hand, D 50 is 10 x 10 3 μm or the maximum particle size is 30×10 3 If the particle size is larger than 1 μm, the particles will be too coarse overall, resulting in a small specific surface area. Since the leaching of divalent iron ions from iron-based powder in soil and the oxidation of iron-based powder both occur from the surface of the iron-based powder, an excessively small specific surface area may reduce the amount of leaching of divalent iron ions. Therefore, it is preferable to satisfy the above-mentioned particle size regulations.

[0029] In the present invention, the powder D 50 The method for measuring the maximum particle size is in accordance with JIS Z 8815 "General rules for sieving test methods."

[0030] Median diameter D of iron-based powder for supplying iron ions 50Specifically, in order to adjust the particle size to 50 μm or more, classification using a sieve may be carried out. On the other hand, the median diameter D of the iron-based powder for supplying iron ions 50 10 x 10 3 To adjust the particle size to 1 μm or less, specifically, the crushing conditions for the iron-based powder as the raw material may be adjusted.

[0031] To adjust the maximum particle size of the iron-based powder for supplying iron ions to 80 μm or more, specifically, classification using a sieve may be carried out. On the other hand, the maximum particle size of the iron-based powder for supplying iron ions is set to 30 × 10 3 To adjust the particle size to 1 μm or less, specifically, the crushing conditions for the iron-based powder as the raw material may be adjusted.

[0032] [Manufacturing of iron-based powder] The iron-based powder according to the present invention can be produced by subjecting an iron-based powder produced by a method such as atomization, oxide reduction, or pulverization to a treatment for increasing the strain of the α-Fe crystal. First, the iron-based powder used in the present invention is preferably produced by water atomization, gas atomization, oxide reduction, or pulverization. Furthermore, the produced powder may be classified or mixed by various methods to prepare the iron-based powder according to the present invention.

[0033] Next, in the present invention, the iron-based powder obtained by the above-mentioned method must be subjected to a treatment to increase the distortion of the α-Fe crystals in the iron-based powder for supplying iron ions. This treatment is preferably a treatment in which mechanical energy is applied using a mixer or a pulverizer. Mixers such as a V-type mixer, double cone mixer, conical blender, and agitator granulator, or pulverizers such as a ball mill, vibration mill, roller mill, jet mill, hammer mill, and disk mill can all be suitably used.

[0034] When using the above mixer or pulverizer, appropriate mixing or pulverization conditions can be set to impart strain to the α-Fe crystals and adjust the lattice spacing to fall within the range of the present invention. [Example]

[0035] The iron-based powder used in this example was prepared by the following procedure. To evaluate the ability of iron-based powders for supplying iron ions to plants, iron-based powders with the particle sizes shown in Table 1 were prepared. First, mill scale generated during the hot rolling of steel was reduced to produce iron powder. Next, a high-speed mixer (manufactured by EarthTechnica Corporation) was used as an agitation granulator to agitate 1 kg of each iron powder, thereby obtaining iron-based powders for supplying iron ions having particle sizes and the like shown in Table 1. All of the iron-based powders for supplying iron ions were iron powders. The agitation was carried out by using an agitator blade in a sample-loading container at a constant rotation speed of 500 rpm, while varying the agitation time.

[0036] The properties of the iron-based powder in this example were evaluated as follows. The iron-based powder according to the example was measured in accordance with JIS Z 8815 "General rules for sieving test methods," and the maximum particle size and the median diameter D, which is the representative value of the particle size, were determined from the particle size distribution based on mass. 50 He asked for this.

[0037] Furthermore, the lattice spacing of the X-ray diffraction intensity curve of the (110) plane of the powdered α-Fe crystal was measured as follows. That is, an X-ray diffractometer (SmartLab manufactured by Rigaku Corporation) was used to measure the iron-based powder to be measured using Cu-Kα characteristic X-rays (wavelength 1.54178 Å) at a scanning speed of 4° / min and a measurement angle in the range of 35° to 55°, thereby obtaining a diffraction intensity curve of the (110) plane of the α-Fe crystal in the iron-based powder. Then, from the diffraction angle and the wavelength of the characteristic X-rays in the diffraction intensity curve, the lattice spacing was calculated using the above-mentioned formula (2). More specifically, the measurement was performed in accordance with JIS K 0131 "General rules for X-ray diffraction analysis." Furthermore, using the above-mentioned method, it was confirmed that the iron-based powder according to the example had a metallic iron content of 50% or more and a crystallinity of 90% or more by volume.

[0038] To evaluate the ability to supply iron ions to plants, rice was cultivated in paddy fields as follows. The iron-based powders according to Comparative Examples 1 to 8 and Invention Examples 1 to 12 were each collected in 100 m 2 The iron ion supply capacity to rice was evaluated based on the mass of harvested rice. Conventional Example 1 was used when rice was grown without applying the iron-based powder, and the mass of harvested rice per unit area in this case was set to 100. The mass of harvested rice when each iron-based powder was used was shown as a mass ratio to Conventional Example 1. A larger value indicates a larger mass of harvested rice and a higher ability to supply divalent iron ions. In other words, the iron ion supply ability in this example was evaluated from the mass of harvested rice per unit area. Table 1 shows the mass ratio of harvested rice per unit area as a result of the conventional example, comparative example, and inventive example.

[0039] [Table 1]

[0040] As shown in Table 1, when the iron-based powders of Examples 1 to 12 of the invention, in which the lattice spacing of the diffraction intensity curve of the (110) plane of α-Fe is 2.000 Å or more and 2.100 Å or less, are sprayed, the mass ratio of the harvested rice grains is larger than when the iron-based powders of Conventional Example 1 and Comparative Examples 1 to 8 are sprayed.

[0041] In addition, the lattice spacing of the diffraction intensity curve of the (110) plane of α-Fe is 2.000 Å or more and less than 2.010 Å, and D 50 is 50 μm or more, 10 × 10 3 μm or less, and the maximum particle size is 80 μm or more 30 × 10 3 When the iron-based powders of Examples 3 and 6 to 12, each having a particle size of 1 μm or less, were sprayed, the mass ratio of the harvested rice grains was even greater than that of Examples 1, 2, 4 and 5.

[0042] The lattice spacing of the diffraction intensity curve of the (110) plane of α-Fe is 2.010 Å or more and less than 2.020 Å, and D 50 is 50 μm or more, 10 × 10 3μm or less, and the maximum particle size is 80 μm or more 30 × 10 3 When the iron-based powders of Examples 7 to 12, each of which has a particle size of 1 μm or less, were sprayed, the mass ratio of the harvested rice grains was even greater than that of Examples 3 and 6.

[0043] The lattice spacing of the diffraction intensity curve of the (110) plane of α-Fe is 2.020 Å or more and 2.100 Å or less, and D 50 is 50 μm or more, 10 × 10 3 μm or less, and the maximum particle size is 80 μm or more 30 × 10 3 When the iron-based powders of Examples 9 to 12, each having a particle size of 1 μm or less, were sprayed, the mass ratio of the harvested rice grains was even greater than that of Examples 7 and 8.

[0044] From the above results, it was found that the lattice spacing of the diffraction intensity curve corresponding to the (110) diffraction plane of the α-Fe crystal of the powder contributes to the performance of the iron-based powder for supplying iron ions. It is clear that the use of the iron-based powder for supplying iron ions of the present invention can efficiently supply divalent iron ions to plants, which is effective in increasing plant growth and yield.

Claims

1. An iron-based powder for supplying iron ions that contributes to plant growth, the iron-based powder for supplying iron ions contains 50% by mass or more of metallic iron, The iron-based powder for supplying iron ions has a lattice spacing in the range of 2.000 Å to 2.100 Å, which is determined from a diffraction intensity curve corresponding to the (110) diffraction plane of an α-Fe crystal among the diffraction peaks of X-ray diffraction of the iron-based powder for supplying iron ions.

2. Median diameter D ５０ is 50 μm or more, 10 × 10 ３ μm or less and maximum particle size is 80 μm or more 30 × 10 ３ 2. The iron-based powder for supplying iron ions according to claim 1, wherein the particle size is 0.1 μm or less.

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