CN101367653B - Method of manufacturing sub-micron trapezoid silicon nitride magnesium polycrystal ceramic powder - Google Patents

Abstract

The present invention relates to a preparation method of submicron orthorhombic silicon magnesium nitride polycrystalline ceramic powder. The difference is that Si-Mg precursor and sodium azide are used for heating and sealing reaction, and Si:Mg:NaN ₃ participating in the reaction is controlled. =1:1-2.75:1-3.25, the heating temperature is 450-600°C, the reaction time is 4-12 hours, and the product can be washed and dried to obtain granular irregular submicron orthorhombic silicon magnesium nitride Polycrystalline ceramic powder. Compared with the prior art, the present invention has the following advantages: 1) the synthesis route of magnesium silicon nitride is carried out simultaneously with the growth of submicron polycrystals, which realizes mild reaction conditions, and the preparation process is relatively simple, especially the preparation temperature has a wide range 2) The product MgSiN ₂ ceramic powder has irregular appearance, sub-micron particle size, relatively uniform distribution, good crystallization degree, high purity and uniform size.

Description

Preparation method of submicron orthorhombic silicon magnesium nitride polycrystalline ceramic powder

technical field

The invention relates to the field of preparation of ceramic materials, in particular to a preparation method of submicron orthorhombic silicon magnesium nitride polycrystalline ceramic powder.

Background technique

MgSiN ₂ has high thermal conductivity, high electrical resistance, relatively good fracture toughness and hardness, oxidation resistance up to 920°C, low dielectric constant, low dielectric loss, and good thermal shock resistance. It is used in various fields, especially in Electronics, national defense, and aerospace have good applications. Submicron orthorhombic magnesium silicon nitride polycrystalline powder has great application prospects in the preparation of high-density integrated circuit substrate materials, β-Si ₃ N ₄ rod crystals, and luminescent materials.

It is known that there are three methods for synthesizing magnesium silicon nitride, including high-temperature direct nitriding method, carbothermal reduction method, and self-propagating high-temperature synthesis method. There are not many patent reports on the synthesis and preparation methods of silicon magnesium nitride, such as the preparation of silicon magnesium nitride powder by self-propagating high temperature synthesis method.

It has been reported to use Mg ₃ N ₂ +Si ₃ N ₄ , Mg+Si ₃ N ₄ , Mg+Si three systems to react with 99.95% nitrogen at 1250°C to prepare MgSiN ₂ polycrystalline powder, carbon powder and magnesium silicic acid MgSiN ₂ polycrystalline powder was prepared by reaction of salt and nitrogen at 1250°C, Mg+Si, pre-sintered Mg ₂ Si and Mg+Si ₃ N ₄ were reacted in a combustion synthesis furnace under different nitrogen pressures to prepare MgSiN ₂ polycrystalline powder Crystal powder. The above-mentioned existing process has high requirements on temperature and consumes a lot of resources.

Contents of the invention

The problem to be solved by the present invention is to propose a method for preparing submicron _MgSiN2 polycrystalline ceramic powder in view of the above-mentioned prior art. The reaction conditions are mild and the preparation process is simple. Significantly lower.

The solution adopted by the present invention to solve the above-mentioned problems is: the preparation method of submicron orthorhombic silicon magnesium nitride polycrystalline ceramic powder, which is characterized in that the heating and sealing reaction is carried out with Si-Mg precursor and sodium azide, and the control Participating in the reaction Si:Mg:NaN ₃ =1:1-2.75:1-3.25, the above is the molar ratio, the heating temperature is 450-600°C, the reaction time is 4-12 hours, the product can be obtained by washing and drying Granular irregular submicron orthorhombic magnesium silicon nitride polycrystalline ceramic powder.

According to the above scheme, the washing refers to ultrasonically washing the product obtained by the reaction with absolute ethanol, dilute hydrochloric acid or dilute nitric acid, and distilled water for 5-20 minutes, centrifuging and purifying.

According to the above scheme, the Si—Mg precursor is SiO ₂ +Mg, Si+Mg, [Mg ₂ Si] or pre-sintered Mg ₂ Si.

According to the above scheme, the [Mg ₂ Si] refers to Si powder and Mg powder according to the molar ratio Si:Mg of 1:2, weighed and mixed, and obtained after ball milling for 24 hours.

According to the above scheme, the pre-sintered Mg ₂ Si refers to Si powder and Mg powder according to the molar ratio Si:Mg of 1:2, mixed after weighing, and sintered at 700°C for 48 hours.

The aforementioned SiO ₂ +Mg and Si+Mg respectively refer to the mixture of SiO ₂ and magnesium, and the mixture of silicon and magnesium, all of which are analytically pure.

The submicron-sized MgSiN ₂ polycrystalline ceramic powder prepared by the present invention is composed of [Mg ₂ Si], Mg+Si, SiO ₂ +Mg, and pre-sintered Mg ₂ Si four Si—Mg precursors, respectively, and a stack of nitrogen sources. Sodium nitrogen (NaN ₃ ) reaction, the chemical reaction equation can be expressed as:

[Mg ₂ Si]+2NaN ₃ ＝MgSiN ₂ +2Na+Mg+2N ₂ (1)

2Si+2Mg+2NaN ₃ ＝2MgSiN2+ ₂ Na+N ₂ (2)

3SiO ₂ +8Mg+2NaN ₃ =3MgSiN ₂ +5MgO+Na ₂ O(3)

Mg ₂ Si (pre-sintered) + 2NaN ₃ = MgSiN ₂ + 2Na + Mg + 2N ₂ (4)

Sodium azide is a relatively cheap solid nitrogen source, and the sodium azide generated after thermal decomposition has a low melting point (97.82°C), which can not only be used as a reactant and endothermic agent to change chemical reactions and ease reactions, but also It is also used as a growth medium for submicron polycrystalline silicon magnesium nitride, so that products with better crystallization, higher purity and uniform appearance can be prepared.

SiO ₂ , Mg, Si, NaN ₃ and other reagents used in the present invention are analytical reagents. Weigh the corresponding reactants according to the pre-designed ratio of reactants, add them into a stainless steel reaction kettle with a volume of about 20ml, put the sealed reaction kettle into a well-type crucible boiler, and set it at a predetermined temperature (450-600°C) ) constant temperature reaction for 4-12 hours. Then cool naturally, open the kettle and process and collect the product. The product is dissolved in anhydrous ethanol to dissolve sodium metal, and then washed with distilled water to remove water-soluble impurities. An appropriate amount of dilute hydrochloric acid or nitric acid is also added to treat the initial product, so as to remove it. Alkali metals and their oxides. The washed product was dried in a vacuum oven at 80° C. for 24 hours to obtain the final sample.

)，2θ在10-80°范围。用电子散射能谱(EDS)分析其组成。产物样品还使用JSM-5510LV型场发射扫描电子显微镜(SEM)观察形貌，其制样方法是直接采用产物粉末分布在双面胶上并粘在样品铜台上喷金后观察。FTIR分析采用Impact420型红外光谱仪，X-射线能谱分析采用FALCON型X-射线能谱仪(C为内标)。Gained product sample X-ray diffraction analysis uses XD-5A type X-ray powder diffractometer (30kv, 20mA, λ=1.5406

), 2θ is in the range of 10-80°. Its composition was analyzed by electron scattering spectroscopy (EDS). The morphology of the product samples was also observed using a JSM-5510LV field emission scanning electron microscope (SEM). The sample preparation method was to directly use the product powder to distribute on the double-sided adhesive tape and stick it on the copper platform of the sample to spray gold for observation. FTIR analysis adopts Impact420 infrared spectrometer, and X-ray energy spectrum analysis adopts FALCON type X-ray energy spectrometer (C is internal standard).

The present invention utilizes a chemical synthesis method to react at low temperature to obtain _MgSiN2 ceramic material, which is a new method for preparing _MgSiN2 ceramic powder, and it is easy to prepare alkaline earth metal silicon nitride ceramic powder with _NaN3 as the N source. Including four reaction routes for preparing MgSiN ₂ powder, MgSiN ₂ can be easily prepared by using pre-sintered Mg ₂ Si, [Mg ₂ Si], Mg+Si, SiO ₂ +Mg four silicon-magnesium systems respectively. Different Si—Mg reaction systems have influence on the crystal formation of the product. The pre-sintered and ball-milled Si-Mg system is easier to prepare MgSiN ₂ than the other two Si-Mg reaction systems, and the crystallinity of the sample is better. Within a certain temperature range, as the temperature increases, the grain growth of the prepared MgSiN ₂ samples is better.

Compared with the prior art, the present invention has the following advantages: 1) the synthesis route of magnesium silicon nitride is carried out simultaneously with the growth of submicron polycrystals, and since _NaN is used as the nitrogen source, it is also a polycrystal growth medium itself, which not only realizes Mild reaction conditions, the preparation process is also relatively simple, especially the preparation temperature is greatly reduced, thereby greatly reducing energy consumption; 2) The product MgSiN ₂ ceramic powder has irregular morphology, sub-micron particle size, and relatively uniform distribution , The crystallization degree of the product is relatively good, the purity is high, and the size is uniform.

Description of drawings

Figure 1 is the XRD spectrum of the product magnesium silicon nitride: [Mg ₂ Si]+NaN ₃ , 600°C-12 hours.

Figure 2 is the SEM photograph of the product magnesium silicon nitride: [Mg ₂ Si]+NaN ₃ , 600°C-12 hours.

Figure 3 is the EDS spectrum of the product magnesium silicon nitride: [Mg ₂ Si]+NaN ₃ , 600°C-12 hours.

Figure 4 is the FTIR spectrum of the product magnesium silicon nitride: a-Mg+Si+NaN ₃ , 500°C-12 hours; b-SiO ₂ +Mg+NaN ₃ , 600°C-12 hours; c-pre-sintered Mg ₂ Si+NaN ₃ , 600°C-12 hours; d-[Mg ₂ Si]+NaN ₃ , 600°C-12 hours.

Detailed ways

The present invention will be further described below in conjunction with the embodiments and accompanying drawings, but it cannot be regarded as a limitation of the present invention.

Example 1

Take 2.65 grams of [Mg ₂ Si] and 4.50 grams of NaN ₃ (Si:Mg:NaN ₃ =1:2:1.98) into a stainless steel reaction kettle with a volume of 20ml, tighten the lid of the reaction kettle, seal it and put it into the well In a crucible boiler, react at a constant temperature of 600°C for 6 hours. After natural cooling, the product is washed with absolute ethanol, dilute hydrochloric acid (0.1M) and distilled water for 5-20 minutes in order to remove alkali metals and their oxides, soluble by-products, etc. Impurities were separated by centrifugation and dried in a vacuum oven at 80° C. for 24 hours to obtain 2.13 g of off-white powder. After analyzing the structure, microstructure, composition and appearance, it is proved that the product is relatively pure random orthorhombic silicon magnesium nitride polycrystalline powder, and its appearance and size are shown in Figure 2.

Example 2

Take 2.82 grams of SiO ₂ , 3.07 grams of Mg and 3.18 grams of NaN ₃ (Si:Mg:NaN ₃ =1:2.72:1.04) into a stainless steel reaction kettle with a volume of 20ml, tighten the lid of the reaction kettle, seal it and put it into the well In a type crucible boiler, react at a constant temperature of 500°C for 12 hours. After natural cooling, the product is washed with absolute ethanol, dilute hydrochloric acid (0.1M) and distilled water for 5-20 minutes in order to remove alkali metals and their oxides and soluble by-products. After centrifugation, the mixture was dried in a vacuum oven at 80° C. for 24 hours to obtain 2.04 g of off-white powder. After structure, microstructure, composition and morphology analysis, it is proved that the product is relatively pure random orthorhombic silicon magnesium nitride polycrystalline powder.

Example 3

Take 0.90 g of Si, 0.86 g of Mg and 3.00 g of NaN ₃ (Si: Mg: NaN3 = 1: 1.11: 1.44) into a stainless steel reactor with a volume of 20 ml, tighten the lid of the reactor, seal it and put it into a well-type crucible In the boiler, react at a constant temperature of 600°C for 12 hours. After natural cooling, the product is ultrasonically washed with absolute ethanol, dilute hydrochloric acid (0.1M) and distilled water for 5-20 minutes to remove impurities such as alkali metals and their oxides, soluble by-products, etc. , and dried in a vacuum oven at 80° C. for 24 hours after centrifugation to obtain 2.43 g of off-white powder. After structure, microstructure, composition and morphology analysis, it is proved that the product is relatively pure random orthorhombic silicon magnesium nitride polycrystalline powder.

Example 4

Take 1.20 grams of pre-sintered Mg ₂ Si and 3.31 grams of NaN ₃ (Si:Mg:NaN ₃ =1:2:1.98) into a stainless steel reaction kettle with a volume of 20ml, tighten the lid of the reaction kettle, seal it and put it into the well In a type crucible boiler, react at a constant temperature of 450°C for 12 hours. After natural cooling, the product is washed with absolute ethanol, dilute nitric acid (0.1M) and distilled water for 5-20 minutes in order to remove alkali metals and their oxides and soluble by-products. After centrifugation and separation of impurities, the mixture was dried in a vacuum oven at 80° C. for 24 hours to obtain 0.97 g of off-white powder. After structure, microstructure, composition and morphology analysis, it is proved that the product is relatively pure random orthorhombic silicon magnesium nitride polycrystalline powder.

Table 1 is the comparison between XRD data of the product magnesium silicon nitride and JCPDF card #52-0797 standard card data.

Accompanying drawing 1 has provided the XRD spectrogram of sample, accords with JCPDF card #52-0797, and attached table 1 compares product silicon nitride magnesium XRD data and JCPDF card #52-0797 standard card data, and the results show that the obtained The final product is magnesium silicon nitride.

Accompanying drawing 2 is the SEM spectrogram of the sample, has demonstrated product shape and size, and the result shows, the polycrystalline powder of magnesium silicon nitride obtained is irregular, and its average particle size is about 200nm.

Accompanying drawing 3 is the X-ray energy spectrogram of the product sample, as can be seen from the figure, the peaks of the binding energy at 390.4eV, 1304.1eV and 1840.2eV are respectively corresponding to N1s, Mgls, Sils, indicating that the sample surface contains Mg, Si , N. As shown in Figure 2b, the atomic percentages of Mg, Si, and N in the sample, the atomic ratio Mg:Si:N is 1:1.50:0.89, which is different from the theoretical ratio (1:1:2), which is mainly due to the The components are not uniformly distributed and can only measure information within 5nm of the sample surface. In addition, the figure also contains a small amount of Au, C, O, Cu and other components, C is the internal standard, O is caused by the surface adsorption of the sample, Au is the reason for spraying gold in the test, and the sample is placed on the copper grid to measure and bring Cu .

As shown in Figure 4, Mg/Si/NaN ₃ , 500°C-12 hours; SiO ₂ /Mg/NaN ₃ , 600°C-12 hours; pre-sintered Mg ₂ Si/NaN3, 600°C-12 hours; [Mg ₂ Si]/NaN3, FTIR spectra of samples prepared under four conditions of 600°C-12 hours. The absorption band around 1380cm ^-1 should be the stretching vibration of N—N bond, the absorption band around 920cm ^-1 should be the stretching vibration of N—Si bond, and the absorption band around 1080cm ^-1 should be Si—O bond The stretching vibration of the N—H bond should be the absorption band around 1640cm ^-1 , and the peak around 3440cm ^-1 is the absorption peak of water molecules. The existence of water molecules is due to incomplete drying or the adsorption of water vapor in the air on the surface of the sample, and the existence of Si—O and N—H is due to the hydrolysis of the sample during the washing process. The absorption peaks at 970, 880, 740, 620, 540, and 520 cm ^-1 in the figure may also be the characteristic band position (wavenumber) range of MgSiN ₂ , but its standard infrared band needs further study.

Claims (6)

1. The preparation method of submicron order orthorhombic silicon magnesium nitride polycrystalline ceramic powder is characterized in that carry out heat sealing reaction with Si-Mg precursor and sodium azide, control the Si that participates in reaction: Mg: NaN ₃ =1: 1-2.75:1-3.25, the above is the molar ratio, the heating temperature is 450-600°C, the reaction time is 4-12 hours, the product can be washed and dried to obtain granular irregular submicron orthorhombic nitriding Silicon magnesium polycrystalline ceramic powder. 2. The method for preparing submicron orthorhombic magnesium silicon nitride polycrystalline ceramic powder according to claim 1, characterized in that the heating temperature is 500-550°C. 3. The preparation method of the submicron orthorhombic magnesium silicon nitride polycrystalline ceramic powder according to claim 1, characterized in that the reaction time is 4-6 hours. 4. The preparation method of the submicron-order orthorhombic silicon magnesium nitride polycrystalline ceramic powder according to any one of claims 1-3, characterized in that the Si-Mg precursor is SiO ₂ +Mg, Si+ Mg and pre-sintered Mg ₂ Si. 5. the preparation method of submicron order orthorhombic silicon magnesium nitride polycrystalline ceramic powder according to claim 4, it is characterized in that the pre-sintered Mg ₂ Si refers to Si powder and Mg powder according to molar ratio Si: Mg is 1 : 2 weighed, mixed, and sintered at 700°C for 48 hours. 6. The method for preparing submicron orthorhombic silicon magnesium nitride polycrystalline ceramic powder according to claim 1, characterized in that the particle size of the submicron orthorhombic silicon magnesium nitride polycrystalline ceramic powder is 100-450nm.

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