Magnesium nitride, the chemical formula of which is Mg3N2 is basically a mixture of magnesium and nitrogen which is usually found in a powdered form specifically in green and yellow colors. It has various properties all of which are rich in their own characteristics.

It is basically the properties of anything that decide on what position that specific item holds in the industry and market. This is exactly why magnesium nitride is rich in its applications too as it has various applications all of which are listed and explained in this article. These are known throughout the market because of the excellent nature that they hold in each and every characteristic.

Introduction

Being nitrogen and magnesium’s inorganic compound, magnesium nitride has the chemical formula Mg3N2. Magnesium nitride is a greenish-yellow powder at room temperature. Magnesium nitride ceramic powder’s molecular weight is 100.93, it has a relative density of 2.71 (25/4oC), its decomposition point is 800oC, and it has a hexagonal crystal system. In ether and ethanol, the compound is slightly soluble whereas it dissolves in acid. This compound decomposes into magnesium hydroxide in water or moist air and releases ammonia. In other nitride compound formations, magnesium nitride ceramic powder is capable of being utilized as it has wear resistance, corrosion resistance, high-temperature resistance, high thermal conductivity, and high hardness characteristics.

Magnesium nitride ceramic powder can be utilized for the making of special alloy blowing agents and of special ceramic material. It is also utilized for producing special glass and catalyzed polymer cross-linked. It is also used for synthesizing cubic boron nitride crystals, and synthetic diamonds and for making steel smelting additives of high strength. Being a bandwidth of 2.8 eV direct bandgap semiconductor, magnesium nitride has a potential application value in the formation of light-emitting diodes. Magnesium nitride micron powder has an almost 1500 C melting point and greenish-yellow color. Magnesium nitride is made by passing ammonia or dry nitrogen over heated magnesium.

Properties Mg3N2

Magnesium nitride has a melting point of 1500 C. Above 1500 C temperature, magnesium nitride decomposes for producing nitrogen gas. It is a pale yellow powder with a density of 2.71 g mL-1. In water, it is freely soluble, whereas, in ammonia, methanol, and ethanol, magnesium nitride is reasonably soluble.

Chemical properties

Magnesium nitride is very beneficial and useful in synthesizing new materials as it is a ceramic with the characteristics like corrosion resistance, high thermal conductivity, and high hardness. Magnesium nitride is sometimes utilized in making other metallic nitrides and it forms alloys with other ceramics in order to form special materials.

Reactivity of Mg3N2 upon Air Exposure

Under ambient conditions, the capping layer of MgO, Mg3N2 decomposes on reaction with water, resulting in the production of magnesium hydroxides (mostly), oxynitrides, and oxides. Commercial Mg3N2 powder of 44 μm nominal particle size was purchased for quantifying the speed at which decomposition occurs, which the scanning electron microscopy (SEM) confirmed, the measurements disclosing the size of the particles on the same scale. As a test, Mg3N2 powder is kept under ambient conditions. Firstly, the powder's color is yellowish but after reacting with air, it faces a drastic increase in volume and turns totally white. The powder starts decomposing after being exposed to air for one hour. Despite no visible XRD signal from Mg (OH) 2, the Mg3N2 peaks’ intensity has already decreased. Initially, the micrometric particle’s surface decomposes and on spreading of the reaction, a signal from the magnesium hydroxide phase is detected, ending up after 24 hours by dominating the XRD pattern.

Quantitative Assessment

The peak areas of the four functions were evaluated as a function of time for assessing the Mg3N2 powder’s decomposition kinetics, quantitatively. A meantime constant was obtained by using an exponential fit for the peak areas, averaged over all four reflections, of τ decomposition in optimum conditions. The thin films of 100 nm thicknesses exhibit a more surface-to-column ratio as compared to the microparticles of a diameter of 44 μm. Their rate of decomposition is maybe more than the powder’s rate of decomposition. Therefore, a capping layer is developed for being deposited in the MBE reactor before the Mg3N2 films are removed and exposed to air as that development is very much needed. MgO looks like an appropriate candidate because of its high chemical stability and ionic Mg-O bond nature (10.33 eV cohesive energy), although MgO feels counterintuitive because of oxygen’s presence in the compound. MgO cap’s oxygen doesn’t react with the underlying Mg3N2, but it is important to make sure that the capping's quality and its compactness can prevent contact between the ambient moisture and the film.

Optimization Parameter

Therefore, the roughness of the surface is chosen to be the optimization parameter for the MgO cap. In the same reactor on MgO substrates, MgO thin films were homoepitaxially grown. For eliminating any scratch/polishing residue from their surface and promoting the production of terraces that are automatically flat, the substrates were annealed ex-situ at high temperatures before growth. AFM analyzed a complete series of samples, displaying the evolution of roughness as oxygen flow and growth temperature's function. The surface shows cubic grains with 100 nm of weight and height at low oxygen flow and low substrate temperature but displays the substrate’s incomplete wetting, making it unacceptable to be used currently. The growth of MgO is slowed down or maybe eventually prevented by an increase in the flow of oxygen at intermediate temperatures, with the nucleation randomly occurring on the substrate and resulting in separated agglomerates.

Process of Nucleation

Nucleation takes place along the atomic steps present on the annealed substrate at the large oxygen flow (0.40 sccm) and highest substrate temperature (~650 °C). With a base of 40 nm, a cubic shape is also possessed by the MgO crystallites. At 0.35 sccm oxygen flow and 580 C temperatures, the substrate’s roughness is the series’ lowest (1.4 nm) and the surface of the substrate is totally wetted. The MgO film contains the square grains with 40 nm of lateral sizes and heights between 1-5 nm above the mean surface for these optimized conditions. Under these growth conditions, XRR measured the MgO growth rate of 63 nm/h on a MgO/CdO multilayer structure. Later, the MgO cap of 50 nm (grown under the optimized conditions) thickness covered all the Mg3N2 films.

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Mg3N2 Epitaxial Growth: Crystal Orientation Tunability

At the smallest Mg/N ratio and 400 °C temperature, the direction of growth is remarkable and parallel, consistent with a study that’s done recently reporting the first attempts for growing the single-crystal Mg3N2 films. A shoulder on the MgO substrate peak’s lower side occurs under these growth conditions, which might be attributed to the formation of MgON at the substrate/layer interface.

The Nitrogen Flow

The orientation is maintained as the flow of nitrogen diminishes, but the parasitic MgON phase totally disappears. The grains appear to further reduce the flow of nitrogen, these grains are oriented parallel, arising polycrystalline thin films showing concomitantly and grains. A further increase in the temperature of Mg cell and reduction of the flow of nitrogen leads to the Mg3N2 films showing one single orientation again.

The spotty RHEED pattern can be modeled with diffraction from crystallographic planes’ three families, as the colored dots represent in Inset (E). There is also discussion on the exact epitaxial relationships giving birth to such diffraction patterns. If the growth temperature is increased under these last conditions of growth, a streaky RHEED pattern corresponding to a flat surface (Inset (F) is recovered. Tuning Mg3N2 growth orientation on MgO is therefore possible by switching from N-rich to the growth conditions that are more Mg-rich. Mg3N2 films growth rate is plotted as Mg cell temperature’s function for 0.35 sccm flow of nitrogen, the growth rate is also accelerated by an increase of Mg flux.

The Growth Conditions

This aspect should be kept in mind as it is significant, same as the other nitrides that are grown by the plasma-assisted MBE (for example, AIN or GaN), the real growth rates are low (in 2 nm/min order for optimized growth conditions). 2.6 nm/min is the maximum growth rate achieved (equivalently, 312 nm/h), but demands large Mg flux and N flow or/and low temperatures, far from the optimum growth conditions for obtaining high-quality thin films. The growth rate’s increase up to a 420-430 C temperature of Mg cell leads to a growth regime that the Mg incorporation limited (for instance, N-rich). Meanwhile, the growth rate’s saturation at temperatures more than 420-430 C temperature of the Mg cell leads to an excess of Mg, for instance, in Mg-rich conditions.

The Role of the MgO Cap

The MgO cap’s 1:1 stoichiometry was monitored by XPS measurements, along with the underlying Mg3N2 thin film’s presence, which was measured because of in-situ etching. Although, any quantitative analysis of the Mg3N2 stoichiometry is prevented by the oxygen's presence in the capping layer. The reason for this prevention is that this cap must be eroded in-situ in the XPS chamber and, therefore, when analyzing the underlying Mg3N2 film, a non-negligible background oxygen partial pressure is always present in the chamber and can be oxidized. In time this effect can be monitored. When the Mg3N2 is being eroded, the concentration of oxygen is detected to be slowly increasing as a function of the time passed between the MgO’s measurement and the erosion. XRR was systematically employed for assessing the abruptness of the MgO(cap)/Mg3N2(film) interface. A typical X-ray reflectivity curve is seen, measured on sample F from the series discussed above, showing neat interference fringes.

Properties of the MgO Cap

If GenX software is being used, then the fitting of the curve indicates 98 nm thickness of Mg3N2 and 42 nm thickness of MgO cap. In addition, there is no interfacial layer indication between the two films and there is 1nm roughness of Mg3N2, which is consistent with the observation of a streaky RHEED pattern measured at the end of the growth of Mg3N2. Despite such discrepancies that take place in XRR measurements, those discrepancies also point toward the existence of grain boundaries and a large vacancy density.

Linear Thermal Expansion Coefficients of Epitaxial

For most materials, epitaxy takes place at higher temperatures than room temperature, so for quantitatively analyzing the lattice mismatch at actual growth temperature between the substrate and thin film, having the know-how of their linear thermal expansion coefficient is important. After analysis, the heterostructures design can be enabled, sustaining the pseudomorphic growth or, maximizing the film’s initial strain for favoring fast plastic relaxation. Also, various basic physical characteristics can be influenced by the thermal expansion coefficient as soon as the temperature variations start coming into play.

The thermal expansion coefficient can specifically play a significant role in determining the material band gap’s temperature dependence. The out-of-plane lattice parameters are measured for assessing the linear thermal expansion coefficient αT of the MgO substrate and also of the Mg3N2 epitaxial films, as a temperature function in the 300 K- 1100 K temperature range. Silicon’s thermal expansion coefficient can be precisely measured by the methodology that Liu and Zheng introduced, and that way we will also reduce the systematic errors.

Bandgap of Epitaxial Mg3N2

For measuring the epitaxial Mg3N2 films’ optical bandgap and determining its temperature dependence, the transmission measurements were taken from low (~10 K) to room temperature and the absorption coefficient (α) was extracted therefrom. Also, in order to compare with the previously carried out measurements on the powder samples of Mg3N2, the diffuse reflectance was also measured as temperature’s function on the same micrometric Mg3N2 particles that were employed for analyzing Mg3N2’s chemical reactivity in ambient conditions.

At low temperatures, a 2.95 eV bandgap can be estimated, and when the temperature is increased to 300K, it decreases down to 2.88 eV. These measurements give values similar to the previous measurements that were obtained from the Mg3N2 powder samples, and represented by dots, and also with the measurements on the commercial Mg3N2 microparticles, which were represented by triangles.

According to the Varshni Formula

For various semiconductors, the bandgap’s measured temperature dependence can be fitted by the Varshni formula. The energy bandgap’s temperature dependence can also be described by the more physically-meaningful model that the K develops. O’Donnell et al. consider the electron-phonon coupling and the states’ photon density is taken into account. The three parameters which define each of the models for a typical Mg3N2 film and for the commercial Mg3N2 powder have been explained.

Applications of Magnesium Nitride Micron Powder

The usage of magnesium nitride is broad. In the silicon nitride’s and boron nitride ceramics’ solid reaction, magnesium nitride is an indispensable sintering assistant with high-temperature resistance, corrosion resistance, wear resistance, high thermal conductivity, and high hardness. In nuclear fuel’s recovery, magnesium alloy melt’s purification, and hBN reaction’s catalysis, a significant role is played by magnesium nitride. In addition, Mg3N2 as an additive can effectively desulfurize and increase alum, so as to improve the density, strength, tensile force, and bearing capacity of steel.

It has a wide range of applications; Magnesium nitride can be used as:

1. Synthesize other elements' nitride with high-temperature resistance, wear resistance, corrosion resistance, high thermal conductivity, and high hardness.

2. Prepare special ceramic materials

3. Foaming agent for making special alloy

4. Used for making special glass

5. Catalytic polymer crosslinking

6. Recycling of nuclear waste

7. Catalysts for synthetic diamond and cubic boron nitride

8. Additives for high strength steel smelting, etc

9. Magnesium nitride Mg3N2.(Vacuum package)

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Uses of Mg3N2 as an Additive

Nitride magnesium (Mg3N2) alternative construction in steel smelting magnesium desulfurization, favorable to improve the density of steel tensile strength and endurance, increase material internal alum (Vitriol) content, reached the standard of the Chinese government put forward the quality construction of steel using magnesium nitride (Mg3N2) desulfurization, can reduce other additives, which helps to reduce the production cost of construction steel in our country is now in the products of a steel factory, the average cost per ton lower RMB 300-450 yuan ($36.3-54.5) application:

1.Magnesium and magnesium alloy

In applications of engineering, it is the lightest metal structure material. The deformation of the plastic forming technology of magnesium alloys in recent years has become the world's magnesium industry important research field of magnesium alloy in the future of the energy shortage will occupy a more important position at present, magnesium alloy in aerospace automobile electronics building industry and daily life is indispensable important material but magnesium alloy in the widely used at the same time it still has its weakness, such as low hardness, strength, and melting point is lower than common metals such as steel how to improve the ability of plastic forming of magnesium alloy has become the research of magnesium alloys.

Hot, therefore, seeking a good hardness, and strength, but also has high specific strength and specific stiffness, has essential academic and industrial application value in recent years, along with the development of high-end mechanical and electrical products production requirements, on the mechanical properties of magnesium alloy to need to further improve, with particulate reinforced magnesium matrix alloy material can exert magnesium alloy matrix at the same time and enhance the benefit of phase, significantly enhance the strength of the magnesium alloy with an elastic modulus of hardness and wear resistance and particulate reinforced magnesium matrix alloy material because of its low cost, strength.

2. The factor of rigidity

Rigidity is high, in the field of modern industrial production, such as advanced manufacturing, have broad application prospects based on the above purpose, using non-toxic pollution-free is added in the magnesium alloy magnesium - nitride nanotubes particles to enhance the strength of the magnesium alloy materials, good toughness and hardness, at the same time, to effectively improve conductive and heat conduction performance of magnesium alloy substrate material chemical composition and quality score is: magnesium Mg: 90-98, the remaining ingredients for aluminium Al for patent, to improve the performance of magnesium alloy in our country's existing magnesium alloy by adding indium scandium Yttrium and other precious metals and 2-3% of rare earth metals, smelting finished sample grain size less than or equal to 3 microns, the invention adds more precious metal elements content = high, high manufacturing costs select capable of improving the Mg alloy amorphous formation (Er, Cu, Ag) as alloying elements, selects the common casting and hot extrusion method preparation of the alloy material, and after casting and extrusion for magnesium alloy with the above alloys have the rare metal addition, although can improve ductility of magnesium alloy materials.

3. Factors of Hardness and Abrasion

Hardness and abrasion resistance, but increased the magnesium alloy smelting cost, at the same time, to achieve higher strength and abrasion resistance proposes a processing process stable low-cost non-polluting emissions can be under the condition of conventional smelting production of magnesium - nitride carbon nanotubes preparation of particulate reinforced magnesium matrix alloy, magnesium alloy material with a more traditional strength toughness of hardness and wear resistance increased greatly, therefore, by adding magnesium - nitride carbon nanotubes particle reaction enhancement purpose to the mechanical properties of magnesium alloy materials.

Conclusion

Mg3N2 is undoubtedly one of the most important and useful alloys of magnesium as its uses are so vast that they can be seen in almost every field. The properties that they hold help them in giving them a prominent place in the market. After all the research and work that has been done in this regard, the importance and necessity of magnesium nitride have been proved to be quite evident throughout the world including in markets and industries.

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References

https://www.jzhaixin.com/magnesium-nitride-powder-mg3n2-product/

https://www.softschools.com/formulas/chemistry/magnesium_nitride_formula/660/

https://hal.archives-ouvertes.fr/hal-03045516/document

https://www.us-nano.com/inc/sdetail/12149