What is Niobium
Niobium (chemical symbol is Nb) is a transition metal element. Niobium is a lustrous gray metal. High-purity niobium metal is highly ductile, but it hardens with increasing impurity content. Niobium has a wide range of applications in the nuclear industry.
| I | O | |||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 1 H |
II | III | IV | V | VI | VII | 2 He |
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| 2 | 3 Li |
4 Be |
5 B |
6 C |
7 N |
8 O |
9 F |
10 Ne |
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| 3 | 11 Na |
12 Mg |
III | IV | V | VI | VII | VIII | I | II | 13 Al |
14 Si |
15 P |
16 S |
17 Cl |
18 Ar |
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| 4 | 19 K |
20 Ca |
21 Sc |
22 Ti |
23 V |
24 Cr |
25 Mn |
26 Fe |
27 Co |
28 Ni |
29 Cu |
30 Zn |
31 Ga |
32 Gc |
33 As |
34 Se |
35 Br |
36 Kr |
| 5 | 37 Rb |
38 Sr |
39 Y |
40 Zr |
41 Nb |
42 Mo |
43 Tc |
44 Ru |
45 Rh |
46 Pd |
47 Ag |
48 Cd |
49 In |
50 Sn |
51 Sb |
52 Te |
53 I |
54 Xe |
| 6 | 55 Cs |
56 Ba |
57-71 La-Lu |
72 Hf |
73 Ta |
74 W |
75 Re |
76 Os |
77 Ir |
78 Pt |
79 Au |
80 Hg |
81 Tl |
82 Pb |
83 Bi |
84 Po |
85 At |
86 Rn |
| 7 | 87 Fr |
88 Ra |
89-103 Ac-Lr |
104 Rf |
105 Db |
106 Sg |
107 Bh |
108 Hs |
109 Mt |
110 Ds |
111 Rg |
112 Uub |
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| La-Lu | 57 La |
58 Ce |
59 Pr |
60 Nd |
61 Pm |
62 Sm |
63 Eu |
64 Gd |
65 Tb |
66 Dy |
67 Ho |
68 Er |
69 Tm |
70 Yb |
71 Lu |
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| Ac-Lr | 89 Ac |
90 Th |
91 Pa |
92 U |
93 Np |
94 Pu |
95 Am |
96 Cm |
97 Bk |
98 Cf |
99 Es |
100 Fm |
101 Md |
102 No |
103 Lr |
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- Item Name: Niobium
- Element Symbol: Nb
- Atomic Number: 41
- Atomic Weight: 92.91
- Atomic Radius: 143pm
- Density: 8.57g/cm3
- Melting Point: 2468°C
- Boiling Point: 4742°C
- Electronic Layout: [Kr]4d45s1
The Atomic Structure of Niobium
Physical Properties
Niobium has a high melting point (2468°C) in its elemental state, and is a refractory metal. At the same time, its density is lower than other refractory metals.
Niobium exhibits superconducting properties at low temperatures. At standard atmospheric pressure, its critical temperature is the highest among all elemental superconductors. It also has the highest magnetic penetration depth of any element. The purity of niobium greatly affects its superconducting properties.
Chemical Properties
Niobium metal is very stable in air at room temperature and will not be fully oxidized when heated in oxygen. Niobium also resists various erosions and forms a dielectric oxide layer. Niobium does not interact with inorganic acids or bases, but it is soluble in hydrofluoric acid. Niobium combines with sulfur, nitrogen, and carbon at high temperature.
The chemical properties of niobium are very similar to those of tantalum. Although it is not as corrosion resistant as tantalum, it is less expensive and more common. Therefore, it is often used to replace tantalum in the case of lower requirements (for example, as a coating material for chemical tanks in chemical plants).
Solid Solution Strengthening Effect of Niobium
Niobium is one of the commonly used solid solution strengthening elements. Niobium atoms have a larger radius than tungsten and molybdenum, and are 15% to 18% larger than nickel, cobalt, and iron atoms. Therefore, the solid solution strengthening effect of niobium is greater than that of tungsten and molybdenum. Inconel 625 is a typical solid solution strengthened alloy using niobium.
625
Si
C
Al
Ti
Co
Ta
Mo
Fe
Cr
Ni
The solid solution strengthening effect of niobium can also significantly improve the creep properties of the alloy. The higher the niobium content, the more obvious the effect. At the same time, niobium can also reduce the average grain size of the alloy, which will further improve the creep resistance of the alloy. However, too much niobium will cause the precipitation of Laves phase, which will have a certain effect on the properties of the alloy.
However, for precipitation strengthened superalloys, only 10% of niobium acts as solid solution strengthening.
Precipitation Strengthening Effect of Niobium
In precipitation strengthened superalloys, 90% of niobium plays a role in precipitation strengthening.
Some of the niobium added to these superalloys will combine with nickel, aluminum and titanium to form Ni3(Al, Ti, Nb). During this process, niobium atoms occupy the positions of some aluminum and titanium atoms in the γ' phase, and these aluminum and titanium atoms will again form a new γ' phase. At the same time, niobium also reduces the solubility of aluminum and titanium in the alloy. This increases the number of γ' phases and increases the degree of order, resulting in enhanced precipitation strengthening of γ' phases. The yield strength of the alloy will be significantly improved, and the permanent creep properties of the alloy will also be significantly improved.
In addition, niobium not only enters the γ' phase, but also generates a γ" phase (NixNb). The γ" phase is an ordered body-centered tetragonal structure, which also plays a good role in precipitation strengthening. The γ" phase is the main strengthening phase of Inconel 718 alloy, and its effect exceeds the γ' phase. The sum of the amount of the γ' phase and the γ" phase in the alloy is 15% to 20%.
718
Si
C
Al
Ti
Co
Nb
Ta
Mo
Fe
Cr
Ni
Conclusion
Niobium has a very large atomic radius. It is also a refractory metal. This property makes it an effective solid solution strengthening element.
In precipitation strengthening alloys, niobium mainly plays the role of precipitation strengthening. And it acts on both the γ' phase and the γ" phase.
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