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Overview of Magnesia crucibles
Magnesium Oxide (MgO) crucibles have a fine-grained structure with low open porosity. The density is 3.45 g/cm3 with less than 1 % open porosity.
This material contains 2 % Yttrium Oxide (Y2O3) to facilitate the sintering of Magnesium oxide. Yttrium Oxide is completely inert and behaves similarly to MgO in all applications.
Magnesia crucibleshave a mechanical strength and thermal shock resistance lower than those of Alumina crucibles. They require heating and cooling to be as homogeneous as possible.
They resist up to around 2,000˚C.
MgO Magnesia crucibles possess relatively good mechanical strength but are sensitive to thermal shock. Uniform heating and cooling conditions are necessary to prevent thermal shock-related damage. Maximum heating and cooling rates of 200 °C per hour are recommended, and thermal gradients should be avoided. When used at temperatures exceeding approximately 1,200 °C, limitations in creep resistance should also be considered.
Chemical analysis of Magnesia crucibles
- MgO + Y2O3 99.38 %
- CaO 0.38 %
- SiO2 0.4 %
- Al2O3 0.03 %
- Fe2O3 0.07 %
- B2O3 0.01 %
Benefits of Magnesia crucibles
Magnesia crucibles offer several advantages:
- Better chemical resistance than alumina in certain applications
- Proven alternative to alumina in slag testing
- Operating temperatures exceeding 2,200 °C in specific environments
Applications of Magnesia crucibles
They are used in various fields, including glass industry and metallurgy.
- Processing of molten metal alloys
- Viable alternative to alumina-based ceramics (Al2O3)
- Compatibility with nickel-based alloys
- Proven performance in plutonium and uranium refining
- High-temperature ceramic superconducting materials
- Compatibility with perovskite structure
- Processing of piezoelectric materials
- Resistant to lead-based materials
Technical data of Magnesia crucibles
|
Ext. Diam. (mm) |
H (mm) |
Vol. (cm3) |
Ext. Diam. (mm) |
H (mm) |
Vol. (cm3) |
Ext. Diam. (mm) |
H (mm) |
Vol. (cm3) |
||
|
12.7 |
25.4 |
1 |
38.1 |
76.2 |
63 |
76.2 |
101.6 |
380 |
||
|
18 |
40.6 |
5 |
44.4 |
88.9 |
99 |
76.2 |
146.1 |
547 |
||
|
19.1 |
25.4 |
4 |
50.8 |
50.8 |
75 |
88.9 |
152.4 |
804 |
||
|
25.4 |
25.4 |
7 |
50.8 |
88.9 |
135 |
91.9 |
152.4 |
865 |
||
|
25.4 |
31.8 |
9 |
50.8 |
152.4 |
234 |
95.3 |
152.4 |
932 |
||
|
25.4 |
76.2 |
24 |
57.2 |
88.9 |
176 |
101.6 |
114.3 |
777 |
||
|
31.8 |
31.8 |
16 |
63.5 |
76.2 |
189 |
101.6 |
152.4 |
1,044 |
||
|
31.8 |
50.8 |
46 |
63.5 |
139.7 |
354 |
114.3 |
152.4 |
1,343 |
||
|
31.8 |
63.5 |
56 |
69.9 |
88.9 |
274 |
127 |
203.2 |
2,254 |
Side thickness of 2.5 to 4 mm depending on the crucible diameter.
FAQs that can help you in this category
To help you choose the crucible best suited for your needs Final Advanced Materials considers two criteria: the maximum attainable heating temperature and the material which is to be melted.
Alumina (Al2O3) is the best choice in terms of value for money. It is chemically very inert, and can be used up to 1,700°C.
Zirconia (ZrO2) is more resistant to thermal shock but chemically less stable. Depending on the type of zirconia, it can be used up to 1,800°C.
Magnesia (MgO) is even more inert, and is resistant up to 2,000°C, but it also has the lowest thermal shock resistance.
Graphite, and vitreous carbon, can be used up to 3,000°C in an inert atmosphere or vacuum. However, when used in air these materials oxidise, and can be used only up to approximately 450-500°C.
Final Advanced Materials recommends that you always work in an argon or nitrogen atmosphere, or a vacuum, to optimise use of these materials. In an oxidising atmosphere their use is very limited.
To melt non-ferrous metals and special alloys, Final Advanced Materials recommends the use of graphite or ceramic crucibles.
Graphite and vitreous carbon are recommended for foundry applications due to their excellent thermal conductivity (between 90 and 180 W.m-1.K-1) and their low expansion (between 2 and 5 10-6.K-1). However, these types of crucibles can react with certain oxides and must be used in an inert atmosphere or vacuum.
Alumina (Al2O3) is chemically stable and suitable for less reactive alloys.
Zirconia (ZrO2) has excellent chemical inertia and is suitable for special alloys and reactive materials.
Silicon carbide (SiC) has great thermal conductivity (125 W.m-1.K-1) and low expansion (4.5 10-6.K-1). It is suitable for aluminium, copper and intensive production.
Magnesia (MgO) is resistant to basic environments and nickel-rich alloys.
Silicon carbide (SiC) crucibles have limited oxidisation resistance in an oxygen-rich atmosphere. Silicon carbide starts forming a protective layer of silica (SiO2) at 800-1,000°C. At 1,200°C or above, in air, oxidation becomes more substantial, which can embrittle the crucible over the long term. In these cases, Final Advanced Materials recommends working in an inert atmosphere to prevent these problems from appearing, and to make the material remain stable up to 1,600-1,800°C.
Regarding chemical corrosion, silicon carbide (SiC) has excellent chemical resistance to non-ferrous metals. However, it is sensitive to strong acids and powerful oxidisers at high temperature.
To prevent thermal shock when using ceramic crucibles Final Advanced Materials recommends the following practices:
• control the temperature variations gradually, and limit mechanical stresses
• never heat crucibles, in particular MgO crucibles, at full power from the start (200°C/h)
• prevent thermal gradients, contact with cold surfaces and localised hot spots
• use an inert atmosphere for silicon carbide, graphite or vitreous carbon