Which of the following will increase the strength of a sample of 90% SiO2 - 10% MgO

Quench the entire sample in water
Quench half of the sample in water
Cool the entire sample with air jets
Cool half the sample with air
Submerge the sample in a salt bath of Na2O
Submerge the sample in a salt bath of CaO

Quench the entire sample in water

Cool the entire sample with air jets
Submerge the sample in a salt bath of CaO

Thanks.

Thanks A

To determine which method will increase the strength of a sample of 90% SiO2 - 10% MgO, we need to understand the effects of each option on the properties of the material.

1. Quenching the entire sample in water refers to rapidly cooling the sample by immersing it in water. This process can cause thermal shock, which can potentially decrease the strength of the material, especially if it has a high thermal expansion coefficient. Therefore, quenching the entire sample in water is unlikely to increase its strength.

2. Similar to quenching the entire sample, quenching half of the sample in water can also lead to a thermal shock. However, since only half of the material is quenched, the thermal stress might be less severe. The strength of the sample could potentially be slightly improved or remain unchanged, but it is unlikely to increase significantly.

3. Cooling the entire sample with air jets involves bringing down the temperature gradually using a controlled flow of air. This method helps to avoid thermal shock and reduces the risk of introducing any stress into the material. Consequently, cooling the entire sample with air jets is a better option than quenching in water, but it may not significantly increase the strength of the material.

4. Cooling only half of the sample with air does not provide a uniform cooling rate throughout the material. This non-uniformity in cooling may result in stress concentrations at the interface between the cooled and uncooled portions. As a result, cooling half the sample with air is not recommended if the goal is to increase its strength.

5. Submerging the sample in a salt bath of Na2O involves exposing the material to a high-temperature environment. This process can cause reactions between the salt and the constituents of the sample, potentially resulting in the formation of new phases or altering the microstructure. While the exact effect depends on the specific composition and conditions, it may not necessarily increase the strength of the material.

6. Submerging the sample in a salt bath of CaO follows a similar principle to the previous option. The reaction between the salt and the sample can lead to changes in the material's microstructure or phase composition. However, like the previous option, it may not directly increase the strength of the material.

In summary, based on the options provided, cooling the entire sample with air jets is the most suitable method for potentially increasing the strength of a sample of 90% SiO2 - 10% MgO.