Engineering Materials MCQ Questions & Answers | Mechanical Engineering

Refractories are materials that can withstand very high temperatures without melting or breaking down and are commonly used to line furnaces, kilns, and reactors.

Based on their chemical behavior towards slags, fumes, and environments, refractories are classified as acidic, basic, or neutral.

If a refractory contains a high content of silicon or silica (SiO₂), it is termed an acidic refractory. This is because silica reacts with basic oxides (like CaO or MgO) but remains stable in acidic conditions.

Acidic refractories are suitable for environments where the slags and gases are acidic in nature. Common examples include silica bricks and fireclay refractories.

On the other hand, basic refractories contain oxides such as magnesia (MgO) or lime (CaO), and neutral refractories contain materials like alumina or chromite that can resist both acidic and basic slags.

Therefore, when a refractory has a high silicon content, it is classified as an acidic refractory.

Hence, the correct answer is Option A: Acidic.

Ionic bonding is the complete transfer of valence electron(s) between atoms.
It is a type of chemical bond that generates two oppositely charged ions.
In ionic bonds, the metal loses electrons to become a positively charged cation, whereas the nonmetal accepts those electrons to become a negatively charged anion

Ferrites that are used in transformer or electromagnetic cores contain nickel, zinc, and/or manganese compounds.
They have a low coercivity and are called soft ferrites.

Toughness is Property of a material that enables it to absorb and distribute within itself relatively large amounts of energy (both stresses and strains) of repeated impacts and/or shocks, and undergo considerable deformation before fracturing or failing

Crystal structure of a material is, generally, examined by X-ray techniques

Macrostructure of a material is, generally, examined by Naked eye

Structural steel contains Nickel, chromium and manganese

Vanadium is traditionally known for its ability to retard grain growth at elevated temperatures and for its beneficial affinity for carbon and nitrogen.
Vanadium promotes fine grain size, increases hardenability and improves wear resistance through the precipitation of its carbides and nitrides.

Monel metal is an alloy of Nickel and copper

A brass alloy consisting of copper (55%), zinc (41 - 43%) and iron (1 - 3%), with the balance consisting of various other metals.
The proportions used make the material harder and suitable for valves and bearings.