CLASS 10 Material Preparation Guide

Class 10: Minerals and Rocks

Class 10 includes engineered ceramics such as silicon nitride, zirconia, and alumina, valued for their hardness, thermal stability, and corrosion resistance. These materials are used in high-performance environments—from aerospace and armor to medical implants and microelectronics. Specialized ceramics like AlON (aluminum oxynitride) offer unique properties like optical transparency and extreme hardness, requiring advanced preparation techniques.

Hardness Range
1000–2500 HV
Typical Materials
Si₃N₄, ZrO₂, Al₂O₃, AlON, SiC, B₄C, SiSiC, Mullite, CMCs
Preparation Challenge
CMP Required & Surface Reflectivity

Material Categories

Oxide Ceramics

Examples
  • Alumina (Al₂O₃)
  • Zirconia (ZrO₂)
  • Mullite
Key Features
  • Excellent wear and corrosion resistance
  • Electrical insulation
  • Often used in biomedical and tooling

Non-Oxide Ceramics

Examples
  • Silicon Carbide (SiC)
  • Silicon Nitride (Si₃N₄)
  • Boron Carbide (B₄C)
Key Features
  • High thermal conductivity and strength
  • Used in armor and aerospace
  • More brittle than oxide ceramics

Specialized Ceramics & CMCs

Examples
  • Aluminum Oxynitride (AlON)
  • Silicon-Infiltrated Silicon Carbide (SiSiC)
  • Ceramic Matrix Composites (CMCs)
Considerations
  • Extreme hardness and transparency (AlON)
  • Lightweight with fiber reinforcement (CMCs)
  • Sensitive to preparation-induced microcracking

Preparation Guide

Key Preparation Challenges

Microstructural Damage

Extremely hard materials require precise abrasion control to avoid subsurface damage.

Relief & Contrast

Relief development can obscure grain boundaries and require chemical-mechanical techniques.

Reflectivity

Many ceramics have low natural reflectivity; sputter coating may be needed for clear imaging.

Grain Pull-Out

Grain-boundary fracture and surface defects may result from aggressive polishing or drying.

Recommended Preparation Steps

Sectioning

Use diamond or cubic boron nitride (CBN) cutting with coolant. Avoid fracture from mechanical shock.

Mounting

Use edge-retaining castable resins. Low shrinkage is important for preserving edge integrity.

Grinding

Use rigid grinding systems with diamond abrasives. Apply light pressure and minimize step transitions.

Polishing

CMP with colloidal silica or alumina is recommended. Use soft, low-nap cloths and frequent cleaning.

Quality Verification

Microstructure free from grain pull-out or fracture

Surface is smooth and free from subsurface damage

Reflectivity enhanced via sputter coating if needed

Grain boundaries and inclusions clearly visible