회사 소식 Why Low Porosity Improves Sagger Reliability？

In lithium battery material production, saggers operate under a combination of:

• high temperature,
• repeated thermal cycling,
• alkaline vapor exposure,
• powder loading stress,
• and long-term oxidation.

Under these conditions, many failures that appear to be “thermal shock problems" are actually closely related to one fundamental material characteristic:

In practical kiln operation, saggers with higher porosity often show:

• faster surface degradation,
• powder infiltration,
• corner cracking,
• bottom weakening,
• and shorter service life.

This case study explains why low porosity is one of the key factors determining long-term sagger reliability.

Porosity refers to the amount of microscopic voids inside the ceramic structure.

In silicon carbide ceramics, pores can become pathways for:

• gas penetration,
• alkaline vapor attack,
• molten phase infiltration,
• oxidation,
• and crack propagation.

Even when pores are not visible from the surface, internal interconnected porosity can significantly influence long-term durability.

For kiln furniture applications, the difference between:

• open porosity,
• closed porosity,
• and near-zero porosity

often determines whether the structure remains stable after hundreds of thermal cycles.

In cathode material production, especially in high-nickel systems, the kiln atmosphere may contain:

• lithium compounds,
• alkaline vapor,
• transition metal oxides,
• and corrosive reaction products.

Porous structures allow these substances to penetrate deeper into the ceramic body.

As penetration depth increases:

• grain boundaries weaken,
• oxidation accelerates,
• local expansion mismatch develops,
• and microcracks initiate internally.

This type of degradation is often progressive and difficult to detect during early stages.

Pores act as natural stress concentrators.

During heating and cooling:

• local temperature gradients develop around pore regions,
• thermal expansion becomes non-uniform,
• and tensile stress accumulates at weak points.

Under repeated thermal cycling, these localized stresses can evolve into:

• edge chipping,
• corner cracks,
• bottom cracking,
• or structural deformation.

The problem becomes more severe in large-size saggers and fast-cooling kilns.

At elevated temperatures, porous structures generally show:

• lower stiffness,
• reduced load-bearing capability,
• and faster creep deformation.

In long-term operation, this may lead to:

• bottom sagging,
• wall distortion,
• uneven powder distribution,
• or instability during stacking.

Even small deformation can alter stress distribution and accelerate failure propagation.

Low-porosity silicon carbide provides a denser microstructure.

This significantly reduces:

• vapor penetration,
• molten phase infiltration,
• and internal oxidation.

As a result:

• chemical attack remains closer to the surface,
• internal structure remains stable,
• and crack propagation slows down.

Dense structures distribute thermal stress more uniformly.

Compared with porous materials, low-porosity ceramics typically show:

• lower local stress concentration,
• reduced microcrack initiation,
• and improved thermal fatigue resistance.

This is especially important during:

• rapid cooling,
• shutdown cycles,
• and repeated start-stop kiln operation.

Low porosity also improves:

• stiffness retention,
• creep resistance,
• and structural integrity at high temperature.

For battery material production, this contributes to:

• more stable geometry,
• consistent stacking behavior,
• and longer operational lifetime.

High-nickel cathode materials create a more aggressive kiln environment than conventional LFP systems.

In these applications, porous saggers may experience:

• accelerated lithium penetration,
• stronger alkaline attack,
• rapid surface degradation,
• and severe edge damage.

Dense pressureless sintered silicon carbide (SSiC) is often preferred because its extremely low open porosity helps minimize these degradation mechanisms.

This becomes increasingly important as:

• firing temperatures increase,
• cycle frequency rises,
• and energy efficiency requirements become stricter.

In many practical cases, sagger failure is not caused by a single overload event.

Instead, reliability gradually decreases due to:

• chemical penetration,
• oxidation,
• thermal cycling,
• and stress accumulation.

Porosity directly influences all of these mechanisms.

For this reason, low porosity should not be viewed only as a material specification.

It is a key engineering factor affecting:

• thermal reliability,
• corrosion resistance,
• structural stability,
• and service life.

Low porosity plays a critical role in improving sagger reliability under demanding kiln conditions.

A denser silicon carbide structure helps reduce:

• chemical penetration,
• thermal stress concentration,
• oxidation damage,
• and long-term deformation.

For high-temperature battery material production, especially in high-nickel cathode applications, low-porosity pressureless sintered silicon carbide provides important advantages in long-term operational stability and durability.

Shaanxi Kegu New Material Technology Co., Ltd. specializes in pressureless sintered silicon carbide (SSiC) components for demanding high-temperature applications, including kiln furniture, rollers, beams, and saggers used in lithium battery material production.