Sintering Relative Density
Compute the relative density of a sintered body, RD = (bulk density/theoretical density)·100%, the fraction of the maximum density (of the fully dense, pore-free material) the piece reached. It is the central measure of the degree of sintering: advanced ceramics aim for RD above 99% (almost pore-free) for maximum strength and properties. The residual porosity is 100% − RD. Enter the bulk (sintered) density and the theoretical density.
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Sintering relative density
In advanced (technical) ceramics — aluminas, zirconias, nitrides and carbides used in implants, cutting tools, armor and electronics — the goal of sintering is to wipe out as much porosity as possible, since every residual pore is a defect that weakens the part. Relative density RD = (bulk density/theoretical density)·100% measures how well that mission went: it compares the density actually reached with the theoretical density (that of the perfectly dense material, with no pores at all — calculated from the crystal structure). An RD of 100% means full densification; the residual porosity is simply 100% − RD. While traditional ceramics (roof tiles, bricks) live comfortably with 10–20% pores, advanced grades demand RD above 99% — sometimes 99.9% — reached through ultrafine powders, isostatic pressing, pressure-assisted sintering (hot pressing, HIP, SPS) and tight process control. Why? Because mechanical strength, transparency (in optical ceramics such as ALON and the translucent zirconia of dental crowns), conductivity and wear resistance all collapse with even a little porosity — an alumina with 5% pores can have half the strength of the fully dense material. RD also guides the study of sintering kinetics: density is tracked as it evolves with time and temperature in order to tune the firing cycle. Enter the bulk density and the theoretical density.
Related Tools
Apparent Porosity (Ceramic)
Compute a ceramic's apparent porosity, AP = (wet mass − dry mass)/(wet mass − immersed mass)·100%, the volume fraction occupied by open pores (accessible to water), measured by Archimedes' method. Unlike water absorption (relative to mass), apparent porosity is relative to volume. Open pores reduce mechanical strength and increase permeability. Enter the wet, dry and immersed masses (hydrostatic weighing).
Bulk Density (Ceramic)
Compute the bulk (apparent) density of a ceramic, BD = dry mass/(wet mass − immersed mass), by Archimedes' method, considering the total piece volume (including pores). It is an indicator of the densification achieved in firing: higher bulk density means fewer pores and generally higher strength. Water density (1 g/cm³) is used in the hydrostatic weighing. Enter the dry, wet and immersed masses.
Firing Shrinkage (Ceramic)
Compute the linear firing shrinkage of a ceramic piece, FS = (L_dry − L_fired)/L_dry·100%, the size reduction during sintering in the kiln, when pores close and particles draw together. It is a critical dimensional-control parameter: porcelain tiles shrink a lot (~7%), while porous ceramics shrink little. Variations in shrinkage cause product miscalibration. Enter the dry and fired lengths.
Water Absorption (Ceramic)
Compute the water absorption of a ceramic piece, WA = (wet mass − dry mass)/dry mass·100%, the amount of water the open pores absorb by immersion. It is the property that classifies ceramic tiles: porcelain (WA ≤ 0.5%, very dense and strong), stoneware, semi-stoneware, semi-porous and porous (wall tile, WA > 10%). The lower the absorption, the more sintered and resistant the piece. Enter the wet mass and the dry mass.
Vitrification Degree (Ceramic)
Estimate the vitrification degree of a ceramic, VD = (1 − WA/WA_green)·100%, comparing the current water absorption with that of the green (non-vitrified) material, as a measure of how much the glassy phase filled the pores during firing. Vitrification — the formation of molten glass that seals the pores — densifies the piece, lowers absorption and raises strength and impermeability. It is what turns porous clay into vitreous porcelain. Enter the current and green water absorptions.
Density-Log Porosity
Compute a reservoir rock's porosity from the density log, φ = (ρma − ρb)/(ρma − ρf), where ρma is the matrix (mineral) density, ρb the bulk density read by the log and ρf the pore-fluid density. It is one of the most used petrophysical methods to estimate porosity in wells, since the bulk density drops as the pore volume (filled by less dense fluid) increases. Enter the matrix, bulk (log) and fluid densities.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.