---
title: "Additive manufacturing plus CVI produces porous SiC gyroids with higher strength and oxidation resistance"
url: https://www.voxelmatters.com/additive-manufacturing-plus-cvi-produces-porous-sic-gyroids-with-higher-strength-and-oxidation-resistance/
date: 2026-02-26
modified: 2026-02-24
lang: en
author: "Davide Sher"
description: "Researchers from the University of Applied Sciences and Arts of Southern Switzerland (SUPSI) and IHI Bernex AG used two 3D printing methods—binder jetting and powder bed fusion—along with chemical vapor..."
categories:
  - "Additive Manufacturing"
  - "AM Research"
  - "Ceramic Additive Manufacturing"
  - "Research & Education"
tags:
  - "future"
image: https://www.voxelmatters.com/wp-content/uploads/2026/02/SUPSI_SiC-study_1771915321330-640x480.jpg
word_count: 582
---

# Additive manufacturing plus CVI produces porous SiC gyroids with higher strength and oxidation resistance

Researchers from the University of Applied Sciences and Arts of Southern Switzerland (SUPSI) and IHI Bernex AG used two 3D printing methods—binder jetting and powder bed fusion—along with chemical vapor infiltration to create porous silicon carbide (SiC) structures shaped like gyroids, which are complex patterns that repeat in three dimensions. The researchers designed cylindrical gyroid samples and adjusted the as-printed dimensions to account for shrinkage so both routes reached a final target size of about 19 mm in diameter and 31 mm in height after thermal processing.

![Uncover the insights from a SUPSI SiC study using binder jetting and powder bed fusion for gyroid SiC structures.](https://www.voxelmatters.com/wp-content/uploads/2026/02/SUPSI_SiC-study_1-s2.0-S0955221925006302-gr13.jpg)For the PBF method, they printed gyroid shapes using polyamide 12 and then made them denser by soaking them in a polymer and heating them, which turned them into a SiOC ceramic structure after heating. In the binder jetting route, parts made from SiC powder were printed with a phenolic binder and then heated, yielding a ceramic preform that did not shrink, unlike the polymer-based route. Both types of preforms were then treated with CVI using methyltrichlorosilane (MTS) in hydrogen at about 1100°C and low pressure, with the 10-hour process split into two parts (2 hours first, then 8 hours) to study time-dependent deposition.

## After CVI

After CVI, both manufacturing methods maintained their overall shape during heating and filling, with CVI adding the most weight and density after the 8-hour period. The reported total mass gain after CVI reached roughly 27% for the PBF+PIP route and 28% for the ceramic binder jetting (CBJ) route. The relative density increased to about 0.721 ± 0.029 for the PBF+PIP method after the second CVI cycle and to about 0.557 ± 0.003 for the binder jetting method after the second cycle, indicating substantial densification but also remaining porosity.

Tests using mercury intrusion porosimetry and SEM imaging showed that CVI reduced pore volume and decreased pore size, but it also created narrow "bottleneck" pores that can block gas flow and prevent complete densification of the core. SEM images identified a compact outer layer on the PBF-derived samples, approximately a few micrometers thick, which the authors suggest may have slowed further infiltration.

Mechanical compression testing reflected the densification trend. After two CVI cycles, the PBF+PIP samples went up from about 4.3 ± 1.4 MPa after pyrolysis to about 7.9 ± 0.4 The BJ samples showed the largest strength change, rising from about 0.3 ± 0.1 MPa after pyrolysis to about 13.3 ± 0.8 MPa after the second CVI cycle, which the study attributes to improved bonding and reduced porosity as CVI deposited SiC within the pore network.

## Oxidation at 1500°C

Oxidation tests in air at 1500°C for up to 8 hours showed that both CVI-processed methods were very resistant to oxidation. The study links this behavior to SiC's natural resistance to oxidation, which forms a protective layer of silica (SiO₂) on its surfaces, as supported by EDX mapping showing elevated levels of silicon and oxygen at the surface after oxidation. The PBF+PIP samples gained less mass than the CBJ samples. The authors think this effect is due to the PBF+PIP samples having lower porosity and a smaller surface area that could be oxidized.

The paper also looks at how these CVI-processed ceramics compare to previously studied Si–SiC materials, stating that getting rid of free silicon helps prevent issues with In the BJ specimens, the authors report cracking and fragmentation of silica layers during cooling, which is consistent with cristobalite-related phase changes and thermal expansion mismatches that can stress brittle oxide scales while still observing overall oxidation resistance at the test temperature.