Table 3. List of Commonly Used Space Holder Material.

space holder type	material	melting temperatures (°C)	space holder removal method	recommended application
Salt beads	NaCl85	801	By dissolution in water	For the preparation of aluminum foam for various industrial applications like mechanical, thermal, sound, and vibration85
	KCl86	770	By thermal decomposition	For the preparation of ZrB2-SiC foam for structural application86
	Carbamide granules87	133–135	By leaching in distilled water	For the preparation of steel foam for automotive and lightweight structures87
	Glycine Powder88	233	By dissolution in water or by thermal decomposition	For the preparation of steel foam for biomedical implants88
	(NH4) HCO389,90	41.9	By thermal decomposition	For the preparation of NiTi shape memory alloy foam for biomedical implants89,90
	CaCl291	772	By dissolution in water	For the preparation of high porosity Al foam91
Woven Wire Mesh	Titanium92	1668	By leaching in HF acid	For the preparation of magnesium foam for orthopedic applications92
Spheres + Wire + Mesh	Steel93	1371–1540	Electrochemical dissolution	For the preparation of titanium foam for industrial applications93
Ceramics	Furan-bonded sand and gypsum94	1400, 1710	With the help of a water bath and mechanical vibration	For the preparation of Al foam, which has various industrial applications such as uniform gas distribution, flow stabilization, filtration, and condensation.94
Polymers	PMMA95,96	160	By thermal decomposition	For the preparation of Al and Mg foams for energy absorption and compressive applications95,96
Carbonate	K2CO397	891	By thermal decomposition	For the preparation of metallic foams with high melting temperatures such as Cu, Fe, Ti, and Ni97