Schematic of apparatus used for foaming stability and microstructure evaluation. (1) CO₂ gas tank; (2) Gas booster pump; (3) Gas inlet valve; (4) CO₂ intermediate container; (5) ISCO pump; (6) Computer using for imaging; (7) Microscope; (8) High-pressure optical cell; (9) Back pressure regulator; (10) Gas–liquid separator; (11) LED light; (12) High-pressure view chamber; (13) Liquid inlet valve; (14) Sapphire glass; (15) Heat exchanger; (16) Mixing blade; (17) Electric motor; (18) Gas inlet valve; (19) Computer using for control; (20) Liquid intermediate container.