Hydrolysis of carboxylic lactones in alumina slurries

Rheological Characterization and Coagulation Casting of Al2O3–Nano Zirconia Suspensions

“…In order to promote coagulation, 0.5 to 6.7 wt% additions, by reference to the solids loading, of Glucono-δ-lactone (Jungbunzlauer, Basel, Switzerland) were introduced to the suspensions, followed by stirring for 1 minute, in line with previous studies 34,37,38 before the suspensions were cast in non porous plastic moulds measuring 60 × 60 × 25 mm that had been coated by a thin layer of lubricant (multipurpose grease, RS Components, Corby, Northamptonshire, UK) in order to avoid cracks forming due to sticking during drying of the green bodies.…”

“…lactones, as coagulants has been successfully applied to aqueous alumina suspensions 33,[37][38][39] and subsequently patented. 40 Although a wide range of different lactones can be used to achieve in-situ coagulation 39 via their hydrolysis to gluconic acid, which causes a pH shift towards the system's isoelectric point where the net surface charge is zero, Glucono-δ-lactone has been determined to be one of the most effective in terms of the efficiency of the process and lower price.…”

Magnesia induced coagulation of aqueous PZT powder suspensions for direct coagulation casting

“…Direct coagulation casting (DCC) is a relatively new ceramic shape forming process from concentrated ceramic powder suspensions [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. The process has created more interest among the researchers as it is completely free from the use of polymeric binders.…”

“…In DCC, concentrated ceramic powder suspensions cast in a mould is set in to rigid gel, by in situ coagulation, which can be removed from the mould immediately after gelation. In situ coagulation of ceramic powder suspensions has been achieved either by shifting the pH of the medium towards the iso-electric point of the ceramic powder by time delayed in situ generation of acid or base from water-soluble precursor molecules or by compressing the electric double layer by in situ generation of excess electrolyte [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Enzyme catalyzed in situ hydrolysis of urea has been used to increase both the pH (due to ammonia) and concentration of electrolytes like ammonium carbonates and ammonium bi-carbonate that coagulate powder suspensions of alumina, zirconia, silicon carbide and silicon nitride [1][2][3][4][5][6][7][8][9][10][11][12].…”

“…Enzyme catalyzed in situ hydrolysis of urea has been used to increase both the pH (due to ammonia) and concentration of electrolytes like ammonium carbonates and ammonium bi-carbonate that coagulate powder suspensions of alumina, zirconia, silicon carbide and silicon nitride [1][2][3][4][5][6][7][8][9][10][11][12]. Coagulation by in situ generation of acid from watersoluble precursor molecules such as acid anhydrides, esters, lactones, and hydroxy aluminium acetate has also been reported for setting of ceramic powder suspensions prepared in alkaline pH range or using ploy (electrolyte) dispersants [13][14][15][16][17][18].…”