• 한국세라믹학회지
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• 제55권2호
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• pp.126-134
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• 2018

Using aqueous solution free radical polymerization with glacial acrylic acid (GAA), maleic anhydride (MA) and sodium methallyl disulfonate (SMADS), a novel linear polycarboxylate dispersant was synthesized for ceramics. Dispersant linear structural characterization was done by FTIR, $^1H$ NMR, HPLC and GPC, and the ratio of monomers was determined using an orthogonal experiment. This research is focused on the effects of polymerization temperature, monomer mole ratios and dosage of initiator on ceramic slurry viscosity with linear polycarboxylate dispersant for ceramic dosage rate of 0.30% (based on dry slurry), all of which were investigated by single factor test. The best polymerization conditions for linear GAA-MA-SMADS are when n(AA) : n(MA) : n(SMADS) equals 3.0 : 1.0 : 0.5, the molecular weight of the polymer is 4600 daltons, the initiator sodium persulfate accounts for 7% of the total mass of polymerized monomers, the polymerization temperature is $90^{\circ}C$ and the reaction time is 2 h. The ceramic body slurry viscosity drops from $820mPa{\cdot}s$ to $46mPa{\cdot}s$ when the concentration of the polycarboxylate dispersant is 0.30%.

• The Korean Journal of Ceramics
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• 제4권4호
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• pp.292-296
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• 1998

In wet powder processing of alumina, a number of organic molecules such as dispersant and binder are used to produce the flow behavior and properties requisite for shape forming. In this study, interparticle forces of alumina particles suspended in aqueous media were controlled by suspension pH, poly (methacrylic acid) (PMAA, used as dispersant) and poly (vinyl alcohol) (PVA, used as binder). The combined adsorption isotherms of the dispersant and binder additives on alumina were determined by total organic carbon analyzer, while the adsorption of dispersant was differentiated from binder in the mixed additive system by ultraviolet spectroscopy. The electrokinetic behavior of alumina suspensions were then correlated with the adsorption characteristics of dispersant and binder onto alumina particles. It was found that the isoelectric ($pH_{iep}$) of alumina shifted from pH 8.9${\pm}$0.1 to acidic pH as PMAA concentration increased, while PVA adsorption did not affect the $pH_{iep}$ but caused a decrease in the near surface potential.

• 한국세라믹학회지
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• 제33권2호
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• pp.214-222
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• 1996

The effect of physicochemical properties of organic solvent and dispersant among organic solvent dispersant binder and plasticizer which are used as processing additives in MLCC fabrication process on the dispersion of BaTiO3 was studied. The steric and electrostatic stabilization mechanisms in dispersion of BaTiO3 in organic media were evaluated respectively. The sttability of BaTiO3 achieved bysteric stabilization was dependent on the fraction of surface coverage of dispersant adsorption on BaTiO3. The electrostatic repulsive forces of BaTiO3 particles dispersed in orgainc media was found to be appreciabley great and dependent mainly on the kinds of organic solvent used. The mechanism affecting the stability of BaTiO3 was studied by the method of rheologi-cal behaviors of BaTiO3 suspension.

• 한국전기전자재료학회논문지
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• 제32권1호
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• pp.25-29
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• 2019

Various process technologies for manufacturing power inductors are under development. The core goal is to increase the mixing ratio of the soft magnetic powder in the epoxy, and to uniformly disperse it in a molding-type power inductor, manufactured by the injection molding method. In this study, we investigated the effect of dispersant and silane on the dispersion of soft magnetic metal powders in epoxy. We added 0.6 wt% of dispersant and 2.0 wt% of silane, and an excellent dispersibility resulted. Under the conditions of 0.3 wt% of dispersant and 0.5 wt% of silane, we added both dispersant and silane together to observe the effect of their interaction on dispersibility. Similarly, the addition of 0.3 wt% of dispersant and 0.1 wt% of silane resulted in a sharp increase in viscosity, considered to be due to the interaction of the dispersant and silane. The addition of 0.1 wt% of dispersant with 0.5 wt% of silane resulted in a sharp rise in viscosity, and sedimentation-height decreased sharply due to the dispersion optimization.

• 한국세라믹학회지
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• 제43권10호
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• pp.635-639
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• 2006

Dispersion behavior of the slurries consisted of Pb or Bi-based glass frits, which are used for the fabrication of green sheet as PDP front panel transparent dielectric, was examined in non-aqueous solvent system. Measurements of sedimentation height and viscosity were conducted to determine proper dispersion condition in the various solvent and dispersant system. Azotropic compound and ethyl acetate were used as the solvent and ammonium-type dispersant was applied to the slurries. All slurries were dispersed well in azotropic solvent system involving 20$\sim$50 vol% ethyl acetate at 2$\sim$3 wt% dispersant content. Especially, dispersion behavior was notably improved in the addition of ethyl acetate in the Bi-based frit slurry.

• 한국세라믹학회지
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• 제47권6호
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• pp.566-571
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• 2010

Dispersion behavior of the slurries consisted of bimodal-type AlN powders was examined in non-aqueous solvent system. Azotropic solvent system and copolymer acidic dispersant were applied to the slurries. Measurements of the sedimentation height and the viscosity of the each slurry, and the test of particle size distribution of the each powder sample were conducted as examinations for the dispersion behavior at the various dispersant contents. The bimodal-type particle size distribution was continued after addition of the dispersant and small particle portions were increased as the dispersant content increases. The density of the green sheet was also increased as the dispersant content increases and a green density of $2.114\;g/cm^3$ was obtained at the sample prepared from 2.4 wt% dispersant content. The increase of large particle portions resulted in the surface defects of the green sheets.

• 한국세라믹학회지
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• 제32권8호
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• pp.901-908
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• 1995

In aqueous slurry processing of silicon nitride, the interaction of dispersant and binder used as polymeric processing additives on the silicon nitride particle surface was studied to identify the effect of these processing polymeric additives on the ceramic powder processing. The adsoprtion isotherm study of anionic organic molecule as dispersant and nonionic organic molecules as binder of silicon nitricde was studied to investigate the effect of these processing organic additives on the physicochemical properties of silicon nitride particles. As anionic molecule adsorbed onto silicon nitrice surface, the IEP of silicon nitride shifted toward acidic pH and changed the stability of silicon nitride particle. However, the adsorption of binder as nonionic organic molecule onto silicon nitride surface did not changed the IEP but caused the decrease of electrostatic potentials of silicon nitride. These distinctive adsorption behaviors of organic additives on silicon nitride particles can be closely correlated to the stability of silicon nitride particles suspended in aqueous media.

• 한국세라믹학회지
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• 제30권4호
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• pp.299-308
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• 1993

Dispersant was used to avoid the agglomeration of aluminum hydrate precipitate and improve the sinterability of calcined alumina powder. The mean particle size of the aluminum hydrate precipitates was 0.26${\mu}{\textrm}{m}$ and 0.44${\mu}{\textrm}{m}$ when ball-milled with and without dispersant, respectively. After calcination at 110$0^{\circ}C$ for 5 hours, the size of the alumina powder without dispersant increased to 0.84${\mu}{\textrm}{m}$, while with dispersant slightly decreased to 0.22${\mu}{\textrm}{m}$. The most thermally active alumina powder was obtained from the sample calcined at 110$0^{\circ}C$ for 5 hours with the 1% dispersant concentration. Using the calcined alumina powder at the above optimized condition, the specimen showed fired density of 3.94g/㎤, 4-point MOR of 364MPa, and KIC of 3.26MPam1/2 after sintered at 155$0^{\circ}C$ for 3 hours.

• 한국세라믹학회지
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• 제39권2호
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• pp.164-170
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• 2002

Acrylate 수계 결합제를 사용한 알루미나 테이프 캐스팅용 슬러리의 완전분산을 위한 최적의 분산제와 분산제량을 결정하기 위해 침강실험, 분말 함유량 실험, 점도 및 zeta 전위 측정을 행하였다. 알루미나 슬러리의 완전분산은 분산제를 polycarboxylic acid로 했을 때 얻어졌으며, 최적의 첨가량은 알루미나 100에 대하여 0.23∼0.24g 이었다. 분말에 대한 분산제량이 증가할수록 분산은 잘 이루어졌으나, 일정량 이상이 첨가되면 분산제가 용매 안에 과잉으로 존재하여 분산을 저해하는 요인으로 작용하였다. 테이프 캐스팅용 슬러리는 100g의 알루미나 분말에 0.2g의 polycarboxylic acid를 첨가하였을 때 분산 및 테이프 특성이 가장 우수하였고, 이 때 혼합한 결합제는 acrylate였고, 가소제는 Benzoflex를 사용하였다. 이 때 슬러리 최적 점도는 약 570 cps였고, 테이프 내 알루미나 량은 57 vol%이었다.

• 한국전기전자재료학회논문지
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• 제21권3호
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• pp.236-241
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• 2008

The effect of organic solvent mixture ratio on the rheology property of slurry and thickness control of ceramic green sheet was investigated. For selecting a suitable dispersant multiple light scattering method was used to evaluate the particle migration velocity and variation of clarification layer thickness. Using the selected dispersant the dispersion property of solution according to solvent mixture ratio was investigated. Binder and plasticizers were added to formulate slurries and their viscosity was evaluated according to solvent mixture ratio. Ceramic green sheets with average thickness of 30, 50 urn were fabricated via tape casting and their thickness tolerances measured. As a result according to solvent mixture ratio the solution and slurry properties varied and for the mixture ratio of ethanol/toluene of 80/20 the ceramic green sheet with the lowest thickness tolerance was obtained.