Papers by Keyword: Dispersant

Abstract: Shallow trench isolation via chemical mechanical polishing (CMP-STI) tests of Si wafers using CeO₂ slurry were studied. The impact of CeO₂ slurry's solid concentration on the SiO₂ removal rate and the selectivity ratio The effects of the solid concentration of CeO₂ slurry on the removal rate of SiO₂ and selectivity (SiO₂/Si₃N₄) were investigated. The CeO₂ abrasive was well matched to the XRD standard pattern, confirming that it had a cubic phase and the absence of any impurities. The SEM image showed that CeO₂ primary particles had a spherical-like shape with a size within 30-60 nm. Additionally, the prepared CeO₂ slurry showed a relatively high dispersion level. The wettability degree of the CeO₂ slurry on top of the Si wafer surface was also sufficient. Furthermore, results from polishing tests indicated that both the SiO₂ removal rate and the selectivity increased linearly with a rise in CeO₂ solid concentration.

Abstract: A superplasticizer or dispersant acts as a friction reducer to enhance the rheological properties of cement slurry, thereby eliminating the need for high pump pressure to pump the viscous slurry behind the casing. Polynaphthalene sulfonate (PNS) is a common dispersant for well cement; however, with the emergence of geopolymer technology for oil wells, the application of PNS in the industry has yet to be investigated. The focus of the research is to examine the influences of PNS on the early, medium, and final compressive strength of geopolymer cement cured at 3000 psi and 100 °C with PNS concentration ranging from 0.0 to 2.0 by weight of fly ash (bwof %). The findings show that PNS can increase the 8-hour compressive strength of geopolymer cement, but it can decrease the 24-hour compressive strength. However, only the sample with the highest concentration of PNS exhibits better compressive strength than the control sample at 48 hours. Additionally, the results demonstrate that the compressive strength of geopolymer cement with PNS increases with a longer curing duration. It is advisable to run a prediction plot to determine the optimum concentration that can result in high compressive strength for 8, 24 and 48 hours.

Abstract: Oil soluble polymeric-based dispersants have been extensively used in engine oil lubrication formulation due to their inherent properties, such as modifiable viscosity, compatibility, and effectiveness. However, the underlying mechanism of how the dispersant stabilizes soot particles in engine oil is still not fully understood, and discovering this mechanism is crucial for engine oil formulation technology. This review discusses the interactions between colloidal particles induced by two PIBSA-derived dispersants, namely PIBSI and PIBSAE. The effectiveness of these dispersants in stabilizing colloidal particles in oil systems depends on the chemical functional groups present on the main chain. The spectrum of colloidal interactions, ranging from Derjaguin, Landau, Verwey and Overbeek (DLVO) to non-DLVO theory, is predominantly influenced by the equilibrium between dispersant concentration and the overall system viscosity. This phenomenon can eventually reverse colloidal stabilization and result in more serious issues, such as engine wear and tear.

Abstract: The conventional oil-well cement dispersant has the characteristics of poor dispersion at high temperature, poor compatibility with other additives, and environmental pollution during the production process. In this article, with ultra-early strong polyether monomer, acrylic acid, 2-acrylamine-2-methylpropyl sulfonic acid, sodium methacrylate as copolymer monomers, an environmentally friendly polycarboxylic acid dispersant, DRPC-1L, was prepared by the aqueous solution free-radical polymerization. The chemical composition and thermal stability of the synthetic copolymer were characterized by FTIR and TGA techniques. The evaluation results show that DRPC-1L has a wide temperature range (30~210 °C), good salt-resistance and dispersing effect. It can significantly improve the rheological performance of cement slurry, and it is well matched with oil-well cement additives such as fluid loss agent, retarder and so on. Moreover, it is beneficial to the mechanical strength development of set cement, especially the early compressive strength. It can also inhibit the abnormal gelation phenomenon of cement slurry, flash set, that occurs during high temperature thickening experiments, which plays an important role in enhancing the comprehensive performance of cement slurry. Consequently, the novel polycarboxylic acid dispersant has good application prospects in deep and ultra-deep wells cementing.

Abstract: Separate and combined effects of sodium hex metaphosphate (SHMP) and polycarboxylate superplasticizer (PCS) of different dosages (0.5%, 1%, 1.5%, and 2%) on the dispersion stability of nanoSiO₂ (NS) were studied. The effect of the dispersant was characterized by the change of absorbance. When SHMP and PCS were used separately and in combination, the stability of nanoSiO₂ dispersions was compared and the optimal amount of dispersant for different dosage of nanoSiO₂ dispersions were summarized. Finally, the mechanism of dispersant compounding was discussed. The results show that with the increase of the concentration, the optimal amount of SHMP increases significantly while the optimal amount of PCS dispersant is lower and better than SHMP. A clear linear relationship between the optimal dosage of SHMP and the concentration of NS could be found. If SHMP is used combined with PCS, the stability of the dispersed NS will increase and the dosages of both dispersants will be reduced.

Abstract: Calcium aluminate cement (CAC) and hydratable alumina (HA) are the most widely used binders for refractory castables. Nevertheless, CAC as the binder for refractory castable generates some low melting point phases when coupled with SiO₂, which deteriorate the high temperature performance of refractory castables. Although hydratable alumina (HA) bonded castables overcome the drawbacks of CAC bonded ones, they demand a longer mixing time and higher water contents due to HA's high specific surface area, as well as increasing the shear stress and viscosity of HA bonded castables. Therefore, in this paper, CAC combined with HA was used as the binder for corundum- spinel castables to obtain better performance. Sodium tripolyphosphate (STPP), dispersing alumina (ADS) and polycarboxylate ether dispersant (FS60) were used as dispersants, and their effects on the rheological behaviors of CAC-HA bonded corundum-spinel castables suspensions had been investigated. According to the viscosity-shear rate and stress-shear rate curves of suspensions with different dispersants, it was suggested that STPP, ADS, FS60 were all helpful for rheological performance of suspensions. Suspensions achieved much better rheological behavior with 0.3 wt.% of STPP, 1.0wt.% of ADS and 0.1wt.% of FS60, respectively. Suspensions with ADS and FS60 presented to be pseudo plastic fluid, which was helpful for the installation process of CAC-HA bonded corundum-spinel castables. And FS60 could simultaneously impart electrostatic and steric stabilization to the given suspension. Considering the actual rheological performance of CAC-HA bonded corundum-spinel castables, FS60 was much better than ADS.

Abstract: Three dispersants cetyl trimethyl ammonium bromide (CTMAB), N-N dimethyl formamide (DMF) and N-methyl pyrrolidone (NMP) were added to disperse graphene (GPLs) and a type of graphene/alumina composite ceramics was fabricated by microwave sintering. The GPLs dispersion was characterized by Zeta potential, XRD and SEM. The experimental results show that anionic dispersant NMP has the best dispersion effect with no impurities when pH value is 5. Using dispersant NMP, 0.4vol.%GPLs/Al₂O₃ composites with high dispersion obtains a relative density of 98.76% at 1500°C for 30 min by microwave sintering. The microhardness, fracture toughness and flexural strength of this composites are 19.58GPa, 6.19MPa·m^1/2 and 365.10MPa, respectively. Its fracture toughness respectively increases by 47% and 15% than that of composites using dispersants DMF and CTMAB.

Abstract: Polyethylene glycol (PEG-200) and itaconic acid (IA) were used as raw materials to compound macromer through esterification reaction. A new type of specialized water-coke slurry dispersant was synthesized by copolymerization of microware, sodium methallyl sulfonate (SMAS) and maleic anhydride (MA). The experiment showed that the concentration of slurry could be reached to 63% with the dosage of 0.2%, and the apparent viscosity was 1140.3 mPa∙s. Through the analysis of the infrared, the dispersant was confirmed to have polyethylene glycol branched chain and hydrophilic functional groups such as carboxyl or sulfonic group. When the concentration of dispersant was 30 g/L, the surface tension of water could be decreased from 72.70 mN/m to 45.50 mN/m. Furthermore, when the solution pH value was 9, the Zeta potential of semi-coke powder surface could also be decreased from-13.38 mV to-25 mV with the addition of dispersant. Thus, this dispersant could increase electronegativity of semi-coke powder surface, enhance steric-hindrance effect and prevent the phenomenon of powder flocculation and gather. Meantime, it also could reinforce the semi-coke hydrophilic by reducing the surface tension of water effectively. And then, the high performance water-coke slurry could be obtained.

Abstract: The composite ZrB₂ powder coated A1₂O₃-Y₂O₃ prepared by co-precipitation method were densified via the spark plasma sintering (SPS) and then researched the oxidation resistance at high temperature. ZrB₂ powder must have the better dispersibility during the coating processing for obtaining the better coating effect. Effect of dispersant on the dispersibility of ZrB₂ powder in the liquid is researched in this paper, the results show ZrB₂ powder have the better dispersibility as the dispersant for PMAA and the content for 2vol%, which lay foundation for synthsising the better coating effect coated A1₂O₃-Y₂O₃-ZrB₂ composite powder.

Abstract: The abundancy of ball clay can be transform into more useful form. This study was conducted to investigate the effect of different amount of dispersant on ceramic system. Ball clay from Kampung Dengir, Besut, Terengganu was used as starting powder while sodium silicate was used as dispersant to produce good flow ability, minimum viscosity and controllable ceramic slurry. Ceramic slurry was prepared by adding additives such as binder, flux, filler and dispersant, casted onto POP mould to obtain ceramic body. Ceramic then cut into test pieces (8cm x 2cm) and mixed for 2 h and aged for 2 days before dried at 70 °C overnight and sintered at temperature of 800-1200 °C in furnace for 2 h with heating rate 5 °C/min. Slurries also tested for rheological properties using rheometer (brand Thermo Haake). Viscosity and shear stress were measured to investigate the rhoelogical behaviour of slip with different amount of dispersant (0.03 mL to 0.06 mL/200 mL of sample). Characterization of raw samples has been done using X-ray diffractometer (XRD) showing the presence of kaolinite and quartz. Effect of dispersant on rheological behavior, rate of shrinkage, water absorption, porosity and density were investigated It was found that increase in amount of dispersant added exhibit the best rheological behavior, and 0.05 mL dispersant was the optimum amount in term of rate of shrinkage, water absorption, porosity and density. As a conclusion, 0.05 mL was the optimum dispersant which gives best rheological behavior and almost fault-free ceramic bodies