PAA—NH4对氧化铝悬浮液沉降性生能的研究

采用PAA—NH4作为分散剂制备了超细氧化铝悬桴液,通过沉降实验观察了PAA-NH4的添加量、pH值对α—Al2O3低固含量悬浮液的沉降性能的影响,并用Zeta电位仪测定了不同pH值条件下稀固相含量悬浮液的Zeta电位;同时对烧结坯体进行了微观分析。结果表明：分散剂PAA—NH4的最佳用量为1．0％左右,最佳pH值为9;对添加PAA—NH4前后的稀悬浮液Zeta电位进行了测定,发现等电势点左移,Zeta电位的绝对值变化显著。添加PAA-NH4后,pH值的变化对悬浮液的沉降性能和Zeta电位影响很大。     

α-Al2O3-H2O-聚丙烯酸悬浮液的抗电解质性能

研究了电解质对α-Al2O3-H2O-聚丙烯酸(polyacrylic acid,PAA)浆料流变性的影响以及α-Al2O3-H2O-PAA悬浮液的抗电解质性能.结果表明:在pH值为6.5,PAA溶液添加质量分数为0.5%时,NaCl浓度提高,悬浮液的流变性下降.但在0.1～0.2 mol/L的浓度之间时,悬浮液的流变性能基本不随电解质浓度的变化而变化.在不同pH值条件下,PAA溶液最小添加量受电解质浓度影响的程度以及稳定浆料抗电解质能力显著不同.在酸性介质中,更有利于制备具有抗电解质性能的稳定悬浮液.     

pH对α-Al2O3-H2O-聚丙烯酸悬浮液稳定性的影响

研究了pH对α-Al2O3-H2O-聚丙烯酸悬浮液稳定性的影响。研究结果表明：对于给定的PAA添加量的浆料．其稳定性随着pH的提高有明显地提高；提高浆料的pH值，PAA最佳添加量减少；固含量分数在54％左右的浆料．在不同的pH值，加入最佳PAA添加量时，其浆料粘度显著不同；以PAA为分散剂制备高固相体积分数的α-Al2O3浆料的最佳pH值为8．5。     

改性斜发沸石对微污染饮用水的处理研究

研究了斜发沸石经NaCl、NH4NO3改性处理后对微污染饮用水中氨氮的吸附。结果表明：改性斜发沸石对氨氮有较好的吸附,吸附温度为常温,NaCl溶液、NH4NO3溶液改性斜发沸石的最佳浓度分别为0．6-1mol／L、1．5-2mol／L,氨氮的去除率达90％。     

蔗糖对PAA-H2O-Al2O3浆料流变性能的影响

研究了蔗糖(sucrose)对聚丙烯酸(PAA)-水基Al2O3悬浮液流变性能的影响.实验表明:在酸性与碱性条件下,蔗糖的添加都有助于提高PAA稳定的水基Al2O3悬浮液流变性.pH为9.0时,PAA-H2O-AlO2悬浮液粘度随着蔗糖含量的增加逐渐降低,当含量大于4wt％时其粘度趋于不变.其中蔗糖对低含量PAA(0.3wt％)稳定的浆料流变性提高尤为明显.对于固含量为25 ～ 40vol％的PAA-H2O-Al2O3悬浮液,4wt％的蔗糖的加入都能提高其稳定性,当固含量为40vol％时,效果最为明显.此外,蔗糖的添加能够较好的提高PAA-H2O-Al2O3悬浮液的抗电解质性能.     

PAA-PEO对ZrO2-H2O悬浮液流变性能的影响

利用一种新型的分散剂—梳型共聚物poly（acrylic acid）-pofy（ethyfene oxide）（PAA—PEO）,研究了pH、分散剂的添加量及固含量对ZrO2-H2O悬浮液的流变性能的影响。结果表明：在pH为3、PAA-PEO的添加量为0．3wt％,ZrO2-H2O悬浮液的粘度最低;固含量在31vol％以下时,浆料都保持稳定状态;随着固含量的增加,浆料的粘度也增加,当固含量达到33vol％时,浆料呈现出明显的剪切变稀行为。     

聚乙烯吡咯烷酮对PESA-H2O-SiC悬浮液流变性能的影响

研究了聚乙烯吡咯烷酮(PVP)对聚环氧琥珀酸(PESA)稳定的水基碳化硅(SiC)悬浮液流变性能的影响.结果表明,在pH值为9.0时,添加一定比例的少剂量的二元分散剂即可改善SiC悬浮液的分散性.当分散剂总添加量为0.4wt％,PESA与PVP的质量之比为3∶1时,悬浮液的流变性最佳.固含量为40vo1％时,PESA稳定的SiC悬浮液完全絮凝,而添加PVP作为第二分散剂可使体系较好的分散.此外,添加二元分散剂PESA/PVP显著提高了SiC悬浮液的抗电解质性能.     

超细二氧化锆注凝成形料浆流变性研究

研究了ZrO2凝胶注模成形工艺中制备低粘度、高固相含量浓悬浮体的关键技术。分析讨论了pH值、分散剂、研磨时间、固相含量等因素对ZrO2浆料粘度的影响。实验表明：pH值、分散剂用量均会明显地影响悬浮液的分散效果和流变性。在悬浮体系中当pH为10-11，分散剂添加量为1．5％（体积分数）时，研磨时间为20h时分散效果最好，并制备了固相含量达56％（体积分数）的浓悬浮液，粘度为308mPa·s，完全能满足凝胶注模成形的要求。     

PVP对CA-H2O-Al2O3悬浮液稳定性的影响

利用柠檬酸(CA)与聚乙烯吡咯烷酮(PVP)复配为二元分散剂,研究其对水基氧化铝悬浮液稳定性的影响。结果表明,pH为9.0时,仅添加0.2 wt%的CA/PVP即可稳定分散固含量为45 v%的氧化铝悬浮液,且浆料为牛顿流体,流变性很好。固含量越高,悬浮液的粘度越大,对pH值越敏感,悬浮液能分散稳定的pH值范围越窄,对于不同的体系,获得最佳流变性时的pH值也不同。     

硝酸改性凹凸棒石粘土及吸附Cu2+的工艺研究

将凹凸棒石粘土用硝酸进行改性处理,然后用于对含铜废水中铜离子的吸附,研究了硝酸浓度、改性凹凸棒石粘土用量、吸附时间、pH值等因素对吸附性能的影响。结果表明:经4mol/LHNO3改性处理后的凹凸棒石粘土吸附能力最好,凹凸棒石粘土加入量为30g/L,水样pH值为4,超声搅拌20min,废水中Cu2+的吸附率接近99%,同时吸附剂的再生实验表明,复用时吸附量下降平缓,可以重复使用。     

Improvement of the Dispersion of Al2O3 Slurries Using EDTA-4Na

Polyacrylic acid (PAA) is known to be an effective dispersant for Al₂O₃ powder in aqueous media. However, at high solid loading (>55 vol%), the dispersion of the Al₂O₃ suspensions became difficult with only PAA as a dispersant. In this paper, ethylenediaminetetraacetic acid, tetrasodium salt, dihydrate (EDTA-4Na) was introduced to improve the dispersion of the Al₂O₃ suspensions. With the aid of EDTA-4Na, the adsorption amount of sodium polyacrylic acid (PAA-Na) increased, while the apparent viscosity of 60 vol% Al₂O₃ slurries decreased significantly. Particle size measurements showed that EDTA-4Na could help to reduce larger agglomerates, possibly by modifying the adsorbed layer thickness. The interactions between EDTA-4Na and PAA-Na were studied using Fourier-transform infrared spectroscopy analysis. Results showed that it was possible to introduce EDTA-4Na as the second dispersant to improve the dispersion of high solid content Al₂O₃ slurries.     

凹凸棒基高分子固沙材料的表征及性能研究

以酸化凹凸棒石和丙烯酰胺为原料,N-N亚甲基丙烯酰胺为交联剂,过硫酸钾为引发剂,采用水溶液聚合法合成了凹凸棒石基高分子固沙材料.通过研究不同浓度硫酸活化的凹凸棒石基高分子固沙材料的吸水性能、保水性能、pH值以及X衍射以及扫描电镜,结果表明4 mol/L硫酸改性的凹凸棒石基高分子固沙材料具有更好的吸水性能和保水性能;pH值的变化对4 mol/L硫酸改性的凹凸棒石基高分子固沙材料具有较大的影响;X衍射以及扫描电镜表明3 mol/L和4 mol/L硫酸改性的凹凸棒石基高分子固沙材料具有更好的吸附性能.研究结果对于加强深入硫酸改性的凹凸棒石基高分子固沙材料的研究重具有要意义,以期制备出一种新型环保型复合高吸水性凹凸棒石基高分子固沙材料.     

Fe2O3/凹凸棒土吸附-光催化法处理间氯甲苯工业废水研究

采用酸化法对凹凸棒土进行改性,考察改性条件、投加量、吸附时间以及废水pH值等因素对吸附效果的影响。在盐酸浓度为4mol/L,煅烧温度为200℃时,在最佳吸附条件（改性凹凸棒土投加量0.500g/25mL,废水pH=4,吸附时间1h）下,吸附法处理染料中间体间氯甲苯废水,COD的去除率由改性前的2.2%提高到14.1%。采用浸渍法制备纳米Fe2O3/凹凸棒土复合催化剂并对其表征,XRD分析结果表明,该复合物中光催化剂主要由α-Fe2O3构成;用凹凸棒土吸附-光催化氧化联合法处理间氯甲苯工业废水,在催化剂加入量为1.0g/L,pH=2,紫外光或太阳光照6h条件下,废水COD去除率分别达到59.2%和52.3%。复合催化剂的光催化活性要远大于纯纳米α-Fe2O3的光催化活性。     

Hydrolysis and Dispersion Properties of Aqueous Y2Si2O7 Suspensions

The dispersion of aqueous γ-Y₂Si₂O₇ suspensions, which contain only one component but have a complex ion environment, was studied by the introduction of two different polymer dispersants, polyethylenimine (PEI) and polyacrylic acid (PAA). The suspension without any dispersant remains stable in the pH range of 9–11.5 because of electrostatic repulsion, while it is flocculated upon stirring due to the readsorption of hydrolyzed ions on the colloid surface. However, suspensions with 1 dwb% PEI exhibit greater stability in the pH range of 4–11.5. The addition of PEI shifts the isoelectric point (IEP) of the suspensions from pH 5.8 to 10.8. Near the IEP (pH_IEP=10.8), the stability of the suspensions with PEI is dominated by the steric effect. When the pH is decreased to acid direction, the stabilization mechanism is changed from steric hindrance to an electrosteric effect little by little. PAA also has the effect of reducing the hydrolysis speed via a "buffer effect" in the basic pH range, but the lack of adsorption between the highly ionized anionic polymer molecules and the negative colloid particle surfaces shows no positive effect on hydrolysis of colloids and on the stabilization of Y₂Si₂O₇ suspensions.     

Electrostatic and electrosteric stabilization of aqueous suspensions of barite nanoparticles

Electrostatic and electrosteric stabilization of aqueous suspensions of barite nanoparticles were investigated. The state of dispersion was evaluated in terms of zeta potential, apparent viscosity and the mean particle size of solid phase in the solution. Zeta potential, apparent viscosity and the mean particle size as a function of pH were performed in absence of dispersant. The result showed that electrostatic stabilization of the aqueous suspension of barite nanoparticles can be accomplished in low acidic and high basic range of pH. In presence of sodium polyacrylate (PAA-Na) dispersant, the isoelectric point (IEP) of the barite nanoparticles was shifted to lower pH and the negative zeta potential was increased in a large range of pH above the (IEP). The optimum amount of PAA-Na dispersant is discussed in the light of zeta potential and viscosity. It is found that the adsorption of PAA is correlated to the net surface charge of the barite nanoparticles and the fraction of dissociated polymer at pH 4, 8.5 and 10. At pH 4, the state of dispersion was achieved at higher amount of electrolyte due to the low fraction of negatively charged dissociated polymer and the positively charge particles. At basic pH, the fraction of dissociated polymer was high and the surface charge of particle was highly negative, therefore, the lowest viscosity was obtained at a small amount of PAA. In addition, the optimum amount of polymer decreased with the increase in pH of the suspension.     

Aqueous tape casting and crystallization behavior of gadolinium-doped ceria

An aqueous tape casting of gadolinia-doped ceria (GDC) ceramics was developed using Poly(acrylic acid) PAA as dispersant, Poly(vinyl alcohol) PVA as binder, Poly(ethylene glycol) PEG as plasticizer, and deionized water as solvent. Surface properties of GDC powder with and without PAA dispersant were characterized by electrokinetic measurements. The zeta potential measurement revealed that the isoelectric point for GDC powders in the absence of dispersant corresponds to a pH value of 4.06. The experimental results showed that pH value greatly affects the rheology of the slurry. Homogeneous, smooth, and defect-free green tapes were successfully obtained by using an appropriate slurry formula. Moreover, the crystallization kinetics of GDC powders prepared by coprecipitation process also has been investigated in this study. The activation energy of crystallization was calculated by differential scanning calorimetry (DSC) at different heating rates. Analysis of non-isothermal DSC data presented values of 105.3 kJ/mol and 1.171 for the activation energy of crystallization presented and the Avrami exponent, respectively.     

α-Al2O3-H2O-聚丙烯酸悬浮液流变性的研究

研究了聚丙烯酸(polyacrylic acid,PAA)添加量、固含量和吸附途径对α—Al2O3浆料流变性的影响。实验表明：浆料具有最小粘度时,分散剂添加量存在最佳值。随着固含量提高,浆料最低粘度值提高,分散剂有效添加量范围变窄。吸附途径对浆料的流变性存在一定的影响,在其它条件相同的情况下,低pH值浆料经历非亲合力状态下的吸附,浆料流变性明显改善。     

Effect of 2-Phosphonobutane-1,2,4-tricarboxylic Acid Adsorption on the Stability and Rheological Properties of Aqueous Nanosized 3-mol%-Yttria-Stabilized Tetragonal-Zirconia Polycrystal Suspensions

2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA) was evaluated as a dispersant for nanosized 3-mol%-Y₂O₃-stabilized tetragonal-ZrO₂ polycrystal (3Y-TZP) suspensions. The adsorption of PBTCA was characterized using the decolorization method of ferric 5-nitrosalicylate complexes. Maximum adsorption of the dispersant on the 3Y-TZP powder was found to occur at pH 3.0. At pH >3.0, the adsorbed amount decreased with increased pH. Semiquantitative analysis using auger electron spectroscopy showed that PBTCA adsorbed irreversibly on the powder. The surface charge of the powder was evaluated by measuring the zeta-potential in dilute powder suspensions. The suspension was most effectively stabilized at high pH by the high charge induced by the adsorption of PBTCA. Rheological properties of the suspension were evaluated as a function of dispersant amount and solids loading. The optimum amount of dispersant increased with increased solids loading for solids loading >20 vol%. A stable suspension of 35 nm 3Y-TZP particles with a solids loading as high as 32 vol% was obtained using PBTCA as dispersant, in contrast to 28 vol% when using ammonium polyacrylate (NH₄PAA). Theoretical calculations of the interaction between 3Y-TZP particles showed that the stabilization of the suspensions was attributed to a combination of the electrostatic repulsion and a steric barrier caused by the adsorbed PBTCA. Induced coupling plasma analysis showed that PBTCA could be completely burned out during sintering, which confirmed its suitability as a dispersant for 3Y-TZP.     

Rheology of Concentrated Suspensions Containing Weakly Attractive Alumina Nanoparticles

The use of nanoparticles for the fabrication of new functional ceramics and composites often requires the preparation of concentrated fluid suspensions. However, suspensions containing nanoparticles are limited in solids content because of the excluded volume formed by the dispersant adlayer around the particles. We investigated the effect of the adlayer thickness on the rheological behavior of suspensions containing model alumina nanoparticles, using dispersant molecules with deliberately tailored chain length. The apparent viscosity and yield stress of the particle suspensions were markedly decreased by increasing the dispersant length, mainly due to a reduction of the attractive forces among particles. Fluid suspensions with solids content up to 35 vol% were prepared in toluene using a dispersant length of 2.5 nm. Our experimental results and viscosity predictions based on a hard sphere model indicate that fluid suspensions with up to 43 vol% of 65 nm alumina particles could be prepared using an optimum dispersant length of about 3.6 nm.