三聚磷酸钠对水煤浆分散剂性能的影响

针对煤粉中含有的高价金属离子会降低水煤浆的成浆性问题,采用了三聚磷酸钠作为金属离子调节剂与几种阴离子型分散剂复配后,进一步提高分散降黏性能.通过测定分散剂在煤粒表面的吸附量、Zeta电位及吸附层厚度,揭示了三聚磷酸钠对脂肪族分散剂(SAF)、木质素系分散剂(GCL3S)及萘系分散剂(FDN)的分散协同增效作用机理.结果表明,三聚磷酸钠与SAF复配同时增加了煤粒之间的静电排斥力和空间位阻,使分散剂在煤粒表面的Zeta电位和吸附层厚度均增大;与GCL3S复配主要增加了煤粒之间的静电排斥作用;对FDN是通过增加分散剂在煤粒之间的空间位阻效应,促进分散降黏性能的提高.     

氨基磺酸系陶瓷分散剂在黑泥/水界面的吸附分散作用

氨基磺酸系陶瓷分散剂(ASP)与木质素磺酸钙(木钙)、萘磺酸盐甲醛缩合物(fdn)及磺化丙酮甲醛缩合物(saf)相比具有明显分散降黏效果。测定了四种分散剂在黑泥表面的吸附等温线及其对黑泥颗粒表面Zeta电位的影响,结果表明ASP既有较大的饱和吸附量,又能提高黑泥颗粒的Zeta电位,通过静电排斥和空间位阻协同作用表现出优良的分散性能。通过加入脲、氯化钠及柠檬酸钠研究了ASP在黑泥/水界面的吸附作用力,发现吸附过程的主导作用力是络合作用,同时氢键吸附也是重要的吸附作用力。     

三种水质对煤沥青水浆制备及性质的影响

以中温煤沥青为原料,采用冷冻粉碎方法制得具有一定粒度级配的煤沥青粉后,再加入适量分散剂与去离子水、自来水和焦化废水分别制备煤沥青水浆.考察了分散剂用量与煤沥青水浆流变性的关系,并对分散剂在煤沥青表面的吸附和Zeta电位进行了研究.研究表明,三种水均能制得浆体浓度为70%的煤沥青水浆,且浆体的表观黏度均随剪切速率的增加呈下降趋势.由去离子水、自来水和焦化废水制得煤沥青水浆的低位发热量、挥发分和灰分均达水煤浆Ⅰ级标准,硫分达Ⅱ级标准.三种水的分散剂溶液在煤沥青表面的吸附量和Zeta电位均随分散剂浓度的增加呈增大趋势,当分散剂浓度达到一定值后继续增加分散剂的浓度,吸附量和Zeta电位稍有下降,且吸附量和Zeta电位达到最大时对应的分散剂浓度基本相同.     

聚羧酸盐分散剂的亲疏水性对农药分散性能影响

[目的]研究聚羧酸盐分散剂的亲疏水性对农药分散性能影响。[方法]使用合成的不同亲疏水单体比例的甲基丙烯酸苯乙烯共聚钠盐(SSMA)作为分散剂制备莠去津悬浮液。使用TURBISCAN LAB稳定性分析仪、激光粒度仪、Zeta电位仪分别测定莠去津悬浮液的稳定性、平均粒径、Zeta电位,使用紫外-可见分光光度计测定SSMA在莠去津颗粒表面的吸附量。[结果]使用亲油(St)亲水(MAA)单体比例为1∶3的SSMA制备的莠去津悬浮液稳定性最好。莠去津悬浮液的Zeta电位值及SSMA在莠去津颗粒表面的吸附量均随SSMA中亲水单体(MAA)比例的增加而降低。[结论]聚羧酸盐分散剂的亲疏水性主要通过影响分散剂在农药颗粒表面的吸附量以及提供的静电斥力来影响农药悬浮液的稳定性。     

TiC—Ni粉体水系共悬浮

通过测定粉体Zeta电位、酸碱性和对分散剂PAA的吸附,探讨了TiC-Ni水系浆料的共悬浮。TiC粉体是酸性,等电点在PH值2.5处,并在PH值为9.5处出现Zeta电位最大值。TiC的Zeta电位随PAA浓度的增加而增加,并且对应于TiC对PAA的饱和吸附,Zeta电位增加到最大值,达到饱和吸附后,继续增加PAA的浓度反而导致Zeta电位的减小。Ni粉体呈碱性,通过理论分析,其等电点应在碱性区。当PAA的加入量为0.3wt％、pH值为6.5时单组分TiC浆料稳定,TiC-Ni浆料相对失稳;当PAA的加入量为0.2wt％、pH值为8.5时,TiC-Ni浆料稳定,并且沉降后的组分均一。     

聚羧酸盐侧链长度对水煤浆分散性能的影响及其作用机理

合成了一系列具有不同侧链长度的梳型聚羧酸盐(PC),研究了PC侧链长度对水煤浆的分散和流变性能的影响,使用X射线光电子能谱(XPS)分析了PC在煤水界面的吸附,并结合水煤浆Zeta电位及PC对煤颗粒的润湿性探讨了PC的分散作用机理,为设计制得高效的聚羧酸盐水煤浆分散剂提供依据。结果表明:长主链、短侧链和高阴离子基团含量的PC500(侧链聚合度)具有优良的分散性,所制水煤浆属假塑性流体。PC在煤表面呈单分子层吸附,其中PC500的吸附密度和吸附厚度均最大,分别为0.638 mg·m^-2和4.20 nm,其对煤粒润湿性也较好,所制水煤浆Zeta电位绝对值最高。侧链长度适中的PC500通过平衡吸附层厚度与Zeta电位发挥空间位阻和静电斥力作用分散水煤浆,其可有效地降低水煤浆Gibbs能,使煤粒间“团聚”减弱,浆体分散性提高。     

碳化硅基浆料的流变性能

研究了pH值、分散剂硅溶胶添加量、固含量对SiC基陶瓷浆料流变性能的影响.结果表明,与分散在水中的陶瓷粉体的Zeta电位相比,分散在硅溶胶中的陶瓷粉体的等电点向酸性方向漂移,且Zeta电位的负值绝对值都增加,这是由于吸附在陶瓷粉体表面的带负电荷的硅溶胶胶粒改变了陶瓷粉体表面的电荷状态.当pH值为11左右、硅溶胶添加量为10%(ω)时,浆料的粘度和剪切应力最小,流动性最佳;固含量达69%(ω)时,浆料呈现较强的触变性.     

两种不同羧酸单体的两性聚羧酸盐水煤浆分散剂的制备及性能对比

以烯丙基醇聚氧乙烯醚500（APEG-500）、羧酸单体 （丙烯酸和衣康酸）、二甲基二烯丙基氯化铵（DMDAAC）等为原料,合成了具有不同羧酸单体的两性聚羧酸盐水煤浆分散剂。采用FTIR、1HNMR对分散剂的结构进行表征,并结合水煤浆黏度、XPS、Zeta电位、接触角、稳定性等测试,讨论了不同羧酸单体对分散剂的分散性能的影响,探究了分散剂与煤粒表面的作用机理。结果表明：当DMDAAC用量为单体质量之和的6.0%时 ,两性聚羧酸盐分散剂对水煤浆的表观黏度降低效果优于阴离子型的聚羧酸盐分散剂;羧酸单体为衣康酸的分散剂性能更优,使陕西榆林煤最大固体质量分数达到66.5%,Zeta电位由-20.8 mV变化到-31.9 mV,吸附膜厚度和饱和吸附量分别为2.56 nm和3.23 mg/g,对煤粒的润湿性更好,浆体的稳定性显著提高,表明双羧基比单羧基更能提高分散剂性能。     

纳米氧化锌在水介质中的分散性能研究

纳米粉体的分散性能对提高分散体系的导热性能具有重要意义,试验选用纳米粒子在水介质中的Zeta电位和水合粒径来表征体系的分散稳定性,探讨不同分散剂种类及其浓度以及不同pH条件对ZnO水悬浮液稳定性的影响,并分析其作用机理.结果表明:Zeta电位与水合粒径有良好的对应关系,Zeta电位绝对值越高,水合粒径越小,表明体系分散稳定越好.pH值、分散剂种类及加入量是影响纳米ZnO水相体系分散稳定性的主要因素,不同的分散剂最佳分散条件不同.在 0.1% ZnO-H2O纳米流体中,在 pH=11.4,加入 0.05%十二烷基苯磺酸钠(SDBS)分散剂,悬浮液的稳定性最佳.     

不同降解方式对淀粉基水煤浆分散剂性能的影响

分别采用氧化法(H₂O₂为氧化剂)、酸解法(HCl)两种不同的方式制备降解淀粉,在相同的实验条件下,以丙烯酸(AA)、苯乙烯磺酸钠(SSS)为单体,H₂O₂-Fe²⁺为引发剂,通过自由基聚合反应制备3种淀粉基水煤浆分散剂。通过红外光谱(FTIR)、核磁共振氢谱(¹HNMR)、凝胶渗透色谱(GPC)对产物的分子结构、相对分子质量及分布进行了表征和分析。将3种分散剂应用于彬长煤制浆,考察对比了浆体的表观黏度、分散剂最佳添量、最大制浆浓度、流变性、Zeta电位、吸附特性及静态稳定性等。结果表明,经氧化降解制备的淀粉基水煤浆分散剂在最佳添加量0.4%(质量分数)时,水煤浆最大制浆浓度可达到67%,表观黏度为906mPa·s,煤粒表面的Zeta电位由–12.1mV变化到–47.3mV,相较于由玉米淀粉及酸降解淀粉制备的水煤浆分散剂对彬长煤具有更好的降黏、分散、稳定作用。     

萘磺酸盐甲醛缩合物在灭幼脲界面的吸附特性研究

利用残余质量浓度法、ζ电位测定和IR法研究了萘磺酸盐甲醛缩合物分散剂在灭幼脲颗粒界面的吸附量、吸附状态、ζ电位、吸附作用力等性能。分析认为,萘磺酸盐甲醛缩合物分散剂在灭幼脲颗粒界面吸附后具有静电排斥和空间位阻双重作用,这对维持灭幼脲水悬浮剂的分散稳定性具有重要意义。     

SAS/MAA/MPEGMAA聚羧酸盐分散剂的制备与性能

以甲基丙烯酸（MAA）和 4 种不同侧链长度的甲氧基聚乙二醇（MPEG相对分子质量分别为350,500,750,1000）先聚合得到酯化大单体（MPEGMAA）,再以甲基丙烯酸,烯丙基磺酸钠（SAS）为单体,在引发剂过硫酸钾,阻聚剂对苯二酚作用下聚合得到 4 种具有不同侧链长度的聚羧酸盐分散剂。通过红外（FT-IR）、核磁共振氢谱（¹H NMR）和凝胶渗透色谱（GPC）对聚合物的结构、相对分子质量及其分布进行了表征和分析,并将其作用于彬长煤制浆,考察了浆体的表观黏度、流变性、zeta电位、吸附性以及最大成浆浓度和稳定性,测定其与煤的接触角,并通过X射线光电子能谱（XPS）分析,得出煤粒表面吸附分散剂后的吸附层厚度为 6.12 nm。结果表明,侧链长度为SAS/MAA/MPEGMAA750的聚羧酸盐分散剂具有良好的润湿和吸附效果,对彬长煤具有更好的降黏、分散和稳定作用。     

Dispersion and densification of nano Si–(Al)–C powder with amorphous/nanocrystalline bimodal microstructure

The dispersion behavior and densification of nano Si–(Al)–C powder with amorphous/nanocrystalline bimodal microstructure were investigated. The Si–C powders synthesized by a mechanical alloying (MA) process had a near‐spherical shape with an average particle size of 170 nm. A solid loading of 62 vol% was achieved using polyethyleneimine (PEI) as a dispersant. The optimum dispersant amount was 1 wt% based on zeta potential, sedimentation, and viscosity analysis data. The high zeta potential value (73 mV) compared with that of the commercially available SiC (65 mV) was caused by modified surface properties and consequent promotion of the cationic dispersant adsorption. A Si–Al–C slurry containing 6.5 wt% of sintering additives with a solid loading of 60 vol% was also prepared. The relative density of the dried Si–Al–C slurry was 63.3% without additional compaction, which could be densified at 1650°C at a pressure of 20 MPa using a spark plasma sintering furnace.     

Stabilization of raw porcelain gres suspensions with sodium naphthalene sulfonate formaldehyde condensates

The stabilization of raw porcelain gres suspensions with sodium naphthalene sulfonate formaldehyde condensates (SNSFC) was examined systematically in order to understand the basis mechanism of dispersion. Small additions of SNSF to the classical deflocculating mixture with sodium silicate were tested. The repulsion between the colloidal particles was correlated with the adsorption isotherm and zeta potential. The naphthalene sulfonate condensates were effective as dispersant for raw porcelain gres suspensions. The efficiency of these dispersant was attributed to electrostatic effect between the colloidal particles. The ability of the SNSFC to stabilise stabilize raw porcelain gres suspensions was not affected by the degree of condensation.     

Effects of Solvent Mixtures on Dispersion of Lanthanum-Modified Lead Zirconate Titanate Tape Casting Slurries

The effects of xylenes/ethanol solvent mixtures on lanthanum-modified lead zirconate titanate (PLZT) nonaqueous suspensions were investigated by measuring sediment height, viscosity, and adsorption of dispersant. Well-dispersed colloidal suspensions were obtained in xylene-rich solvents with a minimum amount of menhaden fish oil as a dispersant. It was also shown that adsorption of dispersant on particle surfaces strongly depends on selection of solvent(s). The ratio of solvent mixture affects PLZT solids content of unfired tapes, in which using insufficient as well as excess dispersant could decrease the packing density of particles. Solubility of other organic additives, such as binder, was also considered when selecting a xylene/ethanol ratio.     

苯乙烯-甲基丙烯酸钠共聚物在吡虫啉颗粒表面的吸附特性

通过溶液聚合合成一系列苯乙烯-甲基丙烯酸钠共聚物分散剂.研究了不同单体摩尔比对其产率和在吡虫啉颗粒表面吸附性能的影响,结果表明当两种单体摩尔比为0.8时分散剂的产率和吸附性能相对最优.通过振荡吸附实验研究了最优分散剂在吡虫啉颗粒表面的吸附动力学、等温线和热力学,由XPS近似计算不同温度下分散剂的吸附层厚度.结果表明:吸附动力学符合伪二级动力学方程;吸附等温线符合Langmuir模型;吸附热力学表明该吸附为自发、放热、熵增过程,高温不利于吸附进行;DH_ad < 40 kJ·mol^-1表明该吸附过程为物理吸附;吸附层厚度随温度升高而降低.通过与其他商品化分散剂对比可知该共聚物适合作为分散剂用于吡虫啉的水基化剂型.     

Dispersant-Binder Interactions in Aqueous Silicon Nitride Suspensions

The interaction of dispersant and binder on the surface of particles was studied to identify the effect of these additives on aqueous ceramic powder processing. Poly(methacrylic acid) (PMAA) and poly(vinyl alcohol) (PVA) were used as the dispersant and binder, respectively. The adsorption isotherms of the organic additives on silicon nitride were determined. The adsorption of PMAA was differentiated from PVA in the mixed additive system via ultraviolet spectroscopy. The electrokinetic behavior of silicon nitride was measured by using an electrokinetic sonic amplitude analyzer. As the PMAA concentration increased, the isoelectric point (pH_iep) of silicon nitride shifted from pH 6.7 ± 0.1 to acidic pH values. The magnitude of the shift depended on the surface coverage of PMAA. PVA did not affect the pH_iep of suspensions but did cause a moderate decrease in the near-surface potential. Finally, the rheological behavior of silicon nitride suspensions was measured to assess the stability of particles against flocculation in aqueous media; this behavior was subsequently correlated with the electrokinetic and adsorption isotherm data.     

聚羧酸盐分散剂在吡虫啉颗粒表面的吸附特性

通过测定吸附量、吸附层厚度和傅里叶红外光谱研究聚羧酸盐分散剂Tersperse 2700在农药吡虫啉颗粒表面的吸附热力学、动力学、吸附作用力和吸附形态。热力学和动力学研究结果表明:吸附等温线符合Langmuir模型,随温度升高Langmuir常数和饱和吸附量明显降低,由ΔG_ad<0、ΔH_ad<0、ΔS_ad>0可知该吸附为自发、放热、熵增过程,结合吸附层厚度随温度升高而降低的现象可认为高温不利于该吸附进行;吸附动力学符合Lagergren方程,半饱和吸附时间随温度升高而降低表明该吸附速率随温度升高而增加,该吸附过程的表观活化能E_a为12.62 kJ·mol^-1,表明该吸附为物理吸附。吸附作用力和吸附形态研究结果表明:分散剂2700在吡虫啉颗粒表面的吸附作用力以范德华力为主;吸附形态为单层多点式吸附,通过建立假设吸附模型认为分散剂2700以空间位阻效应和静电斥力效应共同维持在吡虫啉颗粒表面的吸附稳定性。     

Influence of pH and Ionic Impurities on the Adsorption of Poly(acrylic) Dispersant onto a Zinc Oxide Surface

We have studied the properties of aqueous suspensions of ZnO powders with different purities. Our results suggest that powder purity determines the amount of dispersant necessary to form a stable aqueous suspension as well as the maximum adsorption capacity of the dispersant: the higher the positive surface charge of the as-received ZnO powders, the higher the amount of dispersant adsorbed onto the metal oxide surface. The surface charge of the ZnO particles in suspension is affected by the concentration of zinc as well as sulfate ions, which are the major impurities in the supernatant. The pH of the aqueous ZnO suspensions increases with increasing concentration of poly(acrylic) dispersant until the maximum adsorption capacity is attained. Further additions of dispersant do not increase the pH because of a buffer formation with impurity ions.     

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.