纳米碳酸钙在水中的分散

筛选出了适合于在水中分散的纳米碳酸钙，分别考察了分散机转速、分散剂种类、分散剂用量、分散时间和悬浮液浓度等因素对纳米CaCO3在水中分散的影响，优化出了纳米CaCO3在水中分散的工艺条件，即：转速为7500r／min，分散剂为PK-100，分散时间为1．5h，分散剂用量为纳米CaCO3质量的3％，悬浮液浓度为15％．结果表明，优化条件下所制得的悬浮液黏度较低，纳米CaCO3平均粒径较小，分散均匀，且贮存稳定性良好．添加了该纳米CaCO3浆液的复合建筑涂料的耐沾污性、耐洗刷性、触变性、耐水性、耐碱性和耐老化性等得到了显著改善．     

纳米CaCO_3的制备、表面改性及表征

主要进行了超重力法制备纳米碳酸钙及纳米碳酸钙的表面改性工作 ,并应用TEM、BET、XPS和接触角等方法对改性前后的纳米碳酸钙进行了分析和表征。未改性纳米碳酸钙的粒径约为 30nm ,而改性之后粒子的粒径约在 35～40nm之间 ;未改性纳米碳酸钙的比表面积为 2 9.8m2 / g ,改性碳酸钙的比表面积 38.4m2 /g ,有较大程度的增大 ;改性碳酸钙的XPS能谱图中Ca2 + 的结合能改变了 0 .35eV ,表明改性剂以化学键结合于碳酸钙表面 ;改性剂加入量在 6 % (质量分数 )时改性CaCO3 与极性溶剂的接触角发生反转 ,说明改性剂适宜加入量应在 6 %左右     

阴离子型水性超分散剂的制备及其表征

根据超分散剂作用机理及结构设计原则，以马来酸酐、正丁醇、丙烯酸为原料，过硫酸铵为引发剂，通过先酯化后共聚的方法，制备出低相对分子质量的水溶性超分散剂。通过红外光谱（FT-IR）对聚合物的结构进行表征，运用乌氏黏度法测定其相对分子质量．用合成的超分散剂对纳米二氧化钛、纳米碳酸钙进行了分散稳定性的研究，发现该超分散剂能使纳米二氧化钛在水溶液中稳定分散1152h以上，使纳米碳酸钙悬浮液的黏度降低到接近水的黏度．该超分散剂能有效的分散超细粒子．     

纳米CaCO3改性及其在环氧改性丙烯酸底漆中的应用

采用复合改性剂对纳米CaCO3进行改性,探讨了改性剂用量、乳化温度、乳化时间和保温时间等因素对纳米CaCO3改性的影响,并优化了最佳操作工艺条件:改性剂用量为4.83%(质量分数)纳米CaCO3、乳化温度为80℃、乳化时间为40min和保温时间为60min.测定了改性和未改性纳米CaCO3的活化指数、吸油量、沉降体积及其在邻苯二甲酸二辛酯(DOP)中的糊粘度,并用红外光谱对改性和未改性纳米CaCO3进行了表征,结果表明改性纳米CaCO3的亲油性显著提高.制备了纳米CaCO3复合环氧改性丙烯酸底漆,与传统底漆相比其耐水性、耐盐水性和耐盐雾性显著改善.     

纳米碳化硅颗粒的团聚及分散的研究进展

介绍了微粒团聚机理、团聚类型及其区别;在介绍软团聚处理方法的基础上,综述了pH值、悬浮液黏度及分散剂类型对纳米碳化硅分散效果的影响;阐述了自然碳化硅的带电状态、化学成分及其表面改性情况;在列举了添加分散剂前后纳米碳化硅等电点(IEP)的基础上,重点分析了一种新的分散剂—甲苯酰-聚乙烯亚胺的分子结构及工作原理,同时从吸附量、悬浮液黏度及Zeta电位三个方面与传统分散剂作了对比;最后,根据人们对团聚机理的认识及纳米碳化硅分散的研究现状,在未来的研究中不仅要侧重于纳米碳化硅性质、颗粒微观结构的研究,而且要注重纳米碳化硅的工业生产和制备以及分散剂的优化。     

针形纳米碳酸钙的表面改性及在PVC中的应用

对自制直径为30 nm~40 nm,长径比10~15的针形纳米碳酸钙进行表面改性后,将其应用于聚氯乙烯(PVC)的改性研究中,考察了改性针形纳米碳酸钙/PVC复合材料的力学性能。与未填充的PVC相比,纳米碳酸钙填充量为2.69%(体积分数)时,复合材料的拉伸强度、冲击强度和断裂伸长率分别提高了5.7%、11.3%和33.7%。改性后的纳米碳酸钙与PVC之间的界面作用与未改性碳酸钙相比有所减弱。扫描电镜照片(SEM)显示,添加了改性针形碳酸钙的聚氯乙烯断裂为韧性断裂,冲击断面呈现明显的拉丝现象。     

纳米碳酸钙湿法表面改性的研究

利用季铵型阳离子表面活性剂对纳米碳酸钙进行了湿法表面改性。对湿法改性前后的纳米碳酸钙进行了红外光谱(FTIR)、X射线衍射(XRD)及透射电镜(TEM)分析。采用Zeta电位、分散体系浊度、沉降体积、表观粘度等分析方法对改性前后纳米碳酸钙在水中的界面行为进行评价。另外,通过激光粒度仪对改性前后纳米碳酸钙分散液的粒度分布进行了测定。实验结果表明,经湿法表面改性后,纳米碳酸钙在水中的润湿性及分散性有很大改善。     

纳米CaCO3在环氧树脂中的分散及其复合涂料的制备

采用正交试验法研究了纳米CaCO3在环氧树脂中的分散工艺,制备了纳米CaCO3复合环氧树脂浆液。探讨了分散剂种类,环氧树脂、纳米CaCO3和分散剂的用量等因素对纳米CaCO3在环氧树脂中分散性的影响,并优化出最佳分散工艺条件:环氧树脂25g、纳米CaCO345g和分散剂BYK110为3g。考察了纳米CaCO3复合环氧浆液的贮存稳定性,结果表明,优化条件下制得的纳米CaCO3浆的稳定性好,3周内外观、粘度和细度均无变化。并用该浆液制成的纳米复合涂料,与传统涂料相比其耐水性、耐盐雾性和贮存稳定性等显著改善。     

聚乙二醇改性煤沥青半焦结构及其性能研究

以聚乙二醇-200和聚乙二醇-400为改性剂、对甲苯磺酸为催化剂对煤沥青进行改性,研究改性煤沥青的化学性质、成焦的晶体结构和显微结构。结果表明,改性后的煤沥青β树脂含量提高了51.90%-55.18%,芳核的缩合度和骨架振动吸收频率显著增大;改性反应主要发生在芳环的氢位上。在800℃时的残炭率比未改性煤沥青增加了18%;此外,在低于160℃时,经聚乙二醇-400改性后的煤沥青黏度低于同温度下未改性的煤沥青黏度,而经聚乙二醇-200改性的煤沥青黏度则高于同温度下未改性的煤沥青黏度。经聚乙二醇-200改性的沥青所制半焦纤维组织结构明显改善;其有序性和堆积高度也显著提高。     

ZrO2(n)/SiC(n)-MoSi2纳米复合陶瓷中纳米颗粒的均匀分散

本文探讨了在pH值一定的情况下,不同分散剂、不同分散介质对纳米ZrO2、纳米SiC的分散效果的影响,并考察了不同表面处理方法对纳米SiC颗粒分散性的影响.研究结果表明:以PEG为分散剂、水为分散介质可以有效地分散纳米ZrO2和纳米SiC,并能与基体MoSi2粉末均匀混合;采用550℃、2h的煅烧工艺处理纳米SiC可有效改善其分散性.     

Rheology,fiber distribution and mechanical properties of calcium carbonate (CaCO3) whisker reinforced cement mortar

Calcium carbonate (CaCO₃) whiskers are a new kind of microfiber used in cementitious composites and have proved to provide excellent effect on strengthening and toughening. In order to further improve the mechanical properties of CaCO₃ whisker-reinforced cementitious composites, rheological properties of fresh mixtures and the CaCO₃ whisker distribution in the hardened matrix were investigated. The yield stress and plastic viscosity increased with an increasing content of CaCO₃ whisker and a decreasing water-cement ratio. Also, the rheological properties were affected by the distribution of CaCO₃ whisker in the matrix. The largest increments in flexural and compressive strength were 27.59% and 12.60% for the mortars with CaCO₃ whisker contents of 2.0% and 1.5%, respectively. The properties responsible for the mechanical response were explained in terms of the effects of CaCO₃ whisker reinforcement, the distribution of CaCO₃ whiskers, and the porosity as well as pore size distribution.     

Characteristics evaluation of calcium carbonate particles modified by surface functionalization

Calcium carbonate (CaCO₃) particles were modified by a direct blending method using different coupling agents. The changes in the CaCO₃ particles were determined using different techniques. Compared with pristine particles, the modified CaCO₃ particles show good dispersion, particularly those modified by γ-methacryloxypropyl trimethoxy silane. Results of the thermogravimetric analysis indicated that the coupling agents were adsorbed or anchored on the surface of the CaCO₃ particles, thereby hindering aggregation. The formation of covalent bonds [CaOSi] or [CaOTi] was verified using Fourier transform infrared spectroscopy and X-ray diffraction. The modified CaCO₃ particles showed more stable colloidal dispersion in ethyl acetate than that of pristine CaCO₃ particles. Some silane or titanate coupling agents can be combined with CaCO₃ by covalent bonds, thereby changing the surface properties of CaCO₃ and enhancing dispersion in many organic media. The hydroxyl groups on the surface of CaCO₃ particles can interact with silanol groups or titanate coupling agents forming an organic coating layer.     

Physical and mechanical properties of SEBS/polypropylene nanocomposites reinforced by nano CaCO3

In present study, styrene‐b‐(ethylene‐co‐butylenes)‐b‐styrene triblock copolymer (SEBS) and polypropylene (PP) are prepared. This mixing is followed by adding 3, 5 and 10 wt% of nano CaCO₃. The morphology and thermal behavior of PP/SEBS/nano‐CaCO₃ compounds are characterized by different methods. Scanning electron microscopy micrographs of cryo‐fractured PP/SEBS/nano‐CaCO₃ nanocomposites show that with increasing nano‐CaCO₃ loading, the aggregation becomes worse. However, followed by adding 5 wt% nano‐CaCO₃ into PP/SEBS nanocomposites, nano‐CaCO₃ is homogeneously dispersed in PP matrix. The photomicrograph of transmission electron microscopy confirms that SEBS/PP/nano‐CaCO₃ nanocomposites are formed, as low aggregations of calcium carbonate were well‐dispersed in polymer matrix. With a rise in nano‐filler content, the tensile and impact strength of PP/SEBS/CaCO₃ nanocomposite are fixed while the elastic modulus of PP/SEBS nanocomposites increases followed by adding nano‐CaCO₃ to polymer blend, which could be due to the acceptable nano‐CaCO₃ dispersion quality.     

The influences of particle–particle interaction and viscosity of carrier fluid on characteristics of silica and calcium carbonate suspensions-coated Twaron® composite

The effects of particle–particle interaction and viscosity of carrier fluid on steady and dynamic rheological responses and quasi-static penetration resistance of Twaron® fabrics treated with shear thickening and shear thinning suspensions have been investigated. The suspensions have been made by mechanically dispersing 60 nm silica (SiO₂) and calcium carbonate (CaCO₃) nanoparticles in poly ethylene glycol (PEG) with molecular weights of 200 and 400 g/mol. The CaCO₃ suspensions display shear thinning behaviour along with the total dominance of the elastic state over the viscous state while the SiO₂ suspensions exhibit shear thickening behaviour with the emergence of both the elastic and viscous states. With the increase of molecular weight of PEG, viscosity, viscoelastic modules and instability of the suspensions increase and critical shear rate and frequency of transition to elastic state diminish. The PEG200 and PEG400-contained SiO₂ suspensions-treated Twaron® composites at 35 wt.% have quasi-static penetration resistances which are nearly 2.63 and 2.48 times and maximum absorbed energies which are about 1.54 and 1.55 times higher, respectively, than those of the corresponding CaCO₃ ones. However, the influence of increasing the PEG's molecular weight is not as considerable as the effect of particle–particle interaction on the enhancement of penetration resistance performance.     

Thermal and morphological characterization of poly(ethylene terephthalate)/calcium carbonate nanocomposites

Nanocomposites composed of poly(ethylene terephthalate) (PET) filled with calcium carbonate particles of nanometer scale were prepared by polymerizing the polyester in the presence of the nanosized fillers. Besides plain calcium carbonate, carbonate nanoparticles coated with stearic acid were also used, in order to improve the compatibility between the polymeric matrix and nanofillers. Morphological analysis evidenced a good dispersion of both the nanopowders into the PET matrix, especially in the case of coated calcium carbonate. The strong interfacial adhesion between the two phases is also responsible for the increase of the glass transition and melting temperatures in the nanocomposites compared to plain PET. Finally, non-isothermal crystallization studies revealed that the coated CaCO₃ is a good nucleating agent for PET. Analysis of non-isothermal crystallization data with the Ozawa theory was successful for plain PET and PET/un-CaCO₃, but this method failed to describe the dynamic solidification of the PET/c-CaCO₃ nanocomposite.     

A comparative study of the effect of different rigid fillers on the fracture and failure behavior of polypropylene based composites

Polypropylene (PP) composites with 5 wt% of different rigid particles (Al₂O₃ nanoparticles, SiO₂ nanoparticles, Clay (Cloisite 20A) nanoparticles or CaCO₃ microparticles) were obtained by melt mixing. Composites with different CaCO₃ content were also prepared. The effect of fillers, filler content and addition of maleic anhydride grafted PP (MAPP) on the composites fracture and failure behavior was investigated. For PP/CaCO₃ composites, an increasing trend of stiffness with filler loading was found while a decreasing trend of strength, ductility and fracture toughness was observed. The addition of MAPP was beneficial and detrimental to strength and ductility, respectively mainly as a result of improved interfacial adhesion. For the composites with 5 wt% of CaCO₃ or Al₂O₃, no significant changes in tensile properties were found due to the presence of agglomerated particles. However, the PP/CaCO₃ composite exhibited the best tensile behavior: the highest ductility while keeping the strength and stiffness of neat PP. In general, the composites with SiO₂ or Clay, on the other hand, displayed worse tensile strength and ductility. These behaviors could be probably related to the filler ability as nucleating agent. In addition, although the incorporation of MAPP led to improved filler dispersion, it was damaging to the material fracture behavior for the composites with CaCO₃, Al₂O₃ or Clay, as a result of a higher interfacial adhesion, the retardant effect of MAPP on PP nucleation and the lower molecular weight of the PP/MAPP blend. The PP/MAPP/SiO₂ composite, on the other hand, showed slightly increased toughness respect to the composite without MAPP due to the beneficial concomitant effects of the presence of some amount of the β crystalline phase of PP and the better filler dispersion promoted by the coupling agent which favor multiple crazing. From modeling of strength, the effect of MAPP on filler dispersion and interfacial adhesion in the PP/CaCO₃ composites was confirmed.     

Dispersion of CaCO3 nanoparticles by sonication and surfactant treatment for application in fly ash–cement systems

This research aims to offset the negative effects of fly ash on the early-age properties of cementitious materials with the use of calcium carbonate (CaCO₃) nanoparticles. The main focus is to enhance the effect of the nanoparticles by improving dispersion through ultrasonication and use of surfactants. CaCO₃ aqueous suspensions with various surfactant types and concentrations are prepared and subjected to different sonication protocols (varying duration and amplitude). Dispersion and stability are quantitatively measured by comparing their absorbance spectra through spectrophotometry and qualitatively evaluated through SEM imaging. The effectiveness of sonicated CaCO₃ nanoparticle additions in accelerating setting and improving early-age compressive strength gain of fly ash–cement pastes is investigated. The sonication protocol is optimized and the most effective dispersion is achieved with polycarboxylate-based superplasticizer. Good agreement is found between the dispersion measurements and mechanical performance.     

Modification of rheological and filtration characteristics of water‐based mud for drilling oil and gas wells using green SiO2 @ZnO@Xanthan nanocomposite

In this study, a green, simple and economical approach was used to synthesise the SiO₂ @ZnO@Xanthan nanocomposite (NC) to modify the rheological and filtration characteristics of the water‐based drilling mud. The green synthesised NCs were identified using scanning electron microscopy, energy dispersive X‐ray spectroscopy, elemental mapping, X‐ray diffraction and UV–Vis analytical techniques. Additionally, the effect of SiO₂ @ZnO@Xanthan NCs on the filtration and rheological properties of mud including apparent viscosity, plastic viscosity, yield point, gel strength, mud cake and fluid loss was investigated. The obtained results confirmed that the synthesised NCs effectively improved the rheological properties of drilling mud, and considerably decreased its fluid loss and filter cake by about 54 and 92.5%, respectively. The results highly recommend the SiO₂ @ZnO@Xanthan NC as an excellent additive to improve the rheological properties, and reduce the fluid loss and the filter cake of the drilling mud.Inspec keywords: X‐ray diffraction, scanning electron microscopy, nanofabrication, additives, nanocomposites, X‐ray chemical analysis, drilling (geotechnical), yield point, rheology, filtration, industrial economics, silicon compounds, zinc compounds, ultraviolet spectra, visible spectra, nanofluidics, gelsOther keywords: rheological properties, fluid loss, drilling mud, filtration characteristics, water‐based mud, green approach, economical approach, X‐ray spectroscopy, mud cake, apparent viscosity, oil‐gas wells, nanocomposite synthesis, scanning electron microscopy, energy dispersive X‐ray spectroscopy, elemental mapping, X‐ray diffraction, Uv–Vis spectroscopy, plastic viscosity, yield point, gel strength, additive, SiO₂ , ZnO     

Dispersion effect and auto-reconditioning performance of nanometer WS<Subscript>2</Subscript> particles in green lubricant

This paper reported on dispersion effect and dispersing techniques of nanometer WS₂ particles in the green lubricant concocted by us. And it also researched on auto-reconditioning performance of nanometer WS₂ particles to the abrasive surfaces of steel ball from four-ball tribology test and piston ring from engine lubrication test. The treated and untreated nanometer WS₂ particles were analysed by infrared spectrum. And the elementary component and interior elementary distribution of abrasive surface repaired by nanometer WS₂ particles were analysed by multifunction electron spectrometer. The results showed that the combinative method of ultrasonic dispersion, mechanical agitation and surface modification could improve the dispersion uniformity and stability of nanometer WS₂ particles in the green lubricant effectively. And the optimal ratio of the mass between surface modifier and nanometer WS₂ particles was 1: 2.5, the optimal treating time was 5 h. And IR analysis indicated that surface modifier could react with hydroxide radicals on surfaces of WS₂ particles and modify the surfaces, and the long lipophilic groups on surfaces of nanometer WS₂ particles could stretch in oil adequately and form steric hindrance layers between particles which prevented particles from conglomerating and depositing. In addition, tribological tests and surface analysis indicated that there were WS₂ adsorption film and reaction film on abrasive surfaces during the tribological tests, which could fill and level up the furrows on abrasive surfaces. As a result, the abrasive surfaces were repaired effectively by nanometer WS₂ particles.     

Formation and characterization of dispersive Mg substituted CaCO3

Dispersive Mg substituted CaCO₃ particles were synthesized via the modified carbonation method in which MgCl₂ was added into the Ca(OH)₂ suspension. The influence of MgCl₂ on the morphology, dispersion, composition and structure of the carbonation product was investigated. The experimental results indicated that the addition of MgCl₂ in the slaking step converted the agglomerated Ca(OH)₂ to the dispersive slurry containing Mg(OH)₂ and CaCl₂, the carbonation of the resulting slurry led to the formation of the dispersive Mg substituted CaCO₃.