均一、单分散二氧化钛系列球形胶体颗粒的可控制备研究

TiO₂作为一种重要的半导体材料,具有光催化活性高、化学性质稳定、折射率高等特性,因而在光催化、陶瓷、涂料、化妆品及光电子器件等领域有着十分广泛的应用前景.尤其是近年来,核-壳结构的复合颗粒以及空心和介孔TiO₂胶体颗粒的出现,使TiO₂材料增添了许多独特的优异性能,相应研究成为热点.     

纳米Fe3O4/聚苯乙烯均匀分散体系的制备及结构

用化学共沉淀法制备了Fe3O4纳米颗粒,以油酸为表面活性剂,苯乙烯为载液,制备了稳定的纳米Fe3O4可聚合磁流体,将可聚合磁流体经自由基引发聚合制成纳米Fe3O4/聚苯乙烯均匀分散体系,用WAXRD研究了Fe3O4纳米粒子的结晶情况;用FTIR研究了油酸表面改性前后Fe3O4粒子表面官能团的变化;用TEM研究了Fe3O4颗粒的粒径大小及其在苯乙烯单体和聚苯乙烯中的分散情况;用DSC和TGA研究了纳米Fe3O4/聚苯乙烯均匀分散体系的玻璃化转变温度(Tg)和热稳定性,结果表明,合成的纳米Fe3O4为立方晶型,平均粒径在10nm左右,油酸分子在Fe3O4表面是化学吸附,经表面处理的Fe3O4超细颗粒在苯乙烯和聚苯乙烯基体中分散较均匀.界面粘结较好,含1.8％Fe3O4纳米颗粒的聚苯乙烯的最大热失重温度比聚苯乙烯提高了13K,Fe3O4/聚苯乙烯复合体系的饱和磁化强度σs为17.43emu/g.     

柠檬酸根对纳米Fe3O4颗粒的生长及性能的影响

现代诊断学的发展使得超小超顺磁性的Fe₃O₄粒子在医学领域具有重要应用价值。实验中利用某些羧酸盐对铁氧化物晶粒成长的抑制作用，在共沉淀法中引入柠檬酸根，制备出平均粒径小于5 nm的Fe₃O₄纳米分散体系。研究了不同柠檬酸根浓度对生成粒子的大小、结晶和表面吸附情况的影响。对Fe₃O₄颗粒在不同条件下的磁性与胶体稳定性进行了讨论。     

紫外光固化油墨中的颜料分散

１引言九十年代以来,印刷油墨行业受到来自环境保护的压力越来越大。辐射固化油墨（其中ＵＶ固化占９０％）的研究和应用出现了日新月异、迅猛发展的良好势头。紫外光固化油墨较之传统油墨固化迅速、能耗低,可用于对热敏感的基材,固化产品性能优越,最重要的是无溶剂挥发造成的环境污染,是面向二十一世纪的绿色工业技术！”。紫外光固化油墨中的颜料分散与传统油墨类似,但油墨本身成本高低与组分及其配比关系极大,其中如何选择颜料、分散助剂,如何调整分散工艺是控制成本的关键技术。１．１影响颜料分散的因素油墨中颜料分散的情况,…     

导数光谱法测定誊写油墨中蓝色颜料

蓝色誊写油墨中主要颜料有酞菁蓝和铁蓝.在一些案件中,对油印材料、图表中铁蓝和酞菁蓝的检验鉴定,可确定蓝色誊写油墨的牌号和产地,为侦破工作提供科学依据.有文献报道用原子吸收光谱法和X—射线粉末法测定油墨中铜、铁元素以区别酞菁蓝和铁蓝誊写油墨,但难以彻底排除油墨中填料的干扰.我们在办案中用导数光谱测定蓝色誊写油印制品,取得良好效果.该法具有快速、简便、灵敏、准确等特点,可广泛应用于油墨、涂料、纺织、塑料等有机化工产品中蓝色颜料的分析,为侦破工作、司法鉴定、产品质量监督等领域,提出了良好的检验方法.     

SiO_2包覆超细CaCO_3的微晶分析和XPS研究

0引 言 超细碳酸钙在橡胶、塑料、造纸、涂料、油墨、医药、化妆品等工业中有广泛应用。碳酸钙粉末表面具有许多水羟基,表面是亲水疏油性的 ,易形成聚集体 ,分散性能差 ,直接应用效果不好。因此,根据其本身的性质及其应用目的,对其进行表面处理,以相应提高其应用性能。碳酸钙的表面处理是通过物理或化学方法将表面处理剂吸附或反应在碳酸钙的表面,形成表面改性层,使其表面活性化,以改善碳酸钙的表面性能。目前碳酸钙的表面改性大多为有机表面改性、偶连剂表面改性、高分子（聚合物）表面改性等 [1],而无机表面改性却很少有报道。我…     

酸性离子液体催化合成二甘醇双丙烯酸酯

二甘醇双丙烯酸酯(Diethylene glycol diacrylate,简称DEGDA),是重要的丙烯酸多官能酯类单体之一,作为紫外光固化树脂的活性稀释剂,广泛用于光固化涂料、印刷油墨、感光树脂版、印刷线路版等领域[1].目前,合成DEGDA多用浓硫酸为催化剂,其反应底物一般可形成均相分散体系,有利于反应物间充分接触,反应速度快.缺点是浓硫酸的脱水性和强氧化性,导致反应中副反应多,设备腐蚀严重,大量"三废"的排放给环境保护造成极大的压力[2].     

均分散氯化氧铋胶体粒子制备

近年来均分散体系发展很快,在催化剂、功能陶瓷、传感器、超导体、涂料以及医药和化妆品等方面都有广泛的应用.Matijevic 等人曾对均分散体系制备作过系统研究,关键在于有效地控制晶核生长速率.我们曾对均分散体系制备作过多种研究.本文研制的BiOCl 均分散粒子可作为医药、化妆品方面的增白收敛剂、精细陶瓷的原料等.本工作是利用铋盐水解生成碱式铋盐沉淀.因此利用控制酸度抑制水解.水解时加入其它物质使其有效地控制品核生长.在水解过程中,我们加入烷基苯磺酸和硫酸钠来改变固液之间的界面性质,有利于晶核一次性生长和晶核稳定生成.     

WS2纳米颗粒的合成及摩擦学性能研究

将自制的WO₃纳米颗粒前驱体与S粉混合,在自制的反应装置氢气氛中,于550～750 ℃下煅烧得到二硫化钨纳米颗粒,反应中用H₂代替H₂S以减少对周围环境的污染。该合成路线简单且产物纯度高。用XRD、SEM、TEM和HRTEM对二硫化钨纳米结构进行了表征和分析,并将WS₂纳米颗粒作为添加剂添加到N40基础油中,在MS-T3000摩擦磨损仪测试其摩擦学性能。结果显示:制备的二硫化钨颗粒平均粒径在50 nm以内,其形状为球形或类球形。WS₂纳米颗粒作为普通润滑油的纳米级固体添加剂表现出了较优异的摩擦学性能。     

钛铁矿制备二氧化钛-四氧化三铁复合材料及其光催化应用

TiO_2因具有多种优异的特性被广泛应用在半导体光催化领域,但是纳米结构的TiO_2颗粒细微,在进行光催化反应之后,难以回收再利用。本文以廉价钛铁矿为原料制备光催化剂TiO_2,同时利用副产物铁合成Fe_3O_4,并采用简单温和的浸渍法制备Fe_3O_4/TiO_2磁性复合材料。通过XRD、FT-IR、SEM、EDS等手段对材料形态结构进行表征分析,并以光降解有机污染物若丹明B为探针反应,考察其光催化性能。结果表明,质量比为1∶10的Fe_3O_4/TiO_2复合材料结构稳定、分散均匀,具有最优的光催化活性(波长356nm下反应3h,若丹明B降解率达到64.0%),并表现出良好的重复性。同时,动力学结果显示降解符合一级反应动力学。     

Characterization of mineral oxide charging in apolar media

This paper presents an investigation of the charging behavior of mineral oxide particles dispersed in apolar media. There are a growing number of applications that seek to use electrostatic effects in apolar media to control particle movement and improve aggregation stability. Progress is limited, however, by incomplete knowledge of the mechanism(s) of particle charging in these systems. It has been shown in a number of cases that the acid-base properties of both the particles and the surfactants used to stabilize charge play key roles. A mechanism for acid-base charging has previously been established for mineral oxides in aqueous systems, where the surface hydroxyl groups act as proton donors or receivers depending on the pH of the surrounding solution. In water, the pH at which the surface charge density is zero, i.e., the point of zero charge (PZC), can be used to characterize the acid-base nature of the mineral oxide particles. The current work explores the possible extension of this charging behavior to apolar systems, with the key difference that the surface hydroxyl groups of the mineral oxides react with the surfactant molecules instead of free ions in solution. The apolar charging behavior is explored by measuring the electrophoretic mobility of a series of mineral oxides dispersed in a solution of Isopar-L and AOT, a neutral surfactant in water. The electrophoretic mobility of the particles is found to scale quantitatively, with respect to both sign and magnitude, with their aqueous PZC value. This provides support for the theory of acid-base charging in apolar media and represents a method for predicting and controlling particle charge of mineral oxides dispersed in apolar media.     

CONCERNING THE ORIGIN OF CHARGE AT THE POLYSTYRENE PARTICLE/WATER INTERFACE

The electrophoretic mobility behavior of well-characterized polystyrene latex particles, carrying one type of surface functional endgroups, has been studied as a function of pH. At low pH, the interaction of protons with the functional endgroups increased in the order: Hydroxyl > carboxyl > sulfate; at high pH the order of interaction was reversed; and at intermediate pH no interactions were observed. The particles of the polystyrene latexes in their different forms at the intermediate pH range, dispersed in deionized water, all exhibited the same mobility irrespective of the functional endgroup. The origin of charge in these systems is explained as being the result of either the preferential adsorption of hydroxyl ions or an electron - injection mechanism due to the overlap of local intrinsic molecular - ion states in polystyrene and water. At low concentrations of functional endgroups, the surface properties of the polystyrene latexes are largely dependent upon the hydrophobic nature of the surface.     

Surface grafting of polymers onto inorganic ultrafine particles: Reaction of functional polymers with acid anhydride groups introduced onto inorganic ultrafine particles

The surface grafting onto inorganic ultrafine particles, such as silica, titanium oxide, and ferrite, by the reaction of acid anhydride groups on the surfaces with functional polymers having hydroxyl and amino groups was examined. The introduction of acid anhydride groups onto inorganic ultrafine particle was achieved by the reaction of hydroxyl groups on these surfaces with 4-trimethoxysilyltetrahydrophthalic anhydride in toluene. The amount of acid anhydride groups introduced onto the surface of ultrafine silica, titanium oxide, and ferrite was determined to be 0.96, 0.47, and 0.31 mmol/g, respectively, by elemental analysis. Functional polymers having terminal hydroxyl or amino groups, such as diol-type poly(propylene glycol) (PPG), and diamine-type polydimethylsiloxane (SDA), reacted with acid anhydride groups on these ultrafine particles to give polymer-grafted ultrafine particles: PPG and SDA were considered to be grafted onto these surfaces with ester and amide bond, respectively. The percentage of grafting increased with increasing acid anhydride group content of the surface: the percentage of grafting of SDA (M_n = 3.9 × 10³) onto silica, titanium oxide, and ferrite reaching 64.7, 33.7, and 24.1%, respectively. These polymer-grafted ultrafine particles gave a stable colloidal dispersion in organic solvents.     

Rheological Behavior of Titanium Dioxide Suspensions

The rheological properties of titanium dioxide dispersed in water are measured over a wide range of powder concentrations, temperatures, and pH values. The value of intrinsic viscosity of titanium dioxide measured with an Ubbelohde capillary viscometer is 3.55, which is useful for determining the shape and aggregation property of the particles. The yield stress and steady shear viscosity of titanium dioxide with broad and narrow particle size distributions were measured over a wide range of solid volume fractions on a Brabender rheometer. It is observed that the rheological properties of the suspensions are quite different due to the difference in particle size distributions. Quemada, Casson, and Zhou's models were used to fit the experimental data and useful parameters were obtained. Calculated data are also in good agreement with the experimental data. As expected, the shear viscosity and yield stress decrease with increasing temperature. But when the temperature is around 50 degrees C, yield stress increases with increasing temperature while shear viscosity exhibits a complex behavior. The phenomena are very interesting and special. The Peclet number was used to analyze the shear thickening behavior. Models were also used to describe the shear viscosity under different temperatures and the master plots of the reduced variables eta/eta(infinity) vs t(c)gamma; at different temperatures are superimposed, which means the agreement is fair and the models are suitable to describe the rheological properties of titanium dioxide suspensions. pH effects were investigated on a Rheometrics RFS-II rheometer and it was found that pH can change the surface charge of the particles, which also affects the rheological behavior. The pH at which maximum shear viscosity and yield stress occur is in concordance with the isoelectric point. Copyright 2001 Academic Press.     

Enhancement of titanium dioxide photocatalysis by water-soluble fullerenes

Fullerenes are known for their unique electronic properties including high electron affinity. Although use of fullerenes for scavenging photo-generated electrons from titanium dioxide particles has been demonstrated, no attempts have been made to utilize the unique properties of fullerenes to increase the efficacy of photocatalysis. The present study has demonstrated that a mixture of water-soluble polyhydroxy fullerenes (PHF) and titanium dioxide (anatase polymorph) enhances photocatalytic degradation of organic dye. The PHF molecules adsorbed to the surface of titanium dioxide due to electrostatic forces, with adsorption density being higher at lower pH values. The surface coverage of titanium dioxide nanoparticles by PHF molecules determined the extent of enhancement, with an optimum dosed weight ratio of PHF to titanium dioxide at 0.001. Hydroxylation and concomitant solubilization of fullerenes allow their unique electronic properties to be harnessed for photocatalysis.     

pH-Dependent force spectroscopy of tri(ethylene glycol)- and methyl-terminated self-assembled monolayers adsorbed on gold

Self-assembled monolayers (SAMs) of methoxy-tri(ethylene glycol)- (EG(3)-OMe) and methyl-terminated alkanethiols (C(16)) adsorbed on polycrystalline gold were investigated by chemical force spectroscopy. Measurements were performed in aqueous electrolyte solutions depending on ionic strength and pH value. Charged and hydrophobic tips were employed as probes to mimic local patches of proteins and to study the interaction at the organic/liquid interface in detail. Force-distance curves reveal information about the origin of the observed interaction and the underlying mechanisms. The measurements confirm an effective negative surface charge to be present at the oligo(ethylene glycol) (OEG) and the methyl interface and suggest that the charges are due to the adsorption of hydroxyl ions from aqueous solution. pH-dependent measurements further support the robustness of the established charge associated with the OEG films. Its sign does not change over the whole range of investigated values between pH approximately 3.5 and approximately 10. In contrast, the hydrophobic self-assembled hexadecanethiol films on gold show an isoelectric point (IEP) around pH 4. While the mechanism of charge establishment appears to be similar for both SA films, the strength of hydrogen bonding to interfacial water, which acts as a template for hydroxyl ion adsorption, is likely to be responsible for the observed difference.     

An effective way to stabilize colloidal particles dispersed in polar and nonpolar media

This article offers a new approach to building up self-adjustable invertible polymer coatings at solid surfaces. The approach is based on a two-step process. In the first step, the surface of dispersed TiO2 has been functionalized with the aid of toluene diisocyanate (TDI) as a coupling agent. In the second step, the chains of amphiphilic oligoester have been covalently grafted to the titanium dioxide surface functionalized with isocyanate groups. It is shown that the titania modified in this way can form stable suspensions in both polar (water) and nonpolar (toluene) media. Multiple redispersion cycles show the ability of the modified titanium dioxide particles, after their removal from one type of dispersion and consequent drying, to be redispersed in dispersing media strongly differing by polarity from the previous.     

A rheological investigation of the self-assembly and adsorption behavior of a surfactant salt

The properties of a surfactant salt obtained by neutralizing oleic acid with an ethoxylated stearylamine were determined in blends of water and propylene glycol. The adsorption of this surfactant salt onto the surface of a commercial TiO(2) dispersed in blends of water and propylene glycol was studied using a rheometer. At low propylene glycol content the dispersions exhibited Newtonian behavior, but became shear-thinning fluids with high viscosity at propylene glycol contents above a critical concentration. The observed behavior is consistent with a model involving a surfactant bilayer below the critical point, moving to a monolayer above the critical point. The high viscosity above the critical point is generated by reversible flocculation via hydrophobic forces. The viscosity of the dispersion flocculated by the hydrophobic forces was found to be much higher than that caused by flocculation via van der Waals forces in the absence of surfactant. Changing both the total concentration of the surfactant in the dispersion and the dispersion temperature resulted in a reversible transition between the bilayer and the monolayer. Although the surfactant was always above its critical micelle concentration (CMC) the amount on the particle surface varied appreciably with both propylene glycol and surfactant concentration.     

Quantum chemical study of the mechanism of the catalytic oxyethylation of ethylene glycol on phosphorus-doped titanium dioxide: The role of the surface phosphoryl and hydroxyl groups of the catalyst

DFT calculations of the oxyethylation pathways of monoethylene glycol (MEG) and diethylene glycol (DEG) were performed on a model fragment of phosphorus-doped titanium dioxide (anatase). It was shown that the surface hydroxyl group of titanium dioxide, whose proton initiates C-O bond cleavage in the ethylene oxide molecule, plays the key role in the activation of the molecule. At the same time, the phosphoryl group -P(OH)₂O activates the reactant molecule R (MEG, DEG, etc.) and carries out the synchronous proton transfer from R to the hydroxyl oxygen atom of titanium dioxide, thus restoring the catalyst structure and closing the catalytic cycle. This restructuring occurs synchronously in one step. The substitution of the catalyst hydroxyl groups by alkoxyl groups can influence oxyethylation occurring via the bimolecular nucleophilic substitution mechanism and can poison the catalyst in some cases.     

Improving titanium dioxide dispersion in water through surface functionalization by a dicarboxylic acid

In this work, we show evidence of improving the dispersion of titanium dioxide particles in water. This is observed in the titanium dioxide-water colloid by the shear-thinning flow behavior in rheological measurements induced by the functionalization of a glutaric acid layer on the surface of titanium dioxide particles. The characterization of the layer was achieved by using infrared spectroscopy and ^13?C nuclear magnetic resonance. Rheological measurements corroborated that functionalization of TiO₂ particles decreases the rheological properties such as viscosity measurements at a constant shear rate in two orders of magnitude compared with the pure TiO₂ in suspensions. We present the results as a novel strategy to limit the formation of agglomerates in these colloidal suspensions, and this will be of great use in applications in the paints field and printing technologies.