L-赖氨酸接枝纳米碳酸钙的合成

纳米CaCO_3浆液中加入L-赖氨酸,在其表面引入羧基、氨基等活性基团实现表面改性,利用FTIR、XRD、SEM和TGA等手段对改性机理进行研究。结果表明:L-赖氨酸是以化学键合的形式接枝到纳米CaCO_3表面,改性后的纳米CaCO_3分散良好,晶面间距增大;L-赖氨酸接枝纳米CaCO3最佳工艺条件为:料浆CaCO_3中质量分数为8%~10%,L-赖氨酸与纳米CaCO_3质量比为0.1,改性温度70℃,时间70 min;优化工艺条件下,改性纳米CaCO_3的活化度为46.3%。     

Synthesis of carbon hollow particles by a simple inverse-emulsion method

Morphology-controlled carbon hollow particles have been successfully prepared via carbonization of the resorcinol-formaldehyde (RF) hollow particles synthesized from O/W/O inverse-emulsion system. Various morphologies of carbon hollow particles such as hollow spheres, bowl-like structure, and capsules were tailored by adjusting the pH values of RF precursor. The obtained carbon hollow particles exhibited similar microporous properties with specific surface areas of 526-659 m² g^− 1 and pore volumes of 0.26-0.43 cm³ g^− 1. Based on these results, it was proposed that the low initial pH value of RF precursor and the stability of inverse-emulsion system were crucial in fabricating morphology-controlled carbon hollow particles.     

Preparation of submicrometer-sized titania hollow spheres by templating sulfonated polystyrene latex particles

Submicrometer-sized titania hollow spheres with tunable shell thickness and smooth surfaces have been successfully synthesized by employing sulfonated polystyrene (PS) latex particles as a template in sol-gel method. The structure of the particles was characterized by scanning electron microscopy and transmission electron microscopy. The shell thickness was readily tuned by altering the concentration of titanium tetrabutoxide (TBOT) in ethanol solutions. The surface roughness as well as the shell thickness has the tendency to increase with the increase in the concentration of TBOT. The diameter of the hollow spheres was on the average of 20-26% smaller than the diameter of template PS latex particles. Some titania fragments were also observed for the sample with the highest TBOT concentration.     

Synthesis of ultra-small hollow silica nanoparticles using the prepared amorphous calcium carbonate in one-pot process

The ultra-small hollow silica nanoparticles were synthesized using the prepared amorphous calcium carbonate (ACC) particles as a template. The ACC particles were firstly prepared by carbonation method, which procedure was conducted in the methanol solvent to form the Ca(OCH₃)₂ layers on the ACC particles. An effect of methanol concentration on the morphology of ACC particles was also investigated. The prepared ACC particles were directly coated by silica through adding tetraethoxysilane (TEOS) into the methanol solvent. Hence, the ACC-silica core-shell particles were obtained since the ACC particles have a positive charge and interact with hydrolyzed TEOS. The ACC particles could be stabilized through the reaction between methanol and calcium ions when the methanol concentration was increased over than 40?vol%.     

Synthesis of hollow structural hydroxyapatite with different morphologies using calcium carbonate as hard template

Hydroxyapatite (HAp) with hollow structure was successfully synthesized by hydrothermal process of as-prepared calcium carbonate used as a hard template and calcium sources in a diammonium phosphate solution. Calcium carbonate was fabricated by precipitation, which possessed different morphologies such as balls, rods and blocks through regulating the amount of citric acid. The synthesized powders were characterized by X-ray diffraction (XRD), Fourier transform infrared spectrograph (FT-IR), field-emission scanning electron microscope (FESEM) and high-resolution transmission electron microscopy (HRTEM) and nitrogen adsorption–desorption. Results indicated that different morphologies calcium carbonate could convert to hollow structural HAp with the higher BET surface area and the mesopores. Hydrothermal temperature and hydrothermal time play a slight role on transition percentage. As hydrothermal temperature and hydrothermal time increased, the conversion rate of calcium carbonate to hydroxyapatite increased. The possible formation mechanism of hydroxyapatite was preliminarily investigated. The resultants of HAp are interesting materials for drug delivery and sustained-release.     

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.     

超细碳酸钡粒子的合成

采用共沉淀法合成了碳酸钡粒子。通过添加合适的晶形控制剂,合成了球状和哑铃状的碳酸钡粉体,利用扫描电子显微镜(SEM)和X射线衍射仪(XRD)进行了表征,并对不同晶形碳酸钡的形成机理进行了初步的探讨。     

Effect of initial pH on formation of hollow calcium carbonate particles by continuous CO2 gas bubbling into CaCl2 aqueous solution

Hollow calcium carbonate (CaCO₃) particles are synthesized by continuous bubbling CO₂ gas into CaCl₂ aqueous solution. In order to study the formation kinetics of the hollow CaCO₃ particles, the transmitted light strength of the CaCl₂ solution during the reaction was measured automatically with an on-line monitoring. It was verified that the pH for the formation of the hollow particles depended on the reaction temperature. Higher initial pH of the CaCl₂ solution resulted in the higher ratio of hollow particles as compared to that obtained at lower pH.     

Synthesis of cubic type hollow silica particles

Cubic-type hollow silica particles were prepared from Fe₂O₃-SiO₂ core-shell composite particles by selectively leaching the iron oxide core materials using acidic solution. The cubic Fe₂O₃ core particles were obtained by the hydrolysis reaction of iron salts. The Fe₂O₃-SiO₂ core-shell type particles were prepared by the deposition of a SiO₂ layer onto the surface of Fe₂O₃ particles using a two-step coating process. The first step involved primary coating with sodium silicate solution followed by subsequent coating by controlled hydrolysis of tetraethoxysilicate (TEOS). The core Fe₂O₃ was removed by dissolution in an acidic solution which gave rise to the hollow type silica particles. Scanning electron microscopic observation clearly revealed that the morphology is closely related to those of core the Fe₂O₃ particles. The cross sectional view determined by transmission electron microscopy revealed a silica shell with a thickness of about 50 nm. The porous texture of the hollow type silica particles is further characterized by nitrogen adsorption-desorption isotherm measurements.     

Synthesis of porous carbon hollow particles maintaining their structure using hyper-cross-linked Poly(St-DVB) hollow particles

Porous carbon hollow particles (PCHPs) have many useful features such as a high specific surface area, large pore volume, and the presence of nanovoids, giving them potential for use in catalyst carriers, supercapacitors, and Li-ion batteries. However, conventional synthesis methods have many problems. In this study, we developed a new method to produce hollow polymer particles that retain their structure after carbonization, without using any templates which need to be removed later. These poly(styrene-divinylbenzene) (Poly(St-DVB)) hollow particles are hyper-cross-linked by Friedel-Crafts alkylation, which prevents collapse during carbonization. The synthesized PCHPs have a large specific surface area, and abundant micropores and macropores derived from their hollow structure. The shell of the PCHPs was found to be composed of amorphous carbon partially crystallized as graphite.     

以碳酸钙为模板制备空心羟基磷灰石微球及其表征

以碳酸钙为模板和钙源,与磷酸氢二铵通过水热反应,制备出尺寸均匀、形态规则的空心羟基磷灰石微球。采用X射线衍射(XRD)、傅里叶变换红外光谱(FT-IR)、扫描电镜(SEM)、透射电镜(TEM)测试制备的样品,结果显示,制备的空心羟基磷灰石微球具有与碳酸钙微球模板相似的形貌,空心,尺寸均匀且形貌规则。并通过改变水热反应时间探索了羟基磷灰石微球的形成机理。此羟基磷灰石空心微球在生物医学领域具有较大的应用前景。     

碳酸钙微球的制备及其机理

为了制备出形貌更好的碳酸钙微球,以氯化钙和碳酸钠为原料,通过乙醇溶液和添加柠檬酸2种不同的方法制备。利用场发射扫描电镜、X射线衍射和傅里叶变换红外光谱等方法对制备的产物进行分析。结果表明,50%体积分数的乙醇溶液与1.0 mol·L-1柠檬酸调控下都能制备出形貌良好的碳酸钙微球,采用柠檬酸制备的碳酸钙微球成球性较好,制备的碳酸钙微球均由不同的晶型构成。实验通过改变反应条件进一步探索了在柠檬酸控制下碳酸钙微球的成球机理。     

Synthesis of hollow zirconia particles using wet bacterial templates

Hollow particles have attracted considerable attention owing to their unique properties. In this work, hollow zirconia particles were synthesized using rod-shaped gram-negative bacteria, Escherichia coli, as templates. A zirconia precursor, generated by the hydrolysis of zirconium butoxide, was deposited on the surface of the bacterial cells to form the shell of the hollow particles. The as-synthesized particles had the morphology of the bacterial templates, and were about 1.7 μm long and 0.8 μm across. The bacterial templates could be removed by calcination at 800 °C. The particles shrank on calcination to a final size of about 1.0 μm long and 0.4 μm across, with a wall thickness of about 69 nm. The specific surface area and average pore diameter were 45.7 m²/g and 1.9 nm, respectively. When fixed cells without internal water were used as templates, no hollow particles were observed; this implies that the internal water inside the cells acted as the initiator for the hydrolysis of zirconium butoxide.     

Controllable synthesis of silica hollow spheres by vesicle templating of silicone surfactants

Silica hollow spheres (SHSs) have been designed and prepared through three distinct synthetic routes based on the self-assembling of comb-like copolymer silicone surfactants. This process was based on the rule of similarities for hydrophobicity and hydrophilicity between the surfactant and a silica source. The directed silica wall formations were performed at different confined spaces of the vesicles, including the outer and inner surfaces, and the hydrophobic parts of the bi-layers. The resultant SHSs possess tailorable shell thicknesses (20–400 nm), particle sizes (200 nm–1.2 μm), and a high dispersibility in aqueous solutions.     

Tailoring surface properties of paper using nanosized precipitated calcium carbonate particles

Pigment particles used in paper coatings are typically of micrometer size and consequently the thickness of the coatings is, even at its lowest, in micrometer scale. Progress in nanotechnology has given way to the development of nanosized materials to be used in coatings, yet their exploitation has not been studied to a great extent. This study examines utilization of nanosized precipitated calcium carbonate (nanoPCC) particles in nanoscale thin coating layers. In contrast to commonly used coatings, a thin nanoparticle-based coating was targeted to change the substrate surface characteristics via controlled surface structure rather than via high coat weight. A novel approach for stabilizing and modifying the nanoPCC particles with pectin and alkenyl succinic anhydride (ASA) was utilized and a nanoparticle coating with uniform particle distribution was created. The coating applied on paper substrate was hydrophobic, having a water contact angle of 125°. Particle surface modification provided dispersion stability, enabling control of the coating layer structure. The introduced concept provides a new approach to paper coatings utilizing controlled deposition of nanoparticles with extremely low coat weight, yet having high impact on substrate surface properties. Additionally, as paper is an environmentally sound product, the approach to form a controllable nanostructure on a green substrate has potential in applications outside the traditional paper products.     

单分散PSMMA@ZrO2核壳胶体颗粒及ZrO2中空颗粒的制备与表征

采用乙腈与乙醇混合溶剂法制备出单分散的PSMMA@ZrO2核壳胶体颗粒,并通过TEM、SEM等表征手段对乙腈相对含量以及催化剂选择等参数的影响进行研究,结果表明室温下乙腈相对体积含量为20%时,采用去离子水为催化剂可制得高质量的单分散核壳胶体颗粒.通过高温煅烧得到ZrO2中空球,XRD结果表明二氧化锆转化为单斜相.漫反射光谱结果表明ZrO2核壳颗粒与中空颗粒在测量光谱区间内均具有较高的反射率.     

Evaluation and control of the adhesiveness of cohesive calcium carbonate particles at high temperatures

Understanding the adhesiveness of fine particulate materials at high temperatures is important to achieving the stable, economical operation of various industrial systems. In the present research, two types of calcium carbonate (CaCO₃) particles having different mean particle sizes (often used as heat carriers in energy systems) were evaluated. The tensile strengths of beds of these materials were determined at various temperatures by tensile strength measurement tester. The adhesiveness was found to increase greatly at 500 °C even without chemical reactions or sintering, and X-ray diffraction analyses showed thermal expansion of the CaCO₃ crystals at 500 °C. Pure alumina (Al₂O₃) and silica (SiO₂) microparticles did not exhibit the same pronounced increases in tensile strength or crystal expansion at this same temperature. Because the surface distances between these primary particles were presumably small, it is proposed that van der Waals forces between the particles greatly increased at high temperatures. The addition of Al₂O₃ nanoparticles to the CaCO₃ decreased the tensile strengths of the powder beds both at ambient temperature and at 500 °C. The experimental data confirm that the surface distances between primary particles were increased upon incorporating the nanoparticles, such that the tensile strength decreased during heat treatment.     

湿化学法合成纳米AlN粉末

采用醇盐水解工艺结合碳热氮化还原法进行纳米Al N粉末的制备。以异丙醇铝、果糖、无水乙醇为原料,制备出透明的凝胶,干燥后得到分子水平混合的前驱体,在1 450℃经碳热氮化还原法制备出单相Al N纳米粉末。系统研究了前躯体形成机制,以及碳热氮化还原的温度和时间、C/Al摩尔比、凝胶温度等因素对合成粉体的影响。采用XRD、TG-DSC和SEM对合成产物的特性进行了分析和表征。通过优化工艺,制得类球形的Al N粉末颗粒,其颗粒大小为30~90 nm。     

Ferroelectric hollow particles obtained by solid-state reaction

Hollow particles of barium titanate were obtained by a two-step process combining colloidal chemistry and solid-state reaction. BaCO(3) crystals (size ≈1?μm) suspended in a peroxy-Ti(IV) aqueous solution were coated with an amorphous TiO(2) shell using a precipitation process. Calcination of the BaCO(3)@TiO(2) core-shell particles at 700?°C resulted in the formation of BaTiO(3) hollow particles (shell thickness of ≈70?nm) which retain the morphology of the BaCO(3) crystals. Formation of the cavity occurs because out-diffusion of the core phase is much faster than in-diffusion of the shell material. X-ray diffraction (XRD) and Raman spectroscopy indicate that the hollow particles possess a tetragonal ferroelectric structure with axial ratio c/a = 1.005. Piezoresponse force microscopy has shown strong piezoactivity and 180° ferroelectric domains. The process described provides a general route to fabricate hollow ferroelectric structures of several compounds.