Formation of Monodisperse Spherical TiO2 Powders by Thermal Hydrolysis of Ti(SO4)2

Titania powders have been prepared by the thermal hydrolysis of titanium sulfate at 80°C in a mixed solvent of n -propyl alcohol ( n -PrOH) and water. The morphology of the powders was greatly influenced by the volume ratio in n -PrOH to water (RH ratio) of the solvent. An RH ratio of 1.0 was essential for the formation of spherical TiO₂ powders. When hydroxypropyl cellulose (HPC) was used as a steric dispersant, monodisperse spherical powders 0.7 (μm in diameter were produced. As the RH ratio was increased, the zeta potential of the powders was negatively increased and the dielectric constant of the solvent was decreased. However, powders obtained at an RH ratio of 1.0 were observed to have the highest energy barrier. The colloidal stability of the powders in a mixed solvent of n -PrOH and water is discussed. As-precipitated powders were amorphous hydrates of titania and were crystallized by calcination into anatase (>600°C) and rutile (>800°C).     

Hydrothermal synthesis of monodispersed LiFePO4 cathode materials in alcohol–water mixed solutions

Monodispersed LiFePO₄ powders were prepared by thermal decomposition of Fe(II)–citric acid complex precursor and application of isopropanol as a dielectric constant tuner. The powders morphology was greatly influenced by the volume ratio of isopropanol to water (RH ratio). Monodispersed short rod-like LiFePO₄ crystals were obtained when RH ratio was 1.0, while column-like LiFePO₄ particles composed of much smaller crystals were produced when isopropanol was absent.     

Synthesis of barium fluoride nanoparticles by precipitation in ethanol-aqueous mixed solvents

In this work, the BaF₂ nanopowders with different particle size were synthesized by precipitation in the ethanol/water mixed solvents. Five kinds of compositions of mixed solvents, including pure water, 25 vol.%, 50 vol.%, 67.5 vol.%, and 75 vol.% of ethanol were used. The effects of aging and the volume percentage of ethanol in the mixed solvents on the resultant BaF₂ nanoparticles were under investigation. The size and morphology of the BaF₂ particles were characterized by TEM, FSEM and XRD analyses. The results show that after aging for 2 h the particle size of the BaF₂ precipitates in the 50% mixed suspension changes little. The prepared BaF₂ particles all exhibit cubic fluorite structures no matter what kind of composition is used. In pure water environment, the size of BaF₂ particles is about 70 nm, whereas it reduces to 33 nm in the 75% mixed solution. As the vol.% of ethanol increases the particle size decreases, and other properties such as the size distribution, dispersion, oriented growth et al. are also modulated. These alterations can be interpreted by varying the dielectric constant of mixed solvent.     

Direct observation of water uptake and release in individual submicrometer sized ammonium sulfate and ammonium sulfate/adipic acid particles using X-ray microspectroscopy

Scanning transmission X-ray microscopy (STXM), a microscopy method which allows imaging with a spatial resolution of 40 nm, and X-ray absorption spectroscopy were used to follow in situ the water uptake and release in submicrometer sized particles on a substrate enclosed in a microreactor. Oxygen K-edge near edge X-ray absorption fine structure (NEXAFS) spectra from supported ammonium sulfate particles in their dry salt, saturated solution and supersaturated solution states were obtained for the first time. The variations at the oxygen edge were related to the water content as a function of relative humidity (RH), consistent with mass growth measurements done on larger samples or suspended particle ensembles. Investigations on morphological changes upon water uptake were performed in mixed ammonium sulfate-adipic acid particles using STXM images and NEXAFS spectra taken at the oxygen and the carbon absorption edges, confirming the two phase structure suspected from previous hygroscopicity studies, where adipic acid forms a separate phase of complex morphology partially enclosed by the ammonium sulfate solution at high RH. This example emphasizes the combination of chemical resolution provided via NEXAFS, spatial resolution via STXM and the in situ capability provided by the novel microreactor to obtain information about the microstructure of mixed organic/inorganic particles under close to ambient conditions.     

正丙醇-水-复合溶剂体系等压汽液平衡研究

采用新型双循环沸点仪,测定了100 kPa下正丙醇-水-复合溶剂体系的等压汽液平衡数据。实验结果表明:乙二醇与醋酸钾组成的复合溶剂可消除正丙醇-水的共沸点,并显著提高正丙醇-水的相对挥发度;随着复合溶剂质量分数的增加,正丙醇对水的相对挥发度增大;此复合溶剂可作为萃取精馏正丙醇-水体系的溶剂,适宜的质量分数约为60%。用有序双液(NRTL)方程对实验数据进行了关联,关联结果良好,温度标准偏差为0.45 K,气相组成标准偏差为0.008 7。     

溶剂对对苯二酚晶体晶习的影响

采用冷却结晶方法,考察了水、甲醇、乙醇、正丙醇、异丙醇和正丁醇等溶剂对对苯二酚晶习的影响,并通过扫描电镜、差热扫描分析、X射线衍射等手段对对苯二酚晶体进行了分析表征.结果表明,溶剂性质显著影响对苯二酚晶体的晶习,随着溶剂介电常数的减小,晶体的长径比变小.在利用分子模拟软件Cerius²预测对苯二酚晶体晶习的基础上,初步揭示了溶剂影响对苯二酚晶体晶习的机理.     

Preparation of Monodisperse and Spherical Zirconia Powders by Heating of Alcohol–Aqueous Salt Solutions

A novel method is demonstrated which yields a spherical ZrO₂ powder of narrow size distribution through heating of a zirconyl chloride solution with an alcohol–water mixture as the solvent. The kind and composition of the solvent mixture greatly influenced the behavior of the precipitation and the morphology of the resulting particles. When 1-propanol or 2-propanol was employed as the alcohol of the solvent mixture, the resulting particles had a spherical shape and a narrow size distribution. The particle size and the particle agglomeration level could be controlled by the amount of hydroxypropyl cellulose (HPC) in the solution. As-prepared amorphous powder was crystallized to a mixture of metastable tetragonal phase and monoclinic phase at about 460°C. The metastable tetragonal phase was converted to the monoclinic phase as the calcination temperature was increased. After calcination, the spherical shape of the zirconia powder was retained, while its particle size was decreased slightly.     

聚(N-乙烯基异丁酰胺)接枝聚苯乙烯微球的合成研究

合成了数均相对分子质量为 35 0 0和 6 30 0的两种聚 (N 乙烯基异丁酰胺 ) (PNVIBA)大分子单体 ,并以此大分子单体与苯乙烯 (St)在V(乙醇 )∶V(水 ) =7∶3的混合溶剂中进行自由基分散共聚 ,得到了稳定分散的PNVIBA接枝聚苯乙烯 (PSt)高分子微球。研究发现微粒的粒径随聚合体系中大分子单体相对分子质量和质量浓度的增加而减小 ,并发现当混合溶剂中水的体积分数增加到 ρ(水 ) =35 %时 ,微球的形态发生明显变化。     

不挥发溶质对混合溶剂沸点及蒸气压的影响

测定了若干不挥发溶质对醇 (甲醇、乙醇、正丙醇 ) -水双液系恒压 (100.3kPa)汽液平衡的影响 ,其中包括 16种不挥发溶质对正丙醇 -水恒沸混合物沸点的影响 .通过理论分析 ,得到少量不挥发溶质对具有固定组成的二元混合溶剂沸点及蒸气压影响的普遍性结论 :不挥发溶质使难挥发组分的气相组成增加是引起溶液蒸气压降低或沸点升高的充分条件 ;在恒沸混合物中无论不挥发溶质使气相组成发生何种变化都会引起溶液蒸气压降低或沸点升高 .经检验 ,该结论与实验结果及大量文献数据完全相符 .     

Water Content and Phase Transitions in Particles of Inorganic and Organic Species and their Mixtures Using Micro-Raman Spectroscopy

Hygroscopicity and phase transitions were measured with deposited particles of ammonium sulfate (AS), ammonium nitrate (AN), malonic acid (MA), glutaric acid (GA), glyoxylic acid (GlyA), as well as two mixed particle systems AS-MA and AS-GA using micro-Raman spectroscopy. Hygroscopicity was presented in terms of water-to-solute mass ratios, which were obtained from the integrated area ratios of the Raman water band to a distinct solute peak. Deliquescence and crystallization were confirmed by abrupt changes in the Raman peak positions and the full-width-half-heights of distinct solute peaks. The results for AS, AN, MA, and GA agreed well with literature reports and model predictions. For GlyA, we detected the Raman water band at near 0% RH, indicating that the spectral technique is sensitive for hygroscopic measurements at very low RH. Additional spectral feature at ～ 0% RH was also observed. In the case of more complicated AS-dicarboxylic acid mixed systems, the partial phase transitions of the organic components were identified using the intensity ratios of aqueous to solid C = O peaks. AS-MA particles did not completely crystallize and gradual water uptake with increasing RH from 3% was observed. Moreover, it was found that AS-GA particles showed step-wise crystallization in which the AS fraction crystallized prior to the GA fraction. The measured water content and complete DRH of both mixed systems were consistent with the published values. The results show the utility of micro-Raman spectroscopic analysis in studying hygroscopicity and phase characterizations of the chemical species in mixed particles.     

Preparation and characterization of platinum-ruthenium bimetallic nanoparticles using reverse microemulsions for fuel cell catalyst

Platinum-ruthenium bimetallic nanoparticles are prepared by chemical reduction using sodium borohydride in reverse microemulsions of water/isooctane/Igepal CA-630/2-propanol for fuel cell catalysts. The prepared nanoparticles are characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and energy-dispersive X-ray analysis. The average size and morphology of nanoparticles are dependent on the water volume fraction in reverse microemulsion system in the range of ca. 2-4 nm. The morphology of particles is related with the percolation behavior of water droplets in reverse microemulsions. By the pretreatment of water phase using a hydrochloric acid, the particles of a homogeneous solid solution state can be obtained. The CO stripping cyclovoltammetry and the electrochemical measurements compared with commercial catalyst show that the prepared particles have a high electrochemically active surface area and a stable and high catalytic activity for reformate gas oxidation.     

TMS/H_2O配比对丙烯腈/衣康酸共聚物制备及性能的影响

以环丁砜(TMS)和水(H_2O)为反应介质,制备丙烯腈/衣康酸共聚物。利用FTIR、SEM、WAXRD和DSC等方法研究不同溶剂配比对共聚物结构性能的影响。研究结果表明:随溶剂中TMS含量减少,共聚物的相对分子质量线性增加,转化率呈先增大后减小的趋势,在TMS/H_2O质量比30/70时,转化率存在最大值,达96%;随溶剂中TMS含量的增加,聚合物颗粒形貌由坚硬的细粒团簇状转变为蓬松多孔的大颗粒;溶剂配比对主要官能团的峰位置无显著影响,但随溶剂中TMS含量的增加,环化起始温度和放热速率明显降低,环化放热反应缓和。     

基于水热/溶剂热法制备不同形貌LiNi0.8Co0.1Mn0.1O2 锂离子电池正极材料

基于水热/溶剂热法制备LiNi_0.8Co_0.1Mn_0.1O₂电极材料,以镍、钴、锰乙酸盐为原料,以六亚甲基四胺为沉淀剂、水或乙醇为溶剂,通过调节溶剂组分控制Ni_0.8Co_0.1Mn_0.1（OH）₂（NCM）的成核与生长速率,从而合成两种形貌不同的Ni_0.8Co_0.1Mn_0.1（OH）₂前驱体,再经过混锂煅烧获得LiNi_0.8Co_0.1Mn_0.1O₂正极材料,研究比较了其电化学性能。以水为溶剂通过水热法合成的前驱体样品呈现出由一次片状颗粒紧密堆积组成的长方体状二次颗粒形貌,经混锂煅烧得到的产物表现出较高的放电比容量,在0.5C倍率下首次放电比容量可达到189.70 mA·h/g,循环200次容量保持率为69.72%。以乙醇为溶剂通过溶剂热法合成得到球形二次颗粒前驱体,最终得到的产物具有多孔球形结构,表现出了优异的循环性能,0.5C首次放电比容量为178.65 mA·h/g,循环200次容量保持率仍高达94.55%。     

微球状ZIFs材料（TIF-5Zn）的制备及稳定性

以5,6-二甲基苯并咪唑和咪唑为配体,Zn(NO3)2为金属盐,采用水作为溶剂合成了一种具有GIS拓扑结构的沸石咪唑酯骨架（ZIFs）材料TIF-5Zn。研究了反应溶剂（水、甲醇、甲醇-氨水）对材料形貌的影响以及材料的化学稳定性和热稳定性,并用XRD、SEM、TG及CHN元素分析等手段对材料进行了表征。结果表明：溶剂对其形貌有显著的影响,在单一溶剂水或甲醇中只能形成不规整的微/纳米颗粒聚集体,而在甲醇-氨水混合溶剂中得到了形貌规整的微球状TIF-5Zn,它是由亚微米粒子组装而成的多级微米球结构。     

Effect of mixed solvent on structural,morphological, and optoelectrical properties of spin-coated TiO2 thin films

Nanocrystalline TiO₂ anatase thin films have been synthesized from alkoxide solution via sol–gel spin coating method. The effects of different solvents of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and tert-butanol as well as those of mixed solvents on crystal structure, thermal behavior, morphology, and optoelectrical properties were investigated. It was found that not only the occurrence of rutile with anatase phase was solvent dependent, but also the morphology and optoelectrical properties of the films were strongly affected by solvent type. However, using two different types of alcohols as a single solvent brings the advantages of both solvents. Also, some unique properties in mixed solvent samples could be achieved. The viscosity, gel time, boiling point, possible complexes, dipole moment, and chain length of the solvent affect the packing density, lattice distortion, interfaces, thickness, optical band gap, refractive index, and extinction coefficient.     

Nanoencapsulation of Alpha-linolenic Acid with Modified Emulsion Diffusion Method

Nanocapsules of alpha-linolenic acid (α-LA) were prepared by a modified emulsion diffusion technique with encapsulation efficiency of 93%. Polylactic acid (PLA) was used as the encapsulating polymer with acetone and ethyl acetate as organic solvents, and Tween 20, gelatin and Pluronic-F68 in water as stabilizers. Two ratios of organic to aqueous phases were used with each solvent and stabilizer. Nanocapsule dispersions with a particle size less than 100 nm and a zeta potential as high as 33 mV were obtained as verified by scanning electron microscopy and the dynamic light scattering technique respectively. Both particle size and zeta potential were influenced by such preparation conditions as the type of stabilizer, type of organic solvent and the organic to aqueous phase ratio. Acetone was superior to ethyl acetate, and Tween 20 was superior to each of Pluronic-F68 and gelatin in obtaining smaller, less aggregated nanocapsules. An organic to aqueous phase ratio of 1:5 was shown to be more suitable for the formation of smaller nanocapsules, particularly when acetone was used as the organic solvent.     

Effects of solvent on structures and properties of electrospun poly(ethylene oxide) nanofibers

Poly(ethylene oxide) (PEO) nanofibers were prepared by electrospinning PEO solution with a mixed solvent of ethanol and deionized water. The results show that the mixed solvent system has noteworthy influences on structures and properties of electrospun PEO nanofibers, including molecular chain orientation, crystallinity degree, surface morphology, fiber diameter, diameter distribution, spinnability, and productivity. With increasing ethanol content in the mixed solvent, wrinkly morphologies appear on the surface of PEO nanofibers due to a high evaporation rate of ethanol during electrospinning process. The dielectric constant, dipole moment, conductivity, density, boiling point, and solubility parameter of the mixed solvent become lower with the ethanol content increasing. Besides, the hydrogen‐bonding interactions between PEO and solvents become weaker. As a result, PEO nanofibers with larger diameters, lower molecular chain orientation, and crystallinity degree are obtained. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45787.     

Effects of solvents on properties of nanocrystalline hydroxyapatite produced from hydrothermal process

Hydroxyapatite (HA) particles have been synthesised in isopropanol–water solvent via hydrothermal process. The influences of isopropanol on crystallisation, such as phase evolution, crystallite size, crystallinity degree, chemical composition, and agglomeration of the HA nanoparticles have been investigated by using XRD, FTIR, TEM, BET, TG-DSC and laser diffraction method. All HA nanoparticles prepared in the water–isopropanol mixed solvent have been found to be carbonated HA, and the amount of carbonate increased with increase of alcohol in the solvent. However, the crystallite size and crystallinity degree of the HA nanoparticles decreased with the addition of isopropanol. In addition, there was little change in morphology of HA particles produced in different solvents, though the aspect ratio of the HA increased slightly with increasing concentration of alcohol. The agglomeration was found to be mainly controlled by the zeta-potential and not by the change of solvent.     

甘油合成1,3-丙二醇

以甘油为原料,经过氯代、氧化、克莱门森还原、水解4步反应,最终合成1,3-丙二醇,并用红外光谱仪和质谱仪对目标产物进行结构确定。从反应物摩尔比、反应温度、反应溶剂等优化了反应条件。最优反应条件为:氯代反应:温度120℃;氧化反应:温度23～27℃,n(1,3-二氯-2-丙醇)∶n(重铬酸钠)=1.8∶1,反应溶剂用量:1 mL水溶解1.4 g 1,3-二氯-2-丙醇;克莱门森还原反应:n(1,3-二氯丙酮)∶n(锌)=1∶1.2,水作反应溶剂最佳,在该条件下,1,3-丙二醇总产率可达37.1%。     

Influence of self-complementary hydrogen bonding on solution rheology/electrospinning relationships

A series of poly(alkyl methacrylate)s that contained either pendant carboxylic acid or self-complementary multiple hydrogen bonding (SCMHB) groups were synthesized to determine the influence of intermolecular associations on solution rheology and electrospinning performance. The cosolvent composition was varied in order to control the dielectric constant of the electrospinning solvent. By controlling the dielectric constant of the solvent, intermolecular interactions were systematically screened, and the influence of hydrogen bonding on electrospun fiber morphology was determined. While the diameter of the electrospun poly(methyl methacrylate) (PMMA) fibers were in excellent agreement with previously developed predictions, the diameter of the electrospun poly(methyl methacrylate-co-methacrylic acid) (PMMA-co-PMAA) fibers were smaller than predicted when electrospun from dimethyl formamide (DMF). The smaller PMMA-co-PMAA fibers were attributed to dissociation of the carboxylic acid group, which resulted in increased solution conductivity. The poly(methyl methacrylate-co-SCMHB methacrylate) (PMMA-co-SCMHB) displayed significant hydrogen bonding associations with decreasing solvent dielectric constant (D) which resulted in increased viscosity and lower entanglement concentration (C_e). Moreover, strong hydrogen bonding between the SCMHB groups in relatively nonpolar solvents increased the apparent molecular weight of the copolymers, and significantly larger electrospun fibers than predicted were obtained.