Decomposition process of bastnaesite concentrate in NaOH-CaO-H_2O system

A novel process of calcification-leaching for bastnaesite concentrate(REFCO_3) was proposed. The prior calcification was carried out in the system of NaOH-CaO-H_2O and the lgC-pH pattern for Ce-F-Ca-C-H_2O system was drawn. The thermodynamics result indicates that decomposition for bastnaesite requires certain alkaline condition, but excessive alkalinity also causes decomposition of CaF_2. XRD and SEM-EDS analyses on the calcification-leaching process reveal that bastnaesite first decomposes into RE(OH)_3 and CaF_2. Then, by HCl leaching rare earths were extracted,while CaF_2 was left in the leaching residue. In addition, effects of temperature, time, NaOH and CaO on the calcification were investigated. The results show that the leaching rate of rare earths(REs)reaches 72.5 wt%, at the same time 99.2 wt% of F is left in leaching residue with 20 wt% NaOH and 38 wt% CaO at 493 K for 180 min.     

Synthesis and Characterization of Some Nonionic Bolaamphiphiles

A series of nonionic bolaamphiphiles were synthesized from the reaction of fluoroalkylene (dimercaptoacetates) with maleate crown ethers. Surface activity of the new surfactants was evaluated on the basis of surface tension measurements. The new fluorinated bolamphiphiles exhibit a remarkable lowering of surface tension in comparison with nonfluorinated analogues.     

AlF_n~（3－n）在饮用水中各形体的分布

根据有关公式算出不同的ｐＨ值、不同游离Ｆ~－浓度时ＡｌＦ各形体的分布系数（α_ｎ），并导出计算平均配位数公式，进而算出有关饮用水除氟方法的最佳ｐＨ值范围。     

渗透结晶型液体硬化剂表面处理方法及作用机理研究

阐述了渗透结晶型表面处理剂的作用机理。渗透结晶型表面处理剂渗透进入水泥基内部后,与水泥的水化产物发生反应可以生成新的晶体来填补水泥缝隙,使基体更加密实,研究发现,这是通过与水泥基的化学反应增强机制来实现强化的。本文主要介绍了氟硅酸盐与水泥基材料的作用机理,并初步研究了氟硅酸盐表面硬化的处理方法。     

Theoretical Estimation of Acid Strength of Fluorine Hydrogen-Boron Fluoride Complexes

Abstract

The calculation of complexes R _n BF_3-n . HF (there is R = CH₃ and C₂H₅) has been carried out by the quantum-chemical semi-empirical MNDO method in Dewar and Teel parameterization. The geometrical and electronic structure of these complexes was obtained. On an example of simple H-acids we estimated their acid strength. We found that irrespective of the ligand surrounding of B atom the complexes R _n BF_3-n HF have rather high acid strength (pK _a = 17.9 14.9).     

氟离子选择电极法测定电解金属锰槽液中的氟含量

采用氟离子选择电极建立了一种对电解金属锰槽液中氟含量进行测定的方法。该方法通过加入柠檬酸三钠一硝酸钾作为总离子强度调节剂,采用已知添加量法,由添加前后的电极电位的变化值,计算出待测试样的浓度值,从而可快速准确地测定电解槽液中氟的含量。利用氟离子选择电极法测定出大新分公司的电解金属锰槽液中氟含量为0．20～50．00mg／L,加标回收率可达到100％。     

Determining the degree of grafting for poly（vinylidene fluoride） graft-copolymers using fluorine elemental analysis

Acrylic acid (AAc) and styrene (St) were grafted onto poly(vinylidene fluoride) (PVDF) powder or membrane samples by pre-irradiation graft copolymerization.The grafted chains were proved by FT-IR spectroscopy analysis.The degree of grafting (DG) of the grafted PVDF was determined by fluorine elemental analysis (FEA) method,and was compared with the DGs determined by weighing method,acid-base back titration method and quantitative FT-IR method.The results show that the FEA method is accurate,convenient and universal,especially for the grafted polymer powders.     

Effect of interfacial fluorination on the electrical properties of the inter-poly high-k dielectrics

In this paper, the reliabilities and insulating characteristics of the fluorinated aluminum oxide (Al₂O₃) and hafnium oxide (HfO₂) inter-poly dielectric (IPD) are studied. Interface fluorine passivation has been demonstrated in terminating dangling bonds and oxygen vacancies, reducing interfacial re-oxidation and smoothing interface roughness, and diminishing trap densities. Compared with the IPDs without fluorine incorporation, the results clearly indicate that fluorine incorporation process is effective to improve the insulating characteristics of both the Al₂O₃ and HfO₂ IPDs. Moreover, fluorine incorporation will also improve the dielectric quality of the interfacial layer. Although HfO₂ possesses higher dielectric constant to increase the gate coupling ratio, the results also demonstrate that fluorination of the Al₂O₃ dielectric is more effective to promote the IPD characteristics than fluorination of the HfO₂ dielectric. For future stack-gate flash memory application, the fluorinated Al₂O₃ IPD undoubtedly possesses higher potential to replace current ONO IPD than the fluorinated HfO₂ IPD due to superior insulating properties.     

Effect of α-substituents on molecular motion and wetting behaviors of poly(fluoroalkyl acrylate) thin films with short fluoroalkyl side chains

The effect of α-substituent on the molecular motion and wetting behavior of poly{2-(perfluorobutyl)ethyl acrylate} [PFA-C₄], poly{2-(perfluorobutyl)ethyl methacrylate} [PFMA-C₄], poly{2-(perfluorobutyl)ethyl α-fluoroacrylate} [PFFA-C₄], and poly{2-(perfluorobutyl)ethyl α-chloroacrylate} [PFClA-C₄] films were characterized by dynamic contact angle measurement, lateral force microscopy (LFM), wide angle X-ray diffraction (WAXD), and X-ray photoelectron spectroscopy (XPS). WAXD of oriented PFClA-C₄ fiber suggested the presence of rod-like chain due to the presence of bulky α-substituent. The glass transition temperature (T_g) of PFFA-C₄ and PFClA-C₄ were well above the room temperature. The water repellencies of PFFA-C₄ and PFClA-C₄ were as high as that of PFMA-C₄ and their oil repellency of PFFA-C₄ and PFClA-C₄ was higher than the PFMA-C_4. This result was originated from the low main chain mobility of PFFA-C₄ and PFClA-C₄ due to the presence of bulky α-substituents. The effect of molecular motion on water repellency was clarified by the results of temperature dependence studies of dynamic contact angle, LFM, and surface chemical composition measured by XPS.     

The effect of fluorine content on the mechanical properties of poly (?-caprolactone)/nano-fluoridated hydroxyapatite scaffold for bone-tissue engineering

In this study, the effect of fluorine content on the mechanical properties of the novel poly (?-caprolactone)/nano-fluoridated hydroxyapatite nanocomposite scaffolds was investigated. Poly (?-caprolactone)/nano-fluoridated hydroxyapatite (PCL-FHA) scaffolds were produced by solvent casting/particulate leaching method. The fluoridated hydroxyapatite nanopowders had a chemical composition of Ca₁₀(PO₄)₆OH_2−xF_x (where x values were selected equal to 0.5, 1, 1.5 and 2.0). Various weight percentages (10, 20, 30 and 40) of the FHA were added to the PCL. Sodium chloride (NaCl) particles having diameter of 300-500 μm were used as porogen. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were used to identify the phase structure and functional groups of obtained scaffolds. Mechanical properties of the prepared scaffolds were also determined. Results showed that the compressive strength of scaffolds increases with decreasing the weight percent of fluorine in FHA.