Chemical modification of flexible and rigid poly(vinyl chloride) by nucleophilic substitution with thiocyanate using a phase-transfer catalyst

The purpose of this study was to examine the effect of a phase-transfer catalyst on the chemical modification of flexible and rigid poly(vinyl chloride) (PVC) by substituting chloride with thiocyanate (SCN) in order to develop a new process for recycling PVC. The effects of temperature and time on the reaction of a SCN/ethylene glycol (EG) solution on PVC were investigated in the presence and absence of tetrabutylammonium bromide (TBAB) as a phase-transfer catalyst. TBAB was found to accelerate the dehydrochlorination of both flexible and rigid PVC, thus allowing the reaction to take place over shorter reaction times. The substitution yield and substitution/dehydrochlorination ratio were higher in the presence of TBAB than in its absence. By reducing the reaction temperature, the substitution/dehydrochlorination ratio increased, and substitution occurred more rapidly when TBAB was present. The differences between flexible and rigid PVC were negligible. Together, these results indicate that the phase-transfer catalyst TBAB is effective in accelerating the substitution of chloride by SCN. This two-phase reaction allows for the easy separation of the polymer from the solvent without using other chemicals or thermal processes.     

Behavior and products of mechano-chemical dechlorination of polyvinyl chloride and poly (vinylidene chloride)

The mechano-chemical (MC) dechlorination of polyvinyl chloride (PVC) and polyvinylidene chloride (PVDC) was performed by mechanical milling PVC/PVDC powder with zinc powder in a planetary ball mill, and the products of dechlorination were characterized by Infrared spectra (IR), X-ray diffraction (XRD), Raman spectroscopy, gas chromatography-mass spectrometry (GC-MS), and 13C solid-state nuclear magnetic resonance (NMR). The experimental results show that PVC/PVDC can be easily dechlorinated by milling with zinc powder, and formed various kinds of inorganic and organic products. Inorganic compounds included Zn2OCl(2).2H2O, Zn5(OH)8Cl2.H2O etc., and organic products involved diamond-like carbon, carbyne fragment, polyacetylene etc. Organic products formed following the paths of dechlorination, dehydrochlorination, crosslink, and oxidation. The mechano-chemical dechlorination process of PVC/PVDC may be an effective approach for carbyne synthesizing in the appropriate condition.     

Solvent-assisted self-assembly of amphiphilic polymer/surfactant complexes

We describe a simple manipulation of an amphiphilic polymer, polyvinylacetone (PVKA, with ketalization degree D_H = 0.549), mixed with tetrabutylammonium bromide (TBAB) that generates a series of self-assembled superstructures in the selective solvent composed of dimethylsulfoxide (DMSO) and acetone. The morphologies of those superstructures could be tuned by varying the ratio of DMSO/acetone in the solvent, as well as by varying the TBAB concentration in the original system. This procedure thus adds a facile yet effective tool for superstructure formation of polymer/surfactant complexes. These offer the probability of the research of PVKA on structural construction and utilization, and fabricating such assemblies' essential is not only to the production of novel devices but also to the understanding of fundamental phenomena at the nano-/microscale.     

Bi3+和四丁基溴化铵对碱性可充锌电极枝晶生长行为的影响*

采用电流－时间曲线、极化曲线和扫描电子显微镜等方法,研究了Bi^3 与四丁基溴化铵（TBAB）对可充锌电极在碱性锌酸盐溶液中枝晶生长行为的影响。实验结果表明,Bi^3 和TBAB对锌电极的枝晶生长均有一定的抑制作用,但在高阴极过电位下TBAB不能有效地抑制锌枝晶的生长。在实验过程中还发现,Bi^3 和TBAB对锌枝晶的抑制具有明显的协同作用,且对锌电极的放电行为几乎不产生影响。     

Study of phase-transfer-catalyst influence in CaO-SiO2 Gel preparation

Gels in a CaO-SiO₂ (2080 wt%) system were prepared in a heterogeneous phase. The following phase-transfer catalysts were tested: 18-Crown-6, 15-Crown-5 and tetrabutylammonium hydrogenosulphate. The influences of the polarity of two non-classical solvents (toluene and dichloromethane) were also studied. The degrees of polymerization and of oxide contents were analysed by infrared spectroscopy and thermal analysis. Finally, the morphology and structure of the dry and fired gels were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD).     

Supporting electrolytes containing tetrabutylammonium ions in Li/TiS cells intercalation of tetrabutylammonium ions in TiS

In context with the development of $\text{Li}\text{TiS}{}_2$ cells, the role of tetrabutylammonium bromide (TBAB) was investigated as Supporting Salt in LiSCN-1:3 dioxolane organic electrolytes. TBAB had little effect on the overall conductivity. A deterioration of cell performance was noted upon addition of TBAB to the electrolyte in spite of an improvement in the lithium half-cell. This behavior is attributed to the intercalation of TBA⁺ ions which have been shown in independent experiments to insert into TiS₂ to form the new compound TBA_x⁺ TiS₂.     

Repeatable synthesis of Cu2O nanorods by a simple and novel reduction route

Cu₂O nanorods were synthesized by reducing bamboo leaf-shaped Cu(OH)₂ with sodium hypophosphite (NaH₂PO₂) in an H₂O/ethylene glycol (EG) mixing solution. The Cu(OH)₂ was prepared by adding an alkaline solution to an aqueous solution containing CuSO₄ and NaH₂PO₂ at room temperature. The optimum temperature range for the reduction of the Cu(OH)₂ to Cu₂O nanorods was 55-70 °C. The products were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. The result showed the prepared Cu₂O nanorods were uniform and had diameters of 10-20 nm and lengths of 150-200 nm. The synthesis is simple, inexpensive, and highly repeatable.     

Fabrication and characterization of Ag/calcium silicate core-shell nanocomposites

The Ag/calcium silicate nanocomposite with core-shell nanostructure has been successfully synthesized using Ag solution, Ca(NO₃)₂·4H₂O and Na₂SiO₃·9H₂O in ethanol/water mixed solvents at room temperature for 48 h. Ag solution was previously prepared by microwave-assisted method in ethylene glycol (EG) at 150 °C for 10 min. The nanocomposites consisted of Ag core and an amorphous calcium silicate shell. The XRD and EDS results confirmed that the product was the Ag/calcium silicate nanocomposite. The TEM micrographs indicated that the Ag/calcium silicate nanocomposite was core-shell nanoparticles. The effects of Ca(NO₃)₂·4H₂O and Na₂SiO₃·9H₂O concentration on the shells of Ag/calcium silicate nanocomposite were investigated. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and energy-dispersive X-ray spectra (EDS). This method is simple, fast and may be extended to the synthesis of the other kinds of core-shell nanocomposites.     

Pressure drop and heat transfer characteristics of clathrate hydrate slurry in a plate heat exchanger

Pressure drop and heat transfer characteristics of 0-17.5 vol% tetrabutylammonium bromide (TBAB) clathrate hydrate slurry (CHS) as a secondary refrigerant flowing through a plate heat exchanger (PHE) were investigated in the present research. It was found that the pressure drop of TBAB CHS was about 3.0-50.0 kPa which was about 1.2-2 times of that of the chilled water at the flow rate of 2.5-13.0 L min⁻¹. The pressure drop increased with the increase of the volume fraction. Variation of the pressure drop with the modified Reynolds number was discussed and compared with that of the ice slurry. Flow friction factor correlation and local heat transfer correlation for TBAB CHS flowing through PHE were both proposed based on the experimental data. In addition, the influential factors, such as the inlet water temperature and inlet CHS volume fraction, on the overall heat transfer coefficient were discussed.     

Thermal and tensile properties of HTPB-based PU with PVC blends

Blends of HTPB (hydroxyl-terminated polybutadiene)-based polyurethane (PU) and polyvinyl chloride (PVC) membranes with various relative weight percentages were prepared by solution process. Different equivalent ratios of HTPB, 4,4′-dicyclohexyl methane diiscyanate (H₁₂MDI), and 1,4-butane diol were used to synthesize PU solution by two-stage process. The intermolecular bonding between N-H, CO groups of PU and C-Cl group of PVC was determined via FTIR analysis by the relative absorbance of the two N-H groups and was correlated to thermal/mechanical properties. Larger part of PVC has been found to disperse in the hard domain of PU resulting in the shift in IR frequency. Thermal property, tensile strength and intermolecular bonding of membranes were function of the contents of PVC and PU's hard segment. One-year aged butadiene-containing PUs and blends still exhibit higher tensile strength than that of as-prepared ones. Hence, it is promising to replace the plasticizer, such as DOP, in PVC by these HTPB-based PU for the prevention of PVC migration as well as the enhancement of mechanical and thermal properties of blends.     

Study on thermodynamics and oxidation mechanism of ethylene glycol in the preparation of nanometer nickel powders

Nanometer nickel powders have been prepared using the polyol method with NaOH, Ni(NO₃)₂·6H₂O, ethylene glycol (EG), and polyvinylpyrrolidone (PVP) as raw materials. The thermodynamics of the reaction system was studied, and the E–pH diagram of Ni–EG–H₂O was plotted. The oxidation products of EG were predicted from the E–pH diagram, and CO₃²⁻ in alkaline solutions was identified as the product through the IR spectrum and CaCO₃ sediment. Field-emission scanning electron micrograph (FE-SEM) showed that spherical nanometer nickel powders were obtained.     

Rapid fabrication and optical properties of zinc sulfide nanocrystallines in a heterogeneous system

ZnS nanoparticles about 3 nm in size were prepared by a simple, rapid and reliable route under microwave irradiation in a heterogeneous system, using ZnAc₂·2H₂O (AcCH₃COO) and Na₂S·9H₂O as the starting materials, ethylene glycol (EG) as the medium. The product was characterized with X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and ED, respectively. The optical properties of ZnS nanoparticles were studied.     

Rapid synthesis of Ag@Ni core-shell nanoparticles using a microwave-polyol method

Mixtures of AgNO₃ and NiSO₄·6H₂O, NiCl₂·6H₂O, or Ni(NO₃)₂·6H₂O were reduced in ethylene glycol (EG) in the presence of NaOH and poly(vinylpyrrolidone) (PVP) under microwave (MW) heating for 10 min. Then, we succeeded in the synthesis of Ag core-Ni shell nanoparticles, denoted as Ag@Ni, in high yield. The formation of Ag@Ni particles was confirmed using energy dispersed X-ray spectroscopic (EDS) measurements and selected area electron diffraction (SAED) patterns. The growth mechanism of Ag@Ni is discussed. The UV-Vis spectra of Ag@Ni were similar to those of Ni particles.     

Experimental study on LiCl solution falling-film generation process outside a vertical tube

For the purpose of the development of a generator with higher performance utilizing LiCl/H₂O as the working pair in a two-stage absorption refrigeration system, an experimental investigation of LiCl solution falling film generation outside a vertical tube as the high-pressure stage solution cycle was conducted. An experimental setup was established to study heat and mass transfer process in a falling-film generator for LiCl/H₂O using low-temperature heat source. The experiments showed effect of the flow rates of hot water and falling film solution, temperature of heat source, concentration of the solution and generation pressure on the LiCl/H₂O generation process. To compare with conventional LiBr/H₂O solution, some comparative experiments of falling film generation were tested in order to discuss the mass transfer performance of two different working pairs in a high-pressure generator. The results showed that the two working pairs had similar mass transfer rate. The LiCl/H₂O solution had a similar mass transfer rate to that of the LiBr/H₂O solution, while the concentration of LiCl/H₂O solution was much lower with smaller circulation ratio of the solution, and it could make for possible improvement in the thermal performance of the absorption refrigeration system.     

类石墨烯/氯化聚乙烯-聚氯乙烯复合材料的制备与性能

采用微波辐照法制备了膨胀石墨(EG),利用EG、氯化聚乙烯(CPE)和聚氯乙烯(PVC)的固相剪切碾磨(S³M)制备了EG-CPE-PVC复合粉体,复合粉体进一步与PVC、热稳定剂和增塑剂混匀,经塑化和模压成型得到类石墨烯/CPE-PVC复合材料。用粒度分析、XRD、AFM、SEM和TEM等手段表征了复合粉体及其复合材料的结构与性能。结果表明: S³M实现了体系的粉碎、分散,EG片层的剥离及与CPE-PVC的纳米复合。CPE的加入实现了EG的进一步剥层,使EG片层的厚度达到1~3层,达到了EG的石墨烯化目标。当EG质量分数为3%时,类石墨烯/CPE-PVC复合材料的电导率呈指数上升,与PVC相比提高了8个数量级;当EG质量分数超过4%时,电导率再次激增,出现逾渗现象;在EG质量分数为5%时,电导率达到0.01 S/m,复合材料表现出良好的抗静电性能。     

CO oxidation on planar Au/TiO2 model catalysts: Deactivation and the influence of water

The CO oxidation behaviour of planar Au/TiO₂ model catalysts was studied by a combination of kinetic measurements and in-situ IR measurements under realistic pressure and temperature conditions (p = 20 mbar, T = 80 °C). During reaction in a CO/O₂ mixture, the model catalysts deactivated significantly. Adding small amounts of H₂O (1000 ppm) to the reactive CO/O₂ gas mixture, the catalyst activity increased markedly, by at least one order of magnitude. Furthermore, in-situ IR measurements show a decrease of the amount of adsorbed by-products of the CO oxidation, and a change of the predominant by-product from surface carbonate to surface formate. Possible reasons for the deactivation are discussed and the effect of H₂O addition is compared to results of similar studies on more realistic dispersed catalysts.     

Studies on the effect of organic additives on the monolithicity and optical properties of the rhodamine 6G doped silica xerogels

Rhodamine 6G (R6G) laser dye doped silica xerogels were prepared by sol–gel processing using tetraethylorthosilicate [TEOS, Si(OC₂H₅)₄] precursor, citric acid (CTA) catalyst and ethanolic R6G in the presence of various organic additives such as formamide (FA), N′methylformamide (N′MF), dimethylformamide (DMF), acetamide (AA), glycerol (GLY), oxalicacid (OXA), ethyleneglycol (EG) and diethyleneglycol (DEG). The organic additive/TEOS molar ratio was varied from 0.001 to 0.1 by keeping the TEOS/EtOH/H₂O/CTA/R6G molar ratio constant at 1:5:7:1.2×10⁻³:9.2×10⁻⁶. It was found from the spectral studies of the additive modified R6G doped silica xerogels that the absorption maxima at 530 nm and emission maxima at 565 nm were increased with the addition of organic additive and with the increase of the additive/TEOS molar ratio. The transparency of the R6G doped silica xerogels was increased with the increase of additive/TEOS molar ratio from 0.001 to 0.1 with OXA, DEG and EG and in the case of DMF, N′MF, FA, AA and GLY, the transparency of the samples increased up to 0.014 of additive/TEOS molar ratio and then decreased for >0.014 of additive/TEOS molar ratio. Monolithic samples were obtained with all the organic additives. The percentage volume shrinkage of the samples was less EG and DEG and more with OXA additives.     

Hydrogen evolution kinetics during transition metal oxide-catalyzed ammonia borane hydrolysis

This paper examines the feasibility of using transition metal oxides (cobalt, iron, copper, molybdenum, and vanadium oxides) as catalysts for ammonia borane (AB) hydrolysis. In our experiments, we used an aqueous solution containing 0.24 wt % AB. The amount of oxide catalysts was 10–40 mg. The hydrolysis process was run in the temperature range from 35 to 80°C. The highest hydrogen evolution rate was observed at a temperature of 80°C in the presence of cobalt and iron oxides (Co₃O₄ and Fe₂O₃ · nH₂O). The data obtained for the cobalt and iron oxides demonstrate that the reaction is first-order in ammonia borane. We determined the rate constants of the process and its apparent activation energy: 47.5 kJ/mol for Co₃O₄ and 60.2 kJ/mol for Fe₂O₃ · nH₂O. The cobalt and iron oxides were shown to be efficient catalysts for hydrogen production from aqueous AB solutions.     

Triethanolamine copper chloride prepared from zerovalent metal: another polymorph of a known Cu(II) compound or a mixed-valence complex with all-trigonal bipyramidal copper?

Two new copper complexes with triethanolamine (H₃L) have been prepared using copper powder and characterized by X-ray crystallography, IR and EPR spectroscopy. These are [Cu^I(H₃L)Cl]_x⋅[Cu^II(H₂L)Cl]_1−x (X=0; 2/3) (1) and [Cu^II(H₂L)SCN] (2). Both complexes are neutral species and contain copper atoms in trigonal bipyramidal environments. The important dimensions in 1 are Cu-N 2.011(5), 3Cu-O 2.073(3), Cu-Cl 2.239(2) Å and N-Cu-Cl=180.0°; in 2 Cu-N_NCS 1.918(3), Cu-N_H2Tea 1.983(3), Cu-O 2.004(2), 2Cu-O 2.13(1) Å and N_H2Tea-Cu-N_NCS=174.6(1)°. 2 has all the copper atoms in the oxidation state II, while the three-fold symmetry in 1 would suggest that the metal atoms are formally in the oxidation state I. Results of magnetic measurements of several samples of 1 are rationalized by assuming that a continuous range of composition for [Cu^I(H₃L)Cl]_x⋅[Cu^II(H₂L)Cl]_1−x can occur. In the case of x=0, 1 becomes a polymorph of the reported compound [Cu^II(H₂L)Cl].     

Fabrication and characterization of FePt magnetic nanofibers via electrospinning technique

L1₀-structured platinum–iron (FePt) nanofibers were successfully synthesized by electrospinning technique, followed by calcination and reduction processes. In the preparation procedure, ferrous chloride tetrahydrate [Fe(Cl)₂?4H₂O] and iron nitrate nonahydrate [Fe(NO₃)₃?9H₂O] were, respectively, used as iron sources contained in precursor solution for electrospinning. Subsequently, the FePt nanofibers were obtained from the calcination in air and the followed reduction in hydrogen (H₂) of the as-spun FePt/PVP composite nanofibers. The FePt nanofibers were characterized by X-ray diffractometer, scanning electron microscopy, transmission electron microscopy, and superconducting quantum interference device magnetometry. It was found that the different iron salt used in the spinning solutions could highly affect the FePt nanofiber morphology, crystallite size, and the magnetic properties. The FePt nanofibers, resulted from the spinning solution containing iron dichloride tetrahydrate, were of better crystallinity and well-defined fibrous morphology with an average diameter of about 110 nm. Additionally, the considerably large coercivity of 10.27 kOe was recorded from the above FePt nanofibers.