Study of interaction of ethylene glycol/PVP phase on noble metal powders prepared by polyol process

Noble metal powders (Au, Ag, Pt, Pd and Ru) have been synthesized by the polyol process in both the nanometer and submicron scales (sans Pd, Pt and Ru). They have been characterized by both microscopic (TEM and SEM) as well as spectroscopic techniques (FT-IR and XPS). Infrared spectroscopy was employed to study the colloid particles in the presence of ethylene glycol and PVP and the results show that the interaction between the organic phase and the metal particles vary according to the particle size. The role of the solvent, ethylene glycol, during the reduction process was also investigated and we observe formation of >C=O vibration band after the reduction process implying that the solvent reduces the metal ions thereby getting oxidized. XPS measurements carried out on the colloidal sols have shown the presence of the organic phase adsorbed onto the metal particles.     

Electrochemical preparation of metal cluster compounds

The electrochemical formation of low-valent cluster compounds is described. K₄Nb₆Cl₁₈ crystallizes on the cathode at 610°C, when an eutectic KiCl/KCl melt containing Nb₃Cl₈ is electrolysed with a niobium anode at 0.6 to 1.2 V cell voltage. Electrolysis of GdCl₃ at 770° yields h-GdCl both at the tantalum cathode and the gadolinium anode. Crystals of Gd₂Cl₃ form by the secondary reaction between GdCl and the GdCl₃ electrolyte upon slow cooling. The new cluster compound Gd₅Cl₉C₂ which contains interstitial C₂ units is formed, when a graphite crucible is serving as cathode.     

Poly(vinyl pyridine-poly ethylene glycol methacrylate-ethylene glycol dimethacrylate) beads for heavy metal removal

Poly(vinyl pyridine-poly ethylene glycol methacrylate-ethylene glycol dimethacrylate) [poly(VP-PEGMA-EGDMA)] beads with an average size of 30–100 μm were prepared by suspension polymerization. Poly(VP-PEGMA-EGDMA) beads were characterized by swelling studies, scanning electron microscopy (SEM), elemental analysis, Fourier Transform Infrared Spectroscopy (FTIR). The beads with a swelling ratio of 65% were used for the heavy metal removal studies. Chelation capacity of the beads for the selected metal ions, i.e., Pb(II), Cd(II), Cr(III) and Cu(II) were investigated in aqueous media containing different amounts of these ions (5–80 mg/l) and at different pH values (2.0–10.0). The maximum chelation capacities of the poly(VP-PEGMA-EGDMA) beads were 18.23 mg/g for Pb(II), 16.50 mg/g for Cd(II), 17.38 mg/g for Cr(III) and 18.25 mg/g for Cu(II). The affinity order on mass basis was observed as follows: Cu(II) > Pb(II) > Cr(III) > Cd(II). pH significantly affected the chelation capacity of VP incorporated beads. Heavy metal adsorption on the poly(PEGMA-EGDMA) control microspheres was negligible. Regeneration of the chelating beads was easily performed with 0.1 M HNO₃. It was shown that these beads can be used effectively for heavy metal removal from aqueous solutions with repeatedly adsorption–desorption operations. These features show that poly(VP-PEGMA-EGDMA) beads are potential candidate sorbent for heavy metal removal.     

Electrochemical characterization of metastable pitting of 3003 aluminum alloy in ethylene glycol–water solution

The corrosion and electrochemical behavior of 3003 aluminum alloy in ethylene glycol–water solution were investigated by electrochemical techniques. It is found that the oxide film formed on aluminum depends on the dissolved oxygen in the solution. In the presence of oxygen, a layer of aluminum oxide film forms on the aluminum surface to protect the substrate from corrosion. In the absence of oxygen, the film formed is mainly aluminum-alcohol film that is less compact and less resistant to corrosion. The aluminum oxide film and aluminum-alcohol film have the different susceptibilities to chloride ion attack for pit initiation. There is a higher pitting susceptibility for aluminum oxide-covered electrode. The increase in temperature decreases the resistance of aluminum electrode to corrosion reaction. However, the resistance to pitting corrosion increases.     

乙二醇在Pd-CeO2/C催化剂上的电化学氧化

用交替微波加热法快速制备纳米CeO2/C复合材料,进而制备Pd-CeO2/C催化剂.首次用循环伏安和计时电位法研究了碱性溶液中乙二醇在该催化剂上的电化学氧化行为.实验结果表明,Pd-CeO2/C催化剂对乙二醇的电化学氧化比单纯的Pr/C催化剂具有更好的催化活性.稳态恒电流极化实验结果证明,Pd-CeO2/C催化剂对醇氧化产生的中间物有较好的抗毒化能力.     

Poly(ethylene glycol dimethacrylate-n-vinyl imidazole) beads for heavy metal removal

Poly(ethylene glycol dimethacrylate-n-vinyl imidazole) [poly(EGDMA-VIM)] hydrogel (average diameter 150-200 microm) was prepared by copolymerizing ethylene glycol dimethacrylate (EGDMA) with n-vinyl imidazole (VIM). The copolymer hydrogel bead composition was characterized by elemental analysis and found to contain 5 EGDMA monomer units each VIM monomer unit. Poly(EGDMA-VIM) beads had a specific surface area of 59.8 m2/g. Poly(EGDMA-VIM) beads were characterized by swelling studies and scanning electron microscopy (SEM). These poly(EGDMA-VIM) beads with a swelling ratio of 78% were used for the heavy metal removal studies. Chelation capacity of the beads for the selected metal ions, i.e., Cd(II), Hg(II) and Pb(II) were investigated in aqueous media containing different amounts of these ions (10-750 mg/l) and at different pH values (3.0-7.0). Chelation rate was very fast. The maximum chelation capacities of the poly(EGDMA-VIM) beads were 69.4 mg/g for Cd(II), 114.8 mg/g for Pb(II) and 163.5 mg/g for Hg(II). The affinity order on molar basis was observed as follows: Hg(II) > Cd(II) > Pb(II). Chelation behavior of heavy metal ions could be modelled using both the Langmuir and Freundlich isotherms. pH significantly affected the chelation capacity of VIM incorporated beads. Chelation of heavy metal ions from synthetic wastewater was also studied. The chelation capacities are 45.6 mg/g for Cd(II), 74.2 mg/g for Hg(II) and 92.5 mg/g for Pb(II) at 0.5 mmol/l initial metal concentration. Regeneration of the chelating-beads was easily performed with 0.1 M HNO3. These features make poly(EGDMA-VIM) beads potential candidate adsorbent for heavy metal removal.     

乙二醇法制备负载型钴基-堇青石催化剂及其催化燃烧甲苯的活性

用乙二醇法和浸渍法制备两种负载在堇青石上的钴基负载催化剂,并用XRD、XPS、TPR和TPD对制备的催化剂进行表征,比较两种催化剂催化氧化(燃烧)甲苯的活性。研究结果表明,与浸渍法制备的Co/cord催化剂相比,乙二醇法制备的催化剂Co/cord-EG对甲苯催化燃烧活性明显提高。应用乙二醇法制备Co/cord-EG负载型催化剂,Co元素主要以Co2+存在于载体表面;而传统浸渍法制备的Co/cord催化剂,Co元素是以Co2+与Co3+的两种化学状态存在于载体表面。应用乙二醇法制备Co/cord-EG负载型催化剂,有助于在载体表面形成比较均匀的吸附活性位。应用乙二醇法制备的Co/cord-EG催化剂,催化活性组分能在载体表面上以更小颗粒而且更高的分散度存在,从而能明显提高其催化活性。     

Ferromagnetic resonance in nanomagnetic metal core and noble metal shell systems

The change in the line widths in the ferromagnetic resonance (FMR) spectra of Co and Ni nanoparticles upon shell formation with noble metals like gold or silver are described. The Ni(core)Ag(shell), Co(core)Ag(shell), and CO(core)Au(shell) nanoparticles were prepared by a simple transmetallation reaction between the Co and Ni nanoparticles and the Ag+ or AuCl4- ions. It is revealed that the FMR line width decreases upon Ag shell formation whereas it increases upon core-shell composite formation with Au. Several probable explanations such as the differences in size distributions before and after the reaction or the changes occurring in shape anisotropy of the particles due to the shell formation or the different extents of electronic interaction between the core and shell materials have been offered for this observation.     

Near-field photochemical imaging of noble metal nanostructures

The sub-diffraction imaging of the optical near-field in nanostructures, based on a photochemical technique, is reported. A photosensitive azobenzene-dye polymer is spin coated onto lithographic structures and is subsequently irradiated with laser light. Photoinduced mass transport creates topographic modifications at the polymer film surface that are then measured with atomic force microscopy (AFM). The AFM images correlate with rigorous theoretical calculations of the near-field intensities for a range of different nanostructures and illumination polarizations. This approach is a first step toward additional methods for resolving confined optical near fields, which can augment scanning probe methodologies for high spatial resolution of optical near fields.     

Toward calculation of heat-engineering characteristics of two-phase thermosiphons filled with ethylene glycol I. Thermophysical properties of ethylene glycol

We present the results of experimental investigation and engineering correlations for determining the thermophysical properties of ethylene glycol. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 2, pp. 195–198, March–April, 1998.     

Low-temperature phase and morphology transformations in noble metal nanocatalysts

In situ real-time x-ray diffraction was used to study temperature-induced structural changes of 1-5 nm Au, Pt, and AuPt nanocatalysts supported on silicon substrates. Synchrotron-based x-ray diffraction indicates that the as-synthesized Au and Au(64)Pt(36) nanoparticles have a non-crystalline structure, while the Pt nanoparticles have the expected cubic structure. The nanoparticles undergo dramatic structural changes at temperatures as low as 120?°C. During low-temperature annealing, the Au and AuPt nanoparticles first melt and then immediately coalesce to form 4-5 nm crystalline structures. The Pt nanoparticles also aggregate but with limited intermediate melting. The detailed mechanisms of nucleation and growth, though, are quite different for the three types of nanoparticles. Most interestingly, solidification of high-density AuPt nanoparticles involves an unusual transient morphological transformation that affects only the surface of the particles. AuPt nanoparticles on silicon undergo partial phase segregation only upon annealing at extremely high temperatures (800?°C).     

乙二醇稳定的NaBH4还原法制备纳米Pt/C催化剂

分别采用乙二醇(EG)和H2O为溶剂,通过NaBH4还原法在酸性pH≤2和碱性pH≥12条件下制备了铂担裁量为20%(质量分数)的Pt/C催化剂,利用TEM、CV及LSV等方法对催化剂进行了表征与测试,考察了EG在NaBH4还原法中对铂纳米颗粒的稳定作用.结果表明,EG作溶剂、碱性pH≥12时,通过NaBH4还原法制备得到了平均粒径约2.5nm、粒径分布窄、在碳裁体上分散均匀的Pt/C催化荆;该催化剂的电化学比表面为74.4m2/g Pt,0.8V vs NHE时通过LSV得到的单位质量铂对甲醇电催化氧化的电流密度为229.1mA/mg Pt,分别是相同条件下H2O作溶剂时制备得到的Pt/C催化剂的5.倍和5.3倍.     

磁响应性贵金属核/壳纳米复合粒子制备研究进展

磁响应的贵金属核/壳结构复合纳米粒子具有不同于单组分纳米粒子更优越的多重功能,在催化剂、光学材料、生物传感器及生物医学领域具有重要前景。从核/壳结构类型出发,综述了具有磁响应的贵金属核/壳结构纳米复合粒子的化学制备与结构特征,并简要对其应用研究进展做了讨论。     

Conductive silver patterns via ethylene glycol vapor reduction of ink-jet printed silver nitrate tracks on a polyimide substrate

In this paper, we report using ethylene glycol vapor reduction approach to fabricate conductive silver tracks directly from silver nitrate solution by ink-jet printing. The silver nitrate precursor can be reduced in ethylene glycol vapor to form silver at low temperatures. X-ray diffraction, thermogravimetric analysis, and energy dispersive spectrometric analysis results indicate that the silver nitrate has been converted to silver completely. Using a high concentration silver nitrate solution, continuous silver conductive lines with a resistivity of 7.314 × 10^− 5 Ω cm have been produced, which is relatively close to the resistivity of bulk silver.     

工作用贵金属热电偶校准能力验证

JJG 141——2013《工作用贵金属热电偶检定规程》实施后,为了解我国校准贵金属热电偶的能力,中国合格评定国家认可委员会(CNAS)组织工作用贵金属热电偶校准能力验证,全国28个省、市、自治区的88家实验室参加。该研究主要介绍工作用贵金属热电偶校准能力验证计划的试验背景和实施过程,包括方案设计、样品制备、稳定性试验、结果统计等,并对能力验证结果进行分析。结果显示:校准工作用贵金属结果满意率为98.86%,参加能力验证的绝大多数实验室可以按照修订后的新规程准确校准工作用贵金属热电偶,我国校准工作用贵金属热电偶实验室具有较高的水平。     

Corrosion-electrochemical behavior of aluminum alloys in aqueous ethylene glycol media

Using the method of mathematical design of experiments, we have studied the influence of ethylene glycol concentration and temperature over a wide range of their variation on the corrosion of AMg₃ aluminum alloy. We have established that, irrespective of the ethylene glycol concentration, the maximum corrosion losses are observed at temperatures of 60–70°C. The inhibiting action of ethylene glycol at concentrations exceeding 40% is caused by an increase in the viscosity of the solutions and by the formation of slightly soluble surface complexes of aluminum with ethylene glycol and the products of its oxidation. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 6, pp. 86–93, November–December, 2007.