Gold dissolution in acidic thiourea and thiocyanate solutions

Gold dissolution in acidic solutions containing thiourea (Tu) and thiocyanate was studied using linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and surface enhanced Raman spectroscopy (SERS). A synergistic response found in that mixed ligand system promoted a higher dissolution rate than either lixiviant alone. The passivation of gold occurs in a Tu only solution, but when thiocyanate is mixed with Tu, passivation is significantly alleviated. The dissolution rate of gold in the mixed lixiviant system increases with increasing Tu and thiocyanate concentration. Results from LSV and EIS indicate that gold dissolution is controlled by a combination of charge transfer and diffusion in the mixed lixiviant system. The optimum concentration for Tu and thiocyanate is about 5 mM and 0.05 M, respectively for the rate of gold dissolution. SERS results suggest a possible formation of a mixed ligand complex involving the interaction of Au(Tu)₂⁺ and SCN⁻. Further study is necessary to identify the mixed ligand complex.     

镧（Ⅲ）与硫脲配合物的合成、表征及抗菌活性研究

本文报道了配合物LaI3.2CS（NH2）2.10H2O的合成方法,通过元素分析、X射线粉末衍射、红外光谱、核磁共振谱、质谱、差热——热重分析,确定了配合物的组成和结构,首次测定了配体和配合物的抗菌活性。     

Polymer Supported Synthesis of Multi-substituted Pyrimidine-4-one Derivatives via Pbf-activated Thiourea

Efficient polymer supported synthesis of multi-substituted pyrimidine-4-one derivatives was described.Target products were produced from fluorenylmethoxycarbonyl(Fmoc) protected β-amino acid loaded on hydroxymethyl resin through deprotection, N-alkylation, guanidine formation, and cleavage of 2,2,4,6,7-pentamethyl dihydrobenzofuran-sulfonyl(Pbf) by trifluoracetic acid(TFA) followed with cyclization. The procedure has the advantages of easy operation, mild reaction conditions, and forming multiple substituents.     

Adsorption and inhibitive corrosion properties of thiourea derivatives on cold rolled steel in 1 M HClO<Subscript>4</Subscript> solutions

Thiourea derivatives namely, phenylthiourea (PTU), N, N′-diphenylthiourea (DPTU) and N-naphtyl N′-phenylthiourea (NPTU) synthesised in our laboratory, were tested as inhibitors for the corrosion of cold rolled steel in 1 M HClO₄ using polarisation and electrochemical impedance measurements. At 30 °C, PTU and DPTU stimulated corrosion at low concentrations while addition of NPTU caused inhibition at all concentrations. The best protection (93%) was obtained by adding NPTU at 2.5 × 10⁻⁴ M. Polarisation curves showed that NPTU acted as a mixed inhibitor. The degree of surface coverage of the adsorbed inhibitors was determined by the ac impedance technique. The adsorption of NPTU on the cold rolled steel surface obeyed the Langmuir adsorption isotherm. Corrosion behaviour in the presence of NPTU at various concentrations was studied in the temperature range 20–50 °C. Both the corrosion rate of cold rolled steel and protection efficiency increased with increasing temperature. Activation energies with and without NPTU were obtained from the temperature dependence of corrosion current. The thermodynamic functions of the adsorption processes were calculated from the polarisation data and were used to analyse the inhibitor adsorption mechanism.     

钢铁件酸性镀铜前的预镀工艺研究

实验研究了钢铁件酸性镀铜前的预镀工艺，确定了硫脲浸铜工艺，讨论了工艺中各成分及含量对镀层结合力的影响，得到了硫脲浸铜工艺的成分及最佳含量，硫酸铜10—12g／L、硫酸75—100m/L、硫脲0.2—0.3g／L、添加剂8—10mL/L.由此工艺预浸后，再进行酸性镀铜，得到的镀层结合力良好。     

On the relationship between corrosion inhibiting effect and molecular structure

In order to relate the corrosion inhibition effect of organic compounds for steel in acid media to their molecular characteristics, SCF calculations have been performed for thiourea and nine derivatives, for two further sulphur-containing organic compounds and for urea and two derivatives. The structure of all compounds has been optimised, ionisation potential, dipole moments and the electron density distribution has been computed. It is seen that the dominant molecular parameter for the inhibition effect is the ionisation potential and that there is a clear relation between the increase in corrosion inhibition and the decrease of the ionisation potential.     

硫脲在0.5mol/L硫酸溶液中对A3钢缓蚀作用的电化学研究

为研究硫脲在硫酸溶液中对A3钢的缓蚀作用,并为实际生产中选用硫脲作为缓蚀剂的可行性评价提供参考,采用稳态极化曲线和电化学阻抗谱图(EIS)方法分别研究了A3钢在0.5mol/L硫酸溶液和0.5mol/L硫酸溶液+0.3g/L硫脲混合介质中的腐蚀行为.对硫脲在0.5mol/L硫酸溶液中对A3钢的缓蚀作用给出了评价,证明了硫脲在防止腐蚀的过程中对阴阳两极极化过程均有显著作用,并得出其为一种混合抑制型缓蚀剂的结论.     

硫脲／二氰二胺／环氧树脂潜伏固化体系

通过测定固化过程的凝胶化时间及红外光谱图,考察了硫脲及其衍生物对二氰二胺/环氧树脂体系的固化促进作用;讨论了硫脲及其衍生物/二氰二胺/环氧树脂体系的组成配比对固化特性、室温贮存性能和固化后粘合剪切强度的影响。     

Determination of the metastable zone and induction time of thiourea for cooling crystallization

The solubility,metastable zone width(MSZW),and induction time of thiourea for cooling crystallization were experimentally determined in the temperature range of 283-323 K. The solubility data could be well described by the Apelblat equation model as lnx=-99.55+1071.66/T+16.27 lnT. The determinations of the effects of various stirring and cooling rates indicated that the MSZW increased with increasing and decreasing cooling and stirring rates,respectively.Furthermore,the induction times at various temperatures and supersaturation ratios were also measured.The results indicated that homogeneous nucleation could occur at high supersaturation,whereas heterogeneous nucleation was more likely to occur at low supersaturation.Based on the classical nucleation theory and induction period data,the calculated solid-liquid interfacial tensions of thiourea in deionized water at 302.46 and 312.58 K were 2.86 and 2.94 mJ·m~(-2),respectively.     

超声波处理对纤维素碱脲体系溶解性能的影响

采用碱／尿素／水体系、碱／尿素／硫脲／水体系分别制备纤维素溶液,在溶解的不同阶段用超声波进行处理,并利用光学显微镜、偏光显微镜和X射线衍射对溶解效果进行表征。研究结果表明：溶解之前对纤维素原料的超声波处理主要是对纤维形态结构和超分子结构的破坏,略微增大溶解度;溶解过程中对纤维素溶液超声波处理则可以强化润胀,促进分散,显著增大纤维素的溶解度;在碱／尿素／水体系中超声波对溶解的促进作用强于在碱／尿素／硫脲,水体系中。