银币表面自组装膜抗变色性能及成膜机理  

Anti-tarnish Characteristics and Formation Mechanism of Self-Assembled Monolayers on Surface of Silver Coins

作　　者：梁成浩[1] 杨长江[2] 黄乃宝[1] 金光明[1] 

机构地区：[1]大连海事大学,辽宁大连116026 [2]昆明理工大学,云南昆明650093

出　　处：《稀有金属材料与工程》2013年第7期1411-1417,共7页Rare Metal Materials and Engineering

基　　金：国家高技术研究发展计划项目(2009AA05Z120)

摘　　要：利用化学方法在银币表面制备了十八烷基硫醇组装膜(C18SHSAMs),并通过电化学技术研究了其在0.5mol/LNaCl+0.01mol/LNa2S溶液中的抗变色性能。结果表明:银表面形成SAMs后腐蚀电位正移30mV;阴极氧去极化和阳极银的硫化过程均受到抑制,对阴极极化过程的阻滞作用较阳极极化过程明显;银表面成膜后,容抗弧、电荷传递系数Rt增大,双电层电容Cd降低。有效提高银币的抗变色性能。银表面C18SHSAMs的形成过程符合两阶段模型。膜初始吸附阶段(I)为2级Langmuir吸附,重整结晶阶段(Ⅱ)为1级Langmuir吸附,动力学公式分别为,Ⅰ阶段:ctctt11.7061.706,Ⅱ阶段:0.5471ectt。速率常数与温度的关系为ln(k)=–5826/T+26.5,自组装过程表观活化能E=48.4kJ/mol,化学吸附为控制步骤。Octadecanethiol （ClsSH） self-assembled monolayers （SAM） were prepared on the silver coin surface. The anti-tarnish characteristics of C18SH SAMs were investigated in 0.5 mol/L NaCI＋0.01 mol/L Na2S solution by an electrochemical technique. The results indicate that silver＇s corrosion potential moves by 30 mV to positive direction after forming SAMs. C^sSH SAMs could inhibit oxygen depolarization and silver sulfuration. The inhibition effect for cathode process is better than that for anode. After SAMs is formed on the surface of silver, the silver coin＇s charge-transfer resistance increases and double layer capacitance decreases. The formation of SAMs on silver is in accordance with a two-phase model. In the initial stage, the adsorption obeys two grade Langmuir equation, which is θ（t）=1.706ct/1＋1.706ct . In the latter stage, the adsorption is the process of reforming and recrystallization, and is in accordance with one 1 ＋ 1.706ct grade Langmuir equation, which isθ（t）：1-e^（-0.547ct） . The relationship between rate constant and temperature is ln（k）=-5826/T＋26.5 during absorption. The apparent activation energy of self-assembled process is 48.4 kJ/mol and the self-assembled process is controlled by chemical adsorption

关 键 词：银币 抗变色 自组装膜 成膜机理 

分 类 号：TG174.4[金属学及工艺—金属表面处理]