TINDAKAN LEMBAGA PEMASYARAKATAN DALAM PEMBINAAN PELAKU TINDAK PIDANA BERLATAR BELAKANG ALIRAN SESAT (SUATU PENELITIAN DI RUTAN KELAS II B BANDA ACEH DAN RUTAN CABANG LHOKNGA)

Banda Ace

Electrodeposition of copper from mixed sulphate–chloride acidic electrolytes at rotating disc electrode

The effect of chloride ion on the deposition of copper from low metal concentrations in aqueous, acid sulphate solutions was investigated. The electrolytes contained 0·05 mol dm?3 CuSO4 and 0·5 mol dm?3 Na2SO4 at pH 2 and 296 K. The chloride ion concentration was varied in a wide range from 0·03 to 2·0 mol dm?3. Linear sweep voltammetry was carried out under well defined flow conditions at a smooth platinum rotating disc electrode. The progressive transition from a single, two-electron reaction for the reduction of Cu(II)?Cu(0) to two, single-electron reactions for the reduction sequence: Cu(II)?Cu(I)?Cu(0) was clearly evident as the chloride ion concentration increased. The charge transfer and mass transport characteristics of these reactions were evaluated. The formal potential for the Cu II) reduction to Cu(I), the shift in the potential region for complete mass transport controlled reduction of Cu(I) to Cu(0) and the potential for hydrogen evolution at the deposited copper were also studied. A semi-logarithmic relationship between exchange current density and half-wave potential for Cu(II)?Cu(I) with chloride ion was achieved when the Cl?/Cu(II) ratio in the electrolytes exceeded 2, due to the presence of the Cu(I) dichlorocuprous anion, CuCl2?

Strategies for the determination of the convective-diffusion limiting current from steady state linear sweep voltammetry

The limiting current is an important parameter for the characterization of mass transport in electrochemical systems operating under convective-diffusion control. Four methods to determine the limiting current from current (I) vs. potential (E) plots are considered. Strategies to determine the limiting current values include: 1) direct measurement from I vs. E curves, 2) estimation from the current value at EL =DE/2 where DE is the length of the limiting current plateau), 3) evaluation of the first derivative dI/dE in the I vs. E curve and 4) from plots of E/I vs. I-1. The electrode reactions chosen to demonstrate the different strategies are: Cu(II) ? Cu(I) and Cu(I) ? Cu(0) in 1.5 mol dm-3 NaCl (pH 2) at a platinum rotating disc electrode and K3Fe(CN)6 ? K4Fe(CN)6 in 1 mol dm-3 NaOH at a 60 ppi reticulated vitreous carbon electrode (RVC)

Copper deposition at segmented, reticulated vitreous carbon cathode in hull cell

The electrodeposition of copper from an acid sulphate solution has been studied in a Hull cell fitted with four types of cathode; a carbon plate or a reticulated vitreous carbon (RVC) sheet was used either in a continuous or segmented form. The rates of mass transport to the planar plate and RVC electrodes have been compared in static and stirred electrolytes containing 50, 75 and100 mmol dm23 CuSO4 in 0?5 mol dm23 Na2SO4 at pH 2 and 298 K. The cathodes were divided into 10 equal sections and current vs. potential curves were obtained for each section at a constant current up to 140 mA. The current distribution over the cathodes followed a logarithmicdecay with distance along the cathode; segments nearest to the anode experienced the highest rate of copper deposition

Normal and anomalous electrodeposition of tin–copper alloys from methanesulphonic acid bath containing perfluorinated cationic surfactant

Sn–Cu alloys were deposited from a 12?5 vol.-% (1?93 mol dm23) methanesulphonic acid bath containing a perfluorinated, cationic surfactant at 296 K. Electrodeposition was carried out under controlled flow conditions, using rotating disc, rotating cylinder and rotating cylinder Hull cell electrodes. The influences of deposition current and potential, rotation speed, cupric ion concentration, stannous ion level and surfactant concentration on the deposited alloy composition have been investigated. The presence of surfactant resulted in a shift in the Cu deposition potential compared to that of Sn deposition. Both ‘normal’ deposition (Cu deposited at a more positive potential than Sn) and ‘anomalous’ deposition (Sn deposited at a more positive potential than Cu) could be achieved. A series of Sn–Cu alloys was electrodeposited over a wide range of operating conditions to produce matte grey through golden yellow to light brown, surface finishes. Golden yellow coloured bronze deposits, containing 70–80 wt-% Cu and 20–30 wt-%Sn could be obtained. When Sn was deposited preferentially, the Cu content of the alloy was typically in the range 3–9 wt-% along the cathode of the rotating cylinder Hull cell

Anodic deposition of compact, freely-standing or microporous polypyrrole films from aqueous methanesulphonic acid

Freely-standing and flexible films (0.075 to 9 mm in thickness) of electrically conducting polypyrrole were synthesised via anodic electrodeposition onto a stainless steel substrate from methanesulphonic acid under stirred conditions at 295 K. Cyclic voltammetry was used to studythe effect of pyrrole monomer concentration (0.01 to 1.0 mol dm-3) and methanesulphonic acid level (1.0 to 6.0 mol dm-3) on the formation of polypyrrole films. The films were prepared for deposition times of 30–240 s at constant current densities of 1 to 15 mA cm-2. The ionic conductivity of freely-standing polypyrrole membranes in aqueous methanesulphonic acid was studied. Scanning electron microscopy was used to image the surface microstructure. The polypyrrole films, which were prepared in the oxidised (methanesulphonate doped), conductivestate, showed an ionic area resistance as low as 10 ohm cm2. The films were readily doped with the methanesulphonate anion and the membrane ionic conductivity was dependent on the electrolyte composition used for their deposition. In the presence of anodic oxygen evolution, thefilms showed a ‘template-free’ porosity due to film growth around the bubbles

Numerical simulation of the current, potential and concentration distributions along the cathode of a rotating cylinder Hull cell

Numerical simulations of the non-uniform current, potential and concentration distributions along the cathode of a rotating cylinder Hull (RCH) cell (RotaHull® cell) are performed using finite element methods. Copper electrodeposition from an acid sulfate electrolyte is used as a test system. Primary, secondary and tertiary current distributions are examined. The importance of controllable and uniformly accessible hydrodynamics along the length of the RCH cathode is demonstrated. Charge transfer kinetics are described by a Tafel approximation while mass transport is considered using a Nernstian diffusion layer expression. The effects of applied current density and electrode rotation speeds on the distribution of potential and current along the RCH cathode are investigated. An expression of the primary current distribution and a dimensionless mass transport correlation facilitate comparisons with the simulations

Electrodeposition of composite coatings containing nanoparticles in a metal deposit

Recent literature on the electrodeposition of metallic coatings containing nanosized particles is surveyed. The nanosized particles, suspended in the electrolyte by agitation and/or use of surfactants, can be codeposited with the metal. The inclusion of nanosized particles can give (i) an increased microhardness and corrosion resistance, (ii) modified growth to form a nanocrystalline metal deposit and (iii) a shift in the reduction potential of a metal ion. Many operating parameters influence the quantity of incorporated particles, including current density, bath agitation (or movement of work piece) and electrolyte composition. High incorporation rates of the dispersed particles have been achieved using (i) a high nanoparticle concentration in the electrolyte solution, (ii) smaller sized nanoparticles; (iii) a low concentration of electroactive species, (iv) ultrasonication during deposition and (v) pulsed current techniques. Compositional gradient coatings are possible having a controlled distribution of particles in the metal deposit and the theoretical models used to describe the phenomenon of particle codeposition within a metal deposit are critically considered