Abstract: A surface of an electrolytically dissolvable material, e.g., an electrolytically dissolvable metal, is smoothed by a two-step electrochemical process wherein a the surface to be smoothed and a counterelectrode are contacted with an electrolyte and an electric current is passed between the substrate and counterelectrode, with the substrate as the anode. In a first step relatively large asperities on the substrate are reduced in height by maintaining a macroprofile regime by using a pulsed electric current with short pulses. In a second step, small asperities and the remainder of the large asperities are reduced or removed by maintaining a microprofile regime by using a pulsed current having longer pulses or a direct current.

Abstract: The interior of cavities and through-holes in electrically conductive substrates having high-aspect ratios of 8:1 or greater can be electroplated with a uniform layer of metal on their interior surfaces by using a pulse reverse voltage waveform having a pulse train of long cathodic pulses followed by short anodic pulses even in the absence of conventional additives such as levelers and brighteners.

Abstract: Microscopic mechanical elements suitable for manufacture of microelectromechanical systems (MEMS) are directly prepared by forming a low-relief base of microscopic dimensions on a substrate surface by any conventional means, and electrodepositing a metal preferentially on the upper surface of the base to produce a vertically-extending 3-dimensional structure. In a first step, the patterned substrate and a counterelectrode are contacted with an electrolyte and an electric current is passed between the substrate and counterelectrode, with the substrate being predominantly cathodic with respect the counterelectrode.

Abstract: A layer of a metal is electroplated onto an electrically conducting substrate having a generally smooth surface with a small recess therein, having a transverse dimension not greater than about 350 micrometers, typically from about 5 micrometers to about 350 micrometers, by immersing the substrate and a counterelectrode in an electroplating bath of the metal to be electroplated and passing a modulated reversing electric current between the electrodes. The current contains pulses that are cathodic with respect to said substrate and pulses that are anodic with respect to said substrate. The cathodic pulses typically have a duty cycle less than about 50% and the anodic pulses have a duty cycle greater than about 50%, the charge transfer ratio of the cathodic pulses to the anodic pulses is greater than one, and the frequency of the pulses ranges from about 10 Hertz to about 12000 Hertz. The on-time of the cathodic pulses may range from about 0.83 microseconds to about 50 milliseconds.

Abstract: A continuous layer of a metal is electrodeposited onto a substrate having both hydrodynamically inaccessible recesses and hydrodynamically accessible recesses on its surface by a two-step process in which the hydrodynamically inaccessible recesses are plated using a pulsed reversing current with cathodic pulses having a duty cycle of less than about 50% and anodic pulses having a duty cycle of greater than about 50% and the hydrodynamically accessible recesses are then plated using a pulsed reversing current with cathodic pulses having a duty cycle of greater than about 50% and anodic pulses having a duty cycle of less than about 50%.

Abstract: Electrochemical machining of metals and alloys is accomplished by using a pulsed electric current incorporating modulated reverse electric current. Reverse (cathodic) pulses are interposed between forward (anodic) pulses. The process is useful for electrochemical shaping of metals, electrochemically polishing metal surfaces, and electrochemical deburring of metal articles. The process is especially useful for electrochemical processing of metals and alloys that readily form passive surface layers.

Abstract: A layer of a metal is electroplated onto an electrically conducting substrate having a generally smooth surface with a small recess therein, having a transverse dimension not greater than about 350 micrometers, typically from about 5 micrometers to about 350 micrometers, by immersing the substrate and a counterelectrode in an electroplating bath of the metal to be electroplated and passing a modulated reversing electric current between the electrodes. The current contains pulses that are cathodic with respect to said substrate and pulses that are anodic with respect to said substrate. The cathodic pulses typically have a duty cycle less than about 50% and the anodic pulses have a duty cycle greater than about 50%, the charge transfer ratio of the cathodic pulses to the anodic pulses is greater than one, and the frequency of the pulses ranges from about 10 Hertz to about 12000 Hertz. The on-time of the cathodic pulses may range from about 0.83 microseconds to about 50 milliseconds.

Abstract: A continuous layer of a metal is electrodeposited onto a substrate having both hydrodynamically inaccessible recesses and hydrodynamically accessible recesses on its surface by a twostep process in which the hydrodynamically inaccessible recesses are plated using a pulsed reversing current with cathodic pulses having a duty cycle of less than about 50% and anodic pulses having a duty cycle of greater than about 50% and the hydrodynamically accessible recesses are then plated using a pulsed reversing current with cathodic pulses having a duty cycle of greater than about 50% and anodic pulses having a duty cycle of less than about 50%.

Abstract: A smooth layer of a metal is electroplated onto a microrough electrically conducting substrate by immersing the substrate and a counterelectrode in an electroplating bath of the metal to be electroplated and passing a modulated reversing electric current between the electrodes. The current contains pulses that are cathodic with respect to said substrate and pulses that are anodic with respect to said substrate. The cathodic pulses have a duty cycle less than about 50% and said anodic pulses have a duty cycle greater than about 50%, the charge transfer ratio of the cathodic pulses to the anodic pulses is greater than one, and the frequency of said pulses ranges from about 10 Hertz to about 12000 Hertz. The plating bath is substantially devoid of levelers and may be devoid of brighteners.

Abstract: Excessive evolution of hydrogen in electrolytic deposition of metals on a cathode substrate can be controlled by using a pulsed reverse current. Reverse current pulses interposed between the forward current pulses consume at least some of the nascent hydrogen and prevent the local pH at the cathode surface from becoming excessively alkaline. Control of hydroxide ion concentration by pulsed reverse current alleviates problems caused by reaction of metal-bearing-ions with hydroxide ions generated near the cathode by evolution of hydrogen. The method is useful in depositing functional chromium coatings on electrically conductive substrates from plating baths comprising aqueous solutions of trivalent chromium salts. In such a method the current comprises forward pulses having a duty cycle of from about 50% to about 90% and reverse pulses having a duty cycle of from about 5% to about 30%, and a frequency of from about 5 Hz to about 700 Hz.

Abstract: A smooth layer of a metal is electroplated onto a microrough electrically conducting substrate by immersing the substrate and a counterelectrode in an electroplating bath of the metal to be electroplated and passing a modulated reversing electric current between the electrodes. The current contains pulses that are cathodic with respect to said substrate and pulses that are anodic with respect to said substrate. The cathodic pulses have a duty cycle less than about 50% and said anodic pulses have a duty cycle greater than about 50%, the charge transfer ratio of the cathodic pulses to the anodic pulses is greater than one, and the frequency of said pulses ranges from about 10 Hertz to about 12000 Hertz. The plating bath is substantially devoid of levelers and may be devoid of brighteners.

Abstract: A continuous layer of a metal is electrodeposited onto a substrate having both hydrodynamically inaccessible recesses and hydrodynamically accessible recesses on its surface by a two-step process in which the hydrodynamically inaccessible recesses are plated using a pulsed reversing current with cathodic pulses having a duty cycle of less than about 50% and anodic pulses having a duty cycle of greater than about 50% and the hydrodynamically accessible recesses are then plated using a pulsed reversing current with cathodic pulses having a duty cycle of greater than about 50% and anodic pulses having a duty cycle of less than about 50%.

Abstract: A layer of a metal is electroplated onto an electrically conducting substrate having a generally smooth surface with a small recess therein, having a transverse dimension not greater than about 350 micrometers, by immersing the substrate and a counterelectrode in an electroplating bath of the metal to be electroplated and passing a modulated reversing electric current between the electrodes. The current contains pulses that are cathodic with respect to said substrate and pulses that are anodic with respect to said substrate. The cathodic pulses have a duty cycle less than about 50% and said anodic pulses have a duty cycle greater than about 50%, the charge transfer ratio of the cathodic pulses to the anodic pulses is greater than one, and the frequency of said pulses ranges from about 10 Hertz to about 12000 Hertz. The plating bath may be substantially devoid of levelers and/or brighteners.

Abstract: A layer of a metal is electroplated onto an electrically conducting substrate having a generally smooth surface with a small recess therein, having a transverse dimension not greater than about 350 micrometers, typically from about 5 micrometers to about 350 micrometers, by immersing the substrate and a counterelectrode in an electroplating bath of the metal to be electroplated and passing a modulated reversing electric current between the electrodes. The current contains pulses that are cathodic with respect to said substrate and pulses that are anodic with respect to said substrate. The cathodic pulses have a duty cycle less than about 50% and said anodic pulses have a duty cycle greater than about 50%, the charge transfer ratio of the cathodic pulses to the anodic pulses is greater than one, and the frequency of said pulses ranges from about 10 Hertz to about 5000 Hertz.

Abstract: A smooth layer of a metal is electroplated onto a microrough electrically conducting substrate by immersing the substrate and a counterelectrode in an electroplating bath of the metal to be electroplated and passing a modulated reversing electric current between the electrodes. The current contains pulses that are cathodic with respect to said substrate and pulses that are anodic with respect to said substrate. The cathodic pulses have a duty cycle less than about 50% and said anodic pulses have a duty cycle greater than about 50%, the charge transfer ratio of the cathodic pulses to the anodic pulses is greater than one, and the frequency of said pulses ranges from about 10 Hertz to about 5000 Hertz.

Abstract: A gas diffusion electrode for a proton exchange membrane fuel cell is prepared by electrodeposition of a catalytic metal in nanocrystalline form on a substrate by contacting an electrically conductive substrate and a counterelectrode with a plating bath containing ions of a metal to be deposited on the substrate and passing a pulsed electric current between the substrate and counterelectrode having pulses that are cathodic with respect to the substrate and have a short on-time and/or a short duty cycle with a frequency from about 10 hertz to about 5000 hertz. In a preferred embodiment the electric current is a modulated reversing electric current having pulses that are cathodic with respect to the substrate and pulses that are anodic with respect to the substrate, the cathodic pulses having a short on-time and/or short duty cycle, the charge transfer ratio of the cathodic pulses to the anodic pulses being greater than one, and the frequency of the pulses ranging from about 10 hertz to about 5 kilohertz.

Abstract: Metal salts are removed from solution in an electrolyte by subjecting the solution to electrolysis in a cell having an anode that has an anion exchange membrane closely associated therewith which sequesters the anion of the salt. The cathode may also be provided with a closely associated cation exchange membrane that sequesters, at least partially, the cation of the salt. A metal salt solution can be regenerated by reversing the polarity of the electrodes and conducting an electrolysis using fresh electrolyte.

Abstract: In the disclosed electrochemical cell for the production of an alkaline solution of peroxide, especially on-site production, the electrolyte is divided into an aqueous alkaline catholyte and an aqueous alkaline anolyte, and the cathode is a gas-diffusion electrode. The active material of the electrolyte side of the gas-diffusion cathode comprises a particulate catalyst support material having a surface area of about 50 to about 2000 m.sup.2 /g, and, deposited on the particles of this support material, 0.1 to 50 weight-%, based on the weight of the active layer, of gold or gold alloy particles having an average size >40 but less than about 200 .ANG.. These gold or gold alloy particles are substantially selectively catalytic for the reduction of oxygen to peroxide (e.g. HOO.sup..crclbar.). The electrolyte flow patterns are designed to avoid loss of peroxide resulting from oxidation at the anode. In the operation of the cell, a product with a hydroxyl:perhydroxyl ratio lees than 2:1 can be obtained.

Abstract: In the disclosed electrochemical cell for the production of an alkaline solution of peroxide, especially on-site production, the electrolyte is divided into an aqueous alkaline catholyte and an aqueous alkaline anolyte, and the cathode is a gas-diffusion electrode. The active material of the electrolyte side of the gas-diffusion cathode comprises a particulate catalyst support material having a surface area of about 50 to about 2000 m.sup.2 /g, and, deposited on the particles of this support material, 0.1 to 50 weight-%, based on the weight of the active layer, of gold or gold alloy particles having an average size >40 but less than about 200.ANG.. These gold or gold alloy particles are substantially selectively catalytic for the reduction of oxygen to peroxide (e.g. HOO.sup..crclbar.). The electrolyte flow patterns are designed to avoid loss of peroxide resulting from oxidation at the anode. In the operation of the cell, a product with a hydroxyl:perhydroxyl ratio less than 2:1 can be obtained.

Abstract: A waste solution containing electroactive species, e.g., metal ions, can be remediated to very low levels of contaminant by an electrolysis method including the steps of introducing an electrolyte containing an electroactive species into an electrolytic cell having a cathode and an anode, producing a flow of the electrolyte past at least one of the electrodes at an electrolyte flow rate, and passing an electric current through the solution between the anode and the cathode whereby the electroactive species undergoes an electrochemical reaction at one of the electrodes at an electrochemical reaction rate, using an electric current pulsed at a frequency of 0.5 to 1000 Hertz and a duty cycle of not greater than 50%, and adjusting the electrolyte flow rate for the pulsed current electrolysis such that the electrochemical reaction rate for pulsed current electrolysis is greater than the electrochemical reaction rate for direct current electrolysis.