Dark Film Research Articles

Reduction of Nitric Acid to Hydroxylamine at Glassy Carbon Surfaces Modified by the Reduction of p-Phenylenediamine and p-Aminophenol in 1.0 M Nitric Acid: A Scanning Electrochemical Microscopy Study

The scanning electrochemical microscope (SECM) was used to study the electrochemical reduction of nitric acid to hydroxylamine at modified glassy carbon (GC) electrodes. The GC surface was modified by holding it at a negative potential in solutions of p-aminophenol, or p-phenylenediamine in 1.0 M nitric acid. The generated products were detected in generation/collection experiments with an SECM Pt ultramicroelectrode. The films that form on GC, apparently polymers of a quinone imine intermediate, can also be grown under similar conditions on indium tin oxide (ITO) coated glass electrodes and appeared as dark orange-brown films. Atomic force microscope imaging revealed a highly porous structure. SECM and cyclic voltammetry studies showed that as a result of this surface filming, the GC electrodes exhibited an increase of at least 1 V in the hydrogen overpotential relative to the unmodified surface and the efficiency of the electrochemical reduction of nitric acid to hydroxylamine was dramatically enhanced. Bulk electrolysis of nitric acid at carbon in the presence of p-phenylenediamine resulted in a 75 to 85% current efficiency for hydroxylamine production at current densities of 0.5 to 0.8 A/cm2. This procedure proved to be useful for the large-scale electrochemical production of hydroxylamine from nitric acid at an electrode other than liquid mercury. © 2001 The Electrochemical Society. All rights reserved.

Diamond growth reactor chemistry and film nucleation enhancement using chlorinated hydrocarbons

The chemistry of diamond film growth from chlorinated hydrocarbons has been investigated using a hot filament reactor coupled to an orifice sampling mass spectrometer. The relative concentrations of the species present near the growth surface have been determined as a function of filament temperature for dilute mixtures of CH 4, CH 3Cl, CH 2Cl 2 and CHCl 3 in H 2. Mass spectral analysis indicated that chlorinated hydrocarbons are sequentially dechlorinated in the presence of hydrogen at moderate reactor temperatures. A dark film was deposited on all surfaces of the reactor during studies of this dechlorination of CHCl 3. Raman analysis indicated that these deposits are small particle polycrystalline graphite. Pretreatment of a Si 〈111〉 substrate under conditions that create the graphite deposit is seen to produce a significant nucleation enhancement of diamond when followed by growth at a higher temperature. Chemical mechanisms for some of these processes are proposed.

Investigation of low-reflective ZrCN–PVD-arc coatings for application on medical tools for minimally invasive surgery

Medical tools for minimally invasive surgery are often used under difficult environmental conditions. If the surgeons have to work with a microscope, the operating area must be brightly lit. Reflection and scattering of light from tool-surfaces disturb the visual field. To decrease this kind of disturbance, the tools can be covered by a dark PVD thin film. In the present study, the properties of low-reflective PVD-arc coatings of ZrCN were considered in comparison to TiCN. Different pure metal targets of zirconium and titanium were utilized in a reactive arc-coating process. The coating device was an industrial PVD engine of the HTC 1000/4 ABS type. Caused by the purpose of aimed investigations the engine merely operated in the arc-coating-mode. Amounts of carbon and nitrogen in the layers were steered by systematic changes of gas flow parameters from batch-to-batch. Substrate temperature and bias voltage were held at constant levels. Besides some mechanical and optical properties, aspects of biocompatibility of ZrCN on stainless steel AISI 304 were focused on. Summarizing the obtained results with regard to questions of biocompatibility, all of the investigated thin films have fulfilled the requirements for short-term applications to the human body.

Synthesis of a Thienothiophene Conjugated Polymer

A new conducting polymer was prepared by chemical and electrochemical polymerization of 3,6-dimethylthieno[3,2-b]thiophene. The galvanostatic deposition afforded uniform, adherent and dark blue films of PDMTT. Electrochemical characterization by cyclic voltammetry showed that it can be repeatedly driven between the doped and undoped species with a coulombic efficiency of nearly 100%.

Establishment of Hybrid Arctic Bramble under Field Conditions

The effect of different factors on plant diameter and yield in hybrid arctic bramble (Rubus arcticus nothosubsp. stellarcticus) was examined in two field experiments with a factorial design. The studied factors included planting time (August, September, May or June), plant type (bare-rooted or potted plants) and ground cover (no ground cover or mulching with a dark plastic film). Development of bare-rooted and potted plants did not differ when transplanted in the autumn and in May. Potted plants developed better than bare-rooted plants when transplanted in June. In one year, plants transplanted in May developed best, while in another, plants transplanted in the autumn developed best. Mulching with a dark plastic film improved plant development. The rate of vegetative development during the first growth season was reflected in the yields in both the first and the second harvest year; the greater the plant diameter after the first growth season, the higher the yield.

Contribution to the study of the solid-state reaction of mercury with pure rhodium

Thermogravimetry (TG) and other analysis techniques (EDX, SEM, Mapping surface, X-ray diffraction, inductively coupled argon plasma emission spectroscopy and atomic spectrometry with cold vapor generation) were used to study the reaction of Hg with Rh. The results permitted the suggestion that, when subjected to heat, an electrodeposited Hg film reacts with Rh to form intermetallic products with different stabilities, as indicated by at least three mass loss steps. In the first step, between room temperature and 160°C, only the bulk Hg is removed. From this temperature up to about 175°C, the mass loss can be attributed to the desorption of a film of metallic Hg. The last step, from 175 to 240°C, can be ascribed to the removal of Hg from a thin dark film of RhHg2 .

Electrochemical pitting behaviour of type 321 stainless steel in sulfide-containing chloride solutions

The pitting behaviour of type 321 stainless steel in sulfide-containing chloride aqueous environments was studied using cyclic potentiodynamic polarization. A well-established correlation between H2S and Na2S2O3 in the study of corrosion was applied, that is, H2S was simulated by Na2S2O3. The major factors affecting the pitting corrosion of type 321 stainless steel are the Cl- concentration, solution pH and temperature. The results clearly indicate that both Epit and Epp decrease with increasing Cl- concentration and temperature, while Ipass is more sensitive to temperature variation. Epit decreased with decreasing pH in the range 2 < pH < 7.5. The surface morphology and chemistry of the corroded type 321 stainless steel resulting from anodic polarization in 0.01 M S2O32--containing Cl- solution were analysed by XRD, SEM and EPMA. A higher concentration of sulfur was found in the pits, and the dark surface film was mainly composed of FeS and γ-Fe2O3. The results describe the pitting behaviour of type 321 stainless steel in sulfide-containing Cl- aqueous environments.

Vibrational and optical properties of carbon nitride films prepared by reactive magnetron sputtering

Carbon nitride films were prepared by reactive magnetron sputtering of a graphite target in a nitrogen atmosphere at different pressures and temperatures. The films were characterized by infrared, Raman and ultraviolet-visible spectroscopies, as well as by ellipsometry. We obtained hydrogen-free dark films when a negative bias was applied to the substrates; the samples prepared at room temperature without bias were soft and hydrogen could be detected in their infrared spectra. The most prominent features, between 1000 and 1700 cm-1, in both the Raman and infrared spectra were modelled using two Gaussian curves. As the nitrogen content was varied, the ratio between their areas followed opposite trends in the Raman and the infrared spectra. The presence of hydrogen caused the main feature to absorb more strongly at lower frequencies but did not alter the trend. The presence of six and five membered heteroaromatic rings is suggested to explain the increase of the infrared vibrations associated with double conjugated double bonds. The index of refraction can be correlated with features in the infrared spectra, suggesting that its value increases as the number of carbon and nitrogen double bonds increases. Ion bombardment reduces nitrogen incorporation; it is responsible for the densification of the films and the introduction of several defects that make films prepared under bias more absorbing in the low energy region.

Electropolymeric generation of optically active polypyrrole

The facile synthesis of optically active polypyrrole has been achieved via the enantioselective electropolymerization of pyrrole on indium-tin-oxide-coated glass electrodes in aqueous solution containing D-(+) or L-(−) tartaric acid, (IS)-(+)-10-camphorsulfonic acid and L-lactic acid. The dark films of conducting polypyrroles salt formed under electrostatic conditions (+0.65V vs. Ag AgCl ) exhibited strong circular dichroism (CD) spectra typical of polymers possessing helical chirality. The quantitative reversal of the CD spectrum of the salt grown in (+)-tartaric acid as opposed to (−)-tartaric acid suggests that electropolymerization is highly enantioselective, with one helical screw of the polymer chain being preferentially produced depending on the hand of the tartaric anion incorporated.

The laser film digitizer: density, contrast, and resolution.

This work evaluates differences in density linearity, contrast, and resolution of digital images acquired from a laser film scanner. A calibrated photographic step tablet tested linearity of diffuse optical density (OD). It was digitized within center openings of a dark and light film. The 14- x 17-inch films were scanned into 1024 x 1280 picture elements of 8 bits. A photographic tapered resolution guide evaluated the scanner's detail resolution. A single characteristic curve adequately represents the rate of change of OD per pixel value, but two piecewise linear functions are better. One ranges in light OD and a second in dark OD. Contrast shows a steeper slope in a light film rather than a dark film, yet a greater difference exists between two identical digitizers. The resolution test diminishes at 1.3 line pairs per mm (LP/mm), which compares to a Nyquist limit of 1.44 LP/mm. Such density, contrast, and resolution tests yield a benchmark to assure quality operations.

Preparation of polyacenic semiconductive thin films by excimer laser ablation

Polyacenic semiconductive thin films (PAS-TFs) were prepared onto a quartz or a KBr substrate by excimer laser ablation at 308 nm of a bulk phenol-formaldehyde (PF) resin and the bulk of a PAS material which was obtained by heat treatment of the PF resin at 535 °C (pyrolytic PAS (535 °C)). These were homogeneous brown and/or dark brown thin films consisting of fine particles. The electric conductivities of the films thus prepared from PF resin and pyrolytic PAS(535 °C) were about 10 −8 and 10 −5 S cm −1 at room temperature, respectively. Remarkable increase of electric conductivities was achieved on increasing the substrate temperature during the deposition process. In particular, the conductivity of the film from pyrolytic PAS (535 °C) reached more than 10 −2 S cm −1, which is comparable to that of bulk PAS material prepared by pyrolytic treatment at 775 °C, when deposited on a substrate at 300 °C.

Protective ability of chromate passive films on electrodeposited zinc-tin alloys

The protective ability of passive chromate films on electrodeposited ZnSn alloys (tin content of up to 20%) was studied using a double-cell electrochemical method according to Paatsch. Samples of the same chromate films on zinc deposits were studied for comparison. Three new compositions of chromating solution for electrodeposited ZnSn(15%) alloy are suggested and appropriate ratios of Cr VI to activating ion are proposed. Tests of the chromate films, revealing the best protective ability according to the Paatsch method, as well as of non-passivated zinc and ZnSn(15%) deposits, were carried out in a salt spray chamber. The results of the two methods show good agreement. The colourless and dark yellow films on the alloy reveal better corrosion stability than the films on pure zinc deposits. The surface morphology of the passive films and changes in the morphology after corrosive treatment in 5% NaCl were also studied.

Composition of passive chromate films on a ZnSn alloy

The compositions of three types of passive chromate film on an electrodeposited ZnSn alloy containing 15% Sn were studied both at the surface and at depth by X-ray photoelectron spectroscopy (XPS). Samples of dark yellow chromate films on zinc were used for comparison. The elemental and chemical compositions of chromate films formed on the ZnSn alloy were determined. Differences in the compositions on the surface and in the depth of the films were established. The presence of metallic tin and its compounds was also detected. Changes in the film composition were established after treatment in 5% NaCl. The dark yellow film on ZnSn coating showed the lowest permeability in the corrosive medium studied. The results obtained suggest that the film thickness increases in the order: colourless, iridescent yellow, uniformly coloured dark yellow. The differences in the protective action of the chromate films studied are explained on the basis of data on the compositions of the films and the changes in film thickness as well as corrosive treatment.

Dark and photoconductivity of nanocrystalline CdS films

Nanostructured CdS films are deposited by the high pressure magnetron sputtering technique onto glass and NaCl substrates at various substrate temperatures and at a fixed gas pressure. Electrical conductivity of these nano CdS films in dark and when illuminated is measured. It is observed that the conduction mechanism is dominated by the combined effects of thermionic emission, tunneling, and variable range hopping.

Cobalt and nickel complexes of 2,2′ : 6′,2″ : 6″,2‴-quaterpyridine as catalysts for electrochemical reduction of carbon dioxide

The complexes [Co(qtpy)(OH2)2][ClO4]2 and [Ni(qtpy)(MeCN)2][ClO4]2(qtpy = 2,2′ : 6′,2″ : 6′,2‴-quaterpyridine) were prepared by treating qtpy with Co(ClO4)2·6H2O and Ni(ClO4)·6H2O respectively in acetonitrile. In acetonitrile both complexes show one reversible couple assignable as the [M(qtpy)L2]2+/+ couple {E1/2 for [Co(qtpy)(OH2)2]2+/+=–0.67 V; [Ni(qtpy)(MeCN)2]2+/+=–0.79 V vs. saturated calomel electrode, SCE}, one quasi-reversible couple assignable as [M(qtpy)]+/0(E1/2=–0.96 for Co, –1.15 V for Ni) and one reduction wave at about –1.98 V vs. SCE assignable as reduction of [M(qtpy)] to [M(qtpy)]–. Constant-potential electrolysis of a 0.2–0.4 mmol dm–3 solution of [Co(qtpy)(OH2)2]2+ in the presence of CO2 at –1.7 V resulted in the production of CO with a current efficiency of about 80%. At bulk concentration of [Co(qtpy)(OH2)2]2+ 0.2 mmol dm–3, electrodeposition of the cobalt complex occurs at –1.65 V vs. SCE to give a dark brown electroactive film on the electrode surface. The cobalt-modified electrode is catalytically active towards the electrochemical reduction of carbon dioxide both in acetonitrile and in water. Constant-potential electrolysis with the cobalt-modified electrode at –1.7 V in acetonitrile and at –1.3 V in water resulted in the production of CO with current efficiencies of about 35%. No film formation on the electrode was observed for [Ni(qtpy)(MeCN)2]2+ and its catalytic activity towards reduction of CO2 is much less than that of the cobalt complex.

Enantioselective electropolymerization of aniline in the presence of (+)- or (−)-camphorsulfonate ion: a facile route to conducting polymers with preferred one-screw-sense helicity

The first and remarkably facile synthesis of optically active polyaniline has been achieved via the enantioselective electropolymerization of aniline on indium-tin-oxide-coated glass electrodes in aqueous solution containing (1S)-(+)- or (1R)-(−)-10-camphorsulfonic acid (HCSA). The dark green films of conducting polyemeraldine salt formed under electrostatic conditions (+ L1 V versus Ag/AgCl) exhibited strong circular dichroism (c.d.) spectra typical of polymers possessing helical chirality. The quantitative reversal of the c.d. spectrum of the salt grown in (+)-HCSA as opposed to (−)-HCSA suggests that electropolymerization is highly enantioselective, with one helical screw of the polymer chain being preferentially produced depending on the hand of the CSA − anion incorporated. The ready electrosynthesis of optically active polyanilines should facilitate studies of their use in asymmetric synthesis and in chiral chromatography.

Microstructural examination of solar-beam-irradiated TiN hard coatings

Microstructural examination and characterization of hard coatings may enable engineers to improve coating deposition processes and bring tribologists a step closer to the understanding of tribological mechanisms responsible for the failure of hard coatings. Since a thin oxide film on top of hard coatings could act as a solid lubricant and improve the wear and fretting behaviour of these coatings, the examination of such films is of special interest. The oxide films were produced on physical-vapour-deposited TiN coatings a few micrometres thick by irradiation with concentrated solar energy in ambient atmosphere at 800°C and for holding times between 10 and 350 s. For the analysis and characterization of the oxidized coating microstructure, micro-Raman spectroscopy and atomic force microscopy have been performed on oxidized surfaces. Light optical and scanning electron microscopy were done on polished low angle and fractured coating cross-sections, while transmission electron microscopy has been performed on thin foils showing the coatings either parallel or cross-sectional to the surface. The dark grey oxide films found on TiN have been identified as rutile TiO 2. These layers appeared with a uniform thickness but contain a non-uniform porosity over the oxide film thickness. Close to the TiN interface generally a higher porosity has been observed in the rutile. No sharp interface between TiN and rutile could be found. The TiN-rutile interface is characterized by oxide formation along the TiN grain boundaries.

Assault on society: satirical literature to film

Assault on Society explores over four decades of satirical and dark comedy films, a genre that has been examined only piecemeal before. Since many of these were adapted from novels and dramas, McCaffrey concentrates on literature transformed to the screen. Some works of the genre attack society's defects with the intent to change them, or at least to make us aware of them. If change seems impossible, the absurdist tone of the work has therapeutic value, as in the case of Dr. Strangelove, Catch-22, Day of the Locust, or A Clockwork Orange. Tom Jones and The Horse's Mouth feature picaresque protagonists and expose hypocrisy, blindness, and pretense. The legacy of dark humor and satire from the 60s and 70s lives on in the movies of the 80s and 90s.

Plasma polymerization of cyano compounds

AbstractPlasma polymerizations of three cyano compounds—acrylonitrile (AN), 1,2‐dicyanoethylene (FN), and tetracyanoethylene (TCE)—were investigated by FT IR and XPS, and the transforamtion of cyano groups during the plasma polymerization was discussed. The results pointed out an aspect of the preparation of plasma films with cyano groups. Plasma polymerizations of AN, FN, and TCE deposited brown or dark brown films that contained carbon, nitrogen, and oxygen. The elemental composition of the plasma films, especially N/C atomic ratio, showed a monomer dependence but no rf power dependence. The plasma films contained amide and amino groups, and ketene‐imine and conjugated — C = N — structures as well as cyano groups as nitrogen functionalities, and carbonyl and carboxyl groups as oxygen functionalities. For the preparation of plasma films with cyano groups, compounds with more than two cyano groups themselves are not suitable as monomers. The operation of plasma polymerization under mild plasma conditions at low rf power and in no oxygen atmosphere is favorable for the preparation of plasma films with cyano groups. © 1992 John Wiley &amp; Sons, Inc.

Digital subtraction radiography for assessment of simulated root resorption cavities. Performance of conventional and reverse contrast modes.

A previous study of the sensitivity and accuracy of a standardized radiographic technique for the disclosure of root cavities in a cadaver material indicated that it was not possible to perceive small artificial "resorption" cavities. Using the same material, the aim of the present study was to evaluate whether the use of subtraction radiography would improve the detection of root cavities. In an autopsy material of five mandibular blocks each containing two premolars, small, medium, and large cavities were drilled in the cervical, middle, and apical thirds of the proximal and oral root surfaces. Each jaw block was radiographed before (B) and after (A) cavity preparation with three different exposure times resulting in light, medium, and dark film densities. The radiographs were digitized. Digital subtraction was performed between the A- and B images of varying densities by a computer program developed for dental subtraction radiography. Conventional and reverse contrast modes of the subtraction image were assessed independently by four observers. The results showed small inter- and intraobserver differences in diagnostic accuracy for assessment of total number of root cavities. Original film density did not influence the diagnostic performance in the resulting subtraction image. Contrast mode in the subtraction image influenced diagnostic performance as the majority of observers did best with the reverse contrast mode (p < 0.05). Some of the small root cavities were disclosed by the subtraction technique, but overall accuracy was not increased compared to conventional radiography.