Alternate Exposure Research Articles

Distribution of moisture in reconstructed oil paintings on canvas during absorption and drying: A neutron radiography and NMR study

Moisture is a driving factor in the long-term mechanical deterioration of canvas paintings, as well as for a number of physico–chemical degradation processes. Since the 1990s a number of publications have addressed the equilibrium hygroscopic uptake and the hygro-mechanical deformation of linen canvas, oil paint, animal glue, and ground paint. In order to visualise and quantify the dynamic behaviour of these materials combined in a painting mock-up or reconstruction, we have performed custom-designed experiments with neutron radiography and nuclear magnetic resonance (NMR) imaging. This paper reports how both techniques were used to obtain spatially and temporally resolved information on moisture content, during alternate exposure to high and low relative humidity, or in contact with liquids of varying water activities. We observed how the canvas, which is the dominant component in terms of volumetric moisture uptake, absorbs and dries rapidly, and, due to its low vapour resistance, allows for vapour transfer towards the ground layer. Moisture desorption was generally found to be faster than absorption. The presence of sizing glue leads to a local increase of moisture content. It was observed that lining a painting with an extra canvas results in a damping effect: i.e. absorption and drying are significantly slowed down. The results obtained by NMR are complementary to neutron radiography in that they allow accurate monitoring of water ingress in contact with a liquid reservoir. Quantitative results are in good agreement with adsorption isotherms. The findings can be used for risk analysis of paintings exposed to changing micro-climates or subjected to conservation treatments using water. Future studies addressing moisture-driven deformation of paintings can make use of the proposed experimental techniques.

Sensitive naked-eye sensor for thiol-containing amino acids

Amino acids are of significant importance to the reversible redox reactions. As building blocks for protein, the thiol-containing amino acids levels, such as cysteine (Cys) and homocysteine (Hcy), have been directly linked to some diseases and cancers, such as Alzheimer's disease, neural tube defect and cardiovascular disease. The organic dyes or fluorophore molecules with a formyl group were sensitive to Cys or Hcy, which react with the Cys or Hcy to form a five or six-membered ring. Diarylethene 1-1-[2-methyl5-(9,9-n-Hexyl-fluoren-2-yl)-3-thienyl]-2-[(2-methyl-5-formyl)-3-thienyl] perfluorocy clopentene experienced reversible reaction when alternate exposure of UV and visible light in Figure 1, A. Upon the UV irradiation, the colorless solution in open-ring state changed to turquoise in closed-ring state within seconds. The absorption spectral changes of 1b accompanied with Cys/Hcy titration were recorded in DMF (20 μM), and the results were shown in Figure 1, B and Figure 1,C. When Cys were added into theDMF solution of 1b from 0 to 200 μM, the absorption spectrum of 1bwas changed remarkably (Figure 1, B). Upon addition of Cys, the absorbance at 635 nm of 1b significantly decreased with a new absorbance peak increase at 443 nm, corresponding to solution color change from turquoise to pale yellow so that it could be readily visualized bythe eye. However, the absorption spectrum of 1bwas changed differently when Hcy was added into the DMF solution. As shown in Figure 1,C, the absorbance at 635 nm of 1b decreases with the increase of Hcy concentration from 0 to 200 μM, and a broader absorption band emerged from 285 nm to 385 nm and 420 nm to 600 nm. Simultaneously, the color changed from turquoise to light brick-red. Therefore, compound 1 is a potential application in rapid and sensitive naked-eye sensor to detect Cys or Hcy, even the mixture of other kinds of amino acid.

Effects Of Radon And Uv Exposure On Skin Cancer Mortality In Switzerland

Background: Melanoma and non-melanoma skin cancer are among the most common types of cancer in Switzerland. Risk factors include exposure to ultraviolet (UV) radiation. Recently, radon attached on particles deposited on the skin has been suggested as an additional risk factor. Exposure gradients in Switzerland are considerable due to large differences in altitude (UV increases with altitude) and in geology and soil type (with varying radon levels). We aimed to investigate the mutual effects of UV and radon exposure on skin cancer mortality. Methods: The association between UV and radon exposure on skin cancer mortality (IDC10: C43-44) was investigated by Cox regression, with age as the underlying time scale and adjusted for confounders. We defined the starting at-risk population as adults aged 30+ from 01 Jan 2000, and applied right censoring at the age of event (death by skin cancer), emigration, or end of follow-up (31 Dec 2008). Exposure was modelled at address-level, representative of the period 2000-2008. Radon exposure was based on a national exposure prediction model developed and validated with the measurements from the Swiss Radon Database. Long-term UV exposure was modelled by linear regression using measurements of daily maximum UV index at 4 Swiss locations, 10x10km monthly global radiation grids and a 25x25m digital terrain model. Preliminary Results: The study population included 4.3 million adults and ~2300 deaths with skin cancer as the definitive primary cause. There was no correlation between the radon and long-term UV exposure (r = -0.01). Controlling for the alternate exposure, age-sex adjusted hazard ratios were 1.24 (95% CI: 1.10-1.39) per 100 Bq/m3 for radon and 1.08 (0.93-1.27) per increment in the UV index. Conclusions: A better understanding of the role of the UV radiation and radon exposure for skin cancer is of high public health relevance. Our study suggests that both radon and UV are risk factors for skin cancer.

Apparent self-accelerating alternating assembly of semiconductor nanoparticles and polymers

Alternating polyelectrolyte deposition is a promising route to the low-cost fabrication of electroluminescent devices based on semiconductor nanoparticles, but optimization and exploitation demand a deeper understanding of the fabrication mechanism, which has not hitherto been scrutinized in detail. Nanoparticle–polymer composites were assembled by repeated alternate exposures of a substrate to polyanionic thioglycolate-coated CdTe nanoparticles and the organic polycation polydiallyldimethylammonium while monitoring the process kinetics in situ using optical waveguide lightmode spectroscopy, which enabled detailed structural information to be obtained with good time resolution. This complements the previously reported device characterization. Two hitherto unnoticed features were observed: (i) apparently spontaneous acceleration of addition of semiconductor nanoparticles after a certain quantity has already been deposited and (ii) during subsequent exposure to the organic polycation, an appreciable proportion of the immediately previously deposited nanoparticles is removed. Analysis of the evolution of the optogeometrical parameters of the assembly revealed that during the initial slow addition the nanoparticles enter nanopores in the immediately previously deposited polymer. The deposition régime then switches abruptly to the formation of an adlayer of the nanoparticles. These are initially deposited in considerable excess, which is removable by simple dilution of the system. Further nanoparticle removal takes place during the following phase of polycation deposition via a process of particle scavenging by the polycation molecules. Changes in film refractive index during these various processes show that the predominantly columnar (rather than laminar) molecular arrangement established for polyelectrolyte-only films is maintained in the hybrid polymer–particle films, although the filling of the polyelectrolyte pores makes the film more isotropic.

Intergranular Corrosion in Sensitized AA5083 Under Alternating Wet and Dry Conditions

AA5XXX aluminum-magnesium alloys have become a popular choice for high performance marine structures, especially for the US Navy. The combination of their high strength-to-weight ratio, uniform corrosion resistance, and low cost make these alloys well-suited for shipbuilding. Despite their excellent resistance to uniform corrosion, these alloys can become susceptible to intergranular corrosion (IGC) due to sensitization or precipitation of the more anodic β-phase (Al3Mg2) along the grain boundaries after long periods of exposures to service temperatures of as low as 50oC.[1-2] A significant amount of research has been conducted on the behavior of AA5083 in the context of full immersion exposure in marine environment.[3-6] IGC propagation depths were found to be influenced by the exposure time, applied potential, degree of sensitization (DoS), and orientation of propagation. These studies also revealed that an incubation period is necessary for β-phase pitting to develop into IGC in chloride-containing solutions under potentiostatic conditions. Although during service some areas of these marine structures will be constantly submerged, other parts will only be exposed to atmospheric exposure, and certain surfaces will be subjected to alternating conditions of wetting and drying. This study examines the IGC behavior of AA5083 under various alternating exposure conditions. Specifically, whether these alternating exposures may accelerate or impede IGC propagation in comparison with continuous full immersion was investigated. Because environmental conditions such as relative humidity, film thickness, and electrolyte concentration influence atmospheric corrosion, it is imperative to define a dry cycle environment. Preliminary tests involved a series of 4 sets of alternating wet and dry cycles on AA5083-H131 specimens sensitized to 50 mg/cm2. Every wet or dry cycle lasted for 25 h, for a cumulative wet or full immersion of 100 h. During each wet cycle, the specimens were potentiostatically held at -0.73 VSCE in 0.6 M NaCl solution, pH 8.3. The specimens were each subjected to a different dry cycle environment: (a) no electrolyte in 10% RH, (b) no electrolyte in 90% RH, and (c) fresh 0.6 M NaCl solution at open circuit potential. As compared to that continuously exposed to -0.73 VSCEfor 100 h, the IGC depths after the cumulative alternate immersion exposures, in Figure 1, are substantially lower, which could be due incubation at the beginning of each wet cycle. Additionally, these results also implied that during dry cycle, IGC can still propagate given the appropriate RH levels and/or electrolyte conditions. To avoid damage contributions from these factors, the 10% RH was chosen as the most conservative dry cycle environment. In order to study the influence of cycle time on the IGC damage depths, additional experiments involving various resident times in wet and dry environment were conducted. For each test, the resident time was equal for every wet and dry cycle. For all the tests, the total cumulative wet or full immersion time was 100 h. Initial results, in Figure 2, show that the shorter cycles achieved lower steady state current densities that decreased with each cycle. Moreover, an incubation time to reach a steady state current density was observed at each cycle. To probe the time to reach steady state current density, experiments with dry cycles as short as 30 min in between 25-h wet cycles were conducted. IGC depths were characterized at the end by using suitable metallographic techniques, and image analyses to track effects of cycle time and incubation on the physical damages. The results of this study provide insights into the importance of alternating wet and dry cycles on the IGC propagation of sensitized Al-Mg alloys. The study is part of a larger effort to understand IGC and IGSCC damage in AA5XXX series applied in marine environments. Acknowledgements Office of Naval Research under the contract ONR: N00014-08-10315 References [1] G.M. Scamans, N.J.H. Holroyd, C.D.S. Tuck, Corros. Sci., 27 (1987) 329-347. [2] R.H Jones, D.R. Baer, M.J. Danielson, J.S. Vetrano, Metall. Mater. Trans A, 32 (2001) 1699-1711 [3] S. Jain, M.L.C. Lim, J.L. Hudson, J.R. Scully, Corros. Sci., 59 (2012) 136-147. [4] M.L.C. Lim, J.R.Scully, R.G. Kelly, Corrosion, 69 (2013) 35-47. [5] M.L.C. Lim, R.G. Kelly, J.R. Scully, “Critical Electrochemical Conditions for Intergranular Corrosion in Sensitized AA5083-H131”, in NACE Department of Defense Virtual Corrosion Conference 2013. [6] Y. Yuan, “Localized Corrosion and Stress Corrosion Cracking of Aluminum-Magnesium Alloys” (Ph.D. diss., University of Birmingham: Birmingham, U.K., 2005) Figure 1

Effects of combustion and salt-fog exposure on fatigue behavior of two ceramic matrix composites and a superalloy

Tension–tension fatigue behavior of two ceramic matrix composites (CMCs), SiC/SiC (Nicalon™/SiC) & oxide/oxide (Nextel™720/AS), and a superalloy (Rene 41) was characterized under combustion environment as well as under alternate salt-fog exposure for 4 h and combustion fatigue for 6 h. The run-out limit was 25 h (90,000 cycles) of fatigue. Test temperatures were 900, 1050, and 1050 °C for Rene 41, SiC/SiC, and oxide/oxide CMCs, respectively, and the applied maximum fatigue stress was 62 MPa. All three materials survived up to 25 h under combustion fatigue without any exposure to salt. Rene 41 and Nicalon™/SiC survived up to 25 h (90,000 cycles) under the alternate exposure of salt-fog and combustion fatigue. However, exposure to salt-fog exposure (5 wt%) had very detrimental effect on the combustion fatigue resistance of Nextel™720/AS. The reduction in salt concentration to 0.5 wt% had less detrimental effect. These tests were supplemented with more tests, where applied stress level, test temperature, and salt concentration were changed. Out of these three gas turbine engine materials, Nicalon™/SiC exhibited better fatigue performance in terms of applied temperature and stress level under combustion condition as well as when exposed to alternate salt-fog and combustion.

Heavy metal enrichment in the riparian sediments and soils of the Three Gorges Reservoir, China

Abstract. The Three Gorges Reservoir encompasses a riparian zone with a vertical height of 30 m and a total area of 349 km2 that has been subjected to alternate inundation and exposure due to regular impoundment. Sedimentation on the riparian landforms constitutes an important pathway for riverine contaminant redistribution. In an attempt to understand heavy metal enrichment since water inundation, riparian sediments and soils were sampled along five transects in a typical riparian zone composed of cultivated bench terraces in the middle reaches. Heavy metals (Cr, Ni, Cu, Zn, As, Cd and Pb) were determined to characterize the lateral distribution and vertical transfer ratio. The results indicated that all heavy metals were enriched to varying extents both in the riparian sediments and soils, compared with regional background contents in soils and the reference levels in sediments. However, heavy metal levels in the riparian sediments were generally higher than those in the riparian soils, while those in the upper riparian soils (0–5 cm) were overall slightly higher than those in the lower riparian soils (5–10 cm). There was a decreasing trend of heavy metal contents with increasing elevation. The elevated levels of heavy metals in the riparian sediments may be attributed to sediment yields from upstream anthropogenic sources, especially during major rainstorms in the wet season when large loads of contaminated sediment may be produced from diffuse source areas. Heavy metals can also be adsorbed to pure sediment in the course of mobilization or after deposition. Considering that the riparian soils are local weathering products without mobilization, the enrichment of heavy metals may principally be ascribed to chemical adsorption from dissolved fractions or vertical transfer from overlaid sediments. Heavy metal enrichment may further be affected by the specific type of hydrologic regime such that relatively long flooding duration caused by water impoundment and natural floods was responsible for the relatively higher levels of heavy metals in the lower portions of the riparian zone.

Performance regeneration in lanthanum strontium manganite cathode during exposure to H<sub>2</sub>O and CO<sub>2</sub> containing ambient air atmospheres

The regenerability and stability of lanthanum strontium manganite (LSM)/yttria doped zirconia (YSZ)/LSM symmetrical cells have been examined after the cells were exposed to real-world air environment containing H2O and CO2. An alternate exposure experiment in 20% H2O-air and dry air has been conducted to test the reversibility of the cell degradation in H2O/air. Long-term experiment in 3% H2O-0.5% CO2-air, dry air, 0.5% CO2-air, and 10% CO2-air has shown the stability and regenerability of the cell performance. Additional experiments show that periodic water content fluctuation causes the cell performance fluctuation. Electrochemical performance measurements and post-test microstructure analysis indicate that the segregation of SrO on the LSM surface and formation of La2Zr2O7 at the LSM/YSZ interface degraded the electrochemical performance by increasing the polarization resistance. The cell performance degradation can be partially recovered by exposure to dry air. Thermogravimetric analysis (TGA) has been conducted for the LSM as well as its constituent oxides to elucidate degradation mechanisms. Mechanisms related to the performance degradation and regenerability have been proposed.

Control of a two-dimensional electron gas on SrTiO₃(111) by atomic oxygen.

We report on the formation of a two-dimensional electron gas (2DEG) at the bare surface of (111) oriented SrTiO3. Angle resolved photoemission experiments reveal highly itinerant carriers with a sixfold symmetric Fermi surface and strongly anisotropic effective masses. The electronic structure of the 2DEG is in good agreement with self-consistent tight-binding supercell calculations that incorporate a confinement potential due to surface band bending. We further demonstrate that alternate exposure of the surface to ultraviolet light and atomic oxygen allows tuning of the carrier density and the complete suppression of the 2DEG.

A chiroptical switch based on DNA/layered double hydroxide ultrathin films.

A highly oriented film was fabricated by layer-by-layer self-assembly of DNA and MgAl-layered double hydroxide nanosheets, and its application in chiroptical switch was demonstrated via intercalation and deintercalation of an achiral molecule into the DNA cavity. DNA molecules are prone to forming an ordered and dispersive state in the interlayer region of rigid layered double hydroxide (LDH) nanosheets as confirmed by scanning electron microscopy and atomic force microscopy. The induced chiroptical ultrathin film (UTF) is achieved via the intercalation of an achiral chromophore [5,10,15,20-tetrakis(4-N-methylpyridyl)porphine tetra(p-toluenesulfonate) (TMPyP)] into the spiral cavity of DNA stabilized in the LDH matrix [denoted as TMPyP-(DNA/LDH)20]. Fluorescence and circular dichroism spectroscopy are utilized to testify the intercalation of TMPyP into (DNA/LDH)20 UTF that involves two steps: the electrostatic binding of TMPyP onto the surface of (DNA/LDH)20 followed by intercalation into base pairs of DNA. In addition, the TMPyP-(DNA/LDH)20 UTF exhibits good reversibility and repeatability in induced optical chirality, based on the intercalation and deintercalation of TMPyP by alternate exposure to HCl and NH3/H2O vapor, which can be potentially used as a chiroptical switch in data storage.

Laboratory studies of H retention and LiH formation in liquid lithium

Laboratory experiments on H/D retention on liquid lithium followed by thermal desorption spectrometry (TDS) have been performed at Ciemat. Two different experimental set ups were used in order to expose liquid Li to hydrogen gas or to hydrogen glow discharge plasmas at temperatures up to 673K. In the present work the results concerning the gas phase absorption are addressed. Two different kinetics of absorption were identified from the time evolution of the uptake. Alternate exposures to H2 and D2 were carried out in order to study the isotope exchange and its possible use for tritium retention control in Fusion Reactor. Although important differences were found in the absorption kinetics of both species, the total retention seems to be governed by the total sum of hydrogenic isotopes, and only small differences were found in the corresponding TDS spectra, on which evidence of some isotope exchange is observed. The results are discussed in relation to the potential use of liquid lithium walls in a Fusion Reactor.

Emerging Strategies and Applications of Layer-by-Layer Self-Assembly.

Layer-by-layer self-assembly is an approach to develop an ultrathin film on solid support by alternate exposure to positive and negative species with spontaneous deposition of the oppositely charged ions. This paper summarizes various approaches used for fabrication of layer-by-layer self-assembly as well as their utility to produce various devices. The layer-by-layer technique is basically used for formation of multilayer films. A variety of nanomaterials use it for the modification of films to enhance their resultant durability as well as strength. Studies have shown that many different types of materials can be used for fabrication of multilayers. Recently the layer-by-layer self-assembly technique has also been used for fabrication of gas sensors, hydrogen sensors and solar-based cells. Various methods, such as spin deposition, calcinations, and dry-transfer printing are being used for fabrication of thin films. In this review, the author summarizes the various interesting properties as well as fabrication strategies of layer-by-layer self-assembly.

Data processing costs for three posture assessment methods

BackgroundData processing contributes a non-trivial proportion to total research costs, but documentation of these costs is rare. This paper employed a priori cost tracking for three posture assessment methods (self-report, observation of video, and inclinometry), developed a model describing the fixed and variable cost components, and simulated additional study scenarios to demonstrate the utility of the model.MethodsTrunk and shoulder postures of aircraft baggage handlers were assessed for 80 working days using all three methods. A model was developed to estimate data processing phase costs, including fixed and variable components related to study planning and administration, custom software development, training of analysts, and processing time.ResultsObservation of video was the most costly data processing method with total cost of € 30,630, and was 1.2-fold more costly than inclinometry (€ 26,255), and 2.5-fold more costly than self-reported data (€ 12,491). Simulated scenarios showed altering design strategy could substantially impact processing costs. This was shown for both fixed parameters, such as software development and training costs, and variable parameters, such as the number of work-shift files processed, as well as the sampling frequency for video observation. When data collection and data processing costs were combined, the cost difference between video and inclinometer methods was reduced to 7%; simulated data showed this difference could be diminished and, even, reversed at larger study sample sizes. Self-report remained substantially less costly under all design strategies, but produced alternate exposure metrics.ConclusionsThese findings build on the previously published data collection phase cost model by reporting costs for post-collection data processing of the same data set. Together, these models permit empirically based study planning and identification of cost-efficient study designs.

Phanta: A Non-Fluorescent Photochromic Acceptor for pcFRET

We have developed an orange non-fluorescent photochromic protein (quantum yield, 0.003) we call Phanta that is useful as an acceptor in pcFRET applications. Phanta can be repeatedly inter-converted between the two absorbing states by alternate exposure to cyan and violet light. The absorption spectra of Phanta in one absorbing state shows excellent overlap with the emission spectra of a number of donor green fluorescent proteins including the commonly used EGFP. We show that the Phanta-EGFP FRET pair is suitable for monitoring the activation of caspase 3 in live cells using readily available instrumentation and a simple protocol that requires the acquisition of two donor emission images corresponding to Phanta in each of its photoswitched states. This the first report of a genetically encoded non-fluorescent acceptor for pcFRET.

Evaluation of Alternate Category Structures for the Strain Index

The purpose of this study was to develop alternative Strain Index risk classification categories. Strain Index scores are usually categorized into four Strain Index "risk categories." The "original" risk categories were developed in the meat-packing industry and may not be fully applicable to other industries. Daily Strain Index scores were estimated among 276 manufacturing workers participating in a cohort study of occupational risk factors for hand-arm musculoskeletal symptoms. Each score was categorized using the original method and a new method based on quartiles of Strain Index score values among symptomatic participants. Models examining associations between original Strain Index risk categories and incident hand-arm symptoms were compared to models examining associations between the alternative Strain Index risk categories and incident hand-arm symptoms. Compared to the respective referent categories, a twofold or greater increase in the risk of incident hand-arm symptoms was observed for the highest original Strain Index risk category (HR = 2.06, 95% CI = [1.08-3.92]) and for the second highest alternate Strain Index risk exposure category (HR = 2.21, 95% CI = [1.26-3.85]). Although significant associations between Strain Index risk category and incident hand-arm symptoms were observed for both Strain Index categorization methods, model fit statistics favored the alternate approach. Results from this study suggests that the Strain Index risk category structure may need to be tailored to specific populations. If verified, results from this study provide a better way to identify hazardous manufacturing jobs and target them for exposure reduction.

Photoswitchable Metal-Mediated Catalysis: Remotely Tuned Alkene and Alkyne Hydroborations

A photochromic dithienylethene-annulated N-heterocyclic carbene (NHC)–Rh(I) complex was synthesized and found to undergo reversible electrocyclic ring closure upon alternate exposure to UV (λirr 313 nm) and visible (λirr >500 nm) radiation. Under ambient light, the Rh catalyst efficiently promoted the hydroboration of alkenes and alkynes with pinacolborane. However, upon UV irradiation to effect a photocyclization within the NHC ligand, the catalytic activity was reduced by up to an order of magnitude. The disparity in the rates was used to photoswitch the rates of a series of hydroboration reactions, thus demonstrating the first examples of photomodulating a transition-metal catalyst by tuning its electronic properties. The rate attenuation observed under UV irradiation was attributed to inhibition of the rate-determining reductive elimination step arising from a decrease in electron-donating ability of the photocyclized NHC ligated to the Rh center.

Electronic structure of undoped and doped SnOx nanolayers

Results of electronic structure investigations for tin oxide nanolayers obtained by tin magnetron sputtering and their following oxidation in air at different temperatures are presented. Using X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) spectroscopy techniques it was shown that at the 240°С anneal a predominant phase in the sample surface layers is tin monoxide. With the annealing temperature increase up to 450°C the phase composition corresponds to tin dioxide. Rather high sorption sensitivity for the samples oxidized at 450°C was found. The compositional model of the gap structure based on XANES and XPS data matching for SnOx nanolayers revealed occurrence of the crossed transitions with the energy of ~3.7eV in the presence of two phases: the SnO and the SnO2 or SnOx with vacancies. Under surface doping of SnO2 nanolayers with palladium PdO and PdO2 is observed where PdO is the most intensive component. O2 and H2 multiple alternate exposures resulted in the disappearance of palladium dioxide and PdO recovery to the metallic Pd. Under Pd bulk doping of nanolayers PdO and PdO2 were observed in the surface layers. In this case PdO2 was presented by two types of particles different in size, one of them having the greatest binding energy of Pd 3d5/2 (339.0eV).

A New Concept for Spatially-Divided Reactive Ion Etching with ALD-Based Passivation

Conventional Deep Reactive Ion Etching (DRIE) is a plasma etch process with alternating half-cycles of 1) Si-etching with SF6 to form gaseous SiFx etch products, and 2) passivation with C4F8 polymerizing as a protecting fluorocarbon deposit on the sidewalls and bottom of the etched features. We report on a novel alternative and disruptive technology concept of Spatially-divided Deep Reactive Ion Etching, where the process is converted from the time-divided into the spatially divided regime. The spatial division can be accomplished by ~20 to 100 μm high inert gas-bearing ‘curtains’ that confine the reactive gases to individual (often linear) injection slots constructed in a gas injector head. By horizontally moving the substrate back and forth under the head one can realize the alternate exposures to compose the overall cycle.Next improvement in the spatially-divided approach is the replacement of the CVD-based C4F8 passivation steps by ALD-based oxide (e.g. SiO2) deposition cycles. The method can have industrial potential in cost-effective creation of advanced 3D TSV interconnects and MEMS, but also in advanced patterning of, e.g., nanoscale FinFET devices with reduced line edge roughness, thus approaching Atomic Layer Etching accuracy.

A new concept for spatially divided Deep Reactive Ion Etching with ALD-based passivation

Conventional Deep Reactive Ion Etching (DRIE) is a plasma etch process with alternating half-cycles of 1) Si-etching with SF6 to form gaseous SiFx etch products, and 2) passivation with C4F8 that polymerizes as a protecting fluorocarbon deposit on the sidewalls and bottom of the etched features. In this work we report on a novel alternative and disruptive technology concept of Spatially-divided Deep Reactive Ion Etching, S-DRIE, where the process is converted from the time-divided into the spatially divided regime. The spatial division can be accomplished by inert gas bearing 'curtains' of heights down to ∼20 μm. These curtains confine the reactive gases to individual (often linear) injection slots constructed in a gas injector head. By horizontally moving the substrate back and forth under the head one can realize the alternate exposures to the overall cycle.A second improvement in the spatially divided approach is the replacement of the CVD-based C4F8 passivation steps by ALD-based oxide (e.g. SiO2) deposition cycles. The method can have industrial potential in cost-effective creation of advanced 3D interconnects (TSVs), MEMS manufacturing and advanced patterning, e.g., in nanoscale transistor line edge roughness using Atomic Layer Etching.

Aluminosilicate coatings with enhanced heat- and corrosion resistance

This paper summarizes the results of development of heat- and acid resistant mineral coatings intended for protection of concrete structures and brickwork from exposure of acid media and elevated temperatures. The protective coatings are produced basing on the alkaline aluminosilicate bonds, in which the alkaline compounds are strongly bound into water insoluble hydroaluminosilicate complexes. On the contrary to the known-in-the-art mineral coatings based on cements containing slag and slag/ash, the coatings based on the alkaline aluminosilicates advantageously explore a correlation between corrosion resistance and phase composition due to the synthesis in the structure of the alkaline aluminosilicate matrix of high-silica zeolite-like phases (faujasite, chabazite and mordenite). The introduction into the alkaline aluminosilicate matrix of the formula Na2O·Al2O3·6SiO2·14.5H2O of the acid resistant fillers, selected from mica, aluminosilicate microspheres and ground quartz sand taken in quantities of 3, 8 and 12wt.% enabled to increase the acid resistance of the coatings by 1.25–1.5 fold compared to the known-in-the-art mineral analogs. Heat resistance of the coatings under study, in the conditions of alternate exposure of temperature (473K) and vapors of oleum, may reach 100cycles. The developed formulations of the anti-corrosion alkaline aluminosilicate coatings were successfully tried in 2007 in industrial conditions in repairing the deteriorated brickwork of the flue. After 5years no sign of deterioration of the protective coating was reported.