Refractory coatings and method of producing the same

The adhesion, friction, and wear properties of sputtered refractory coatings on substrates of materials that form stable nitrides is improved by placing each substrate directly below a titanium carbide target of a commercial radiofrequency diode apparatus in a vacuum chamber. Nitrogen is bled into the system through a nozzle resulting in a small partial pressure of about 0.5% to 2.5% during the first two minutes of deposition. The flow of nitrogen is then stopped, and the sputtering ambient is reduced to pure argon through a nozzle without interrupting the sputtering process. When nitrogen is deliberately introduced during the crucial interface formation, some of the titanium at the interface reacts to form titanium nitride while the metal of the substrate also forms the nitride. These two nitrides atomically mixed together in the interfacial region act to more strongly bond the growing titanium carbide coating as it forms on the substrate

Improved adherence of sputtered titanium carbide coatings on nickel- and titanium-base alloys

Rene 41 and Ti-6Al-4V alloys were radio frequency sputter coated with titanium carbide by several techniques in order to determine the most effective. Coatings were evaluated in pin-on-disk tests. Surface analysis by X-ray photoelectron spectroscopy was used to relate adherence to interfacial chemistry. For Rene 41, good coating adherence was obtained when a small amount of acetylene was added to the sputtering plasma. The acetylene carburized the alloy surface and resulted in better bonding to the TiC coating. For Ti-6Al-4V, the best adherence and wear protection was obtained when a pure titanium interlayer was used between the coating and the alloy. The interlayer is thought to prevent the formation of a brittle, fracture-prone, aluminum oxide layer

Adherence of sputtered titanium carbides

Sputtered coatings of the refractory metal carbides are of great interest for applications where hard wear-resistant materials are desired. The usefulness of sputtered refractory carbides is often limited, in practice, by spalling or interfacial separation. In this work improvements in the adherence of refractory carbides on iron, nickel and titanium based alloys were obtained by using oxidation, reactive sputtering or sputtered interlayers to alter the coating-substrate interfacial region. X-ray photoelectron spectroscopy and argon ion etching were used to characterize the interfacial regions, and an attempt was made to correlate adherence as measured in wear tests with the chemical nature of the interface

X-ray photoelectron spectroscopy study of radiofrequency-sputtered refractory compound steel interfaces

Radiofrequency sputtering was used to deposit Mo2C, Mo2B5, and MoSi2 coatings on 440C steel substrates. Both sputter etched and preoxidized substrates were used, and the films were deposited with and without a substrate bias of -300 V. The composition of the coatings was measured as a function of depth by X-ray photoelectron spectroscopy combined with argon ion etching. In the interfacial region there was evidence that bias produced a graded interface in Mo2B5 but not in Mo2C. Oxides of iron and of all film constituents except carbon were presented in all cases but the iron oxide concentration was higher and the layer thicker on the preoxidized substrates. The film and iron oxides were mixed in the MoSi2 and Mo2C films but layered in the Mo2B5 film. The presence of mixed oxides correlates with enhanced film adhesion

Effect of nitrogen-containing plasma on adherence, friction, and wear of radiofrequency-sputtered titanium carbide coatings

Friction and wear experiments on 440C steel surfaces that were rf sputtered with titanium carbide when a small percentage of nitrogen was added to the plasma were conducted. Both X-ray photoelectron spectroscopy and X-ray diffraction were used to analyze the resultant coatings. Results indicate that the small partial pressure of nitrogen (approximately 0.5 percent) markedly improves the adherence, friction, and wear properties when compared with coatings applied to sputter-etched surfaces, oxidized surfaces, or in the presence of a small oxygen partial pressure. The improvements are related to the formation of an interface containing a mixture of the nitrides of titanium and iron, which are harder than their corresponding oxides

X-ray photoelectron spectroscopy study of radiofrequency sputtered chromium bromide, molybdenum disilicide, and molybdenum disulfide coatings and their friction properties

Radiofrequency sputtered coatings of CRB2, MOSI2, and MOS2 were examined by X-ray photoelectron spectroscopy. The effects of sputtering target history, deposition time, RF power level, and substrate bias on film composition were studied. Friction tests were run on RF sputtered surfaces of 440-C steel to correlate XPS data with lubricating properties. Significant deviations from stoichiometry and high oxide levels for all three compounds were related to target outgassing. The effect of biasing on these two factors depended on the compound. Improved stoichiometry correlated well with good friction and wear properties

An agent-based model about the effects of fake news on a norovirus outbreak

Concern about health misinformation is longstanding, especially on the Internet. Using agent-based models, we considered the effects of such misinformation on a norovirus outbreak, and some methods for countering the possible impacts of ‘good’ and ‘bad’ health advice. The work explicitly models spread of physical disease and information (both online and offline) as two separate but interacting processes. The models have multiple stochastic elements; repeat model runs were made to identify parameter values that most consistently produced the desired target baseline scenario. Next, parameters were found that most consistently led to a scenario when outbreak severity was clearly made worse by circulating poor quality disease prevention advice. Strategies to counter ‘fake’ health news were tested. A 10% reduction in circulating bad advice or making at least 20% of people fully resistant to believing in and sharing bad health advice were effective thresholds to counteract the negative impacts of bad advice during a norovirus outbreak. How feasible it is to achieve these targets within communication networks (online and offline) should be explored

Influence of base and photoacid generator on deprotection blur in extreme ultraviolet photoresists and some thoughts on shot noise

A contact-hole deprotection blur metric has been used to monitor the deprotection blur of an experimental open platform resist (EH27) as the wt % of base and photoacid generator (PAG) were varied. A six times increase in base wt % is shown to reduce the size of successfully patterned 1:1 line-space features from 52 to 39 nm without changing deprotection blur. Corresponding isolated line edge roughness is reduced from 6.9 to 4.1 nm. A two times increase in PAG wt % is shown to improve 1:1 line-space patterning from 47 to 40 nm without changing deprotection blur or isolated line edge roughness. A discussion of improved patterning performance as related to shot noise and deprotection blur concludes with a speculation that the spatial distribution of PAG molecules has been playing some role, perhaps a dominant one, in determining the uniformity of photogenerated acids in the resists that have been studied. © 2008 American Vacuum Society

The spectral transmission of ocular media suggests ultraviolet sensitivity is widespread among mammals

Although ultraviolet (UV) sensitivity is widespread among animals it is considered rare in mammals, being restricted to the few species that have a visual pigment maximally sensitive (λmax) below 400 nm. However, even animals without such a pigment will be UV-sensitive if they have ocular media that transmit these wavelengths, as all visual pigments absorb significant amounts of UV if the energy level is sufficient. Although it is known that lenses of diurnal sciurid rodents, tree shrews and primates prevent UV from reaching the retina, the degree of UV transmission by ocular media of most other mammals without a visual pigment with λmax in the UV is unknown. We examined lenses of 38 mammalian species from 25 families in nine orders and observed large diversity in the degree of short-wavelength transmission. All species whose lenses removed short wavelengths had retinae specialized for high spatial resolution and relatively high cone numbers, suggesting that UV removal is primarily linked to increased acuity. Other mammals, however, such as hedgehogs, dogs, cats, ferrets and okapis had lenses transmitting significant amounts of UVA (315–400 nm), suggesting that they will be UV-sensitive even without a specific UV visual pigment

Risk factors and risk factor cascades for communicable disease outbreaks in complex humanitarian emergencies: A qualitative systematic review

Background: Communicable diseases are a major concern during complex humanitarian emergencies. Descriptions of risk factors for infectious disease outbreaks are often non-specific and yet not easily generalizable to similar situations. This review attempts to capture relevant evidence and explore whether it is possible to better generalize the role of risk factors and the risk factor cascades these factors may form. Methods: A systematic search of the key databases and websites was conducted. Search terms included terms for complex humanitarian emergencies (per United Nations Office for the Coordination of Humanitarian Affairs definition) and terms for communicable diseases. Due to the types of evidence found, a thematic synthesis was conducted. Results: 26 articles met inclusion criteria. Key contextual risk factors include crowded conditions, forced displacement, poor quality shelter, poor water, sanitation and hygiene conditions, lack of health care facilities and lack of adequate surveillance. Most identified risk factors do not relate to specific diseases, or are specific to a group of diseases such as diarrheal diseases and not to a particular disease within that group. Risk factors are often listed in general terms but are poorly evidenced, not contextualized and not considered with respect to interaction effects in individual publications. The high level of the interrelatedness of risk factors became evident, demonstrating risk factor cascades that are triggered by individual risk factors or clusters of risk factors. Conclusions: Complex humanitarian emergencies pose a significant threat to public health. More rigorous research on the risk of communicable disease outbreaks in complex humanitarian emergencies is needed, both from a practitioner and from an academic point of view