Study on Coating Mechanism and Properties of Die CrN+DLC Layer

This paper introduces the principle of PACVD coating technology, technical characteristics, equipment composition and material characteristics of CrN+DLC. Taking H13 steel as the research object, its surface was treated with CrN+DLC. The microstructure, bonding state and hardness of the interface were studied by means of metallography, SEM, hardness and component distribution of the surface layer. The anti-crack ability and grade of DLC layer were analyzed by studying the shape of crack distribution with Rockwell hardness indentation, and the high quality layer with crack grade of HF1 was obtained. With the dual properties of diamond and graphite of DLC, it can make the die surface have lower friction coefficient, higher hardness, higher impact toughness, better solid lubrication performance and higher corrosion resistance. Surface DLC coating technology provides a new solution to improve the performance of the die.

Influence of Combined Mechanical Processes on Tribological Properties of Tool Steels Vanadis 8 and Vancron 40 With a Similar Hardness

Surface integrity is important factor for components exposed to wear, like cold working tools, which need to possess high hardness combined with high wear resistance. Surface treatments such as grinding, hard turning, and hard turning with slide burnishing have been developed for its improvement. Vancron 40 and Vanadis 8 tool steels, of different chemical composition and different types and amounts of carbides, were now investigated. Heat treatment was carried out in vacuum furnaces with gas quenching to hardness of Vancron 64 ± 1 HRC and of Vanadis 65 ± 1 HRC. 3D topography, optical and scanning electron microscopy, X-ray diffraction and ball-on-disc tribological tests against Al2O3 and 100Cr6 balls as counterparts were used to examine wear and friction. For both steels, the lowest values of dynamic frictions and wear rates against Al2O3 counterbodies were achieved after sequential process of hard turning with slide burnishing with a burnishing force of 180 N. For alumina balls, the increase of wear resistance, achieved after hard turning plus burnishing in comparison to grinding exceeds 50 and 60%, respectively for Vanadis 8 and Vancron 40 steels.

The Corrosion Resistance of Hard Anodised EN AW 7075 T6 Alloy

In this paper, commercially cold-rolled and artificial aged EN AW 7075 T6 alloy has been used. To ensure increased corrosion resistance, surface hardness, scratching resistance, and aesthetic features, this aluminium alloy was subsequently hard anodised and hot-water sealed (AC-A). The hard anodizing and sealing process increased surface hardness up to 304±13 HV 1 from an initial surface hardness of 194±3 HV 1. Also, the microhardness of the anodised layer and bulk material has been documented. Scanning electron microscopy (SEM) was used for microstructure and trapped precipitates investigation in the 42.9±1.4 thick formed anodised layer investigation. The T6 treated (AC) and hard anodised together with sealed (AC-A) EN AW 7075 alloy corrosion properties were evaluated using the anodic potentiodynamic polarisation tests (PPT) in a neutral 2.5% NaCl deaerated solution. The corrosion rate CR (mm/y) decreased approx. 39-times for the hard anodised and sealed EN AW 7075 alloy (AC-A), associated with the shift of the Ecorr (mV) to more positive values, degreased Icorr (µA) and increased Rp (Ohm) values compared to the artificial aged (AC) alloy. Additionally, the pitting was evaluated using laser confocal microscopy, and the pitting coefficient was also calculated.

Impact of Compression Force on Mechanical, Textural, Release and Chewing Perception Properties of Compressible Medicated Chewing Gums

Medicated chewing gums (MCGs) represent a beneficial platform for realizing drugs intended for dental prophylaxis and treatment. The present study aimed to investigate the impact of compression force on the mechanical, textural, release, and chewing perception characteristics of compressible MCGs with the combination of lysozyme hydrochloride (LH) and ascorbic acid (AsA). Four batches of MCGs were obtained on a laboratory single-punch tablet machine applying different forces, i.e., 5, 7, 10, and 15 kN, and evaluated by their geometrical parameters, mechanical resistance, surface and internal structure characteristics, texture profile, release behavior, and perception attributes during mastication. It was found that increasing compression force slightly affected resistance to crushing and friability of MCGs, but resulted in surface smoothing and formation of a thicker layer with highly compacted particle arrangement. According to the texture analysis, increasing compression force led to harder and more adhesive gums, indicating possible difficulties in chewing and, therefore, impairment of their consumer properties. Lower compression forces were also found to be preferable in terms of better drug release from the obtained chewing gums. The volunteers’ assessment showed that an increase of compression force led to significantly raising the initial hardness and crumbliness as well as to decreasing the rate of the integral gum mass formation during mastication, which may negatively affect perceptive sensations when using MCGs. Based on the results obtained, the optimal compressing force was selected to be 7 kN, which allows obtaining MCGs with good organoleptic, mechanical, textural, and release properties.

The Influence of the Type of Electrolyte in the Modifying Solution on the Protective Properties of Vinyltrimethoysilane/Ethanol-Based Coatings Formed on Stainless Steel X20Cr13

The paper reports the results of the examination of the protective properties of silane coatings based on vinyltrimethoxysilane (VTMS) and ethanol (EtOH), doped with the following electrolytes: acetic acid (AcOH), lithium perchlorate LiClO4, sulphuric acid (VI) H2SO4 and ammonia NH3. The coatings were deposited on stainless steel X20Cr13 by the sol–gel dip-coating method. The obtained VTMS/EtOH/Electrolyte coatings were characterized in terms of corrosion resistance, surface morphology and adhesion to the steel substrate. Corrosion tests were conducted in sulphate media acidified up to pH = 2 with and without chloride ions Cl−, respectively. The effectiveness of corrosion protection was determined using potentiometric curves. It has been demonstrated that the coatings under study slow down the processes of corrosion of the steel substrate, thus effectively protecting it against corrosion.

The Construction of Regional Ecological Security Pattern Based on a Multi-Factor Comprehensive Model and Circuit Theory

Various ecological problems have become increasingly prominent due to the accelerated growth of urbanization. Ecological security and ecological conservation have become an important topics in the current scenario. This study took southern Anhui as an example, constructing comprehensive assessment models to conduct source identification from three perspectives, i.e. ecosystem services, ecological sensitivity and residents’ ecological needs. Landscape resistance surface was built based on the reciprocal of habitat quality and night-time light data. According to the circuit theory, the ecological process in the heterogeneous landscape was simulated to identify ecological corridors, extract pinch points and divide barriers that need improvement, thereby to construct the southern Anhui ecological security pattern (ESP). The pattern comprised 20 ecological sources, 37 ecological corridors, 9 pinch points and 2 levels of improvement areas. Specifically, ecological sources were mainly distributed within the area of Huangshan city and Xuancheng city, mostly covered with trees; ecological corridors were mostly located in the northern part of the research area; pinch points were mainly farmland or beside construction land; the primary improvement area was mainly in Chaohu city and Maanshan city, while the secondary improvement area was distributed around the primary area. The study discussed the diversified improvement strategies of different barriers and introduced the optimization scheme “one centre, two wings, one belt”, providing planning advice for decision-makers. The study expanded the construction of regional ESP, and partly guided the steady development of ESP of southern Anhui.

Climatic niche conservatism shapes the ecological assembly of Hawaiian arthropod communities

Spatial variation in climatic conditions along elevation gradients provides an important backdrop by which communities assemble and diversify. Lowland habitats tend to be connected through time, whereas highlands can be continuously or periodically isolated, conditions that have been hypothesized to promote high levels of species endemism. This tendency is expected to be accentuated among taxa that show niche conservatism within a given climatic envelope. While species distribution modeling approaches have allowed extensive exploration of niche conservatism among target taxa, a broad understanding of the phenomenon requires sampling of entire communities. Species-rich groups such as arthropods are ideal case studies for understanding ecological and biodiversity dynamics along elevational gradients given their important functional role in many ecosystems, but community-level studies have been limited due to their tremendous diversity. Here, we develop a novel semi-quantitative metabarcoding approach that combines specimen counts and size-sorting to characterize arthropod community-level diversity patterns along two elevational gradients across two volcanoes on the island of Hawai'i. We find that arthropod communities between the two transects become increasingly distinct compositionally at higher elevations. Resistance surface approaches suggest that climatic differences between sampling localities are an important driver in shaping beta-diversity patterns, though the relative importance of climate varies across taxonomic groups. Nevertheless, the climatic niche position of OTUs between transects was highly correlated, suggesting that climatic filters shape the colonization between adjacent volcanoes. Taken together, our results highlight climatic niche conservatism as an important factor shaping ecological assembly along elevational gradients and suggest topographic complexity as an important driver of diversification.

Omnidirectional connectivity for the Andean bear (Tremarctos ornatus) across the Colombian Andes

Context Conserving or restoring connectivity is a common objective of landscape-scale conservation initiatives. However, precise species occurrence or movement data to inform or validate spatial models are often lacking. Objectives Our objectives were to 1) produce the first approximation of country-wide connectivity for Andean bears ( Tremarctos ornatus ) in Colombia and 2) demonstrate a novel approach for model validation which uses publicly available web and social media records of a flagship species. Methods We used general knowledge about Andean bear habitat associations and indices of ecological integrity to construct a resistance surface across the Colombian Andes. We used this resistance surface to model omnidirectional connectivity using circuit theory. We validated our model with coarse location data acquired from local news stories and social media posts. Results Our model was most sensitive to changes in the resistance values of agricultural landcover and the mid-elevational zone, but uncertainty analysis demonstrated these had little impact on our conclusions regarding the municipalities most conducive to Andean bear movement. Just over one-third of those areas most conducive to Andean bear movement were within protected areas, while 8% coincided with agricultural landcover. Conclusions We constructed a model of connectivity that did not rely on independent, empirically derived location data. Our model is coarse (1 km resolution) but can still provide useful information to practitioners in Colombia who are working with scarce ecological data. More information about how Andean bears move through agricultural landscapes would help improve our understanding of connectivity for this species in Colombia.

Waterborne Graphene- and Nanocellulose-Based Inks for Functional Conductive Films and 3D Structures

In the vast field of conductive inks, graphene-based nanomaterials, including chemical derivatives such as graphene oxide as well as carbon nanotubes, offer important advantages as per their excellent physical properties. However, inks filled with carbon nanostructures are usually based on toxic and contaminating organic solvents or surfactants, posing serious health and environmental risks. Water is the most desirable medium for any envisioned application, thus, in this context, nanocellulose, an emerging nanomaterial, enables the dispersion of carbon nanomaterials in aqueous media within a sustainable and environmentally friendly scenario. In this work, we present the development of water-based inks made of a ternary system (graphene oxide, carbon nanotubes and nanocellulose) employing an autoclave method. Upon controlling the experimental variables, low-viscosity inks, high-viscosity pastes or self-standing hydrogels can be obtained in a tailored way. The resulting inks and pastes are further processed by spray- or rod-coating technologies into conductive films, and the hydrogels can be turned into aerogels by freeze-drying. The film properties, with respect to electrical surface resistance, surface morphology and robustness, present favorable opportunities as metal-free conductive layers in liquid-phase processed electronic device structures.