Reducing friction, wear and lubricants are the main developing tendency in the modern manufacturing technology. In this work, we used an integrated approach to reduce the friction and wear of hard ...TiAlSiN coatings. Firstly, dimples were introduced to substrate surface by a Nd:YAG laser. Secondly, TiAlSiN coatings were prepared on the textured surfaces by magnetron sputtering technique. Finally, high energy ion implantation was performed on the textured coating surface. In this manner, adherent ion mixing layer can be present on the textured coating surface. The hard coating supports the load while the ion mixing layer provides low friction coefficient. The samples were characterized by different techniques such as Raman spectroscopy, X-ray diffraction, energy dispersive spectrometry and nanoindentation measurement etc. Additionally, wear performance was characterized by a ball-on-disk wear tester in dry condition. The results showed that the structural and mechanical properties of the TiAlSiN coatings could be altered by ion implantation process. Surface softening was found for the coatings implanted with carbon. In addition, the TiAlSiN coatings with surface texturing and ion implantation had an obvious improvement on friction and wear as compared to un-treated coated surfaces. The improved wear performance can be explained by the entrapment of wear particles by surface dimples and the formation of an ion mixing layer produced by ion implantation process.
•Regular surface patterns were prepared by laser ablation method.•Wear performance of TiAlSiN coatings was improved by surface texturing and ion implantation.•Friction and wear were found to be reduced on the coating with texturing and ion implantation.
A scheme to achieve stable collisionless shock acceleration (CSA) of ions from a near-critical plasma by intense petawatt-picosecond laser pulses is proposed, where the plasma is confined in a high-Z ...solid tube. The application of the tube, on the one hand, restrains the plasma from transverse thermal expansion, helping to sustain sufficient density steepening required for shock formation and maintenance; on the other hand, due to the induced sheath field along its wall, pinches hot electrons for recirculation near laser axis, aiding to reach efficient plasma heating that is crucial to have a strong shock velocity for ion reflection. Consequently, stable ion CSA can be maintained for picosecond time scales, resulting in production of high-flux high-energy ion beams. Two-dimensional PIC simulations show that proton beams with narrow energy spread between 50 and 80 MeV and high flux with particle number about 1012 are produced by a laser pulse at intensity 8.8 × 1019 W cm−2 and duration 1 ps. By extending the pulse duration to 3 ps, over 100 MeV high-flux proton beams are obtained.
•GNPs uniform dispersion in Ti matrix via HPT processing.•Tendency of microstructure evolution upon HPT.•Preparation of GNPs/Ti nanocomposite without interfacial reactions.
How to obtain the uniform ...dispersion and prohibit severe interfacial reaction simultaneously were the two important problems in graphene nanoplatelets (GNPs) reinforced Ti matrix (GNPs/Ti) composites. In this study, GNPs/Ti nanocomposites were fabricated by using high-pressure torsion (HPT) technique at ambient temperature. The microstructure evolution of the GNPs/Ti nanocomposites during HPT processing were investigated. The results show that the GNPs were homogeneously dispersed under the HPT shear force. Moreover, their intrinsic structure was well-retained with no interfacial reaction. The microhardness of HPT 1wt% GNPs/Ti nanocomposite was increased by 18.6% compared to that of HPT pure Ti processed at 5GPa-5r.
Plantation forestry is expanding rapidly in China to meet an increasing demand for wood and pulp products globally. Fungal pathogens including species of Calonectria represent a serious threat to the ...growth and sustainability of this industry. Surveys were conducted in the Guangdong, Guangxi and Hainan Provinces of South China, where Eucalyptus trees in plantations or cuttings in nurseries displayed symptoms of leaf blight. Isolations from symptomatic leaves and soils collected close to infected trees resulted in a large collection of Calonectria isolates. These isolates were identified using the Consolidated Species Concept, employing morphological characters and DNA sequence comparisons for the β-tubulin, calmodulin, histone H3 and translation elongation factor 1-alpha gene regions. Twenty-one Calonectria species were identified of which 18 represented novel taxa. Of these, 12 novel taxa belonged to Sphaero-Naviculate Group and the remaining six to the Prolate Group. Southeast Asia appears to represent a centre of biodiversity for the Sphaero-Naviculate Group and this fact could be one of the important constraints to Eucalyptus forestry in China. The remarkable diversity of Calonectria species in a relatively small area of China and associated with a single tree species is surprising.
The focus of this study was to identify the effects of increasing ambient temperature (T) at different relative humidity (RH) and air velocity (AV) levels on heat loss from the skin surface and ...through respiration of dairy cows. Twenty Holstein dairy cows with an average parity of 2.0 ± 0.7 and body weight of 687 ± 46 kg participated in the study. Two climate-controlled respiration chambers were used. The experimental indoor climate was programmed to follow a diurnal pattern with ambient T at night being 9°C lower than during the day. Night ambient T was gradually increased from 7 to 21°C and day ambient T was increased from 16 to 30°C within an 8-d period, both with an incremental change of 2°C per day. A diurnal pattern for RH was created as well, with low values during the day and high values during the night (low: RH_l = 30–50%; medium: RH_m = 45–70%; and high: RH_h = 60–90%). The effects of AV were studied during daytime at 3 levels (no fan: AV_l = 0.1 m/s; fan at medium speed: AV_m = 1.0 m/s; and fan at high speed: AV_h = 1.5 m/s). The AV_m and AV_h were combined only with RH_m. In total, there were 5 treatments with 4 replicates (cows) for each. Effects of short and long exposure time to warm condition were evaluated by collecting data 2 times a day, in the morning (short: 1-h exposure time) and afternoon (long: 8-h exposure time). The cows were allowed to adapt to the experimental conditions during 3 d before the main 8-d experimental period. The cows had free access to feed and water. Sensible heat loss (SHL) and latent heat loss (LHL) from the skin surface were measured using a ventilated skin box placed on the belly of the cow. These heat losses from respiration were measured with a face mask covering the cow's nose and mouth. The results showed that skin SHL decreased with increasing ambient T and the decreasing rate was not affected by RH or AV. The average skin SHL, however, was higher under medium and high AV levels, whereas it was similar under different RH levels. The skin LHL increased with increasing ambient T. There was no effect of RH on the increasing rate of LHL with ambient T. A larger increasing rate of skin LHL with ambient T was observed at high AV level compared with the other levels. Both RH and AV had no significant effects on respiration SHL or LHL. The cows lost more skin sensible heat and total respiration heat under long exposure than short exposure. When ambient T was below 20°C the total LHL (skin + respiration) represented approx. 50% of total heat loss, whereas above 28°C the LHL accounted for more than 70% of the total heat loss. Respiration heat loss increased by 34 and 24% under short and long exposures when ambient T rose from 16 to 32°C.
Natural zeolite membranes, directly sectioned from mineral deposits, have been previously reported to show molecular sieve characteristics in selective separation of water and hydrated cations. ...Although a high removal of cations was observed, the low water flux was a limitation for any potential industrial applications. In this study novel clinoptilolite-based phosphate composite membranes were prepared by dry pressing of mixed powder materials followed by high temperature autoclave steaming and characterized by XRD, SEM-EDX. Their performance for pervaporative water desalination was examined using different levels of salinity in a temperature range of 25–95°C and feed side pressure of 1atm. At 1400ppm Na feed salinity and 95°C, a water flux of 15kg/m2h and over 95% removal of Na+ were obtained. The water flux achieved was about 10 times higher than the flux obtained using natural zeolite rock membranes. Introducing phosphate into the composite membranes appears to provide not only mechanical strength, through the possible chemical bonding between zeolite particles and the in-situ phosphate cement, but also to create a chemically favorable interface between zeolite crystals. Such interface might facilitate the desalination process bypassing the technical difficulties of ion leakage/diffusion through the inter-crystal spaces commonly associated with synthetic zeolite membranes.
•Natural clinoptilolite-phosphate composite membranes.•High temperature water desalination process.•98+% of Na+ removal was achieved at 50°C for a saline water with 1400ppm of sodium.•High water flux of ~15kg/m2h was achieved at 95°C.
In this study, remote influence originating from the tropical western Indian Ocean on June precipitation in South China and the Indochina Peninsula is documented. Based on numerical simulation and ...statistical analysis, it is noted that the warm anomaly in the tropical western Indian Ocean can induce a weaker-than-normal Walker circulation across the tropical Indian Ocean and western Pacific Ocean. This further leads to a northeast–southwest-oriented western North Pacific subtropical high and a weaker-than-normal monsoon trough in the South China Sea. In addition, the weak monsoon trough is concurrent with an anomalous rising motion in South China and a sinking motion in the Indochina Peninsula. This enhances precipitation in South China and suppresses precipitation in the Indochina Peninsula on an interannual time scale. On the other hand, the warming trend in the tropical western Indian Ocean also supports the long-term trends of precipitation in the two regions.
A new test technique and bespoke apparatus to conduct high strain rate measurements of the tensile response of materials are presented. The new test method is applicable to brittle solids and ...composites as well as high-performance fibres, yarns and tapes used in composite construction. In this study, the dynamic response of monolithic poly(methyl methacrylate) and unidirectional composites based on Dyneema® tape, Dyneema® SK75 yarn and Kevlar® 49 yarn are explored. The technique allows early force equilibrium and yields valid tensile stress–strain curves, which include part of the elastic material response. The new method also enables investigation of size effects in tape and yarn materials, allowing testing of specimens of arbitrary length.
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