Dynamics of ultrafast heated radiative plasmas driven by petawatt laser light

A relativistic petawatt laser light can heat heavy metals over keV temperature isochorically and ionize them almost fully. Copious hard X-rays are emitted from the high-Z hot plasma which acts as X-ray sources, while they work as a cooling process of the plasma. The cooling process can affect on the creation of high energy density plasma via the interaction, however, the details are unknown. The X-ray spectrum depends on the plasma temperature, so that it is worthwhile to investigate the radiation cooling effects. We here study the isochoric heating of a solid silver foil irradiated by relativistic laser lights with a help of particle-in-cell simulations including Coulomb collisions, ionizations, and radiation processes. We have conducted a parameter survey varying laser intensity, 1018-20 W/cm2, to check the cooling effects while keeping the incident laser energy constant. The silver plasma heated mainly by the resistive heating dissipates its energy by keV X-ray emissions in a picosecond time scale. The radiation power from the silver foil is found to be comparable to the incident laser power when the laser intensity is less than 1019 W/cm2 under the constant energy situation. The evolution of the plasma energy density inside the target is then suppressed, due to which a highly compressed collisional shock is formed at the target surface and propagates into the plasma. The radiation spectra of the keV silver plasma are also demonstrated.

Silver nanoparticles – possible applications and threats

Silver is known for its biocidal properties. This metal has been used for decorations and food preservation since ancient times and has also been used in medicine. Silver foil has been used to cover wounds and burns. In addition, silver solutions were created to help fight the microorganisms responsible for causing infections, which helped the wound healing process. Currently, to increase and optimize the properties of silver, it is used on a nanometric scale. Nanosilver, due to its expanded spectrum of properties, is used in many economic sectors, including in the production of disinfectants and food films, as well as in animal farms. Nanoparticles are also the basis of nanomedicine action. Creating new drug complexes with nanosilver and modifying the medical materials used in implantology or dentistry allow the lives of many people to be saved every day. In addition, nanosilver particles are commonly used as a specific disinfectant in the production of hospital materials: dressings, bandages, surgical masks, hospital clothing and shoes, and equipment. With the growing use of nanosilver, there are concerns about its harmful effects on living organisms, because not all its mechanisms of action are known. As is well known, the dose determines the toxicity of a given substance; the case is similar for nanosilver. However, is the dose providing antibacterial and antifungal properties non-toxic to animals and humans? This review presents a summary of the scientific research showing the scope of nanosilver activity and the resulting threats.

Fundamental Research on the Structure and Properties of Electroerosion-Resistant Coatings on Copper

The electroerosion-resistant coatings of CuO–Ag and ZnO–Ag systems were obtained on the Cu surface. The formation of the coating was caused by the processing of copper surface with a plasma formed in the electrical explosion of silver foil with a weighed sample of copper oxide or zinc oxide. After electroexplosion spraying, the electron-beam treatment of coatings was performed. The nanohardness, Young modulus, wear resistance, friction coefficient, and electrical erosion resistance of the formed coatings were studied. All studied properties exceed those of copper. Electrical erosion coatings were studied by the methods of scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. It became possible to achieve the high level of operational properties of electrical erosion coatings due to their nanostructurization. Structure of coating is formed by cells of high-speed crystallization. The size of cells varies within the range from 150 nm to 400 nm. The cells are separated by interlayers of the second phase whose thickness varies as 15–50 nm. By method of atomic force microscopy, the separate particles of ZnO or CuO of different shapes and 10–15 nm in size chaotically located in silver matrix were revealed as well as spherical particles of ZnO or CuO in size of 2–5 nm. The total thickness of coatings is 60 μm. The complex of studies we have carried out permits to recommend the integrated processing for strengthening the switch copper contacts of powerful electrical networks.

The Behavior of Sheep Leather Parchment to Artificial Ageing

Parchment used for restoration, book binding and art requires special performance on physical-chemical, organoleptic and aesthetic characteristics, but also good long-term stability. In this sense, the parchment is ecologically processed, with features that ensure firmness, fullness, light resistance, dimensional stability, thermal stability, malleability, flexural/pressure bending resistance. For a good behaviour in time and to artificial ageing, it is found that in the case of parchments made/obtained from sheepskin, the fat or volatile matter content must be as low as possible. The parchment with these qualities allows for the creation of new covers or historical replicas, complements for the integration of old covers, hot and/or cold stamping modelling, incision, entrainment, deposition of gold and silver foil, colouring and decoration with pigments and dyes. Some niche areas such as book bindings and art require a dedicated craftsmanship that promotes the survival of artisanal forms of production and the perpetuation of local creativity and identity. The parchments have undergone artificial ageing treatments based on the concomitant action of temperature and relative humidity for up to 16 days. Chemical (volatile matter, extractable substances, total ash, total nitrogen, dermal) and physical-chemical (measurement of colour variation and shrinkage temperature) analyses were performed to evaluate colour parameters and collagen hydrostability. The fat content of the parchment leads to oxidation reactions that cause the bathochromic effect, closing the colour, but also the deterioration over time of the fibrillar structure by depreciating the contraction temperature.

Effect of joining temperature on Al2024/Ag/Ti-6Al-4V joints during transient liquid phase bonding

The objective of this study is to investigate the effect of bonding temperature on the microstructure and mechanical properties of Al2024 and Ti-6Al-4V diffusion bonds using a 30 μm pure silver foil as interlayer. Using optical microscopy, scanning electron microscopy, line scan and X-ray diffraction, the interfaces of joints were evaluated. The mechanical properties of joints were measured using Vickers micro-hardness and shear strength. At the bonding temperature of 570°C joints contained a non-uniform distribution of elements and various intermetallic phases. With increasing bonding temperature, an uninterrupted microstructure is achieved. According to the results, liquid eutectic formed between Ag interlayer and Al2024, while solid-state diffusion occurs between the Ag interlayer and Ti-6Al-4V. The increase in bonding temperature from 570 to 580 °C resulted in higher shear strength, from 71 MPa to 121 MPa.

Spectroscopy Investigation of Triptych Icon from the Borsa Church, Maramures County

A triptych icon from the 18th century from Borsa Maramure�s County, Romania was investigated by physical-chemical destructive and nondestructive methods: Fourier Transform Infrared (FTIR) spectroscopy, X-ray Fluorescence (XRF), X-Ray Diffraction and thermal analysis by Differential Scanning Calorimetry (DSC). There were identified: gypsum as ground, wooden stage (lime wood), egg yolk as binder, pigments from the painting layer (red lead, green malachite and white lead), silver foil, iron bolus and animal glue for ground. The scientific investigation of various religious objects in general, this wooden icon in the present case, is a mandatory step in the approach to conservation and restoration of cultural goods.