Nitrogen-vacancy centers in diamond (NV) attract great attention because they serve as a tool in many important applications. The NV center has a polarizable spin S = 1 ground state and its spin state can be addressed by optically detected magnetic resonance (ODMR) techniques. The m S = 0 and m S = ±1 spin levels of the ground state are separated by about 2.88 GHz in the absence of an external magnetic field or any other perturbations. This zero-field splitting (ZFS) can be probed by ODMR. As this splitting changes as a function of pressure and temperature, the NV center might be employed as a sensor operating at the nanoscale. Therefore, it is of high importance to understand the intricate details of the pressure and temperature dependence of this splitting. Here we present an ab initio theory of the ZFS of the NV center as a function of external pressure and temperature including detailed analysis on the contributions of macroscopic and microscopic effects. We found that the pressure dependence is governed by the change in the distance between spins as a consequence of the global compression and the additional local structural relaxation. The local structural relaxation contributes to the change of ZFS with the same magnitude as the global compression. In the case of temperature dependence of ZFS, we investigated the effect of macroscopic thermal expansion as well as the consequent change of the microscopic equilibrium positions. We could conclude that theses effects are responsible for about 15% of the observed decrease of ZFS.

No abstract

Energy efficient buildings are unimaginable without highly insulating thermal envelopes. Mineral wool among others is a popular material for thermal insulation. Architects and engineers usually use the data given by the manufacturer in the specification of the material for their building physical design. Such data are obtained from laboratory measurements, carried out on non-aged, and dry samples. However, moisture could affect the thermal performance of insulation materials and may affect the durability too. In the research, we examined stone mineral wool hardboard thermal insulations, which were obtained from a flat roof. The samples looked differently: some of them were in good condition and maintained their load bearing capability, but some were spoiled and soft. We measured and compared the used samples' thermal conductivity, sorption isotherm and deformation under compressive force to new etalon samples. We also investigated the reason behind the lack of load bearing durability of the built-in and spoiled mineral wool boards using scanning electron microscopy and derivatography. In our study, we show how built-in conditions changed the thermal and mechanical properties and thermal performance of the mineral wool insulation layer, which could degrade by up to 40% in terms of thermal resistance under built-in conditions due to certain spoiling and production mistakes of mineral wool.

No abstract

In the article the possibility of using a surface blast-cleaning waste as a replacement of fine aggregate in concrete manufacturing was presented. Concretes with w/c ratio 0.6 and 300 kg/m3 dosage of cements: CEM I 32.5R and CEM II/B-V 32.5N were tested. The quite high value of the w/c ratio resulted in good compactibility of the mixtures without use of plasticizer. The replacement rate of the fine aggregate (0–2 mm) with copper slag (CS) was 33%, 66% and 100% respectively. Concretes of the same composition served for reference except for with river sand as fine aggregate instead of slag. The performed tests focused on: compressive and tensile strength (both after 28 days), sorptivity, free water absorption capacity and abrasion resistance. The obtained results showed that the strength and some other tested properties of concretes with copper slag as sand replacement were similar or even better than that of the control mixtures.