Jozefa Lukovičová

Barrier–cluster–heating model and photoinduced phenomena in chalcogenide glasses

Barrier–cluster–heating model of disordered semiconductors was originated by synthesis of the barrier–cluster model (which was described in the previous works of authors) and of the local heating model (published short time ago). The synthesis of these two models brought synergic effect enabling deeper understanding of physical processes in amorphous semiconductors. The article gives a new view on the essence of some optical and photoinduced effects in chalcogenide glasses on the base of the barrier–cluster–heating model.

Some open problems in physics of disordered materials (and their possible solutions on the base of the barrier-cluster-heating model)

The paper briefly summarizes the basic problems in physics of disordered materials, namely in physics of non-crystalline semiconductors. Although there was much attention devoted to the research in this area, many questions about the nature of processes taking place in these substances still remain unanswered. This article familiarizes the readers with the barrier-cluster-heating model of disordered semiconductors and discusses the possibility of explanations of the mentioned phenomena on its base. This article offers the explanation of the mid-gap absorption and mid-gap photoluminescence on the base of the barrier-cluster-heating model.

The Firing Temperature of Romanesque Brick from Pác

Abstract A pavement brick taken from a Romanesque part of the church in Pác, in the Trnava County, Slovakia, was investigated by x-ray diffraction analysis (XRD) and thermal analyses as differential thermal analysis (DTA), thermogravimetry (TG) and thermodilatometry (TD). It was found that the brick contained dehydroxylated illitic clay, calcite and quartz. As revealed, dehydroxylation was completely finished and no redehydroxylation was observed. Partial decomposition of calcite was also found. The estimated firing temperature is between 600 °C and 700 °C.

Thermophysical Properties of Cement Based Composites with Addition of Plastic Fibers and Horse Manure

Effect of different amount of plastic fiber and horse manure addition on thermophysical properties of cement based composite is studied. 1-D process of water uptake, and porosity measurement were carried out to understand the structural changes. Horse manure has high microfiber content, so that the difference between plastic and natural fiber was compared.

Investigation of thermo-physical properties of thermal insulation coating

This paper examines the thermal properties of thermal insulation coating applied to the building materials surfaces. The main objective is to determine the insulation coating impact on the heat flux transfer. The heat flux is modelled in terms of the heat transfer coefficient on the surface of a solid body. The thermal conductivity and heat transfer coefficient are obtained from the solution of the inverse heat conduction problem in 3D, based on the temperature measurements. The real temperature evolution is perturbed due to intrinsic properties of the measuring apparatus. We correct this situation via modelling a thermocouple function. Afterwards the determination procedure of the heat flux transfer parameters is a standard solution of the inverse problem based on the minimization of discrepancy between corrected measured data and computed temperature data.This paper examines the thermal properties of thermal insulation coating applied to the building materials surfaces. The main objective is to determine the insulation coating impact on the heat flux transfer. The heat flux is modelled in terms of the heat transfer coefficient on the surface of a solid body. The thermal conductivity and heat transfer coefficient are obtained from the solution of the inverse heat conduction problem in 3D, based on the temperature measurements. The real temperature evolution is perturbed due to intrinsic properties of the measuring apparatus. We correct this situation via modelling a thermocouple function. Afterwards the determination procedure of the heat flux transfer parameters is a standard solution of the inverse problem based on the minimization of discrepancy between corrected measured data and computed temperature data.

Thermophysical properties of cement based composites and their changes after artificial ageing

The usage of recycled plastic materials in concrete mix gained increased attention. The behaviour of such environmental friendly material is studied. In this paper an investigation of the thermophysical properties of cement based composites containing plastic waste particles with different percentage is presented. Measurements were carried out using pulse transient method before and after artificial ageing in climatic chamber BINDER MKF (E3).

Order and disorder and their influences on optical absorption of glasses in the gap region

The exponential increase of the absorption coefficient near the absorption edge is usually explained by existence of the density-of-states tails. Among the quoted theoretical models which are widely used to explain the manifestations of the Urbach rule in semiconductors, are the Sumi–Toyozava and the Dow–Redfield models and ab initio (from begining) theory. Our barrier-cluster-heating model assumes the different creating mechanism of exponential tails. The energy by optical transition is provided to electrons except from photons also from vibration of microregion. It deals about the replenishment of absented photons energy, which is smaller as gap width. Absented energy needed for the transition by light absorption is acumulated in certain microregions of material in the form of vibrational energy. At absorption sufficiently big package of accumulated energy can be used. Energy of emptied microarea is filled by phonons from surrounding of microarea (as result of temperature status of surrounding), resp. p...

Mid-gap phenomena in chalcogenide glasses and barrier-cluster-heating model

The physical mechanism of photoluminescence spectrum formation of chalcogenide glasses (CHG) belongs to the important unsolved problems in physics of non-crystalline materials. Photoluminescence is an important means of the electron spectrum investigation. PL spectrum in CHG is produced mostly in the middle of the band gap, and its profile is normal - Gaussian. Several features of PL spectra in CHG is still a great mystery. The aim of the paper is to make reader acquainted with the new insight into the problem. In this article we also deal with the issue of clarifying the nature of mid-gap absorption. From the experiments it is known that after excitation of the glass As2S3 (or As2Se3) with primary radiation from Urbach-tail region the glass will be able to absorb the photons of low energy (IR) radiation from mid-gap region of spectra. This low photon absorption without action of the primary excitation radiation of the higher photon energy is impossible. Mid-gap absorption yields boost in the photolumines...

Determination of Poroelastic Parameters of Porous Building Materials

Variations of sorption moisture in the capillary porous materials result in strong fluid-skeleton interactions due to molecular and surface forces, which produce moisture-induced deformation. The effect of moisture sorption on the non-linear elastic behavior of hygroscopic porous building materials has been experimentally investigated showing strong influence of moisture especially in the lower moisture content range. In the framework poroelasticity moisture influence on elastic behavior is described by two poroelastic coefficients, which present the fluid-skeleton coupling. This paper presents an application of the procedure for the determination of the coupling coefficients for medieval brick.

Self-Diffusion on Pd(111) from the Point of View of the Band Model of Diffusion

In this article we present a different view on the results of experimental investigation of the self - diffusion on Pd (111) published in „Surface Science“ [1]. Our consideration is based on the band model of diffusion. This model is able to explain the Meyer-Neldel rule (MNR) and to clarify “puzzles” mentioned in [1]. The aim of this article is also to familiarize the readers with this model, to the band model of diffusion.