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  • Author: Ewa Borowiak x
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Preparation and characterization of catalyst mix Fe-Co/MgO for carbon nanotubes growth

Preparation and characterization of catalyst mix Fe-Co/MgO for carbon nanotubes growth

Fe-Co/MgO is one of the most common catalyst mix applied to carbon nanotubes (CNTs) growth in chemical vapor deposition process. Therefore, here we present detailed study on the preparation and characterization of Fe-Co/MgO. The precursors of Fe and Co are iron (II) acetate and cobalt acetates, correspondingly. The molar ratio of the catalyst mix is Fe:Co:MgO=1:1:100. Initially, thermogravimetric analysis (TGA) of the mixture was performed. TGA analysis of it indicated the stepwise mass losses which pointed out the crucial thermal conditions for the changes in the elemental composition, morphology, crystallographic structure and vibrational properties. In current state of the art the lowest growth temperature for singlewalled carbon nanotubes is 550°C in CVD technique and here the characterization of the catalyst mix strongly suggest that this temperature can be decreased what would enhance the compatibility of CNT growth with current complementary metal-oxide-silicon (CMOS) technology for CNTs-based nanoelectronics. The morphology, crystallographic structure, elemental composition of the samples and its spectroscopic properties were performed via high resolution transmission electron microscopy (TEM), X-ray diffraction (XRD) and Infrared spectroscopy (IR), respectively.

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Reversible electron charge transfer in single-wall carbon nanotubes

Reversible electron charge transfer in single-wall carbon nanotubes

Single-wall carbon nanotubes (SWCNT) have proved to be very special materials due to their unique electronic properties. Over the last years many scientists have dedicated their research to the study of the these materials as an electronic system. Amphoteric doping effects (n-type and p-type), which can be reversed, became a very popular way of manipulating the optic and electronic properties of carbon nanotubes. In the particular case of SWCNT, the most common and widely used procedure, which changes their properties, is acid treatment applied as a purification procedure. The effect of the addition of this kind of the dopant has been widely studied but not fully understood so far. Here, we present a study, of two kinds of SWCNT, produced within different techniques: (i) chemical vapors deposition and (ii) laser ablation. The main difference between the two types is the diameter distribution of the obtained materials, which is broad in the first technique and narrow in the second. After the acid treatment it is possible to observe a diameter sensitive doping effect on both samples. Resonance Raman spectroscopy, optical absorption spectroscopy (OAS) in UV/Vis/NIR and the Fourier transform middle-infrared (FTIR) spectroscopy have been applied for the characterization of the samples.

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Synthesis of carbon nanotubes via chemical vapor deposition by using rareearth metals as catalysts

Synthesis of carbon nanotubes via chemical vapor deposition by using rareearth metals as catalysts

This work presents the results of the synthesis of carbon nanotubes using the CVD method. Fe: MgO catalyst was used, also in combination with rare earth elements (gadolinium (Gd), dysprosium (Dy)), which when used alone, are not efficient as catalysts in nanotube growth. Synthesis was performed both at reduced pressure (10-3 mbar) and atmospheric pressure, with constant parameters dependent on the process parameters.

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Stress coping styles and occupational burnout syndrome of nurses employed in intensive care units

Abstract

Aim. The aim of the study is to evaluate a relationship between demographic and work-related factors and a work stress coping style as well as a relationship between a work stress coping style and symptoms of occupational syndrome.

Material and methods. Material was collected from 50 nurses employed in intensive care units of clinical hospitals of the Medical University of Lodz. The study was conducted as a diagnostic survey using the following survey techniques: author’s questionnaire and the Coping Inventory for Stressful Situations (CISS).

Results. The study group demonstrated the highest mean value for the task-oriented coping style and the lowest mean value – for the avoidance-oriented coping style. Age, education level and subjective determination of the degree of work-related stress affect the value of the task-oriented coping style. The emotion-oriented stress style is accompanied by heart palpitations and avoidance of physical activity. The value of the avoidance-oriented coping sub-style, i.e. distraction, depends on atmosphere at workplace, heart palpitations and sleep problems. The value of the avoidance-oriented coping sub style, i.e. social diversion, is contributed by marital status, fertility and work organization.

Conclusions. Nurses working in intensive care units prefer the task-oriented coping style. Work stress coping style is related to demographic factors and perception of work environment. An unadaptive style of coping with work-related stress is accompanied by symptoms of somatic occupational burnout syndrome.

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Photocatalytic mineralisation of humic acids using TiO2 modified by tungsten dioxide/ hydrogen peroxide

Photocatalytic mineralisation of humic acids using TiO2 modified by tungsten dioxide/ hydrogen peroxide

TiO2 of anatase structure was modified by tungsten dioxide and H2O2 in order to obtain WO3-TiO2 photocatalyst with enhanced photocatalytic activity under both, UV and artificial solar light irradiations. WO2 was dissolved in 30% H2O2 and mixed with TiO2 in a vacuum evaporator at 70°C. Such modified TiO2 was dried and then calcinated at 400 and 600°C.

The prepared samples and unmodified TiO2 were used for the photocatalytic decomposition of humic acids (Leonardite standard IHSS) in the aqueous solution under irradiations of both, UV and artificial solar light. Modification of TiO2 with tungsten dioxide and H2O2 improved separation of free carriers in TiO2 which resulted in the increase of OH radicals formation. Calcination caused an increase of anatase crystals and higher yield in OH radicals. The uncalcined samples showed high abilities for the adsorption of HA. Combination of adsorption abilities and photocatalytic activity of photocatalyst caused that the uncalcined TiO2 modified with WO2/H2O2 showed the shortest time of HA mineralisation. The mineralisation of HA under the artificial solar light was much lower than under the UV. It was proved that, although OH radicals are powerful in the decomposition of HA, adsorption can facilitate the contact of the adsorbed molecules with the photocatalyst surface and accelerate their photocatalytic decomposition.

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Counteracting domestic violence against elders in the professional practice of a nurse employed in the primary health care system

Abstract

Aim. Assessment of preparation of a nurse – employee of the primary health care for providing preventative measures against domestic violence targeted at elders.

Material and methods. The material was collected in a group of 70 nurses – employees of the primary health care of a medical centre in Lodz. Inclusion criteria were: the respondent’s consent for the inclusion in the study and the position of a nurse of the primary health care system. The authors of the study used the diagnostic survey method, with the application of their own questionnaire. Obtained results were statistically analysed.

Results. In the nurses’ opinion, lack of knowledge of effective tools, which could be used to provide victims with help, considerably hampers implementation of preventive measures for counteracting domestic violence. A multivariate analysis revealed a relationship between the opinion of nurses on prevention of domestic violence against the elderly and their education, the number of years worked and individual beliefs.

Conclusions. Violence against elders is a growing global problem. Polish nurses are legally obliged to initiate interventions in order to counteract domestic violence. Nurses from the primary health care are not prepared to carry out prevention of violence against the elderly. There is a need to provide nurses employed in the primary health care with post-graduate training on counteracting domestic violence against the elderly.

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Single-walled carbon nanotubes fractionation via electrophoresis

Single-walled carbon nanotubes fractionation via electrophoresis

This work presents the influence of the sonication time on the efficiency of the metallic/semiconducting (M/S) fractionation of diazonium salt functionalized single-walled carbon nanotubes (SWCNTs) via free solution electrophoresis (FSE) method. The SWCNTs synthesized via laser ablation were purified from amorphous carbon and catalyst particles through high vacuum annealing and subsequent refluxing processes in aqua regia solutions, respectively. The purified material was divided into two batches. The SWCNTs samples were dispersed in 1% SDS solution in ultrasound bath for 2 and 12 hours. Both dispersed SWCNTs samples were functionalized with p-aminobenzoic acid diazonium salt and fractionated via free solution electrophoresis method. Afterwards, the fractionated samples were recovered, purified from surfactant/functionalities by annealing and investigated via UV-Vis-NIR optical absorption spectroscopy (OAS). The efficiency of the fractionation process was estimated through the comparison of the van Hove singularities (vHS) presented in the obtained fractions to the starting SWCNTs.

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