Introduction of polymers into the cement composites improves same of the properties of concretes and mortars. Therefore, the polymer-cement composites are successfully used in construction. The model of microstructure formation in cement composites modified with thermoplastic polymer (pre-mix modifiers) has already been developed and successfully implemented. However, the formation of microstructure in the case of epoxy-cement composites (containing post-mix modifier) demonstrates same peculiarities which should be taken into account when modelling the process. The microstructure of epoxy-cement composites and its formation is discussed in the paper. The model is offered, formulated on the basis of the microscopic observations and results of testing.

In order to achieve extended life of asphalt pavement, one of key points is to achieve a good bonding between it’s components. This research paper presents findings on the topic of influence of polyethylene bitumen modification on the adhesion between bitumen and aggregate. A novel method of quantifying the bitumen coated area, based on computer image analysis, has been developed for this study. Two different methods of adhesion testing were employed, namely boiling water method and the rolling bottle method. Aggregates used in this study were granite and limestone. Based on 108 measurements, it was concluded that polyethylene modification has a negative impact on binder aggregate adhesion.

This article presents shortly reasons for improving designs of turboprop and turboshaft engines, and describes aero-thermodynamic aspects of methods or modification of these devices. The theoretical analysis of methods or modification concerns general changes or efficiency, flow, and rating. The influence of the following factors on engine performance is presented: change of efficiency or engine units, increase of compression and flow rate by using a compressor zerostage, change of compressor pressure ratio, changes of gas temperature keeping the gasgenerator rotational speed constant by adjusting the minimal throat area of turbine nozzle guide vanes, turbornachinery modelling, and changes of rotational speed of ratings.

Liquid AI -Si alloys are usually given special treatments before they are cast to obtain finer or modified matrix and eutectic structures, leading to improved proper ties. For many years, sodium additions to hypoeutectic and eutectic AI -Si melts have been recognized as the most effective method of modifying the eutectic morphology, although most of the group IA or IIA elements have significant effects on the eutectic s tructure. Unfortunately, many of these approaches also have associated several founding difficulties, such as fading, forming dross in presence of certain alloying elements, reduced fluidity, etc. ln recent years, antimony additions to AI -Si castings have attracted considerable attention as an alternative method of refining the eutectic structure. Such additions eliminate many of the difficulties listed above and provide permanent (i.e. non -fading) refining ability. In this paper, the authors summarize work on antimony treatment of Al -Si based alloys.

The purpose of the work was initial modification of the construction of a commercially produced heat exchanger – recuperator with CFD (computational fluid dynamics) methods, based on designs and process parameters which were provided. Uniformity of gas distribution in the space between the tubes of the apparatus as well as the pressure drop in it were taken as modification criteria. Uniformity of the gas velocity field between the tubes of the heat exchanger should cause equalization of the local individual heat transfer coefficient values and temperature value. Changes of the apparatus construction which do not worsen work conditions of the equipment, but cause savings of constructional materials (elimination or shortening some parts of the apparatus) were taken into consideration.

Surface wastewater pollution due to accidental runoff or release of oil or its products is a longstanding and common environmental problem. The aim of the study was to investigate the impact of concentrations of oil products (diesel) and suspended solids, the sorbent type, the water flow rate and the interfering factors (chlorides) on the dynamic sorption of diesel and to test regeneration of polypropylene after its use for sorption. The sorbents used for study included common wheat straw (Triticum aestivum), polypropylene and sorbents modified with hydrogen peroxide solution. Standard methods were used for the determination of the investigated parameters and an in-house procedure employing a gas chromatograph was used for the determination of diesel concentration. The following factors that impact the sorption of diesel were investigated during the study: diesel concentration, concentration of suspended solids; type of sorbent (common wheat straw (Triticum aestivum), wheat straw modified with hydrogen peroxide, and polypropylene), water flow rate; and influence of the interfering factors (chlorides). Filtration speed in the range of investigated speeds does not affect the efficiency of diesel removal. Removal efficiency does not depend on the concentration of diesel before the sorbent reaches its maximum sorption capacity. Filling containing 50% of polypropylene and 50% of wheat straw was used for the study. It was found that polypropylene and wheat straw do not remove chlorides and suspended solids from solution. The study found that the solution of hydrogen peroxide boosts the hydrophobic properties of common wheat straw, but does not affect the sorption of diesel. The recommended number of regenerations of polypropylene should be limited to two.

The paper presents results of a study concerning an AlSi7Mg alloy and the effect of subjecting the liquid metal to four different processes: conventional refining with hexachloroethane; the same refining followed by modification with titanium, boron, and sodium; refining by purging with argon carried out in parallel with modification with titanium and boron salts and strontium; and parallel refining with argon and modification with titanium, boron, and sodium salts. The effect of these four processes on compactness of the material, parameters of microstructure, and fatigue strength of AlSi7Mg alloy after heat treatment. It has been found that the highest compactness (the lowest porosity ratio value) and the most favorable values of the examined parameters of microstructure were demonstrated by the alloy obtained with the use of the process including parallel purging with argon and modification with salts of titanium, boron, and sodium. It has been found that in the fatigue cracking process observed in all the four variants of the liquid metal treatment, the crucial role in initiation of fatigue cracks was played by porosity. Application of the process consisting in refining by purging with argon parallel to modification with Ti, B, and Na salts allowed to refine the microstructure and reduce significantly porosity of the alloy extending thus the time of initiation and propagation of fatigue cracks. The ultimate effect consisted in a distinct increase of the fatigue limit value.

A fading mechanism during casting of treated Al-B-Sr master alloys in an aluminium-silicon cast alloy was investigated. Two different master alloys, the Al-3%B-3%Sr and Al-4%B-1%Sr were demonstrated for the efficiency test both grain refinement and modification microstructure. From experimental result, the addition of Al-3%B-3%Sr master alloy led to a refined grain size and fully modified eutectic Si. However, smaller grain sizes were found with Al-4%B-1%Sr master alloy addition while eutectic Si had coarser acicular morphology. The formation of high amounts of SrB6 compound in the Al-3%B-3%Sr master alloy resulted to increase of grain size and eutectic Si. In fading mechanism test when holding the melt for prolong time, the agglomeration of the SrB6 and AlSiSr compounds at the bottom of the casting specimen was important factors that decreased both grain refinement and modification efficiency. The stirring of the melt before pouring was found that the grain size and Si morphology were improved.

A method of manufacturing hydrogel coatings designed to increase the hydrophilicity of polyurethanes (PU) is presented. Coatings were obtained from polyvinylpyrrolidone (PVP) by free radical polymerisation. The authors proposed a mechanism of a two-step grafting - crosslinking process and investigated the influence of reagent concentration on the coating’s physical properties - hydrogel ratio (HG) and equilibrium swelling ratio (ESR). A surface analysis of freeze-dried coatings using scanning electron microscopy (SEM) showed a highly porous structure. The presented technology can be used to produce biocompatible surfaces with limited protein and cell adhesive properties and can be applied in fabrication of number of biomedical devices, e.g. catheters, vascular grafts and heart prosthesis.

Titania nanotube (TNT) arrays fabricated by anodizing of titanium foil in organic (ethylene glycol) and inorganic (phosphoric acid) electrolytes and thermally modified in argon revealed much improved properties to detect hydrogen peroxide. Horseradish peroxidase and acetate thionine co-absorbed by a dip coating on the TNT electrode were used to detect hydrogen peroxide in phosphate buffered saline. The morphology and electrochemical properties of TNT arrays were studied by scanning electron microscopy, electrochemical impedance spectroscopy and cyclic voltammetry. Well defined oxidation and reduction peaks for potassium ferricyanide have been observed for TNT formed in ethylene glycol and annealed in argon. TNT arrays formed in organic electrolyte and annealed in argon indicated more favorable adsorption and electrochemical properties what was confirmed by detection of hydrogen peroxide towards analyte in phosphorate buffered saline solution.

The presented work discusses the influence of material of foundry mould on the effect of modification of AlSi11 alloy. For this purpose castings were produced in moulds made of four various materials. Castings of the first type were cast in a metal die, the second ones in the conventional mould of bentonite-bound sand, those of the third type in the sand mould with oil binder, the last ones in a shell mould where phenol-formaldehyde resin was applied as a binder. All the castings were made of AlSi11 alloy modified with strontium. For a purpose of comparison also castings made of the non-modified alloy were produced. The castings were examined with regard to their microstructures. The performed investigations point out that the addition of strontium master alloy results in refining of the alloy structure, particularly of the α-phase, causes some morphological changes in the alloy and the refinement of eutectics. The advantageous influence of modifier on the structure of the examined silumin was observed particularly in the case of alloy cast either in the conventional oil-bound sand mould or in the shell mould. The non-modified alloy cast into a metal die exhibits a structure similar to those of modified alloy solidifying in the other moulds. The improvement in both tensile strength and unit elongation suggests that the modification was carried out correctly. The best mechanical properties were found for the alloy cast in a metal die, both with and without modification treatment.

Grain refining and modification are common foundry practice for improving properties of cast Al-Si alloys. In general, these types of treatments provide better fluidity, decreased porosity, higher yield strength and ductility. However, in practice, there are still some discrepancies on the reproducibility of the results from grain refining and effect of the refiner’s additions. Several factors include the fading effect of grain refinement and modifiers, inhomogeneous dendritic structure and non-uniform eutectic modification. In this study, standard ALCAN test was used by considering Taguchi’s experimental design techniques to evaluate grain refinement and modification efficiency. The effects of five casting parameters on the grain size have been investigated for A357 casting alloy. The results showed that the addition of the grain refiner was the most effective factor on the grain size. It was found that holding time, casting temperature, alloy type and modification with Sr were less effective over grain refinement.

This paper presents a study of the effect of the modification and cooling rate on the grain count α(Al) in the Al-5Cu alloy. Research was

performed on castings with walls thickness between 3 mm and 25 mm. Cooling curves were recorded to determine the cooling rate and the

degree of undercooling at the beginning of solidification. It has been shown that cooling rate increases exponentially as the wall thickness

of casting decreases. Moreover it has been demonstrated that the cooling rate of castings changes within a wide range (21ºC/s - 1ºC/s)

when the wall thickness changes from 3 up to 25 mm. Metallographic examinations revealed primary grains (primary α(Al) grains). The

paper show that the relationship between the grain count and the degree of undercooling (for non-modified and modified alloys) can be

represented by the equation N = Nv = np·exp(-b/ΔTα), based on the Weibull's distribution of the size of nucleation sites.

Compacted graphite iron, also known as vermicular cast iron or semiductile cast iron is a modern material, the production of which is increasing globaly. Recently this material has been very often used in automotive industry. This paper reviews some findigs gained during the development of the manufacturing technology of compacted graphite iron under the conditions in Slévárna Heunisch Brno, Ltd. The new technology assumes usage of cupola furnace for melting and is beeing developed for production of castings weighing up to 300 kilograms poured into bentonite sand moulds.

Abstract An attempt has been made to determine the effect of an addition of colloidal suspensions of the nanoparticles of magnesium oxide on the structure of water glass, which is a binder for moulding and core sands. Nanoparticles of magnesium oxide MgO in propanol and ethanol were introduced in the same mass content (5wt.%) and structural changes were determined by measurement of the FT-IR absorption spectra.

Impact of surface and volume modification and double filtration during pouring the moulds on basic mechanical properties and creep resistance of nickel superalloys IN-713C and MAR-247 in conditions of accelerated creep of castings made of post-production scrap of these alloys is evaluated in this paper. The conditions of initiation and propagation of cracks in the specimens were analysed with consideration of stereological properties of material macro- and microstructure. It has been proven that in the conditions of hightemperature creep at 980°C and at stress σ = 150 MPa, creep resistance of superalloy MAR-247 is more than 10 times higher than the creep resistance of IN-713C alloy. In case of IN-713C alloy, the creep resistance negligibly depends on macrograin sizes. But, the macrograin size considerably affects the time to failure of specimens made of alloy MAR-247. Creep resistance of specimens made of coarse grain material was 20% higher than the resistance of fine grain materials.

The effect of combination grain refinement with AlTi5B1 master (55 ppm) and Sr-modification with AlSr5 master (20, 30, 40, 50 and 60 ppm) on the microstructure, tensile and hardness properties of AlSi7MgTi cast alloy were systematically investigated. Eutectic silicon was studied by optical and scanning electron microscopy after standard (0.5% HF) and deep etching (HCl). Morphology of eutectic Si changes from compact plate-like (as-cast state) to fibbers (after modification). Si-fibbers in samples with 50 and 60 ppm Sr coarsen probably as a result of over-modification. The optimum mechanical properties has the experimental material which was grain refined and modified with 40 ppm of Sr (UTS = 220.6 MPa; ductility = 6.1%, and 82.3 HBW 5/250/15).

This paper deals with the effects of modifications to clay-siliceous raw material from Dylągówka (Dynów foothills, SE Poland), which alter the rheological properties of its water suspensions. The investigations were carried out on three samples collected from various depths of the deposit as they considerably differ in their contents of smectite and other minerals. The samples were either modified with soda or activated with sulphuric (VI) acid and used to prepare their water suspensions with various contents of solids. The suspensions were subject to determinations of viscosity and flow curves. Dependencies of three variables of the suspensions (rheological properties, mineral composition of the solid phase, and the modifications introduced) were assessed on the basis of: the contents of the solid phase in the suspensions required to obtain a viscosity of 1000 mPas; hypothetical, calculated thixotropic energy. These show that the amount of solids in the water suspension required to obtain the required viscosity is considerably lower in samples with higher contents of smectite and in those activated with sodium. In turn, the acid activation that partially alters smectite towards a protonated silica gel decreases the viscosity and thixotropy of the suspensions, which was confirmed in the studies of mid-infrared spectroscopy. The conducted studies provide important information needed in designing the mineral composition of drilling fluids and others applications.

This study analyses and presents a technical comparison of seepage estimation from 11 empirical equations with measured seepage losses by the inflow-outflow method from two lined and unlined secondary irrigation canals sub-divided into different reach lengths. A significant margin of error was observed between empirical and inflow- outflow methods, hence modifications in empirical equations were performed. Results reveal that the average seepage losses observed in unlined and lined canals by inflow-outflow method were 9.15 and 3.89%, respectively. Moreover, only the Chinese equation estimated seepage losses for an unlined canal as similar to observed losses (0.11 m ³∙s ^–1) whereas the Indian equation estimated similar results for a lined canal to those observed in the field (0.09 m ³∙s ^–1). However, the rest of empirical equations were modified in accordance with error percentage with regard to the observed losses. The empirical equations were then observed to estimate reliable results of seepage.

In this work, research on influence of multiwalled carbon nanotubes (MWCNTs), produced in Catalic Chemical Carbon Vapor Deposition, NANOCYLTM NC7000CNTs on a structure and properties of AISI 301 steel remelted by TIG arc. In the assessment of influence a type of carbon on properties and structure of austenitic steel, as a carbon filler was use also carburizer. In the specimens (AISI 301 plates) with dimensions 155×60×7 [mm] were drilled holes with 1.3 mm diameter and placed 0.5 mm under specimen surface. Next, to the drilled holes was implemented CNTs, carburizer and mixture of these both powders. Prepared specimens were remelted by TIG method on the CASTOTIG 2200 power source with 2.4 mm tungsten thoriated electrode with parameters sets for obtain 3.0 mm penetration depth. Remelted specimens were cut into the half of the welds distance and prepared for metallographic examinations. Cross sections of the specimens were tested on classical metallography microscopes, hardness tests, SEM analyses (on JEOL 5800 LV SEM EDX equipment) and phase identification by X-ray phase analysis on Philips APD X’Pert PW 3020 diffractometer. Hardness analysis indicates about 25% increase of hardness in the remelted area when the CTNs are used. In the specimens with carburizer there is no significant changes. SEM analyses of remelted areas on AISI 301 specimens modificated with CNTs, indicates that dark areas, initially interpret as one of the phase (based on optical microscope) is finally densely packed bladders with dimensions from 50 nm up to a few µm. These bladders are not present in the specimens with carburizer filler. High resolution scanning microscopy allow to observe in the this area protruding, longitudinal particles with 100-300 nm length. For identification of this phase, X-ray analysis was done. But very small dimensions of used CNTs (diameters about 9,5 nm), random orientation and small weight amount can make difficult or impossible to CNTs detection during XRD tests. It means that it is not possible to clearly determine nature of particles filling the cavities, it is only possible to suppose that they are CNTs beams with nanoparticles comes from their disintegration. Results of the researches indicates, that fill in the weld pool with different form of carbon (CNTs and carburizer) it is possible to achieve remelted beads with different structure and hardness distribution. It confirms validity of the research continuation with CNTs as a modifier of steels and also other metals and theirs alloys.

The morphology of G20Mn5 specimens made of non-modified and rare earth metals (REM) modified cast steel was investigated. Molten metal was treated with a cerium-rich mischmetal contain 49.8% Ce, 21.8% La, 17.1% Nd, 5.5% Pr and 5.35% other rare earth metals making up the balance. The melting, quenching (920°C/water) and tempering (720°C/air) were performed under industrial conditions. Analysis included G20Mn5 cast steel fracture specimens subjected to Charpy V-notch impact testing at 20°C, -30°C and -40°C. The purpose of the analysis was to determine the influence of REM on the microstructure and mechanical properties of G20Mn5 cast steel and the REM effect on the morphology, impact strength and character of the fracture surfaces. In addition, a description of the mechanism by which fracture occurred in the two materials was proposed. The author demonstrated the beneficial effects of adding REM to molten steel, manifested by a 20 - 40% increase in impact toughness, depending on test temperature, as compared to the non-modified cast steel. Important findings included more than 100% increase in impact strength in comparison with the required impact toughness of 27J at -40C for heat treated steels (EN 10213).

With the aid of eutectic modification treatment, the precipitation of coarse lamellar eutectic silicon can be suspended during the solidification of aluminum-silicon alloys, thereby the formation of fine-grained, fibrous eutectic Si can be promoted by the addition of small amounts of modifying elements, such as Sr, to the liquid alloy. The effectiveness of this technique is, however, highly dependent on many technological factors, and the degree of modification can be lowered during the various stages of melt preparation due to the oxidation of the Sr-content of the melt. During our research, we investigated the effect of rotary degassing melt treatments coupled with the addition of three different fluxes on the degree of modification of an Al-Si-Mg-Cu casting alloy. It was also studied, that whether additional Sr alloying made before and during the melt treatments can compensate the Sr fading with time. The degree of eutectic modification was characterized by thermal analysis (TA) and the microscopic investigation of TA specimens. It was found, that by using one of the three fluxes, and by adding Sr master alloy rods before the melt treatments, better modification levels could be achieved. It was also found that the measurement of Sr-concentration by optical emission spectroscopy alone cannot be used for controlling the level of eutectic modification.

In this study, Ni20Cr coatings were obtained by cold spraying on an aluminum alloy 7075 substrate. The obtained coatings were characterized by a uniform microstructure and low porosity. The sprayed coating has the same phase composition as the powder used. Next, the cold sprayed coatings were heat treated using a TRUMPF TLF 6000 TURBO (4 kW) CO2 laser. The laser surface melting of the coatings resulted in the formation of a columnar structure and an improvement in their mechanical properties. The Ni20Cr cold sprayed coatings after additional laser melting showed lower porosity and an increase in microhardness and Young`s modulus.

The paper presents the results of investigations concerning the influence of gray cast iron modification on free vibration frequency of the disc casting. Three different chemical composition melts of gray cast iron were prepared in induction furnace. During gravity casting 0.05% and 0.3% mass of the Inolate modifier was added on stream of metal for changing graphite flakes in castings. Sound signal vibration of cast iron sample was registered by means on microphone for free vibration frequency measurements. Decreasing of free vibration frequency of modified cast iron in comparison with non modified castings was observed. Higher contents of modifier causes more decreasing of free vibration frequency. Cast iron with smaller contents of carbon and silicon have higher free vibration frequency in comparison with eutectic composition cast iron. Hardness of examined cast iron is lower when the more modifier is added during modification process. Free frequency is smaller with smaller Brinell hardness of disc casting. It was concluded that control of free vibration frequency of disc castings by means of chemical composition and modification process can improved comfort and safety of working parts.