The Effect of Foaming Agents on the Thermal Behavior of Aluminum Precursors.

Various foaming agents can be used to achieve foaming of the precursors obtained by using the powder metallurgy method. However, the thermal behavior of pure aluminum precursors with different foaming agents has been studied very little in recent times. For the production of aluminum foams with closed cells, 1 wt.% of calcium carbonate (CaCO3), titanium hydride (TiH2), heat-treated TiH2 and zirconium hydride (ZrH2) were used. The foaming capability of the compacted precursors was investigated at temperatures 700, 720 and 750 °C. CaCO3 and TiH2 showed the best foamability at all considered temperatures, while ZrH2 achieved relatively good foaming only at the highest temperature, 750 °C. Due to their low onset temperature of the decomposition compared to the melting point of the unalloyed aluminum, in hydride-based foaming agents the drainage occurred at the bottom part of the foam samples. Among the investigated foaming agents, precursors with heat-treated TiH2 had the worst foaming properties, while CaCO3 showed the best foamability without the occurrence of drainage.

Study on Surface Roughness, Morphology, and Wettability of Laser-Modified Powder Metallurgy-Processed Ti-Graphite Composite Intended for Dental Application.

In this study, the surface laser treatment of a new type of dental biomaterial, a Ti-graphite composite, prepared by low-temperature powder metallurgy, was investigated. Different levels of output laser power and the scanning speed of the fiber nanosecond laser with a wavelength of 1064 nm and argon as a shielding gas were used in this experiment. The surface integrity of the machined surfaces was evaluated to identify the potential for the dental implant's early osseointegration process, including surface roughness parameter documentation by contact and non-contact methods, surface morphology assessment by scanning electron microscopy, and surface wettability estimation using the sessile drop technique. The obtained results showed that the surface roughness parameters attributed to high osseointegration relevance (Rsk, Rku, and Rsm) were not significantly influenced by laser power, and on the other hand, the scanning speed seems to have the most prevalent effect on surface roughness when exhibiting statistical differences in all evaluated profile roughness parameters except Rvk. The obtained laser-modified surfaces were hydrophilic, with a contact angle in the range of 62.3° to 83.2°.

New Insights of Powder Metallurgy: Microstructure, Durability and Properties.

This Special Issue of Materials, entitled "New Insight of Powder Metallurgy: Microstructure, Durability and Properties", aimed to publish original and review papers on new scientific and applied research making significant contributions to our findings and understanding of the current developments and trends in powder metallurgy (PM) [...].

Structure and Thermal Expansion of Cu-90 vol. % Graphite Composites.

Copper-graphite composites are promising functional materials exhibiting application potential in electrical equipment and heat exchangers, due to their lower expansion coefficient and high electrical and thermal conductivities. Here, copper-graphite composites with 10-90 vol. % graphite were prepared by hot isostatic pressing, and their microstructure and coefficient of thermal expansion (CTE) were experimentally examined. The CTE decreased with increasing graphite volume fraction, from 17.8 × 10-6 K-1 for HIPed pure copper to 4.9 × 10-6 K-1 for 90 vol. % graphite. In the HIPed pure copper, the presence of cuprous oxide was detected by SEM-EDS. In contrast, Cu-graphite composites contained only a very small amount of oxygen (OHN analysis). There was only one exception, the composite with 90 vol. % graphite contained around 1.8 wt. % water absorbed inside the structure. The internal stresses in the composites were released during the first heating cycle of the CTE measurement. The permanent prolongation and shape of CTE curves were strongly affected by composition. After the release of internal stresses, the CTE curves of composites did not change any further. Finally, the modified Schapery model, including anisotropy and the clustering of graphite, was used to model the dependence of CTE on graphite volume fraction. Modeling suggested that the clustering of graphite via van der Waals bonds (out of hexagonal plane) is the most critical parameter and significantly affects the microstructure and CTE of the Cu-graphite composites when more than 30 vol. % graphite is present.

Laser Surface Modification of Powder Metallurgy-Processed Ti-Graphite Composite Which Can Enhance Cells' Osteo-Differentiation.

The paper examines the surface functionalization of a new type of Ti-graphite composite, a dental biomaterial prepared by vacuum low-temperature extrusion of hydrogenated-dehydrogenated titanium powder mixed with graphite flakes. Two experimental surfaces were prepared by laser micromachining applying different levels of incident energy of the fiber nanosecond laser working at 1064 nm wavelength. The surface integrity of the machined surfaces was evaluated, including surface roughness parameters measurement by contact profilometry and confocal laser scanning microscopy. The chemical and phase composition were comprehensively evaluated by scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction analyses. Finally, the in vitro tests using human mesenchymal stem cells were conducted to compare the influence of the laser processing parameters used on the cell's cultivation and osteo-differentiation. The bioactivity results confirmed that the surface profile with positive kurtosis, platykurtic distribution curve and higher value of peaks spacing exhibited better bioactivity compared to the surface profile with negative kurtosis coefficient, leptokurtic distribution curve and lower peaks spacing.

Investigation of the Relationship between Morphology and Thermal Conductivity of Powder Metallurgically Prepared Aluminium Foams.

Among different promising solutions, coupling closed-cell aluminium foam composite panels prepared by a powder metallurgical method with pore walls interconnected by microcracks, with low thermal conductivity phase change materials (PCMs), is one of the effective ways of increasing thermal conductivity for better performance of thermal storage systems in buildings. The internal structure of the foam formation, related to the porosity which decides the heat transfer rate, plays a significant role in the thermal energy storage performance. The dependence of the heat transfer characteristics on the internal foam structure is studied numerically in this work. The foamable precursor of 99.7% pure aluminium powder mixed with 0.15 wt.% of foaming agent, TiH2 powder, was prepared by compacting, and extruded to a volume of 20 × 40 × 5 mm. Two aluminium foam samples of 40 × 40 × 5 mm were examined with apparent densities of 0.7415 g/cm3 and 1.62375 g/cm3. The internal porous structure of the aluminium foam samples was modelled using X-ray tomography slices through image processing techniques for finite element analysis. The obtained numerical results for the heat transfer rate and effective thermal conductivity of the developed surrogate models revealed the influence of porosity, struts, and the presence of pore walls in determining the heat flow in the internal structure of the foam. Additionally, it was found that the pore size and its distribution determine the uniform heat flow rate in the entire foamed structure. The numerical data were then validated against the analytical predictions of thermal conductivity based on various correlations. It has been found that the simplified models of Bruggemann and Russell and the parallel-series model can predict the excellent effective thermal conductivity results of the foam throughout the porosity range. The optimal internal foam structure was studied to explore the possibilities of using aluminium foam for PCM-based thermal storage applications.

Laser-Based Ablation of Titanium-Graphite Composite for Dental Application.

Biocompatible materials with excellent mechanical properties as well as sophisticated surface morphology and chemistry are required to satisfy the requirements of modern dental implantology. In the study described in this article, an industrial-grade fibre nanosecond laser working at 1064 nm wavelength was used to micromachine a new type of a biocompatible material, Ti-graphite composite prepared by vacuum low-temperature extrusion of hydrogenated-dehydrogenated (HDH) titanium powder mixed with graphite flakes. The effect of the total laser energy delivered to the material per area on the machined surface morphology, roughness, surface element composition and phases transformations was investigated and evaluated by means of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), confocal laser-scanning microscopy (CLSM) and X-ray diffraction analysis (XRD). The findings illustrate that the amount of thermal energy put to the working material has a remarkable effect on the machined surface properties, which is discussed from the aspect of the contact properties of dental implants.

A Study of Laser Micromachining of PM Processed Ti Compact for Dental Implants Applications.

The paper deals with the experimental study of laser beam micromachining of the powder metallurgy processed Ti compacts applying the industrial grade fibre nanosecond laser operating at the wavelength of 1064 nm. The influence of the laser energy density on the surface roughness, surface morphology and surface elements composition was investigated and evaluated by means of surface roughness measurement, scanning electron microscopy (SEM), energy dispersive X-Ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis. The different laser treatment parameters resulted in the surfaces of very different characteristics of the newly developed biocompatible material prepared by advanced low temperature technology of hydride dehydride (HDH) titanium powder compactation. The results indicate that the laser pulse energy has remarkable effects on the machined surface characteristics which are discussed from the point of view of application in dental implantology.

Poisson's Ratio of Closed-Cell Aluminium Foams.

A nondestructive impulse excitation technique was used to investigate Poisson's ratio of powder metallurgical pure closed-cell aluminium foams according to ASTM E 1876 within the foam density range of 0.430⁻1.390 g·cm-3. Instead of a constant value of 0.34, as according to Gibson and Ashby's assumption for the Poisson's ratio of metallic foams, the decrease of the Poisson's ratio with decreasing foam density was observed. Observed Poisson's ratio data were in the range of 0.21⁻0.34. To check the validity of the results, the Young's modulus was calculated using Poisson's ratio and its dependence on relative density was successfully modelled using the usual power law function with characteristic exponent of 1.72 ± 0.1. This confirms that the obtained experimental results for Poisson's ratio are valid. Finally, rule of mixture and percolation theory were used to model the observed decrease of Poisson's ratio with increasing porosity.

Blood concentration of copper, cadmium, zinc and lead in horses and its relation to hematological and biochemical parameters.

Environmental pollution results in serious health hazards to animals and blood analysis serves as a good alternative for health status assessment. The target of this study was to analyze the concentration of selected metals in equine blood, to analyze the blood parameters and to find possible correlations. Blood samples were collected from the vena jugularis of healthy adult horses. The highest concentration of all elements was found in whole blood (Cu 3.84 ± 0.90 mg L(-1); Cd = 0.81 ± 0.90 mg L(-1); Zn 26.67 ± 14.12 mg L(-1); Pb 9.33 ± 5.76 mg L(-1)). Higher concentrations of copper, cadmium, zinc and lead were detected in blood clots compared to blood sera (44.04%). A similar tendency was found for cadmium (50%), zinc (13.08%) and lead (46.02%), which showed generally higher concentrations in blood clots (cells). Correlation analysis proved some relations between analyzed elements. In blood clots there is a strong positive correlation between Cd - Pb (r = 0.93) and Zn - Pb (r = 0.71) was detected. For biochemical and hematological parameters mainly medium correlations were detected. Obtained results prove different correlations of analyzed elements in blood components as well as the effect on parameters of blood biochemical and hematological profiles.

Accumulation of zinc, nickel, lead and cadmium in some organs of rabbits after dietary nickel and zinc inclusion.

This study reports the effect of dietary nickel (Ni) and a combination of Ni and zinc (Zn) on the accumulation of lead (Pb), cadmium (Cd), Ni and Zn in muscles, liver and kidneys of rabbits. Female rabbits (Oryctolagus cuniculus) of experimental groups were fed a granular mixture with addition of various concentrations of Ni or Ni+Zn (E1 - 17.5 g NiCl(2) per 100 kg of feed mixture, group E2 - 35.0 g NiCl(2) per 100 kg of feed mixture, group E3 - 17.5 g NiCl(2) per 100 kg of feed mixture and 30 g ZnCl(2) per 100 kg of feed mixture, group E4 - 35.0 g NiCl(2) per 100 kg of feed mixture and 30 g ZnCl(2) per 100 kg of feed mixture). Group C without inclusion of Ni or Zn served as control. After the 90-day experimental period biological material (liver, kidney, musculus longissimus dorsi, musculus biceps femoris) was taken from the animals. Samples were analyzed by the AAS method. Ni added to the FM caused an increase in Cd concentration in the kidneys of the rabbits, significantly in the E3 group in comparison with the control group. In the liver an insignificant decrease of Cd concentration was found. Zn addition in the amount of 30 g to the diet caused an increase of Cd level in the kidney as well as in the liver. Ni and Zn treatment caused a significant decrease of Pb accumulation in the m. longissimus dorsi of rabbits. This study indicates that dietary inclusion of Ni and Zn caused specific interactions among the observed metals.

In vitro assessment of silver effect on porcine ovarian granulosa cells.

The general objective of this in vitro study was to examine the secretory activity (insulin-like growth factor I, IGF-I) of porcine ovarian granulosa cells after Ag addition and to outline the potential intracellular mediators (cyclin B1 and caspase-3) of its effects. Ovarian granulosa cells were incubated with silver nitrate (AgNO(3)) at the doses 0.09, 0.17, 0.33, 0.5 and 1.0 mg/mL for 18 h and compared to the control group without metal addition. The release of IGF-I by granulosa cells was assessed by RIA and expression of cyclin B1 and caspase-3 immunocytochemistry. Our observations show that IGF-I release by granulosa cells was significantly (P<0.05) stimulated by AgNO(3) addition at the doses (0.09-1.0 mg/mL). Similarly to IGF-I the cyclin B1 and caspase-3 expression in ovarian granulosa cells was stimulated by Ag addition (0.09-1.0 mg/mL). In conclusion, the present results indicate, a direct effect of Ag on (1) secretion of growth factor IGF-I, (2) expression of markers of proliferation (cyclin B1) and apoptosis (caspase-3) of porcine ovarian granulosa cells and (3) that the effect of Ag on ovarian cell proliferation could be mediated by IGF-I and cyclin B1. Obtained data indicate the interference of Ag in the pathways of proliferation and apoptosis of porcine ovarian granulosa cells through hormonal and intracellular peptides such as are cyclin B1 and caspase-3.

The effect of deoxynivalenol on the secretion activity, proliferation and apoptosis of porcine ovarian granulosa cells in vitro.

The aim of this in vitro study was to examine the secretion activity, markers of proliferation and apoptosis in porcine ovarian granulosa cells (GCs) after deoxynivalenol (DON) addition. Ovarian granulosa cells were incubated with DON for 24h: 10, 100 and 1000 ng/mL, while the control group received no DON. The secretion of insulin-like growth factor I (IGF-I) and progesterone was determined by radioimmunoassay (RIA) and expression of cyclin B1, PCNA and caspase-3 by immunocytochemistry. IGF-I release by GCs was inhibited by DON, while progesterone release and the expression of cyclin B1 was stimulated by DON (at 1000 ng/mL but not at 10 and 100 ng/mL). PCNA expression was stimulated by DON (at 100 and 1000 ng/mL but not at 10 ng/mL). Caspase-3 expression was not influenced by DON treatment (at all doses). In conclusion, our results indicate, (1) a direct effect of DON on secretion of growth factor IGF-I and steroid hormone progesterone, (2) expression of markers of proliferation (cyclin B1 and PCNA) but not on the (3) expression of marker of apoptosis (caspase-3) in porcine ovarian granulosa cells. This in vitro study suggests the dose-dependent association of DON on porcine ovarian functions.

In vitro assessment of molybdenum-induced secretory activity, proliferation and apoptosis of porcine ovarian granulosa cells.

Molybdenum (Mo) is an essential trace element and it plays an important role in cell functions. The mechanism of the action of molybdenum in connection with growth factor IGF-I, proliferation-related peptide cyclin B1 and apoptosis-related peptide caspase-3 has not been examined previously in porcine ovarian granulosa cells. The general objective of this in vitro study was to examine the secretory activity of porcine ovarian granulosa cells after experimental Mo administration and to outline the potential intracellular mediators of its effects. Ovarian granulosa cells were incubated with ammonium molybdate for 18 hours: 1.0 mg/mL; 0.5 mg/mL; 0.33 mg/mL; 0.17 mg/mL and 0.09 mg/mL, while the control group received no Mo. The secretion of IGF-I was assessed by RIA and expression of cyclin B1 and caspase-3 by immunocytochemistry. IGF-I release was decreased by Mo addition at the doses 1.0 mg/mL and 0.5 mg/mL. The expression of cyclin B1 was stimulated by Mo addition at all doses ranging from 1.0-0.09 mg/mL. Caspase-3 expression was also stimulated after experimental Mo addition at the doses 1.0 and 0.5 mg/mL. These data contribute to new insights regarding the mechanism of action of Mo on porcine ovarian functions, secretory activity, proliferation and apoptosis of granulosa cells through hormonal and intracellular substances such as are cyclin B1 and caspase-3.

Cobalt-induced changes in the IGF-I and progesterone release, expression of proliferation- and apoptosis-related peptides in porcine ovarian granulosa cells in vitro.

Cobalt (Co) is an essential element. The general objective of this in vitro study was to examine dose-dependent changes in the secretory activity of porcine ovarian granulosa cells after experimental Co administration and to outline the potential intracellular mediators of its effects. Concentrations of IGF-I and progesterone were determined by RIA and expression of cyclin B1 and caspase-3 by immunocytochemistry. IGF-I release by granulosa cells was stopped by Co addition at the concentration 1 mg/mL. Progesterone release by granulosa cells was decreased at the lowest Co addition (0.09 mg/mL). In our study the changes of the expression of proliferation related peptide cyclin B1 and apoptosis related peptide caspase-3 in ovarian granulosa cells was observed after experimental Co addition. The molecular pathways stimulated by Co through the expression of cyclin B1 and caspase-3 were found. In conclusion, this study provides novel evidence that cobalt is the factor which can initiate adverse effects in ovarian granulosa cells. These results contribute towards the understanding of mechanisms relating to endocrine disruptor-induced alterations in porcine ovarian granulosa cells.

Nickel-induced blood biochemistry alterations in hens after an experimental peroral administration.

The purpose of this study was to determine certain blood biochemical parameters in hens of Isa Brown breed (n = 20) after nickel administration. Animals were divided into four groups (K, P1, P2, P3). Experimental hens (n = 5; in each group) received nickel (NiCl2) as peroral administration in drinking water in various doses (P1 - 0.02 g NiCl2/L; P2 - 0.2 g NiCl2/L; P3 - 2.0 g NiCl2/L of drinking water) for 28 days. The last group - K (n = 5) was the control, receiving no nickel. Biochemical parameters of mineral profile (calcium; phosphorus; magnesium; sodium; potassium) and of energy and enzymatic profile [(glucose; total cholesterol; total proteins; triglycerides; alanine aminotransferase (ALT) aspartate aminotransferase (AST) gamma glutamyl transferase (GGT) and glutamatdehydrogenase (GLDH)] were analyzed in blood serum on Day 0, 7, 14, 21 and 28 of the experiment. Average levels of mineral metabolism parameters were relatively stable apart from calcium. The evaluation registered a significant decrease in calcium during the experiment mainly in the group with highest nickel concentration in drinking water. No significant differences were detected between groups in energy and enzymatic profile apart from the concentrations of ALT on Day 7. In conclusion, there were significant associations between nickel levels and calcium and ALT in blood serum of the hens. No significant differences were detected in other biochemical parameters of mineral profile (P, Mg, Na, K) and energy and enzymatic profile (glucose, total cholesterol, total proteins, triglycerides, AST, GGT and GLDH) after nickel administration. Our results may contribute to an evaluation of reference levels of analyzed parameters, to monitor the health and nutritional status of hens. In this study also the negative effect of nickel mainly on calcium metabolism was detected.

Environmental levels of cadmium, lead and mercury in brown hares and their relation to blood metabolic parameters.

The purpose of this study was to examine concentrations of selected heavy metals in the liver and kidney of brown hares (Lepus europaeus). In addition, correlations between heavy metals and biochemical parameters in blood plasma were determined. The average concentrations of heavy metals (mmol/L) +/- SD were as follows: liver: Pb 0.221 +/- 0.189, Cd 0.160 +/- 0.140, Hg 0.021 +/- 0.030, kidney: Pb 0.115 +/- 0.125, Cd 1.570 +/- 1.103, Hg 0.030 +/- 0.053. The average concentrations of biochemical parameters in the blood plasma were as follows: Ca 3.16 mmol/L, P 2.19 mmol/L, Mg 1.40 mmol/L, Na 148.71 mmol/L, K 8.12 mmol/L, glucose 6.56 mmol/L, total proteins 56.49 g/L, urea 5.00 mmol/L, total lipids 1.40 g/L, bilirubin 3.97 micro mol/L, cholesterol 1.53 mmol/L, aspartate aminotransferase (AST) 6.06 micro kat/L and alanine aminotransferase (ALT) 1.94 micro kat/L. Average levels of hormones (ng/mL) were as follows: testosterone 2.94, androstendiol 0.13, estradiol 501.59, progesterone 6.63, oxytocin 328.60. Tissue analysis showed an accumulation of lead, cadmium and mercury in the liver and kidney of brown hares. There were no significant correlations between levels of heavy metals in liver, kidney, and biochemical parameters.

Nickel induced alteration of hen body weight, egg production and egg quality after an experimental peroral administration.

In this study the effects of nickel (NiCl2) administered in drinking water (0.02; 0.2 and 2.0 mg NiCl2/L for 28 days) on laying hen body weight, egg production and egg quality is reported. Growth parameters during the experiment were significantly decreased mainly in the group with the highest nickel concentration. In total egg production dose-dependent decrease in all experimental groups was found. Egg weight was mainly affected in the group with the highest nickel concentration. Specific egg weight was not altered. Albumen weight and albumen content was significantly decreased in groups with the highest nickel concentration in comparison with the control group. Egg yolk analysis detected significantly decreased yolk weight in the group with the highest nickel experimental level. In yolk color a significant difference was detected between the group receiving 0.02 and 0.2 mg NiCl2/mL. Eggshell compactness was increased in all experimental groups what could be induced by altered mineralization of eggshell. Results of this study clearly report a negative effect of nickel as an environmental pollutant on laying hen body weight, egg production as well as egg quality.

Mercury-induced alterations in rat kidneys and testes in vivo.

In this study effects of mercury administration on the kidney and testicular structure of adult rats were evaluated. Rats received mercury (HgCl2) in single intraperitoneal dose 20 mg HgCl2 (group A), 10 mg HgCl2 (group B) and 5 mg HgCl2 (group C) per kilogram of body weight and were killed after 48 hours following mercury administration. After the preparation of histological samples the results were compared with control group (K). In kidney decreased diameters of glomeruli and renal corpuscles, damaged tubules with affected quality of tubular cells and infiltration of interstitium were detected. Quantitative analysis demonstrated increased relative volume of tubules and renal corpuscles. Also the number of nuclei and glomeruli was increased in all experimental groups. The diameter of glomeruli and renal corpuscles was decreased. In testis undulation of basal membrane, dilatation of blood vessels in interstitium and occurrence of empty spaces in germinal epithelium were observed. Decreased relative volume of germinal epithelium, increased relative volume of interstitium and increased apoptosis occurrence suggest damaged interstitium and revealed occurrence of edemas. The relative volume of seminiferous tubules showed higher luminization. The number of nuclei was decreased in all experimental groups what is in positive relation with occurrence of empty spaces. Also other evaluated criteria demonstrated significant differences between control group and experimental groups. This study reports a negative effect of mercury on the structure and function of kidney and testes.

Distribution of cadmium and lead in liver and kidney of some wild animals in Slovakia.

The content of cadmium and lead, as risk factors of environment, in liver and kidneys of wild animals as brown hare (Lepus europaeus), yellow-necked mouse (Apodemus flavicollis), wood mouse (Cleithrionomys glareolus), and red deer (Cervus elaphus) were studied. Samples were analyzed by the atomic absorption spectrophotometry method (AAS). The highest levels of cadmium were found in kidneys (0.213-2.387 mg/kg) of all animal species. The concentration of cadmium in liver was 0.032-0.258 mg/kg. The analysis of lead showed that the concentration of this element was higher in kidneys of yellow-necked mouse and wood mouse (0.503-0.780 mg/kg) than in liver (0.177-0.268 mg/kg). In brown hare and red deer a higher accumulation of lead in liver (0.221-1.904 mg/kg) in comparison with kidneys (0.115-0.561 mg/kg) is reported.