Search

MoCu alloys were fabricated by the mechanical alloying method and consolidated by cold and hot pressing at 950 °C with the addition of ceramic α-Al2O3(1–2.5 wt%). XRD was used to define the crystallinity and lattice defects of the mixed powder, milled powders, and hot-pressed samples after mechanical alloying experiments. The crystallite size of Mo and Cu significantly decreased after the milling process and the homogeneous phase distribution was found in the hot-pressed specimen, however, large agglomerates of Mo and α-Al2O3particles were found in the mixed specimens. The lattice parameter and lattice strain values indicated the existence of a finer Cu fraction positioned on the grain boundaries of Cu. Based on the SEM-EBSD analysis, the isotropic crystallographic texture was found in all samples. The hardness (265–266 HB) and yield strength (849–878 MPa) were significantly increased in the bulk samples due to the effect of milling and relative density still reached 95 %. The hardness and yield strength were improved in the milled and mixed samples by increasing the α-Al2O3content, however, formability was decreased equally.

In their seminal work, Cordero-Erausquin, Nazaret and Villani (Adv Math 182(2):307-332, 2004) proved sharp Sobolev inequalities in Euclidean spaces via Optimal Transport, raising the question whether their approach is powerful enough to produce sharp Sobolev inequalities also on Riemannian manifolds. By using L1-optimal transport approach, the compact case has been successfully treated by Cavalletti and Mondino (Geom Topol 21:603-645, 2017), even on metric measure spaces verifying the synthetic lower Ricci curvature bound. In the present paper we affirmatively answer the above question for noncompact Riemannian manifolds with non-negative Ricci curvature; namely, by using Optimal Transport theory with quadratic distance cost, sharp Lp-Sobolev and Lp-logarithmic Sobolev inequalities (both for p>1and p=1) are established, where the sharp constants contain the asymptotic volume ratioarising from precise asymptotic properties of the Talentian and Gaussian bubbles, respectively. As a byproduct, we give an alternative, elementary proof to the main result of do Carmo and Xia (Math 140:818-826, 2004) and subsequent results, concerning the quantitative volume non-collapsing estimates on Riemannian manifolds with non-negative Ricci curvature that support Sobolev inequalities.

•Non-destructive analytical methods were efficient to identify stone raw materials at Maklár.•This article shed light on network between Burgenland, Moravia and the Great Hungarian Plain.•Different raw materials were used to make polished stone axes with shaft-hole.•Stone remain an important raw material during the Bronze Age and must be investigated.

Aniline is one of the most important chemical in the polyurethane industry and it is produced by the catalytic hydrogenation of nitrobenzene. The development of novel, multifunctional catalysts, which are easily recoverable from the reaction mixture is therefore of paramount importance. Transition metal-containing ferrites decorated with palladium were prepared by using a combination of sonochemical and combustion steps. First of all, magnetic ferrites were produced to be used in catalyst preparation as supports for palladium nanoparticles. On the surface of the ferrite particles palladium nanoparticles were deposited by applying ultrahigh sonication in an alcoholic phase. All in all, three magnetic catalysts, Pd/NiFe2O4, Pd/ZnFe2O4, and Pd/NiZnFeO4have been created. The catalysts have been tested and their activity have been compared in nitrobenzene hydrogenation to synthesize aniline at four different temperatures, and 20 bar pressure. The most active catalysts were the Pd/ZnFe2O4and Pd/NiZnFeO4systems with which aniline yields of 99.2 and 92.8 n/n% were achieved after 3 h of hydrogenation, respectively. In contrast, by applying the Pd/NiFe2O4catalyst, a significantly lower aniline yield was achieved. It was proved that, due to their magnetic properties, the prepared catalysts are easily removable from the reaction medium by using a magnetic field. Thus, catalysts with excellent properties have been successfully developed and tested in nitrobenzene hydrogenation.

The Jenkyns Event or Toarcian Oceanic Anoxic Event was an episode of severe environmental perturbations reflected in carbon isotope and other geochemical anomalies. Although well studied in the epicontinental basins in NW Europe, its effects are less understood in open marine environments. Here we present new geochemical (carbon isotope, CaCO3, [Mn]) and nannofossil biostratigraphic data from the To¨lgyhát and Kisgerecse sections in the Gerecse Hills (Hungary). These sections record pelagic carbonate sedimentation near the margin of the Tethys Ocean. A negative carbon isotope excursion of c.6‰ is observed in the To¨lgyhát section, in a condensed clay and black shale layer where the CaCO3content drops in association with the Jenkyns Event. At Kisgerecse, bio- and chemostratigraphic data suggest a gap in the lower Toarcian. The presence of an uppermost Pliensbachian hardground, the absence of the lowermost Toarcian Tenuicostatum ammonite zone and the condensed record of the Jenkyns Event at To¨lgyhát, together with a condensed Tenuicostatum Zone and the missing negative carbon isotope anomaly at Kisgerecse, imply arrested carbonate sedimentation. A calcification crisis and sea-level rise together led to a decrease in carbonate production and terrigenous input, suggesting that volcanogenic CO2-driven global warming may have been their common cause.

This article is focused on the development of geopolymer–glass foam composite, produced by encapsulation of glass waste based lightweight aggregate in geopolymer matrix. The aim of the investigation was to encase glass foam with optimum cell size in geopolymer in order to obtain lightweight environmentally friendly concrete from waste materials. Physical properties (uniaxial strength and specimen density) of the geopolymer–glass foam composite were determined, while XRD, SEM and FTIR measurement were carried out to investigate the structure of the resulted composite. The density of the composite compared with the neat geopolymer decreased by 76%. XRD results show that amorphous gel was developed from fly-ash and glass foam. The SEM results confirmed the zeolite crystallization and revealed the gel reinforcing arrangement of it. FTIR results show difference in the material structure between the inner part of geopolymer matrix and the interface of geopolymer–glass foam.

By applying ultrasonic cavitation, palladium particles were deposited onto the surface of two different types of carbon nanotubes (nitrogen-doped bamboo-shaped carbon nanotubes, N-BCNT and multiwalled carbon nanotubes, MWCNT). To achieve this, palladium ions have been reduced by the adsorbent (N-BCNT or MWCNT) itself. Hydroxyl functional groups were identified on the surface of the MWCNTs, while amine groups have been found on the N-BCNTs. The Zeta potential was lower (−9.8 mv) in the case of the N-BCNT sample, than for MWCNT (−6.1 mV), which was in accordance with their different dispersibility in aqueous phase. The incorporated nitrogen atoms and their oxidized forms within the N-BCNT structure lead to increased adsorption capacity and thus, this type of nanotube is more efficient adsorbent for Pd particles, than MWCNT. The higher adsorption capacity of the N-BCNTs can be explained by the presence of nitrogen atoms which increase the interaction between the Pd and nanotubes. Both Pd/nanotube systems show high catalytic activity (after 30 min – 99% aniline yield) in hydrogenation of nitrobenzene to aniline. Thus, palladium coated carbon nanotubes were synthetized in a one-step reduction procedure, and the produced composites are applicable as catalysts in heterogeneous hydrogenation reactions.

Nitrogen-free multi-wall carbon nanotubes (MWCNTs) and N-doped bamboo-like carbon nanotubes (BCNTs) were synthesized by using catalytic vapor deposition (CVD) and used as catalyst support materials. Pd, Rh, Ru, and Ir have been deposited onto the nanotubes to achieve metal/nanotube catalysts. The catalytic activity of the samples was fine-tuned by changing the type of support. BCNT supported Pd and Rh (Pd/BCNT, Rh/MWCNT) catalysts were found to be the most active for liquid phase hydrogenation of octadecene amongst these samples. The initial olefin hydrogenation rate of the Pd/BCNT sample was slightly higher than the corresponding MWCNT-supported catalyst. Based on the hydrogenation reaction, the performance of these catalyst had been ranked as follows: Pd/BCNT ≈ Rh/MWCNT > Pd/MWCNT > Rh/BCNT >  > Ir/MWCNT > Ru/BCNT > Ir/BCNT > Ru/MWCNT. The structural properties of chemisorbed Pd on MWCNT and N- BCNT were also characterized by means of computational chemical methods in order to shed some light on the nature of metal binding properties of N-doped and undoped surfaces. The calculations shown preference towards the edges of the surfaces which is in good agreement with the experimental findings.

Nitrogen-doped bamboo-like carbon nanotube (N-BCNT) coating was synthesized onto the surface of zeolite beads by using Catalytic Chemical Vapour Deposition (CCVD) method to develop a "support on support" (SoS) system. These complex structured materials were used as supports during the preparation of hydrogenation catalysts. Rhodium, palladium and platinum nanoparticles were deposited homogeneously onto the surface of the N-BCNTs of the SoS (final metal content 2 wt%). The catalytic activity of these samples was compared in the hydrogenation of nitrobenzene. The Pt/N-BCNT-zeolite sample was the most active (182 mol nitrobenzene after 30 min). The activity of the other two catalysts at 20 bar was well below this value, 99.5 mol after 60 min and 96 mol after 120 min for Pd and Rh, respectively. The aniline selectivity was different for the three catalysts and they facilitate the formation of various by-products (e.g. N -methylaniline, cyclohexylamine). The usage of the Pd and Pt/N-BCNT-zeolite catalysts are more convenient, as only one main by-product was formed. It was confirmed that the zeolite supported N-BCNTs are efficient catalyst supports in hydrogenation processes. Furthermore, by using this special SoS structure to support the catalytic metals the applicability is widened and the catalyst removal is easier. [ABSTRACT FROM AUTHOR]

Bovine bones heated to 1100 °C under air atmosphere were studied using transmission electron microscopy. During heating, bone bioapatite was transformed into hydroxylapatite (HAp). Energy-dispersive spectroscopy did not indicate the presence of A-type CO3substitution, it showed a near-ideal Ca/P ratio of 1.67 during heating. In the present study, the structure of the formed HAp was determined using automated electron diffraction tomography, a 3D electron diffraction method, space group P63a= 9.42 Å and c= 6.89 Å at 700 °C. The position of the OH hydrogen sitting in the channel position was determined, confirming the lack of the mirror plane perpendicular to the c-axis in the P63/mspace group.

A catalyst nanocomposite was synthesized based on zeolite supported nitrogen-doped carbon nanotubes (N-CNT) decorated with palladium nanoparticles. Zeolite beads impregnated with nickel nitrate solution were used as CCVD catalyst support during the synthesis of N-CNT. Then the zeolite supported N-CNT was decorated with palladium nanoparticles and the final nanocomposite was tested in nitrobenzene hydrogenation. The structure of the nanocomposite was characterized by SEM. The surface of the zeolite beads is extensively covered by N-CNT. The particle size distribution of the palladium nanoparticles on the surface of N-CNT is relatively homogenous (< 7 nm). The catalytic activity of the nanocomposite was the highest at 10 bar and 323 K while the achieved nitrobenzene/aniline conversion was 99.9% after 4 h of hydrogenation.

26 blueschist Neolithic polished stone tools coming from archaeological sites in Borsod-Abaúj-Zemplén County (NE Hungary) were archaeometrically analysed. All items were described and documented macroscopically and magnetic susceptibility was measured on each tool. Non-destructive XRD analyses were made on all implements to separate blueschists from other metamorphic rocks, because this technique can make a difference between the diagnostic sodic amphiboles and other amphiboles, which was confirmed by EDS/SEM in each case. Electron microprobe analyses were carried out on polished sections and selected intact axes by using “original-surface” method. Non-destructive Prompt Gamma Activation Analysis (PGAA) was performed on selected pieces. Blueschist polished stone tools were classified into five groups based on their mineral components and metamorphic evolution. Mineral chemistry analyses suggest that blueschists suffered a polyphase metamorphism. Our data were compared to the nearest blueschist outcrop in the Meliata Unit (Slovakia); it is supposed that the source area of the blueschist implements is the Meliata Unit and/or the blueschist pebbles from Cretaceous conglomerate in the Pieniny Klippen Belt.

Bamboo-shaped carbon nanotubes (BCNT) were prepared from three different amines on supported iron (Fe) and nickel (Ni) catalysts by catalytic chemical vapor deposition. The main factors governing product morphology and defect site density were identified. Post-synthetic oxidative functionalization was used to add carboxyl groups to the nanotubes, and then platinum (Pt) nanoparticles were deposited on the surface by the in situ reduction of a platinum salt. The average Pt nanoparticle diameter was found to be affected by the extent of surface functionalization. The catalytic performance of the synthesized Pt/BCNT samples were examined in the hydrogenation of 1-butene, in order to show that the catalytic activity of the bamboo like carbon nanotube supported Pt catalyst is similar to the conventional Pt catalysts in heterogeneous catalytic hydrogenation. The best overall performance was achieved when the bamboo-shaped nanotube support was synthesized on 5 wt% Fe/Al(OH)3catalyst from triethylamine and decorated with 5 wt% platinum nanoparticles.

In the traditional heavy-clay industry, compounds are usually prepared by the addition of organic waste material. These additives originate mainly from the wood, food or paper industries. The purpose of this study is to present the results of the examination of friction contact between the wall of the forming die and the clay compounds containing organic additives. Saw dust and ground sunflower seed shell were mixed to clay in 0 wt%, 3 wt% and 5 wt%. The water content of compounds was also varied. The clay and the additives were described by morphology, XRD, bulk density and equivalent diameter. Friction tests were carried out on a special tribometer up to plastic deformation of the sample. The coefficient of friction decreased when normal stress was increased for all the ten compounds. Average results showed that the tendency of change in the value of the coefficient of friction could be divided into three sections: a decreasing, a quasi constant and a shearing section. It follows from this that the coefficient of friction can be characterized with a number only inside the quasi constant section, i.e. between two definable normal stress values. Averaged coefficient of friction was between 0.17 and 0.21 for saw dust and between 0.19 and 0.21 for the compounds with ground sunflower seed shell.

A plastic brick clay with high clay mineral content was selected and the effects of different extruder heads on the main physical properties of the extruded products were investigated. The raw material was processed by a laboratory extruder after homogenization and wetting. Extruder heads with conical and special (spherical and torus) inner shape were applied to form and produce the green products which were examined after drying and firing. The rotation of the extruder screw was also varied between 15-55 1/min. Applying optical microscopy and SEM, the structure of the green products was analyzed. In addition to the physical properties of the products, the pressure caused by the extruder heads was determined by theoretical calculation and measurement. The results revealed that the physical properties of the products could be changed only by changing the shaping die geometry when the product size and production method remained unchanged. Maximal compressive strength of fired brick products (35.45 MPa) was obtained in case of the spherical head while the use of torus head caused some 5% decrease in the power consumption of the extruder. The density of fired products decreased and water adsorption increased when the rotation speed of the extruder screw was increased. The measurements confirmed the theoretical order of the applied extruder heads in terms of capability of pressure generation.

Experimental work was conducted on illite-chlorite and kaolinite-carbonate rich clays to investigate effects of pore forming additive materials. Three types of additives were applied: vegetal materials like sawdust, sunflower seeds hull and rice husks; lignite, as high organic content mineral material; fuel-grade coke, as synthetic additive. Raw materials were characterized regarding their composition, thermal behavior, microstructure and chemical composition. Expansion of extruded samples was detected after pressing release. Correlations were determined between the type and cellulose content of vegetal materials and expansion caused. The mineral and synthetic additive does not produce expansion, but lowers the working moisture needed.

Vegetal materials are generated in high amounts and are applied as additives in clay bricks since ancient times. They have a certain heat contribution to the firing process. As revealed by X-ray Powder Diffraction, main component of vegetal waste materials is cellulose. Thermal and Evolved Gas Analysis revealed the combustion process in its details. Mixtures of clay and vegetal additives prepare for test bodies were analyzed by Thermal Analysis. The thermal effects were quantified by Differential Thermal Analysis and correlated with Thermogravimetry and Derivative Thermogravimetry.

We consider nonlinear elliptic Neumann problems driven by the p-Laplacian. Using variational techniques together with Morse theory (in particular, critical groups and the Poincaré-Hopf formula), we prove some multiplicity results: either three or four distinct nontrivial solutions are guaranteed, depending on the geometry and smoothness of the nonlinear term.

In this paper we study the multiplicity of solutions of the quasilinear elliptic system \begin{equation} \left. \begin{aligned} -\Delta_pu&=\lambda F_u(x,u,v)&&\text{in }\varOmega, \\ -\Delta_qv&=\lambda F_v(x,u,v)&&\text{in }\varOmega, \\ u=v&=0&&\text{on }\partial\varOmega, \end{aligned} \right\} \end{equation} \tag{S$_\lambda$} where $\varOmega$ is a strip-like domain and $\lambda>0$ is a parameter. Under some growth conditions on $F$, we guarantee the existence of an open interval $\varLambda\subset(0,\infty)$ such that for every $\lambda\in\varLambda$, the system (S$_\lambda$) has at least two distinct, non-trivial solutions. The proof is based on an abstract critical-point result of Ricceri and on the principle of symmetric criticality.

Cobalt, copper and nickel ferrite spinel nanoparticles have been synthesized by using a combination of sonochemical treatment and combustion. The magnetic nanoparticles have been used as supports to prepare ∼4 wt% palladium catalysts. The ferrites were dispersed in an ethanolic solution of Pd(II) nitrate by ultrasonication. The palladium ions reduced to metallic Pd nanoparticles, which then attached to the surface of the different metal oxide supports. Thus, three different catalysts (Pd/CoFe2O4, Pd/CuFe2O4, Pd/NiFe2O4) were made and tested in the hydrogenation of 2,4-dinitrotoluene (DNT). A possible reaction mechanism including the detected species has been envisaged based on the results. The highest 2,4-diaminotoluene (TDA) yield (99 n/n%) has been achieved by using the Pd/NiFe2O4catalyst. Furthermore, the TDA yield was also reasonable (84.2 n/n%) when the Pd/CoFe2O4catalyst was used. In this case, complete and easy recovery of the catalyst from the reaction medium is ensured, as the ferrite support is fully magnetic. Thus, the catalyst is very well suited to apply in the hydrogenation of DNT or other aromatic nitro compounds.