Prediction of hardness and electrical properties in ZrB2 particle reinforced metal matrix composites using artificial neural network

In the present study, the hardness and electrical properties of copper based composite prepared by hot pressing of mechanically alloyed powders were predicted using Artificial Neural Network (ANN) approach. Milling time (t, h), particles size of mechanically alloyed powders (d, nm), dislocation density (Ï, m-2) and compressive yield stress (σ0.2, MPa) were used as inputs. The ANN model was developed using general regression neural network (GRNN) architecture. Cu-based composites reinforced with micro and nano ZrB2 particles were consolidated via powder metallurgy processing by combining mechanical alloying and hot pressing. Analysis of the obtained results concerning hardness and electrical properties of the Cu-7 vol.% ZrB2 alloy showed that the distribution of micro and nano ZrB2 particles and the presence of agglomerates in the Cu matrix directly depend on the milling time. Also, the results show a strong influence of the milling time on hardness and electrical properties of Cu-7 vol.% ZrB2 alloy. Addition of ZrB2 particles decreases electrical conductivity of copper, but despite this fact Cu-7 vol.% ZrB2 alloy can be marked as highly conductive alloy (samples made of mechanically alloyed powders milled longer than 20 h). Experimental results of the samples have shown a consistency with the predicted results of ANN.  http://dx.doi.org/10.5937/metmateng1404255

Understanding plasma spraying process and characteristics of DC-arc plasma gun (PJ-100)

The thermal spray processes are a group of coating processes used to apply metallic or non-metallic coatings. In these processes energy sources are used to heat the coating material (in the form of powder, wire, or rod form) to a molten or semi-molten state and accelerated towards a prepared surface by either carrier gases or atomization jets. In plasma spraying process, the spraying material is generally in the form of powder and requires a carrier gas to feed the powder into the plasma jet, which is passing between the hot cathode and the cylindrical nozzle-shaped anode. The design of DC plasma gun (PJ - 100) is designed and manufactured in Serbia. Plasma spaying process, the powder injection with the heat, momentum and mass transfers between particles and plasma jet, and the latest developments related to the production of DC plasma gun are described in this article

The Effect of Ball-Powder Ratio on The Mechanical and Structural Properties of CuZrB Composite Materials Fabricated by Powder Metallurgy

Copper matrix composites exhibit excellent mechanical and thermal properties. The composite consists of copper (Cu), zirconium (Zr), and boron (B) and is produced using the powder metallurgy technique. The high-energy ball milling was applied for mechanical alloying of the Cu-Zr-B powder mixture to achieve the desired ratio for obtaining a copper matrix reinforced with ZrB2 ceramic particles. The milling times of 10 and 40 hours for two different ball-to-powder ratios are investigated for a powder mixture with a composition of Cu-2.71Zr-2.27B (wt.%). XRD and SEM analyses were employed to determine structural and morphological changes in the mechanically alloyed powder mixture. Investigation of the morphological parameters shows that with prolonged milling, the shape of mixed particles becomes more uniform, while their structural parameters have been drastically changed. It is determined that during high-energy ball milling of the Cu-2.71Zr-2.27B (wt.%), the size of the copper powder decreases as the mechanical alloying increases for both ball-powder ratios. Dislocation densities reach their maximum value at around 30 hours of mechanical alloying for both ball-powder ratios, with dislocation density being higher for the 1:15 ratio, after which they decrease owing to the recrystallization of the copper matrix. XRD analysis shows no presence of ZrB2 reinforcement particles or oxides during milling

Hemijske modifikacije β-laktoglobulina hinonima

The avarone/avarol quinone/hydroquinone couple. as well as their derivatives show considerable antitumor activity. In this work, covalent modifications of beta-lactogglobulin. isolated from cow milk by avarone, its model compound 2-tert-butyl-1,4-benzoquinone. and several of their alkylthio derivatives were studied. The techniques applied for as-saying the modifications were: UV/VIS spectrophotometry, SDS PAGE and isoelectrofocusing. The results of the SDS PAGE suggest that polymerisation of the protein occurs. The shift of the pI of the protein upon modification toward lower values indicates that lysine amino groups are the principal site of die reaction of beta-lactoglobulin with the quinones.Hinonsko/hidrohinonski par avaron/avarol i njihovi derivati pokazuju značajnu antitumorsku aktivnost. U ovom radu proučavane su kovalentne modifikacije β-laktoglobulina, izolovanog iz kravljeg mleka, avaronom, njegovim model-jedinjenjem 2-tert-butil-1,4-benzohinonom i njihovim alkiltio-derivatima. Za ispitivanje modifikacija korišćene su UV/VIS spektrofotometrija, SDS PAGE i izoelektrofokusiranje. Rezultat SDS PAGE ukazuje da se protein polimerizuje. Pomeranje pI vrednosti proteina nakon modifikacije ka nižim vrednostima pokazuje da su amino grupe lizina glavna mesta reakcije β-laktoglobulina sa hinonima

Data analytics approach to predict the hardness of copper matrix composites

Copper matrix composite materials have exhibited a high potential in applications where excellent conductivity and mechanical properties are required. In this study, the machine learning models have been applied to predict the hardness of the copper matrix composite materials (CuMCs) produced via the powder metallurgy technique. Six different machine learning regression models were employed. The observed CuMCs were reinforced with two different volume fractions (2 vol.% and 7vol.%) of ZrB2 particles. Based on experimental work, we extracted the independent variables (features) like the milling time (MT, Hours), dislocation density (DD, m-2), average particle size (PS, μm), density (ρ, g/cm3), and yield stress (σ, MPa) while the Vickers hardness (MPa) was used as the dependent variable. Feature selection was performed by calculation the Pearson correlation coefficient (PCC) between the independent and dependent variables. The predictive accuracy higher than 80% was achieved for Cu-7vol.% ZrB2 and lower for the Cu-2vol.% ZrB2

The effect of synthesis of the starting powders on the properties of Cu-Ti-TiB2 alloy obtained by laser melting

A comparison was made between layer-by-layer laser melting (LM) of two types of feedstock powders: (1) elemental powder blend and (2) mechanically alloyed powder. LM was done by Nd:YAG laser at 1064 nm (max. average power 100 W) in argon ambience. Samples synthesized were Cu-Ti-TiB2 rectangular tracks (20x6x1 mm), and input parameters of the process: powder layer thickness 100-250 µm, hatch spacing 1 mm, pulse length 4 ms, energy 4 J, pulse repetition rate 20 Hz. Part of the samples was heat-treated in argon at 900 °C, 10 h. Structural characterization of the samples was done using light microscope and scanning electron microscope (SEM). Chemical analysis of the as-obtained laser melted samples was done by inductively coupled plasma-atomic emission spectrometry (ICP-AES). It was established that the microstructure of LM samples was comprised of Cu-Ti and Cu-B solid regions, and in situ formed microparticles of primary TiB2. Only after high-temperature thermal treatment has the secondary TiB2 occurred. Tensile tests showed much higher strengthening in heat-treated samples with mechanically alloyed powder as starting material, where the formation of secondary TiB2 nanoparticles was considerable

Innovative processing routes in manufacturing of metal matrix composite materials

Metal matrix composites (MMCs) belong to a group of modern materials owing to their excellent technological, mechanical, and physical properties such as excellent wear and corrosion resistance, high electrical and thermal conductivity, improved strength and hardness. Final properties of MMCs are affected equally by all steps of its manufacturing process. It is shown that by using adequate process parameters to obtain starting materials (reaching the specific size, shape, and reactivity) the control of volume fraction and distribution of reinforcements within the matrix can be achieved. For this purpose, mechanical alloying has been appointed as a good approach. MMCs can be produced using powder metallurgy, ingot metallurgy, and additive manufacturing techniques. Combining high-energy ball milling with these techniques enables the design of an innovative processing route for MMCs manufacturing. Mechanochemical process (achieved using high-energy ball milling) was employed in three manufacturing procedures: hot pressing, compocasting, and laser melting/sintering for obtaining of the suitable powder. These production routes for MMCs manufacturing were the subject of this work. The aim of MMCs design is to establish an optimal combination of production techniques merged into the cost-effective fabrication route for obtaining MMCs with required properties

Microwave Assisted Esterification of Aryl/Alkyl Acids Catalyzed by N-Fluorobenzenesulfonimide

The susceptibility of the carbonyl group towards nucleophilic attack affords the construction of various organic compounds. Thus, investigations of carbonyl activation applying greener methodologies are highly important. In the present work, among the investigated N-halo compounds, N-fluorobenzenesulfonimide (NFSi) has been found as an efficient and selective catalyst in the reaction of direct esterification of aryl and alkyl carboxylic acids supported by microwave (MW) irradiation. The comprehensive esterification of different benzoic acids and mono-, di-and tri-carboxy alkyl derivatives was performed, whereby significant reaction time reductions were achieved. The presented method used NFSi as an easily manipulatable, non-metal, water-and air-tolerant catalyst, allowing simple synthetic and isolation procedures and energy saving, compared to conventional methodologies. Importantly, in contrast to esterification under thermal conditions, where N-halo compounds behave as pre-catalysts, in the MW-supported protocol, a distinct reaction mechanism has been proposed that assumes NFSi as a sustainable catalyst. Moreover, a scale-up of the industrially important derivative was performed

Tečni stajnjak kao potencijal stočarskih farmi u sistemu kogeneracije

Biomass is specific energetic resource, because of a possibility of getting heat, electricity, fuel etc. This kind of energy contribute to higher labor employment, reduce emission of SO2, CO2, NO2, comparing to other fossil fuels. In order to increase energetic efficiency of its production, optimal technology and adequate technical solutions for biomass using, are determined. Because of extensive production in our country, processes like gathering, treatment, preparing and using of biomass waste are not in common use. This paper examines the state of the fattening farm's biomass as potential in cogeneration system, the same of renewable energy sources technologies. There are some experiences in countries with undeveloped livestock production, that redirected production process to better use of secondary products can significantly improve economic effects.Biomasa uopšte, a tečni stajnjak posebno, predstavlja raznorodni energetski izvor, jer se od njega može dobiti toplota, električna struja, gorivo za pogon i dr. Energija iz tečnog stajnjaka doprinosi većoj zaštiti životne sredine jer se, smanjuju emisije sumpor-dioksida, ugljen-dioksida i azot-dioksida, u odnosu na sagorevanje fosilnih goriva. Određena je optimalna tehnologija i tehnička rešenja korišćenja biomase iz stočarske proizvodnje radi poboljšanja energetske efikasnosti proizvodnje. Postupci prikupljanja obrade, pripreme, kao i korišćenja biomase, u našim uslovima nisu naišli na širu primenu, zbog ekstenzivnog načina proizvodnje i nedomaćinskog načina poslovanja. U radu je dato stanje biomase na stočarskim farmama, kao potencijala u sistemu kogeneracije, jednoj od tehnologija korišćenja obnovljivih izvora energije. Ekonomski efekti u zemljama sa manje razvijenom stočarskom proizvodnjom ukazuju da se tom pitanju mora posvetiti adekvatna pažnja i pravilno usmeriti proizvodnja, koja sa svojim sekundarnim proizvodima može doprineti pozitivnijem rezultatu

Ostvareni obim korišćenja sredstava poljoprivredne tehnike kao element za donošenje odluke pri organizovanju mehanizovanih procesa na poljoprivrednim gazdinstvima

The paper presents a method to be based on known economic laws made the decision making that provides increased levels of economic efficiency of use of agricultural mechanization. It is one of the basic tasks necessary precondition for achieving competitiveness in the market of agricultural products, as well as a necessary part of the transformation of rural economies in order to survive.U radu je prikazan metod kako se na bazi poznatih ekonomskih zakonitosti vrši donošenje odluke koja obezbeđuje povećanje nivoa ekonomske efektivnosti korišćenja poljoprivredne tehnike. To je jedan od osnovnih zadataka i neophodan preduslov za dostizanje konkurentnosti na tržištu poljoprivrednih proizvoda, kao i neophodan segment transformacije seoskih gazdinstava u cilju njihovog opstanka