Search

Almost a third of Earth’s freshwater resources are used by municipalities, agriculture and industries and therefore very large quantities of wastewater are generated and discharged into surface water or groundwater. If discharged inadequately and without previous treatment, wastewater can cause chemical pollution, affect aquatic life as well as human health and have a negative impact on the environment. An emerging technology for wastewater treatment is the membrane separation process due to the low cost, the use of ambient temperature, the low energy consumption compared to other traditional techniques, and the high selectivity of different separation mechanisms with compact design. In this study, ultrafiltration (UF) technique was investigated to treat wastewater with different organic loads. The effects of the stirring and a three-dimensional (3D) printed spacer, integrated into the UF cell were analyzed on the permeate fluxes, membrane rejections of turbidity, conductivity and chemical oxygen demand (COD).

This study investigates the enhancement of dairy wastewater treatment using chemical and physical pre-treatments coupled with membrane separation techniques to reduce membrane fouling. Two mathematical models, namely the Hermia and resistance-in-series module, were utilized to comprehend the mechanisms of ultrafiltration (UF) membrane fouling. The predominant fouling mechanism was identified by fitting experimental data into four models. The study calculated and compared permeate flux, membrane rejection, and membrane reversible and irreversible resistance values. The gas formation was also evaluated as a post-treatment. The results showed that the pre-treatments improved UF efficiency for flux, retention, and resistance values compared to the control. Chemical pre-treatment was identified as the most effective approach to improve filtration efficiency. Physical treatments after microfiltration (MF) and UF showed better fluxes, retention, and resistance results than ultrasonic pre-treatment followed by UF. The efficacy of a three-dimensionally printed (3DP) turbulence promoter was also examined to mitigate membrane fouling. The integration of the 3DP turbulence promoter enhanced hydrodynamic conditions and increased the shear rate on the membrane surface, shortening filtration time and increasing permeate flux values. This study provides valuable insights into optimizing dairy wastewater treatment and membrane separation techniques, which can have significant implications for sustainable water resource management. The present outcomes clearly recommend the application of hybrid pre-, main- and post-treatments coupled with module-integrated turbulence promoters in dairy wastewater ultrafiltration membrane modules to increase membrane separation efficiencies.

The press and sinter method remains the standard among powder metallurgy processes for powdered stainless-steel materials. It delivers low cost, low oxidation rate, and adequate corrosion resistance. Furthermore, 17-4PH is a martensitic stainless-steel that is commonly used for high-strength and medium-ductility stainless steel parts. However, a few studies have investigated the press and sinter method for producing 17-4PH parts. This shortage is due to the high hardness (low compressibility) of 17-4PH powder. Thus, the main objective of this study is to evaluate the press and sinter method in terms of the manufacturing process, the influencing factors, and the theoretical basis of press and sinter methods in conjunction with metal injection molding technology for the production of 17-4PH parts. First, the literature and monographs are examined and summarized to cover the previous results, research progress, development trends, and applications of press and sinter method 17-4PH parts. Following the theoretical analysis, the practical investigation was conducted by producing parts with cold pressing from 800 to 1600 MPa, followed by sintering: the sintering temperature was 1200 °C for one hour under a protective vacuum atmosphere. ImageJ analysis was performed to measure the sinter density. The results showed an increase in relative sinter density from 84.43% to 96.43% for 800 and 1600 MPa, respectively, while the earlier results reached 93.47%. Overall, the press and sinter method enables the production of high-hardness 17-4PH parts with a high density, without using additives like lubricants, wax, or alloying elements.

In the present study, an electroless nickel (EN) plating method is applied for the coating of silicon carbide (SiC) particles. The particles of SiC(Ni) were added to the Sn–3.0Ag–0.5Cu matrix for the production of SAC305/SiC(Ni) composite by the powder metallurgy route. SAC305/xSi(Ni) composite was prepared by a planetary ball milling of the starting powder, followed by compacting and sintering. Nickel-coated silicon carbide particles and the lead-free solder matrix react together, forming different phases during sintering at temperature 200°C for 3 h. The microstructure, mechanical (compressive strength, microhardness, wettability, and porosity) and physical properties (density) of lead-free solder composite SAC305/SiC(Ni) were studied. The current research shows the successful application of electroless nickel (EN) plating method, and how nickel-coated SiC particles subsequently improve the mechanical properties and microstructure of lead-free solder.

In this paper, the effect of soldering technique and thermal shock test were investigated on SAC 305 solder joints, produced by 2 different solder methods, which are the most common solder material...

Good wetting, strong bonding and low electrical resistance are the most important properties of the solder in microelectronic packaging. Aim of this study was to improve the mechanical and wetting properties of commercially available lead-free solders. Different type and sized ceramic particles treated with different surface modification methods were added to lead-free SAC305 solder paste to form composites. The reinforcement particles were subjected to various surface modification processes. We made reflow soldering in the same way as in industrial application. Solder joints were formed between a novel designed test PCB board and microelectronic components. The mechanical properties of the composite joint were tested by microhardness measurement and shear test, while the microstructure and the IML layer were examined by scanning electron microscope.

The Sn-3.0Ag-0.5Cu solder alloy is a prominent candidate for the Pb-free solder, and SAC305 solder is generally employed in today’s electronic enterprise. In this study, the formation of intermetallic compounds (Cu6Sn5 and Ag3Sn) at the interface, average neighbour’s particle distance, and the morphological mosaic are examined by the addition of SiC and nickel-coated silicon carbide reinforcements within Sn-3.0Ag-0.5Cu solder. Results revealed that the addition of SiC and SiC(Ni) particles are associated with a small change to the average neighbor’s particle distance and a decrease of clustering rate to a certain limit of the Sn-3.0Ag-0.5Cu solder composites. Moreover, the development of the Cu6Sn5 and the structure of the Ag3Sn are improved with the addition of SiC and Ni coated SiC.

The Sn–Ag–Cu (SAC) solders with low Ag or Cu content have been identified as promising candidates to replace the traditional Sn–Pb solder. In this study, an extensive discussion was presented on two major area of mechanical properties and microstructural investigation of SAC305 and SAC405. In this chapter, we study the composition, mechanical properties of SAC solder alloys and microstructure were examined by optical microscope and SEM and mechanical properties such as tensile tests, hardness test and density test of the lead solder alloys were explored. SAC305 and SAC405 alloys with different Ag content and constant Cu content under investigation and compare the value of SAC305 and SAC405. From this investigation, it was reported that tensile strength is increased, with an increase of Ag content and hardness and density were also increases in the same manner.

The Lead-free solders (SAC) with low Ag content have been identified as crucial solder to replace the traditional Sn–Pb solder. The main discussion was presented in two major area of microstructural investigation and mechanical properties of SAC305 and SAC405. Composition and microstructure of SAC solder alloys were investigated by an optical microscope and SEM (Scanning Electron Microscopy). Mechanical properties such as tensile tests and hardness test of the lead-free solder alloys have been tested in this research. Different Ag content and constant Cu content of lead-free solder has been considered in this investigation and compare the mechanical properties of SAC305 and SAC405 solders. From this investigation, tensile strength and hardness have been increased with increased of Ag content.

This work represents an interesting development in the detection and interpretation of crack evolution in through hole technology (THT) solder joints, which based on the development of general and common method. Serial sectioning is a useful method because it overcomes the problems associated with traditional two-dimensional metallographic techniques by providing information about (micro)structures in three-dimensions.In our work, serials sectioning with reconstruction method was utilized to visualize the 3D nature of cracks in through hole solder joint. Accurate quantitive analysis of the cracks, such as crack length, position and extension are presented with a help of the developed method: newly defined parameter and serial-cross sectioning method.

W and Cu can be found in separate phases in the W-Cu composites since these elements do not dissolve in each other neither in liquid nor in solid phase, but with mechanical alloying it is possible to produce nonequilibrium W-Cu alloys In this work the nanostructured W-Cu composites were produced by planetary ball milling. The nanostructured W-Cu powder was sintered on 900 °C and 950 °C with 50 MPa pressure applied. The meso- and microstructure of the W-Cu powder and the sintered samples, were investigated with SEM, TEM and XRD. After 50 h of milling, the size of the W crystallites was ~10 nm, and about 10% of the Cu was solved in the W matrix, producing a W-Cu nonequilibrium alloy layer on the surface of W nano crystallites. During sintering, the Cu atoms left from the W surface to the Cu phases, so the W-Cu nonequilibrium alloy layer disappeared. The size of the W crystallites – after 60 min of sintering on 950 °C - was around 170 nm, and the relative density was ~90% of the theoretical density.

The current investigation was conducted to understand the effect of 1wt. % silicon carbide (SiC) in the Sn–3.5Ag–0.5Cu (SAC305) lead-free solder alloy which was produced by the powder metallurgy method. A systematic investigation of the microstructure of the solidified composite solder along with its wetting behavior was carried out at different reflow temperatures (230°C–290°C). From microstructure investigation, it was clear that SiC ceramic particles influence the development of IMCs at the Cu–Sn interface and refine microstructure in the bulk solder region. Micro-cracks were detected at Cu/SAC interface and also in the Cu6Sn5 layer. This is due to the development of extremely (brittle) intermetallic layer and ductile nature of Sn–3.0Ag–0.5Cu solder. The intermetallic layer thickness increased substantially with the increase of reflow temperatures (230°C–290°C). A uniform distribution of SiC, Ag3Sn, and Cu6Sn5 IMCs were found in the bulk b-Sn matrix. The result shows that the SiC particles promote the extra nucleation sites for the development of b-Sn phase and IMCs in the solidified structure. In addition to this, SiC particles, b-Sn dendrites and IMCs can prevent dislocation slippage which helps in attaining a strong solder joint due to strong strengthening effect. The results showed that the spread ratio, spread factor, and the relative spread area (RSA) increased while the equilibrium contact angle decreased with an increase inreflowtemperature. This can be attributed to the strong adsorption effect and high surface free energy of the SiC particles.

The Sn-3.0Ag-0.5Cu (SAC305) composite solder reinforced micro-sized silicon carbide and nickel-coated silicon carbide (Ni-SiC) particles were produced by a high-energy ball milling process. SiC and Ni-SiC were homogeneously mixed into SAC305 lead-free solder alloy with distinctive (0.5, 1.0, and 1.5 wt.%) percent weight, through a powder metallurgy path. The growth of nickel on ceramic SiC (1-3 μm) particles was investigated by the electroless nickel (EN) method. The relative contact perimeter (RCP) and the wettability of SAC305 composite solder were investigated with the an image analysis software. The data from image analysis software shows that the relative contact perimeter, as well as the wettability of lead-free composite solders, were significantly improved.

In lead-free reflow soldering, the presence of voids should be taken into account. For this reason, the effect of the applied heating profiles was examined via the characterization of voids in galvanic and immersion Sn coatings. According to EU Directive 2002/95/EC, the screening of Pb element of reflow soldering (i.e. of electrical and electronic equipment) is necessary; and the practical implementation of this measurement is largely affected by the characteristics of the solder (i.e. the presence of voids and the inhomogeneity of the solder). Comparing the results of the above two coating methods, it was found that by chemical coating more voids were formed and the detected lead content was higher than for galvanic Sn. The standard deviation of Ag and Cu concentrations was mainly influenced by the appearance of large compounds in the second case, while with chemical coating, no large compounds were formed due to the elevated number of voids.

Nano hydroxyapatite (nHA)–zirconia (ZrO2) composites have been produced by spark plasma sintering (SPS). During the SPS process low temperatures (600–950 °C) and short dwelling time (5 min) have been applied to avoid the decomposition of nHA as well as the reaction between nHA and ZrO2. The grain size of the sintered composites was between 200 and 1000 nm. Carbon diffusion was induced from the graphite die and layered composite structure was formed. These observations might be related to the spark plasma sintering side effects. The microstructure and mechanical properties of high hydroxyapatite content zirconia composites have been found to be influenced and strongly correlated with the specialties of SPS method.

The European Union and Japan initiated the issue of RoHS, the directive about the restriction of hazardous substances, which prohibits certain hazardous substances in electronic equipment - including lead - application. Due to the directive the use of lead free solder alloys is spreaded, however the Pb in the form of contamination may be appear under technological process. The lead impurity has significant effect on microstrucutre and lifetime so it is necessary to carry out detailed examinations. In this paper the study of intermetallic compounds in six-element, Pb impured, thermal cycles test-subjected, Sn-Ag-Cu (SAC) solder alloy is demonstrated

Hydroxyapatite, (Ca10(PO4)6(OH)2is chemically similar to the mineral component of bones and teeth. HAp is among of the few materials that are classified as bioactive, meaning that it will support bone ingrowth and osseointegration when used in orthopaedic, dental and maxillofacial applications. Hydroxyapatite may be employed in forms such as powders, porous blocks and hybrid composites to fill bone defects or voids. These may arise when large sections of bone have had to be removed or when bone augmentations are required (e.g. dental applications). In this work, nanohydroxyapatite (nanoHAp) was successfully produced by using recycled eggshell and phosphoric acid by mechanochemical activation method (e.g. attrition milling). nanoHAp bioactivity was evaluated in animal (rabbit) models. Sixteen 4-month-old New Zealand white rabbits with an average weight of 2.8kg were used in experiments. After bilateral parietal bony defects formation (diameter: 8.0mm), nanoHAp was grafted. The control was unfilled defect. The bone regeneration was evaluated by micro-computerized tomograms (μCT) and histomorphometric analysis at 4 and 8 weeks. In conclusion, nanoHAp from eggshell showed much more bone formation compared to unfilled control group in both μCT analysis and histomorphometric analysis. Considering that the eggshell is easily available and cheap, nanoHAp from the eggshell can be good calcium source in tissue engineering.

This research explores the use of a variety of carbon nanostructures as reinforcing agents for Si3N4 matrix composites. We have chosen highly promising families of carbon materials: multiwall, singlewall carbon nanotubes (MWCNTs, SWCNTs), graphene, carbon black nanograins and graphite micrograins for use as fillers. These materials were dispersed with a concentration of 3 wt% in silicon nitride matrices. A high efficiency attritor mill has also been used for effective dispersion of second phases in the matrix. In the present work the development of sintering processes (hot isostatic pressing (HIP) and spark plasma sintering (SPS)) has been performed to consolidate and tailor the microstructure of Carbon nanotube (CNT)-reinforced silicon nitride-based ceramic composites. The silicon nitride nanocomposite systems retained the mechanical robustness of the original systems. Elastic modulus measurements and micro-indentation investigations of the hardness and fracture toughness have been performed as well as scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction in order to characterize the composites produced by the two sintering methods.

Hydroxyapatite (HAp) was successfully produced from recycled eggshell, seashell and phosphoric acid by using two different type of milling method (attrition milling and ball milling). According to the analysis, the attrition milling resulted nanosize HAp even after milling, while the ball milling process provided HAp only after a 400oC, 2 h long heat treatment. The grain size in both cases were approximately preserved during the heat treatment. The effect of temperature on stoichiometry, morphology and crystallinity of HAp powders were investigated. The structures of the HAp were characterized by X-ray diffraction and Scanning Electron Microsopy.

Hydroxyapatite (HAP) is the main inorganic component of mammal bone and teeth. It is one of the few bioactive materials, which helps cell growing. The objective of this study was to fabricate hydroxyapatite-biopolimer nanofiber mats. To achieve this goal, two different suspensions were used. Approximately 1 μm diameter size fibers with large HAP agglomerates were fabricated using acetone and acetic acid. Fibers with a larger diameter size and homogenous distributed HAP particles were produced applying acetone and isopropanol. During the experiment the effect of the processing parameters: applied voltage, diameter of needle, the distance of the needle tip and the collector, flow rate was analyzed.

One of the methods of melt-treatment of Al-Si alloys is the modification that plays a very significant role in the development of (mechanical) properties of finished product. There are a lot of well-known processes for the investigation of effectiveness of modification but an objective, exact result cannot be obtained in each case by using these methods. The method suitable for the classifi-cation of modification worked out by us was developed by integrating two methods namely the comparison by means of etalon-images and the integration of measurement of morphological pa-rameters. This method is relatively simple, does not demand lots of measurements and gives reliable results.

Hydroxyapatite (HAp) was successfully produced from recycled eggshell, seashell and phosphoric acid. The phases obtained depended on the ratio of calcined eggshell/ seashell to phosphoric acid, the calcination temperature and the mechanochemical activation method (ball milling or attrition milling). The HAp structures were characterized by X-ray diffraction, scanning electron microsopy and infrared spectroscopy. Attrition milling was more effective than ball milling, yielding nanosize, homogenous and pure Hap.

Hydroxyapatite (HAp) was successfully produced by using recycled eggshell. The observed phases of the synthesised materials were dependent on the mechanochemical activation method (ball milling and attrition milling). The structures of the HAp were characterized by X-ray diffraction, scanning electron microscopy and infrared spectroscopy. Attrition milling proved to be more efficient than ball milling, as resulted nanosize, homogenous HAp even after milling.

The A356 alloy, which consists of 100-200 ppm modifier, namely strontium was examined. The samples were solidified unidirectionally, and each sample had a pair which was solidified in a rotating magnetic field. The microstructure of the samples: morphology and the fraction of eutectic silicon was studied. The morphology of eutectic Si was very different in the samples - the samples solidified at different movement velocities – so it was necessary to determine the quantity of strontium. Magnetic stirring changes both the strontium content and the extent of modification. This paper describes the investigation methods and the effects of strontium modification.

The effects of various materials parameters on hot deformability f of AISI M2 high speed steel are studied in a complex way. These studies revealed beside other parameters (e.g. carbides) a strong correlation between some impurities (S, Sn) and f, determined by hot deformability tests. The correlation between f and the P content prooved to be weaker. The paper is devoted to impurity effects. The composition and impurities of the samples and their isolated carbide phases have been determined by chemical analysis. In situ AES fractography and SEM were applied to study the fracture surfaces. The main results are: The S concentration of the fracture surfaces exhibits a correlation with the bulk content. Strong enrichment of S and P within a thin (1–3 nm) surface layer was revealed by AES in-depth profiling, showing also carbide phases. In the temperature range -150°C — +250°C no grain boundary fracture was observed, fracture was ductile and void type. The fracture path is determined by carbides, being the sites of S and P enrichment. Es wurde die Wirkung verschiedener Faktoren auf die Warmverformbarkeit f von AISI M2-Schnellstahl (TGL 7571-X82WMo6.5) mit interdisziplinaren Methoden untersucht. Die Torsionsprufungen wiesen neben anderen Faktoren (z. B. Carbide) eine starke Korrelation zwischen einigen Verunreinigungen und f auf. f wurde durch Warmtorsionsversuche bestimmt. Dagegen zeigte f eine schwachere Korrelation mit dem P-Gehalt. Die Mitteilung befast sich mit der Wirkung von Verunreinigungen. Die Zusammensetzung der Proben und isolierten Carbid-Phasen wurde mittels chemischer Analyse bestimmt. Die Bruchoberflachen wurden durch in-situ AES Analyse und SEM gepruft. Die wichtigsten Ergebnisse zusammenfassend: Die S Konzentration an den Bruchoberflachen zeigt eine Korrelation mit den verschiedenen Proben. Eine starke Anreicherung von S und P in einer 1–3 nm dieken Oberflachen-Schicht wurde mit Hilfe der AES-Ionen-Tiefenprofil-Analyse gefunden, welche auch Carbid-Phasen zeigten. Im Temperaturgebiet -150°C — +250°C konnten keine Korngrenzebruche nachgewiesen werden; der Bruch war plastisch. Der Bruchweg ist durch Carbid-Phasen bestimmt, wo auch die Anreicherung von S und P stattfindet.

The fracture surfaces of tool steel K-13 (Hungarian Standard) were studied by Auger electron spectroscopy. Notched specimens of 3 × 3 mm2 were fractured in UHV (6 × 10−8 Pa) with a fracturer (Riber FR 100) and studied with a CMA analyser (Riber OPC 103). With our modification the fracturer was operated within the −150°C −+230°C temperature range. The fracture surfaces were tested with a scanning electron microscope (JEOL JSM 35). The evaluation of Auger spectra was based on the PHI (PALMBERG et al.). Handbook, however the backscattering correction of Jablonski was applied in some cases. The choice of adequate fracturing temperature proved to be very important. Low temperature fracture of this steel alloy is producing very rigid transgranular fracture. The effects of sample heat treatment and of fracturing temperature as well were studied in details. The Auger spectra of fracture surfaces are strongly affected by the heat treatment of the samples. The grain boundary fracture surface of a sample austenitized at 1100°C quenched and tempered at 600°C exhibited a strong enrichment of P, correlating with the enrichment of Cr, V and Mo. The transgranular fracture surface of the same sample but without tempering corresponded to the bulk composition. In some cases and spots on the fracture surfaces, giant S or P peaks were associated with secondary phases (inclusions) on the SEM pictures. Die Bruchflachen vom Werkzeugsstahl K-13 (ungarische Norm) wurden mittels Auger Elektronenspektroskopie untersucht. Gekerbte Proben mit einem 3 × 3 mm2-Querschnitt wurden im UHV (6 × 10−8 Pa) mit einem RIBER FR 100-Bruchgerat gebrochen und mittels eines CMA Analysators (RIBER OPC 103) untersucht. Das Bruchgerat konnte mit einer Weiterentwicklung im Temperaturgebiet −150°C − +230°C arbeiten. Die Bruchflachen wurden mit einem Rasterelektronenmikroskop (JEOL JSM 35) gepruft. Die Auswertung der Auger-Spektren wurden mittels des PHI-Handbuchs (PALMBERG et al.) ausgefuhrt; jedoch wurde eine Korrektur nach Jablonski fur die Ruckstreuung in einigen Fallen angewendet. Die Auswahl der geeigneten Bruchtemperatur erwies sich als sehr wichtig, da der Tieftemperaturbruch von dieser Stahllegierung sproden interkristallinen Bruch verursacht. Die Wirkung der thermischen Behandlung und der Bruchtemperatur wurden im einzelnen untersucht. Die Auger-Spektren der Bruchflachen hangen stark von der Warmebehandlung der Proben ab. Die interkristalline Bruchflache einer Probe, die bei 1100°C austenitisiert, abgeschreckt und bei 600°C getempert wurde, wies eine starke Anreicherung von P, in Verbindung mit einer Anreicherung von Cr, V und Mo auf. Die transkristalline Bruchflache derselben Probe ohne Temperung entsprach ihrer Volumenzusammensetzung. In einigen Fallen und an Stellen der Bruchflachen waren riesige S und P Signale mit Einschlussen auf den SEM-Abbildungen erkennbar.