Materials Science and Engineering

Materials of acryloide type are very often used in conservation and restoration of ceramic materials as adhesives, consolidants and protective coatings. As they do not have enough strength by themselves to satisfy more demanding interventions, inorganic particles were added as reinforcement in order to improve their mechanical properties. In the present work composite materials with matrix made from mixture of two acryloid copolymers, Paraloid B-72 and B-48N, were tested for extreme service condition that were simulated by exposing the samples to cavitation resistance.

In this paper, a study on the batch processing and characterization of microcellular foamed high-density polyethylene (HDPE/iPP) blends is reported. A microcellular plastic is a foamed polymer with a cell density greater than 109 cells/cm3 and fully grown cells smaller than 10 µm. Recent studies have shown that the morphology and crystallinity of semicrystalline polymers have a great influence on the solubility and diffusivity of the blowing agent and on the cellular structure of the resulting foam in microcellular batch processing. In this research, blends of HDPE and iPP were used to produce materials with variety of crystalline and phase morphologies to enhance the subsequent microcellular foaming. It was possible to produce much finer and more uniform foams with the blends than with neat HDPE and iPP. Moreover, the mechanical properties and in particular the impact strength of the blends were significantly improved by foaming.
(citation # 293)

Standard fused filament fabrication (FFF)-based 3-D printers fabricate parts from thermopolymers, such as polylactic acid (PLA). A new range of metal based PLA composites are available providing a novel range of potential engineering materials for such 3-D printers. Currently, limited material data, specifically thermal property characterization is available on these composites. As a result, the application of these materials into functional engineered systems is not possible. This study aims to fill the knowledge gap by quantifying the thermal properties of copperFill, bronzeFill, magnetic iron PLA, and stainless steel PLA composites and provide insight into the technical considerations of FFF composite 3-D printing. Specifically, in this study the correlation of the composite microstructure and printing parameters are explored and the results of thermal conductivity analysis as a function of printed matrix properties are provided. Considering the relative deviation from the filament raw bulk analysis, the results show the printing operation significantly impacts the resultant component density. Experimentally collected thermal conductivity values, however, do not correlate to the theoretical models in the literature and more rigorous quantitative exercises are required to determine true percent porosity to accurately model the effect of air pore volume fraction on thermal conductivity. Despite this limitation, the thermal conductivity values provided can be used to engineer thermal conductivity into 3-D printed parts with these PLA-based composites. Finally, several high-value applications of such 3-D printed materials that look metallic, but have low thermal conductivity are reviewed.

In order to assist researchers explore the full potential of distributed recycling of post-consumer polymer waste, this article describes a recyclebot, which is a waste plastic extruder capable of making commercial quality 3-D printing filament. The device design takes advantage of both the open source hardware methodology and the paradigm developed by the open source self-replicating rapid prototyper (RepRap) 3-D printer community. Specifically, this paper describes the design, fabrication and operation of a RepRapable Recyclebot, which refers to the Recyclebot's ability to provide the filament needed to largely replicate the parts for the Recyclebot on any type of RepRap 3-D printer. The device costs less than $700 in mate rials and can be fabricated in about 24 h. Filament is produced at 0.4 kg/h using 0.24 kWh/kg with a diameter ±4.6%. Thus, filament can be manufactured from commercial pellets for <22% of commercial filament costs. In addition, it can fabricate recycled waste plastic into filament for 2.5 cents/kg, which is <1000X commercial filament costs. The system can fabricate filament from polymers with extrusion temperatures <250 °C and is thus capable of manufacturing custom filament over a wide range of thermopolymers and composites for material science studies of new materials and recyclability studies, as well as research on novel applications of fused filament based 3-D printing.

The highest energy density among the rechargeable batteries is provided by lithium ion technology thanks to immense electrochemical potential of Lithium element. Among the recent studies which are about cathode materials LiMO2  stands out but capacity of LiMO2  cathode materials are not enough when their capacities compared with anode materials. High voltage LiNi0.5Mn1.5O4 spinel with an operating voltage of 4.7 V and theoretical capacity of 148 mAh/g is a promising candidate as the positive electrode in future lithium ion batteries for electric vehicle applications. LiNi0.5Mn1.5O4 is produced by sol-gel method is a very convenient method to obtaining the cathode material, due to its versatile advantages as obtaining high purity material. Gels which are produced via sol-gel method are coated onto Aluminum substrate to improve electrical, mechanical, chemical and optical properties. Galvanostatic test results are close to theoretical capacity of LiNi0.5Mn1.5O4  and the highest capacity value is determined as 131,4 mAh/g.

Generally, in most countries, there are no strict regulations regarding tire disposal. Hence, tires end up thrown in seas and lands as well as being burnt, harming the living beings, and are therefore considered a very dangerous pollution source for the environment. Over the past few years, several researchers have worked on incorporating shredded/powdered rubber tires into cement-based material. This strategy shows a dual functionality: Economic-environmental benefits and technological functionalization of the building material. Rubber-modified cement materials show interesting engineering and architectural properties due to the physical-chemical nature of the tire rubber aggregates. However, the abovementioned performances are affected by type, size, and content of polymer particles used in the cement-based mixtures production. Whereas an increase in the rubber content in the cement mix will negatively affect the mechanical properties of the material as a decrease in its compression strength. This aspect is crucial for the use of the material in building applications, where proper structural integrity must be guaranteed. In this context, the development of innovative manufacturing technologies and the use of multi-physics simulation software represent useful approaches for the study of shapes and geometries designed to maximize the technological properties of the material. After an overview on the performances of 3D printable rubber-cement mixtures developed in our research laboratory, a preliminary experimental Finite Element Method (FEM) analysis will be described. The modeling work aims to highlight how the topology optimization allows maximizing of the physical-mechanical performances of a standard rubber-cement component for building-architectural applications.

Computational complexity of multiscale methods based on the first-principles energetics is analyzed. Computational cost of such methods is dominated by expensive first-principles determination of structural energies and atomic forces, including structural relaxations. Information integration is an opportunity to eliminate recalculation of known data, and, consequently, to reduce the total cost of multiscale calculations. We propose the Structural Database as a universal tool for structural data integration, and explain its conceptual design and functionality, including data mining options. To exemplify benefits provided by the Structural Database, we consider search for new ground states, construction of a phase diagram for a bulk material, and prediction of surface patterning. We show that the Structural Database is a powerful tool for information integration and data mining, which can greatly reduce the cost of multiscale computations and materials design.

Nanosized LaFeO3material was prepared by 3 methods: high energy milling, citrate gel, and coprecipitation. The X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) show that the orthorhombic LaFeO3phase was well formed at a low sintering temperature of 500°C in the citrate-gel and co-precipitation methods. Scanning electron microscope (SEM) and transmission electron microscope (TEM) observations indicate that the particle size of the LaFeO3powder varies from 10 nm to 50 nm depending on the preparation method. The magnetic properties through magnetization versus temperatureM(T)and magnetization verses magnetic fieldM(H)characteristics show that the nano-LaFeO3exhibits a weak ferromagnetic behavior in the room temperature, and theM(H)curves are well fitted by Langevin functions.

The AlSiMg 0.3 casting alloy is used in the motor vehicle and aerospace industry, for parts in mechanical engineering, shipbuilding, fitting etc which require the casting alloy to have very high strength and hardness along with corrosion resistance. In order to optimize these properties, there is a need to study the effects of individual alloying elements in required proportions at different aging conditions. With the aim of improving the mechanical properties of LM-25 alloy, studies have been carried out on the effects of various alloying elements on its mechanical properties. In this process, we arrived at a particular range of compositions of the alloying elements for LM-25 by conducting several tests using the software and arrived at the final improved composition which gave superior mechanical properties.

Crumb rubber modification has been proven to enhance the properties of pure bitumen. This paper looks at some of the international standards for producing crumb rubber modified bitumen (CRMB) and reviews the effect of crumb rubber to the rheology of crumb rubber modified bitumen. The review shows that the rheology of CRMB depends on internal factors such as crumb rubber quantity, particle size, and pure bitumen composition, and external factors such as the mixing time, temperature, and also the modification technique. These factors govern the swelling process of crumb rubber particles that lead to the increase of viscosity of the modified bitumen. However, the mixing temperature and duration can cause rubber particles to depolymerize and subsequently cause loss of viscosity. Crumb rubber modification also improves the properties of bitumen by increasing the storage and loss modulus and enhancing the high and low temperature susceptibility. The effect of crumb rubber to aging propert...

Semiflexible pavement (SFP), a composite pavement, is formed by filling into a very open porous asphalt skeleton a specifically designed water consistency fluid mortar with a very high early and 28-day strength. The amalgamation of both components will produce a SFP where it will replace the conventional wearing course. The main goal of this investigation is to study the effect of various aggregate gradations towards producing SFP. These include determining the optimum binder, volumetric properties, and durability and strength of each aggregate gradation. The final results were statistically analyzed and two factor variance analyses (ANOVA) were performed to check on the significance at certain confidence limits. The results confirmed that different aggregate gradations significantly affect the properties mentioned.

Total Quality Management (TQM) is based on the conceptions of managing and enhancing the success of construction projects. When applied, TQM improves execution of time management of project, satisfies clients’ needs, minimizes the expenses and increases the profit of contractor, and fulfils safety regulations on the construction site. This research is aimed at evaluating the impacts of employing the concepts of TQM to the construction projects in Saudi Arabia. The results of the study were obtained through utilization of a descriptive analytical approach, where 300 questionnaires were distributed to engineering firms and companies with a response rate of 200 questionnaires, hence achieving the study sample for this research. The data gathered was analyzed by applying the Statistical Package for Social Science (SPSS) program and calculating the relative importance index (RII) and the mean values. From the research conducted, the outcomes showed that the management’s ability to commit...

Aluminum hybrid metal matrix composites are the field of interest of researchers because they are widely used in aerospace and automobile industries. A hybrid composite benefits the properties of two or more reinforcement materials and could contain unique physical, mechanical and tribological properties which are not achievable in other materials. In this study different amounts of SiC microsize (37 μm) particles were added to Al-Mg2Si composite using stir casting method. Then, hot extrusion was applied to the specimens. Finally, the effect of different amounts of SiC on the mechanical properties of Al-Mg2Si in-situ composite was investigated. The microstructure characteristics of the composite was studied using optical and scanning electron microscopy. The results showed that SiC particles had a good dispersion in the Al-Mg2Si matrix. The hardness increased from 110 for the bas composite to 135 brinell for the composite containing 9 wt. % SiC. The amounts of YS and UTS of the Al-Mg2Si composite was 90 and 160 MPa respectively and the addition of 9 wt. % SiC enhanced these values to 125 and 260 MPa respectively. However, the addition of SiC reduced the elongation from 6.7 % to 1 %. Moreover, the addition of 9 wt. % SiC increased the ultimate compressive strength from 280 to 430 MPa.

— In digital communication system, digital information can be sent on a carrier through changes in its fundamental characteristics such as phase, frequency and amplitude. The use of a filter plays an important part in a communication channel because it is effective at eliminating spectral leakage, reducing channel width, and eliminating interference from adjacent symbols (Inter Symbol Interference) ISI. It describe the developed and dynamic method of designing finite impulse response filter with automatic rapid and less error by an efficient genetic and neural approach. GA and Neural are powerful global optimization algorithm introduced in combinational optimization problems. Here, FIR filter is designed using Genetic, Neural approach by efficient coding schemes. We need to design these filters with some constraints imposed by requirements of the communication system in which we are going to use them. The use of optimization techniques have been proved to be quite useful towards the design of those digital filters with certain specifications. This paper reviews about the uses of optimization systems in digital filter design.

 Abstract— Data Leakage can be referred as the unauthorized transfer of classified information from a computer or data centre to the outside world. Big data is an evolving term that describes any voluminous amount of structured, semi-structured and unstructured data that has the potential to be mined for information. The data loss in such huge massive data sets may cause critical vulnerabilities. In this paper we proposed a novel model in Hadoop master/slave architecture for data leakage prevention with LRA algorithm. The LRA algorithm evaluates the Least Reliable Agent and sends it to the DLA (Data Leakage Avoider). DLA prevents the NameNode from allocating data to these agents.

—knitted fabrics find numerous applications in sportswear fabric industry, during their use it can be subjected to loading-unloading due to the body movements which can be indirectly affected by the dynamic elastic recovery value of the fabrics. The cyclic loads lead to the redistribution of fibers in the yarn structure, because they tend to get the minimum level of energy. Dimensional properties of knitted fabric are widely affected by the externally applied forces that could involve permanent deformation. Cotton/Spandex knitted fabrics are widely used for several applications. In this work, an attempt was done to analyze the effect of cyclic loading on cotton/spandex knitted fabric subjected to the different levels of cyclic loading under different values of initial extensions. Knitted fabric mechanical properties with different percentages of spandex were tested. The fabric properties and the number of cycles indicate the change of the residual extension and the drop in the fabric strength and stiffness.

Changes in the microstructure, volume fraction and distribution of phases during different stages of thermochemical processing of Ti-25Al-10Nb-3V-1Mo (at.%) castings were investigated. Up to 14.5 at.%(0.35 wt.%) of hydrogen was introduced into the material by ...

Silk fibre has received attention in the biomedical sector rather than textile production because of its excellent biocompatibility properties in the past century. Although silk fibre properties are different from area to area, it has created an opportunity in the biomedical sector to develop new silk-based medical textile products. &is research work aimed to study the structural, physical, mechanical, and thermal properties of Ethiopian silkworm cocoon’s filament. Eri and mulberry silk fibre properties such as morphological structure, chemical properties, linear density, filament length, tensile strength, elongation, thermal property, and luster were measured using ES ISO and ASTM standard methods. Statistical analysis result showed that eri silk fibre from Arba Minch had water removal temperature between 100°C and 125°C with a degradation temperature of around 400°C and eri silk fibre from both Addis Ababa and Awassa had an almost similar water removal temperature around 100°C and...

The main objective of this project is to develop and implement a prototype of a controller scheme using latest control algorithms and drives technology to capture maximum sun energy from sun through solar panel in day time. The efficiency of a solar panel is related to the amount of solar energy it absorbed, so it is necessary to track the sun’s position for the panel accurately. A new approach to implement a control unit so that the position of the panel is always kept perpendicular to the sun so as to capture maximum amount of energy. In this control unit a new tracking system is proposed, which comprises of a sensor (position), a microcontroller, and a stepper motor. The position sensor (pyranometer) always detects the position of the sensor. This sensor also detects the radiation from the sun. The fuzzy logic control approach is developed in the microcontroller to design a drive unit for stepper motor as well as to detect the sun position. By implementing this tracking system, the solar panel can be perpendicular to the sun at any moment in day time to obtain maximum solar radiation. The resulting structure has high efficiency, low cost and can be easily modified. This improves the performance of regular tracker nearby 30-40%.

Uncertainties associated with modelling of deteriorating bridges strongly affect management decisions, such as inspection, maintenance and repair actions. These uncertainties can be reduced by the effective use of health monitoring systems, through which information regarding in situ performance can be incorporated in the management of bridges.The objectives of this paper are twofold; first, an improved chloride induced deterioration model for concrete bridges is proposed that can quantify degradation in performance soon after chlorides are deposited on the bridge, rather than when initiation of corrosion at the reinforcement level takes place. As a result, the implications of introducing proactive health monitoring can be assessed using probabilistic durability criteria. Thus, the second objective of the paper is to present a methodology for performance updating of deteriorating concrete bridges fitted with a proactive health monitoring system.This methodology is illustrated via a simple example of a typical bridge element, such as a beam or a part of a slab. The results highlight the benefits from introducing ‘smart’ technology in managing bridges subject to deterioration, and quantify the reduction in uncertainties and their subsequent effect on predictions of future bridge performance.

Kaolin and quartz from Pugu and feldspar from Morogoro were used to produce feldspathic dental porcelain bodies. Mineralogical results from XRD revealed the presence of kaolinite, illite, microcline and clinochlore in the kaolin samples; albite, microcline, sanidine in the feldspar samples and only silica in the quartz samples. The chemical results studies by XRF revealed the presence of in varying proportions. Particle size distribution of all the raw materials were determined and particles <63 μm were used for preparation of batches. The batches of different compositions with ranges: quartz (12-22%), feldspar (75-88%) and kaolin (3-5%) were fired at 1100, 1200 and 1250 o C, and the developed properties were tested. The physico-mechanical properties studied exhibited volumetric shrinkage between 2 and 55.17%, open porosity between 6.67 and 40.00%, water of absorption between 7.1 and 40%, bulk densty of 1.43 – 5.68 g/cm 3 , and compressive strength at 0.13-32.25 MPa. The optimal firing temperature for the best results was found to be 1250 o C. The results obtained indicate that kaolin and quartz from Pugu and feldspar from Morogoro are potential raw materials for the production of dental porcelain.

Rotary degassing is one of the most frequently used melt treatment technologies used for processing liquid aluminum alloys. Despite this, the information available about the possible effects of this method on the double oxide-and nitride film (bifilm) content, especially when using different purging gases, is quite limited. For this reason, in this study, the effects of multiple rotary degassing treatments conducted with N 2 and Ar purging gases on the bifilm quantity of a casting aluminum alloy were compared. The characterization of the melt quality was realized by the computed tomographic (CT) analysis of reduced pressure test (RPT) specimens, image analysis, and scanning electron microscopy (SEM) of the fracture surfaces of K-mold samples. Based on the results, by the application of Ar as a purging gas, relatively low bifilm content can be achieved. On the other hand, while the use of N 2 leads to the formation of numerous small-sized nitride bifilms, which significantly increased the pore number density inside the RPT specimens. This can be associated with the nitride formation by the chemical reaction between the liquid aluminum alloy and the N 2 purging gas bubbles during the degassing treatments.

In this paper, we conduct a friction stir welding lap joint experiment on Al-Mg-Si alloy to investigate its formation and mechanical properties. By studying and observing the surface morphology, it was discovered that the higher the welding speed, the lower the burst and flash effect. In the cross-sectional analysis, we obtain larger EST (1.59) at rotating speed (1600 rpm), welding speed (150 mm/min) and 0.15 mm depression, and a nearly identical EST (1.58) at rotating speed (1200 rpm), welding speed (100 mm/min) and 0.15 mm depression. We talked about welding speed and other working parameters, and we found that rotating speed (1600 rpm) and welding speed (150 mm/min) with the more practical tensile shear load (10.11) produced significant results. In the Microhardness section, it was discovered that increasing the mixing head's rotational speed increases the heat input, resulting in a higher nucleation number of recrystallized grains and we obtain the best microhardness of the curve at rotating speed (1400 rpm), welding speed (150 mm/min) and 0.1 mm depression. The higher heat input (1600-150-0.15) along the fracture path results in a better metallurgical bonding effect of the cold lap, and the fracture propagates downward from the highest point of the cold lap to the lower sheet under the smaller EST.
Key Words: FSW; Tool Rotation Speed; EST; Microhardness; Fracture Path

The aim of this paper is obtaining and characterizing hydrogels based on different ratios of oxidized alginate (oA) and k-carrageenan (C), chemically cross-linked with adipic dihydrazide (adh). The alginate (A) was first oxidized with sodium metaperiodate in order to transform it into the dialdehyde derivative, a more reactive compound than alginate. A known procedure for oxidation of alginate with sodium metaperiodate in ethanol-water in order to improve alginate reactivity by transforming the hydroxyl end-groups into dialdehyde was used, preceded by a partially cleavage of the alginate chains. In the second stage, the mixture of dialdehydic derivative of oxidized alginate, k-carrageenan and glycerol subjected to reaction with adipic dihydrazide leads to a Semi-Interpenetrated Network covalently cross-linked alginate/k-carrageenan hydrogel (oACadh), based on the dihydrazone compound which is responsible for the chemical cross-linking. Pure alginate, k-carrageenan, oxidized alginate...

High-strength concrete (HSC) has several well-known technical, aesthetic, and economic advantages over normal-strength concrete (NSC), which explains the increasing popularity of the former material in the construction domain. As in the case of NSC, however, high temperature adversely affects HSC mechanical properties even more than in NSC, as indicated by the many studies performed so far on HSC at high temperature (hot properties) or past a thermal cycle at high temperature (residual properties). Since many code provisions concerning concrete properties versus high temperature were developed for ordinary concrete and the available models (in terms of stress-strain relationship) come mostly from the tests on NSC—as the tests on HSC are less numerous—developing predictive relationships for HSC exposed to high temperature is still an open issue, especially with reference to many parameters affecting concrete compressive strength, like temperature as such, heating rate, water-to-binde...

A laboratory research project was conducted to examine the impact resistance of laminated asphalt shingles with various support conditions. Roof panels were constructed using laminated asphalt shingles installed over weathered asphalt shingles as well as weathered wood shingles in both " nested " and " bridged " applications. A control panel with standard installation was constructed for comparison purposes. Solid ice spheres simulating hail were launched against the roof panels at established speeds and energies. Results indicated that asphalt shingles installed over asphalt shingles or wooden shingles were more susceptible to impact-caused damage than asphalt shingles installed over plywood decking. Additionally, shingle areas supported by underlying shingles or decking performed better than shingle areas with air spaces underneath (unsupported).

Ductile iron castings with 2 and 10 mm thickness with varying chemical composition were cast in sand molds to identify the effect of sample thickness on microstructural changes and tensile properties. The effect of melt chemistry and molten metal processing variables (i.e., pre-conditioning of the base iron, inoculation type and practice, and pouring temperature, etc.) on the tensile properties of thin-wall ductile iron castings has been investigated. Comparison of 2 and 10 mm sections within the same casting showed that section size was the main factor influencing tensile properties of ductile irons. While many samples from 2 mm sections showed low elongation values, likely caused by a high pearlite content or presence of carbides, many others showed higher elongations and superior strengths well above those required in ASTM A536 grades. At moderate to high elongations, the thin-wall samples were significantly stronger than samples from identical irons of 10 mm section.

— Designing an efficient Distributed Database System (DDBS) is considered as one of the most challenging problems because of multiple interdependent factors which are affecting its performance. Allocation and fragmentation are two processes which their efficiency and correctness influence the performance of DDBS. Therefore, efficient data fragmentation and allocation of fragments across the network sites are considered as an important research area in distributed database design. In this paper presents an approach which simultaneously fragments data vertically and allocates the fragments to appropriate sites across the network. Bond Energy Algorithm (BEA) is applied with a better affinity measure that improves the generated clusters of attributes.

The aim of this publication is to present a general strategy to engineer more efficient photoluminescent dendritic molecules based on polyhedral oligomeric silsesquioxane (POSS) cores. A series of chromophores were grafted
on POSS cores to form dendritic molecules for which steric hindrance was used as a trigger to tune their photophysical properties. For fluorescence in the blue/near-UV spectral ranges, 4-vinylbiphenyl molecules were chosen as model chromophores to present a general approach based on stable chemistry and bulky groups grafted to the chromophores to enhance photoluminescence efficiency of the dendritic molecules.
Photoluminescence quantum yields as well as steady-state and time-resolved solution spectroscopy along with molecular dynamics investigation and electronic structure calculations on a family of new materials are reported. We highlight an apparent contrast between free chromophore and dendritic molecules photophysical properties and show that chromophores’ engineering and confinement around an inorganic core allows the design of more efficient photoluminescent dendritic molecules relevant to sensors and hybrid light-emitting diodes.