Selected Papers from ICIR EUROINVENT - 2023

Recovery of the energy contained within the waste heat from various processes represents an important concern for the efficiency of energy utilization. This paper aims to present an overview of currently employed methods for waste heat energy recovery in the automotive industry, with an emphasis on processes within thermal combustion engines and recovery methods based on thermo-electric generators (TEG). While TEG technology is capable of direct conversion of heat into electricity, conversion efficiency is quite low. Efforts are made to optimize these systems (number, size, form, positioning, location, etc.) in order to minimize heat loss and maximize energy recovery. The review concluded that the efficiency of TEG conversion might be improved by choosing appropriate characteristics for the recovery system for specific processes analyzed, such as thermoelectric materials, geometry, location, and type of cooling fluid.

In recent years, improving the surface of titanium implants is increasingly being studied, in order to reduce their rejection rate. Thus, there are several methods by which the properties of the base material, in this case, the titanium alloy, can be improved, such as anodizing, micro-arc oxidation, plasma spraying, physical vapour deposition, biomimetic deposition, chemical conversion deposition etc. Regarding the deposition process by chemical conversion, the phosphating process presents a multitude of advantages, including good adhesion to the substrate and the capacity of improving cellular adhesion due to the porosity of the layer. Therefore, the paper aims to study the tribological characteristics by evaluating the adhesion and coefficient of friction of three types of phosphate layers deposited on the surface of the titanium alloy, Ti6Al4V, using a UMTR 2M-CTR Micro-tribometer and SEM. The results of the scratch tests revealed that the phosphate layers have good adhesion at the substrate and the values of the coefficient of friction were increased due to the roughness of the surface.

Geopolymerization is the most suitable method for the valorization of mineral wastes with high contents of Si and Al oxides. Compared to Ordinary Portland Cement (OPC) materials, the geopolymers exhibit better compressive strength and thermal stability, but their flexural strength is also limited by their brittle matrix. The aim of this study is to evaluate the thermal behavior of ambient-cured fly ash-based geopolymers reinforced with recycled glass fibers in order to estimate the possibility of manufacturing precast concrete products. The thermogravimetric analysis (TGA) showed a low weight loss up to 200 ℃, followed by a much lower decrease in the 200 ℃–500 ℃ temperature range. The TA curves follow closely the trend of the Differential Thermodynamic Analysis (DTA) curves, which confirm a highly endothermic reaction in the 20 ℃–200 ℃ temperature range due to the removal of free or physically bound water. Above this temperature, small peaks corresponding to the dihydroxylation of -FeOOH or transformation of Ca(OH)₂ to CaCO₃ can be observed. The thermal behavior of both samples is similar, confirming that the presence of glass fibers doesn’t influence the thermal behavior of fly ash-based geopolymers.

The study aimed to evaluate the effectiveness of hybrid polymer ZOPAT compared to single polymers in treating textile wastewater. The research analyzed reduction of color, chemical oxygen demand (COD), turbidity, and suspended solids using jar testing. Response Surface Methodology (RSM) was employed to optimize the treatment, analyze variance, and create pertur-bation and desirability plots for multiple responses. The storage conditions of the hybrid polymer were also investigated. The results showed that ZOPAT was highly effective in reducing color, with a 93% reduction compared to other treatments. Additionally, turbidity and suspended solids were reduced by 100%, and COD was reduced by up to 80%. The RSM multi-response outcome showed a desirability plot of 0.592. The hybrid polymer required only 17.5 min for coagulation treatment, while the other treatments re-quired more than 40 min to achieve maximum effectiveness. The validation test showed that the optimization model’s error rate was less than 1%. The study recommended that hybrid polymer solutions be stored in a cold room for up to 20 days to maintain consistency. The findings suggest that hybrid polymer is a highly effective coagulant for treating textile wastewater, with significant reductions in color, turbidity, and suspended solids. The use of RSM allowed for the optimization of the treatment, and the storage conditions were determined to ensure consistent results over time. Overall, the study’s results have significant implications for the water treatment industry, with potential applications in treating wastewater in other industries.

Sustainability of hydroelectric dams has been questioned due to the sedimentation, erosion and vortex formation at the dams. This study had assessed the potential of sedimentation, erosion and vortex formation based on the flow pattern formed via hydraulic physical model (Scale of 1:100). Four cases have been tested which are Case 1 (the position of water inlet at the middle with stage of 0.38 m), Case 2 (the position of water inlet at the middle with stage 0.34 m), Case 3 (the position of water inlet at the side with stage of 0.38 m) and Case 4 (the position of water inlet at side with stage 0.34 m). Based on Case 3, the range of flow velocities obtained was 0.3–2.1 m/s at 20% from water surface, leading to erosion at the dam bank and sedimentation which focused on the side of the dam that threatened the stability of the dam due to the concentrated load of sediment. Vortex type 5–6 had been identified for a period of 15–30 s. Overall, the flow pattern at the dam up-stream was influenced by the position of water inlet from dam’s upstream, flowrate of the dam and the depth from the water level.

High volatile fatty acid natural rubber latex foam (H-VFA NRLF) was prepared via the Dunlop process using sodium bicarbonate, NaHCO₃ as the blowing agent. The influence of different foaming temperatures (140 ℃, 150 ℃, 160 ℃, 170 ℃, and 180 ℃) on relative foam density, average cell size, cell size distribution frequency and compression stress-strain of H-VFA NRLF were studied. The average cell sizes were related to the relative foam density of H-VFA NRLF. As the temperature increased, the relative foam density increased, and eventually the average cell size decreased due to high amount of gas generated by blowing agents simultaneously. Meanwhile, smaller cell sizes were distributed as the temperature increased. It was found that the optimum temperature for H-VFA NRLF was 150 ℃ due to the lowest relative foam density and significantly larger uniform cell size were produced. Thus, the lowest compression stress up to 60% of strain was found at 150 ℃ and increased with increasing temperature. The mechanical properties were correlated with the morphology and physical properties of the H-VFA NRLF, respectively.

Landslides in tropical hilly terrain have become a threat to the community. The difficulty of predicting future landslides can be overcome by detecting signs of past landslides especially in tropical hilly terrain like Cameron Highland, Pahang Darul Makmur. Basic skills in geomorphology and remote sensing are needed in detecting and mapping past landslides due to its geomorphological features that have been modified because of erosion, weathering, and development. However, an approach by using remote sensing and Geographic Information System techniques, the detection of geomorphological features can be done. Among the features that can be seen is hummocky topography, existence of articulating head scarps, crowns, main scarp, side scarps and convex hillslopes followed by concave hillslopes. The activation of inactive landslides is usually caused by natural factors and human factors. Natural factors consist of high rainfall distribution which weakens the soil structure and causes physical and chemical weathering process or rate to increase. About 40% of slopes in the study area with the steepness of 25° which is identified as the main natural factor to slope failures. Human factors comprise of the construction of permanent and large-scale infrastructure which exerts load hence weakening the slope strength. This causes a growth of tension cracks which are perpendicular to the slope face and is expanding up to this day.

The use of coal additives in concrete has acquired popularity in recent years due to their potential performance-enhancing benefits. The ability to mitigate aggressive ion penetration, a chemical reaction that can cause concrete to degrade and potentially fail, is one of their most significant advantages. This literature review concentrates on the effect of coal additives, specifically coal fly ash and bottom ash, on the performance of concrete, with an emphasis on its strength and resistance to chemical attack. The review investigates several studies that investigate the properties of coal additive concrete, including its compressive strength, durability, and chemical penetration resistance. The findings indicate that the addition of coal to concrete can improve its properties, resulting in enhanced performance and durability. However, certain limitations must be considered, such as variations in the properties of coal residue based on the source and combustion process, for which geochemical analysis can provide insight into the causes. To fully comprehend the potential of coal additives in concrete and to address any limitations associated with their use, additional research is required.

This study aims to compare and assess the quality of two biogas reforming processes: steam reforming of biogas (SRB) and tri-reforming of biogas (TRB). SRB if the conventional method of producing hydrogen efficiently. TRB, on the other hand, is a relatively new innovative way to achieve higher hydrogen yield at less energy expense and lower carbon dioxide (CO₂) production. Both processes still have room for improvement, so optimizations should be considered to attain higher hydrogen yields and assess the effectiveness of both processes. The process simulation and sensitivity analysis were carried out using chemical process simulator (CPS), Aspen HYSYS, and its built-in sensitivity analysis tool. Direct comparisons of the results and evaluations of specific parameters targeted in the sensitivity analysis were then conducted, where the effects of changing molar ratio, temperature, and pressure were analyzed. The conversion of methane, conversion of CO₂, ratio of hydrogen to carbon monoxide (CO) produced, and hydrogen yield were also calculated. Since this study was only simulated on Aspen HYSYS, the results should be taken as an estimation of the processes under ideal conditions. The results lack chemical analysis and are limited to the software’s mathematical and computational abilities. However, the sensitivity analysis obtained decent correlation with literature and recorded trends that showed the feasibility of SRB and TRB in industrial conditions.

Various types of composite materials were being used in boat manufacturing especially for hull production as a main part. Natural composite materials such as teak sawdust, wood ash and silica particles have been utilized in boat hull making from previous researchers. This paper revised mechanical properties impact on several composite materials mixed with epoxy resin matrix by using hand lay-up method. Other than that, the main focused in this study is on the application of ceramic particles waste as a composite material. In-stead of being used as land-filling, ceramic particles waste can be reused in becoming value-added composite materials in specific area which brings benefits to environment and enhance the properties for other materials in terms of physical and mechanical. This study also presents an assembled and up-to-date review of physical, mechanical, durability and other durable potential abilities of ceramic fine aggregate which have huge ability usage in concrete production, soil stabilization, bricks block and road pavement structure. The percentage of particles usage from previous studies were from 2% up to 20% and the findings indicate that usage of ceramic waste particles improves flexural, durability, compressive, geotechnical and mechanical strength properties compare to standard materials usage. Thus, a new application area will be explored from this study on the usage of ceramic particles waste to the resin on the interface between the composite materials and core materials used in production of boat hull.

This study explores the potential of shrimp shells (SS), a widely available waste material, for biofuel production through torrefaction, offering an alternative approach to address environmental and energy scarcity issues. The torrefaction was conducted at 200, 250, and 300 ℃ in a fixed bed reactor, resulting in varying yields of biochar, bio-oils, and biogas. As the temperature increased, the biochar yield declined from 64% to 34%, while the bio-oils and biogas yields rose to 28% and 38% respectively. Compositional changes were investigated using proximate and ultimate analyses, revealing significant reductions in moisture (from 22.97% to 4.55%) and volatile matter (from 71.67% to 20.19%), while the fixed carbon content increased from 3.48% to 68.91%. FTIR spectroscopy confirmed structural alterations in the SS, including dehydration and transformations of specific compounds. The results suggest the feasibility of SS torrefaction for biochar production, which has potential applications in carbon sequestration and energy generation.

The development of filler- and fibre-reinforced vegetable oil composites has received considerable attention in recent years due to their environmental friendliness and potential to replace synthetic composites. Vegetable oil composites can be reinforced with either natural or synthetic fillers/fibres, resulting in partially or fully green composites. However, synthetic fibers have the disadvantage of being non-renewable and unsustainable due to their production from petroleum-based sources. To address this limitation, there is a growing trend toward hybridizing two or more types of filler/fibers as a hybrid reinforcement system, which can improve the supporting properties of the composites. Therefore, this review article specifically focuses on the use of hybrid filler/fibers in vegetable oil-based composites, including the various types of hybrid fiber/fibers, vegetable oils used, and their potential applications. Additionally, the mechanical and thermal properties of these composites are also being reviewed.

Over the years, the extrusion technique has captured the attention of polymer industries by meeting the demand for polymer processing and fabrication of final products. Extrusion is a continuous process, and it has a lot of potential in the increasing polymer sector, especially in the three-dimensional (3D) printing sector. 3D printing is popular because the feedstock filament form is accessible and produce able. The properties of the filament used influence the printed part qualities regardless of the FDM parameters. This study provides information on how extrusion parameters affect the diameter of extruded filaments. This study reviews previous studies on the effect of varied extrusion settings on filament diameter. The review will serve as a resource for researchers in the 3D printing sector to fabricate their filaments for 3D printing. Overall, this paper will provide solutions to overcome issues in obtaining optimal filament diameters for future research projects.

Geopolymers are emerging as an eco-friendly alternative to conventional building materials. These materials exhibit enormous potential as a substitute for traditional technologies like concrete, but more applied studies are needed to evaluate their practicality on an industrial scale. Moreover, each type of raw material needs to be optimized in terms of parameters that influence the properties of the final product. In order to optimize geopolymers in terms of mechanical performance, the obtaining parameters and the possibilities offered by the Taguchi method were considered to design a series of geopolymers suitable for civil engineering applications. The optimization was conducted considering: (i) three blends comprising a different percentage of fly ash (FA), fly ash with S (FS) and red mud (RM), (ii) three different liquids to solid ratios (0.70, 0.75 and 0.80), (iii) three different Na₂SiO₃ to NaOH ratios (1.0, 1.25 and 1.5) and (iv) three different molar concentrations of NaOH solution (3, 6.5 and 10 M). The mechanical strength tests showed that the mixture with the best compressive strength is the one consisting of 35 wt.% FA, 15 wt.% FS and 50 wt.% RM, with liquid: solid ratio (L/S) of 0.7, Na₂SiO₃: NaOH of 1.5 and 10 M NaOH, respectively. In terms of flexural strength, the mixture with the same amounts of raw materials, but the following parameters exhibited the highest value after 28 days of curing: L/S of 0.75, Na₂SiO₃:NaOH of 1 and 7M NaOH.

Nepheline geopolymer ceramics have emerged as a promising sustainable alternative to traditional cementitious materials in various applications. As the sintering mechanism plays a crucial role in the densification and mechanical performance of ceramics, therefore, in this paper, a preliminary study was conducted to examine the effects of densification towards mechanical properties of geopolymer-based nepheline ceramics upon sintering. The said innovative geopolymer technology can convert raw materials of aluminosilicate activating with alkaline activator into ceramic-like materials requiring low temperatures. The experimental procedure includes the synthesis of nepheline geopolymer ceramics through the geopolymerization method, then sintered at different temperatures to explore the sintering behavior and its impact on the materials’ microstructure and mechanical performance. The densification behavior of nepheline geopolymer ceramics during sintering was analyzed by evaluating the changes in density, shrinkage, and porosity. The microstructural evolution and are determined by using SEM. The relationships between sintering conditions, microstructure, and mechanical performance were investigated to understand the underlying mechanisms affecting the material’s strength and durability. The geopolymer exhibited its highest flexural strength of 54.93 MPa when sintered at 1200 ℃, while the lowest strength of 6.07 MPa was observed at a sintering temperature of 200 ℃. The findings demonstrate a positive correlation between the sintering temperature and the flexural strength of the geopolymer ceramics, indicating that higher temperatures lead to increased strength. Ultimately, this knowledge can facilitate the broader utilization of nepheline geopolymer ceramics as sustainable materials in various engineering and construction applications.

By replacing traditional Portland cement (OPC) with crumb rubber in fly ash-based geopolymer mortar, waste tyre disposal and natural mineral aggregate use can be reduced, resulting in lower CO₂ emissions. Crumb rubber geopolymer mortar is formed when sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) are mixed with fly ash (class F) to make aluminosilicate gel. All of the fly ash geopolymer preparations followed the same ratio of solid to liquid (2:1) and the same ratio of NaOH solution (12M) to Na₂SiO₃ solution (2.5). Different amounts of crumb rubber (0%, 5%, 10%, 15%, and 20% by weight of solid) were added to the mixture. The results show that the compressive strength of the geopolymer mortar decreased with increasing crumb rubber loading. The results of the analysis show that the compressive strengths of CR-0%, CR-5%, CR-10%, CR-15%, and CR-20% are 25,59,14,31,11.19,10.38, and 8.16 MPa. The strength is diminished because of inadequate interfacial adhesion between the crumb rubber and geopolymer paste. As the sample weight fell, the percentage of crumb rubber in the geopolymer mortar in-creased, but the density decreased.

Finding solutions regarding the promotion of the biological response of metallic implants became thoroughly researched, especially by surface modification treatments, due to the high number of clinical demands and the advantageous commercial context. Most of the researchers focused on hydroxyapatite or metal oxide coatings deposited by different methods (electrodeposition, sol-gel, physical vapor deposition, etc.). However, in the last few years, chemical conversion coatings have increased attention in the field of biomaterials. The phosphate layers obtained by this technology have multiple benefits, among which are high adherence to the substrate, similar morphology with the bone, high corrosion resistance, etc. Also, the phosphate coatings present chemical stability and good wear resistance and don’t have an impact on the mechanical properties of the substrate. Therefore, this paper aims to analyze the evolution of research in the field of coatings for metallic biomaterials, focusing on conversion coatings deposited on biomaterials, using bibliometric analysis. The results show an increase in the number of publications regarding the chemical conversion process since 2012, many of which are about the layers deposited on magnesium and titanium alloys.