Hasil untuk "Mechanical industries"

A. A. Azeez, K. Rhee, Soojin Park et al.

C. Ma, A. Z. Awang, W. Omar

Abstract Off late, the continuously depletion of the ozone layer and global warming issue have increased the awareness of the construction industries in using more eco-friendly construction materials. Against this background, geopolymer concrete has started to gain significant attention from the research scholars and construction practitioners, due to its advantageous in using by-product waste to replace cement and reducing greenhouse gas emission during its production. It also possesses better mechanical properties and durability compared to conventional concrete. Despite its advantageous, the use of geopolymer concrete in practical is considerably limited. This is mainly due to the lacking in the studies in terms of structural elements, design and application studies. This paper reviewed the material and structural performances of geopolymer concrete to identify the research gaps in this area for future research development. Analysis shown that geopolymer concrete can replace conventional concrete as they presented better mechanical properties, higher durability and more desirable structural performances compared with conventional counterparts. More studies are still needed for practical design standards and finally, the full scale studies on the structural elements should be established to ensure its feasibility in practical.

Pawankumar Rai, Srishti Mehrotra, S. Priya et al.

The progression of plastic pollution is a global concern. "Reuse, reduce and recycle" offers a solution to the burdening issue, although not enough to curb the rampant use of plastics. Biodegradable plastics are gaining acceptability in agriculture and food packaging industries; nevertheless, they occupy a rather small section of the plastic market. This review summarizes recent advances in the development of biodegradable plastics and their safe degradation potentials. Here, biodegradable plastics have been categorized and technology and developments in the field of biopolymers, their applicability, degradation and role in sustainable development has been reviewed. Also, the use of natural polymers with improved mechanical and physical properties that brings them at par with their counterparts has been discussed. Biodegradable polymers add value to the industries that would help in achieving sustainable development and consequently reinforce green economy, reducing the burden of greenhouse gases in the environment and valorisation of waste biomass.

Farah Maria Drumond Chequer, G. Oliveira, E. Ferraz et al.

Dyes may be defined as substances that, when applied to a substrate provide color by a process that alters, at least temporarily, any crystal structure of the colored substances [1,2]. Such substances with considerable coloring capacity are widely employed in the textile, pharmaceutical, food, cosmetics, plastics, photographic and paper industries [3,4]. The dyes can adhere to compatible surfaces by solution, by forming covalent bond or complexes with salts or metals, by physical adsorption or by mechanical retention [1,2]. Dyes are classified according to their application and chemical structure, and are composed of a group of atoms known as chromophores, responsible for the dye color. These chromophore-containing cen‐ ters are based on diverse functional groups, such as azo, anthraquinone, methine, nitro, aril‐ methane, carbonyl and others. In addition, electrons withdrawing or donating substituents so as to generate or intensify the color of the chromophores are denominated as auxo‐ chromes. The most common auxochromes are amine, carboxyl, sulfonate and hydroxyl [5-7].

F. Awaja, M. Gilbert, G. Kelly et al.

Yanan Liu, Ye Ding, Li-jun Yang et al.

Abstract Engineering alloys are widely applied as important functional structural materials in aerospace, electronics, metallurgy, and other high-end engineering industries due to their superior properties. However, their further application remains notably restricted by numerous inherent limitations, including low hardness, terrible wear and high-temperature oxidation resistance. In response to this problem, the development of laser cladding (LC) technology has provided new approaches for surface modification of engineering alloys. In this review paper, the recent progress made in the preparation of engineering alloys by LC technology is thoroughly investigated. The elementary knowledge in this field is provided to establish the internal relationships among the laser processing parameters, microstructure, and significant mechanical properties. The LC processing methods and material systems are reviewed, and the critical functional coatings related to this field are also summarised and explored in detail. Furthermore, the current challenges and future efforts are presented, identifying the existing knowledge and technology gaps while also attempting to determine future research directions.

Peng Hu, Qingyi Xie, Chunfeng Ma et al.

Marine biofouling profoundly influences marine industries and activities. It slows the speed and increases the fuel consumption of ships, corrodes the offshore platforms and blocks the seawater pipelines. The most effective and economic antifouling approach is using coatings. Fouling release coatings (FRCs) with low surface free energy and high elasticity weakly adhere to marine organisms so they can be readily removed by the water shear force. FRCs have received increasing interest because they are biocide-free and hence eco-friendly. Yet, traditional silicone based FRCs have weak adhesion to substrate, low mechanical strength and low fouling resistance, limiting their applications. In recent years, many attempts have been made to improve their mechanical properties and fouling resistance. The review deals with the progress in construction of high-performance silicone based fouling release surfaces.

A. K. Singla, Mainak Banerjee, A. Sharma et al.

Abstract Selective laser melting (SLM) has received huge attention recently by the research community due to feasibility of realization of tailored intricate metallic structures having applications in biomedical, aviation and energy industries. SLM of Ti6Al4 V is found to be one of the most demandable and potential area. Present work is aimed for critical review of noteworthy contributions in terms of SLM process parameters, defects and various post processing techniques considered by various researchers. Proper selection of process parameters can arrest the tendency of defect generation and appropriate post treatment results in improvement in mechanical behavior in comparison with as-built SLMed Ti6Al4 V components. Efforts have been made to identify correlations between SLM parameters, specially scan speed, laser power, hatch spacing and layer thickness, with prominent defects. Different post processing approaches considered by important research studies have been extensively analyzed and their impact on defects and mechanical behavior especially fatigue performance and biocompatibility of SLM-fabricated Ti6Al4 V alloy is revealed. Many remedies have been identified in the form of optimization of process parameters and post processing techniques. The outcomes of work have clearly facilitated in developing a better scientific understanding of SLMed Ti6Al4V alloy and have also opened many dimensions for future investigations.

N. Geier, J. Davim, T. Szalay

Abstract Carbon fibre reinforced polymer (CFRP) composites have excellent specific mechanical properties, these materials are therefore widely used in high-tech industries like the automobile and aerospace sectors. The mechanical machining of CFRP composites is often necessary to meet dimensional or assembly-related requirements; however, the machining of these materials is difficult. In an attempt to explore this issue, the main objective of the present paper is to review those advanced cutting tools and technologies that are used for drilling carbon fibre reinforced polymer composites. In this context, this paper gives a detailed review and discussion of the following: (i) the machinability of CFRP including chip removal mechanisms, cutting force, tool wear, surface roughness, delamination and the characteristics of uncut fibres; (ii) cutting tool requirements for CFRP machining; and (iii) recent industrial solutions: advanced edge geometries of cutting tools, coatings and technologies. In conclusion, it can be stated that advanced geometry cutting tools are often necessary in order to effectively and appropriately machine required quality features when working with CFRP composites.

S. S. Dhaliwal, Jaswinder Singh, P. K. Taneja et al.

S. Nemani, Rama Kishore Annavarapu, Behrouz Mohammadian et al.

Low cost, controlled crystallinity, chemical, and mechanical stability enable application of polymers in energy, water, electronics, and biomedical industries. Recent studies have shown that tailoring surface properties of polymers impacts their durability and functionality in these applications. However, the functionality and performance of polymer‐based devices and systems are greatly affected by the modification method and the process parameters, highlighting the need for understanding these methods and their mechanisms of operation in detail. The selection of the modification method invariably decides the properties enhanced in the polymer. In this review, various polymer surface modification treatments are discussed. These methods are categorized into physical, chemical, thermal, and optical ways, while illustrating their advantages and disadvantages. This review also explores the surface modification of polymers by patterning which encompasses one or more surface treatment methods. An application‐oriented study is presented discussing the relative importance of a method pertaining to a specific field of end‐application.

Saurabh Khandelwal, K. Rhee

Abstract Basalt fibers (BFs) have attracted much attention in the composites industry because they are chemically stable and have excellent mechanical and thermal properties. Due to their high commercial value, BFs have many applications in the polymer and construction industries. Although BF dosage is a key factor in basalt-fiber-reinforced composites (BFRCs), and mechanical performance improves significantly as the dosage increases, the fiber–matrix interface is another important parameter that determines the performance of BFRCs during their service life. The adhesion between the matrix and the BF is crucial for transferring stress and enhancing the mechanical properties of the composite. This paper reviews polymer and cement composites reinforced with BF and discusses strategies for improving the fiber–matrix interface, such as surface modification of the fibers and the addition of micro- and nanofillers to the matrix.

M. Zwawi

Increased environmental concerns and global warming have diverted focus from eco-friendly bio-composites. Naturals fibers are abundant and have low harvesting costs with adequate mechanical properties. Hazards of synthetic fibers, recycling issues, and toxic byproducts are the main driving factors in the research and development of bio-composites. Bio-composites are degradable, renewable, non-abrasive, and non-toxic, with comparable properties to those of synthetic fiber composites and used in many applications in various fields. A detailed analysis is carried out in this review paper to discuss developments in bio-composites. The review covers structure, morphology, and modifications of fiber, mechanical properties, degradable matrix materials, applications, and limitations of bio-composites. Some of the key sectors employing bio-composites are the construction, automobile, and packaging industries. Furthermore, bio-composites are used in the field of medicine and cosmetics.

Julia Didier Pedrosa de Amorim, K. C. De Souza, C. R. Duarte et al.

Mohammad Khajavian, V. Vatanpour, Roberto Castro-Muñoz et al.

The high molecular weight of chitin, as a biopolymer, challenges its extraction due to its insolubility in the solvents. Also, chitosan, as the N-deacetylated form of chitin, can be employed as a primary material for different industries. The low mechanical stability and poor plasticity of chitosan films, as a result of incompatible interaction between chitosan and the used solvent, have limited its industrialization. Deep eutectic solvents (DESs), as novel solvents, can solve the extraction difficulties of chitin, and the low mechanical stability and weak plasticity of chitosan films. Also, DESs can be considered for the different chitosan and chitin productions, including chitin nanocrystal and nanofiber, N,N,N-trimethyl-chitosan, chitosan-based imprinted structures, and DES-chitosan-based beads and monoliths. This review aims to focus on the preparation and characterization (chemistry and morphology) of DES-chitin-based and DES-chitosan-based structures to understand the influence of the incorporation of DESs into the chitin and chitosan structure.

Yichun Ding, Haoqing Hou, Yong Zhao et al.

P. Chawla, Ishwar B. Bajaj, S. Survase et al.

Summary Bacterial cellulose, an exopolysaccharide produced by some bacteria, has unique structural and mechanical properties and is highly pure as compared to plant cellulose. This article presents a critical review of the available information on the bacterial cellulose with special emphasis on its fermentative production and applications. Information on the biosynthetic pathway of bacterial cellulose, enzymes and precursors involved in bacterial cellulose synthesis has been specified. Characteristics of bacterial cellulose with respect to its structure and physicochemical properties are discussed. Current and potential applications of bacterial cellulose in food, pharmaceutical and other industries are also presented.

Shaona Wang, Yang Yang, Wenqing Xu et al.

Abstract As an integrated CO2 capture and utilization (ICCU) process, direct electrochemical reduction of amine captured-CO2 reduction reaction (cCO2RR) has enormous advantages in energy efficiency and operating cost. The low product selectivity is an urgent issue. Here, we found that the hydroxyl (-OH) on CeO2 can significantly enhance CO selectivity. After hydroxyl modification, the CO faraday efficiency (FECO) was surprisingly increased by 188% (relative increase rate). The correlation coefficient between -OH quantity and FECO is as high as 0.98. Further study indicated that the presence of -OH can lead to a more compact electrochemical double layer (EDL) and charge transfer resistance by proton transfer. The -OH can also enhance CO2 adsorption and stabilize the intermediate species (*COOH). DFT results further demonstrate that the rate-determining step was proton transfer from the surface -OH to MEACOO−, -OH modification can reduce the energy barrier to as low as 0.39 eV. This work provides additional insights into improving selectivity in amine-based cCO2RR, advancing the development of ICCU technology.

Jingbo Zhao, Zhengping Gao, Tianhui Zhao et al.

Hydrogen, as a zero-carbon secondary energy carrier, provides a unified pathway for low-carbon energy transformation. In electro–hydrogen coupling systems (EHCSs), surplus renewable power is stored via water electrolysis and later reconverted to electricity using fuel cells or gas turbines, enhancing the system’s flexibility and reliability in support of deep decarbonization. This study constructs an electricity–hydrogen energy-recycling model based on a coupling relationship considering the bidirectional conversion between electricity and hydrogen. A multistage carbon-emission-reduction indicator constraint is also established. Additionally, the green-certificate and carbon trading markets are introduced to optimize equipment investment and operation costs while achieving carbon-emission reduction. A case study reveals that the proposed EHCS planning model effectively allocates carbon emissions across different system stages, while mitigating economic repercussions, thus ensuring closer alignment with China’s emission-reduction policies. Incorporating diverse market mechanisms significantly enhances the system’s economy and decision-making flexibility, particularly in addressing future challenges in the energy market.

Sara Herreras Martínez, Justus Mesman, Daniel Møller Sneum et al.

Abstract Background While energy communities working on electricity provision have been extensively studied, thermal energy communities (TECs) focusing on bringing district heating (DH) systems to decarbonise heat systems in buildings have been relatively under-researched. This study addresses this gap by presenting the first comprehensive examination of key factors influencing the emergence and development of TEC projects in Denmark, Germany, and the Netherlands. The study uses an established analytical framework from previous research encompassing seven dimensions: market structure, hard- and soft institutions, financing, physical infrastructure, capacity, and interactions with other stakeholders. Data are gathered through a literature review and interviews. Results TECs have emerged at different times in each country, shaped by contextual circumstances and diverse forms of institutional support. Elements that have supported the development of TECs are regulatory frameworks promoting DH growth, heat decarbonisation policies, economic incentives to use waste heat in plants, targeted financing mechanisms, and assistance to enhance the capacity of TECs. External factors such as high oil prices, seismic events, and recent rising energy prices have also spurred project initiation. TECs also rely on additional factors for success, including organisational and entrepreneurial abilities to engage with stakeholders, gain social acceptance, and secure commitment from community members. Involvement from local government, intermediary organisations, and private companies is crucial for TEC implementation. Among the studied countries, Danish TECs stand out as the most developed, benefiting from a stable policy environment, decades of experience with DH and TEC, and positive societal perceptions. Conversely, Dutch and German TECs face challenges because of the early stage of their heat transition, dealing with financial obstacles, underdeveloped policies, unfamiliarity with DH technology and with TECs, as well as the need for expensive infrastructure changes. Shared challenges across regions include capacity limitations in small projects and implementing cost-effective, local, and sustainable heat sources. Conclusions In light of the study's findings, policymakers must consider establishing stable, integral and flexible policies supporting heat decarbonisation and TECs, addressing TECs' reliance on limited capacities, involving TECs in local heat municipal plans, and facilitating high DH connection rates where DH is the most cost-effective solution from a socio-economic perspective.