Metal additive manufacturing (MAM) is rapidly transforming the manufacturing industry by enabling the fabrication of complex, lightweight, and high-performance components. While a few researchers have explored individual aspects of MAM, such as processes, materials, and applications, there remains a critical gap in the literature regarding integrated analysis that bridges material behaviors, process optimization, post-processing, and real-world applications. This review addresses that gap by presenting a comprehensive overview of the current state of MAM technologies, evaluating the trade-offs and synergies among various methods such as selective laser melting (SLM) and electron beam melting (EBM), and detailing how mechanical properties can be enhanced through tailored post-processing and material selection. It also discusses the role of simulation, sustainability, and standardization often overlooked in prior reviews. By linking scientific development with industrial implementation, this paper offers a unified perspective to guide future innovations in the engineering application of MAM.

Bioprinting faces key challenges in achieving smooth extrusion and structural precision, especially with Polycaprolactone (PCL)-based bio-inks. Traditional approaches often fail to dynamically control flow behavior, leading to inconsistencies in scaffold quality. This study introduces a magnetostatic fluid flow approach using COMSOL Multiphysics to enhance printability by integrating a 1 Tesla magnetic field to influence bio-ink flow dynamics. The objective was to investigate how magnetic flux density (MFD) impacts pressure, velocity, and particle alignment within the nozzle. Simulations were conducted with varying magnet placements (0.8 mm to 1.4 mm from the nozzle center), revealing optimal results at 1 mm due to the close arrangement of magnets towards the nozzle. Magnetic control achieved a maximum velocity of 6.4 m/s and improved pressure uniformity, shear stress, and turbulence compared to non-magnetic conditions. Experimental validation is performed using a Gaussmeter to observe the MFD distribution, and it closely aligns with the simulation results with minimal error. Quantitatively, velocity improved by up to 27%, and pressure fluctuation was significantly reduced. These findings demonstrate the magnetic field’s role in optimizing extrusion and enhancing the integrity of the scaffold. However, to observe the real flow behaviour of bio-ink, rheological and mechanical strength validation is required. This magnetostatic technique offers a promising direction for precise, reproducible bioprinting, with future recommendations including biological corroboration and field strength optimization for broader biomedical applications.

Bioprinting represents the transformative approach to additive manufacturing, specifically in fabricating scaffolds and tissue constructs. While notable advancements have been made in fabricating organ tissues and neural tissues, challenges persist regarding optimized printability conditions, mechanical properties, and cell viability. This study uniquely integrates computational fluid dynamics (CFD) and finite element analysis (FEA) to refine bioprinting parameters and enhance scaffold performance. Advanced bio-printed techniques are investigated for their ability to produce high precision and improved cell viability. The main objective of this study is to present a simulation-driven approach to bioprinting that refines both biological and mechanical properties. A discussion is conducted about the bioprinting methods and the simulation conditions employed to optimize the outcomes of the bioprinting process. Additionally, applications of bioprinting in various fields are presented. Conclusively, integrating simulation techniques with bioprinting enhances mechanical properties and cell viability, accelerating innovation in bioprinting.

This review explores the use of magnetic bone tissue scaffolds in hyperthermia treatment. It is a therapy that heats cancer cells to damage or destroy them while minimising harm to healthy tissues. Hyperthermia leverages the greater heat sensitivity of cancer cells, potentially enhancing treatment outcomes. Bone scaffolds, typically composed of biocompatible materials like ceramics or polymers, have emerged as promising tools for hyperthermia by incorporating magnetic nanoparticles that generate heat under an alternating magnetic field. This study aims to evaluate the current advancements in magnetic bone scaffolds for hyperthermia therapy, focusing on the materials, fabrication methods, and magnetic properties that influence their performance. The review also addresses key challenges in optimising scaffold design and offers recommendations for future research to improve therapeutic efficacy. Conclusions indicate that magnetic scaffolds have significant potential for targeted cancer treatment and bone regeneration, yet further studies are needed to enhance their clinical application. This review can guide future efforts toward optimising scaffold-based hyperthermia therapies.

Many ceramic materials have become significant in the biomedical field due to their bio-compatibility, because of which it is called “bioceramics”. These materials generally have the properties of biocompatible, bioresorbable, bioactive, or bioinert, with the choice of bio-ceramic depending on their application. Characterisation techniques such as optical microscopy, surface analysis, mechanical property assessment, and chemical composition evaluation are mostly used to study these scaffolds in different literature. Bioceramics, with their biocompatibility and osteoconductive properties, have advanced bone repair and tissue engineering. However, traditional manufacturing methods often lack the precision for complex implants. 3D-bioprinting addresses this by allowing the precise addition of bio-ceramic inks to create customised scaffolds. This paper examines the improvement in the mechanical properties and biocompatibility of printed bio-ceramic scaffolds, their current uses in tissue engineering, recent developments, and prospects. This will help in choosing bio-ceramics based on intended applications with different 3D printing processes available at present.

This study explores the fabrication of bone scaffolds using a composite ink of poly-ε-caprolactone (PCL), polyhydroxybutyrate (PHB) and synthesized fluorapatite (FHAp) via response surface methodology optimization to achieve optimal Vickers hardness number (VHN). Characterization with X-ray diffraction confirms FHAp presence and increased crystallinity post-sintering, while Fourier-transform infrared spectroscopy reveals fundamental material interactions. Results show PCL’s softening effect at higher concentrations, PHB’s contribution to decreasing hardness and FHAp’s significant role in reinforcing the composite. Contour plots demonstrate peak hardness at lower PCL and PHB concentrations (<11% wt/v) with 18% wt/v FHAp. The optimum hardness values were found at PCL, PHB and FHAp of 9.754% wt/v, 9.473% wt/v and 24.608% wt/v, respectively, yielding 185.34 VHN. These findings offer insights into optimizing composite concentrations for tailored mechanical properties crucial in bone scaffold design, advancing regenerative medicine and tissue engineering.

Fiber laser welding is conducted on 0.5 mm SS-316L steel plates. Microstructural evaluation in fusion zone (FZ) of welded specimens are investigated at three different welding speeds. Autogenous welding process favors epitaxial grain growth in the FZ. The morphology of delta ferrite changed from skeletal to lathy ferrite with the increase of welding speed and further at higher welding speed of 1000 mm/min cellular structure is developed in FZ. XRD patterns demonstrate the existence of δ-ferrite in FZ at all welding conditions. The tensile properties of weldments are increased with the increase of welding speed due to the change in morphology of austenitic structure in the FZ. Ductile mode of fracture is observed in both base material and the weldments.

CLC (cellular lightweight concrete) bricks are made of CLC or Foam Concrete. It is a lightweight concrete that is produced by mixing cement and fly ash slurry with preformed foam used in residential construction buildings. This paper explores the innovative design of CLC bricks featuring a rectangular outer solid structure with internal rectangular hollow and circular porous structures. Utilizing FEA-based COMSOL Multiphysics software, a comprehensive analysis is conducted to determine the maximum deformation and compressive strength of these bricks, shedding light on their structural integrity and potential applications. Under a uniformly distributed load, deformation is primarily concentrated at the edges rather than uniformly across the surface, indicating edge susceptibility. The maximum deformation is 1.6 x 10-4 mm for the rectangular hollow block, and the minimum deformation 5.5 x 10-7 mm is obtained for the circular hollow block of 3 mm diameter.

In the current study, the state-of-the-art laser welding process of Inconel alloys are discussed in detail. The review work is mainly focused on the articles that describe the current status, challenges and relationship between the laser welding parameters and related outcomes in laser welding of Inconel alloys in similar and dissimilar configurations. Laser beam welding (LBW) offers precise welding methods, higher speed, and the potential to produce high-quality weld joints with lower deformation and minimal residual stresses in the welded parts. Laser welding is a complicated welding procedure having many controlling variables. But this process is stochastic in nature. Laser parameter is one of the critical variables which controls the weld quality. Inconel alloys belong to the Ni-Cr-based superalloy class acclaimed with remarkable properties such as exceptional strength, excellent fabricability, and corrosion resistance behavior. These alloys are significantly used in many industrial products such as gas turbine blades, aircraft, and marine components. The review highlights laser welding's advantages over conventional welding technologies like arc and gas-welding. This research paper concludes with a key challenge such as process stability, material characterization, and standardization of the laser welding process for Inconel alloys and their opportunities for future research and development.

Three-dimensional (3D) bioprinting technology enables the fabrication of porous structures with complicated and variable geometries, allowing for the equitable distribution of cells and the regulated release of signalling components, which distinguishes it from traditional tissue scaffolding approaches. In 3D bioprinting, various cell-laden materials, including organic and synthetic polymers, have been used to create scaffolding systems and extracellular matrix (ECM) for tissue engineering (TE). However, significant technological hurdles remain, including bio-ink composition, printability, customizing mechanical and biological characteristics in hydrogel implants, and cell behaviour guiding in biomaterials. This chapter investigates several methodologies for hydrogel-based bio-inks that can mimic the ECM environment of real bone tissue. The study also looks at the process factors of bio-ink formulations and printing, as well as the structural requirements and production methods of long-lasting hydrogel scaffolds. Finally, contemporary bioprinting techniques are discussed, and the chapter concludes with an overview of the existing obstacles and probable future prospects for smart hydrogel-based bio-inks/scaffolds in tissue regeneration.

This study explores recent advancements in metallizing polymer substrates for electronic applications, particularly through electroless plating with laser-assisted surface pretreatment. The demand for lightweight, flexible, and cost-effective electronic devices has spurred significant research in polymer-based electronics. Electroless plating, which involves integrating metallic layers onto polymer substrates, has emerged as a promising solution, overcoming challenges related to adhesion and compatibility. Laser treatment selectively modifies polymer surfaces, improving their receptivity to metal deposition and enhancing adhesion. Synthesizing recent studies, it examines the impact of laser-assisted surface pretreatment on morphology, chemical composition, and adhesion properties of polymer substrates. Additionally, it addresses challenges in the field, such as uniformity, reproducibility, and scalability. The integration of laser technology with electroless plating presents a synergistic approach, paving the way for multifunctional electronic devices with improved performance and durability. This comprehensive review provides valuable insights into the latest developments in polymer substrate metallization, emphasizing the role of laser-assisted surface pretreatment in enhancing the efficiency and applicability of electroless plating processes.

The field of additive manufacturing has experienced noticeable advancements with the emergence of multimaterial (MM) 3D printing methods. This chapter investigates the technologies in the realm of metamaterials, unveiling a novel avenue for engineering materials with unprecedented mechanical, thermal, and electromagnetic properties. By enabling precise control over material composition, structure, and geometry at a micro- and mesoscale level, MM 3D printing of metamaterials transcends the limitations of traditional manufacturing techniques. It reviews key breakthroughs in materials science, design methodologies, and fabrication processes that have paved the way for the creation of complex, multifunctional metamaterial structures. Additionally, the potential applications across various industries, including aviation, electronics, and medical devices, in which the tailored properties of these structures promise to revolutionize product design and performance have been discussed. As researchers continue to delve into the synergistic possibilities of MM 3D printing and metamaterial engineering, this chapter presents a comprehensive outlook of present state-of-the-art, challenges, and prospects in this rapidly evolving field.

The present study concerns the influence of hydroxyl functionalized multi-walled carbon nanotubes (MWCNTs) on the mode I interlaminar fracture behavior of carbon fiber-reinforced epoxy composites. Three different weight percentages of 0.1, 0.2, and 0.3% of MWCNTs were dispersed in epoxy resin through the sonication and mechanical mixing process. The 16-layer composite panels were made using a traditional hand lay-up method followed by a vacuum bagging process. A double cantilever beam was prepared according to the ASTM standard and subjected to a quasi-static test with a loading rate of 5 mm/min. It has been discovered that the addition of MWCNTs to bulk epoxy improves the fracture toughness of the composite proportionally. The fracture toughness for 0.1, 0.2, and 0.3% MWCNTs reinforced composites was improved by 7.9, 47.7, and 5.8% compared to the pristine composites. The improvement of the fracture strength is attributed to the improved adhesion between the fiber and matrix and the effective dispersion of carbon nanotube in the epoxy resin. The addition of MWCNTs, however, made the interface brittle, observed from the load–displacement behavior. The experimental results are validated using a bilinear cohesive zone model and confirm the improvement of interlaminar fracture toughness with the addition of MWCNTs.

Poppet valves used in internal combustion engines have a high risk of failure due to significant temperature and pressure. These poppet valves need surface finishing at the nano-scale level to prolong their life during their working use. In the present research, the chosen poppet valve has narrow ridge profiles, which is difficult to nano-finish by conventional processes due to certain limitations. The magnetorheological fluid-based finishing method can be effectively used for this kind of complicated narrow profile. For the magnetorheological fluid-based finishing processing of the poppet valve, a novel magnet fixture and setup is used. For checking the efficiency of this setup, surface characterization and surface roughness for polished and unpolished surfaces are outlined using a field-emission scanning electron microscope, microscope and optical profilometer. The final surface roughness of Sa = 23.1 nm at poppet profiles were obtained. All manufacturing defects like burrs, dents, scratches and pits are almost removed. The study of finishing forces in the magnetorheological fluid-based finishing method is also carried out using magnetostatic fluid–solid interaction, experimental and theoretical analysis. This force analysis supports the development of the material dislodgement model to anticipate material removal rate while finishing. The gap (error = 12.87%) between the experimental and theoretical material removal rate is marginal. It has high accuracy and reliability for specific applications.

The production of complex structures out of a variety of materials has undergone a revolution due to the rapid development of additive manufacturing (AM) technology. Initially confined to applications such as magnetic actuators and two-dimensional electric or electronic circuits, the convergence of 3D printing and metallization methods has emerged as a revolutionary approach. This synergy facilitates the creation of functional and customizable metal-polymer hybrid structures characterized by high strength, lightweight properties, intricate geometric designs, and superior surface finish. These structures also exhibit enhanced electrical and thermal conductivity, as well as optical reflectivity. This paper reviews techniques to improve the effectiveness of 3D-printed polymer antennas and structures by using various techniques of metallization. The metallization processes are examined, and a classification based on the materials employed is presented to facilitate comparisons that highlight the optimal utilization of materials for the fabrication of 3D-printed polymer structures. The main emphasis here is on the effectiveness of different processes in terms of deposition, bonding strength, electrical conductivity, and various characteristics of metallic coatings developed on polymers. This review contributes an in-depth analysis of the latest developments in 3D printing and metallization techniques specifically applied to polymer antennas and structures. The exploration extends to potential applications, challenges encountered, and future prospects within this dynamic field. As AM and metallization continue to evolve, this study aims to provide a comprehensive understanding of the state-of-the-art methodologies and their implications for the future of polymer-based structures and antennas.

The geometric intricacy of tiny gears makes nano-finishing difficult. In the current study, the magnetorheological (MR) polishing process is used for the nano-finishing of intricate surfaces of tiny gear components uniformly. For polishing, the technique employs a dynamic fluid recognized as magnetorheological polishing fluid (MRPF), that has the ability to stiffen in the presence of a magnetic field. Base media, iron and abrasive particles are utilized to synthesize the MRPF. Permanent magnets produce the necessary magnetic field in the finishing zone. Finite element analysis (FEA) is utilized to model the iron and abrasive particles to understand better how they would react in the external magnetic field. FEA is utilized to analyze the magnetic flux density (MFD) distributions and the amount of magnetic force exerting on gear profiles through iron particles (IPs). It has been observed that the IPs present close to the active abrasives are primarily accountable for indenting active abrasives into the workpiece surfaces. In addition, the influence of particle dimension on the stiffness of iron particle chains in MRPF has been investigated. A mathematical model for material removal is developed by utilizing normal finishing force analysis on active abrasives. Lastly, the finishing surface characteristics of gear profiles are examined using an optical profilometer, field emission scanning electron microscope (FESEM) and spectroscopic analysis. Finally, 92.68% improvement in the surface finish is observed.

Residential construction materials have undergone a notable evolution within the construction sector. This paper extensively reviews various types of bricks and building materials commonly employed in house construction, categorizing them into classifications such as typical clay, concrete, fly ash, and new materials such as aerated concrete and recycled bricks. The study thoroughly investigates the mechanical, thermal, and environmental potentials of each material, also considering auxiliary building materials like mortar, cement, and bio-materials, which play vital roles in house construction. Its primary objective is to offer valuable insights to architects, engineers, builders, and researchers to facilitate informed decision-making in residential construction projects. It also considers factors such as sustainability and local availability. The research identifies Cellular Lightweight Concrete (CLC) bricks as the optimal choice for residential construction, given their compressive strength of up to 30–40% more than traditional bricks, along with excellent lateral load capacity and displacement ductility, also making them suitable for constructing partition walls. Modifications in composition, such as incorporating coconut and basalt fibres, result in a notable enhancement of approximately 17.4% in thermal insulation with minimal impact on thermal degradation. Ultimately, this review serves as a valuable reference for individuals seeking a deeper understanding of the diverse options available in bricks and building materials for modern residential construction.

Bone tissue engineering relies on scaffolds with enhanced mechanical properties, achievable through 3D printing techniques. Our study focuses on enhancing mechanical properties using a solvent-cast 3D printing method. For this, poly-ε-caprolactone (PCL) reinforced with polyhydroxybutyrate (PHB), and synthetic fluorapatite (FHAp) nanopowders were utilized, immersed in a solution of dichloromethane (DCM) and dimethylformamide (DMF). Sol–gel method was used to synthesized FHAp, and the XRD pattern confirmed crystalline FHAp presence, with notable peaks at 2θ values of 31.937°, 33.128°, 32.268°, and 25.864°. Moreover, composites exhibited nonchemical PCL-PHB/FHAp interactions, with PHB and FHAp crystallographic planes evident. Surface roughness, assessed via RMS values, showed progressive increases with higher PHB and FHAp content. Tensile strength peaked at 19% wt/v of PHB, with varied effects of FHAp. Compressive strength reached its apex at 30% wt/v of FHAp, with higher PHB content consistently enhancing strength. Flexural strength notably increased with PHB, peaking at 19% wt/v, and further with FHAp. Young's modulus rose with both PHB and FHAp content. Hardness increased with PHB and FHAp, notably peaking at 30% wt/v of FHAp. Cell viability improved with PHB, showing varied responses to FHAp. Hemocompatibility evaluations indicated low hemolysis percentages, especially in balanced PHB/FHAp compositions. These findings highlight the crucial role of composite compositions in tailoring mechanical and biological properties for optimal bone scaffold design, promising advancements in tissue regeneration technologies.

Three-dimensional (3D) bioprinting technology allows the production of porous structures with complex and varied geometries, which facilitates the development of equally dispersed cells and the orderly release of signal components. This is in contrast to the traditional methods used to produce tissue scaffolding. To date, 3D bioprinting has employed a range of cell-laden materials, including organic and synthetic polymers, to construct scaffolding systems and manufacture extracellular matrix (ECM). Still, there are several challenges in meeting the technical issues in bio-ink formulations, such as the printability of bio-inks, the customization of mechanical and biological properties in bio-implants, the guidance of cell activities in biomaterials, etc. The main objective of this article is to discuss the various strategies for preparing bio-inks to mimic native tissue's extracellular matrix environment. A discussion has also been conducted about the process parameters of bio-ink formulations and printing, structure requirements, and fabrication methods of durable bio-scaffolds. The present study also reviews various 3D-printing techniques. Conclusively, the challenges and potential paths for smart bioink/scaffolds have been outlined for tissue regeneration.

This study aims to enhance the mechanical properties of 3D-printed scaffolds by optimizing a composite of Poly-ε-caprolactone (PCL), poly-hydroxybutyrate (PHB), and synthetic fluorapatite (FHAp) using Response Surface Methodology (RSM). The research targets the intricate relationships between PCL, PHB, and FHAp concentrations, crucial for achieving optimal tensile, compressive, and flexural strengths. The solvent-cast process successfully yielded FHAp-reinforced PCL composites, confirmed by XRD and FTIR spectra. The findings indicate that an optimal PHB content of over 15 % wt/v and PCL under 10 % wt/v significantly enhance tensile strength, achieving values up to 48 MPa. Compressive strength peaked at PHB concentrations of 13–16 % wt/v and PCL concentrations of 9–13 % wt/v, showcasing effective stress transmission, with the highest recorded value being 90 MPa. Flexural strength exceeded 100 MPa with lower concentrations of PCL and PHB, emphasizing the need for a balance of rigidity and flexibility. The study identifies the optimum composition for these mechanical properties at PCL 9.432 % wt/v, PHB 16.568 % wt/v, and FHAp 24.933 % wt/v, crucial for advanced biomedical implant applications.

The current study is concerned with the effect of friction stir welding (FSW) on the mechanical properties of aluminium alloy (AA1100). The FSW process was carried out using two rotational speed values—1100 rpm and 1500 rpm at a constant weld speed of 98 mm/min. The standard tensile and fracture (compact tension) specimens were prepared and subjected to mechanical tests to study the load–displacement behaviour and determine the fracture toughness of the FSW samples. In tensile tests, the ultimate tensile strength of the specimen was found to decrease by 12.6 and 31.8% at 1100 rpm and 1500 rpm, respectively. In the case of fracture tests, the estimated fracture toughness of the friction stir (FS) welded CT specimens was 97.24% for 1100 rpm and 85.62% for 1500 rpm, respectively, compared to the base metal specimen's fracture toughness. In addition, the fractographic analysis of failures with SEM revealed two types of surface textures. Whilst the base material fractured surface was made up of rough surface textures with voids and dimples, the surfaces of the welded samples for both the rotational speeds were granular, with more pronounced peaks and valleys.

Tiny gears play a critical role in the transfer of power in smaller machinery used in the aviation, automobile, and biomedical sectors, etc. Nano-finishing tiny gears is a tough job owing to their geometry’s intricacy. Precise finishing of small gear increases its life and performance. To impart nano finishing on small gears, it is necessary to remove faults on gear’s working surfaces due to manufacturing. The faults include scratch marks, burrs, and pits. Very few finishing processes are applied to small gears due to the narrow spacing between the gear teeth. The rotational magnetorheological abrasive flow finishing process is a magnetorheological polishing fluid-based finishing process which delivers nanometer-level finishing. In the present study, this process is employed to nano finish small steel gear. This problem is addressed by developing gear workpiece fixture and synthesizes optimum polishing fluid in the finishing process. Wire electro discharge machining is used to manufacture the steel gear. After finishing the steel gear, minimum surface roughness of 34.5 nm is achieved. Maximum percentage improvement of surface roughness at involute profile of gear workpiece is obtained as 85.56%. Also, manufacturing defects are removed after the finishing process. After analyzing the finished surface, it is observed that recast layer on the ground surfaces is totally removed after the finishing procedure.

Milling of stainless steel workpiece by conventional process is very challenging as the tool wear and design of tool for complex shapes are very critical and also machine at low rate. The surface finish and the machining accuracy obtained during conventional milling are not good. To overcome these limitations, electrochemical milling is very good alternative. It is a non-conventional process which removes material atom by atom from the layer of the workpiece same as electrochemical machining. As it is non-contact process, the accuracy of the tool surface replicates on the workpiece. Various process parameters enhance the accuracy of milling. In this paper, ‘L’ shape profile has been milled over the stainless steel 316L of thickness 3 mm with copper rod of diameter 5 mm. An electrochemical milling setup is indigenously developed to perform the experiments. The effect of tool rotation over the machining depth, surface roughness and overcut has been studied. The result shows that the rotary tool enhances the machining depth and surface finish and decreases the overcut of the electrochemical milled surface. The surface roughness value for the milling layer depth of 0.15 mm and tool feed of 8 mm/min with tool having the 500 rpm is 0.072 µm.

Electropolishing (EP) is a non-traditional polishing method which is governed by Faraday’s law of electrolysis. An experimental setup is design and developed to perform the EP of maraging steel. EP removes some layers of material from the surface to achieve a mirror finish polish surface. In this paper, a simulation of 2D model is developed to predict the thickness of material removed from the workpiece surface during EP to achieve mirror like surface finish. A finite element-based COMSOL software is used to design the model for EP. A comparative analysis of thickness removal from experiment and simulation is done. The measured thickness of material removed is 13.16 µm and 14.51 µm from experiment and simulation, respectively. The surface roughness, Ra is also measured and it is 0.276 µm before EP, which reduces to 0.107 µm after EP, an improvement of about 61% is observed.

Nowadays, the surface quality of the material is crucial for industry and science. With the development of micro-electronics and optics, the demand for surface quality has become more and more rigorous, making optical surface polishing more and more critical. Plasma polishing technology is conceived as an essential tool for removing surface and subsurface damages from traditional polishing processes. The plasma processing technology is based on plasma chemical reactions and removes atomic-level materials. Plasma polishing can easily nano-finish hard-brittle materials such as ceramics, glass, crystal, fused silica, quartz, Safire, etc. The optical substrate with micro-level and nano-level surface roughness precision is in demand with the advancement in optics fabrication. The mechanical properties of super-finished optics materials are being used to fulfill the requirement of modern optics. This article discusses the processing of different types of freeform, complex and aspheric optical materials by the plasma polishing process used mainly by the optical industry. The plasma polishing devices developed in the last decade are thoroughly reviewed for their working principles, characteristics and applications. This article also examines the impact of various process parameters such as discharge power, rate of gas flow, mixed gas flow ratio and pressure on the plasma polishing process.

As a thermochemical conversion process, biomass pyrolysis has received a lot of interest for energy recovery by generating clean fuels, valuable compounds, and advanced materials. Innovative and novel pyrolysis procedures have arisen over time, and these processes may be optimized to produce high-quality end products. Substantial progress has been achieved in the development of analytical pyrolysis systems during the last few decades. However, due to a lack of knowledge of the reaction process, the current mechanism of biomass pyrolysis, as well as its economic feasibility, is far from a complete and thorough explanation. This review systematically covers biomass pyrolysis for energy recovery, the most recent advances in biomass pyrolysis, and the numerous factors responsible for the end products. Furthermore, the various feedstock compositions, as well as the techno-economic analyses, have also been reported. This review emphasizes discernment into future paths, intending to overcome existing deficiencies. This review may also be employed to get new insights into this field and be useful for future studies on biomass pyrolysis.

Smart materials, by definition, are those materials whose properties change by changing an external factor such as electric current, magnetic field, capacitance etc. One such material is magnetorheological fluid. Magnetorheological fluid is a class of fluid whose apparent viscosity varies over changing magnetic flux density in the range of magnitude 1 T. Without magnetic field, magneto-theological fluid functions as a Newtonian fluid but shifts its essence to that of a non-Newtonian fluid when subjected to a magnetic field. One of the models that depict the behaviour of magnetorheological fluid is Bingham plastic fluid. Similar to Bingham plastic, magnetorheological fluid needs a certain amount of yield stress before it starts to flow, and this certain yield stress relies on the degree of the magnetic flux density applied. Magnetorheological fluids are prepared by dispersing micron-size magnetizable iron particle in a non-magnetizable solution such as deionized water, silicone oils, synthetic hydrocarbons etc. Additives such as greases are often applied to avoid sedimentation and coagulation of material. Through adding the magnetic field, the magnetizable iron particles are tied collectively in chains, along magnetic field lines, and these chain-links thicken the fluid. Conventionally magnetorheological fluids were used in rail locomotive engines, dampers, shock absorber, clutches etc. In the recent decade, magnetorheological fluids are extensively used in the manufacturing industry for finishing purposes. Certain contours, an internal section of pipes etc. are difficult to finish with other methods. Since fluid can flow within internal and hard to reach places, this can be and is manipulated. Magnetorheological fluids mixed with abrasive particles are used for such purposes. This article discusses the preparation, formulation, rheological properties and engineering applications of magnetorheological fluid in details.

Predicting failure in composite materials under service loading conditions has been challenging due to the non-uniform mechanical properties arising from the composite fabrication process. Including these uncertainties in the analysis becomes critical. The probabilistic approach plays a vital role in making the design less conservative and anticipates the risk associated with the design incorporating the uncertainties. In this work, metamodels such as support vector machines, radial basis function, and logistic regression in conjunction with Latin hypercube, Sobol, and Halton sequence sampling methods were used to calculate the failure probability in the carbon fibre/epoxy-based composite material. Here, the composite plates were fabricated using the vacuum-assisted resin transfer molding (VARTM) process. The variation in the fibre-volume fraction was evaluated at different sites of the composite plate. Then, the effective orthotropic properties of the composite for various fibre-volume fractions have been numerically computed by the homogenisation method using periodic boundary conditions. A double cantilever composite beam problem was considered to predict the failure probability by including the uncertainties in single-source — fibre-volume fraction and double-source — fibre-volume fraction and fracture toughness. At the end, a study to ascertain the metamodels stability was presented to demonstrate the accuracy and effectiveness of the proposed approach.

Surface quality is a critical factor impacting the durability and functionality of products. The conventional method of finishing causes many manufacturing defects in the final product. Conventional finishing approaches are not preferable for complex irregular surfaces due to inadequate controlling forces and machine movement constraints. There are two kinds of advanced finishing techniques: the first one uses magnetic fields, and the others do not. The first type covers magnetic abrasive finishing, magnetorheological (MR) finishing, and related methods, and the other one involves abrasive flow machining with a flexible system. For ultra-fine finishing of complex free-form products, the choice of polishing particles in these finishing methods performs an essential part. This article discusses different developments and modes of operation of instruments based on advanced abrasive-based finishing methods. The advanced abrasive-based devices studied over the last decade will be thoroughly reviewed, discussing their principles, challenges and applications. This article further emphasizes the detailed study related to MR polishing fluid and AFM media. Finally, the application prospects for these advanced finishing methods for polishing different complex free-form components made of various materials are discussed.

Electrochemical micromachining (EMM) is an anodic dissolution process which governs by Faraday's laws of electrolysis. The accuracy of the machining de-pends on the tool design as the streamline of current density formed in between the tool and the workpiece (electrodes) depends on it. In the present paper, two different tool-tips namely flat and ball end are considered for investigation. The complete set-up is modeled in the COMSOL Multiphysics® software coupling electrochemistry and fluid flow. The current density develops during EMM for both the tool-tips are used for analysis. The tool material is tungsten and work-piece material is stainless steel. Keeping parametric conditions constant for the two, simulation was performed. It was observed that more uniform current developed for ball end compared to flat end. It leads to a decrease in overcut of 120 µm in ball tip than the flat end. The fluid flow shows flushing of debris particles from the interelectrode gap is more effective in ball end than the flat end tooltip.

Miniature gears are used in the biomedical, automotive, and aerospace industries for advanced automatic transmission. Significantly few finishing processes can be utilized to finish miniature gears due to the narrow spacing between the miniature gear teeth profiles. In the present study, a novel uniform flow restrictor, an exact negative replica of the miniature gear teeth profiles, is designed and developed while using the rotational magnetorheological fluid-based finishing process. The effect of critical parameters on the process’s performance has been studied through response surface methodology (RSM). The surface roughness and surface texture of the finished gear profiles with different magnetorheological fluids with and without using flow restrictors are compared for consistent and precise finishing. After finishing, it is observed that all manufacturing defects in SS316L miniature spur gear are entirely removed. Also, the ultrafine surface roughness of 23.9 nm (Ra) is achieved using a uniform flow restrictor at miniature gear teeth profiles. The forces responsible for finishing gear profiles are also simulated using Comsol® Multiphysics for understanding the controlling mechanism correctly. A mathematical model for material removal using abrasive grains on gear profiles is carried out to anticipate material dislodgement mechanism during finishing.

Emerging finishing trends and increasing demand have resulted in the manufacture of nanofinished optical products, such as navigation-grade inertial sensors (accelerometers and gyros), x-ray optics, laser fusion optics, and large-scale telescopic lenses. Plasma polishing is an effective technique for nanofinishing hard and brittle materials such as crystal, fused silica, quartz, sapphire, glass, etc. A non-contact plasma polishing method removes materials from the workpiece by generating reactive radicals that interact with the substrate surface atom. This chapter explores an approach to bridge the gap between micro and nanofinishing observed in the plasma polishing of components. An in-depth discussion detailing the mechanism of plasma polishing for various types of complex freeform, and aspheric optical materials, which are primarily used by optical industries, is presented. Also, Comsol simulation of the plasma polishing process is included. Further, optical polishing challenges are also highlighted.

Poppet valves are commonly used as relief valves, pressure regulators, selectors, and inlet and exhaust valves in automobile internal combustion (IC) engines. Nanofinishing of ridge profiles of the poppet valve is a challenging task due to its narrowness. This article presents the precise finishing of narrow ridge profiles of poppet valves at optimum process parameters in the rotational-magnetorheological fluid-based finishing (R-MRFF) process using a novel magnet fixture. Statistical analysis is used to determine the impact of each process parameter. Further, simulation of finishing forces in the R-MRFF process is performed using software that applies the finite element technique. Investigation of finishing forces assists in controlling the process precisely. An analytical model is formulated for calculating the number of abrasive particles acting on nickel–aluminum–bronze alloy poppet profiles to anticipate final material dislodgement. The significant process parameters for surface roughness are abrasive volume concentration, poppet rpm, poppet vertical feed rate, and carbonyl iron particle (CIP) volume concentration. The minimum obtained surface roughness (Ra) at poppet valve profiles is 23.5 nm. The final finished poppet valve may have a longer service life and improved wear and corrosion resistance at maximum temperature and pressure.

Nano-finishing of miniature gear is a tough job since its geometry is complex. Traditional gear finishing methods can cause burns, micro-cracks, scratch marks, burrs, pits and thermal distortion in gear teeth profiles. Because of the limited spacing between the gear teeth, miniature gears can only be finished with a few processes. This article reports on the new uniform flow restrictor used in the rotational magnetorheological fluid-based finishing (R-MRFF) method to ensure a consistent and precise polishing of gear profiles. The uniform flow restrictor is analyzed using a commercial software program (COMSOL® Multiphysics) focused on finite element analysis (FEA). The surface roughness simulation is also performed using the results of the FEA and force analysis on active abrasives. The simulated roughness values are consistent with experimental values. Later, the experiments are performed without and with a novel uniform flow restrictor on the SS316L spur gear teeth profile to examine and compare the finishing performance. After finishing the gear, the minimum surface roughness of Ra = 23.9 nm at the tooth profile is achieved, and further, all manufacturing defects are entirely removed. Concurrently, the teeth geometry profiles are not affected. The uniform finishing of miniature gear with a continuous smooth surface may improve its work performance, transmitting power ability, reliability, fatigue life and form accuracy.

The traditional finishing method causes form inaccuracy in miniature gear profiles due to the transverse grinding line, fine microcrack, claw-mark, burr, pit and thermal distortions. Because of the small space between their teeth, tiny gear can only be polished in a very few ways. This article reports on the new flow restrictor used in rotational-magnetorheological miniature gear profile polishing (R-MRMGPP) process for precise polishing of miniature gear profiles. The response surface method (RSM) is utilized to investigate the effect of key factors on process performance. Further, simulation of finishing forces is conducted using COMSOL® Multiphysics software, which is based on finite element analysis (FEA). The study of finishing forces assists in accurately understanding the processing mechanism. A model is also simulated to determine the depth of indentation produced by an abrasive on SS316L miniature gear tooth profile due to normal finishing forces. Experimental results identified that combining a higher number of finishing cycles, a lower volumetric proportion of iron/abrasive particles, and a higher extrusion pressure is more favourable to obtain high material removal rate (MRR).

Precise finishing of the poppet valve profile will make it perfectly fit on its seat in the aerospace gas propulsion engine to reduce hydrocarbon emissions. Nano-finishing of poppet valve narrow profiles is a particularly challenging job. This article reports on the uniform polishing of the poppet profiles using a novel magnet fixture used in the rotational-magnetorheological fluid-based finishing (R-MRFF) method. The precise finishing of the Nickel aluminium bronze (BS1400 Gr. AB2) (excellent corrosion resistance and bearing properties) poppet profiles is done through various compositions of magnetorheological polishing (MRP) fluid. After performing the experiments, surface characterization and material compositions are outlined for both polished and unpolished poppet profiles. Magnetostatic simulation is also performed to observe the distribution of magnetic flux density along poppet valve profiles. This magnetostatic analysis will help in understanding the finishing mechanism properly. Ultrafine surface roughness (Ra = 21.3 nm) at poppet profiles are obtained using an MRP fluid of Type ‒ 2. All manufacturing defects are almost removed from the poppet valve profiles.

Surface finishing is essential for various applications in the aerospace industry. One of the applications is the poppet valve, which is used for leak-proof sealing of high-pressure gases in aerospace gas propulsion engines. The combustion engine also typically employs a poppet valve as an intake and exhaust valve. Nano-finishing a poppet valve is difficult because of its complex narrow profile. The precise nano-finished poppet valve perfectly fits on its seat and reduces hydrocarbon emissions. The rotational–magnetorheological fluid-based finishing process can be used effectively for these complicated surfaces. The polishing agent in this process is magnetorheological fluid, and rheological properties are controlled by a permanent magnet. This article presents the uniform finishing of the poppet valve's narrow ridge profile, which is analyzed through finite element analysis (FEA), wherein the outcomes are uniform shear stress, normal stress, and magnetic flux density distributions along the poppet ridge profile. The study of forces exerting on abrasive grains and surface roughness simulation is also conducted using FEA findings. The experiment is subsequently performed to verify the simulation results for poppet profile polishing. The obtained experimental and simulated surface roughness values are comparable. After the finishing process, the maximum percentage improvement of surface roughness is obtained as 93.71%. The rotational–magnetorheological fluid-based finishing process has high accuracy and reliability for specific applications.

Surface quality is the most crucial factor affecting the product lifespan and performance of any component. Most earlier technologies display accuracy in the micrometre or submicrometre range, surface roughness in the nanometre range, and almost no surface defects in the production of optical, mechanical and electronic parts. Such finishing methods incorporate a magnetic field to control the finishing forces using magnetorheological fluid as the polishing medium. Magnetorheological fluid (MR) consists of ferromagnetic and abrasive particles. It is a type of modern intelligent fluid. An optimum selection of magnetorheological fluid constituents and their volume concentration plays an essential role for the ultra-fine finishing of newly developed engineering products. Rheological characteristics of magnetorheological fluid can change rapidly and effortlessly with the support of an activated magnetic field. Traditional finishing methods are comparatively inferior in finishing complex freeform surfaces, due to the lack of controlling finishing forces and limitations of polishing tool movement over the complex freeform contour of the components. There are different types of processes based on the magnetorheological fluid including magnetorheological finishing, magnetorheological abrasive flow finishing, rotational magnetorheological abrasive flow finishing and ball end magnetorheological finishing. This article discusses the development of different types of magnetorheological-fluid-based finishing processes and their modes of operation. The MR fluid devices developed in the last decade are thoroughly reviewed for their working principles, characteristics and applications. This article also highlights the study of rheological characterization of magnetorheological fluid and its applications in different polishing methods appropriate for finishing various complex freeform components.

Electrochemical micromachining (EMM) uses anodic dissolution in the range of microns to remove material. Complex shapes that are difficult to machine on hard materials can be fabricated easily with the help of EMM without any stresses on the workpiece surface and no tool wear. Fabrication of microfeatures on microdevices is a critical issue in modern technologies. For the fabrication of microfeatures, precise micro-tools have to be fabricated. In this present study, EMM milling is used for the fabrication of micro-tools. For this, an EMM setup has been designed. Tungsten carbide tools with an initial diameter of 520 µm have been selected and are electrochemically machined to reduce their diameter. The tool and workpiece are connected as anode and cathode, respectively. The electrolyte solution used for this investigation is sodium nitrate. A comparative analysis of the effect of tool rotation over both machining accuracy and surface finish has been performed.

Ultrafine glass–ceramic polishing is very challenging due to structural inconsistencies, chemical inhomogeneity and high stiffness. In the modern optics sectors, glass–ceramics are extensively used. In the present study, two different experimental setups of rotational-magnetorheological glass–ceramic polishing (R-MRGP) process are used to super-finish the complex freeform curved profiles of the glass–ceramic workpiece. After polishing, the performance of both R-MRGP process setups is compared in terms of uniformity in surface roughness, surface reflectance characteristics, surface topographical images and material removal rate (MRR). Further, magnetostatics fluid-flow analysis is performed for both R-MRGP process setups to study the distributions of magnetic flux density (MFD), axial velocity and shear stress along the glass–ceramic profile. This finite element analysis (FEA) helps in recognizing the polishing capability of R-MRGP process setups. In the current study, finishing force analysis is also performed to develop a theoretical model for predicting and comparing the obtained MRR in both R-MRGP process setups. The final outcome demonstrates that the workpiece has an excellent surface quality, with a minimum achieved roughness of 1.91 nm after using the R-MRGP process setup-II. The versatility of the R-MRGP process makes it a viable option for ultra-precision polishing of glass–ceramics.

Surface quality is a key parameter affecting product life and functionality. Most of the technologies have been produced in the past that can be used for a micrometre or submicrometre accuracy, nanometer surface roughness and almost no surface defects in the production of optical, mechanical and electronic products. Such technologies for finishing have been divided into two types: including and not including magnetic field support. These processes having flexible finishing tool that can be employed for complex freeform components effectively. In the case of finishing complex freeform surfaces, traditional finishing methods are comparatively inferior in performance due to the lack of controlling finishing forces and limitations of polishing tool movement over the components' complex freeform contour. Surface conditions of biomedical components (knee joint, hip joint, elbow joint, heart valve, dental crown etc.) decide the life and functionality of the implant. Generally, implants are made from skin, bone or other body tissues and also metals, plastics, ceramics or other materials. Abrasive finishing is a non-traditional finishing technique that offers better finishing accuracy, performance, consistency and economy. This article discusses the published works on fine finishing of biomedical implants to improve their functionality and surface quality through abrasive based finishing methods, including abrasive flow machining, magnetorheological fluid-based finishing, magnetic abrasive finishing, etc.

Nowadays, every component is getting miniature. For machining of these micro components, micromachining have to be performed either on soft or hard materials. To machine at micron range, the tool has to be also in the micron range. But the fabrication of the tool at the micron range is very challenging because of its size, shape, strength, etc. Several researchers have utilized non-conventional machining to fabricate microtools using different techniques such as Electrical discharge machining (EDM), Electrochemical machining (ECM), Focused ion beam machining (FIB), etc. In this paper, a detailed explanation of all these processes for the fabrication of micro tools has been discussed with the advantages and disadvantages associated with these processes. The shape and size of the fabricated microtool are also discussed with their applications.

Small gears are an integral part of the transmission of power and other devices in the small machines which are employed in aerospace, automotive and medical industries etc. Nanofinishing of small gear is a difficult task due to the complexity in its geometry. The modern hybrid approach for the development of nano-scale surface finishing is magnetorheological abrasive flow finishing (MRAFF) method. These surfaces decrease friction among meshing components to improve the their service life. A model for simulating the effects of the MRAFF method was built in the current research study by using FEA based software i.e. (COMSOLÒ Multiphysics). Computational fluid dynamic (CFD) analysis of MR fluid in the 2D computational domain is conducted to see the effects of different process variables on the fluid flow properties (shear rate, shear stress, velocity profile) while finishing the gear component. To analyze the forces acting in the MRAFF method, a viscosity model for the magnetorheological polishing (MRP) fluid flow around a complex component (small steel gear) in external magnetic field is identified and simulated. The magnetic field significantly affects process efficiency by regulating the MR fluid viscosity. The surface finish achieved at various positions on the workpiece surface is consistent throughout the finishing of the gear component.

An electrochemical micromachining (EMM) removes material via anodic dissolution. Several parameters affect their machining rate as well as accuracy. Analyzing these parameters and their effects via experiments is very rigorous and time-consuming. The simulation study helps in better prediction of the parameters as well as saves time. In this paper, different parameters and their effects are analyzed during machining. A three-dimensional model is formed by making an electrolytic cell with a tungsten carbide micro-drill tool as a cathode and SS-316L as the anode surface with sodium chloride as an electrolyte. From the simulation results, it is found that on increasing the voltage and concentration of the electrolyte, material removal rate (MRR) increases. The current density decreases on increasing the interelectrode gap (IEG). A non-uniform behavior of current density is observed during EMM. The simulation results for the effect of voltage and concentration of the electrolyte over MRR is validated with the experiments. The deviation of simulation results from the experimental results is around 15%.

Miniature gears are essential components of transmitting power in tiny motors used in the aviation, automobile, and healthcare sectors etc. Because of the intricacy of its shape, nanofinishing of tiny gear is a tough job. The rotational magnetorheological abrasive flow finishing (R-MRAFF) technique is a new hybrid methodology for the generation of nanometer range surface finishing. These surfaces reduce friction between integrating parts, extending their life span. In the current study, a model for simulating the impacts of the R-MRAFF technique was developed using finite element (FE) analysis software, namely COMSOL® Multiphysics. The impacts of various process factors on the fluid flow characteristics while finishing the gear component are investigated using magnetostatic fluid flow analysis of magnetorheological polishing fluid (MRPF) in 3D computational domain of new workpiece fixture. To evaluate the forces operating in R-MRAFF technique, a viscosity model for MRP fluid flow around a complicated component (small steel gear) in an outside magnetic field is recognized and simulated. The magnetic field has a major impact on processing effectiveness by controlling the MRPF viscosity. During the polishing of the gear component, the surface finish attained at various places on working surfaces is uniform, which is confirmed by surface characterization of teeth profiles of small gear.

Micro electrical discharge machining (EDM) can be used to fabricate micro rods and these rods are widely employed for drilling of single, multiple as well as arrays of micro holes. Various application in real life where can be commonly used such as perforated shadow mask, semiconductor device, and micro heat exchanger, etc. In the present investigation, grey relational analysis (GRA) has been proposed to optimize the multi-response performance characteristics (i.e., machining time and tool wear rate) of the process. GRA and Taguchi methodology are applied to optimize fabrication process of micro rods to obtain the better dimensional accuracy with minimum tool wear and machining time using reverse micro EDM (R-μEDM) process, a variant of Micro EDM process. In Micro EDM, tool wear and machining time are directly influence the dimensional accuracy of the micro rods. The dimensional accuracy can be improved by reducing the tool wear and machining time during the fabrication process. The experimental investigation considers voltage, capacitance, and feed rate as input parameters. GRA optimization result shows that voltage of 80 V; feed rate of 10 μm/sec; and capacitance of 1000 pF are found as the optimum process parameters. The voltage contributes 58.28% being highly influenced, followed by capacitance (17.63%) and feed rate (10.63%). Voltage and capacitance having the statistical significance of 95% confidence level on overall performance towards the response parameters for getting the better dimensional accuracy with minimum time duration.

The characteristics of the surface and substrate have a significant role in the life and efficiency of the optical device. COMSOLÒ Multiphysics is a software program, which is applied to model the radio frequency (RF)-excited dielectric barrier for helium (processing gas) and oxygen (reactive gas). The software is flexible enough to accommodate multiple partial differential equations (PDEs) in a single domain model. This Multiphysics software is focused on finite element modelling program. The composition of the gas, the pressure, the configuration of the electrodes, and the excitation power of the RF are analyzed with regard to the formation of oxygen radicals and their consistency of allocation in the chamber. A computer program has been established to plan and optimize the microwave plasma physics utilized for the polishing of the surface of an optical specimen. The COMSOLÒ Multiphysics software is used for the simulation of microwave plasma coupled with an electromagnetic wave. COMSOL can easily simulate multiphysics problems. In the current study, a new method of producing Helium and Oxygen by microwave plasma is researched, evaluated, and simulated. The results show the distribution of density, temperature, and potential of electrons for two different specimens in the plasma chamber.

In this article, a new flow restrictor is utilized in the magnetorheological miniature gear-profile polishing (MRMGPP) method to ensure a consistent and precise polishing of gear profiles. The effectiveness of flow restrictor is analyzed using a finite element-based software COMSOL® Multiphysics, where shear stress and axial velocity distributions are studied along gear profiles. Later, the experiments are performed without and with using a novel flow restrictor on the SS316L miniature gear teeth profile to examine the finishing performance and results are compared with each other. After finishing the gear, the minimum surface roughness of 24.1 nm at involute profile is achieved, and also all manufacturing defects are completely removed. Concurrently, the teeth geometry profiles are not affected. The uniform finishing of miniature gear with a continuous smooth surface may improve its work performance, transmitting power ability, reliability, fatigue life and form accuracy.

Nano-finishing of small-scale gears is difficult because their geometric complexity is really challenging. The high-speed application causes noise or vibration between the meshing teeth. The traditional method for finishing of tiny gears produces a surface error on its profiles. Very few finishing processes can be applied to SS316L tiny gears due to the narrow spacing between their teeth. In the current study, the stainless-steel tiny gear teeth profiles are polished using a novel flow restrictor by the magnetorheological-polishing fluid-based finishing process. The minimum ultrafine surface roughness Ra of 23.9 nm at tiny gear teeth profiles is obtained. All surface defects like burrs, dents, scratches and pits are also completely removed. The finishing results are compared with and without using a flow restrictor. A theoretical analysis of the magnetic force responsible for finishing is also done to recognize the process accurately.

The study of surface texturing has been a great interest to the researcher over the last years. Surface texturing improves the property of the surface of the material in the working area. It creates a pattern of micron dimensions over the surface to influence the surface property in its working area. Several techniques are used to fabricate these micro dimensions. Electrochemical micromachining (EMM) emerges as a new technique with several benefits. This review paper highlights the advantages of EMM over other processes and discusses different methods to develop the micro-features. EMM process is capable of fabricating micron-size features without changing any surface property at a low cost.

The present workis focused on compacting, sintering, and characterization of sintered magnetic abrasive particles, which is composed of equal volume fraction of alumina and carbonyl iron powder. Powder metallurgy method is a well-developed technique for manufacturing of ferrous and nonferrous parts. AhO3-CIP composites are prepared through powder metallurgy method. Ball milling is used for mixing powders, and hydraulic Jack with die is used for compacting purpose. Solid and liquid phase sintering is performed at a high temperature tubular furnace under an inert gas atmosphere of argon. Solid and liquid phase sintering is done at 1000C and 1545C, respectively in proper consecutive sintering cycle. After sintering, the sintered pallets are crushed using ball miller to obtain the required size of the sintered powder. Energy Dispersive X-ray spectroscopy is used for elemental composition of all sintered powders. Vibrating sample magnetometer is used to see the magnetization of the particles. The saturation magnetization of the sintered abrasive obtained at 9-ton compaction pressure is found to be highest. Different phases of all prepared samples are studied using the X-ray diffraction technique. The morphology, as well as particle size, are studied using a scanning electron microscope. Also, the microstructure of sintered powders is studied using an optical microscope. Compression strength test of all sintered pallets is carried out using Universal Testing Machine. Bulk density of the pallets is measured using standard Archimedean principle. It is observed that the bulk density value increases with the compaction load. Micro hardness of the sintered pallets is measured using a Vickers micro hardness measuring instrument. The sintered pallet, fabricated at a compaction pressure of 9 ton shows the highest hardness.

Magnetorheological finishing method is carried out in order to correct errors of figures which are produced by conventional polishing methods on planes, spheres, aspheres and freeform optics having surface roughness value as low as 1 nm RMS. Low surface roughness and mid-spatial frequencies in advanced optical systems are essential for minimizing flare and energy loss. Magnetorheological polishing fluid is a clever fluid that can alternate from its liquid phase to almost solid under magnetic field influence. The main key process parameters in magnetorheological finishing process such as fluid composition, rheological properties along with the surface quality of polished optical components (including metal, glass, and ceramic) are reviewed in the present manuscript.

Biomass is a renewable and sustainable energy source. Co-firing of biomass with coal will increase the renewable energy share by decreasing the coal consumption. In the present paper, hydrodynamic behaviour of coal and biomass mixture is investigated in a fluidized bed reactor. A Computational Fluid Dynamic (CFD) model is developed and the hydrodynamic behaviour of gas and solid is investigated in detail. The CFD model is based on Eulerian-Eulerian multiphase modelling approach where the solid phase properties are obtained by applying the Kinetic Theory of Granular Flow (KTGF). Six different weight percentages of coal and biomass (100:0, 95:5, 90:10, 80:20, 70:30 and 50:50) are used for the present study. The hydrodynamic behaviour is analyzed in terms of the important hydrodynamic parameters like bed pressure drop, bed expansion ratio, particle volume fraction distribution and velocity distribution. The numerical model is also validated by comparing some of the numerical results with our own experimental data generated in a laboratory scale bubbling fluidized bed reactor.