Calcium phosphate (CaP) bioceramics are widely used in the field of bone regeneration, both in orthopedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The aim of this article is to review the history, structure, properties and clinical applications of these materials, whether they are in the form of bone cements, paste, scaffolds, or coatings. Major analytical techniques for characterization of CaPs, in vitro and in vivo tests, and the requirements of the US Food and Drug Administration (FDA) and international standards from CaP coatings on orthopedic and dental endosseous implants, are also summarized, along with the possible effect of sterilization on these materials. CaP coating technologies are summarized, with a focus on electrochemical processes. Theories on the formation of transient precursor phases in biomineralization, the dissolution and reprecipitation as bone of CaPs are discussed. A wide variety of CaPs are presented, from the individual phases to nano-CaP, biphasic and triphasic CaP formulations, composite CaP coatings and cements, functionally graded materials (FGMs), and antibacterial CaPs. We conclude by foreseeing the future of CaPs.

Calcium Phosphate Bioceramics: A Review of Their History, Structure, Properties, Coating Technologies and Biomedical Applications.

The laser shock peening (LSP) process using a Q-switched pulsed laser beam for surface modification has been reviewed. The development of the LSP technique and its numerous advantages over the conventional shot peening (SP) such as better surface finish, higher depths of residual stress and uniform distribution of intensity were discussed. Similar comparison with ultrasonic impact peening (UIP)/ultrasonic shot peening (USP) was incorporated, when possible. The generation of shock waves, processing parameters, and characterization of LSP treated specimens were described. Special attention was given to the influence of LSP process parameters on residual stress profiles, material properties and structures. Based on the studies so far, more fundamental understanding is still needed when selecting optimized LSP processing parameters and substrate conditions. A summary of the parametric studies of LSP on different materials has been presented. Furthermore, enhancements in the surface micro and nanohardness, elastic modulus, tensile yield strength and refinement of microstructure which translates to increased fatigue life, fretting fatigue life, stress corrosion cracking (SCC) and corrosion resistance were addressed. However, research gaps related to the inconsistencies in the literature were identified. Current status, developments and challenges of the LSP technique were discussed.

/pdf/laser-peening-process-and-its-impact-on-materials-properties-1up080uvlh.pdf

Laser Peening Process and Its Impact on Materials Properties in Comparison with Shot Peening and Ultrasonic Impact Peening

Hydroxyapatite (HA) is an essential element required for bone regeneration. Different forms of HA have been used for a long time. The essence of bone regeneration always revolves around the healthy underlying bone or it may be the surroundings that give enough strength. HA is well known for bone regeneration through conduction or by acting as a scaffold for filling of defects from ancient times, but emerging trends of osteoinductive property of HA are much promising for new bone regeneration. Emerging technology has made the dreams of clinicians to realize the use of HA in different forms for various regenerative purposes both in vivo and in vitro. The nanostructured calcium apatite plays an important role in the construction of calcified tissues. The nanostructured material has the ability to attach biological molecules such as proteins, which can be used as functional materials in many aspects, and the capability of synthesizing controlled structures of apatite to simulate the basic structure of bone and other calcified tissues. The process of regeneration requires a biomimetic and biocompatible nanostructured novel material. The nanostructured bioceramic particles are of interest in synthetic bone grafts and bone cements both injectable and controlled setting, so that such composites will reinforce the strength of bioceramics. Extensive research is being carried out for bone regeneration using nanotechnology. Artificial bone formation is not far from now. Nanotechnology has made many dreams come true. This paper gives comprehensive insights into the history and evolution with changing trends in the use of HA for various regenerative purposes.

https://journals.sagepub.com/doi/pdf/10.4137/BTRI.S36138

Hydroxyapatite—Past, Present, and Future in Bone Regeneration

Directed energy deposition (DED) has matured into an essential additive manufacturing (AM) branch. DED has been broadly implemented in the design and fabrication of novel materials. These include metals, ceramics, and composites. Successful DED operation requires a good understanding of many critical phenomena, including laser-material interactions, fundamentals of casting and solidification of alloys, welding metallurgy and joining interfaces, along with microstructure-mechanical properties relations. Also critical are powder flowability, heat transfer, and various machine-related parameters. Several review articles have been published in recent years on metal AM via powder bed fusion (PBF) and DED, focusing on either a specific material system, mapping the recent technologies for AM, or issues related to the deposition process or material properties. Yet, no recent review is dedicated to a comprehensive presentation of material systems, design, fabrication, challenges, and the relationship between microstructures and mechanical properties of various DED'ed material families. Since the DED-based approach is becoming popular to manufacture bimetallic and multi-material structures, repair high-value structures, and alloy design, this comprehensive review focuses on materials design via DED, including a survey of a variety of monolithic and multi-material compositions. Finally, the critical challenges and opportunities in this area are highlighted. 

http://manuscript.elsevier.com/S0921509322003744/pdf/S0921509322003744.pdf

Laser-based directed energy deposition (DED-LB) of advanced materials

The increasing demand for orthopedic implants has driven the search for materials that combine strength, biocompatibility, and long lifetime. Compared to stainless steel and Co-Cr-based alloys, titanium (Ti) and its alloys are favored for biomedical implants because of their high strength, corrosion resistance, and biocompatibility. This comprehensive review delivers a wide overview of the field of titanium-based biomaterials for orthopedic implants applications, focusing on their types, mechanical and chemical resistance, surface modifications, innovations in fabrication techniques, titanium matrix composites, and machine learning advancements. Titanium alloys of different crystalline phases, including α, near-α, (α + β), β, and shape memory alloys, offer diverse options for orthopedic applications. Strengthening properties, wear, fatigue, and corrosion resistance are crucial factors influencing the performance and reliability of titanium implants. Moreover, this review discussed the challenges to titanium-based biomaterial durability through surface modifications to enhance their biofunction, wear resistance, corrosion resistance, and antibacterial properties. Recent developments in fabrication techniques for titanium-based biomaterials are also discussed. Eventually, this review investigated how machine learning (ML) revolutionized titanium orthopedic implants by providing insights into the behavior of new alloys, aiding in manufacturing optimization, allowing for real-time quality control, and advancing the development of personalized, biocompatible, and reliable implants. 

Titanium-Based alloys and composites for orthopedic implants Applications: A comprehensive review

This article discusses the feasibility of a new microforming technique—laser dynamic forming (LDF). LDF is a new hybrid forming process, combining the advantages of laser shock peening, and metal forming, with an ultra high strain rate forming utilizing laser shock waves. Experiments are conducted on copper foils to demonstrate this forming process. After the forming process, the mechanical and microstructure of the formed work piece will be characterized. Electron backscatter diffraction will be used to investigate the grain microstructure and misorientations quantitatively. The residual stress distributions will be measured using x-ray diffraction. The key factors for the improved formability of this high strain rate microforming process will be discussed in detail. With further development, LDF may become an important microforming technology for various materials.

Microstructure and mechanical property characterizations of metal foil after microscale laser dynamic forming

The response of solid to shock compression has been an interesting topic for more than a century. The present work is the first attempt to experimentally show that plastic deformation can be generated in brittle materials by a heat-assisted laser shock peening process, using silicon crystal as a sample material. Strong dislocation activity and large compressive residual stress are induced by this process. The dislocation structure is characterized with transmission electron microscopy and electron backscattered diffraction. The residual stress is measured using Raman scattering. This work presents a fundamental base for the application of laser shock peening in brittle materials to generate large compressive residual stress and plastic deformation for better mechanical properties, such as fatigue life and fracture toughness.

Plastic Deformation in Silicon Crystal Induced by Heat-Assisted Laser Shock Peening

A hybrid micro-nanofluidic channel network is developed on a silicon wafer for bioanalytical applications, such as separation, concentration, and fractionation. The nanochannel is formed on the silicon wafer using surface micromachining techniques, while the microchannel is fabricated on the poly-di-methyl-siloxane utilizing soft lithography techniques. Microfluidic networks not only support the very thin wall of the nanofluidic channel, but also provide appropriate gateways for the fluid/sample flow. The thickness of the microchannels is kept below 10 µm by changing the spin rate and time during photolithography. On the other hand, nanochannel thickness is varied between 100 and 200 nm by controlling the sputtering time of the sacrificial copper layer. Electrochemical wet etching is employed to release the thin layer of copper from the silicon dioxide shell. Our etching technique demonstrates significant advantages over other existing methods, such as wet chemical etching and reactive ion etching, including relatively fast etching rate, good selectivity, less safety and environmental concerns, less monitoring and control issues, and low cost. The dimensions of our microfluidic channels are measured using a profilometer, while the nanochannel thickness is confirmed by the atomic force microscopy and scanning electron microscopy images.

Design and fabrication of a hybrid nanofluidic channel

Analysis of the laser forming process has been focused on geometry, yield strength, and microstructure change in the past. However fatigue life has been the primary concern for engineering components in many applications. For laser forming to become a practical rapid prototyping tool, research has to be done to predict fatigue life of sheet metal after laser forming. Microstructure as well as the distribution of residual stresses and strains changes during laser forming process. The current models cannot predict the fatigue life after laser forming accurately because of differences in assumptions. This work presents a model to predict fatigue life of sheet metal after laser forming. Results from microstructure integrated finite element modeling of laser forming are incorporated in the fatigue life model. Low carbon steel is used in this work to validate the model. It is shown that the proposed model can predict the fatigue life of sheet metal after laser forming with good accuracy. The predictions from the model are consistent with experimental results. Effects of laser forming conditions on fatigue life of sheet metal are under investigation.

Fatigue Life Prediction After Laser Forming

In this paper, we observed and characterized changes in the microstructure and texture during recrystallization and grain growth in polycrystalline GaAs thin films using multiple pulses crystallization by a KrF excimer laser. Films of various thicknesses were studied to assess film thickness and laser energy density effects. In the low temperature domain corresponding to the partial melting regime, normal grain growth was observed. In the superlateral grain growth regime the increase in grain size was notable with grain sizes much greater than the film thickness. A bimodal grain size distribution emerged implying the onset of secondary grain growth. The change in grain size distribution, texture, and grain boundary texture were analyzed using scanning electron microscopy and electron backscatter diffraction. It was found that grain growth is accompanied by a strengthening in {001} texture, indicating that the grain growth phenomenon is strain energy driven. The experimental results are explained with theo...

Microstructure and texture developments in multiple pulses excimer laser crystallization of GaAs thin films

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