Dispersion Of Ceramic Particles Research Articles

Laser-powder bed fusion of Y2O3 nanoparticle modified CoCrNi matrix composites: Parameter optimization, microstructural evolution and strengthening mechanisms

Laser-powder bed fusion (L-PBF) delivers significant advantages in manufacturing metal matrix composites due to its micro-sized molten pool and fast cooling rate. In this work, a simple two-step process including the ultrasonic dispersion of ceramic particles and the volatilization of liquid medium by stirring was employed to synthesize Y2O3 nanoparticle modified CoCrNi matrix (Y2O3/CoCrNi) composite powders, which were subsequently processed for L-PBF to make samples. The effects of laser power (P) and hatch spacing (h) on the microstructures and mechanical properties of the L-PBF processed (L-PBFed) Y2O3/CoCrNi composites were investigated comparatively. The results confirm that the high P (350 W) and low h (60 μm) promoted the uniform dispersion of Y2O3 particles (∼50 nm) by altering the Marangoni flow, reducing the dynamic viscosity and increasing the remelting area. The L-PBFed Y2O3/CoCrNi composites under optimized condition exhibited a superior strength-ductility synergy, in which the yield strength, ultimate tensile strength and fractured strain were 647 MPa, 858 MPa and 42.2 %, respectively. It is demonstrated that a metallurgical defect-free hierarchical microstructure that involved dislocation-formed cellular structures, dispersion of Y2O3 particles and various crystallize defects (i.e. stacking faults, Lomer-Cottrell locks, and deformation twins) were responsible for the superb mechanical properties.

Development of PVA-ABO3 organic-inorganic nanocomposite proton exchange membrane for HT-PEMFCs

In this study for the first time, poly(vinyl alcohol) (PVA)-ABO3 (BaCeO3/SrCeO3/SrZrO3) nanocomposite membranes were prepared as proton exchange membrane for high-temperature proton exchange membranes fuel cell (HT-PEMFC). Proton ion-conducting material based on perovskite ceramic ABO3 were prepared by sol-gel combustion method. PVA-ceramic nanocomposite membrane containing BaCeO3, SrCeO3, SrZrO3, nanoparticles in various compositions were developed by solutions casting method. Structural features are confirmed by X-ray diffraction (XRD) and FTIR. Uniform dispersion of ceramic particles in polymer membrane is confirmed by scanning electron microscopy. Proton-conducting ability of the composite membranes was revealed by impedance spectroscopy. The ion-conducting ability of the membrane was studied under three conditions (1) by hydrating the membrane, (2) by phosphoric acid doping, and (3) by sulphuric acid doping. Proton conductivity of phosphoric acid doped nanocomposite membrane is found to be highest amongst the others. The dynamics of proton ion conduction were revealed by electric modulus spectrum. The composite membrane exhibited good mechanical strength and thermal stability up to 120 °C. The PVA-BaCeO3 (PVA-BCO) composite membrane demonstrates maximum proton ion conductivity 2.84 × 10−3 S/cm as compared to PVA and other PVA-based composites at 120 °C using phosphoric acid doping. For PEMFC applications, phosphoric acid-doped composite membranes made of PVA and barium cerate (BaCeO3) have a high potential of effectiveness.

Understanding Polymer Structure and Conductivity in Composite Electrolytes

Lithium ion batteries are a crucial technologies for electric vehicles and portable electronics due to their high energy density. However, flammable liquid electrolytes create a safety concern and transitioning to all solid state batteries allows for the potential of higher energy density by utilizing lithium metal anodes. Two classes of solid materials have been explored to replace liquid electrolytes: ceramic and polymer electrolytes. Composite electrolytes, typically in the form of dispersed ceramic particles or nanowires in polymer matrix, combine these two materials to have good ionic conductivity while maintaining the mechanical properties of the polymer. While they have achieved fairly high conductivity (typically 10-4 S/cm), the mechanism for such ion conduction is not well understood.The polymer likely plays a crucial role as the ceramic volume fractions are typically under 20%.1,2 Four possible ways that polymers could increase in conductivity in the composite have been identified: decreased crystallinity, increased free volume, disruption of polymer alignment, and increased lithium ion dissolution due to acidic surface groups on the ceramic.1,3,4 We have developed thin film model systems to probe the interface of the polymer with and ceramic surfaces. We found that when confined to thin films, the conductivity of the polymer electrolyte increased compared to the bulk. We utilized differential scanning calorimetry to identify the crystallinity and found that the small crystallinity variation could not account for the variation in conductivity. Subsequently, we utilized surface conductivity and transference number measurements to understand the effects of acidic surface groups. X-ray Absorption measurements will be similarly utilized to probe the variation in lithium ion environments within these materials to understand any variation in the lithium salt dissolution. It was found that the variation in conductivity based on this effect is small.In order to probe the possible variation in free volume, Small Angle Neutron Scattering will be utilized to quantify the free volume within thin films, bulk polymer, and composite electrolytes. This can quantify the volume associated with each monomer and therefore how much space is between polymer chains for lithium ion movement.5 Lastly, while the polymer chain alignment has not been extensively discussed composite literature, it has been identified that when polymer electrolytes are cast on a surface, polymer electrolytes typically show anisotropy with measurements parallel to the surface having higher conductivity due to the alignment of the chain.6 Therefore, ceramic fillers in the composites may disrupt this packing and allow for higher conductivity perpendicular to the cast surface, the direction in which they are most commonly measured. In order to probe this effect, we measure the anisotropy of both our thin film electrolytes as well as composite electrolytes to compare the significance of the anisotropy and utilize small angle x-ray scattering to measure any anisotropy in the structure.

Fabrication and evaluation of PLA/MgAl2O4 scaffolds manufactured through 3D printing method

In this study, we synthesized magnesium aluminate spinel (MgAl2O4) with a particle size ranging from 35 to 70 nm using a facile combustion approach. Then, we used a 3D printing (FDM) machine to produce PLA/x wt% MgAl2O4 (x = 0, 2, 4, 6, and 8) scaffolds. To investigate the crystal structure, microstructure, biodegradability, and thermal characteristics of the produced materials, we employed X-ray diffraction analysis (XRD), field emission scanning electron microscope (FESEM), Inductively Coupled Plasma (ICP), Simultaneous Thermal Analysis (STA), and compressive strength analyses. The results showed that PLA/6 wt% MgAl2O4 scaffolds possess the highest amounts of compressive strength. We evaluated the bio-activation and biodegradability of scaffolds by immersing them in simulated body fluid (SBF) for four weeks. Interestingly, the highest strength was achieved in PLA/6 wt% MgAl2O4 scaffolds, while the improper dispersion of ceramic particles happened on the polymer substrate in cases where x>6. ICP analysis showed that the addition of spinel nanoparticles to PLA increased the biodegradability of the scaffolds. Our FESEM results supported this finding and also revealed that the dispersion of ceramic particles on the polymer substrate was not uniform in cases where x>6. Also, according to the results of STA, the presence of MgAl2O4 nanoparticles effectively reduces the rate of thermal decomposition from 95 to 85 percent.

Limiting Factors Affecting the Ionic Conductivities of LATP/Polymer Hybrid Electrolytes

All-Solid-State Lithium Batteries (ASSLB) are promising candidates for next generation lithium battery systems due to their increased safety, stability, and energy density. Ceramic and solid composite electrolytes (SCE), which consist of dispersed ceramic particles within a polymeric host, are among the preferred technologies for use as electrolytes in ASSLB systems. Synergetic effects between ceramic and polymer electrolyte components are usually reported in SCE. Herein, we report a case study on the lithium conductivity of ceramic and SCE comprised of Li1.4Al0.4Ti1.6(PO4)3 (LATP), a NASICON-type ceramic. An evaluation of the impact of the processing and sintering of the ceramic on the conductive properties of the electrolyte is addressed. The study is then extended to Poly(Ethylene) Oxide (PEO)-LATP SCE. The presence of the ceramic particles conferred limited benefits to the SCE. These findings somewhat contradict commonly held assumptions on the role of ceramic additives in SCE.

Enhancing Li+ transport efficiency in solid-state Li-ion batteries with a ceramic-array-based composite electrolyte

An innovative composite solid electrolyte (CSE) enhances Li+ transport efficiency by integrating an array of ceramic pillars into a polymer matrix, as compared to conventional CSEs with dispersed ceramic particles.

A Three-Dimensionally Interconnected Composite Polymer Electrolyte for Solid-State Batteries

High energy density of solid-state batteries requires a thin solid electrolyte separator layer (<30 μm), that can sustain high currents and is easily processable. Polymer-ceramic composite electrolytes can potentially fulfill these requirements by combining the advantages of each type. Ceramic electrolytes have high room-temperature ionic conductivity, transference number of one, and mechanical strength to suppress lithium dendrites, whereas polymer electrolytes are easily processable and can form conformable interfaces with the electrodes. High interfacial-impedance between polymer and ceramic electrolytes make the composites with dispersed ceramic particles less attractive.1 A composite electrolyte architecture where a three-dimensionally interconnected porous ceramic is filled with polymer electrolyte, previously reported by our group, can avoid the interfacial impedance issue, although for thin composite membranes, the interfacial impedance between ceramic framework and excess polymer layer on top/bottom surface will still dominate the overall impedance.2 Here we will present fabrication and electrochemical evaluation of ~150 μm thick composite electrolytes with the above-described 3D-interconnected ceramic architecture. The 3-D framework is obtained by partially sintering Ohara ceramic particle tapes obtained via tape casting, which are filled with curable polymer electrolyte precursors. To obtain a thin (5 μm), uniform polymer electrolyte layer on both surfaces, spray coating was employed. The resulting composite membrane exhibited good dendritic resistance in symmetric cell cycling, improved transference number compared to the polymer electrolytes. We also found significantly improved flexibility of the composite electrolytes with plasticization, however, at the cost of reduction in ionic conductivity due to damage to the ceramic network caused by plasticizer-induced swelling of the cross-linked polymer electrolyte. This research was sponsored by the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy for the Vehicle Technologies Office’s Advanced Battery Materials Research Program (Tien Duong, Program Manager). This abstract has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan). References Chen, X. C.; Liu, X.; Samuthira Pandian, A.; Lou, K.; Delnick, F. M.; Dudney, N. J., Determining and Minimizing Resistance for Ion Transport at the Polymer/Ceramic Electrolyte Interface. ACS Energy Letters 2019, 4 (5), 1080-1085.Palmer, M. J.; Kalnaus, S.; Dixit, M. B.; Westover, A. S.; Hatzell, K. B.; Dudney, N. J.; Chen, X. C., A three-dimensional interconnected polymer/ceramic composite as a thin film solid electrolyte. Energy Storage Materials 2020, 26, 242-249.

Fabrication, morphological, mechanical and biological performance of 3D printed poly(ϵ-caprolactone)/bioglass composite scaffolds for bone tissue engineering applications

Several techniques, such as additive manufacturing, have been used for the manufacture of polymer-ceramic composite scaffolds for bone tissue engineering. A new extruder head recently developed for improving the manufacturing process is an experimental 3D printer Fab@CTI that enables the use of ceramic powders in the processing of composite materials or polymer blends. Still, the manufacturing process needs improvement to promote the dispersion of ceramic particles in the polymer matrix. This article addresses the manufacture of scaffolds by 3D printing from mixtures of poly(ϵ-caprolactone) (PCL) and a glass powder of same composition of 45S5Bioglass®, labeled as synthesized bioglass (SBG), according to two different methods that investigated the efficiency of the new extruder head. The first one is a single extrusion process in a Fab@CTI 3D printer, and the other consists in the pre-processing of the PCL-SBG mixture in a mono-screw extruder with a Maddock® element, followed by direct extrusion in the experimental Fab@CTI 3D printer. The morphological characterization of the extruded samples by scanning electron microscope showed an architecture of 0°/90° interconnected struts and suitable porosity for bone tissue engineering applications. Scaffolds fabricated by two methods shows compressive modulus ranging from 54.4 ± 14.2 to 155.9 ± 20.4 MPa, results that are compatible to use in bone tissue engineering. Cytotoxicity assays showed non-toxic effects and viability for in vitro MG-63 cell proliferation. Alizarin Red staining test showed calcium deposition in all scaffolds, which suggests PCL/SBG composites promising candidates for use in bone tissue engineering. Results of cell morphology suggest more cell growth and adhesion for scaffolds fabricated using the pre-processing in a mono-screw extruder.

Piezoelectric Ceramic/Photopolymer Composites Curable with UV Light: Viscosity, Curing Depth, and Dielectric Properties

Four piezoelectric ceramic materials with varying particle sizes and geometries are added up to 30 vol.% to a photopolymer resin to form UV-curable piezoelectric composites. Such composites solidify in a few minutes, can be used in UV-curing-based 3D printing processes, and can achieve improved sensor performance. The particle dispersion with ultrasonication shows the most homogeneous particle dispersion with ethanol, while two other solvents produced similar results. The viscosities of the prepared suspensions show some dependency on the particle size. The curing depth results show a strong dependency on the ceramic particle size, the difference in refractive index, and the particle size distribution, whereby composites filled with PZT produced the worst results and composites filled with KNN produced the highest curing depths. The SEM images show a homogeneous dispersion of ceramic particles. The highest dielectric properties are also shown by KNN-filled composites, while BTO and PZT produced mixed results of dielectric constants and dielectric losses. KNN-filled composites seem to be very promising for further 3D-printable, lead-free piezoelectric composite development.

Bioactivity assessment of additively manufactured doped-HA composite scaffolds for bone tissue engineering

Composites are promising candidates for treating bone defects, but manufacturing of composite scaffolds is challenging. This study aimed to fabricate composite scaffolds based on polycaprolactone (PCL) and doped Hydroxyapatite (HA) via a single step melt extrusion additive manufacturing technique. Starting from the raw powder forms, the printed scaffolds were produced and then characterized for morphology, mechanical behavior and in vitro mineralization. MicroCT revealed the homogenous dispersion of ceramic particles in the PCL matrix. Also, SEM showed the ceramic particles on the surfaces of printed scaffolds. Furthermore, bioactivity assays confirmed the enhanced apatite deposit formation on composite scaffolds compared to PCL alone.

Microstructure and mechanical properties of Cu/RHA composites fabricated by friction stir processing

Pure copper its composites reinforced with Rice Husk Ash (RHA) particles prepared by Friction Stir Processing (FSP) technique. Copper Matrix Surface Composites (CMSCs) is to enrich the metallurgical and mechanical properties. Pure copper used as matrix material and ceramics particles RHA used as reinforcement. CMSCs were fabricated a set of process parameters such as rotational speed 1000 rpm, transverse speed 40 mm/min and an axial force 10 kN with a single pass. CMSCs are presently characterized using Optical Microscope (OM), Field Emission Scanning Electron Microscopy (FESEM), Vickers hardness tester, and wear behavior conduct by pin-on-disk apparatus. High abrasive wear loss of pure copper because of its softness material. CMSCs of micrograph revealed the enhanced fine bonding in the stir zone (SZ) with a uniform dispersion of ceramic particles. The addition (0, 6, 12, 18 vol%) of RHA particles to copper prompts an expressive improvement in its hardness and wear resistance.

Effect of amount of TiB2 and B4C particles on tribological behavior of Al7075/B4C/TiB2 mono and hybrid surface composites produced by friction stir processing

In this study, by friction stir processing, we fabricated several defect-free Al7075/B4C/TiB2 mono and hybrid surface composites containing various amounts of B4C and TiB2 reinforcements with high quality interfacial bonding with substrate, fine recrystallized matrix grains, and homogenous dispersion of ceramic particles through the matrix. The composite region of hybrid composite samples was more constricted compared with that of mono composite samples. All hybrid composites had more hardness and wear resistance in comparison to Al/B4C mono composite sample. Among different hybrid composites, the most optimal dispersion of ceramic particles, minimum size of B4C and TiB2 ceramic particles, the lowest friction coefficient, and the highest hardness and wear resistance belonged to the hybrid composite containing equal weight percentage of B4C and TiB2 ceramic particles (named 50%B4C-50%TiB2 hybrid composite). The hardness and wear resistance of the Al7075/B4C, Al7075/TiB2 mono composites and the 50%B4C-50%TiB2 hybrid composite were respectively enhanced by (91%, 121%, 107%) and (67%, 82%, 87%) regarding Al7075 base alloy. During wear, an unstable-simple tribolayer was formed on the surfaces of Al7075 base alloy and unreinforced FSPed samples; however, a more stable mechanically mixed tribolayer containing a mixture of oxygen, ceramic particles, and alloying elements of Al7075 base alloy and steel counterface was formed on the surface of the composite samples. The most stable tribolayer with the highest self-lubricating behavior belonged to the 50%B4C-50%TiB2 hybrid composite owing to the high amount of iron and very low amount of B4C in the tribolayer, resisting the subsurface of tribolayer to crack propagation.

Localized dispersing of TiB2 and TiN particles via pulsed laser radiation for improving the tribological performance of hot stamping tools

The aim of this study is to increase the tribological performance of hot stamping tools by using a laser implantation process. This technique allows the fabrication of separated, elevated and dome-shaped microfeatures on the tool surface in consequence of a localized dispersing of ceramic particles via pulsed laser radiation. Hence, the topography and material properties of the tool are modified, which influences the tribological interactions at the blank-die interface. However, an appropriate selection of ceramic particles is an essential prerequisite, in order to obtain tailored and highly wear resistant surface features. In this regard, different titanium-based hard particles (TiB2 and TiN) were laser-implanted on hot working tool specimens and subsequently tested by means of a modified pin-on-disk test regarding to their wear and friction behavior.

A New Approach to 3D Printing Dense Ceramics by Ceramic Precursor Binders

Fabrication of dense ceramic objects by 3D printing processes is important in achieving improved functions in many applications, such as mechanical, optical, and electrical devices. It is a challenging process, mainly due to the high content of organic binders within the printed object. Upon heating and sintering, the printed object shrinks and becomes porous due to the decomposition of the organic binder. Herein, a new approach is presented based on the utilization of an inorganic binder that is a sol–gel precursor for the same material composing the dispersed ceramic particles. The approach is demonstrated in printing objects composed of barium titanate (BTO), which is an important dielectric and piezoelectric material. This binder also enables us to achieve dispersions with high solid load that exhibits a shear‐thinning rheological behavior, which is essential for direct ink writing (DIW) printing technology. The as‐printed parts contain only 1 wt% organic materials, having 97.8% of the theoretical density, whereas the BTO binder crystalizes upon heating, without forming undesired secondary phases.

Investigating the effects of hybrid reinforcement particles on the microstructural, mechanical and tribological properties of friction stir processed copper surface composites

Friction Stir Processing (FSP) technique was employed in this research to fabricate copper surface composites through incorporating a hybrid mixture of reinforcement particles. Hybrid combination of advanced nitride based ceramic particles (25% AlN + 75% BN) was dispersed onto the surface of copper matrix at varying volume fractions through FSP technique. Results demonstrated an increase in mechanical properties with respect to increase in the amount of particle dispersion. Mechanism of fracture for developed set of surface composites was studied with the aid of fractography. A tremendous increase in wear resistance was observed with respect to increase in hybrid particle dispersion owing to the hardness and self-lubricating characteristics of dispersed ceramic particles.

A quasi-solid composite separator with high ductility for safe and high-performance lithium-ion batteries

The safety of lithium ion batteries is correlated closely to the mechanical property and thermal stability of separators. The polymer/ceramic particle composite separators are widely investigated for quasi-solid gel separators of lithium ion batteries, but the nonuniform dispersion of ceramic particles limits their performance. In this study, ball-milled Al-doped Li6.75La3Zr1.75Ta0.25O12 suspension is incorporated into poly (vinylidene fluoride-co-hexafluoropropylene) gel to prepare a highly uniform quasi-solid composite separator. The results show that adding only 4.29 wt% Li6.75La3Zr1.75Ta0.25O12 into PVDF-HFP increases ductility by three times and the mechanical strength by 38% as compared with pure PVDF-HFP separator. Batteries with the composite separator show significantly improved cyclic stability and rate performance at both room temperature and temperatures up to 80 °C. In particular, the composite separator promotes homogenous Li+ flux through the separator and suppresses Li dendrite growth in Li-metal based batteries.

Triple-Bioinspired Burying/Crosslinking Interfacial Coassembly Strategy for Layer-by-Layer Construction of Robust Functional Bioceramic Self-Coatings for Osteointegration Applications.

Coating bioceramics of inherent bioactivity onto biometallic implants is a straightforward yet promising solution to address poor osteointegration of the latter. One step further, it would be a nontrivial accomplishment to develop a mild, cheap, and universal route to firmly stabilizing, in principle, any ceramics onto any implant substrate, while imparting expectedly versatile biofunctional performances. Herein, we describe a triple-bioinspired burying/cross-linking interfacial coassembly strategy for enabling such ceramic coatings, which ingeniously fuses bioinspiration from sea rocks (burying assisted particle immobilization), marine mussels (universal adhesion and versatile chemical reactivity), and reef-building oysters (cross-linking rendered cohesion). Specifically, surface functionalized, aqueous dispersed ceramic particles were buried within an substrate-anchored organic matrix of polyelectrolyte multilayers (i.e., (poly(ether imide) (PEI)/poly(sodium-p-styrenesulfonate) (PSS)) n), through a new inorganic-organic hybrid layer-by-layer (LBL) coassembly scheme wherein mussel (oyster) inspired adhesive (cohesive) chemistries were exquisitely orchestrated. As a conceptual demonstration, bioactive baghdadite (Ca3ZrSi2O9) was synthesized as model ceramics, with which we constructed on medical titanium robust, biomimetic, and cross-linkable LBL self-assemblies harnessing the said strategy. Intimate substrate contacts and well-defined buried inorganic-organic interfaces were evidently seen, together with good structural and chemical stabilities, especially after cross-linking. Sustained bioactive ion releasing and appreciable biomineralization activity were confirmed in vitro. Subsequently, biological performances of the assemblies were systematically investigated with respect to surface hydrophilicity, protein adsorption, and osteoblast functions. Additionally, nanosilver deposition, which imparted the surfaces with added antibacterial potencies, was used to exemplify the strategy's versatility in allowing multifunctionality. What's more, the flexibility of our approach was testified through modifying clinically relevant complicated 3D porous scaffolds. Overall, our strategy basically met the design expectations, boding well for future medical adoption. This study offers the promise of an alternative broadly useful avenue to bioactive and functional surface design of bone implants. It may also provide insights into other multiple-bioinspired materials/interfaces for biological and other applications.

Surface modification and dispersion of ceramic particles using liquid-liquid extraction method for application in supercapacitor electrodes

Particle extraction through liquid-liquid interface (PELLI) was used for the extraction of MnO2, Mn3O4, FeOOH and ZnO particles from an aqueous synthesis medium to the n-butanol phase. The benefits of PELLI were demonstrated by the fabrication of supercapacitor electrodes, which showed good electrochemical performance at high active mass loadings. Octyl gallate (OG) was found to be an efficient and versatile extractor for the ceramic particles. The phase transfer of the particles resulted in reduced agglomeration, which allowed for improved electrolyte access to the particle surface and facilitated their mixing with conductive multiwalled carbon nanotube (MWCNT) additives. It was shown that OG is a promising extractor material for the fabrication of ceramic-ceramic, ceramic-metal and ceramic-MWCNT nanocomposites. The strong adsorption of OG on the particle surface involved bridging or chelating bidentate bonding of the catechol group to the metal atoms. The capacitive properties of FeOOH-MWCNT electrodes were tested in the negative potential window. MnO2-MWCNT and Mn3O4-MWCNT electrodes were investigated for charge storage in the positive potential window. The highest capacitance of 5.7 F cm−2 for positive electrodes was achieved using MnO2-MWCNT composites with active mass loading of 36 mg cm−2. The Mn3O4-MWCNT electrodes exhibited improved capacitance retention at high charge-discharge rates.

Dispersion behavior of TiB2 particles in AISI D2 tool steel surfaces during pulsed laser dispersing and their influence on material properties

AISI D2 is one of the most applied cold-working tool steel for deep drawing operations, due to the materials good toughness and high wear resistance. However, since the lubricant-free deep drawing as well as the processing of high strength and ultra-high strength steel sheets remaining ongoing trends in the automotive industry, the tool surfaces need to be improved regarding their friction and wear behavior. For this purpose elevated micro textures can be applied. Since protruded micro features are predominantly affected by wear, a structuring process enabling the formation of suitable textures with high wear resistance is needed.In this paper surface texturing at microscale was conducted by laser implantation. This technique allows the fabrication of highly wear resistant, separated and elevated features (implants) on steel surfaces via a discontinuous dispersing of ceramic particles by pulsed laser radiation. The aim of this study was to investigate the techniques potential for the creation of wear resistant elevated micro features on AISI D2 tool steel surfaces by the application of TiB2 particles. The laser parameters (pulse power and length) were varied and a comparative material analysis on AISI D2 laser remelted spots and TiB2 localized dispersed zones was examined. High-speed camera recordings allowed the description of the particle insertion mechanism from pre-coatings during laser processing. Mechanical properties were analyzed by (micro-) hardness measurements at top and cross sections. The microstructure was investigated by optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The implants geometrical properties (diameter, height, depth) were investigated by white light interferometry and optical microscopy. The experiments reveal that a pulsed laser remelting of AISI D2 leads to a significant hardness drop due to high retained austenite (γR) contents. Contrary, a localized dispersing of TiB2 particles leads to defect free dome- or ring-shaped elevated features with hardness values up to 1800 HV1. The high hardness values result from the dispersed TiB2 particles and an in-situ precipitation of new hard particle phases, which lead to a reduction of the γR content within the matrix.

Metal-Ceramic composites via “in situ” methods

Several “in situ” methods for obtaining composite materials with ceramic particles were developed in order to overcome some of the inherent problems associated with conventional processes.This paper reviews the obtaining processes of composite materials with a greater emphasis on nitriding and oxidation by directed melting. These obtaining methods provide microstructures with different combinations of metal–ceramic. Metal matrix composites with controlled amounts of dispersed ceramic particles are obtained by “in situ” processes. The composite materials obtained are having different properties by controlling various processing variables such as temperature, time, the reactant phases and the reinforcing material.The properties of the “in situ” obtained materials depend mainly on the matrix and volume fraction of constituent phase. Briefly are reviewed the mechanical properties, hardness mechanisms and possible applications of these composite materials.Nitridation is much more attractive because with the variation of process parameters is obtained a wider range of microstructures and properties. The activation energy for the formation of AlN (A1N ∼ 100 kJ/mole) is smaller than that of oxidation (Al2O3 ∼ 400 kJ/mole) and growth rates (3 × 10-2 gm/cm2/s) are at least three times higher for oxidation.