Realization of Phase and Microstructure Control in Fe/Fe2SiO4-FeAl2O4 Metal-Ceramic by Alternative Microwave Susceptors

This study provides a novel method to prepare metal-ceramic composites from magnetically selected iron ore using microwave heating. By introducing three different microwave susceptors (Activated Carbon, SiC, and a mixture of Activated Carbon and SiC) during the microwave process, effective control of the ratio of metallic and ceramic phases has been achieved easily. The effects of the three susceptors on the microstructure of the metal-ceramics and the related reaction mechanisms were also investigated in detail. The results show that the metal phase (Fe) and ceramic phase (Fe2SiO4, FeAl2O4) can be maintained, but the metal phase to ceramic phase changed significantly. In particular, the microstructures appeared as well-distributed nanosheet structures with diameters of ~400 nm and thicknesses of ~20 nm when SiC was used as the microwave susceptor.

Nanomechanical, Tribological, and Scratch Properties of Electroless Ni-B-W Alloy and Ni-B-W-SiC Composite Coatings

Electroless deposition process can develop composite coatings superior in mechanical and tribological characteristics. The deposited alloy matrix with the reinforcement of a hard ceramic phase can produce a stronger composite coating, favorable for industrial applications. Fabrication process of Ni-B-W-SiC electroless composite coating on steel substrate by reinforcing silicon carbide (SiC) in ternary Ni-B-W matrix is presented in this report. Characteristics of the developed composite coating are studied in reference to electroless ternary Ni-B-W alloy coating. These ternary alloy and composite coatings are also subjected to heat treatment (450oC, 1 hr) to observe the changes. All coated samples are characterized with FESEM, XRD, ICP-AES, and HRTEM analyses to draw conclusions in comparative studies concerning morphological features, compositions, and phase structures. Cross-sectional and Raman spectroscopic examinations are performed to authenticate the presence of SiC phases in alloy matrix. To get a further insight on the nature, various nanomechanical and tribological properties of these coatings are evaluated and subsequently co-related. Coatings developed with silicon carbide particles present in matrices show remarkable improvements in nano-hardness (H), reduced modulus (Er), yield strength, and fraction of plastic work done. Heat treatment imparts propitious effects on these mechanical properties due to the formation of harder nickel boride (Ni3B, and Ni2B) phases. Heat-treated Ni-B-W-SiC composite subjected to tribological and micro-scratch testing reveals a significant improvement in sliding wear and scratch resistance as compared to those in other coatings.

Crystallization and Dielectric Properties of BaO-SrO-PbO-TiO2-Nb2O5-SiO2 Glass-Ceramic Composites with La2O3 Addition

Glass-ceramic composite samples with different La2O3 content were prepared via melt-quenching followed by controlled crystallization. X-ray diffraction(XRD) analysis reveals that when the addition amount of La2O3 in the glass sample is less than 1mol%, two phases of perovskite structure and tungsten-bronze structure are formed after annealing at 1000°C for 3h. When the addition amount of La2O3 in the glass sample is increased to 2mol%, a new phase of pyrochlore structure is formed. Moreover, the addition of La2O3 causes the change in the lattice parameters of the glass-ceramic crystal phase. The microstructure observed that the ceramic phase grain size is in the nanometer level. The shape of some grains becomes an elongated structure when the La2O3 content in the sample increases to 2 mol%, and the grain size is increased significantly. The dielectric constant of the BaO-SrO-PbO-TiO2-Nb2O5-SiO2 glass-ceramic system is decreased with the increase of La2O3 addition, and the dielectric loss of the sample is decreased to the range of 0.003-0.008. The electric field stability of the dielectric constant was significantly improved with the addition of La2O3, indicating that adding a certain proportion of La2O3 to the BaO-SrO-PbO-TiO2-Nb2O5-SiO2 glass-ceramic system can effectively improve the dielectric properties, and it has a promising application as a dielectric material.

Features of the Synthesis of the Dispersed TiC Phase with Nickel Nanostructures on the Surface to Create an Aluminum-Based Metal Composite

The development of new composites with improved functional properties is the important task of modern materials science. The composites must be structurally organized to provide improved properties. For metal-ceramic composites, there is a need for a uniform distribution of the dispersed ceramic phase in the bulk metallic matrix The modification of the dispersed ceramic phase surface with a metal coating is one of the more effective ways to accomplish this. Particularly, in this work, the conditions of Ni nanolayer deposition on titanium carbide (TiC) particles were studied. The goal was to create core–shell particles with a thickness of the Ni coating on TiC not exceeding 90 nm. Preliminary work was also carried out to study the effect of the dispersed phase composition on the mechanical properties of the composite with an Al matrix.

PROCESSING OF ULTRA-HIGH TEMPERATURE CERAMIC MATRIX COMPOSITES (UHTCMCS) THROUGH RF ENHANCED CHEMICAL VAPOUR INFILTRATION (RF-CVI)

Carbon fibre (Cf) reinforced Ultra High Temperature Ceramic (UHTC) Matrix Composites (UHTCMCs) have proven to be excellent materials that can survive nearly 3000°C in highly oxidizing environments along with a good specific strength. Consequently, they have excellent potential for use in aerospace applications such as rocket nozzle throats and thermal protection systems (TPS). Due to the presence of the carbon fibres, UHTCMCs offer high strength and modulus combined with excellent thermal shock behaviour whilst the presence of the ultra-high temperature ceramic phase protects the carbon fibres at the application temperatures. High temperature oxidation, thermal ablation behaviour and mechanical properties of the UHTCMC’s relies heavily on the bonding between the carbon fibre and matrices especially the oxides formed to avoid any progressive failure and predict the life of the components. In the present investigation, a radio frequency assisted chemical vapor infiltration (RF-CVI) technique has been used to make the 2.5D Cf reinforced ZrB2, ZrB2/carbon matrices composites with various interphase materials. The advantage of RF heating is that it creates an inverse temperature profile in the sample, which means that the infiltration starts from inside and progresses outwards. This allows the time needed for processing to be reduced very significantly compared to the conventional CVI process. This presentation will report on the latest results from the research that has been undertaken at the University of Birmingham, including the results from a wide range of testing that has been undertaken at both DLR in Germany and the University of Naples in Italy.

Production of TiC-MMCs Reinforcements in Cast Ferrous Alloys Using In Situ Methods

This literature review aims to summarize the research conducted on the production of locally reinforced ferrous castings based on metal matrix composites reinforced with TiC (TiC-MMCs). One way to improve the wear resistance of cast components is to reinforce critical regions locally with metal matrix composites (MMCs) without changing the toughness of the component core. The in situ method of self-propagating high-temperature synthesis is one of the main approaches for the production of this enhanced material. Using this approach, the reinforcement is formed from a powder compact inserted in the mold cavity. The temperature of the liquid metal then produces the combustion reactions of the powders, which promote the formation of the ceramic phase. This paper focuses on eight powder systems used to synthesize TiC: Ti-C, Ni-Ti-C, Ni-Ti-B4C, Fe-Ti-C/Fe-Cr-Ti-C, Cu-Ti-B4C, Al-Ti-C, and Al-Ti-B4C, and provides an overview of the methodologies used as well as the effect of processing variables on the microstructural and mechanical characteristics of the reinforcement zones.

RESEARCH ON TRIBOLOGICAL BEHAVIOR OF Cr3C2-25NiCr-COATED BRAKE DISC

This research presents the results of a comparative study to determine the friction and wear behavior of the high-velocity oxygen fuel (HVOF)-sprayed Cr3C2-25NiCr-coated brake disc. The friction and wear behavior of Cr3C2-25NiCr-coated brake disc (CD) and the sliding against the commercial brake pad were examined on a laboratory-scale disc-pad dynamometer and the findings were compared with those of reference brake disc (UCD). The coating was deposited by means of the HVOF process on a grey cast iron (GCI) substrate. Braking tests were performed according to the SAE-J2430 test standard. The as-sprayed coating was characterized for their microstructure and phase constitution by SEM/EDS and XRD. The results reveal that the coefficient of friction (COF) of CD and UCD varies between 0.42–0.57 and 0.44–0.62, respectively. The Cr3C2-25NiCr-coated brake disc was found to have exhibited a comparable COF and lower wear loss to the reference brake disc. The addition of a ceramic phase to the brake disc coating played an important role in reducing the COF to an acceptable range and improving the sliding wear resistance of the brake pair.

Hydroxyapatite Obtained via the Wet Precipitation Method and PVP/PVA Matrix as Components of Polymer-Ceramic Composites for Biomedical Applications

The aspect of drug delivery is significant in many biomedical subareas including tissue engineering. Many studies are being performed to develop composites with application potential for bone tissue regeneration which at the same provide adequate conditions for osteointegration and deliver the active substance conducive to the healing process. Hydroxyapatite shows a great potential in this field due to its osteoinductive and osteoconductive properties. In the paper, hydroxyapatite synthesis via the wet precipitation method and its further use as a ceramic phase of polymer–ceramic composites based on PVP/PVA have been presented. Firstly, the sedimentation rate of hydroxyapatite in PVP solutions has been determined, which allowed us to select a 15% PVP solution (sedimentation rate was 0.0292 mm/min) as adequate for preparation of homogenous reaction mixture treated subsequently with UV radiation. Both FT-IR spectroscopy and EDS analysis allowed us to confirm the presence of both polymer and ceramic phase in composites. Materials containing hydroxyapatite showed corrugated and well-developed surface. Composites exhibited swelling properties (hydroxyapatite reduced this property by 25%) in simulated physiological fluids, which make them useful in drug delivery (swelling proceeds parallel to the drug release). The short synthesis time, possibility of preparation of composites with desired shapes and sizes and determined physicochemical properties make the composites very promising for biomedical purposes.

The Early Iron Age IIA Ceramic Assemblage from Khirbet al-Ra‘i

The early 10th-century BCE pottery assemblage from Khirbet al-Ra‘I is presented. The assemblage, which came from a few rooms that were suddenly destroyed, offers a large number of complete profiles. This is the second largest pottery assemblage, after that of Khirbet Qeiyafa, of this poorly known ceramic phase.