High Quality, Fully Dense Ceramic Components Manufactured Using Fused Deposition of Ceramics (FDC)

Solid Freeform Fabrication (SFF) is a technology that produces physical solid components or parts from computer design models. This technology has the potential of reducing functional ceramic product development cycle time in terms of reducing design iteration and production time, minimizing extra post processing, and therefore reducing cost. A commercially available Fused Deposition Modeling (FDM™) 3D Modeler was altered for use with ceramics. This newly developed method referred to as Fused Deposition of Ceramics (FDC) is capable of fabricating complex shape, functional ceramic components. We have investigated issues related to hardware, software, feed material, and build strategy which are required to achieve high quality, fully dense green ceramic parts. In this paper, we report recent improvements made in the FDC process, including hardware modifications, software improvements, feed material standardization, as well as build strategy/condition control. We also report the current FDC status for making complex functional parts. Our goal is to optimize the FDC condition to ensure its robustness for producing defect free green ceramic parts consistently and without interruption.Mechanical Engineerin

Fabrication and properties of Al-infiltrated RBAO-based composites

The reaction-bonded Al2O3 (RBAO) process is applied to fabricate open porosity Al2O3-based composites with SiC and Al2O3 particulate inclusions. These are then gas-pressure infiltrated with liquid aluminum. The Al-infiltrated composites exhibit strongly improved mechanical properties, e.g. fracture toughness and bond strength of samples containing 30 vol.% 13 µm diameter Al2O3 platelets are enhanced 1·6 to 5·8 MPavm and from 85 to 760 MPa, respectively. In all cases, crack bridging by ductile Al ligaments is the main toughening mechanism. Filling of void defects, caused by particulate agglomeration, with Al is especially effective in reducing the strength-controlling flaw size

A Low Cost Fe3O4–Activated Biochar Electrode Sensor by Resource Utilization of Excess Sludge for Detecting Tetrabromobisphenol A

Owing to its ubiquity in natural water systems and the high toxicity of its accumulation in the human body, it is essential to develop simple and low-cost electrochemical sensors for the determination of 3,3′,5,5′-tetrabromobisphenol A (TBBPA). In this work, Fe3O4–activated biochar, which is based on excess sludge, was prepared and characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and BET analysis to analyze its basic features. Subsequently, it was used to fabricate an electrochemical sensor for the detection of TBBPA. The electrochemical test results revealed that the Fe3O4–activated biochar film exhibited a larger active surface area, a lower charge transfer resistance and a higher accumulation efficiency toward TBBPA. Consequently, the peak current of TBBPA was significantly enhanced on the surface of the Fe3O4–activated biochar. The TBBPA sensing platform developed using the Fe3O4–activated biochar composite film, with relatively a lower detection limit (3.2 nM) and a wider linear range (5–1000 nM), was successfully utilized to determine TBBPA levels in water samples. In summary, the effective application of Fe3O4–activated biochar provided eco-friendly and sustainable materials for the development of a desirable high-sensitivity sensor for TBBPA detection

Tetracycline Adsorption on Magnetic Sludge Biochar: Effects of pH, Humic Acid (HA), and Fulvic Acid (FA)

Natural organic matters (NOMs) are ubiquitous in the environment, but few systematic studies have examined the influence of NOMs on the sorption ability of magnetic sludge biochar. In this study, magnetic sludge biochar was synthesized, characterized, and used as a sorbent to remove tetracycline (TC) from aqueous solutions. The effects of pH, humic acid (HA), and fulvic acid (FA) on TC adsorption by magnetic sludge biochar were studied using batch experiments. Adding HA and FA can alter the adsorption behavior of TC, except for its pH dependency. The results of this study show that relatively low concentrations of dissolved HA (≤8 ppm) and FA (≤5 ppm) promote the adsorption capacity of TC, but higher concentrations compete against TC for sorption sites on the surface of magnetic sludge biochar. The results of this study promote a better understanding of the application of magnetic sludge biochar in real antibiotic wastewater

Properties of RU955 Si3N4 Filament for Fused Deposition ofCeramics

One ofthe key elements in the FDC process is the development of ceramic loaded fusible filament. The filament is not only material feed stock for deposition, but also serves as a piston to push the fused material through the FDC liquefier. Therefore, the FDC filament has to meet several requirements. It should have enough flexibility to satisfy the automatic feeding requirements, enough stiffness to carry the force for extrusion in the liquefier, and a low viscosity. A series of binders developed at Rutgers University show promising properties and meet these requirements. However, the change of filament properties with time and storage conditions was observed, and they dramatically influenced the FDC process. Systematic experiments were carried out in order to understand filament aging and establish proper storage conditions. The results indicate that moisture in the environment plays an important role in the filament aging. Vacuum treatment at 30°C apparently accelerates the aging process. The mechanisms offilament aging and the method offilament evaluation will be discussed.Mechanical Engineerin

The Role of Materials Processing Variables in the FDC Process

The Fused Deposition of Ceramics (FDC) is based on the commercially available Fused Deposition Modeling (IDMTM) technique developed by Stratasys Inc. The FDC process is being currently developed to make complex ceramic parts in an automated fashion. Although the current focus is on making SisN4 parts, this technique has been successfully used to make electroceramic (such as PZT) and metallic (such as stainless steel) parts. As feedstock for the IDC process, filaments loaded with 55 vol% GS-44 Si3N4 is being used. For the filament to be used in the IDC process, it must possess a unique combination of physical, rheological and mechanical properties. In this paper, we investigate the role played by some of the process variables on these properties. Our current processing sequence to make filaments is as follows - coating of powders with a surfactant, compounding the ceramic and binder, extrusion into filaments and finally treatment of filaments to achieve requisite properties. The study has resulted in improvements to the quality of the filament which can be used for automated FDC. The effect of moisture, agglomerates and filament aging on FDC will be discussed.Mechanical Engineerin

Functionally Gradient Materials for Thermal Barrier Coatings in Advanced Gas Turbine Systems

New designs for advanced gas turbine engines for power production are required to have higher operating temperatures in order to increase efficiency. However, elevated temperatures will increase the magnitude and severity of environmental degradation of critical turbine components (e.g. combustor parts, turbine blades, etc.). To offset this problem, the usage of thermal barrier coatings (TBCs) has become popular by allowing an increase in maximum inlet temperatures for an operating engine. Although thermal barrier technology is over thirty years old, the principle failure mechanism is the spallation of the ceramic coating at or near the ceramic/bond coat interface. Therefore, it is desirable to develop a coating that combines the thermal barrier qualities of the ceramic layer and the corrosion protection by the metallic bond coat without the detrimental effects associated with the localization of the ceramic/metal interface to a single plane