Robert C. Voigt

Comparison of Hydroxyl Radical Generation for Various Advanced Oxidation Combinations as Applied to Foundries

The authors monitored hydrogen peroxide (H2O2), ozone (O3), and apparent hydroxyl radical (OH·) concentrations in the liquid phase, along with gas phase ozone when operating an advanced oxidation (AO) system that included H2O2, O3, sonication, and underwater plasma (UWAP). The OH· radical converted non-fluorescent terephthalic acid to fluorescent hydroxyterephthalic acid (HTA). As determined from HTA formation, when a 500 ppm H2O2 dose in tap water was combined with O3 and sonication, nearly twice as much OH· (0.72 ppm) accumulated than with H2O2 alone. When UWAP accompanied H2O2, O3, and sonication, these together generated 15–35% more OH· than when UWAP was excluded. When ozone was introduced into this AO system, the AO system decomposed almost all the O3. This research has been conducted as a part of a study that has appraised this advanced oxidation system (Sonoperoxone) in green sand foundries, where it has diminished volatile organic compound (VOC) and hazardous air pollutant (HAP) emissions by 20–75%; and clay and coal consumption by 20–35%.

Developing an engineered antimicrobial/prophylactic system using electrically activated bactericidal metals

The increased use of Residual Hardware Devices (RHDs) in medicine combined with antimicrobial resistant-bacteria make it critical to reduce the number of RHD associated osteomyelitic infections. This paper proposes a surface treatment based on ionic emission to create an antibiotic environment that can significantly reduce RHD associated infections. The Kirby-Bauer agar gel diffusion technique was adopted to examine the antimicrobial efficacy of eight metals and their ionic forms against seven microbes commonly associated with osteomyelitis. Silver ions (Ag+) showed the most significant bactericidal efficacy. A second set of experiments, designed to identify the best configuration and operational parameters for Ag+ based RHDs addressed current and ionic concentrations by identifying and optimizing parameters including amperage, cathode and anode length, separation between anode and cathode, and surface charge density. The system demonstrated an unparalleled efficacy. The concept was then implemented during in vitro testing of an antimicrobial hip implant, RHD.

Micro-scale fabrication and characterization of a silver-polymer-based electrically activated antibacterial surface.

This paper reports the fabrication methodology and characterization results for an electrically activated silver-polymer-based antibacterial surface with primary applications in preventing indirect contact transmission of infections. The surface consists of a micro-scale grating pattern of alternate silver electrodes and SU-8 partitions with a minimum feature size of 20 µm, and activated by an external voltage. In this study, prototype coupons (15 mm × 15 mm) of the antibacterial surface were fabricated on silicon substrates using two sets of lithographies, and analyzed for their physical characteristics using microscopy and surface profilometry. The prototypes were also electrically analyzed to determine their current-voltage characteristics, and hence silver ion (Ag(+)) release concentrations. Finally, they were tested for their antibacterial efficacy against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) using a newly engineered microbiological testing procedure. The antibacterial efficacy testing results show significant reductions in the number of viable organisms of both the species after 45 min of testing with 15 µA system current. Due to the growing incidences of hospital-acquired infections and rising treatment costs, study and application of such alternative antibacterial systems in critical touch-contact and work surfaces (e.g., door push plates, countertops, medical instrument trays) for healthcare environments has become essential.

The Environmental Performance and Cost of Innovative Technologies for Ductile Iron Foundry Production

The authors and collaborators have devised innovative technologies that decrease foundry costs, pollution, materials use, and energy. These include: (a) applying advanced oxidation to green sand and baghouse dust to diminish clay, coal, sand, volatile organic compounds (VOCs), and costs; (b) replacing phenolic urethane core binders with collagen-alkali silicate binders to diminish VOCs; (c) replacing coke with anthracite fines held together with biomaterial to reduce energy and costs. It is proposed by the authors that if a foundry were to concurrently employ all these innovative technologies (with 50% anthracite bricks), it could potentially diminish overall costs by 6.6%, life cycle energy costs by 15%, VOC pollution by 57%, sand by 85%, clay and coal by 50%, and iron scrap by 9%. These computations are per full-scale operations for advanced oxidation; and R&D results for replacing binders and coke. This paper also notes that when electricity comes primarily from coal fired power plants, electric induction furnaces consumes more life cycle energy than do cupolas for melting iron.

Full-Scale Demonstration of a Hybrid Hydrolyzed Collagen-Alkali Silicate Core Binder

A novel core binder system has been devised that is comprised of hydrolyzed collagen and alkali silicates. Cores that employ this hybrid binder were tested in a full-scale demonstration at a partner foundry. Among the 244 iron castings manufactured at this facility while using these hybrid binders, none of the iron castings were rejected as scrap due to core-related defects. The core regions of these iron castings exhibited no deformation, veining, or erosion from molten iron exposure. Moreover, these hybrid silicate-collagen cores demonstrated satisfactory shakeout during full-scale demonstrations. This hydrolyzed collagen-alkali silicate binder yielded cores that achieved a higher tensile strength and less hot distortion than conventional phenolic urethane binders.

Effects of microstructure and strength on wear performance in rough milling of austempered ductile iron

The machinability of various grades of austempered ductile iron (ADI) has been investigated for rough milling operations. ADI 900, ADI 1050 and ADI 1200 grades were commercially produced, commercially heat treated and machined under controlled conditions using coated carbide inserts with coolant in the laboratory. The milling performance of the various grades was compared to that of AISI/SAE 4340 with similar hardness. In this study, machinability characteristics relative to wear rate (ISO 8688-2) and machining forces were measured and related to initial microstructure and properties. These preliminary results have been used to establish initial rough milling machining guidelines for machining ADI with coated carbide milling inserts.

Understanding the Machinability of Austempered Ductile Iron (ADI)

Guidelines for production milling, turning and drilling of the standard grades of austempered ductile irons (ADI) have been established. Electron Backscatter Diffraction (EBSD) characterization has clearly shown that severe plastic deformation in the machining-affected-zone, ahead of and beneath the cutting tool, will cause strain-induced martensitic transformation of the austenite in the ausferrite structure that inhibits machinability. This phenomenon is particularly of concern during finish machining where small depths of cut are strongly influenced by surface martensite from prior machining passes.

Cast Iron Solidification with Non-Contact Acoustic Stimulation

The influence of non-contact ultrasonic vibration on the solidification of gray and ductile irons has been evaluated with and without inoculation. Conventional instrumented cooling curve analysis samples were cast under a wide range of non-contact acoustic stimulation conditions. Ultrasonic frequencies between 17 and 18 kHz were evaluated at transducer power ratings of 1800–3600 Watts with various horn designs. The air gap between the ultrasonic actuator and the surface of the solidifying metal was varied from 11–38 mm. The resultant solidification cooling curves as well as the microstructure after solidification were evaluated. Ultrasonic treatment of gray irons resulted in only slight changes in graphite morphology. However, in some cases, ultrasonic treatment of uninoculated gray iron changed the graphite shape from undercooled type D graphite to type A graphite. Ductile irons subjected to ultrasonic treatment showed a slight increase in nodule count and nodularity. Also, ultrasonic treatments resulted in a minor increase in overall solidification time. Further work is needed to identify the specific non-contact acoustic conditions that will have a significant effect on cast iron solidification behavior.

Non-Incineration Treatment to Reduce Benzene and VOC Emissions from Green Sand Molding Systems

Final report describing laboratory, pilot scale and production scale evaluation of advanced oxidation systems for emissions and cost reduction in metal casting green sand systems.