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In 2003, Professor Youngblood joined the School of Materials Engineering at Purdue University. Promoted to Associate Professor in 2009 and Professorin 2015, he uses his polymer expertise to investigate nanotechnology, surface science, advanced processing and biomaterials. Of late, he has beenspecifically interested in ceramic processing using methods similar to those for polymeric materials, composites and fabrication, sustainability ofmaterials, cellulose nanocomposites, cementitious materials, Additive Layer Manufacturing (3D printing), and durable anti-ice coatings.

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Polymer and Surface Science in the Youngblood Group

Advanced Ceramic Processing

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RESEARCH HIGHLIGHT

Sustainable Nanotechnology Functional Materials

SUSTAINABLE FLAMERETARDANTSHalogenated flame retardants (HFRs) areused in a variety of polymer systems.However, there is currently concern abouttheir negative effects on health and theenvironment as bioaccumulation of HFRs inhumans can lead to a variety of health issues.The goal of this project was to develop andstudy biologically-sourced chemicals asalternative FRs based on biomimetic design.

Cured-in-place pipe (CIPP) is the resin saturated fabric liner that is installedinto a deteriorated pipeline and then cured using steam, hot water or UVLight. Our goal is to analyze possible environmental effect during, and afterinstallation of cured-in-place pipe (CIPP).

ADVANCED POLYMER COMPOSITES

Before CIPP Installation After CIPP Installation

i.) Fiber SpinningCommercially available fiber spinning methodsare being explored to produce high strength, highstiffness nanocellulose reinforced commoditypolymer fibers where nanoparticle alignment andnanoparticle concentration are crucial toperformance. We shown that CNC and CNFaddition can increase modulus and strength ofthe fibers and can also add as a crystallinitynucleant.

ii.) Hygroscopic Swelling of CNC FilmsHygroscopic swelling is commonly characterized by the coefficient ofhygroscopic swelling (CHS), which correlates the degree of expansion of amaterial to the mass intake of water as a function of humidity. CHS of self-organized and shear-oriented CNC films was determined by capturinghygroscopic strains produced by water vapor intake in equilibrium. Here, weuse contrast enhanced microscopy digital image correlation (CEMDIC) todetermine CHS as a function of CNC alignment.

500 µm

Fast extrusion

Polyvinyl alcohol/CNC Fibers

i.) LaminatesLaminates are made up of stackedlayers of bio-friendly cellulosenanofibrils (oxidized CNF ormechanically fibrillated CNF) asthe primary component with theaddition of a thermoplasticpolymer binder layer to achievehigh strength, transparency andtoughness.

ii.) NanocompositesCNC and CNF are potentialadditives and fillers for variouspolymer systems where it can actas a structural reinforcement,promote nucleation, and enhancethermal, mechanical and transportbarrier properties.

3D Printing Cement with Controlled ArchitectureAdditive manufacturing offers unique opportunities to design and testarchitectured cement-based materials. We have shown that “Bouligand”architectures with a pitch angle of 45° demonstrate a higher specific strengththan cast specimens over a wide range of porosity. As well, we have shownthat some architectures can provide flexibility, much higher toughness, andcrack deflection in brittle cementitious materials.

Professor Youngblood’s ceramic research focuses on structure-property-processing relationships of ceramic materials. In particular, we areinvestigating novel processing approaches for forming (ballistic and hightemperature) ceramics and cements into complex shapes using powder-polymer suspensions as well as preparing transparent ceramic via alignment of𝛼𝛼 -alumina platelets for armor applications.

AQUEOUS BASED CERAMIC-POLYMER PROCESSINGi.) Additive ManufacturingCurrent bulk ceramic forming processes are limited to simple structures orrequire secondary machining to add intricate features. AdditiveManufacturing (AM) can be used with aqueous ceramic-polymer suspensionswith tailored rheological properties to produce complex geometries. Presently,we are developing ceramic suspensions from different ceramic systems (B4C,Al2O3, Si3N4, ZrB2) for use in AM.

By tailoring flow properties of aqueousceramic-polymer suspensions, injectionmolding can be accomplished at roomtemperature to produce samples withcomplex geometries. Combined withpressureless sintering, this results inparts with high relative densities andmechanical properties comparable tosamples prepared by traditional formingmethods.

STRUCTURED MATERIALSTransparent CeramicsCurrent methods for producing transparent ceramics involve extremely highsintering temperatures and/or complex and very large magnetic fields to alignceramic particles. By compression-molding a mixture of platelet-grain alpha-alumina in a thermoplastic polymer, a high degree of crystallographicalignment can be achieved. Subsequent binder burnout and densification willyield a dense, transparent, polycrystalline ceramic.

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ii.) Room-Temperature Injection Molding

Injection molding of alumina slurry.

3D printing of a boron carbide slurry 3D printed sintered boron carbide part

Schematic representation of moisture sorption of CNC films

Shadow visible behind hot-pressed alumina

Top: Architectured cement – a. honeycomb, b. twisting layers, c. hollow box with internalstructure, d. double-modulus cement “spring”, e. Bouligand structure with 8 degree twist.Bottom: MOR vs density curve showing 3D printed architectures show anomalous strengthbehavior.

Flame retardancy of natural products compare favorably to commercial FRs

Structure of Tannic Acid

Structure of Lignin (from Wikipedia)

Water culvert before and after CIPP repair

Mutliphasic mixture of VOCs, water, and partially cured polymer are released to the environment during steam curing of CIPP.

CNC AND CNF PROCESSING

NEW COMPOSITES

FUNDAMENTAL PROPERTY MEASUREMENT

Platelet-grained alumina

Optical birefringence method for anisotropy determination

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Sustainable nanotechnology in the Youngblood group is primarily focused oncellulose nanomaterials (CN), which are sustainable, non-toxic, high strength,high stiffness, and derived from biomass. These materials are comprised ofCellulose Nanocrystals (CNCs) – rod-like liquid crystalline particles of 100nmlength and Cellulose Nanofibrils (CNFs) – flexible fibrils of microns in length.Research into CNC and CNF spans new materials, new processing methods andfundamental property determination.

Polylactic acid/CNC Fibers

CNC R2R coating on PET film

CNF laminates are highly transparent

20 bilayer CNF laminate structure

CNC Epoxy nanocomposites show good dispersion

CHS of CNC films with different CNC alignments

CEMDIC image with CHS at an angular increment of 45o

i.) Optical Birefringence for Anisotropy MeasurementBirefringence has been investigated for the determination of crystal orientationof a CNC film. The prime focus of our study is to establish a simple and lowcost experimental technique using a standard UV–Vis spectrometer todetermine the order parameter (S) for both isotropic and anisotropicconfigurations. The transmitted light intensity of CNC films between crosspolarizers for the bright and dark fields were measured to determine the lineardichroitic ratio, which were used to calculate the order parameters of differentcrystalline arrangements.

Transmittance peak intensity for a anisotropic film

ii.) Roll to Roll (R2R) Continuous FabricationA large-scale continuous manufacturing processfor cellulose nanocrystal (CNC) and CNCcomposite coatings on a flexible substrate wasdeveloped in this work. In microgravure R2R, thecoating thickness (from 2µm to 6µm) and CNCalignment can be controlled via processparameters and ink viscosity. Such processing isuseful for producing barrier films to preventoxygen, CO2 and water transmission for foodpackaging and anti-bleed layers for printing.

CNCs increase Degree of Hydration (DOH) in cement

We have used these results to conduct field tests

Increased DOH increases strength in cement

CNCs reduce cement paste yield stress, yet improvedegree-of-hydration (DOH) all at very low dosages.Lowered yield improves workability, while increasedDOH increases strength. We are investigating theorigin of these observations and how to improve CNCperformance. We are now trying to apply CNCadditives at the macro level during field tests.

ADDITIVES FOR CEMENTITIOUS MATERIALS

Sustainable energy sourcesneed storage solution toreduce intermittency andprovide stable power.However, currentelectrochemical storage areeither too expensive or haveto low capacity for suchuse. Here we investigateearth abundant materialssuch as biomass, sulfur andcommon metals such assodium integrated withprocessing to lower cost.

SUSTAINABLE MATERIALS FOR ENERGY STORAGE

a. Waste biomass such as pistachio shell can becarbonized and used for batteries. b. Performancedepends on carbonization temperature.

Functional Materials research in the Youngblood group seeks to create andinvestigate materials, additives and components that are “active” in some way –chemically, electrochemically, thermally, etc. The application fields can spanthe gamut of cement, batteries , polymer additives, anti-ice coatings and others.