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Graduate Theses and Dissertations

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Full-Text Articles in Engineering Science and Materials

The Role Of Vec And Local Atomic Environment In Structural Transitions And Stability Of Complex Intermetallic Compounds Through Theoretical And Experimental Study Of Γ-Brasses, Stephanie L. Eveland Jan 2019

The Role Of Vec And Local Atomic Environment In Structural Transitions And Stability Of Complex Intermetallic Compounds Through Theoretical And Experimental Study Of Γ-Brasses, Stephanie L. Eveland

Graduate Theses and Dissertations

The fusion of computational and synthetic techniques provides a powerful investigative arsenal for a systematic consideration of the factors governing the structural makeup and observed physical properties of complex intermetallic compounds such as the non-uniform mixed sites in Mn2+xZn11-x, VEC driven structural transition in Mn5-yAl8-xZnx+y, and atypical atomic decoration of Cu9Al4 γ-brasses. Classic solid state synthetic techniques, self-flux techniques, as well as multiple structural characterization methods such as X-ray diffraction and electron microscopy were employed in the experimental portion of this work. Magnetic susceptibility measurements were utilized when appropriate in the study of the γ- brasses of Mn2 ...


Design And Development Of Cellulose Based Composites For The Built Environment, Melvin Glenn Veigas Jan 2019

Design And Development Of Cellulose Based Composites For The Built Environment, Melvin Glenn Veigas

Graduate Theses and Dissertations

Cellulose is a versatile material with numerous contemporary applications in textiles, food, and biomaterials. Contemporary research is focused on modifying the structural and thermal properties of cellulose to create novel composites with cellulose nano-crystals, lignocellulosic pulp, and foamed cellulose to name a few. Significant advances have been made in improving the properties of cellulose. Adding aligned cellulose nano-fibers to concrete to improve its mechanical properties or combining with polymers for better durability can lead to new applications specifically in design and construction. These new forms of cellulose through optimization and combination with other materials provide opportunities for reducing material usage ...


Study Of Combustion Performance Of Al/Ptfe B/Ptfe And B/Al/Ptfe Composites, Liyun Feng Jan 2019

Study Of Combustion Performance Of Al/Ptfe B/Ptfe And B/Al/Ptfe Composites, Liyun Feng

Graduate Theses and Dissertations

Metal particles like aluminum and boron are of great interest as additives to energetic materials due to their high gravimetric and volumetric heat of combustion. However, the ignition temperatures of metals are quite high and their burning rates which depend upon the surface area of the burning metal agglomerates are quite slow. The naturally formed oxide layer on the surface of metal particles can further inhibit their ignition and combustion by limiting fuel/oxidizer transport. The boron oxide layer on boron particles is of particular interest due to the strong diffusion barrier formed by its presence. However, the ignition temperature ...


Towards Understanding Material Characteristics Through The Additive Manufacturing Arc, Alden Watts Jan 2019

Towards Understanding Material Characteristics Through The Additive Manufacturing Arc, Alden Watts

Graduate Theses and Dissertations

The directed energy powder feed additive manufacturing (AM) process fabricates components with good quality, accuracy, and efficiency. However, this is a complex process and without careful consideration can lead to discontinuities in the final product such as porosity, cracks, or unfavorable microstructure. These material discontinuities may occur due to the limited understanding of the relationship between AM source materials and the evolution of the composition and microstructure during the deposition process. This makes it vital to study and correlate the composition, morphology, and characteristics of both the source material and of the final printed parts. In this research the properties ...


A Fast Fourier Transform Approach To Dislocation-Based Polycrystal Plasticity, John Thomas Graham Jan 2018

A Fast Fourier Transform Approach To Dislocation-Based Polycrystal Plasticity, John Thomas Graham

Graduate Theses and Dissertations

Polycrystalline materials serve as a basis for much of our current technology and will undoubtedly continue to serve a similar role in the future. Their mechanical properties depend not only on intragranular interactions between various defects, including the distribution of sizes and orientations of the grains, but also interactions with the grain boundaries. Modeling the mechanical behavior of polycrystals has become a standard part of the multiscale treatment of deformation. Currently, polycrystalline simulations are done through crystal plasticity methods, which are often informed through elastically isotropic single-crystal dislocation dynamics studies. These single-crystal studies, however, miss out on crucial effects due ...


Effect Of Nanoparticle Additives On The Tribological Behavior Of Oil Under Boundary Lubrication, Yosef Jazaa Jan 2018

Effect Of Nanoparticle Additives On The Tribological Behavior Of Oil Under Boundary Lubrication, Yosef Jazaa

Graduate Theses and Dissertations

In this study, three different nanoparticles (CuO, WC, WS2) of comparable nominal diameter, were added to a Polyalphaolefin (PAO) base oil to evaluate tribological response in the boundary lubrication regime. The concentration of particles was fixed at 1% by weight for this study and different surfactants (Oleic acid, polyisobutylene succinimide) and dispersion methods were employed to determine the impact on agglomeration and the observed tribological response. The results showed that of the methods studied, adding 10 % Oleic acid (OA) while sonicating the particles for 30 minutes reduced the agglomeration the most and adding 1% Oleic acid while sonicating the particles ...


Liquid-Phase Diffusion Bonding And The Development Of A Cu-Ni/Sn Composite Solder Paste For High Temperature Lead-Free Electrical Connections, Stephanie Michele Choquette Jan 2018

Liquid-Phase Diffusion Bonding And The Development Of A Cu-Ni/Sn Composite Solder Paste For High Temperature Lead-Free Electrical Connections, Stephanie Michele Choquette

Graduate Theses and Dissertations

After gathering sufficient microstructural evidence that a practical high-temperature lead-free solder could be produced through liquid-phase diffusion bonding (LPDB) of gas-atomized Cu-Ni powder blended with SN100C (Sn-0.7Cu-0.05Ni, wt.%) commercial solder powder, additional research was completed to enable design of a prototype composite solder paste. By reviewing several experimental alternatives to LPDB for use as replacements and improvements to the currently-used high-Pb solders (which will inevitably be banned by the EU’s RoHS directive), the choice to pursue the prototype solder paste research was verified. One key difference between this research and that of others is the method of ...


Environments-By-Design: Developing New Tools To Bring “Field Conditions” To The Laboratory, Kara Lind Jan 2018

Environments-By-Design: Developing New Tools To Bring “Field Conditions” To The Laboratory, Kara Lind

Graduate Theses and Dissertations

Maximizing agricultural yields is an urgent priority for our society as the world population will increase to 9 billion by 2050. Additionally, climate change could have detrimental effects on food supply and biomass production. Addressing these problems means considering the relationship the environment has on a plant’s development. The reality is though that there are few tools to plant scientists that can properly control and monitor the growing environment for plant. We believe that as engineers we can provide plant scientists with new tools which we call “environments by design”. These tools can control the environmental stimuli either abiotic ...


Study Of Collagen Organization In Cell-Laden Hydrogels And Animal Tissue Samples For Effective Tissue Engineering Scaffolds, Anuraag Boddupalli Jan 2018

Study Of Collagen Organization In Cell-Laden Hydrogels And Animal Tissue Samples For Effective Tissue Engineering Scaffolds, Anuraag Boddupalli

Graduate Theses and Dissertations

The interaction of biomaterials with biological systems is a complex process, that is triggered in response to implants and wounds. It is essential to understand the phases of wound healing response, particularly the interactions of immune cells such as macrophages and fibroblasts, with the local extracellular matrix which can influence implant acceptance or the restoration of the damaged wound site. Materials properties such as compressive modulus, surface geometry, functionalization, and topology can be tuned to modulate the inflammatory and fibrotic responses to wounds and implants. Naturally derived materials, such as alginate, are widely used biomaterials owing to their biocompatibility and ...


Gellan Gum Based Thiol-Ene Hydrogels With Tunable Properties For Use As Tissue Engineering Scaffolds, Zihao Xu Jan 2018

Gellan Gum Based Thiol-Ene Hydrogels With Tunable Properties For Use As Tissue Engineering Scaffolds, Zihao Xu

Graduate Theses and Dissertations

Gellan gum is a naturally occurring polymer that can crosslink in the presence of divalent cations to form biocompatible hydrogels. However, physically crosslinked gellan gum hydrogels lose stability under physiological conditions, which substantially limits the applications of these hydrogels in vivo. In order to improve the mechanical strength, we incorporated methacrylate into gellan gum and chemically crosslinked the hydrogel through three polymerization methods: step growth through thiol-ene photoclick chemistry, chain growth via photopolymerization, and mixed model in which both mechanisms were employed. Methacrylation was confirmed and quantified by proton nuclear magnetic resonance (1H NMR) and Fourier transform infrared spectroscopy (FTIR ...


Mixed Glass Former Effect In Borate And Thioborate Sodium-Ion Conducting Glass Systems, Brittany Curtis Jan 2018

Mixed Glass Former Effect In Borate And Thioborate Sodium-Ion Conducting Glass Systems, Brittany Curtis

Graduate Theses and Dissertations

As alternative energy sources continue to increase their production, there becomes a higher demand for cost-effective, safe, and energy efficient grid storage. Solid-state batteries are becoming of increased attention due to the demands for grid storage of alternative energy production, especially on days when these sources are under producing. As these solid-state batteries are being developed, many aspects of these batteries are being researched to optimize safety, cost-effectiveness and energy density. Current lithium-ion batteries have been scrutinized due to their safety concerns utilizing a flammable, liquid electrolyte. These concerns may be limited by replacing these organic, liquid electrolytes with an ...


Exploration Of Alnico Permanent Magnet Microstructure And Processing For Near Final Shape Magnets With Solid-State Grain Alignment For Improved Properties, Aaron Gregory Kassen Jan 2018

Exploration Of Alnico Permanent Magnet Microstructure And Processing For Near Final Shape Magnets With Solid-State Grain Alignment For Improved Properties, Aaron Gregory Kassen

Graduate Theses and Dissertations

Economic uncertainty in the rare earth (RE) permanent magnet (PM) marketplace as well as a quickly evolving electric drive motor market which has decided to leverage permanent magnet synchronous AC drive (PMAC) motors as the motor of choice, has driven renewed research in RE-free permanent magnets such as “alnico.” Alnico, essentially an Al-Ni-Co-Fe magnet alloy, was displaced for high energy density applications by RE-containing magnets in the 1970’s due to their high-energy performance and high coercivities.

The current PMAC development trajectory requires the development of a sustainable magnet material choice, which not only has impressive mechanical properties, such as ...


Computational Methods To Engineer Process-Structure-Property Relationships In Organic Electronics: The Case Of Organic Photovoltaics, Balaji Sesha Sarath Pokuri Jan 2018

Computational Methods To Engineer Process-Structure-Property Relationships In Organic Electronics: The Case Of Organic Photovoltaics, Balaji Sesha Sarath Pokuri

Graduate Theses and Dissertations

Ever since the Nobel prize winning work by Heeger and his colleagues, organic electronics enjoyed increasing attention from researchers all over the world. While there is a large potential for organic electronics in areas of transistors, solar cells, diodes, flexible displays, RFIDs, smart textiles, smart tattoos, artificial skin, bio-electronics, medical devices and many more, there have been very few applications that reached the market. Organic photovoltaics especially can utilize large market of untapped solar power -- portable and affordable solar conversion devices. While there are several reasons for their unavailability, a major one is the challenge of controlling device morphology at ...


Design And Performance Assessment Of Chip Seal Applications, Minas Guirguis Jan 2018

Design And Performance Assessment Of Chip Seal Applications, Minas Guirguis

Graduate Theses and Dissertations

The research evaluates the effectiveness of chip seal treatments when rational design, good materials, good construction and good agency oversight work together. The work investigates the effectiveness of chip seal applications using short-term and long-term quantitative test results from various chip seal roadways located in Oregon. Laboratory testing is utilized to understand and reflect the importance of aggregate characterization to ensure the success of performance. Findings show that chip seal preserved Oregon’s roadways by improving their surface texture properties and protecting them from additional cracking and deterioration.

The study further evaluates the effect of various parameters on chip seal ...


A Framework For Isogeometric-Analysis-Based Design And Optimization Of Wind Turbine Blades, Austin Herrema Jan 2018

A Framework For Isogeometric-Analysis-Based Design And Optimization Of Wind Turbine Blades, Austin Herrema

Graduate Theses and Dissertations

Typical wind turbine blade design procedures employ reduced-order models almost exclusively for early-stage design; high-fidelity, finite-element-based procedures are reserved for later design stages because they entail complex workflows, large volumes of data, and significant computational expense. Yet, high-fidelity structural analyses often provide design-governing feedback such as buckling load factors. Mitigation of the issues of workflow complexity, data volume, and computational expense would allow designers to utilize high-fidelity structural analysis feedback earlier, more easily, and more often in the design process. Thus, this work presents a blade analysis framework which employs isogeometric analysis (IGA), a simulation method that overcomes many of ...


Precision Radio-Frequency And Microwave Dielectric Spectroscopy And Characterization Of Ionic Aqueous Solutions, Amin Gorji-Bandpy Jan 2018

Precision Radio-Frequency And Microwave Dielectric Spectroscopy And Characterization Of Ionic Aqueous Solutions, Amin Gorji-Bandpy

Graduate Theses and Dissertations

Excessive amounts of chemicals and ions flowing into water sources, which are mainly due to efflux from agricultural lands, cause serious environmental and human-health related concerns. The lack of affordable and real-time monitoring systems for these contaminants limits effective conservation and management strategies. To establish a basis for developing an effective, fast, real-time, and affordable sensing system, dielectric spectroscopy has been applied to characterize agriculturally-relevant aqueous solutions of most commonly found ions in tile drainage water. Dielectric spectra of aqueous sodium chloride (NaCl), sodium nitrate (NaNO3), and sodium sulphate (Na2SO4) ionic solutions, which are the common pollutants found in agricultural ...


Fracture And Deformation Of Soft Materials And Structures, Zhuo Ma Jan 2018

Fracture And Deformation Of Soft Materials And Structures, Zhuo Ma

Graduate Theses and Dissertations

Soft materials and structures are very common in our daily life and industry products, but still shows great potential on many innovative applications. To make better use of them, we need a good understanding of the fracture and deformation of the materials. Starting from soft elastic foams, this paper proposes a scaling law for the fracture energy of soft elastic foam by using the analogy between the cellular structure and the network structure of rubbery polymers. To verify the scaling law, a phase-field model for the fracture processes in soft elastic structures is developed. The numerical simulations in two-dimensional foam ...


Use Of Cellular Automata-Based Methods For Understanding Material-Process-Microstructure Relations In Alloy-Based Additive Processes, Matthew Rolchigo Jan 2018

Use Of Cellular Automata-Based Methods For Understanding Material-Process-Microstructure Relations In Alloy-Based Additive Processes, Matthew Rolchigo

Graduate Theses and Dissertations

Deposition of metals through additive manufacturing has garnered research interest as of late due to the large range of potential industry applications. In particular, direct metal deposition processes such as Laser Engineered Net Shaping (LENS) have the ability to construct near net shape parts, open cellular structures, compositionally graded parts, and parts with improved mechanical properties over those manufactured via traditional methods such as casting and forging. To utilize additive processes to their full potential, it is imperative that the relationships among process parameters, development of the molten pool, microstructure, and properties are understood. Our goal in applying computational modeling ...


Solution Phase Synthesis And Computational Investigation Of Pnictide Based Nowotny-Juza Phases, Miles Arthur Burris White Jan 2018

Solution Phase Synthesis And Computational Investigation Of Pnictide Based Nowotny-Juza Phases, Miles Arthur Burris White

Graduate Theses and Dissertations

Filled tetrahedral semiconductors comprised of elements from group I, II, and V of the periodic table are of interest to the thermoelectric, photovoltaic, and battery fields due to their tunable electronic structures. However, until recently, the synthesis of these materials in a facile and scalable manner had remained elusive. In this thesis, we demonstrate the solution phase synthesis of three members of this class of compounds (LiZnP, LiCdP, and LiZnSb). Furthermore, we explore the presence of polytypism in these compounds and computationally investigate which additional phases would be expected to display polytypism. Finally, we closely investigate the phase space of ...


An Integrated Model For The Probabilistic Prediction Of Yield Strength In Electron-Beam Additively Manufactured Ti-6al-4v, Thomas Kiel Ales Jan 2018

An Integrated Model For The Probabilistic Prediction Of Yield Strength In Electron-Beam Additively Manufactured Ti-6al-4v, Thomas Kiel Ales

Graduate Theses and Dissertations

A complete model for the prediction of the yield strength of Titanium 6Al-4V in an additively manufactured component is presented herein. A thermal model is presented utilizing the ABAQUS simulation software to provide the process leg of the materials tetrahedron. The thermal model is fed into an implementation of the Langmuir equation that has been adapted for use in the simulation of the Electron-Beam Additive Manufacturing (EBAM) process. The predicted chemistry provided by the Langmuir equation for the Ti-6Al-4V alloy is then used in a phenomenological equation for the prediction of yield strength; a design probability curve is generated through ...


Simple Solutions To The Fabrication Of Textured And Porous Coatings, Xinchun Tian Jan 2018

Simple Solutions To The Fabrication Of Textured And Porous Coatings, Xinchun Tian

Graduate Theses and Dissertations

Functional coatings can change the surface properties of the substrate, add entirely new surface functionalities, or preserve the substrate. They provide solutions to many key engineering problems where different functionalities between the surface and the bulk are required. Among them, textured coatings are characterized by their surface roughness, film porosity, and surface chemistry. They are useful for applications ranging from superhydrophobic surfaces to artificial implants to thermal barrier coatings. However, the use and deployment of new coating methods are hampered in real applications due to the lack of a comprehensive consideration of the associated issues. In this thesis, two deposition ...


Interfacial Degradation Mechanisms With Applications To Polymer-Matrix Composites And Intergranular Stress Corrosion Cracking Of Steels, Denizhan Yavas Jan 2018

Interfacial Degradation Mechanisms With Applications To Polymer-Matrix Composites And Intergranular Stress Corrosion Cracking Of Steels, Denizhan Yavas

Graduate Theses and Dissertations

Structural interface property controls a wide spectrum of applications, ranging from the hybrid integration of dissimilar structural materials, to the enhanced physical properties of high performance engineering alloys. Practically, interfaces can be perceived as the weakest part of a heterogonous material or a structure. They are the most prone to environmental disturbances such as chemical or thermal, with significant deterioration of the structural integrity. Despite the large volume of literature on the topic, there remains a lack of proper understanding of degradation mechanisms of these interfaces. The challenge remains in the early detection of interfacial damage, and assessment of the ...


Ferrite Percentage Prediction Of Duplex Stainless Steels As A Function Of Cooling Rates, Longlong Liao Jan 2018

Ferrite Percentage Prediction Of Duplex Stainless Steels As A Function Of Cooling Rates, Longlong Liao

Graduate Theses and Dissertations

Highly alloyed CD3MWCuN was chosen to investigate the influence of cooling rates on the ferrite percentage of duplex stainless steels. It is known that cooling rate can influence the overall ferrite / austenite ratio, and achieving the proper balance of phases is crucial in producing a casting with suitable mechanical and corrosion properties. In this thesis cooling was initially investigated as a function of the solidification rate from the molten state and the rate of cooling from the homogenization temperature. It was quickly realized that given a suitable homogenization temperature and time the solidification cooling rate was of minimal importance. However ...


Biorenewable Polymer Thermoplastic Biocomposites, Mitchel M. Michel Jan 2018

Biorenewable Polymer Thermoplastic Biocomposites, Mitchel M. Michel

Graduate Theses and Dissertations

Biorenewable fillers have recently gained a greater focus in research to produce composites because of their unique properties, abundance, and diversity. These biorenewable fillers can include various terrestrial based plants naturally grown throughout the world. The focus of this work was on the natural fiber feedstocks that are created as waste streams from a wide range of industries, in particular agave fibers. Creating a composite composed of fibrous materials would have potential benefits that include cutting costs of composite products, decrease in density, increased strength and durability, and utilizing plant fiber waste streams for cost recovery. However, these natural fibers ...


Investigating The Effect Of Retained Austenite On Wear And Fatigue Behavior Of Aisi 8620 Steel, Sougata Roy Jan 2018

Investigating The Effect Of Retained Austenite On Wear And Fatigue Behavior Of Aisi 8620 Steel, Sougata Roy

Graduate Theses and Dissertations

Enhancing the operational life and reliability of drivetrain components via heat treatment routes is a long-studied topic of research. By varying parameters using heat treatment, the resulting attributes of the material such as hardness, residual stress, amount of retained austenite (RA), microstructure, grain size, grain orientation etc. can be varied. While the effect of hardness and residual stress on the resulting tribological properties of the steel is well known, the effect of RA is not as clearly understood yet. In this study, AISI 8620 steel samples were subjected to several heat treatment schemes using conventional and laser-based surface treatment routes ...


Multiscale Modelling Of Martensitic Phase Transformation: Example Of Si I To Si Ii, Hao Chen Jan 2018

Multiscale Modelling Of Martensitic Phase Transformation: Example Of Si I To Si Ii, Hao Chen

Graduate Theses and Dissertations

Martensitic phase transformations (PTs), amorphization, twinning, and dislocation motion are the main deformation mechanisms in many crystalline materials. However, the interaction between these material behaviors are not well understood. In this work, we try to understand the interaction between dislocation motion and PTs through multiscale modelling using density functional theory (DFT, in collaboration with Drs. Zarkevich and Johnson from Ames Laboratory), molecular dynamics (MD), continuum mechanics and concurrent atomistic-continuum (CAC) method. The following topics are discussed.

1. A continuum/atomistic approach for predicting lattice instability during martensitic PTs is developed for the general loading with an arbitrary stress tensor and ...


Investigating Degradation Pathways In Organic Solar Cell Materials, Satvik Shah Jan 2018

Investigating Degradation Pathways In Organic Solar Cell Materials, Satvik Shah

Graduate Theses and Dissertations

Thin film organic solar is a recent technology with tremendous potential – low cost materials, quicker manufacturing processes and synthetic tuning of organic materials to optimize material properties. Cell efficiencies > 12% have already been achieved. But the bottleneck problem this technology faces is instability. Performance of these cells degrades much faster than traditional solar cells. The degradation occurs on exposure to solar radiation, both through extrinsic ingress of moisture and oxygen as well as intrinsic degradation mechanisms.

One of the most common type of thin film organic cell with efficiency ~10% is PTB7:PCBM organic solar cell. Hence I have tried ...


Characterization Of Lithium Thiosilicophosphate Glasses Prepared By High Energy Ball Milling, Mark Anthony Paul Aguilar Jan 2018

Characterization Of Lithium Thiosilicophosphate Glasses Prepared By High Energy Ball Milling, Mark Anthony Paul Aguilar

Graduate Theses and Dissertations

An increasing demand for renewable energy has catalyzed investigations into improving battery technology. High energy density, longer cycling life, and safer battery materials are highly desirable. Research must go into developing advanced battery materials with properties designed for fast ionic conductivity, good chemical stability with the anode, and facile and low cost formability. Studying the short-range and intermediate-range atomic structures of materials will give insight into relationships between the atomic level structures of battery materials and their properties. In this research, the focus was upon developing new lithium ion conducting amorphous solid electrolytes in the compositional series 0.6 Li2S ...


Numerical Analysis Of A Non-Polymeric Double-Network Composite, Qitong Yao Jan 2018

Numerical Analysis Of A Non-Polymeric Double-Network Composite, Qitong Yao

Graduate Theses and Dissertations

Double-network hydrogels have drawn much attention for its combined mechanical properties of high stretchability and high mechanical strength and numerous studies have been conducted on these hydrogels with specific emphasis on gel compositions and mechanisms. Additionally, there are also reports on application of double-network gel mechanisms on macro composites which achieved similar results as in the gels. In this thesis, a series of numerical simulations on designing and tuning of a double-network hydrogel inspired non-polymeric composite formed with a coiled serpentine network acting as the long-chain and a solid plate acting as the short-chain are presented. The simulation results show ...


Cementitious Materials Subjected To Mechanical And Environmental Stressors: A Computational Framework, Shahin Hajilar Jan 2018

Cementitious Materials Subjected To Mechanical And Environmental Stressors: A Computational Framework, Shahin Hajilar

Graduate Theses and Dissertations

Despite the significant amount of concrete produced worldwide, there are long-standing issues with the long-term performance of concrete structures and facilities subjected to the mechanical and environmental stressors. To settle these issues, it is first imperative to understand the structural hierarchies and heterogeneous characteristics of concrete. While the structure of concrete at large length scales have been widely investigated in the literature, little knowledge is available about the structure, composition, and properties of the smallest building blocks of concrete, i.e., hydrated cement paste (HCP). This is mainly due to the complexities involved in the atomic structure of HCP phases ...