Artificial N 2 fixation via the electrocatalytic nitrogen (N 2 ) reduction reaction (NRR) has been recently promoted as a rational route towards reducing energy consumption and CO 2 emission as compared with the traditional Haber-Bosch process. Nevertheless, optimizing NRR relies on developing highly efficient electrocatalysts. Herein, we report on the reliable and reproducible synthesis of two promising electrocatalysts in either the presence or absence of Ketjenblack (KB), respectively, namely ZrO 2 -ZrN@KB and ZrO 2 -ZrN systems, synthesized through the nitriding of Zr. Both materials had never previously been considered for NRR, to the best of our knowledge. Nevertheless, both of these electrocatalysts incorporated a combination of tetragonal ZrO 2 , ZrON, and cubic ZrN and showed excellent activity and durability towards NH 3 formation. Moreover, the maximum NH 3 production rate of 84.1 μg h −1 mg −1 at −0.7 V vs. a reversible hydrogen electrode (RHE) was achieved with the ZrO 2 -ZrN electrocatalyst with an impressive Faradic efficiency of 21.2 % at −0.6 V vs RHE, indicating a high selectivity associated with the NRR. Additionally, the catalysts demonstrated excellent stability during the electrolysis process and recycling tests. We postulate that the combination of exposed active sites of ZrN and ZrO 2 likely contributes to the enhanced NRR performance attributed to ZrO 2 -ZrN.

Crystal violet (CV) is an organic chloride salt and a triphenylmethane dye commonly used in the textile processing industry, also being used as a disinfectant and a biomedical stain. Although CV is widely used, it is carcinogenic to humans and is retained by industrial-produced effluent for an extended period. The different types of metal oxide (MOx) have impressive photocatalytic properties, allowing them to be utilized for pollutant degradation. The role of the photocatalyst is to facilitate oxidation and reduction processes by trapping light energy. In this study, we investigated different types of metal oxides, such as titanium dioxide (TiO2), zinc oxide (ZnO), zirconium dioxide (ZrO2), iron (III) oxide (Fe2O3), copper (II) oxide (CuO), copper (I) oxide (Cu2O), and niobium pentoxide (Nb2O5) for the CV decomposition reaction at ambient conditions. For characterization, BET and Raman spectroscopy were applied, providing findings showing that the surface area of the anatase TiO2 and ZnO were 5 m2/g and 12.1 m2/g, respectively. The activity tests over TiO2 and ZnO catalysts revealed that up to ~98% of the dye could be decomposed under UV irradiation in <2 h. The decomposition of CV is directly influenced by various factors, such as the types of MOx, the band gap–water splitting relationship, and the recombination rate of electron holes.

Synthetic dye removal is a topic of increasing interest as textile recycling has become more popular in industries. While methods involving dye removal from wastewater effluent have been widely studied and reported on, research on decolorization of fabric itself remains quite unknown. In regard to the lack of research, this study presents cotton fabric samples dyed with crystal violet (CV) that were treated with varying concentrations of sodium hydroxide (NaOH). Fabric decolorization was studied using several characterization methods. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy data showed that the cellulose structure remained unchanged after CV and NaOH treatment. Characteristic CV peaks in the FTIR and Raman spectra were apparent only in the control sample, while the spectra of NaOH-treated samples were very similar to that of the cotton fabric. X-ray diffractometry (XRD) data also confirmed that the crystallite size of cellulose was not affected by CV and NaOH treatment. A visible violet hue remained in all NaOH-treated samples, though CV intensity was inversely proportional to NaOH concentration. The L*a*b* values were utilized to complement characterization results. As the concentration of NaOH was increased, the CIELAB parameters aligned more with those of the plain untreated fabric

Fabric waste has become an escalating problem that stems from the ever-shortening clothing lifecycle. Previous cotton recycling processes used mechanical methods to break the cotton down into fiber; this comes at the cost of compromised strength. Sodium hydroxide has long been used in the textile industry to increase dye absorption and luster through mercerization. In this paper, the deweaving of cotton muslin fabric was attempted using the chemical interactions of NaOH in combination with heat and mechanical forces through agitation. Different NaOH concentrations were tested to determine the optimum condition for fabric decomposition on a laboratory scale. Overall, the muslin fabric treatment with 0.5 M NaOH yielded the most promising results for fiber quality retention and chemical usage. The NaOH solution was shown to be feasible in effectively deweaving multiple muslin fabrics consecutively. While the deweaving process reduces the mechanical strength of the fabric, overall, the recycling method was successful in minimizing chemical waste and deweaving time.

To investigate reaction order and kinetic parameters of the reaction between crystal violet (CV) and sodium hydroxide (NaOH), various concentrations of the reactants were applied. The present work also verifies the unknown solid product produced under highly concentrated conditions. The reaction orders of CV and NaOH were determined to be 1 and 1.08 by pseudo rate method, respectively, with a rate constant, k, of 0.054 [(M−1.08) s−1]. In addition to pseudo rate method, the half-life approach was used to calculate the overall reaction order to verify the accuracy of pseudo rate method. The overall reaction order was determined to be 1.9 by the half-life method. The overall reaction order based on the two methods studied was approximately 2. The precipitate formation was observed when high concentrations of CV (0.01–0.1 M) and NaOH (1.0 M) were applied. Fourier transform infrared (FTIR) spectroscopy was used to compare the spectra of the precipitate generated and a commercial solvent violet 9 (SV9). Based on the FTIR spectra, it was confirmed that the molecular structure of the precipitate matched that of solvent violet 9.

Textile waste presents a major burden on the environment, contributing to climate change and chemical pollution as toxic dyes and finishing chemicals enter the environment through landfill leachate. Moreover, the majority of textile waste reaching landfills is discarded clothing, which could be reused or recycled. Here we investigate environmentally benign morphology changing of cotton textiles as a precursor for reintegration into a circular materials economy. At 50 °C using low concentrations of acids and bases, the interfiber structures of woven cotton were successfully degraded when treated with the following sequence of chemical treatment: citric acid, urea, sodium hydroxide, ammonium hydroxide, and sodium nitrate. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) reveal separation of the constituent fibers without depolymerization of the cellulose structure, and streaming potential measurements indicate that surface charge effects play a key role in facilitating degradation. The proposed reaction procedures show feasibility of effective waste-fabric recycling processes without chemically intensive processes, in which staple fibers are recovered and can be re-spun into new textiles.

In the past decade, there has been increasing attention paid to the recycling of cotton fabric waste. In the present study, different concentrations of sodium hydroxide (NaOH) ranging from 1 M to 4 M were used to thermomechanically deweave cotton fabric. The fabrics treated with 1 M NaOH and 2 M NaOH were partially deweaved, whereas those treated with 3 M NaOH and 4 M NaOH were completely deweaved. Fourier-transform infrared (FTIR) spectroscopy was applied to analyze the chemistry and structure of the cotton fabric. The FTIR spectra indicated that the structure of cotton fabrics treated with 1–2 M NaOH were similar to that of pristine fabric, while the presence of NaOH was observed. In the case of samples treated with 3–4 M NaOH, both the peak positions and the band intensities were changed, in addition to the formation of cellulose II. FTIR spectra for the recycled NaOH-treated cotton fabrics were compared, and no major structural changes were identified. A post-treatment with deionized (DI) water removed excess Na+ ions, with the sample showing a similar molecular structure to that of the pristine material. These results suggest the feasibility of recycling aqueous NaOH for post-washing treatment as a new method for recycling cellulosic fabric waste.

Environmentally friendly chromate-free, zirconium (Zr)-based conversion coating is a promising green technology for corrosion protection. Additives in the surface treatment provide critical functionalities and performance improvements; however, mechanistic understanding as to how the additives influence the coatings remains unclear. In this study, a new organic-inorganic hybrid Zr-based conversion coating combines copper (Cu) compounds and polyamidoamine (PAMAM), taking advantage of the complementary nature of organic and inorganic additives. A multimodal approach combining electron and X-ray characterization is applied to study the interaction of Cu2+ and PAMAM and the resulting impacts on coating formation. Adding PAMAM changed the surface morphology, thickness, distribution of Cu in the clusters, and void formation of the coatings. High PAMAM (100-200 ppm) leads to little conversion coating formation, and low PAMAM (0-25 ppm) shows voids formation under the coatings. Moreover, PAMAM incorporates in the coating in the form of a PAMAM-Cu complex with a higher concentration toward the surface, providing an organic layer at the surface of the coating. X-ray absorption near-edge structure (XANES) spectroscopy shows the difference between the conventional and the hybrid coating treatments in an alkaline solution to simulate the E-coat process, suggesting the contribution of PAMAM in the enhanced chemical stability in an alkaline environment. Therefore, an intermediate range of addition of PAMAM (50 ppm) is optimal to (1) avoid excessive voids formation, (2) promote some Cu cluster formation and thus enhance the Zr-based coating formation, and (3) incorporate organic components into the coating to improve the adhesion of the subsequent coatings. Overall, this work furthers our knowledge on the formation mechanism of an effective and environmentally friendly hybrid conversion coating for corrosion inhibition, demonstrating a critical processing-structure-property relationship. This study will benefit future development of green and effective surface treatment technology.

The hierarchical nature of additively manufactured materials necessitates a multimodal approach for quantifying microstructural features and corresponding chemical heterogeneities that ultimately impact their properties and performance. In laser powder-bed fusion (L-PBF) 316L stainless steel, corrosion behavior has been discussed in the context of chemical heterogeneities formed in the presence of these hierarchical microstructures. Here, we employ a suite of advanced synchrotron x-ray techniques and correlative transmission electron microscopy for the analysis of microstructure and chemical heterogeneities in L-PBF 316L as a function of printing speed. Our findings reveal an appreciable dislocation density consistent with the formation of a cellular dislocation microstructure in L-PBF 316L, which is correlated to spatial variations in the local Cr concentration and the formation of complex Mn7C3 nanoinclusions. Cyclic voltammetry experiments reveal that relative to wrought 316L, the printed samples exhibit either a comparable or marginally reduced susceptibility to uniform corrosion but with an increased affinity for pitting particularly in the samples printed at the highest speed with the largest dislocation density. Given the spatial correlations between regions of high dislocation density and the formation of chemical heterogeneities known to degrade corrosion performance, our findings demonstrate the impact of the microstructural defect state and its variation with printing speed on the resistance of L-PBF 316L to uniform and localized corrosion.

Additive manufacturing (AM) of alloys such as stainless steels has the potential to be a disruptive technology for design of complex structures which eliminates the potentially damaging effects of mechanical failure and localized corrosion associated with interfaces between separate parts (which can now be printed as part of a single assembly). In addition, increasingly complex geometries can be manufactured with nearly as much ease as simple ones, and new mechanisms for optimization and generative design can allow manufacturers to achieve significant material and weight savings. However, challenges remain, in particular due to the potential for material variabilities both between parts made with the same nominal build parameters and even within a single build, as the consistency in properties inherent in the commercial-scale forging of alloys to be machined into components is exchanged for the considerable advantages of on-site, distributed custom parts production. Our studies and related work by other groups indicates that this is clearly true in the case of corrosion susceptibility in AM alloys. By studying the relationship between build parameters and electrochemical properties, we propose that it will be possible to tailor alloys for enhanced corrosion properties. AM processes produce materials with hierarchical microstructures containing fusion boundaries at the macroscale, irregular grains and grain boundaries at the microscale, and subgrain dislocation structures at the nanoscale. In laser powder bed fusion (LPBF) formed 316L stainless steel structures, corrosion performance has been discussed in the context of chemical heterogeneities formed in the presence of these hierarchical microstructures. However, the large variability in reported measurements underscores the need for statistically significant microstructural data, which is often difficult to access via electron microscopy alone. In this presentation, we explore multi-modal synchrotron X-ray techniques for quantifying hierarchical microstructures and their connection to the underlying chemical distribution in 316L stainless steel. Our results show that the dislocation density depends on the printing conditions with implications for the chemical distribution at the nanoscale, which in turn may play a key role in inconsistent corrosion behavior. LPDF 316L samples formed at varying speeds using pulsed and continuous laser deposition are compared via cyclic polarization in 3.5% NaCl and 0.1M HCl solutions, as well as using standard methods for characterizing sensitization. Surface corrosion layers are characterized using laboratory-based X-ray photoelectron spectroscopy to determine the impact on passivity of the aforementioned microsegregation associated with process-induced microstructures. Corrosion rates and pit densities are then discussed to build a connection between printing conditions and corrosion performance vis-à-vis microstructural and chemical information from synchrotron measurements performed at Brookhaven National Laboratory (BNL), including high energy X-ray diffraction using the X-ray Powder Diffraction (XPD) beamline at the National Synchrotron Light Source-II (NSLS-II) which provided data on minor precipitate population(s), atomic structure and dislocation microstructures critical to corrosion behavior. In addition, heterogeneities in elemental composition data is provided by 2D X-ray fluorescence (XRF) and 2D X-ray Absorption Spectroscopy (XAS) nanometer resolution-mapping obtained at the Hard X-ray Nanoprobe (HXN) beamline at the NSLS-II and correlated with process-induced hierarchal structures via use of the microscopy facilities at the Center for Functional Nanomaterials (CFN). By employing a combination of multi-modal synchrotron characterization techniques, electron microscopy, and baseline testing protocol combined with electrochemical polarization experiments, we are able to study the the role of microstructure across multiple length scales on electrochemical properties and corrosion performance. Understanding the impact of microstructure and chemical heterogeneities on the susceptibility to pitting and intergranular attack will enable microstructurally-informed process optimization and materials design for enhancing the corrosion resistance of LPBF 316L stainless steel, with implications for AM and subsequent durability of alloys in general.

Metacomposites are an interesting field of research. This research is regarding tunable magnetic metacomposite formed using graphene and polyethylene (PE). Dielectric measurements show that as the concentration of graphene was increased in PE–graphene nanocomposites, the separation between graphene sheets decreased and negative dielectric constant was observed at low frequencies while high dielectric constant was observed at high frequencies of the applied field. The switching frequency could be controlled by changing the graphene concentrations. Small angle neutron scattering (SANS) analysis showed that the graphene assembled as fractals in the nanocomposites. As more graphene was incorporated into the nanocomposites, the fractals gave rise to percolation. We propose that the fractals are the building blocks for percolation phenomenon in the PE–graphene nanocomposites. Also, we observed ferromagnetism in the PE–graphene nanocomposites till 30% graphene. At 40% graphene the nanocomposite becomes a diamagnet. We attribute this to the topological defects induced in graphene by PE. Theses PE–graphene magnetic meta composites can have potential applications in battery technology.

Self-efficacy, or belief in one’s own ability to learn, is a key predictor of success for engineering students. I have developed and evaluated a scenario-based, task-specific on-line assessment instrument, the Self-Efficacy Assessment Survey (SEAS), and evaluated its use for preand post-assessment of students in a first year Introduction to Engineering course. Through a combination of the SEAS and other quantitative and qualitative assessment tools, incorporation of problem-based and active learning activities are found to enhance student self-belief in their ability to learn engineering-related material and accomplish certain engineering-related tasks. Use of scenario-based questions to measure student confidence levels (as has been done in the SEAS) provides a unique mechanism to gain insight into student self-efficacy, though questions must be carefully designed to limit the impact of extraneous factors on student responses.

The formation of ordered polydiacetylenes (PDAs) from conjugated triynes and longer polyynes has proven challenging due to the low stability of the starting materials and the possibility of varying regiochemistry for the polymerization. We report here the preparation of host-guest cocrystals of diiodohexatriyne and diiodooctatetrayne, each with a bis(nitrile)oxalamide host. Single-crystal X-ray diffraction studies show that the halogen-bonding interactions between the host and guest align the diiodopolyyne monomers with the proper parameters for 1,4-topochemical polymerization. Using Raman spectroscopy, solid-state C-13 MAS NMR, and single-crystal X-ray diffraction, we have demonstrated the formation of a single highly ordered PDA, poly(iodoethynyliododiacetylene) (PIEDA), from the 1,4-polymerization of diiodohexatriyne. Diiodooctatetrayne also forms ordered cocrystals, but attempts to form polymer from these crystals led to disordered species. This work represents the first reported single-crystal-to-single-crystal 1,4-polymerization of a conjugated triyne.

Furfuryl alcohol (C5H6O2) (FA) was used as the precursor for the synthesis of approximately 1.0 mm sized polymeric beads (PFAB) via suspension polymerization. The polymeric beads were carbonized and activated to synthesize porous carbon beads (PFAB/C/A) as an efficient adsorbent for gaseous volatile organic compounds (VOCs). Surface characterization tests revealed the material to be predominantly microporous with the specific surface area measured to be similar to 446 m(2)/g. Raman measurements revealed a graphitic characteristics of PFAB/C/A. Adsorption tests were performed in a fixed tubular packed bed adsorber under different operating conditions: amounts of adsorbents (2-6 g), gas flow rates (0.2-0.4 standard cc per min), adsorption temperatures (40-60 degrees C), VOC concentrations (2000-53,300 ppm) and types of VOCs (toluene and benzene). The tests revealed high adsorption capacities of the synthesized material i.e., 515 and 350 mg/g for toluene and benzene, respectively at 50 degrees C. This study has clearly shown that the biomass-based environmentally benign FA can be a potential alternative precursor to the synthetic petro-based polymers presently used for preparing carbon-based adsorbents.

Chemical conversion coatings can improve both anti-corrosion and adhesion properties in a wide range of applications. Due to the environmental and health issues of traditional chromate and phosphate coatings, more research has been carried out to develop environment-friendly and cost-effective chemical conversion coating. In this study, the coating formation mechanism of zirconium-based conversion coating and zirconium-polymer-based hybrid coating applied on carbon steel has been investigated. For zirconium-based coating, the kinetics of coating formation was characterized by the growth of the cluster size, as assessed by high-resolution SEM imaging; the evolution of the chemical composition was studied by Synchrotron X-ray Absorption Near Edge Spectroscopy (XANES) and X-ray Photoelectron Spectroscopy (XPS). Furthermore, the processing-structure-property correlation of an improved zirconium-based organic-inorganic “hybrid” coating was investigated. In both systems, corrosion tests have been carried out to understand the potential effects of post-coating processes. Overall, the study sheds light on the mechanism of the zirconium-based and hybrid coating formation, advancing the development of novel anti-corrosion technologies.

With the increase in popularity of 3D printing, an important question arises as to the equivalence between devices manufactured by standard methods vs. those presenting with identical bulk specifications, but manufactured via fused deposition modeling (FDM) printing. Using thermal imaging in conjunction with electron and atomic force microscopy, we demonstrate that large thermal gradients, whose distribution is difficult to predict, are associated with FDM printing and result in incomplete fusion and sharkskin of the printing filament. Even though these features are micro or submicron scale, and hence may not interfere with the intended function of the device, they can have a profound influence if the device comes in contact with living tissue. Dental pulp stem cells were cultured on substrates of identical dimensions, which were either printed or molded from the same PLA stock material. The cultures exhibited significant differences in plating efficiency, migration trajectory, and morphology at early times stemming from attempts by the cells to minimize cytoplasm deformation as they attempt to adhere on the printed surfaces. Even though biomineralization without dexamethasone induction was observed in all cultures at later times, different gene expression patterns were observed on the two surfaces. (Osteogenic markers were upregulated on molded substrates, while odontogenic markers were upregulated on the FDM printed surfaces.) Our results clearly indicate that the method of manufacturing is an important consideration in comparing devices, which come in contact with living tissues.

Engineered nanomaterials are playing an increasingly important role in many industries, from medical applications to aerospace to catalysis for energy production to infrastructure. Yet degradation of these materials not only impacts performance, but also has the potential to release reactive or hazardous materials to the environment. This chapter considers the potential mechanisms of environmental degradation, including loss of protective coatings, oxidation, chemical and biodegradation, and mechanical wear, and gives examples of how this can impact the robustness and environmental transformation of nanoparticles, nanostructured surfaces, and nanocomposites. The resulting impact on health and the environment is considered, as well as guidelines for engineering nanomaterials to limit this impact.

The role of surface engineering is to create a substrate/surface system which ensures dependability of structures manufactured for use in demanding service environments. This requires engineers to recognize the interrelationship of substrate composition, surface features (including defects and compositional heterogeneities), and surface treatments, and how these either enhance or mitigate the possible degradation mechanisms which can impact performance. This chapter discusses a few areas of manufacturing needs and then focuses on categories of surface engineering technology which have broad applicability or which by their nature demonstrate how research and development is leading to advances toward an ideal surface treatment.

The Use of Narrative in Undergraduate Engineering Education Many theories of engineering education identify methods to engage students and enhance learning that leverage mechanisms by which learning occurs. Most commonly, techniques such as problem-based learning, discovery learning, scaffolding, and hands-on or active learning have been promoted to enhance learning of engineering concepts and design methods. But less systematically studied are approaches that specifically address student motivation (and its assessment). One especially overlooked modality in this regard, despite (and probably also because of) its pervasive presence in instructional discourse, is the use of narrative. Cognitive psychologist and philosopher of education Jerome Bruner defined two modes of thinking that apply in this context: “logico-scientific” and “narrative,” (which are not mutually exclusive). The logico-scientific mode (and its attendant argumentative method) is clearly the dominant mode in engineering education for focusing on science, math, and logic to categorize and understand engineering principles and develop technological applications. But use of narrative can both improve motivation in learning and enhance mastery of engineering knowledge, and more important, it is ideal for helping students understand broader impacts (societal, ethical, historical) in engineering. The 20th century French philosopher Paul Ricoeur points out that narrative is built upon concern for the human condition, and ethical literary scholar Marshall Gregory contends that there is indeed no stepping outside of narrative contexts. Hence, by more explicitly and imaginatively using stories in engineering education, including case studies and cautionary tales, a more holistic approach may be achieved: one which happens to be reflected in ABET’s student learning outcomes. In addition, by exploring ‘missing narratives’ – voices and stories that are silenced or excluded in a given narrative – we can better understand the role of ethics and values in engineering designs and technological failures. We will discuss models for the use of narrative, and examine the results of the presenter’s use in undergraduate courses of disaster literature and science fiction (both reading and writing) to enhance the learning of engineering ethics, value sensitive design, and risk assessment. We will also discuss further roles for the concepts of narrative pedagogy in engineering (for example, having students tell stories of their own relationship with technology) and, in a broader sense, explore the potential for enhancing teaching and learning in engineering and the humanities through seeing engineering designs as narratives themselves.

Polylactic acid (PLA) is an organic polymer commonly used in fused deposition (FDM) printing and biomedical scaffolding that is biocompatible and immunologically inert. However, variations in source material quality and chemistry make it necessary to characterize the filament and determine potential changes in chemistry occurring as a result of the FDM process. We used several spectroscopic techniques, including laser confocal microscopy, Fourier transform infrared (FTIR) spectroscopy and photoacousitc FTIR spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) in order to characterize both the bulk and surface chemistry of the source material and printed samples. Scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) were used to characterize morphology, cold crystallinity, and the glass transition and melting temperatures following printing. Analysis revealed calcium carbonate-based additives which were reacted with organic ligands and potentially trace metal impurities, both before and following printing. These additives became concentrated in voids in the printed structure. This finding is important for biomedical applications as carbonate will impact subsequent cell growth on printed tissue scaffolds. Results of chemical analysis also provided evidence of the hygroscopic nature of the source material and oxidation of the printed surface, and SEM imaging revealed micro- and submicron-scale roughness that will also impact potential applications.