Effect Of Substrate Chemistry Research Articles

Microstructure evolution and hardness of hot dip aluminized coating on pure iron and EUROFER 97 steel: Effect of substrate chemistry and heat treatment

EUROFER 97 steel, a variation of reduced activation ferritic-martensitic (RAFM) steel, is considered to be a potential material for the first wall of fusion reactor. Aluminide diffusion barrier coatings offer an effective solution to mitigate corrosion and tritium permeation in the first wall. However, the performance of the coating is influenced by the nature of intermetallic phases and their microstructure. In order to critically understand the phase evolution during both hot dip aluminizing (HDA) process and subsequent heat treatment, experiments were performed on (i) pure iron and (ii) EUROFER 97 steel. The samples were hot dip aluminized at 973 K in an inert Ar-5% H2 atmosphere. Detailed metallurgical analysis using backscattered electron detector, electron probe microanalyzer and electron backscattered diffraction technique was performed to examine the evolution of phases and microstructure. It was noted that Fe2Al5 is the major phase forming in both the cases during HDA. Subsequent heat treatment involving solution treatment at 1253 K and ageing at 1033 K led to transformation of Fe2Al5 to FeAl2, FeAl(Cr) and α-Fe(Al, Cr) in HDA EUROFER steel due to interdiffusion of Fe, Al and Cr. However, no trace of FeAl2 could be detected in HDA iron. Thicker and wavy interdiffusion layers were formed in HDA iron, whereas in HDA EUROFER steel near-planar interfaces were present. Micro-pores were observed in all heat treated samples. It was found that the hardness of the phases determined using nanoindentation are in the order of FeAl2(Cr)>Fe2Al5(Cr)>Fe2Al5>FeAl(Cr)>FeAl>α-Fe(Al, Cr)>α-Fe(Al).

Crystallization Mechanism and Charge Carrier Transport in MAPLE-Deposited Conjugated Polymer Thin Films.

Although spin casting and chemical surface reactions are the most common methods used for fabricating functional polymer films onto substrates, they are limited with regard to producing films of certain morphological characteristics on different wetting and nonwetting substrates. The matrix-assisted pulsed laser evaporation (MAPLE) technique offers advantages with regard to producing films of different morphologies on different types of substrates. Here, we provide a quantitative characterization, using X-ray diffraction and optical methods, to elucidate the additive growth mechanism of MAPLE-deposited poly(3-hexylthiophene) (P3HT) films on substrates that have undergone different surface treatments, enabling them to possess different wettabilities. We show that MAPLE-deposited films are composed of crystalline phases, wherein the overall P3HT aggregate size and crystallite coherence length increase with deposition time. A complete pole figure constructed from X-ray diffraction measurements reveals that in these MAPLE-deposited films, there exist two distinct crystallite populations: (i) highly oriented crystals that grow from the flat dielectric substrate and (ii) misoriented crystals that preferentially grow on top of the existing polymer layers. The growth of the highly oriented crystals is highly sensitive to the chemistry of the substrate, whereas the effect of substrate chemistry on misoriented crystal growth is weaker. The use of a self-assembled monolayer to treat the substrate greatly enhances the population and crystallite coherence length at the buried interfaces, particularly during the early stage of deposition. The evolution of the in-plane carrier mobilities during the course of deposition is consistent with the development of highly oriented crystals at the buried interface, suggesting that this interface plays a key role toward determining carrier transport in organic thin-film transistors.

Substrate chemistry regulates the surface phase separation of polyurethane films

The effect of substrate chemistry on surface phase separation of polyurethane films were investigated by using self-assembled monolayer (SAM) with chemically different modifications, i.e. hydroxy (–OH) and methyl (–CH3) end groups. Results showed that hydrophilic (–OH) and hydrophobic end groups (–CH[Formula: see text] could respectively promote the aggregation of hard and soft segments at polyurethane–substrate interface, which further regulates the phase separation of polyurethane surface that contacts the substrate. The aggregation of hard segments tended to enhance the surface smoothness of polyurethane films, especially on hydrophilic substrates with hydroxy modification. Further analysis of tensile testing revealed that the regulation of surface phase separation had no effect on the shape memory effect of polyurethane films. These findings suggest that the chemical properties of the substrates could regulate the phase separation and may provide some guidance on the design of specific polyurethane with desired morphology and properties.

Correction to “Effect of Substrate Chemistry on the Bottom-Up Fabrication of Graphene Nanoribbons: Combined Core-Level Spectroscopy and STM Study”

Correction to “Effect of Substrate Chemistry on the Bottom-Up Fabrication of Graphene Nanoribbons: Combined Core-Level Spectroscopy and STM Study”

Effect of Substrate Chemistry on the Bottom-Up Fabrication of Graphene Nanoribbons: Combined Core-Level Spectroscopy and STM Study

Atomically precise graphene nanoribbons (GNRs) can be fabricated via thermally induced polymerization of halogen containing molecular precursors on metal surfaces. In this paper the effect of substrate reactivity on the growth and structure of armchair GNRs (AGNRs) grown on inert Au(111) and active Cu(111) surfaces has been systematically studied by a combination of core-level X-ray spectroscopies and scanning tunneling microscopy. It is demonstrated that the activation threshold for the dehalogenation process decreases with increasing catalytic activity of the substrate. At room temperature the 10,10′-dibromo-9,9′-bianthracene (DBBA) precursor molecules on Au(111) remain intact, while on Cu(111) a complete surface-assisted dehalogenation takes place. Dehalogenation of precursor molecules on Au(111) only starts at around 80 °C and completes at 200 °C, leading to the formation of linear polymer chains. On Cu(111) tilted polymer chains appear readily at room temperature or slightly elevated temperatures. An...

The optimal combination of substrate chemistry with physiological fluid shear stress

Osteoblasts on implanted biomaterials sense both substrate chemistry and mechanical stimulus. The effects of substrate chemistry alone and mechanical stimulus alone on osteoblasts have been widely studied. This study investigates the optimal combination of substrate chemistry and 12dyn/cm2 physiological flow shear stress (FSS) by examining their influences on primary rat osteoblasts (ROBs), including the releases of ATP, nitric oxide (NO), and prostaglandin E2 (PGE2). Self-assembled monolayers (SAMs) on glass slides with –OH, –CH3, and –NH2 were employed to provide various substrate chemistries, whereas a parallel-plate fluid flow system produced the physiological FSS. Substrate chemistry alone exerted no observable effects on the releases of ATP, NO, and PGE2. Nevertheless, when ROBs were exposed to both substrate chemistry and FSS, the ATP releases of NH2 were upregulated about 12-fold compared to substrate chemistry alone, while the ATP releases of CH3 and OH was similarly increased 7-fold at the peak. Similar trends were observed for the releases of NO and PGE2. The expressions of ATP, NO, and PGE2 followed the pattern of NH2-FSS>Glass-FSS>CH3-FSS≈OH-FSS. ROBs on NH2 produced the optimal combination of substrate chemistry with the physiological FSS. The F-actin organization and focal adhesion (FA) formation of ROBs on various SAMs without FSS were examined. NH2 produced the best results whereas CH3 and OH produced the worst ones. Inhibition of FAs and/or disruption of F-actin significantly decreased the releases of FSS-induced PGE2, NO, and/or ATP. Consequently, a mechanism was proposed that the best F-actin organization and FA formation of ROBs on NH2 lead to the optimal combination of substrate chemistry with the 12dyn/cm2 physiological FSS. This mechanism gives guidance for the design of implanted biomaterials and bioreactors for bone tissue engineering.

Keratinocyte-fibroblast paracrine interaction: the effects of substrate and culture condition

Interactions between epidermal–dermal cells via soluble factors provide important signals in regulating the reepithelialization of wounded skin. For example, keratinocytes regulate the expression of keratinocyte growth factor (KGF) in fibroblasts through the release of interleukin-1beta (IL-1β). In this study, a previously developed polyethyleneglycol-based interpenetrating network (IPN) system was utilized as a platform for the delivery of keratinocyte-active factors. The effect of substrate chemistry, culture condition, and the delivery of exogenous keratinocyte-active factors on the keratinocyte behavior and the keratinocyte-fibroblast paracrine relationship was delineated. Adherent keratinocyte density on TCPS and glutaraldehyde-fixed gelatin hydrogels but not on IPN was significantly increased with culture time in the presence of growth supplements independent of the released KGF from the gelatin hydrogel and IPN. In the presence of fibroblasts, adherent keratinocyte density on gelatin hydrogels was higher than that without fibroblasts. This phenomenon was not observed on IPN and polycarbonate membrane. In summary, the delivered exogenous huKGF (i.e., released from a biomaterial matrix) operates in tandem with fibroblasts in regulating keratinocyte activation (i.e., IL-lβ release and adhesion) in a surface-dependent manner. Immunoassay analysis of cell culture keratinocyte-fibroblast paracrine relationship as characterized by IL-1β and KGF could not be established in the presence of IPNs, 0.1% glutaraldehyde-fixed gelatin hydrogels, and polycarbonate membranes.

Disentangling Moss Species Limitations: The Role of Physiologically Based Substrate Specificity for Six Species Occurring on Substrates with Varying pH and Percent Organic Matter

Abstract Substrate specificity has been pinpointed as key to understanding plant species distributions and to differentiating types of plant rarity. Substrate specific distribution patterns (e.g., calcicole and calcifuge) are particularly prevalent among bryophytes. Many authors have suggested that the effects of substrate chemistry might be most important during the establishment stage. The connection between substrate sensitivity during establishment and the degree of substrate specificity (i.e., substrate breadth) measured for adult plants in the field was explored for three rare moss species, Mielichhoferia macrocarpa, Didymodon johansenii, and Mnium arizonicum and three taxonomically allied common species, Bryum pseudotriquetrum, Didymodon rigidulus var. gracilis, and Mnium spinulosum, respectively. Substrate pH and organic matter content were determined for field samples to quantify species substrate breadths. These observed specificities were tested by comparing regeneration of gametophyte fragment...

Decomposition and nitrogen mineralization from biosolids and other organic materials: relationship with initial chemistry.

Biosolids are effective forest fertilizers. In order to facilitate their use it is important that one be able to predict the amount and rate of mineralization of nutrients, particularly nitrogen, and the relationship between substrate chemistry and N release. We examined the relationships between substrate quality and nitrogen release in a variety of organic materials. Rates of decomposition and net N mineralization from four biosolids, wheat straw, paper fines, and Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] needle litter were measured during 391-d incubations in a greenhouse, and at two field sites in wet coastal and dry interior forests. Decomposition rates were best predicted by a model incorporating the ratio of carbon to organic matter. The decomposition model extrapolated well to the field when site-specific correction factors were applied. There was a weak relationship between rates of decomposition and net N mineralization. Rates of net N mineralization were best predicted by a model incorporating the initial organic N concentration and the proportion of phenolic C determined from solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. The mineralization model extrapolated less well to the field, but the effect of substrate chemistry was still apparent. Among the four biosolids there was a strong correlation between organic N concentration and indices or protein determined from 13C NMR, suggesting that these protein indices may be useful for predicting N mineralization from biosolids. There was some evidence that the protein content and N mineralization in biosolids may be predictable from the sewage treatment process employed.

Improved underlayers for acid amplified resists

Abstract Acid amplified resists represent a major development in lithography in the last few years. It is recognized that for precise CD control with these resists in device manufacturing, it is required that the processing environment be free of any basic contaminants. Top coat protection of the resist films in conjunction with rigorous exclusion of basic chemical vapors in the work area has been recommended to minimize the effects of environmental contaminants. Another important variable in determining the resist performance is the effect of substrate chemistry which has received little attention in the literature. This paper provides an understanding of these effects and gives a general method to circunmvent the problem.