Untreated Reference Samples Research Articles

Investigation of surface structuring and oxidation performance of Inconel 718 superalloy by laser remelting with different patterns

The current paper deals with the effect of CO2 laser remelting on the surface structuring and oxidation performance of Inconel 718 superalloy, pointing out different laser-induced surface patterns that make a difference in their oxidation properties vital for high-temperature applications. Surface roughness, microstructure, and oxidation behavior characterization were performed using 3D optical profilometry, SEM, and XRD techniques. The oxidation tests conducted at 1000 °C for 24 h have revealed that remelted surfaces offered better oxidation resistance compared to untreated samples. Notably, the patterned sample showed the lowest weight gain under oxidation, and a parabolic regime in oxidation occurred after 100 min; while in an untreated reference sample, this appears only after 200 min. This improvement in performance results from the formation of a chromium-rich oxide layer on the melt pools, which acts as an effective barrier against further oxidation. The findings show that laser remelting, especially with grid-like surface patterns, results in an improvement in both durability and high-temperature performance of Inconel 718; therefore, it is apparently a very promising technique for lifespan extension of industrially relevant materials.

Investigation of Impregnation Approach of Zinc Oxide Nano-Dispersions for Potential UV Stabilization in Abies alba and Fagus sylvatica

As biological material, wood is distinctly affected by to various environmental influences during use. Reductions in durability can come from ultraviolet (UV) radiation, insects, fungi, and microorganisms in both exterior and interior applications. Wood can be easily protected from living organisms via the control of moisture content; however, UV radiation is not so easily managed. Wood components subject to this degradation are damaged and decomposed at a molecular level leading to deterioration of surface quality, especially in visible application areas. A potential remedy to this is using the UV-stabilizing properties of zinc oxide nanoparticles. Zinc oxide nano-dispersions based on propylene glycol (PG) were introduced into the microscopic structure of fir (Abies alba) and beech (Fagus sylvatica) wood by whole-cell impregnation to overcome problems associated with surface coatings. In this work the material uptake of ZnO nano-dispersions in concentrations of 1%, 2%, and 3% w/v were investigated and their effect on the stability of the optical appearance to UV exposure in short-term weathering were evaluated. Untreated reference samples showed significant photo-yellowing. A 1% w/v ZnO dispersion significantly increased the UV stability of treated surfaces. It was found that the uptake of the nano-dispersions was independent of the proportion of ZnO, and that the impregnating agents penetrated fir wood (about 200%) stronger than beech wood (about 70%). Already, a 2% w/v ZnO nano-dispersion led to a saturation of ZnO in the cell structure of the treated wood, for fir as well as beech, and no further ZnO uptake was achieved with 3% w/v nano-dispersions. Scanning electron microscopy shows an agglomeration of ZnO-NP in the cellular pathways impacting penetration, reducing leachability at higher concentrations.

Kinetic studies on photo-degradation of thermally-treated spruce wood during natural weathering: Surface performance, lignin and cellulose crystallinity

The hygroscopic behavior of wood-based materials is undoubtedly influential on the material surfaces exposed to climatic conditions. The paper aims to kinetically investigate the photo-degradation and surface characteristics of thermally-treated spruce wood at 185 °C and un-treated (reference) sample through 2 years of natural weathering. Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy and X-ray diffraction (XRD) were employed to investigate the chemical changes occurred in lignin and crystalline structure of cellulose as a function of outdoor exposure. Detailed measurements of morphological and surface changes were evaluated during exposing periods. Surface wettability and roughness as well as cracks were increased for all samples due to weathering as the exposure time extended. Prominently, the color changes (ΔE) and photo-chemical reactions were found to be negligible in short-time weathering thanks to thermal modification. In the long–term exposing, more OH-bonds caused by lignin leaching out resulted in presence of cracks and the affinity for water on reference sample. Degree of crystallinity significantly decreased by 12.7% in thermally treated wood and 18.3% in reference sample after long-term weathering while, the crystallinity index of thermally-treated wood increased to 4.7% in 6-month weathering. Hence, the amorphous structures and chromophores groups appeared on the reference wood at a faster and more intense rate during exposing time. Thermal treatment delayed photo-yellowing as well as color change of wood due to up-graded lignin and cellulose crystallinity through a photo-stable structure. Accordingly, kinetic studies ascertained the service-time of wood products in exterior uses.

Controlled surface crystallization of lithium‐zinc‐alumosilicate glass‐ceramics using thermal poling

AbstractTwo glasses from the lithium‐zinc‐alumosilicate (LZAS) glass–ceramic system were thermally poled at 0.5 and 0.9 Tg and subsequently crystallized in heat‐treatment. Underneath the anode‐faced surface of the as‐poled glasses, a lithium depletion layer was found with layer thicknesses up to 15 μm. Between the depletion layer and the bulk, an accumulation of sodium was measured. Structural alterations underneath the anode‐faced and cathode‐faced surfaces of the crystallized glasses were examined using grazing‐incidence X‐ray diffraction and scanning electron microscopy. A mainly amorphous layer was observed on all anode‐faced surfaces, each containing only small amounts of high‐quartz solid solution (high‐quartz s.s.). The low crystalline content was attributed to a reduced lithium content when compared to the untreated reference. Additionally, in one sample a keatite solid solution (keatite s.s.) formed in the anode‐faced surface with its phase content increasing with the poling temperature. The transformation of high‐quartz s.s. to keatite s.s. is facilitated by a silica‐rich glass composition beneath the anode‐faced surface. Underneath the cathode‐faced surface high crystalline contents were obtained, which even exceed the crystalline phase contents found in the untreated reference samples. In combination with an observable larger lattice parameter of the high‐quartz s.s. phase, it could be assumed that Li+ cations enrich at the cathode‐faced surface. The enrichment of Li+ cations on the cathode‐faced and their depletion on the anode‐faced surface lead to different particle sizes. Small grains were observed underneath the amorphous layer in the anode‐faced surface, while larger grains with an overall broader particle size distribution were found on the cathode‐faced surface.

Long-Term Effect of Low-Frequency Electromagnetic Irradiation in Water and Isotonic Aqueous Solutions as Studied by Photoluminescence from Polymer Membrane.

The swelling of a polymer membrane NafionTM in deionized water and isotonic NaCl and Ringer’s solutions was studied by photoluminescent spectroscopy. According to our previous studies, the surface of this membrane could be considered as a model for a cellular surface. Liquid samples, in which the membrane was soaked, were subjected to preliminary electromagnetic treatment, which consisted of irradiating these samples with electric rectangular pulses of 1 µs duration using platinum electrodes immersed in the liquid. We used a series of pulses with a repetition rate of 11–125 Hz; the pulse amplitudes were equal to 100 and 500 mV. It turned out that at certain pulse repetition rates and their amplitudes, the characteristic swelling time of the polymer membrane significantly differs from the swelling time in untreated (reference) samples. At the same time, there is no effect for certain frequencies/pulse amplitudes. The time interval between electromagnetic treatment and measurements was about 20 min. Thus, in our experiments the effects associated with the long-term relaxation of liquids on the electromagnetic processing are manifested. The effect of long-term relaxation could be associated with a slight change in the geometric characteristics of bubston clusters during electromagnetic treatment.

Performance improvement of Cu2ZnSn(S,Se)4 solar cells by ultraviolet ozone treatment on precursor films

The precursor status is critical in obtaining high-quality CZTSSe absorbers for direct solution coating method. Here, the ultraviolet-ozone (UV-ozone) oxidation is introduced during precursor film preparation based on DMSO/DMF solutions. It was found that exposing precursor films in ultraviolet ozone with proper duration before selenization treatment effectively reduces the organic residues stemming from solvent and/or component sources. Comparing with the untreated reference sample, the crystallization and morphology of CZTSSe layers with UV-ozone treatment are evidently improved, leading to enhanced carrier lifetime and solar cell device performance. This work provides a feasible way to solve the common problem involving organic residues during CZTSSe layer preparation via a non-hydrazine solution process.

Detection of acidic paper recovery after alkaline nanoparticle treatment by 2D NMR relaxometry.

Cellulose-based artefacts are highly prone to degradation, especially in the presence of acidic compounds, which trigger the depolymerization of cellulose chains and lead to a loss in the original mechanical resistance of the material. Calcium hydroxide nanoparticles dispersed in organic solvent have been recently proposed for the deacidification of cellulose-based artworks. In this work, changes induced on paper by a deacidification treatment, following an acidification bath, were studied by nuclear magnetic resonance (NMR) relaxometry and by the so-called NMR diffraction of water trapped in the cellulose network. The deacidification treatment modifies intrachain and interchain bonds in hydrolyzed and degraded cellulose, leading to a buffered cellulose network configuration, which is similar to that characterizing the untreated reference sample in terms of relaxation parameters. Overall, calcium hydroxide nanoparticles are demonstrated effective in hindering the degradation of cellulose induced by acids and ageing in strong environmental conditions, even from the standpoint of cellulose network arrangement. It is worth noting, too, that the unilateral NMR device used for the relaxation measurements may represent a powerful tool for the preservation of cellulose-based artworks because it allows for the monitoring of the conservation status of cellulose in a completely non-invasive manner.

Reconditioning acidic and artificially aged cellulose with alkaline nanoparticles: an NMR diffusometry study

The prominent degradation mechanism of cellulose is the acid-catalyzed hydrolysis of glycosidic bonds, which results in the decrease of the degree of polymerization (DP) and, macroscopically, in the dramatic decay of the mechanical resistance of cellulose-based materials. Alkaline nanoparticles in organic solvents have been recently proposed for the deacidification of cellulose-based artworks. Their effectiveness has been demonstrated in previous studies, by pH and DP measurements, colorimetric and thermal analyses. Herein, the changes in the cellulosic network following an acidification bath and a consequent deacidification treatment using Ca(OH)2 nanoparticles, have been investigated by NMR self-diffusion dynamics of water and related to the changes of samples’ DPs. The deacidification treatment modifies intra- and inter-chain interactions, leading to a buffered cellulose network configuration similar to that characterizing the untreated reference sample in terms of diffusive parameters and confining environment. Such results are plausibly due to a rearrangement in connectivity of the cellulosic network, even though with a different physical fingerprint with respect to the reference sample. The analysis of tortuosity of the cellulosic network in acidic and deacidified samples confirms this conclusion, further corroborating the idea that calcium hydroxide nanoparticles are an effective tool to hamper the degradation of cellulose induced by acids and aging in strong environmental conditions, even from the standpoint of cellulose network arrangement.

Application of an in vitro digestion model to study the metabolic profile changes of an herbal extract combination by UHPLC–HRMS

BackgroundSTW 5 is a fixed herbal combination containing extracts from nine medicinal plants: bitter candytuft, greater celandine, garden angelica roots, lemon balm leaves, peppermint leaves, caraway fruits, licorice roots, chamomile flowers, and milk thistle fruit. STW 5 is a clinically proven treatment for functional dyspepsia and irritable bowel syndrome. PurposeUsing a static in vitro method, we simulated oral, gastric, and small intestinal digestion and analyzed the metabolic profile changes by UHPLC–HRMS to determine the impact of oro-gastro-intestinal digestion on STW 5 constituents. Study Design and MethodsSTW 5 was incubated according to the InfoGest consensus method. Samples of each digestive phase were analyzed by UHPLC–HRMS in ESI positive and negative modes. After data processing, background subtraction, and normalization, the peak areas of detectable compounds were compared to untreated reference samples and recovery ratios were calculated to monitor the metabolic profile of STW 5 during simulated digestion. ResultsAlthough the levels of some constituents were reduced, we did not observe complete degradation of any of the constituents of STW 5 upon in vitro digestion. We did not detect any new metabolites beyond increased levels of caffeic acid and liquiritigenin due to degradation of progenitor compounds. Changes observed in intestinal bioaccessibility ratios were mainly a result of isomerization, hydrolysis, protein binding, and low water solubility. ConclusionThe majority of STW 5 constituents are stable towards simulated in vitro digestion and can reach the colon to interact with gut microbiota if they remain unabsorbed in the upper intestinal tract.

Selective surface treatment by means of IR-laser – A new approach to enhance the rate capability of cathodes for Li-ion batteries

To meet today’s demands on lithium-ion batteries for battery electrical vehicles in terms of energy density, electrodes with a high active mass loading as well as a low porosity are strived for. However, such high energy electrodes exhibit a poor rate capability, mainly due to limited lithium-ion diffusion. In this work, we present a laser-based surface treatment of calendered cathodes to partially overcome this conflict of objectives. NCM-based electrodes with different porosities were superficially modified by using IR-laser radiation with pulse duration in the nanosecond-regime. By detailed microscopic analysis, we show that it is possible to selectively ablate the binder/additive-compound without impairing the active material particles. Thus, it is possible to open surface pores which were closed during calendering by the binder/additive-compound. As a result, laser treated highly densified cathodes show a significantly improved rate capability at C-rates > 2C compared to untreated reference samples. The most significant improvement of >20% of the rate capability is found at 5C for electrodes with lowest porosity of 20%. The experimental findings suggest that an enhanced electrolyte access to the active mass and thus, a reduced lithium-ion transport resistance lead to the improved electrochemical characteristics. In addition to the short-term rate capability tests, preliminary investigations of the cyclic stability of electrodes modified in such a way were performed. The state-of-health after one hundred 1C charge/discharge-cycles was about 95% for both, the laser treated and the pristine electrodes.

Thermal Stability of Defect‐Enhanced Ge on Si Quantum Dot Luminescence upon Millisecond Flash Lamp Annealing

The intentional merging of epitaxial Ge on Si(001) quantum dots with optically active defect sites promises low‐cost applications such as room temperature (RT) light emitters in Si photonics. Despite recent progress in this field, important benchmarks, for example, the thermal stability of such a combination of low‐dimensional nanosystems, as well as the curing of parasitic charge‐carrier recombination channels, have been barely investigated thus far. Herein, the structural robustness of defect‐enhanced quantum dots (DEQDs) is examined under millisecond flash lamp annealing (FLA), carried out at sample temperatures up to 800 °C. Changes in the optical DEQD properties are investigated using photoluminescence spectroscopy performed in a sample temperature range from 10 to 300 K. It is demonstrated that FLA—in contrast to in situ thermal annealing—leads to only negligible modifications of the electronic band alignment. Moreover, upon proper conditions of FLA, the RT emission intensity of DEQDs is improved by almost 50% with respect to untreated reference samples.

Improved Electron Injection and Transport in Semiconducting Polymers By Doping with Guanidino-Functionalized Aromatic Compounds

Efficient and stable n-dopants are still rare but highly desired for organic electronics and thermoelectrics. Many high mobility, n-type semiconducting polymers still show some hole transport, which is unwanted for applications in complementary inverters, as it gives rise to increased power dissipation. The use of n-type contact dopants that block the injection of holes is thus beneficial. We successfully applied 1,2,4,5-tetrakis(tetramethylguanidino)benzene (ttmgb), a guanidino-functionalized aromatic (GFA) compound, as a strong two-electron donor to networks of single-walled carbon nanotube field-effect transistors to create purely n-type devices with high electron mobilities and high on/off current ratios [1]. Here, we demonstrate the versatility of this dopant by applying it to the well-known n-type (but still slightly ambipolar) polymer semiconductor P(NDI2OD-T2).The dopant ttmgb can be processed directly from solution, which leads to significantly improved device characteristics. Additionally, we show that vapor deposition of ttmgb is another pathway to high-performance injection layers. In all cases, the injection of electrons and their mobility is significantly improved compared to the untreated reference samples. In addition, the injection of holes is blocked by ttmgb2+ on the electrode surface, which enables the fabrication of solely n-type FETs. Contact doping with ttmgb and other GFAs could potentially also be used on other semiconducting materials, e.g. for two-dimensional transition metal dichalcogenides, and may find widespread application in high performance thin film electronics. [1] Schneider et al., ACS Nano 2018, 12 (6), 5895-5902 Figure 1

Characterization of alkali-extracted wood by FTIR-ATR spectroscopy

Attenuated total reflectance (ATR) infrared (IR) spectroscopy analyses were performed with silver/white birch (Betula pendula/B. pubescens) and Scots pine (Pinus sylvestris) chips pretreated under alkaline (from 1 to 8% NaOH charge on wood dry solids) conditions to determine the suitability of this method in quickly determining chemical changes caused by varying treatment conditions on wood chemical structure. In addition to the alkali charge, pretreatment conditions varied with respect to temperature (130 and 150 °C) and treatment time (from 30 to 120 min). The spectral data of pretreated wood samples were compared to those of untreated reference samples, and the effects of the pretreatments conducted were determined based on these data. Results indicated that the most essential phenomena taking place during alkaline pretreatments could be detected by applying this simple and rapid spectral method requiring only a small sample amount. Such information included, for example, the cleavage of common lignin and carbohydrate bonds together with the significant removal of organics, especially hemicelluloses during pretreatments.

UV Radiation Induced Cross-Linking of Whey Protein Isolate-Based Films

Casted whey protein films exposed to ultraviolet irradiation were analyzed for their cross-linking properties and mechanical and barrier performance. Expected mechanical and barrier improvements are discussed with regard to quantification of the cross-linking in the UV-treated whey protein films. Swelling tests were used to determine the degree of swelling, degree of cross-linking, and cross-linking density. When the UV radiation dosage was raised, a significant increase of the tensile strength as well as an increase in Young’s modulus was observed. No significant changes in water vapor and oxygen barrier properties between the UV-treated films and an untreated reference sample could be observed. The cross-linking density and the degree of cross-linking significantly increased due to UV radiation. Combined results indicate a disordered protein network in cast films showing locally free volume and therefore only minor mechanical and barrier improvements.

Effectiveness of External Electric Field Treatment of Conjugated Polymers in Bulk-Heterojunction Solar Cells.

External electric field treatment (EFT) on P3HT:PCBM bulk heterojunction (BHJ) devices was recently found to be a viable approach for improving the power conversion efficiencies (PCEs) through modulating the blend nanomorphology. However, its effectiveness over the broad family of polymer-fullerene blends remains unclear. Herein, we investigate the effects of external EFT on various polymer-fullerene blends with distinct morphologies stemming from the difference in molecular structure of the polymers (i.e., semicrystalline vs amorphous) in a bid to establish a clear morphology-function-charge dynamics relationship to the photovoltaic performance. Our findings reveal that EFT promotes self-organization of the semicrystalline thiophene-based conjugated polymers (i.e., P3HT and P3BT) while it was ineffective for the amorphous polymers (i.e., PTB7 and PCPDTBT) even at the maximum applied E-field of 8 kV cm-1. Transient absorption spectroscopy shows an improvement in the initial charge-carrier and polaron formation from delocalized excitons in the E-field treated semicrystalline blends compared to their untreated reference samples. Interfacial trap-assisted monomolecular and trap-free bimolecular recombination at nanosecond-microsecond time scale in the E-field treated P3BT:PC60BM devices are significantly suppressed. Importantly, our findings shed new light and provide guidelines on the effectiveness of utilizing external EFT to enhance the PCEs of a larger family of conjugated polymer-based BHJ OSCs.

AN EVALUATION OF SELECTED RETOUCHING MEDIA FOR ACRYLIC EMULSION PAINT

In this study, polar and non-polar retouching media were analyzed to assess their applicability and reversibility on acrylic emulsion paint films (Golden and Schmincke acrylic paints). Acrylic emulsion paints are very sensitive to a variety of solvents. Only water, short-chain alcohols and aliphatic hydrocarbons are considered suitable for their treatment. Therefore, the retouching media used in this study were chosen for their solubility in each of these solvents. Distilled water and ethanol were used in order to test the reversibility of the polar retouching. Noctane, n-hexane and diethyl ether, which offer weak dispersive interactions but different vapor pressures, were employed for swab removal of the non-polar retouching. Extraction tests with different polar and non-polar solvents, showed which components were leached out of the acrylic paint film sample during swab removal of retouching media. Gloss measurements and photomicrographs taken of the paint film samples before and after the application of the retouching displayed variations when compared to untreated reference samples. Both measurements were taken again after reversibility tests in order to demonstrate any changes in morphology and gloss of the paint film samples.

Stability of ethyl glucuronide in hair reference materials after accelerated aging

Two different hair reference materials, one produced from authentic hair displaying an ethyl glucuronide (EtG) content of about 25pg/mg and one obtained by fortification of blank hair to an EtG level of 85pg/mg were submitted to accelerated aging between 4°C and 60°C for periods between one and 24 months. Subsequently, the EtG content was determined in the aged samples and untreated reference samples stored at −22°C under repeatability conditions following the so-called isochronous approach. The EtG content remained stable even at 40°C for 24 months and at 60°C over six months. This is in contrast to many organic analytes contained in trace concentrations in diverse matrices. A slight but significant increase of the recovered EtG in case of authentic hair samples having been exposed for 24 months between 4°C and 60°C may be due to a temperature-driven process that allows increased recoveries of the physiologically embedded EtG.

Sulfide Stress Cracking and Electrochemical Corrosion of Precipitation Hardening Steel After Plasma Oxy-Nitriding

In this paper, we present the results of a duplex plasma nitriding followed by an oxidizing stage process (which is also referred as oxy-nitriding) on the corrosion behavior of a 17-4PH precipitation hardening stainless steel. The formation of both, expanded martensite (b.c.t. α′N-phase) and chromium oxide (type Cr2O3) in the subsurface of oxy-nitrided samples at specific controlled conditions, leads in a noticeable increasing in the time-to-rupture during the sulfide stress cracking test, in comparison with an untreated reference sample. Oxy-nitriding improves the corrosion performance of the alloy when it is immersed in solutions saturated by sour gas, which extends the application potential of this type of steel in the oil and gas extraction and processing industry. The presence of the oxy-nitrided layer inhibits the corrosion process that occurs in the near-surface region, where hydrogen is liberated after the formation of iron sulfides, which finally produces a fragile fracture by micro-crack propagation; the obtained results suggest that oxy-nitriding slows this process, thus delaying the rupture of the specimen. Moreover, oxy-nitriding produces a hard, sour gas-resistant surface, but do not significantly affect the original chloride ion solution resistance of the material.

Investigation of Low-molecular Weight Phenol Formaldehyde Distribution in Tracheid Cell Walls of Chinese Fir Wood

Treatment with water-soluble low-molecular weight phenol-formaldehyde resin is an effective method to improve wood properties. In this paper, plantation wood of Chinese fir was modified with low-molecular weight phenol-formaldehyde resin. The absorbance by tracheid cell walls of phenol-formaldehyde resin in treated and untreated reference samples were measured with an ultraviolet micro-spectrophotometer. The UV absorbance values of earlywood tracheids and middle lamella in treated wood were significantly increased, with an average increase of 49% and 23%, respectively. Moreover, after treatment with low-molecular weight phenol-formaldehyde resin, the UV absorbance of the earlywood tracheid cell walls of Chinese fir increased to more than 47%, regardless of whether or not the cell lumens were filled with resin. After treatment with low-molecular weight phenol-formaldehyde resin, the UV absorbance of earlywood tracheid cell walls at different locations did not vary greatly. This study provides direct support for the improvement of the physical and mechanical properties of resin-modified Chinese fir in terms of penetration of the resin into the cell walls.

Sensory Effects of Hexanal Vapor on Fresh‐Cut Slices of Golden Delicious Apples

Hexanal is a natural antimicrobial molecule that characterizes apples aroma. In this paper, the sensory effects of hexanal, as a component of packaging atmosphere, on fresh sliced Golden Delicious apples after storage at 4 °C for 8 d were evaluated. In particular, a colorimetric analysis of slices treated with different concentrations of hexanal vapor (coming from 3.040 to 0.076 mmol of liquid aldehyde per liter of air) fixed at 0.076 mmol/L the amount of hexanal in evaluating sensory effects in the subsequent analysis. Color and texture evaluation of slices by Two-out-of-Five method did not highlight any significant difference between treatment and control. The results from olfactory evaluation showed instead that treated samples had an intense odor compared with those untreated (P < 0.001). A significant difference between treatment and control was also highlighted during the flavor evaluation (P < 0.01); however, from the panelists' observations it emerged that such an effect would work negatively. The positive effect of the tested dose of hexanal on the odor of Golden Delicious slices and its flavor acceptability were verified by using regular apple consumers. A significant preference (P < 0.001) for the odor of treated apple slices came out, so the small dose of hexanal intensifies the odor of apples pleasantly. The different flavor of treated samples was not identified by the consumers, who altogether expressed positive judgments about it. This suggests the nicety of this difference that in the absence of an untreated reference sample is very difficult to detect.