Amorphous Part Research Articles

Porosity of Calcium Silicate Hydrates Synthesized from Natural Rocks.

In this work, the suitability of natural raw materials with various modifications of SiO2—granite sawing waste (quartz) and opoka (a mixture of cristobalite, tridymite, quartz, and an amorphous part)—for the 1.13 nm tobermorite and xonotlite synthesis is examined, and their specific surface area, pore diameter and volume, and the predominant pores are determined. Hydrothermal syntheses were carried out at 200 °C for 12 and 72 h from mixtures with a molar ratio of CaO/SiO2 = 1.0. X-ray diffraction analysis, simultaneous thermal analysis, and scanning electronic microscopy were used, which showed that in the lime–calcined opoka mixture the formation of crystalline calcium silicate hydrates takes place much faster than in the lime–granite sawing waste mixture. The high reactivity of amorphous SiO2 results in the rapid formation of 1.13 nm tobermorite and xonotlite (12 h). According to Brunauer, Emmet and Taller (BET) analysis data, this product features a specific surface area of ~68 m2/g, a total pore volume of 245 × 10−3 cm3/g, and has dominating 1–2.5 nm and 5–20 nm diameter pores. This porosity of the material should provide good thermal insulation properties of the products made from it as no air convection occurs in the fine pores.

Titanium doped MoSe2 coatings – Synthesis, structure, mechanical and tribological properties investigation

In this work, we doped sputtered MoSe2 coatings with Ti to improve their mechanical and tribological properties. Mo-Se-Ti coatings were prepared onto steel discs by High Target Utilisation Sputtering (HiTUS). The Ti was in the range 7–31 at.%, which led to Se/Mo ratios of 1.7–2.7. The Mo-Se-Ti coatings possessed a polycrystalline structure for the lower Ti contents and became amorphous when Ti content was above approx. 18 at.%. The hardness of the initially soft (0.3 GPa) pure MoSe2 coatings was dramatically improved with Ti additions (up to 7.5 GPa). Sliding experiments confirmed excellent tribological properties: coefficient of friction values from 0.02 to 0.08 and very low wear rates (8×10-8mm3N-1m−1) of the Ti-containing coatings tested in the humid air at the loads in the range of 2–45 N. The outstanding self-lubricant properties of Mo-Se-Ti coatings were attributed to the transformation of the topmost amorphous part of the coating into crystalline MoSe2 tribofilm while preserving inner parts of the coating in as-deposited state ensuring good load-bearing capacity. There is strong experimental evidence that Ti has a gettering effect in the tribological contact, which protects MoSe2 tribofilm against oxidation.

Effect of Phosphorus on Crystallization of Alkaline Molybdenum-Containing Borosilicate Glasses

The effect of additives of P2O5 on the solubility of molybdenum in the amorphous part of glass and on the phase composition of the crystallized part of the highly alkaline glasses of the Li2O–(Na2O–K2O)–B2O3-SiO2 system was studied. The comparison of the phase composition of samples with or without phosphorus prior and after annealing allowed to determine the change of solubility of molybdenum in the amorphous part of the samples and to evaluate the thermal stability of the synthesized glass-ceramic materials. It was found, that for the compositions without phosphorus and the samples without lithium, when molybdenum is added at the synthesis stage, almost all of the molybdenum is included only in the crystalline molybdates. The study has shown an increase in the solubility of molybdenum only in the structure of lithium-containing glasses with phosphorus.

Additive Manufacturing of Bulk Metallic Glasses—Process, Challenges and Properties: A Review

Bulk Metallic Glasses (BMG) are metallic alloys that have the ability to solidify in an amorphous state. BMGs show enhanced properties, for instance, high hardness, strength, and excellent corrosion and wear resistance. BMGs produced by conventional methods are limited in size due to the high cooling rates required to avoid crystallization and the associated detrimental mechanical properties. Additive manufacturing (AM) techniques are a potential solution to this problem as the interaction between the heat source, e.g., laser, and the feedstock, e.g., powder, is short and confined to a small volume. However, producing amorphous parts with AM techniques with mechanical properties comparable to as-cast samples remains a challenge for most BMGs, and a complete understanding of the crystallization mechanisms is missing. This review paper tries to cover recent progress in this field and develop a thorough understanding of the correlation between different aspects of the topic. The following subjects are addressed: (i) AM techniques used for the fabrication of BMGs, (ii) particular BMGs used in AM, (iii) specific challenges in AM of BMGs such as the control of defects and crystallization, (iv) process optimization of mechanical properties, and (v) future trends.

Preparation and Characterization of Nanocrystalline Cellulose from Cladophora sp. Algae

Nanomaterial is one of the recent technological advancements that attracts the attention of many scientists. Many advanced properties could emerge from the utilization of materials on this scale. Nanocrystalline cellulose (NCC) is a cellulose-based nanomaterial currently gaining attention because of its remarkable properties. NCC was prepared by removing the amorphous part of cellulose through acid hydrolysis. Cladophora is a type of algae with a fiber-like body, that could grow rapidly and widely available in the Indonesian coastal area, which is considered a nuisance and has no known high economic value. Cladophora can be used as an alternative source of cellulose because it has a high amount of cellulose. Cellulose could be extracted from Cladophora using 17.5% of NaOH at 100°C, 1 M sulfuric acid hydrolysis at 100°C, and bleaching with 5% hydrogen peroxide at 100°C. Nanocrystalline cellulose could be extracted by sulfuric acid hydrolysis at 100°C, with a concentration of 2 M, 3 M, and 5 M. The duration of the process for each concentration, varied for 5, 10, and 15 hours. X-Ray Diffraction (XRD), Particle Size Analyzer (PSA), Transmission Electron Microscopy (TEM), and Fourier Transform Infrared (FTIR) spectroscopy were used to characterize the resulting hydrolyzed product. The result showed that the increase in acid concentration and processing duration increased the crystallinity while decreased particle length and cellulose diameter. The highest crystallinity and smallest particle size were 96.36% and 189.2 nm, obtained by acid hydrolysis in 5 M sulfuric acid for 15 hours.

Justification of conditions of application of thermo modified veneer for protection of wooden products from moisture

The analysis of the process of thermal modification of wood was carried out and it was found that the treatment causes chemical changes in the structures of wood components (lignin, cellulose and hemicellulose). It is proved that in the process of thermal modification there is a decomposition of hemicelluloses and amorphous part of cellulose, reduced water absorption, and also reduces the amount of substances that are the environment for the development of fungi, which leads to increased durability. In addition lignin and psevdolihnin formed by the process of polymerization and pererozpodilynyu in cell volume and cell walls provide higher density, hardness, increase the hydrophobicity (water repelling), thereby reducing their ability to absorb moisture and swell. It has been experimentally established that in comparison with unmodified veneer, which gained 22.41 % of moisture in two weeks, veneer modified at 250 and 280 °C gained 2.5 times less moisture - on average 8.6 %. It is established that with the increase of the modification temperature to 280 °C, the water absorption decreases more than twice. The results of the research will also allow to purposefully solve further problems on the creation of new methods of thermal modification of wood and the conditions of its operation at various sites.

Research of the process of water absorption by thermally modified wood

The analysis of the process of thermal modification of wood, which was obtained by a controlled process of pyrolysis of wood heating (> 180 °C), which causes some chemical changes in the structures of cell wall components (lignin, cellulose and hemicellulose), to increase its durability. It is proved that in the process of thermal modification there is a decomposition of hemicelluloses and amorphous part of cellulose, reduction of water absorption, and also the quantity of substances which are the environment for development of fungi decreases. In addition lignin and psevdolihnin formed by the process of polymerization and redistribution in cell volume and cell walls provide higher density, hardness, increase the hydrophobicity (water repelling), thereby reducing their ability to absorb moisture and swell. Polymerised lignin fills the inside of the cell – formed closed porous structure with low ability to bind water. It was established that the most effective option to reduce such substances are temperature and exposure time. The results of water absorption, dependence on which the calculated diffusion coefficient in the water absorption. Thermal modification of wood reduces water absorption by more than 10 times within 6 hours, which allows it to be used on objects with high humidity.

Fate of phosphorus and potassium in single-pellet thermal conversion of forest residues with a focus on the char composition

The phosphorus and potassium contents of the char obtained from thermal conversion of forest residues can limit its utilization as an alternative fuel and reducing agent to substitute coal/coke in the steelmaking industry. In this study, ash transformation and release of K and P during single-pellet thermal conversion of different types of forest residues (i.e., bark, twigs, and bark+twigs) were investigated with the aid of a vertical tube furnace (Macro-TGA) at different temperatures (i.e., 600, 800, and 950 °C) and within and after different fuel conversion stages, i.e., devolatilization and char gasification. The residual char before and after full devolatilization, and ash after char gasification were characterized by SEM-EDS, XRD, and ICP-OES with the support of thermochemical equilibrium calculations. The concentrations of K (7970–19500 mg/kg) and P (1440–4925 mg/kg) in the char produced after devolatilization were more than four times higher than in coke and pulverized coal frequently used in metallurgical processes. A low amount of P and K (≤15%) were released from all fuels. K and P were evenly distributed within the char residues, and no crystalline compounds containing K and P were found. In ash residues of bark, K was found in K2Ca2(CO3)3, and K2Ca(CO3)2. K in ash residues from twigs and bark+twigs was mainly found in the amorphous part of ash, most likely in the form of K-Ca rich silicates. Apatite was found as the main P crystalline compound in all ashes at all temperatures. Estimations show that a release of more than 80% is needed for the studied forest residual assortments to reach K and P concentrations typical of blast furnace coals and cokes.

Attenuated Total Reflection-Far-Ultraviolet Spectroscopy and Quantum Chemical Calculations of the Electronic Structure of the Top Surface and Bulk of Polyethylenes with Different Crystallinities.

In this study, we explored the electronic structure of the surfaces of polyethylene samples having different crystallinities using attenuated total reflection (ATR) far-ultraviolet (FUV) spectroscopy and quantum chemical calculations. Specifically, the ATR-FUV spectra of five types of high-density polyethylene (HDPE), six types of linear low-density PE (LLDPE), and seven types of low-density PE (LDPE) were obtained. All the spectra contained an intense band near 156 nm and a broad band between 180 and 190 nm. Transmission spectra were obtained for the thin-film (30 µm) PE samples between 165 and 250 nm. In this region, the HDPE films show very low-intensity bands. In contrast, the transmission spectra of the LLDPE and LDPE samples yielded weak-to-medium and medium-intensity bands around 180-190 nm, respectively. In addition, to understand the differences in the absorption spectra among the PEs observed, we simulated the spectra of n-pentane as a PE crystal model using time-dependent density functional theory and found that the common intense band at 156 nm is due to the σ (C(2p)-H)→Rydberg 3s, 3p transition. The absorption bands near 180-190 nm may correspond to aggregates of numerous molecular chains in the amorphous parts of the LLDPE and LDPE samples.

Investigating compatibility between TPU and bitumen SARA fractions by means of Hansen solubility parameters and interfacial tension measurements

Hansen solubility parameters (HSP) and model oils were used to predict the affinity of each block of the TPU (thermoplastic polyurethanes) with the SARA fractions (Saturates, Aromatics, Resins, Asphaltenes) of bitumen, revealing the preferential compatibility of the bitumen with the soft block of the TPU. More specifically, aromatics are highly compatible with the soft block while resins are compatible with soft and hard blocks of the TPU. Companion SAXS analysis highlighted that the microstructure of TPU is however maintained with semicrystalline hard nanodomains dispersed in a soft matrix with its amorphous part being swollen by resins. Interfacial tension measured by drop deformation retraction method (DDR) highlighted the compatibilizing role of resins as a lower interfacial tension value was measured at high resin content. In turn, different mechanical properties of TPU-modified bitumens were obtained when changing their composition. With similar morphologies for the blends (i.e. continuous TPU phase swollen with the same ratio), a decrease in rubbery storage modulus and flowing temperature was observed as the amount of resins increases.

Chemical and mineralogical characteristics of carbonated and uncarbonated cement pastes subjected to high temperatures

The fire-resistance of carbonated concrete under high temperatures is significant due to its direct exposure during an accidental fire. To evaluate the carbonation effect on fire-resistance of concrete, the chemical and mineralogical changes of uncarbonated and carbonated cement pastes subjected to high temperatures were thoroughly investigated in this research by employing micro-measurement methods including thermal-gravimetric analysis (TGA), X-ray diffraction (XRD) and 29Si nuclear magnetic resonance (29Si NMR). Uncarbonated cement paste results showed the decomposition of portlandite at 400 °C with the formation of lime, whilst the depolymerization of C–S–H happened simultaneously to generate monomeric silicon tetrahedron. Above 720 °C, all the C–S–H depolymerized to crystalline C2S. Carbonated cement pastes on the other hand showed that amorphous calcium carbonate and part of vaterite decomposed between the range of 400–600 °C, while the rest of the vaterite and calcite were decomposed at 600–720 °C. The individual content of calcium carbonate polymorph could not be obtained using a TGA curve. Besides, the calcium-modified silicate gel was significantly decomposed at 500 °C and completely depolymerized to crystalline C2S at 950 °C. In summary, carbonated pastes show better resistance to high temperatures with its heat absorption capacity 3.3 times as high as the uncarbonated sample, which delays the temperature development in the inner layer. Therefore, a reasonable carbonation process could help to improve the fire resistance of concrete to some extent.

Establishing regularities in the propagation of phase transformation front during timber thermal modification

The creation of environmentally friendly protective materials for building structures made of wood could make it possible to influence the processes of stability and the physical-chemical properties at the thermal modification of hornbeam wood over a certain time. That necessitates studying the conditions for investigating phase transformations when the timber is exposed to high temperature, as well as establishing the mechanism of hornbeam wood thermal modification. Given this, a mathematical model of the phase transformation process during the transfer of heat flux to a sample was built. Based on the derived dependences, it was established that when hornbeam wood is exposed to temperature treatment, it undergoes endothermic phase transformations characterized by the heat absorption and change in the color of hornbeam wood. In particular, at a temperature of 200 °C, the temperature in the wood decreases by 5 % due to the chemical changes in the structure of cell wall components (lignin, cellulose, and hemicellulose). It was found that the process of thermal modification is accompanied by the decomposition of hemicellulose and the amorphous part of cellulose, a decrease in moisture absorption, as well as a decrease in the volume of substances that are a medium for the development of fungi. In addition, lignin and the resulting pseudo lignin undergo a process of polymerization and redistribution throughout the cell volume. At the same time, they give the cell walls higher density, hardness, increase hydrophobicity (water repellency), thereby reducing the ability to absorb moisture and swell. It was established that the most effective parameter of phase transformations is the temperature and aging duration. The results of moisture absorption have been given; it has been found that over 6 hours of modified timber exposure, its moisture absorption decreases by more than 10 times, which allows its application at facilities with high humidity

Fe and S-isotope compositions of hydrothermal deposits from Kings Triple Junction, Lau Basin, southwest Pacific Ocean

We analyzed iron and sulfur isotopic compositions of polymetallic sulfides from an extinct hydrothermal mound near the Kings Triple Junction of the northern Lau basin belonging to a back-arc basin for understanding the origin and mineral zoning processes in this study. Sulfides from the hydrothermal mound's pedestal slab consisting of chalcopyrite and pyrite show enrichment of heavy S-isotope (δ34SV-CDT = +8.3 to +9.6‰). Sphalerite-dominated chimney on the mound's slope also has variable δ34S values between +5.5 and + 8.3‰ from central orifice to outer wall. These isotopic ratios indicate the substantial contribution of heavy isotope rich sulfate-S in seawater circulating within the mound. Low Δ33S values in these sulfides also indicate that the sulfate reduction is of thermal origin, with minimal or no role for microbes. Circulating seawater induced changes in fluid composition and post-depositional zone refinement of certain minerals can explain the variation in δ34S in different layers within the chimney and pedestal slab. The Fe-isotopic compositions (δ56FeIRMM-014) show a range from −1.1 to −0.3‰ in the pedestal slab while they vary between −1.7 and − 0.6‰ at different parts of the peripheral chimney section. We explain such changes are mostly due to redox processes and mineral zoning development during these sulfide deposit formation. The tree-like FeMn oxide growth structures in the vicinity of the hydrothermal mound having a thin birnessite top layer and amorphous iron oxide bottom part show distinct δ56Fe values of −3.0 and − 0.8‰, respectively.

Synergic Effects of Surfactant and Chelating Agent on Stubborn Keratin Grime for Easy Cleaning.

We report on the synergic effect of surfactants and chelating agents on the mechanism to remove stubborn keratin grime (keratin-Ca), which is bound with calcium ions and one of the most difficult grimes to remove, in order to make it easier to clean bathtubs in less time and with less scrubbing. Our approach was to focus on keratin swelling, which we achieved by applying aqueous solutions with chelating agents and anionic surfactants, the combination of which greatly improved the swelling ratio, resulting in quick, easy removal of keratin-Ca with water rinsing and little scrubbing. For the swelling process, we added chelating agents and anionic surfactants to swell the keratin-Ca by both capturing calcium ions and improving solution permeation. Furthermore, we measured the structural change of the keratin-Ca during swelling by TD-NMR and confirmed that a certain combination of chelating agent and anionic surfactant improved swelling by affecting not only the amorphous part such as the keratin matrix, but also the crystalline part such as the intermediate filaments (IFs).

Research activation energy in thermal modification of wood

The analysis of the process of thermal modification of wood, which was modified by a controlled process of pyrolysis of wood heating (> 180 ° C) in the absence of oxygen, which causes some chemical changes in the chemical structures of cell wall components (lignin, cellulose and hemicellulose), durability. It is proved that in the process of thermal modification the decomposition of hemicelluloses and the amorphous part of cellulose occurs, and therefore the amount of substances that are the environment for the development of fungi in wood significantly decreases. In addition, lignin and the formed pseudolignin undergo a process of polymerization and redistribution of cell volume and give cell walls greater density, hardness, increase hydrophobicity (water repellency), thereby reducing their ability to absorb moisture and edema. Polymerized lignin fills the inner cavity of the cell, forming a closed porous structure with a low ability to bind water. It was found that the most effective parameter for reducing such substances is the temperature and exposure time. The results of thermogravimetric researches are given, the dependence of weight loss on temperature of researches on the basis of which activation energy is calculated is defined. The results of determining the activation energy show that for hardwood species this value exceeds more than 1.5 times compared to softwood.

Relevant Properties of Carbon Support Materials in Successful Fe-N-C Synthesis for the Oxygen Reduction Reaction: Study of Carbon Blacks and Biomass-Based Carbons.

Fe-N-C materials are promising non-precious metal catalysts for the oxygen reduction reaction in fuel cells and batteries. However, during the synthesis of these materials less active Fe-containing nanoparticles are formed in many cases which lead to a decrease in electrochemical activity and stability. In this study, we reveal the significant properties of the carbon support required for the successful incorporation of Fe-N-related active sites. The impact of two carbon blacks and two activated biomass-based carbons on the Fe-N-C synthesis is investigated and crucial support properties are identified. Carbon supports having low portions of amorphous carbon, moderate surface areas (>800 m2/g) and mesopores result in the successful incorporation of Fe and N on an atomic level and improved oxygen reduction reaction (ORR) activity. A low surface area and especially amorphous parts of the carbon promote the formation of metallic iron species covered by a graphitic layer. In contrast, highly microporous systems with amorphous carbon provoke the formation of less active iron carbides and carbon nanotubes. Overall, a phosphoric acid activated biomass is revealed as novel and sustainable carbon support for the formation of Fe-Nx sites. Overall, this study provides valuable and significant information for the future development of novel and sustainable carbon supports for Fe-N-C catalysts.

Nanoscale mechanics of thermally crystallized GST thin film by in situ x-ray diffraction

The thermal crystallization of Ge2Sb2Te5 (GST) thin film is investigated by in situ x-ray diffraction (XRD). The combination of several x-ray diffraction techniques (a) in-plane XRD, (b) out of plane XRD, (c) high resolution XRD on the substrate, and (d) 2D high energy XRD allows the characterization of the mechanical behavior of GST upon thermal crystallization. A new method is proposed for the evaluation of experimental stress vs strain dependence in thermally crystallized GST. Nanoscale strain, macroscale stress, and nucleation/crystallization are fully described by the correlation of these techniques. Upon crystallization, a progressive tensile stress build-up is observed. Concomitant stress build-up is also observed both in the in-plane and out of plane directions of the film. The 2D high energy XRD demonstrates a homogeneous nucleation process and a progressive crystallization of the GST composed partially of amorphous and crystalline parts in the film. The GST nanomechanics is then characterized at the nanoscale (crystallites scale) and at the macroscale (film scale). By plotting the stress vs strain and assuming a Poisson ratio of 0.28, the mixture of phase results in a Young modulus between 9 GPa and 37 GPa for amorphous and crystalline matrices, respectively. Intermediate states with a partial amorphous/crystalline ratio results in intermediate values of the Young modulus. Finally, cross correlation between all XRD techniques gives EGST ≈ 34 GPa and υGST ≈ 0.34 for fcc crystalline GST.

Effect of gamma radiation on the structural, thermal and optical properties of PMMA/Sn0.75Fe0.25S2 nanocomposite

Abstract Nanocomposite films of polymethylmethacrylate PMMA with Sn0.75Fe0.25S2 nanoparticles (NPs) were fabricated by both thermolysis and casting techniques. Changes in PMMA/Sn0.75Fe0.25S2 nanocomposite (NCP) due to gamma irradiation have been measured. XRD results indicate that the gamma doses of 10–80 kGy cause intermolecular crosslinking that reduces the ordered portion in the NPs. Bonding between the NPs and the host PMMA was confirmed by FTIR. TGA results indicate an enhancement in thermal stability in the NCP films irradiated with doses 20–80 kGy. The optical band gap was reduced from 3.23 to 2.47 eV upon gamma irradiation up to 80 kGy due bonding between the NPs and PMMA which enhanced the amorphous part of the NPs. Finally, the color variation between the blank and irradiated films (ΔE) was determined. Color changes immensely when the PMMA/Sn0.75Fe0.25S2 NCP films are gamma irradiated. Values of ΔE were as much as 31.6 which is an acceptable match in commercial reproduction on printing presses.

Copper-containing non-woven materials from silk waste

A rational approach to the problem of recycling natural silk processing waste is proposed. Cocooning wastes are processed into needle-punched non-woven material onto which copper nanoparticles are deposited by chemical reduction methods with ascorbic acid from alkaline solutions of copper sulfate. It was shown that, depending on the time of impregnation of the nonwoven material with an alkaline copper solution, sericin, wax and fatty substances are removed from the material, and when impregnated for more than 15 minutes, the amorphous part of fibroin. The amount of copper on the fibrous material can be varied by the conditions of impregnation and washing. The size distribution of copper nanoparticles on the finished material was studied.

Relationship between Carbon Structure-Electrical Conductivity By Cluster Analysis for Li-Ion Battery Application

Carbon materials are widely used as anode on Li-ion battery (LIB). In particular, the effect of electrical conductivity (EC) on the anode is related to capacity and retention, which are important factors for LIB performance. However, the relationship between carbon properties and battery performance is still unclear. This uncertainty is due to the sp3 and sp2 bond states, the diversity of carbon like amorphous structures, and impurities.In this study, we investigate the structure-EC relationship from over 50 carbon samples. The carbon used was graphite, carbon nanotube (CNT), carbon black (CB), hetero atom doped carbon, and the ones synthesized by solution plasma. The carbon materials are evaluated by X-ray diffraction (XRD), Raman spectroscopy, Thermogravimetric analysis (TGA), Energy-dispersive X-ray spectroscopy (EDX), and four-point probe (FPP) measurement. The characterized values were extracted from the results and analyzed by Cluster analysis (CA) with JMP software. CA was used to classify how carbons are related to each other.The clusters were divided into 3 big groups according to the presence of 002 peak and the degree of defects. Some clusters have been shown high conductivity when they have high crystallinity. It was also found that the heteroatomic effect was higher than the crystallinity in the part showing low EC range. However overall correlation with EC is still unclear. This is because XRD and Raman can only provide information of symmetric or periodic structures rather than the effect of disorder or amorphous parts, sizes and shapes are not considered. Thus, analysis of shapes and sizes such as SEM and BET, and additional measurements related to amorphous structures may be helpful to clarifying the correlation. Figure 1