Changes In Material Composition Research Articles

Physical techniques shed light on the differences in sugarcane bagasse structure subjected to steam explosion pretreatments at equivalent combined severity factors

Significant improvements in pretreatments and a deeper understanding of changes in the physical structure and chemical composition of pretreated lignocellulosic materials are required to guarantee the technical and economic sustainability of second-generation ethanol technologies. In present work, several biophysical techniques were applied to characterize sugarcane bagasse samples that have been subjected to autocatalytic, phosphoric acid and sulfuric acid catalyzed steam explosion under equivalent combined severity factors (CSF). Confocal laser scanning microscopy and fluorescence lifetime imaging studies demonstrated unequal changes in lignin distribution in the plant cell wall that could be nicely correlated with substrate susceptibility to enzymatic hydrolysis. Furthermore, solid state nuclear magnetic resonance corroborated these observations by showing the differences in biomass composition primarily associated with hemicellulose removal, whereas X-ray diffraction analysis revealed changes in crystallinity indexes and average crystallite sizes. Thus, the impact of pretreatment temperature on the physical structure and chemical composition of CSF-equivalent steam-exploded sugarcane bagasse was identified as the key factor for developing substrate accessibility. This calls for caution in using combined severity factor as a chief parameter for comparison of different pretreatment conditions.

Influencing factors and evaluation system for Carbon–Calcium pellet performance in a pyrolysis furnace

In the new process of CaC2 production, C–Ca pellets need to be pyrolysed in a prepyrolysis furnace before being placed in a CaC2 furnace. In this paper, the factors influencing the performance of composite pellets in a pyrolysis furnace are studied experimentally. A comprehensive performance-evaluation system is established to calculate and evaluate composite pellets comprising five raw materials. The pyrolytic rate, compressive strength, and dust concentration of the composite pellets are tested through thermogravimetry, universal pressure tester and dust concentration detector, respectively. The effects of C/Ca ratio, temperature, time and raw material composition on these properties are explored. Results show that during the pyrolysis of the composite pellets, the C-containing raw materials have a significant effect on various performance indicators. With increased C/Ca ratio, the pellet pyrolysis rate and compressive strength show a downward trend; with increased pyrolysis temperature and time, the pellet pyrolysis rate, compressive strength and activity show an upward trend; with a change in raw material composition, the pellet activity and dust concentration change significantly. The comprehensive properties of CaO + coke and CaO + anthracite are superior to those of other raw materials in all aspects, and this finding is in line with the industrial-production practice.

Study on geotechnical engineering investigation method of strong karst deep backfill area in mountain area

Guizhou Province is characterized as mountainous with few flat lands. It also features undulating terrains; widespread karst strata; large karst troughs; karst depressions and falling water caves; and well-developed underground karst caves, karst pipelines, and underground rivers. In such mountainous areas, large-scale construction of karst sites requires large-scale excavation and backfilling. The study site comprises several backfilled layers of 550 m thickness and features complex components and large thickness variations. The influence of the long-term seepage of surface water and groundwater is also apparent. However, the study site also exhibits an uneven settlement of deep backfilled layers and unstable karst foundation. The conventional survey method cannot identify effectively and comprehensively existing problems in engineering geology and hydrogeology according to the problems found in the investigation of large-scale building areas, municipal roads, urban rail transit, and university campuses. Through the combination of building engineering methods, such as new and old topographic and geomorphologic contrast methods, on-site geological surveys, karst hydrogeological surveys, borehole layout principle, drilling method, effective physical exploration test, field in-situ test, and indoor test, the scale and characteristics of karst development in the study site, changes in backfill thickness and material composition, and physical and mechanical properties of rock and soil mass are determined. The results provide comprehensive geotechnical data for the type selection, arrangement, and foundation scheme selection of structures. Through comprehensive analysis and summary, this work establishes a set of comprehensive geotechnical investigation methods for strong backfilled karst areas in mountainous regions. The results are expected to be applicable to other similar sites.

Specific Features of Thermal Performance of the Arc Steel Furnace in Unstable Properties Conditions of Burden Materials

In the production of steel in a state-of-the art arc furnace, there are two serious issues, resulting from a decrease in bulk density of burden materials, and an increase in non-ferrous metals concentration. The paper presents the analysis results of changes in the chemical composition of iron-containing materials related with an increase in the content of non-ferrous metals: copper, tin, lead, antimony and unspecified metals in a given steel grade and a decrease in the bulk density of burden materials. A method of reducing impurities by means of using pellets produced from natural raw materials, that are pure in terms of impurities, is presented. A method of setting up charging of burden materials with different bulk density, using the filling coefficient of the furnace operating volume, is proposed. Combined burden materials that include various types of scrap and non-ferrous metals of iron-ore pellets, that are pure in terms of impurities, will ensure high-quality steel production.

Iso-material contour representation for process planning of heterogeneous object model

Abstract Additive manufacturing is emerging as the preferred process for making heterogeneous objects. Planning the deposition of material is more complex for heterogeneous objects as the material variation has to be tracked along the path. This paper proposes an iso-material contour representation to generate the process plan for additive manufacturing given a smooth representation of heterogeneous object model. These contours represent the iso-material paths for deposition. As these paths shift along the direction of the gradation of material distribution, the deposition respects the gradient of the designed material distribution unlike iso-oriented paths generated by a raster scan method. Since the paths have the same material composition, material frequent change in the material composition is avoided, which, in turn, avoids the uneven deposition caused by the frequent start and stop of deposition while the material is being changed along the paths generated by the traditional raster scan. Associativity between the contours and the corresponding designed material feature is maintained, and therefore, changes in material composition are automatically propagated to the process plan.

Highly dense cellulose acetate specimens with superior mechanical properties produced by fused filament fabrication

The extrusion based Fused Filament Fabrication (FFF) enables to build up components of thermoplastic materials by using a layer-by-layer strategy. Typically, the layered structure results in an internal porosity limiting the mechanical performance. In this work, using a commercial 3D-printer specimens of the polymer cellulose acetate (CA) were produced having porosities as low as 1–3 %. Quasi-static tensile tests demonstrate that these highly dense specimens reach similar or even higher strength values in comparison to their injection molded counterparts. The influence of the temperature management was studied by using different hot-ends, namely a standard one and a novel hot-end having a modified heat-block. Using the latter one, a homogeneous internal structure was achieved as observed with scanning electron microscopy (SEM). The very low porosities can be assigned to the elevated specimen temperature maintained during printing which is slightly above the materials glass transition temperature. Processing of CA at such temperatures leads to a slight loss of plasticizer as proved with NMR spectroscopy. This favorable change in material composition during printing additionally contributes to the mechanical strength of the test specimens. We conclude that the porosity is the key parameter (which has to be measured and minimized) to realize FFF components with good mechanical performance. Whereas we demonstrated FFF for the first time for CA as an industrially relevant thermoplastic material, our results can be easily applied to amorphous polymers in general.

Progress in low energy high intensity ion implantation method development

New results on the equipment development and advancement of the method of high-intensity ion implantation of metal, gases and low-energy semiconductors providing a long range effect of dopants penetration are presented in the article. The results of the research and development of plasma-immersion systems for the formation of ion beams with a current density of tens and hundreds of mA/cm2, a beam current exceeding 1 A at kilovolt accelerating voltages using ion extraction and beam focusing systems as part of a sphere or cylinder are shown. A comparative analysis of various systems, their advantages and disadvantages depending on the purpose are presented.The concept of low energy high intensity ion implantation (LEHI3) method is described. The features of the method as applied to the problems of deep modification of the microstructure and operational characteristics of metals and alloys are analyzed. The report presents the results of experimental studies of LEHI3 of aluminum, titanium, nitrogen into various structural materials. The possibility of ion doping of materials at depths of several tens and hundreds of micrometers is shown. Data are presented on the changes in the elemental composition, microstructure and properties of various materials depending on the ion current density of 10–500 mA/cm2, ion energy, implantation temperature and irradiation fluence of 1018–1022 ion/cm2.Based on the analysis of the obtained experimental data, the directions of further research are discussed in the framework of the development of the physical and technological foundations of the LEHI3 method of material properties modification at depths that are orders of magnitude greater than the projective ranges of ions.

Critical Assesment 37: Harmonic-structure materials - idea, status and perspectives

ABSTRACTRecent efforts in engineering metals with high structural efficiency have resulted in developing a new category of artificial materials with heterogeneous microstructures architected across multiple scales. In this critical assessment, a relatively new concept of heterogeneous bimodal harmonic-structure (bHS) materials is introduced and analysed. It is shown that the bHS concept is applicable to a large variety of metallic materials and is most efficient in scenarios where changes in the chemical composition of materials are restricted for some reason. Basic principles, weaknesses and advantages along with present development status and perspectives are discussed. The overview of critical performance characteristics of various bHS materials is provided, and interesting directions for future research, development and applications are proposed.

Rheology of starch dispersions at high temperatures.

In the food industry, many food products experience extreme processing conditions of high temperature and high shear stresses. The measurements of sample behavior for water-based formulations above 100°C is extremely challenging due to changes in material composition from the boiling of volatile ingredients. We have developed a high-sensitivity, pressurized starch pasting cell (up to 5 bar) which utilizes a design free of mechanical bearings and seals, resulting in an order-of-magnitude improvement in torque sensitivity (1 μN.m in oscillatory and 10 μN.m in shear flows) compared to traditional pressure cells. A pressurized atmosphere in the cell suppresses boiling of the volatile components, allowing the characterization of the structure-property relationships of the sample over a range of testing conditions (-5 to 150°C) which simulate industrial processing and storage conditions. This cell is employed to investigate the pasting properties of a commercial starch dispersed in water. In situ gelatinization of starch dispersions of varying starch particle weight fractions (ϕ) subjected to a high temperature (120°C) at elevated pressure and at a fixed shear rate is studied. A phase transition, from an initial flowable starch slurry to a paste, takes place during which the viscosity evolves by several orders of magnitude. Typical parameters associated with the viscosity evolution during gelatinization such as onset temperature, peak temperature, and peak viscosity are analyzed to probe the impact of high temperature on the gelation process and the rheological properties of the final starch paste. Furthermore, yield stresses of the final paste, measured at 120°C, are examined for varying ϕ through traditional rheological methods such as flow ramps, oscillatory shear, and stress growth, demonstrating the capabilities of this cell for studies of steady shear and nonlinear viscoelastic behavior of the starch pastes. The yield stress values are found to be in good agreement when comparing various testing methods. Yield stresses range from 0.25 to 6.5 Pa for ϕ between 0.05 and 0.15, with 0.05 being the minimum starch weight fraction for which there is any measurable yield stress. The yield stress and the paste viscosity both scale with starch particle weight fraction as (ϕ - ϕc ) m , where ϕc = 0.04 as no yield stress is observed for ϕ ≤ 0.04. The exponent, m, for yield stress is found to be in the range of 1.15-1.4 depending on the analytical method used and the definition of yield stress while for peak and breakdown viscosities it is noted to be 1.6 and 1.1, respectively. The Herschel-Bulkley model is found to fit the flow curves well. The starch pastes are found to exhibit shear-thinning and significant thixotropic behavior.

Numerical Simulation Study on Bolted Joints of Steel-wood Structures

As one of the most widely used rigid connections, bolted joints have the advantages of convenient loading and unloading, increased prestressing to prevent loosening, and no change in material composition at the joints. In this paper, six sets of test pieces are designed, and the monotonic loading is performed. The bearing capacity of the joints under the two parameters of bolt margin and wood characteristics is analyzed, and compared with the theoretical value, the reliability of the finite element simulation results is increased.

Effect of material composition on noise performance of sub-micron high electron mobility transistor

Noise figure, reflection coefficient and normalized resistance for AlxGa1−xN/GaN based sub-micron high electron mobility transistor is analytically investigated as a function of material composition from small-signal equivalent circuit over the period of C-band to X-band. A few other significant parameters like phase of both reflection coefficient and optimum impedance, average gain are studied; and critical variations are found for optimum impedance phase profile which gives maximum magnitude at a particular frequency for different material systems. Variations of noise figure and other relevance parameters are explored for an assortment of external biasing conditions and threshold parameter, and results suggests very close agreements with experimental data and also with Pospieszalski model. Phase of optimum impedance depicts peak at a particular frequency within the choice of range, and it shifts with change of material composition. Simulated results are significant in designing HEMT based RF oscillator circuits with proper amalgamation of material composition, drain and gate voltages, leakage current and threshold voltage.

Evaluation of the content and bioaccessibility of magnesium, manganese, zinc and copper from buckwheat groats produced in various conditions

AbstractIn recent years special attention has been paid to gluten-free foods, and among them buckwheat grains are becoming more popular. They are a rich source of many nutrients, including mineral compounds, and are eaten in many forms, eg. as a “kasha” which is obtained from roasted and dehulled grains. Food processing causes various changes in chemical composition of raw materials and their rate depends on the treatment parameters, therefore the aim of the study was to determine how the content and bioavailability of selected minerals is influenced by conduction the buckwheat groats production under different conditions.The experimental materials were buckwheat grains subjected in industrial conditions to a short hydrothermal treatment (ca. 100°C/15 min) conducted in cereal dryer (unroasted groats were obtained), and also roasted in pressure boilers (140°C/90 min, 0.4 MPa) to receive roasted grains. The content of selected minerals (Mg, Mn, Zn, Cu) was determined by flame atomic absorption spectrometry and their bioavailability was determined by enzymatic hydrolysis in vitro in a system, which simulated the conditions in the human gastrointestinal tract.It was shown that different conditions of applied hydrothermal treatment had a lesser influence on the total content of analyzed minerals (determined before the digestion process), but they significantly influenced their bioaccessibility. Short treatment carried out at a lower temperature had a beneficial effect on the availability of all determined elements, increasing it to the greatest extent for Mg and Mn.This process caused an increase in the content of Mg released after digestion from 859.4 μg/g (unheated grains) to 1233.8 μg/g (unroasted groats), and the Mn level increased respectively from 2.61 to 5.19 μg/g. The roasting process statistically significantly (p < 0.001) reduced the level of these elements (to 836.1 μg/g for Mg and 1.99 μg/g for Mn). The high parameters of seed treatment used during roasting also caused a decrease in the availability of other elements and their effect was most noticeable for Zn, whose level decreased from 31.99 μg/g (unheated grains) to 9.97 μg/g (roasted groats).Observed dependencies allow to state, that due to the bioaccessibility of minerals, it is more beneficial to treat buckwheat grains with a lower temperature in a short time, and therefore consumers who pay attention to the nutritional value of the food, should choose unroasted buckwheat groats.

Pulsed electric discharge for environmentally friendly cleaning and crushing of quartz sand

The paper presents the results of research on the use of a pulsed electric discharge in aqueous media for the pretreatment (preliminary crushing and washing) of quartz sand in the glass industry. The averaged granulometric and elemental composition of quartz sands of the Muraevnya deposit has been studied (explored reserves are 31 million tons). The efficiency of the proposed method for treating quartz sand for its subsequent cleaning from undesirable impurities (primarily iron and clay oxides) is shown, preliminary parameters of the treatment process, changes in the granulometric and elemental composition of raw materials, and specific energy consumption for its treatment are determined. The main advantage of the technology is that it makes it possible to obtain such a degree of purification of quartz sand from impurities due to the destruction of impurities aggregated with silicon oxide particles, which is unattainable with standard flushing.

Calcined Post-Production Waste as Materials Suitable for the Hydrothermal Synthesis of Zeolites.

The zeolite production process is currently being very intensively researched. Due to environmental protection, as well as issues related to the guidelines of a zero-waste economy, all activities aimed at obtaining such materials from post-processed waste are extremely important. This article presents an innovative method of utilising calcined carboniferous shale in order to produce synthetic zeolites. The raw material for testing came from two Polish hard coal mines. Both the chemical and phase composition of the coal shale were characterised. Based on the recorded thermal analysis results coupled with the mass spectrometer, the processes occurring during the heating of raw materials were interpreted and the calcination temperatures were determined. The changes in the phase composition of raw materials resulting from the calcination process used were also analysed. The heat-treated raw materials were subjected to the synthesis of zeolites in an aqueous solution of sodium hydroxide by means of the hydrothermal method at a concentration of 2.75 M. The results of water leaching and structural parameters are presented for both raw materials, as well as the produced synthesis. The conducted research confirmed that after the application of the synthetic process on coal shale, a zeolite with a surface area of SBET equal to 172 m2/g can be obtained.

Provenance, modification and use of manganese-rich rocks at Le Moustier (Dordogne, France).

The use of colouring materials by Neanderthals has attracted a great deal of attention in recent years. Here we present a taphonomic, technological, chemical-mineralogical and functional analysis of fifty-four manganese rich lumps recovered during past and on-going excavations at the lower rockshelter of Le Moustier (Dordogne, France). We compare compositional data for archaeological specimens with the same information for twelve potential geological sources. Morphometric analysis shows that material from Peyrony’s excavations before the First World War provides a highly biased picture of the importance of these materials for Mousterian groups. These early excavations almost exclusively recovered large modified pieces, while Mn-rich lumps from the on-going excavations predominantly consist of small pieces, only half of which bear traces of modification. We estimate that at least 168 pieces were not recovered during early work at the site. Neanderthals developed a dedicated technology for processing Mn-rich fragments, which involved a variety of tools and motions. Processing techniques were adapted to the size and density of the raw material, and evidence exists for the successive or alternating use of different techniques. Morphological, textural and chemical differences between geological and archaeological samples suggest that Neanderthals did not collect Mn-rich lumps at the outcrops we sampled. The association and variability in Mn, Ni, As, Ba content, compared to that observed at the sampled outcrops, suggests that either the Le Moustier lumps come from a unique source with a broad variation in composition, associating Mn, Ni, As, Ba, or that they were collected at different sources, characterized either by Mn-Ni-As or Mn-Ba. In the latter case, changes in raw material composition across the stratigraphy support the idea that Neanderthal populations bearing different stone tool technologies collected Mn fragments from different outcrops. Our results favour a use of these materials for multiple utilitarian and symbolic purposes.

Chemical changes during composting of plant residues reduce their mineralisation in soil and cancel the priming effect

Applying composts is useful for increasing soil carbon (C) stocks and improving agricultural productivity. In order to understand the effects of composts on soil organic matter (SOM) formation and mineralisation, 13C-labelled plant residues, previously composted or not, were incubated in an arable soil. The amount of 13C was quantified in the CO2 evolved, the dissolved organic carbon (DOC) and in the microbial biomass (MB). Composting decreased (from 29 to 9%) the proportion of the plant residue labile pool and increased the residence time of both labile and more stable pools from 21 to 34 days and 1.5–5.5 years, respectively. At the beginning of the incubation, the amounts of 13C in the DOC and MB were significantly higher when adding fresh residues than composted ones to the soil. A priming effect on SOM mineralisation (+21% over 3 years) was only observed for non-composted residues. These differences were attributed to changes in the chemical composition of plant materials during composting (less sugars and lipids, more lignins). In terms of C budget, the total loss of CO2 (including the composting process and the SOM priming by fresh residues) was comparable for both treatments after 600 days of incubation.

Drastic Changes in Material Composition and Electrical Properties of Gallium-Seeded Germanium Nanowires

Varying the growth conditions of gallium-seeded germanium nanostructures leads to significant variations in morphology, and particularly of the electronic properties inducing a transition from the ...

The influence on different incorporation elements concentration of (Ga2O3)x(Co)0.6-x (ZnS/Se)0.4 (x = 0.1, 0.3 and 0.5) chalcogenide thin films

The (Ga2O3)x(Co)0.6-x(ZnS/Se)0.4 thin film was fabricated by the PLD of different pressure and substrate temperature. The ability to control the growth of nano-scale films is proved by the results of thickness. The antireflection coating materials in the infrared spectral region are affirmed by the results of refractivity. The change of material composition having an important effect on the preparation process is depicted by the plasma plume. Stable amorphous structure is confirmed by XRD under the different preparation conditions. The change of material composition has an important impact on the bonding and microstructure of the material, which is confirmed by Raman spectra. The high transmittance in range 500–2500 nm is revealed in transmission spectra. The adjustable optical band is demonstrated via Tauc’s equation calculation. The blue-shift of the PL spectra due to the change of concentration is certified. The highest mobility and changeable resistivity among existing chalcogenide material are reflected via Hall measurements. In conclusion, the specific concentration of multi-materials used in the infrared field is obtained, and of nano film with transmittance to 98%–100% is got in the range 1500–2500 nm. The high mobility 8.646 × 104 cm2(V S) and low resistivity 2.3 Ω · cm in the presented chalcogenide based multi-materials are tested. Therefore, we successfully accomplished the combination of semiconductor oxide and chalcogenide. Multi-incorporation nano-composites, which can be applied both in the field of optical and electricity by adjusting the doping elements concentration, are reported in this work.

Celitement quality parameter determination by online NIR spectroscopy

A new process for the manufacture of a novel hydraulic binder (Celitement) with a high potential for saving energy and reducing carbon dioxide emissions was developed at the Karlsruhe Institute of Technology. To obtain the ideal process conditions and to monitor the optimal product quality of the binder, it was necessary to develop a measurement system for the online determination of certain quality parameters. A method for the direct calculation of different quality parameters of both precursor and final product from online measured near-infrared (NIR) spectra is presented in this article. A successful transformation between calibration models gained with laboratory and online NIR is also demonstrated. This enables optimisation of the calibration models on a laboratory scale and a seamless transfer to industrial scale due to changes in composition of the raw materials, formulation or processing parameters.

Multi-modal characterization of polymeric gels to determine the influence of testing method on observed elastic modulus

Demand for materials that mechanically replicate native tissue has driven development and characterization of various new biomaterials. However, a consequence of materials and characterization technique diversity is a lack of consensus within the field, with no clear way to compare values measured via different modalities. This likely contributes to the difficulty in replicating findings across the research community; recent evidence suggests that different modalities do not yield the same mechanical measurements within a material, and direct comparisons cannot be made across different testing platforms. Herein, we examine whether “material properties” are characterization modality-specific by analyzing the elastic moduli determined by five typical biomaterial mechanical characterization techniques: unconfined-compression, tensiometry, rheometry, and micro-indentation at the macroscopic level, and microscopically using nanoindentation. These analyses were performed in two different polymeric gels frequently used for biological applications, polydimethylsiloxane (PDMS) and agarose. Each was fabricated to span a range of moduli, from physiologic to supraphysiologic values. All five techniques identified the same overall trend within each material group, supporting their ability to appreciate relative moduli differences. However, significant differences were found across modalities, illustrating a difference in absolute moduli values, and thereby precluding direct comparison of measurements from different characterization modalities. These observed differences may depend on material compliance, viscoelasticity, and microstructure. While determining the underlying mechanism(s) of these differences was beyond the scope of this work, these results demonstrate how each modality affects the measured moduli of the same material, and the sensitivity of each modality to changes in sample material composition.