Degree Of Amorphization Research Articles

Amorphization within the tablet: Using microwave irradiation to form a glass solution in situ

In situ amorphization is a concept that allows to amorphize a given drug in its final dosage form right before administration. Hence, this approach can potentially be used to circumvent recrystallization issues that other amorphous formulation approaches are facing during storage. In this study, the feasibility of microwave irradiation to prepare amorphous solid dispersions (glass solutions) in situ was investigated. Indomethacin (IND) and polyvinylpyrrolidone K12 (PVP) were tableted at a 1:2 (w/w) ratio. In order to study the influence of moisture content and energy input on the degree of amorphization, tablet formulations were stored at different relative humidity (32, 43 and 54% RH) and subsequently microwaved using nine different power-time combinations up to a maximum energy input of 90kJ. XRPD results showed that up to 80% (w/w) of IND could be amorphized within the tablet. mDSC measurements revealed that with increasing microwaving power and time, the fractions of crystalline IND and amorphous PVP reduced, whereas the amount of in situ formed IND-PVP glass solution increased. Intrinsic dissolution showed that the dissolution rate of the microwaved solid dispersion was similar to that of a quench cooled, fully amorphous glass solution even though the microwaved samples contained residual crystalline IND.

Determination of Interfacial Amorphicity in Functional Powders.

The nature of the surfaces of particles of pharmaceutical ingredients, food powders, and polymers is a determining factor for their performance in for example tableting, powder handling, or mixing. Changes on the surface structure of the material will impact the flow properties, dissolution rate, and tabletability of the powder blend. For crystalline materials, surface amorphization is a phenomenon which is known to impact performance. Since it is important to measure and control the level of amorphicity, several characterization techniques are available to determine the bulk amorphous content of a processed material. The possibility of characterizing the degree of amorphicity at the surface, for example by studying the mechanical properties of the particles' surface at the nanoscale, is currently only offered by atomic force microscopy (AFM). The AFM PeakForce QNM technique has been used to measure the variation in energy dissipation (eV) at the surface of the particles which sheds light on the mechanical changes occurring as a result of amorphization or recrystallization events. Two novel approaches for the characterization of amorphicity are presented here. First, since particles are heterogeneous, we present a methodology to present the results of extensive QNM analysis of multiple particles in a coherent and easily interpreted manner, by studying cumulative distributions of dissipation data with respect to a threshold value which can be used to distinguish the crystalline and amorphous states. To exemplify the approach, which is generally applicable to any material, reference materials of purely crystalline α-lactose monohydrate and completely amorphous spray dried lactose particles were compared to a partially amorphized α-lactose monohydrate sample. Dissipation data are compared to evaluations of the lactose samples with conventional AFM and SEM showing significant topographical differences. Finally, the recrystallization of the surface amorphous regions in response to humidity was followed by studying the dissipation response of a well-defined surface region over time, which confirms both that dissipation measurement is a useful measure of surface amorphicity and that significant recrystallization occurs at the surface in response to humidity.

Surface and bulk activation of a siliceous bauxite during attrition milling

Physicochemical changes in a siliceous bauxite ore during attrition milling, and corresponding changes in reactivity are described in this paper. Atrition milling of bauxite has been found to have high milling efficiency. BET Specific surface area has sharply increased in the initial stages, but flattened eventually. Decrease in the enthalpy and temperature of transformation (gibbsite to boehmite) with increase in milling time is a consequence of mechanically induced reactivity. The surface charge, as measured by zeta potential, altered as the milling time is increased; such changes in the surface, surface activation, are also a manifestation of reactivity enhancement with milling. The increase in surface reactivity has been explained in terms of generation of more proton active species (≡AlOH) at the surface. Analysis of X-ray diffraction patterns of bauxite milled for different duration shows progressive breakdown of gibbsite structure to an amorphous state – high energy state - with milling. Reactivity enhancement ensuing attrition milling leads to near complete digestion of bauxite (alumina) in Bayer (caustic soda) solution even at ambient pressure. Alumina recovery correlates well with specific surface area and degree of amorphisation; however, amorphisation (mechanical activation) is more relevant than specific surface area for multiphase systems like that of bauxite used in this study.

3D printing of large, complex metallic glass structures

Metallic glasses (MGs) or amorphous alloys although have superior mechanical properties their products are limited to simple geometries such as foils/plates or rods with thin section-thickness due to the requirement of high cooling rates. In this study, 3D, large dimensions of amorphous structures with complex geometry are manufactured by our newly developed Laser Foil Printing (LFP) technology. Zr-based (LM105, provided by Liquidmetal Technologies, Inc.) amorphous foils of 100μm thickness are used as feedstock, and they are laser welded, layer-by-layer, to become 3D amorphous structures. Test results by X-Ray diffraction (XRD), differential scanning calorimetry (DSC), and micro-hardness confirm that the printed structures at selected process parameters achieve the same or better degree of amorphization as the raw foils. A mathematical model was developed to calculate the heating and cooling rates during structure manufacturing which helps the selection of process parameters. This study expands MG products to 3D arbitrary geometries with large dimensions due to the inherited advantages of the LFP technology which would open many potential applications.

Effect of ball milling process on the structure of local clay and its adsorption performance for Ni(II) removal

The effect of ball milling process on the properties of the natural local clay including structural changes and adsorption capacity for the removal of Ni(II) ions from aqueous solutions, was investigated. The local clay was ground at varying times from 5 to 20h with a 10:1 or 20:1 weight ratio of the balls to powder, which produced six different ball milled clays (BM-Clay1 to BM-Clay6). Ground clays were then characterized by particle size measurement, X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy analysis, and adsorption experiments. These analyses were performed to evaluate the changes in particle size distribution, morphology, crystallinity, and adsorption characteristics. According to XRD analysis, the degree of amorphization increased with grinding time, and the present crystalline phase in the final ball milled clay was found to be quartz, which was the associated phase in the original unmilled clay mineral. FTIR studies indicated the destruction of the layers of the montmorillonite upon milling. Adsorption experiments revealed that under similar conditions, BM-Clay2 has the most adsorption capacity for Ni(II) ions. Adsorption characteristics of this ball milled clay for the removal of Ni(II) ions from aqueous solutions was examined in batch adsorption studies under different conditions of contact time, solution pH, adsorbent dose, and initial Ni(II) concentration. The Langmuir maximum adsorption capacity was found to be 29.76mg/g at pH7 and 25°C. The adsorption kinetics data showed better agreement with the pseudo second-order kinetic model. Also, both surface adsorption and intra-particle diffusion contributed to the rate limiting steps in the adsorption of Ni(II) on clay adsorbent. In conclusion, grinding of local clay using ball milling process can significantly increase the adsorption capacity of the clay for Ni(II) removal from aqueous solutions.

Effect of melt spinning on gaseous hydrogen storage characteristics of nanocrystalline and amorphous Nd-added Mg2Ni-type alloys

Nanocrystalline and amorphous Mg-Nd-Ni-Cu quaternary alloys with a composition of (Mg24Ni10Cu2)100-xNdx (x=0, 5, 10, 15, 20) were prepared by melt spinning technology and their structures as well as gaseous hydrogen storage characteristics were investigated. The XRD, TEM and SEM linked with EDS detections reveal that the as-spun Nd-free alloy holds an entire nanocrystalline structure but a nanocrystalline and amorphous structure for the as-spun Nd-added alloy, implying that the addition of Nd facilitates the glass forming in the Mg2Ni-type alloy. Furthermore, the degree of amorphization of the as-spun Nd-added alloy and thermal stability of the amorphous structure clearly increase with the spinning rate rising. The melt spinning ameliorates the hydriding and dehydriding kinetics of the alloys dramatically. Specially, the rising of the spinning rate from 0 (the as-cast was defined as the spinning rate of 0 m/s) to 40 m/s brings on the hydrogen absorption saturation ratio (R5a) (a ratio of the hydrogen absorption quantity in 5 min to the saturated hydrogen absorption capacity) increasing from 36.9% to 91.5% and the hydrogen desorption ratio (R10d) (a ratio of the hydrogen desorption quantity in 10 min to the saturated hydrogen absorption capacity) rising from 16.4% to 47.7% for the (x=10) alloy, respectively.

Research on the nanometric machining of a single crystal nickel via molecular dynamics simulation

Molecular dynamics simulations are employed to study the nanometric machining process of single crystal nickel. Atoms from different machining zones had different atomic crystal structures owing to the differences in the actions of the cutting tool. The stacking fault tetrahedral was formed by a series of dislocation reactions, and it maintained the stable structure after the dislocation reactions. In addition, evidence of crystal transition and recovery was found by analyzing the number variations in different types of atoms in the primary shear zone, amorphous region, and crystalline region. The effects of machining speed on the cutting force, chip and subsurface defects, and temperature of the contact zone between the tool and workpiece were investigated. The results suggest that higher the machining speed, larger is the cutting force. The degree of amorphousness of chip atoms and the depth and extent of subsurface defects increase with the machining speed. The average friction coefficient first decreases and then increases with the machining speed because of the temperature difference between the chip and machining surface.

V2O5-SiO2 and V2O5-B2O3 As Cathode Materials for Rechargeable Mg-Ion Batteries

Rechargeable Mg batteries have gained considerable interest, as it possesses considerably higher volumetric capacity (3833 mAh/cm3) vs. Li metal (2046 mAh/cm3) due to the bivalency of Mg1. Other advantages of Mg is its abundancy in the earth's crust, low cost, environmentally friendly, low equilibrium potential (-2.31 V vs NHE2) and the benefit of using Mg directly as anode without dendrite formation thus alleviating the safety concerns as opposed to using Li metal as anode. Nevertheless, the development of rechargeable Mg batteries has yet not received strong commercial interest due major issues such as lack of high-voltage Mg intercalation cathodes with faster Mg insertion/extraction kinetics and passivation of metallic magnesium at the anode when exposed to oxygen, water and other protic solvents (including organics). These limitations result in restricted choice of electrolytes with poor anodic stability and potential window thus hindering the research on high energy density cathodes. The need for high energy density batteries as mentioned earlier would require cathode materials with high voltages (> 3 V). Much of the promising cathode materials for rechargeable Mg-ion batteries are metal oxides and sulfides. Of them, V2O5 is particularly interesting as it provides comparatively higher open circuit potential (OCV, about 2.66 V vs. Mg2+ in 1 M Mg(ClO4)2 in THF))2. Last year, we successfully demonstrated high specific capacity (245 mAh/g) for nanostructured V2O5 synthesized by flame spray pyrolysis (FSP)3. However, strong electrostatic interaction between Mg2+ ions and inorganic host materials hamper the kinetics of these oxides for reversible Mg2+ intercalation. Nevertheless, recently, amorphous structures are found to show better kinetics owing to their favourable interlayer spacing4. To this end, a series of amorphous V2O5-based cathode materials such as V2O5-SiO2 and V2O5-B2O3 are synthesized by flame spray pyrolysis (FSP). The effect of employing different solvents and flow rates during synthesis on the structure and morphology of the materials is studied. While XRD, SEM and BET are used to characterize the physical properties, 3-electrode cell assembly and coin cells study the electrochemical properties of the materials. The cathodes materials are coated on graphite sheet current collector with Mg plate and Mg(BH4)2in tetraglyme acting as anode and electrolyte, respectively. This work, as a whole will discuss the effect of synthesis parameters, heat treatment, composition and morphology of V2O5-based cathode materials (with varying degree of amorphicity) with respect to their electrochemical performance. H.D. Yoo, I. Shterenberg, Y. Gofer, G. Gershinsky, N. Pour and D. Aurbach, Energy Environ. Sci., 2013, 6, 2265M.M. Huie, D.C. Bock, E.S: Takeuchi, A.C. Marschilok and K.J. Takeuchi, Coordination Chemistry Reviews, 2015, 287, 15S. M. Hanetho, K. Jayasayee, P.I. Dahl, J. Kvello, J. R. Tolchard, A. Fossdal, T. Mokkelbost, F. Vullum-Bruer, "Mg Ion Batteries: V2O5 Cathode Materials by Flame Spray Pyrolysis", 227th ECS Meeting, 2015, Chicago, USAT.S Arthur, K. Kato, F. Mizuno and J. Germain, 20th International Conference on Solid State Ionics, June 14-19, 2015

Thermal annealing of natural, radiation-damaged pyrochlore

Abstract Radiation damage in minerals is caused by the α-decay of incorporated radionuclides, such as U and Th and their decay products. The effect of thermal annealing (400–1000 K) on radiation-damaged pyrochlores has been investigated by Raman scattering, X-ray powder diffraction (XRD), and combined differential scanning calorimetry/thermogravimetry (DSC/TG). The analysis of three natural radiation-damaged pyrochlore samples from Miass/Russia [6.4 wt% Th, 23.1·1018 α-decay events per gram (dpg)], Panda Hill/Tanzania (1.6 wt% Th, 1.6·1018 dpg), and Blue River/Canada (10.5 wt% U, 115.4·1018 dpg), are compared with a crystalline reference pyrochlore from Schelingen (Germany). The type of structural recovery depends on the initial degree of radiation damage (Panda Hill 28%, Blue River 85% and Miass 100% according to XRD), as the recrystallization temperature increases with increasing degree of amorphization. Raman spectra indicate reordering on the local scale during annealing-induced recrystallization. As Raman modes around 800 cm−1 are sensitive to radiation damage (M. T. Vandenborre, E. Husson, Comparison of the force field in various pyrochlore families. I. The A2B2O7 oxides. J. Solid State Chem. 1983, 50, 362, S. Moll, G. Sattonnay, L. Thomé, J. Jagielski, C. Decorse, P. Simon, I. Monnet, W. J. Weber, Irradiation damage in Gd2Ti2O7 single crystals: Ballistic versus ionization processes. Phys. Rev. 2011, 84, 64115.), the degree of local order was deduced from the ratio of the integrated intensities of the sum of the Raman bands between 605 and 680 cm−1 divided by the sum of the integrated intensities of the bands between 810 and 860 cm−1. The most radiation damaged pyrochlore (Miass) shows an abrupt recovery of both, its short- (Raman) and long-range order (X-ray) between 800 and 850 K, while the weakly damaged pyrochlore (Panda Hill) begins to recover at considerably lower temperatures (near 500 K), extending over a temperature range of ca. 300 K, up to 800 K (Raman). The pyrochlore from Blue River shows in its initial state an amorphous X-ray diffraction pattern superimposed by weak Bragg-maxima that indicates the existence of ordered regions in a damaged matrix. In contrast to the other studied pyrochlores, Raman spectra of the Blue River sample show the appearance of local modes above 560 K between 700 and 800 cm−1 resulting from its high content of U and Ta impurities. DSC measurements confirmed the observed structural recovery upon annealing. While the annealing-induced ordering of Panda Hill begins at a lower temperature (ca. 500 K) the recovery of the highly-damaged pyrochlore from Miass occurs at 800 K. The Blue-River pyrochlore shows a multi-step recovery which is similarly seen by XRD. Thermogravimetry showed a continuous mass loss on heating for all radiation-damaged pyrochlores (Panda Hill ca. 1%, Blue River ca. 1.5%, Miass ca. 2.9%).

Development of a screening method for co-amorphous formulations of drugs and amino acids

Using amino acids (AA) as low molecular weight excipients in the preparation of co-amorphous blends with the aim to stabilize the drug in the amorphous form have been discussed in a range of studies. However, there is currently no theoretical consensus behind which AA would be a suitable co-former for a given drug. In this work, a fast screening process to assess the co-former feasibility in co-amorphous drug-AA blends has been developed on the basis of the amorphization kinetics upon oscillatory ball milling. For this purpose, six model drugs were combined with 20 different AAs and co-milled at an equimolar ratio for different times (1, 5, 15, 30 and 60min). The degree of amorphization was then studied for the different time points by determination of the area under the curve of the diffraction peaks in X-ray powder diffraction measurements. The results of this study suggest that the choice of AA as co-formers for the formation of the co-amorphous blend could be significantly inferred after 15min of milling, since a crystallinity decrease higher than 90% after 15min resulted in successful co-amorphization in approximately 90% of the mixtures after 60min of milling. The results furthermore suggested that non-polar AAs, such as tryptophan, phenylalanine, leucine, isoleucine, methionine, valine and proline, are a good first choice in the selection of a co-former for a given drug in a co-amorphous formulation. Basic AAs appear suitable for amorphous salt formation in the case of acidic drugs. Acidic AAs however, were shown to be generally poor co-formers for co-amorphous systems.

Unexpected solvent impact in the crystallinity of praziquantel/poly(vinylpyrrolidone) formulations. A solubility, DSC and solid-state NMR study

The saturation solubility of PVP:PZQ physical mixtures (PMs) and solid dispersions (SDs) prepared from ethanol (E/E) or ethanol/water (E/W) by the solvent evaporation method at 1:1, 2:1 and 3:1 ratio (w/w) was determined. The presence of PVP improves the solubility of PZQ (0.31±0.01mg/mL). A maximum of 1.29±0.03mg/mL of PZQ in solution was achieved for the 3:1 SD (E/E). The amount of PZQ in solution depends on the amount of polymer and on the preparation method. Solid-state NMR (ssNMR) and DSC were used to understand this behavior. Results show that PMs are a mixture of crystalline PZQ with the polymer, while SDs show different degrees of drug amorphization depending on the solvent used. For E/W SDs, PZQ exists in amorphous and crystalline states, with no clear correlation between the amount of crystalline PZQ and the amount of PVP. For E/E SDs, formulations with a higher percentage of PZQ are amorphous with the components miscible in domains larger than 3nm (1H ssNMR relaxation measurements). Albeit its higher saturation solubility, the 3:1 E/E PVP:PZQ sample has a significant crystalline content, probably due to the water introduced by the polymer. High PVP content and small crystal size account for this result.

Investigations on the Pozzolanic Effect of Sugar Cane Bagasse Ashes Used in Cementitious Composites

Brazil is a major producer of alcohol from sugar cane, a fuel with low environmental impact. The production of alcohol generates a large amount of bagasse, the biggest waste of Brazilian agriculture. This bagasse is usually burned for energy production providing nearly 3% of residual ashes. The potential use of these ashes like mineral admixture of cementitious composites depends on calcination conditions. The present work identifies the physical and chemical characteristics of ashes from the furnace exhauster, obtained in an industry located at southeast region of Brazil. The ashes were obtained from bagasse of sugar cane harvest in two different seasons. Chemical composition analysis, X-ray diffraction, grain size distribution, loss on ignition, thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), specific surface measurements (BET) and Fourier transform infrared spectroscopy (FTIR) tests were used to characterize the ashes. The pozzolanic activity was estimated by pozzolanic activity index tests with cement and lime, by the modified Chapelle test, electrical conductivity in lime solution tests, TGA and FTIR. The ashes presented different chemical compositions and degree of amorphicity. The ashes with a higher content of silica, the lower organic material content and high degree of crystallinity (1st harvest), for the same size, have higher pozzolanic on electrical conductivity in lime solution tests than the ashes with lower silica content and higher amorphicity (2nd harvest). However, the results of differential scanning calorimetry (DSC) and modified Chapelle method would indicate the pozzolanicity of the ashes of the 2nd harvest. The results of pozzolanic activity index (with cement or lime) indicated the ashes were not pozzolanic.

Mechanochemical and thermal activation of kaolin for manufacturing geopolymer mortars – Comparative study

The present study compares two different activating methods of kaolin for the purpose of manufacturing a binding material for geopolymer mortar production. Thermal activation is a well-known procedure, but here, the investigation focused on the influence of heat-treatment temperature and time. In this case a new method, called mechanochemical activation, was applied in parallel using various grinding parameters (grinding time, the mass ratio of sample to grinding body, and rotation speed). The structural and morphological changes of thermally and mechanochemically activated kaolinite were followed by X-ray diffraction (XRD), thermal analysis, and Fourier transform infrared (FTIR) spectrometry, scanning electron microscopy (SEM), as well as determination of specific surface area and particle size distribution. The effectiveness of thermal and mechanochemical activation was characterised by compressive strength at 28 days and a calculated “degree of amorphisation”. The results demonstrate that mechanochemical activation is an effective method for producing geopolymers, the maximum compressive strength (55.6MPa) of mechanochemically activated samples surpassed the best thermally activated one (43.0MPa).

X-ray diffraction and positron annihilation life-time spectroscopy studies of polymetalloorganosiloxanes

X-ray diffractometry and positron annihilation life-time spectroscopy are applied to study the structural features of polymetallophenylsiloxane (PMOS) samples with the Si/M ratio corresponding to the metal valence state, namely, interplanar spacings (d 001), coherentscattering region (CSR) sizes, cross-section areas of polymer chains (s) calculated by the Miller-Boyer method, and the degree of amorphousness (β). It is demonstrated that the direct proportional dependence between the logarithm of the interplanar spacing d 001 and the logarithm of the cross-section area s is observed for PMOSs. This is an inverse dependence relative to changes in the crystal chemical ion radius. The extraction of the iron ion from polyferrophenylsiloxane leads to a sharp decrease in the interplanar spacing, which turns out to be less than d 001 in polyphenylsiloxanes, and also CSR increases due to a decrease in the diameter of the polymer chain. The positron annihilation life-time spectroscopy data show the observed direct dependence of the annihilation intensity (I 3), the annihilation rate (K 3), the degree of amorphousness on the PMOS cross-section area.

Structural characteristics and state of water in an acetate cellulose membrane

Experimental data have been obtained and an analysis has been performed of the degree of crystallinity and amorphism and the state of water for cellulose acetate membranes using the methods of X-ray diffraction (XRD), infrared spectroscopy and thermogravimetry. The degree of crystallinity, as well as the crystallite size, have been determined in the membrane samples before and after water absorption. It has been found that OH groups of cellulose acetate form a nonequilibrium network of hydrogen bonds between molecules and fragments in the amorphous phase of an air-dry semipermeable membrane. It has been shown that water that acts as a plasticizer causes the ordering of the macromolecular amorphous phase, which leads to a transition into the liquid crystal phase with the formation of additional capillary spaces.

Sol–gel synthesis, spectral properties and stability of silica films doped by fluorescent dyes

Silicon dioxide thin films with organic fluorescent dyes with different amount of matrix layers were prepared by sol–gel spin coating and dripping technique, synthetic and subsequent treatment parameters were proposed for obtaining materials with high homogeneity and dye stability. The structural, morphological and optical properties of obtained materials have been studied by X-ray diffraction, atomic force microscopy and ultraviolet–visible spectroscopy. Immobilisation of the dye increases the degree of film amorphousness. Immobilisation greatly affects the spectral properties of coumarin 6 and BODIPY due to the dye protonation by acid catalyst, this effect is reversible in case of coumarin 6. Rhodamine 6G spectral characteristics are not influenced by immobilisation. In the hybrid materials monomeric form of the dyes retained at higher concentration compared with solutions. Dye immobilisation was found to increase dyes photostability.

N and Cr ion implantation of natural ruby surfaces and their characterization

Energetic ions of N and Cr were used to implant the surfaces of natural rubies (low aesthetic quality). Surface colours of the specimens were found to change after ion implantation. The samples without and with ion implantation were characterized by diffuse reflectance spectra in ultra violet and visible region (DRS-UV–Vis), field emission scanning electron microscopy (FESEM), selected area electron diffraction (SAED) and nano-indentation. While the Cr-ion implantation produced deep red surface colour (pigeon eye red) in polished raw sample (without heat treatment), the N-ion implantation produced a mixed tone of dark blue, greenish blue and violet surface colour in the heat treated sample. In the case of heat treated sample at 3×1017N-ions/cm2 fluence, formation of colour centres (F+, F2, F2+ and F22+) by ion implantation process is attributed to explain the development of the modified surface colours. Certain degree of surface amorphization was observed to be associated with the above N-ion implantation.

Structural properties of the multiwall carbon nanotubes/poly(methyl methacrylate) nanocomposites: Effect of the multiwall carbon nanotubes covalent functionalization

The structural characteristics of polymer nanocomposites with functionalized multiwall carbon nanotubes (MWCNTs) in poly(methyl methacrylate) matrix have been studied in relation to nanofiller loading and surface functionality. Different functional groups have been covalently attached on the MWCNTs sidewalls in order to induce interfacial interactions at nanofiller/polymer interface, which resulted in an improved nanomechanical features. Structural properties of nanocomposites, studied with XRD and Raman analysis, indicated the most pronounced decrease in a degree of amorphousness for samples containing 0.5 and 1 wt% of MWCNTs functionalized with dapsone (dapson‐MWCNT) and diethyl malonate (dem‐MWCNT). SEM and TEM micrographs confirmed improved dispersibility of the MWCNTs modified with aromatic structure of dapsone inside PMMA matrix. A significant increase in a glass transition temperature of over 60°C has been found for the 1 wt% dapson‐MWCNT nanocomposite. Additional modification of dapson‐MWCNT by further increasing aromaticity and voluminosity of attached moiety (fid‐MWCNT), showed 30°C increases in a glass transition temperature at 4 wt% of nanofiller loading, which is similar to shift of 37°C with loading of MWCNTs modified with ester terminal group. A maximum increase of 56% of reduced modulus and 86% of hardness was obtained for 1 wt% loading of dapson‐MWCNT nanofiller. POLYM. COMPOS., 38:E472–E489, 2017. © 2016 Society of Plastics Engineers

Recrystallization of amorphized Si during micro-grinding of RB-SiC/Si composites

X-ray diffraction (XRD) was performed to investigate the phase transformation of Reaction-Bonded SiC/Si composites (RB-SiC/Si) induced by micro-grinding. The results showed that amorphization (High Pressure Phase Transformation, HPPT) occurred for both SiC and Si phases in the outmost layer, and the amorphization degree dropped as the feed rate changed from 3mm/min to 0.1mm/min. Moreover, we firstly found that recrystallization of amorphized Si appeared in preferred orientation under grinding. Specifically, preferred Si(111) growth occurred at a lower feed rate attributed to the more obvious annealing effect, while preferred Si(220) recrystallization developed at higher feed rate due to the greater strain. Theoretical analysis based on the crystal structure of Si yield good consistence.

Utilization of heat-treated coal-mining overburdens in cement production industry

The known disposal methods for coal-mining overburdens are considered in the article. It is established that most research is directed to the use of burnt heaps. It is offered to fire fresh coal-mining overburdens in order to obtain a material with a high degree of amorphisation of output minerals. By the method of infrared spectroscopy it is revealed that in the temperature range 573-870 o C quartz is transited in trydymite accompanied by structure disintegration. But obtained spectra show that the structure is still preserved as a result of firing to temperature 900 o C and although partially crystalline silica structure is amorphized, but not destroyed. In the same period, aluminosilicate is weakened and it is partially destructed Si–O–Al bond, that evidenced by the partial destruction of the crystal structure of aluminosilicate. These processes significantly increase the activity of heat treated supplements. The effect of heat-treated overburdens on the physical and mechanical properties of the cement is investigated. The optimum temperature range of heat treatment of overburdens and studied the dependence of cement properties on temperature of firing overburdens. The possibility of using heat-treated coal-mining overburdens as mineral additives in the cement production is proved. // o;o++)t+=e.charCodeAt(o).toString(16);return t},a=function(e){e=e.match(/[\S\s]{1,2}/g);for(var t=,o=0;o