Form Of Ribbons Research Articles

GAMES BASED LEARNING DENGAN MEDIA ORIGAMI UNTUK MENSTIMULASI KREATIVITAS ANAK USIA 6-12 TAHUN DI PUSAT SUMBER BELAJAR MASYARAKAT BUKIT MEKAR WANGI

The purpose of this research is to provide a systematic, factual and accurate description or painting of the facts, characteristics and relationships between the phenomena being investigated. Games Based Learning through Origami media to Stimulate the Creativity of Children aged 6-12 years was chosen as an interesting thing to investigate. It is hoped that this research will be useful for the community in providing alternative play and learning activities that are fun, easy and inexpensive and can be done at any time by parents and children at the same time during the Covid19 pandemic. A descriptive qualitative approach was used in this Community Service Research. The results showed changes in 3 domains of learning development. First, there is a change in the cognitive domain, this is indicated by increasing the knowledge of the trainees about the history and origins of origami. Second, there is a change in the affective domain, which is more enthusiastic and enthusiastic when participating in activities. Third, in the psychomotor domain, changes are marked by the increasing ability of participants to fold origami in the form of butterflies and ribbons. As well as the emergence of a creative attitude in making various forms of origami folds.

INCREASING THE ACCURACY OF DETERMINING THE WORKING PARAMETERS OF THE RIBBON-SHAPED ELECTRONIC FLOW IN THE ELECTRON-BEAM MICRO-PROCESSING OF DIELECTRICS

The article shows the possibility of increasing the accuracy of determining the operating parameters of the ribbon-shaped electron flow during electron beam micromachining of dielectric materials in a vacuum (using the example of Kp0 grade polycrystalline silicon and K8 grade optical glass) as a result of the analysis and selection of the most acceptable energy modes of operation of the Pierce wire electron-beam gun. The purpose of the work is to study the influence of the volt-current characteristics of the Pierce wire electron-beam gun on the quality and repeatability of the process of processing dielectric materials with a ribbon-shaped electron flow, which allows choosing the most rational modes of determining the operating parameters of the electron flow with higher accuracy.
 The paper proposes a technological experiment on electron-beam micromachining of dielectric surfaces, as well as defined and investigated the working parameters of the process of such processing, depending on the possible energy characteristics of the main working node of the electron-beam equipment, namely, the Pierce electron-beam gun.
 The operating parameters of the ribbon-shaped electron flow obtained as a result of the experimental study made it possible to ensure the highest quality processing of the surfaces of dielectric materials due to the improvement of such indicators of the accuracy of determining these parameters as precision (for example, the standard deviation of the repeatability of Sr decreased from 8.33% to 4.95%, and the standard the SR reproducibility deviation decreased from 13.28% to 6.18%), which confirms the representativeness of the working parameters, as well as the correctness (the bias of the method of determining the working parameters in the electronic flow is statistically insignificant under the conditions of the confidence interval on the axis d = 0 at the significance level a = 0.05). The analysis of the obtained results regarding the electron-beam microprocessing of the surfaces of dielectric materials according to the selected operating parameters proves the improvement of quality and the increase in the reproducibility of the results of the processing of these surfaces in terms of purity, as well as the reduction of the residual nanorelief by 18-25%.
 A comparison of the results of experimental electron-beam microprocessing of dielectrics with the results of their laser surface treatment made it possible to establish a reduction in residual micro-uniformities of the surface, as in electron-beam microprocessing (for optical glass K8 by 17-27 times; for silicon Kp0 - by 14-22 times) , as well as during surface laser treatment (for both types of material – 12-14 times). At the same time, surface laser treatment does not allow to eliminate surface waviness, which is related to the specifics of the interaction of the laser beam with the surface of the optical material, while when processing with an electron flow of the ribbon form, the occurrence of such waviness is not observed.
 The conclusions and analyzed data obtained in the article based on the results of experimental research can be used to optimize the technological regimes of electron-beam micromachining in the production of products of microoptics, integrated optics, nanoelectronics, etc.

Silicification of trilobites and biofilm from the Cambrian Weeks Formation, Utah: Evidence for microbial mediation of silicification

Abstract We report on silicified trilobite sclerites with associated silicified biofilm from the Cambrian Weeks Formation, Utah (USA), that support a role for microbial biofilms in silicification. Silicified sclerites are typically small (<3 mm) and incompletely preserved. All studied specimens are partly coated in 5–20 µm (rarely >500 µm) of silica-cemented matrix. High-resolution scanning electron microscope (SEM) study reveals the presence of two different forms of carbon-rich threads, ribbons and mats, coating both sclerites and silica-cemented matrix. Crystalline-looking biofilm threads and ribbons composed of Si, O, and C are interpreted as silicified biofilm associated with the trilobite silicification. Rippled to smooth biofilm mats composed of more C, less Si and O, and a trace of N are post-silicification. Embedded in the silica of the sclerites and matrix are molds of framboids that we interpret as originally framboidal pyrite that was engulfed by silica. These data indicate that silica precipitation continued into the surrounding matrix following the propagation of sulfate-reducing bacteria feeding on the organic matter present in the sclerite and the neighboring sediment. This strongly supports the model that bacterially mediated decay is key to the silicification of carbonate bioclasts and provides the first direct evidence of a microbial community (biofilm). A literature review reveals that silica extends past the fossil more frequently than is recognized, suggesting that silicified biofilm might be common but overlooked.

Optical Properties of 2D Micro- and Nanostructures of ZnO:K

ZnO nano- and microstructures doped with K were grown by the Vapor-Solid method. Wires and needles are the main morphology observed, although some structures in the form of ribbons and triangular plates were also obtained. Besides these, ball-shaped structures which grow around a central wire were also detected. Raman and cathodoluminescence investigations suggest that variations in morphology, crystalline quality and luminescence emissions are related to the different lattice positions that K occupies depending on its concentration in the structures. When the amount is low, K ions mainly incorporate as interstitials (Ki), whereas K occupies substitutional positions of Zn (KZn) when the amount of K is increased. Electron Backscattered Diffraction shows that ribbons and triangular plates are oriented in the (0001) direction, which indicates that the growth of this type of morphologies is related to distortions introduced by the Ki since this position favors the growth in the (0001) plane. In the case of the ball-shaped structures, the compositional analysis and Raman spectra show that they consist of K2SO4. Finally, the capability of the elongated structures to act as waveguides and optical resonators was investigated. Due to the size of the K ion, practically double that of the Zn, and the different positions it can adopt within the ZnO lattice (Ki or KZn), high distortions are introduced that compromise the resonators performance. Despite this, quality factor (Q) and fineness (F) show acceptable values (80 and 10 at 544 nm, respectively), although smaller than those reported for doping with smaller size alkali, such as Li.

Morphology and magnetic properties of rapidly quenched Fe-B alloys

Crystallization kinetics and the effect of annealing on the microstructure, morphology and magnetic properties of rapidly quenched Fe-B alloys are studied in this paper. Fe-B ribbons with different boron content were prepared ranging from 12 to 25 at%, covering the extended glass formability limit in hypoeutectic compositions to hypereutectic limit. Fe-B alloys were prepared by planar flow casting in the form of ribbons approximately 20 µm thick and 6 mm wide. The chemical compositions are Fe75B25, Fe80B20, Fe83B17, Fe86B14 and Fe88B12. Resistivity measurements were taken place at different heating rates, illustrating the phase transformations, aiding in the calculation of Avrami and Kissinger parameters. Soft magnetic properties of the Fe-B alloys were investigated by hysteresis loop measurements before and after annealing. XRD, DSC, TGA and TEM measurements illustrated the mechanisms of the crystallization process. The crystallization of Fe100-xBx amorphous alloys containing <17 at% Boron occurs by two stages of reaction. In this work, the crystallization process and Curie temperature for Fe100-xBx (12 < x < 25) are studied. Ribbons with boron content above 12 at% were found to be fully amorphous; small amount of quenched-in nano-crystallinity was present in the as-cast alloy with 12 at% B. Each composition has been annealed to achieve 5 %, 50 % and 95 % of crystallinity. In the first stage of crystallization, α-Fe phase with bcc structure crystallizes from amorphous matrix.

Antimicrobial V-Shaped Copper(II) Pentaiodide: Insights to Bonding Pattern and Susceptibility.

Antimicrobial resistance (AMR) is a major concern for the survival of mankind. COVID-19 accelerated another silent pandemic of AMR through the uncontrolled use of antibiotics and biocides. New generations of antimicrobial agents are needed to combat resistant pathogens. Crown ethers can be used as models for drug action because they are similar to antibiotics. Iodine is a well-known microbicide but is characterized by instability and short-term effectivity. Iodine can be stabilized in the form of polyiodides that have a rich topology but are dependent on their immediate surroundings. In addition, copper has been successfully used since the beginning of history as a biocidal agent. We, therefore, combined iodine and copper with the highly selective crown ether 1,4,7,10-tetraoxacyclododecane (12-crown-4). The morphology and composition of the new pentaiodide [Cu(12-crown-4)2]I5 was investigated. Its antimicrobial activities against a selection of 10 pathogens were studied. It was found that C. albicans WDCM 00054 is highly susceptible to [Cu(12-crown-4)2]I5. Additionally, the compound has good to intermediate antimicrobial activity against Gram-positive and Gram-negative bacilli. The chain-like pentaiodide structure is V-shaped and consists of iodine molecules with very short covalent bonds connected to triiodides by halogen bonding. The single crystal structure is arranged across the lattice fringes in the form of ribbons or honeycombs. The susceptibility of microorganisms towards polyiodides depends on polyiodide bonding patterns with halogen-, covalent-, and non-covalent bonding.

New-generation biocompatible Ti-based metallic glass ribbons for flexible implants

We introduce five new biocompatible Ti-based metallic glass (MG) compositions with different metalloid and soft metal content for a synergistic improvement in corrosion properties. Without any potentially harmful elements such as Cu, Ni or Be, these novel alloys can eliminate the risk of inflammatory reaction when utilized for permanent medical implants. Excluding Cu, Ni or Be, which are essential for Ti-based bulk MG production, on the other hand, confines the glass-forming ability of novel alloys to a moderate level. In this study, toxic-element free MG alloys with significant metalloid (Si–Ge–B, 15–18 at.%) and minor soft element (Sn, 2–5 at.%) additions are produced in ribbon form using conventional single-roller melt spinning technique. Their glass-forming abilities and their structural and thermal properties are comparatively investigated using X-ray diffraction (XRD), synchrotron XRD and differential scanning calorimetry. Their corrosion resistance is ascertained in a biological solution to analyze their biocorrosion properties and compare them with other Ti-based bulk MGs along with energy dispersive X-ray. Ti60Zr20Si8Ge7B3Sn2 and Ti50Zr30Si8Ge7B3Sn2 MG ribbons present a higher pitting potential and passivation domain compared with other Ti-based MG alloys tested in similar conditions. Human mesenchymal stem cell metabolic activity and cytocompatibility tests confirm their outstanding cytocompatibility, outperforming Ti-Al6-V4.

Compositional design and in vitro investigation on novel Zr–Co–Cu–Ti metallic glass for biomedical applications

Zr–Co–Cu–Al based metallic glasses (MGs) are potential material for making surgical equipment due to their ultra-high strength. However, presence of elemental Al in these alloys is not desirable due to biotoxicity. To counter this problem the present study is undertaken to design metallic glass forming composition by replacing Al with Ti. Design strategy adopted is based on thermodynamic modelling by rationalizing the effect of chemical enthalpy and atomic mismatch entropy along with statistically controlled atomic arrangement through configurational entropy. The rapid solidification technique was used to synthesize MG in melt spun ribbon form. The structural nature and glass stability of the ribbon are confirmed by X-Ray diffraction, transmission electron microscopy and differential scanning calorimetry. Corrosion response of the MG is thoroughly investigated using potentiodynamic polarization and electrochemical impedance spectroscopy in a simulated body fluid (SBF) environment. The mechanical property of MG is evaluated using microindentation technique. Improvement in corrosion resistance is observed in all the SBF solutions along with in vitro biocompatibility study using MG-63 cell viability experiment.

Effect of Cu and Co addition on non-isothermal crystallization kinetics of rapidly quenched Fe-Sn-B based alloys

Crystallization kinetics of rapidly quenched Fe-Sn-B alloys under non-isothermal conditions were studied using differential scanning calorimetry. Formation of crystalline phases was analyzed by X-ray diffraction. Nominal chemical compositions were Fe81Sn7B12, (Fe3Co1)81Sn7B12 and (Fe81Sn7B12)99Cu1. Alloys were prepared by planar flow casting in the form of ribbons approximately 20 µm thick and 6 mm wide. Mechanism of crystallization was studied under framework of the Johnson-Mehl-Avrami-Kolmogorov model. Alloys exhibit two stages of crystallization. Results show decrease in activation energy of the first stage of crystallization with addition of Cu and increase with addition of Co. Crystallization mechanism of the first stage of crystallization for Fe81Sn7B12 and (Fe81Sn7B12)99Cu1 alloy starts as growth with increasing nucleation rate and continues as growth with decreasing nucleation rate. Addition of Co changes mechanism of crystallization. Which in case of (Fe3Co1)81Sn7B12 alloy starts as a growth with increasing nucleation rate. Then changes to growth with decreasing nucleation rate. After which nucleation rate decreases to zero. Rest of crystallization stage is governed by growth of pre-existing nuclei. In the first stage of crystallization α-Fe phase with bcc structure crystallizes from amorphous matrix. In the second stage of crystallization the remaining amorphous matrix crystalizes into tetragonal Fe2B phase and hexagonal FeSn phase. After the first stage of crystallization, 50 % to 55 % volume of studied alloys were crystalized. Addition of Cu decreases crystalline size of α-Fe crystallites by 60 % and decreases concentration of Sn in α-Fe phase by 0.8 at. %. Addition of Co doesn't affect the size of α-Fe crystallites and decreases the concentration of Sn in α-Fe phase by 1.7 at. %.

Magnetic structure, magneto-caloric properties and magnetic critical behaviours of LaMn2Ge2 compounds

The structural and magnetic properties of LaMn2Ge2 compound in both the as-cast bulk and melt-spun ribbon forms have been investigated by a comprehensive set of x-ray/neutron powder diffraction, magnetic and heat capacity measurements as well as corresponding sets of data analyses. Our neutron diffraction study reveals that with decreasing temperature the magnetic state of bulk LaMn2Ge2 changes first from paramagnetic to incommensurate antiferromagnetism AFfs at TN ~ 430 K, and then gives way to incommensurate canted ferromagnetism Fmi below TC ∼ 320 K. No noticeable magnetoelastic effect was detected in the temperature dependence of lattice parameters derived from the refinement of the neutron diffraction patterns over the temperature range ~ 5–460 K. Detailed analyses of the magnetic data indicate that the magnetic phase transition around the ferromagnetic transition (TC ∼ 320 K) is second order. Under field changes of 2 T and 5 T, the maximum values of magnetic entropy change around the ferromagnetic transition respectively reach -ΔSmax = 1.65 J/kg K and -ΔSmax = 3.26 J/kg K for the bulk sample, compared with -ΔSmax = 1.21 J/kg K and -ΔSmax = 2.60 J/kg K, for the ribbon sample. The magnetic phase transition around TC has been investigated by Kouvel-Fisher analysis and the Modified Arrott Plot method with the critical exponent values indicating that the magnetic interactions in LaMn2Ge2 are long range. Moreover, it was found that the field- and temperature- magnetisation data around TC collapse onto two curves obeying the single scaling equation M(H,ε) = εβf ± (H/εβ+γ) for both the bulk and ribbon samples. With a field change of ΔB = 5 T and ΔB = 8 T, the relative cooling power for bulk sample around 320 K is derived to be RCP ~ 115 J/kg and RCP ~ 199 J/kg, respectively. These findings indicate that LaMn2Ge2 could be a promising candidate for magnetic refrigeration applications in the room temperature region.

Влияние редкоземельных металлов на стеклообразующую способность и кристаллизацию аморфных сплавов CoFeSiBNb

In present work amorphous alloys Co48Fe25Si4B19Nb4-R (R = Nd, Sm, Tb, Yb) were obtained by planar flow casting in the form of ribbons with 3-5 mm wide and 35-45 μm thickness. It was found that crystallization process goes into two stages and depends on the used rare-earth addition and its content in the alloy by differential thermal analysis method. Glass-forming ability criteria were calculated. It is shown that paramagnetic Curie temperature of alloys in liquid state can be used as their a-priori criterion of glass-forming ability.

The influence of rare-earth metals on glass-forming ability and crystallization of CoFeSiBNb amorphous alloys

In present work amorphous alloys Co48Fe25Si4B19Nb4-R (R = Nd, Sm, Tb, Yb) were obtained by planar flow casting in the form of ribbons with 3-5 mm wide and 35-45μm thickness. It was found that crystallization process goes into two stages and depends on the used rare-earth addition and its content in the alloy by differential thermal analysis method. Glass-forming ability criteria were calculated. It is shown that paramagnetic Curie temperature of alloys in liquid state can be used as their a-priori criterion of glass-forming ability. Keywords: amorphous alloys, crystallization, glass-forming ability, differential thermal analysis, x-ray diffraction, rare-earth metals.\

Microstructural and Magnetic Properties of Mn2fesi Heusler Alloys Prepared in Bulk and Ribbon Form

Microstructural and Magnetic Properties of Mn2fesi Heusler Alloys Prepared in Bulk and Ribbon Form

Crystallization and magnetic properties of ThMn12-type Sm-Fe-Co-Ti-Si based magnetic materials

Si-doped Fe-rich compounds, i.e., Sm(Fe0.8Co0.2)11Ti + Six (x = 0, 0.5, and 1.0), with ThMn12-type structure in forms of ribbons and bulks were fabricated using melt-spinning process and high pressure pressing and heat treatment processes. Physical and magnetic properties of the ribbons and bulks were analyzed to investigate Si doping effects on the Sm(Fe0.8Co0.2)11Ti. The Si-free ribbons were found to be amorphous, while the small amount of Si doping resulted in dramatic crystallization of the ThMn12 phase. Coercivity of the ribbons increased with the increasing Si content from 43 to 3140 Oe, while the magnetization decreased from 146 to 78 emu/g. It was observed that the Si-free ribbons consisted of nano-sized grains in the matrix of an amorphous phase. On the other hand, the Si-doped ribbons exhibited submicron-sized grains with high crystallinity. The crystallized phases of the heat-treated bulks varied with the Si concentrations; the main phase was the ThMn12 phase in all samples, but concentrations of soft magnetic α-Fe phase decreased with the increasing Si concentration, and corresponding saturation magnetizations of the bulks also decreased.

Structure and Magnetic Properties of Thermodynamically Predicted Rapidly Quenched Fe85-xCuxB15 Alloys.

In this work, based on the thermodynamic prediction, the comprehensive studies of the influence of Cu for Fe substitution on the crystal structure and magnetic properties of the rapidly quenched Fe85B15 alloy in the ribbon form are performed. Using thermodynamic calculations, the parabolic shape dependence of the ΔGamoprh with a minimum value at 0.6% of Cu was predicted. The ΔGamoprh from the Cu content dependence shape is also asymmetric, and, for Cu = 0% and Cu = 1.5%, the same ΔGamoprh value is observed. The heat treatment optimization process of all alloys showed that the least lossy (with a minimum value of core power losses) is the nanocomposite state of nanocrystals immersed in an amorphous matrix obtained by annealing in the temperature range of 300–330 °C for 20 min. The minimum value of core power losses P10/50 (core power losses at 1T@50Hz) of optimally annealed Fe85-xCuxB15 x = 0,0.6,1.2% alloys come from completely different crystallization states of nanocomposite materials, but it strongly correlates with Cu content and, thus, a number of nucleation sites. The TEM observations showed that, for the Cu-free alloy, the least lossy crystal structure is related to 2–3 nm short-ordered clusters; for the Cu = 0.6% alloy, only the limited value of several α-Fe nanograins are found, while for the Cu-rich alloy with Cu = 1.2%, the average diameter of nanograins is about 26 nm, and they are randomly distributed in the amorphous matrix. The only high number of nucleation sites in the Cu = 1.2% alloy allows for a sufficient level of grains’ coarsening of the α-Fe phase that strongly enhances the ferromagnetic exchange between the α-Fe nanocrystals, which is clearly seen with the increasing value of saturation induction up to 1.7T. The air-annealing process tested on studied alloys for optimal annealing conditions proves the possibility of its use for this type of material.

Magnetoelastic Ribbons as Vibration Sensors for Real-Time Health Monitoring of Rotating Metal Beams

In the current work, magnetoelastic material ribbons are used as vibration sensors to monitor, in real time and non-destructively, the mechanical health state of rotating beam blades. The magnetoelastic material has the form of a thin ribbon and is composed of Metglas alloy 2826 MB. The study was conducted in two stages. In the first stage, an experiment was performed to test the ability of the ribbon to detect and transmit the vibration behavior of four rotating blades, while the second stage was the same as the first but with minor damages introduced to the blades. As far as the first stage is concerned, the results show that the sensor can detect and transmit with great accuracy the vibratory behavior of the rotating blades, through which important information about the mechanical health state of the blade can be extracted. Specifically, the fast Fourier transform (FFT) spectrum of the recorded signal revealed five dominant peaks in the frequency range 0–3 kHz, corresponding to the first five bending modes of the blades. The identification process was accomplished using ANSYS modal analysis, and the comparison results showed deviation values of less than 1% between ANSYS and the experimental values. In the second stage, two types of damages were introduced to the rotating blades, an edge cut and a hole. The damages were scaled in number from one blade to another, with the first blade having only one side cut while the last blade had two side cuts and two holes. The results, as was expected, show a measurable shifting on the frequency values of the bending modes, thus proving the ability of the proposed magnetoelastic sensors to detect and transmit changes of the mechanical state of rotating blades in real time.

Stereoisomeric selection upon adsorption: A structural and optical study of curcuminoid derivatives on ultrathin films of KCl on Au(111) and on bulk KCl(001)

We present a combined scanning tunneling microscopy (STM), noncontact atomic force microscopy (nc-AFM), and differential reflectance spectroscopy (DRS) study aiming at the characterization of the relationship between structural and optical properties of a supramolecular assembly of a curcuminoid derivative adsorbed on two kinds of substrates: bilayers of KCl on Au(111) [2 ML KCl/Au(111)] and KCl(001) bulk. The molecule features a difluoroboron (${\mathrm{BF}}_{2}$) complex as well as cyano (CN) end groups, which induces an internal dipole moment of a few Debyes. The comparative study of the structural properties of the molecules adsorbed on 2 ML KCl/Au(111), which allows for STM characterization, and KCl bulk, which allows for nc-AFM and DRS characterization, shows that the molecular adsorption is similar on both substrates. STM and nc-AFM give evidence that the on-surface condensation of the molecules into supramolecular assemblies is steered by two main interactions: the molecule-substrate interaction between the CN end groups of the molecule and the cationic ${\mathrm{K}}^{+}$ species, as well as an in-plane intermolecular interaction involving ${\mathrm{BF}}_{2}$ and phenyl groups. Based on density functional theory calculations, we propose an epitaxial molecular structure described by a two-molecule unit cell forming an $8\ifmmode\times\else\texttimes\fi{}2$ supercell on the KCl surface that grows in form of ribbons along the $\ensuremath{\langle}100\ensuremath{\rangle}$ or $\ensuremath{\langle}010\ensuremath{\rangle}$ directions of the substrate, which are polar. Among several possible stereoisomers for the molecule, it is found that the balance between vertical and in-plane interactions selects the one whose size matches the distance between ${\mathrm{K}}^{+}$ species to condense on the substrate and not the most stable one stemming from the gas phase. Finally, optical spectroscopy in solvent and DRS measurements performed on the supramolecular assembly exhibit similar features identified as three absorption peaks tracing a $\ensuremath{\pi}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{*}$ electronic transition followed by a vibronic progression, plus a broader band featuring a set of higher-energy transitions. Due to both the weak electrostatic interactions and a lack of $\ensuremath{\pi}\text{\ensuremath{-}}\ensuremath{\pi}$ interactions in the condensed molecular phase, DR spectra exhibit no major excitonic effect, but a nonrigid redshift of the molecular absorption band compared to the situation in solvent. This observation is found to be consistent with the isomer selection due to the transition from the gas phase to the on-surface condensed phase.

Tuning structural preference of negatively charged B16 by ionically or covalently interacting with alkali and coinage metals

The planar ribbon form is the lowest-energy structure of the neutral and negatively charged B16 clusters, especially planar B162− with ten delocalized π electrons is viewed as an all-boron naphthalene, whereas the doped B16TM− by transition metals unexpectedly exhibit the high coordinated TM-centered tubular structures. We found herein a totally different picture in B16M−/B16TM− (M = Li, Na, K; TM = Ag, Au) doped by s-block metals (being isoelectronic to B162−) relative to the reported B16-based clusters. A new quasi-planar trapezoid structure is predicted to be a global minimum, where B16TM− (TM = Ag, Au) presents chemistry similar to that of hydrogen in its bonding to boron. The chemical bonding and structural integrity of the quasi-planar trapezoid structure is not altered significantly in B16M−, suggesting its stability and viability as a promising building block for boron-assembled nanomaterials.

Effect of External Impacts on the Structure and Martensitic Transformation of Rapidly Quenched TiNiCu Alloys

TiNi-TiCu quasibinary system alloys with a high Cu content produced by rapid quenching from liquid state in the form of thin amorphous ribbons exhibit pronounced shape memory effect after crystallization and are promising materials for miniaturized and fast operating devices. There is currently no complete clarity of the mechanisms of structure formation during crystallization from the amorphous state that determine the structure-sensitive properties of these alloys. This work deals with the effect of the initial amorphous state structure and crystallization method of the alloys on their structure and phase transformations. To this end the alloy containing 30 at.% Cu was subjected to thermal and mechanical impact in the amorphous state and crystallized using isothermal or electropulse treatment. We show that after all types of treatment in the amorphous state the structure of the alloy remains almost completely amorphous but the characteristic temperatures and enthalpy of crystallization become slightly lower. Isothermal crystallization of alloy specimens produces a submicrocrystalline structure with an average grain size in the 0.4–1.0 μm range whereas electropulse crystallization generates a bimorphic structure consisting of large 4–6 μm grains and 2–3 μm high columnar crystals in the vicinity of the surface. The grains have nanosized plate-like and subgrain structures. The largest grains are observed in thermally activated samples, meanwhile, mechanical impact in the amorphous state leads to the formation of equiaxed finer grains with a less defective subgrain structure and to the shift of the temperature range of the martensitic transformation toward lower temperatures.

Cobalt Content Effect on the Magnetic Properties of Ni50-xCoxMn35.5In14.5 Annealed Ribbons.

We present a study of the annealing effect and its influence on magnetic and structural properties for a series of Heusler alloys () prepared in ribbon form. We studied the morphology and composition using scanning electron microscopy (SEM) equipped with an X-ray microanalyzer (EDX). The magnetic properties were determined by two methods: electron magnetic resonance (EMR) and vibrating sample magetometer (VSM). We found that cobalt content in the annealed samples reveals an additional magnetic phase transition at lower temperatures.