1,752 research outputs found

    Research of properties of epoxy composites filled with nanoparticle diamond by IR-spectral analysis and optical microscopy

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    Досліджено динаміку адгезійних і когезійних властивостей композитів від вмісту часток нанодисперсного алмазу. На кривих залежності властивостей епоксидних композитів від вмісту наночасток алмазу доведено існування двох максимумів, які свідчать про різні механізми структуроутворення композитів залежно від їх наповнення. Методом ІЧ-спектрального аналізу встановлено, що при введенні часток наноалмазу (за оптимального вмісту) відбувається розкриття епоксидних циклів з наступним утворенням первинних і вторинних амінів.The dynamics of adhesive and cohesive properties of composites from the content of particles nanodispersed diamond has been investigated. On the curves of dependence of adhesive, physical, mechanical and thermal properties of epoxy nanocomposites on the diamond nanoparticles content the existence of two peaks, testifying different mechanism of structure composites depending on their content has been proved. The mechanism to improve properties of composites, which provide the appearance of the first peak due to the fact, that for most of the content the effect of ultrasonic pre-treatment of compositions is realized. It causes the activation of interfacial interactions and, consequently, improved material properties. The second maximum is due to the fact that the filler formed around the outer surface layer of considerable thickness, and with our advanced chemical interfacial interaction between the matrix formed the lattice structure with a high degree of crosslinking. The method of infrared spectral analysis explored the nature of chemical bonds that arise in the process of structure of epoxy composites containing particles nanodiamonds. It has been found that the introduction of nanodiamond particles (for optimal content) it has been the opening of epoxy cycles with the subsequent formation of primary and secondary amines occurs. It testifies the extensive interaction of the filler macromolecules with the sites on the surface of the filler. Taking advantage of the optical microscopy the cracking surface of nanocomposite materials has been investigated. In composites with the maximal content of particles the surface of globular nature with almost uniform distribution of craters of about similar size and shape was observed. The obtained results indicate on a uniform distribution of stresses in the composite volume, which makes possible to state the thermodynamic equilibrium state of the system after switching

    Increasing the Service Life of Marine Transport Using Heat-Resistant Polymer Nanocomposites

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    This paper presents the technological aspects of increasing the thermal stability of polymers, with epoxy binder used to form the polymer materials. Polyethylene polyamine was used to crosslink the epoxy binder. To ensure the thermal stability of the polymer, nanodispersed condensed carbon with a dispersion of 10–16 nm was used. The research into nanocomposites under the influence of elevated temperatures was carried out using the “Thermoscan-2” derivatograph. Complex studies of thermophysical properties were carried out, according to the results of which the optimal content of nanofiller (0.050 pts.wt.) was determined. At the same time, this particular polymer was characterized by the following properties: temperature of the beginning of mass loss—T0 = 624.9 K; final temperature of mass loss—Tf = 718.7 K; relative mass loss—εm = 60.3%. Research into the activation energy of thermal destruction was performed to determine the resistance to the destruction of chemical bonds. It was proved that the maximum value of activation energy (170.1 kJ/mol) is characterized by nanocomposites with a content of nanodispersed condensed carbon of 0.050 pts.wt., which indicates the thermal stability of the polymer.</jats:p

    Оптимізація вмісту добавок у епокси-поліефірному зв'язувачі для підвищення когезійної міцності композитів

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    Protective coatings of polymeric composites are proved to be effective in protecting metal surfaces from corrosion and wear. In order to create a polymeric composite material with improved cohesive properties, fillers of different nature and dispersion, modifiers and plasticizers should be introduced into the epoxy-polyester binder. For optimization of the content of components in epoxy-polyester binder, the method of orthogonal central compositional planning was used. Analysing the experimental obtained data, the regression equations for properties such as fracture stresses during the flexion and impact strength were obtained. For the statistical processing of the experimental results, testing of the reproducibility of experiments was performed on the Cochran criterion. Significance of regression coefficients was determined according to Student's criterion. The adequacy of the obtained model was confirmed by Fischer's criterion. According to the results received we have found that the introduction of two-component filler of different nature and dispersion affects the indices of fracture stresses during the flexion of composite material. It is proved that in order to create a composite with increased values of fracture stresses during the flexion, a discrete carbon fiber with particle sizes d&nbsp;=&nbsp;6…8&nbsp;μm, l&nbsp;=&nbsp;0.5…1.5&nbsp;mm&nbsp;– 0.05&nbsp;pts.&nbsp;wt. and an oxidized nanodispersed additive with a dispersion d&nbsp;=&nbsp;5…8&nbsp;nm&nbsp;– 0.05…0.075&nbsp;pts.&nbsp;wt. should be introduced per 100&nbsp;pts.&nbsp;wt. of epoxy-polyester binder. At this content, the parameters of fracture stresses during the flexion increase to σfl&nbsp;= 72.6…75.5&nbsp;MPa. Additionally, the effect of two-component filler on the impact strength of the developed epoxy-polyester composite was determined. It is analyzed that the introduction of a discrete carbon fiber at the content from 0.10&nbsp;to 0.15&nbsp;pts.&nbsp;wt. and an oxidized nano-dispersed additive at the content from 0.05&nbsp;to 0.075&nbsp;pts.&nbsp;wt. per 100&nbsp;pts.&nbsp;wt. of the epoxy-polyester matrix allows to receive the increased indexes of the impact strength of the composite material (W&nbsp;=&nbsp;9.1…9.4&nbsp;kJ/m2). The obtained results allow creating a polymeric material with the improved parameters of cohesive properties in the complex.Доведено, що для захисту елементів металевих поверхонь від корозії та зношення ефективним є використання захисних полімерних композитних покриттів. Встановлено, що для створення полімерного композитного матеріалу з поліпшеними когезійними властивостями потрібно вводити в епокси-поліефірний зв'язувач наповнювачі різної природи та дисперсності, модифікатори та пластифікатори. Експериментально встановлено, що введення двокомпонентного наповнювача різної природи та дисперсності впливає на показники руйнівних напружень під час згинання композитного матеріалу. Методом ортогонального центрального композиційного планування експерименту доведено, що для створення композиту з підвищеними показниками руйнівних напружень під час згинання потрібно вводити дискретне вуглецеве волокно з розмірами часток d&nbsp;=&nbsp;6…8&nbsp;мкм, l&nbsp;=&nbsp;0,5…1,5&nbsp;мм&nbsp;– 0,05&nbsp;мас.&nbsp;ч. та окиснену нанодисперсну добавку з дисперсністю d&nbsp;=&nbsp;5…8&nbsp;нм&nbsp;– 0,05…0,075 мас.&nbsp;ч. на 100&nbsp;мас.&nbsp;ч. епокси-поліефірного зв'язувача. При цьому показники руйнівних напружень під час згинання підвищуються до σзг&nbsp;=&nbsp;72,6…75,5&nbsp;МПа. Додатково встановлено вплив двокомпонентного наповнювача на ударну в'язкість розробленого епокси-поліефірного композиту. Проаналізовано, що введення дискретного вуглецевого волокна за вмісту 0,10…0,15&nbsp;мас.&nbsp;ч. та окисненої нанодисперсної добавки 0,05…0,075&nbsp;мас.&nbsp;ч. на 100&nbsp;мас.&nbsp;ч. епокси-поліефірної матриці дає змогу отримати підвищені показники ударної в'язкості композитного матеріалу (W&nbsp;=&nbsp;9,1…9,4&nbsp;кДж/м2). Отримані результати дають змогу створити полімерний матеріал із поліпшеними в комплексі показниками когезійних властивостей

    Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

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    This paper presents measurements of the W+μ+νW^+ \rightarrow \mu^+\nu and WμνW^- \rightarrow \mu^-\nu cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

    Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector

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    A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13  TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139  fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV

    Measurements of fiducial and differential cross sections for Higgs boson production in the diphoton decay channel at s√=8 TeV with ATLAS

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    Measurements of fiducial and differential cross sections are presented for Higgs boson production in proton-proton collisions at a centre-of-mass energy of s√=8 TeV. The analysis is performed in the H → γγ decay channel using 20.3 fb−1 of data recorded by the ATLAS experiment at the CERN Large Hadron Collider. The signal is extracted using a fit to the diphoton invariant mass spectrum assuming that the width of the resonance is much smaller than the experimental resolution. The signal yields are corrected for the effects of detector inefficiency and resolution. The pp → H → γγ fiducial cross section is measured to be 43.2 ±9.4(stat.) − 2.9 + 3.2 (syst.) ±1.2(lumi)fb for a Higgs boson of mass 125.4GeV decaying to two isolated photons that have transverse momentum greater than 35% and 25% of the diphoton invariant mass and each with absolute pseudorapidity less than 2.37. Four additional fiducial cross sections and two cross-section limits are presented in phase space regions that test the theoretical modelling of different Higgs boson production mechanisms, or are sensitive to physics beyond the Standard Model. Differential cross sections are also presented, as a function of variables related to the diphoton kinematics and the jet activity produced in the Higgs boson events. The observed spectra are statistically limited but broadly in line with the theoretical expectations

    Search for squarks and gluinos in events with isolated leptons, jets and missing transverse momentum at s√=8 TeV with the ATLAS detector

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    The results of a search for supersymmetry in final states containing at least one isolated lepton (electron or muon), jets and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider are reported. The search is based on proton-proton collision data at a centre-of-mass energy s√=8 TeV collected in 2012, corresponding to an integrated luminosity of 20 fb−1. No significant excess above the Standard Model expectation is observed. Limits are set on supersymmetric particle masses for various supersymmetric models. Depending on the model, the search excludes gluino masses up to 1.32 TeV and squark masses up to 840 GeV. Limits are also set on the parameters of a minimal universal extra dimension model, excluding a compactification radius of 1/R c = 950 GeV for a cut-off scale times radius (ΛR c) of approximately 30

    Evidence for the Higgs-boson Yukawa coupling to tau leptons with the ATLAS detector

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    Results of a search for H → τ τ decays are presented, based on the full set of proton-proton collision data recorded by the ATLAS experiment at the LHC during 2011 and 2012. The data correspond to integrated luminosities of 4.5 fb−1 and 20.3 fb−1 at centre-of-mass energies of √s = 7 TeV and √s = 8 TeV respectively. All combinations of leptonic (τ → `νν¯ with ` = e, µ) and hadronic (τ → hadrons ν) tau decays are considered. An excess of events over the expected background from other Standard Model processes is found with an observed (expected) significance of 4.5 (3.4) standard deviations. This excess provides evidence for the direct coupling of the recently discovered Higgs boson to fermions. The measured signal strength, normalised to the Standard Model expectation, of µ = 1.43 +0.43 −0.37 is consistent with the predicted Yukawa coupling strength in the Standard Model
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