physical and mechanical properties of the nanocomposite and combined Ti-N-Si /WC-Co-Cr and Ti-N-Si/(CR3C2)75-(NiCr)25 coatings

Two types of the combined nanocomposite coatings (Ti-N-Si /WC-Co-Cr and Ti-N-Si/ (Cr3C2Ni)75-(NiCr)25) of 160-320 μm thickness were produced using two deposition techniques: the cumulative-detonation and the vacuum-arc deposition with the high-frequency discharge. This gives the possibility (using the combined coatings) to restore the size of worn areas of the tools and demonstrate the high corrosion and wear resistance, to increase the hardness, modulus of elasticity, and plasticity index. Composition of the top coating varied from Ti = 60 at.%, N = 30 at.%, and Si = 10 at.% to Ti = 75 at.%, N = 20 at.%, and Si = 5 at.%. In the first series of coatings the following phases were obtained: (Ti;Si) and TiN in thin top coating and WC and W2C in thick bottom coating. The second series gives (Ti;Si)N and TiN in top coating; Cr3Ni2 and pure Cr in bottom coating; and small amount of Ti19O17 in the transition region between thin and thick coatings. For the first series the grain size achieved 25 nm at the hardness of 38 GPa. For the second series the grain size was 15 nm at the hardness of 42 GРa ± 4 GPa. It is shown that the corrosion resistance in salt solution and acid media increases with the wear decrease as a result of the cylinder friction over the surface of combined coating. При цитуванні документа, використовуйте посилання http://essuir.sumdu.edu.ua/handle/123456789/9351Отримано два види комбінованих нанокомпозитних покриттів (Ti -N-Si /WC-Co-Cr; TI-N -Si/(Cr3C2Ni)75-(NiCr)25) товщиною 160 ÷ 320 мкм з використанням двох технологій осадження: кумулятивно-детонаційним з подальшим осадженням за допомогою вакуумно-дугового джерела у ВЧ розряді. Що дає можливість, за допомогою комбінованого покриття, відновлювати розмір зношених ділянок виробів із захистом їх від корозії, зносу, при цьому збільшити твердість, модуль пружності, індекс пластичності. Склад верхнього покриття змінювали від Ti = 60 %, N ≈ 30 %, Si = 10 % до Si = 5 %; N = 20 %, Ti = 75 %. У першій серії покриттів виявлені фази (Ti, Si) і TiN в тонкому верхньому покритті і WC і W2C в товстому нижньому покритті. У другій серії, у верхньому покритті були отримані (Ti, Si) N і TiN, а в нижньому покритті Cr3Ni2, чистий Cr; невелика кількість Ti19O17 в перехідній області між тонким і товстим покриттям. Розмір зерен в першому варіанті тонкого покриття складав 25 нм, при твердості 35 ГПа, а в другому варіанті розмір зерен кристалітів складав 15 нм при твердості Н = 42 ± 3,6 ГПа. Показано, що корозійна стійкість в сольовому розчині і кислотному середовищах збільшується, при зменшенні зносу в результаті тертя циліндра по поверхні комбінованого покриття. При цитировании документа, используйте ссылку http://essuir.sumdu.edu.ua/handle/123456789/9351Получено два вида комбинированных нанокомпозитных покрытий (Ti-N-Si/WC-Co-Cr; Ti-N-Si/(Cr3C2Ni)75-(NiCr)25) толщиной 160 ÷ 320 мкм с использованием двух технологий осаждения: кумулятивно-детонационным с последующим осаждением с помощью вакуумно-дугового источника в ВЧ разряде. Что даёт возможность, при помощи, комбинированного покрытия восстанавливать размер изношенных участков изделий с защитой их от коррозии, износа, при этом увеличить твердость, модуль упругости, индекс пластичности. Состав верхнего покрытия изменяли от Ti = 60 %, N ≈ 30 %, Si = 10 % до Si = 5 %; N = 20 %, Ti = 75 %. В первой серии покрытий обнаружены фазы (Ti; Si) и TiN в тонком верхнем покрытии и WC и W2C в толстом нижнем покрытии. Во второй серии, в верхнем покрытии были получены (Ti, Si)N и TiN, а в нижнем покрытии Cr3Ni2, чистый Cr; небольшое количество Ti19O17 в переходной области между тонким и толстым покрытием. Размер, зерен в первом варианте тонкого покрытия, составлял 25 нм, при твёрдости 35 ГПа, а во втором варианте размер зёрен кристаллитов составлял 15 нм при твёрдости Н = 42 ÷ 3,6 ГПа. Показано, что коррозионная стойкость в солевом растворе и кислотной средах увеличивается при уменьшении износа в результате трения цилиндра по поверхности комбинированного покрытия. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/935

Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe

Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV

A search for a Higgs boson decaying into two photons is described. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross section of the standard model Higgs boson decaying to two photons. The expected exclusion limit at 95% confidence level is between 1.4 and 2.4 times the standard model cross section in the mass range between 110 and 150 GeV. The analysis of the data excludes, at 95% confidence level, the standard model Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The largest excess of events above the expected standard model background is observed for a Higgs boson mass hypothesis of 124 GeV with a local significance of 3.1 sigma. The global significance of observing an excess with a local significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is estimated to be 1.8 sigma. More data are required to ascertain the origin of this excess.Comment: Submitted to Physics Letters

Measurement of the Lambda(b) cross section and the anti-Lambda(b) to Lambda(b) ratio with Lambda(b) to J/Psi Lambda decays in pp collisions at sqrt(s) = 7 TeV

The Lambda(b) differential production cross section and the cross section ratio anti-Lambda(b)/Lambda(b) are measured as functions of transverse momentum pt(Lambda(b)) and rapidity abs(y(Lambda(b))) in pp collisions at sqrt(s) = 7 TeV using data collected by the CMS experiment at the LHC. The measurements are based on Lambda(b) decays reconstructed in the exclusive final state J/Psi Lambda, with the subsequent decays J/Psi to an opposite-sign muon pair and Lambda to proton pion, using a data sample corresponding to an integrated luminosity of 1.9 inverse femtobarns. The product of the cross section times the branching ratio for Lambda(b) to J/Psi Lambda versus pt(Lambda(b)) falls faster than that of b mesons. The measured value of the cross section times the branching ratio for pt(Lambda(b)) > 10 GeV and abs(y(Lambda(b))) < 2.0 is 1.06 +/- 0.06 +/- 0.12 nb, and the integrated cross section ratio for anti-Lambda(b)/Lambda(b) is 1.02 +/- 0.07 +/- 0.09, where the uncertainties are statistical and systematic, respectively.Comment: Submitted to Physics Letters

Search for new physics in events with opposite-sign leptons, jets, and missing transverse energy in pp collisions at sqrt(s) = 7 TeV

A search is presented for physics beyond the standard model (BSM) in final states with a pair of opposite-sign isolated leptons accompanied by jets and missing transverse energy. The search uses LHC data recorded at a center-of-mass energy sqrt(s) = 7 TeV with the CMS detector, corresponding to an integrated luminosity of approximately 5 inverse femtobarns. Two complementary search strategies are employed. The first probes models with a specific dilepton production mechanism that leads to a characteristic kinematic edge in the dilepton mass distribution. The second strategy probes models of dilepton production with heavy, colored objects that decay to final states including invisible particles, leading to very large hadronic activity and missing transverse energy. No evidence for an event yield in excess of the standard model expectations is found. Upper limits on the BSM contributions to the signal regions are deduced from the results, which are used to exclude a region of the parameter space of the constrained minimal supersymmetric extension of the standard model. Additional information related to detector efficiencies and response is provided to allow testing specific models of BSM physics not considered in this paper.Comment: Replaced with published version. Added journal reference and DO

Measurement of isolated photon production in pp and PbPb collisions at sqrt(sNN) = 2.76 TeV

Isolated photon production is measured in proton-proton and lead-lead collisions at nucleon-nucleon centre-of-mass energies of 2.76 TeV in the pseudorapidity range |eta|<1.44 and transverse energies ET between 20 and 80 GeV with the CMS detector at the LHC. The measured ET spectra are found to be in good agreement with next-to-leading-order perturbative QCD predictions. The ratio of PbPb to pp isolated photon ET-differential yields, scaled by the number of incoherent nucleon-nucleon collisions, is consistent with unity for all PbPb reaction centralities.Comment: Submitted to Physics Letters

Measurements of differential production cross sections for a Z boson in association with jets in pp collisions at root s=8 TeV

Peer reviewe

Measurement of the mass difference between top quark and antiquark in pp collisions at root s=8 TeV

Peer reviewe

Measurements of the t(t)Overbar charge asymmetry using the dilepton decay channel in pp collisions at root s=7 TeV

The tt¯ charge asymmetry in proton-proton collisions at s&#8730; = 7 TeV is measured using the dilepton decay channel (ee, e &#956; , or &#956;&#956; ). The data correspond to a total integrated luminosity of 5.0 fb &#8722;1 , collected by the CMS experiment at the LHC. The tt and lepton charge asymmetries, defined as the differences in absolute values of the rapidities between the reconstructed top quarks and antiquarks and of the pseudorapidities between the positive and negative leptons, respectively, are measured to be A C = &#8722;0 . 010 ± 0 . 017 (stat . ) ± 0 . 008 (syst . ) and AlepC = 0 . 009 ± 0 . 010 (stat . ) ± 0 . 006 (syst . ). The lepton charge asymmetry is also measured as a function of the invariant mass, rapidity, and transverse momentum of the tt¯ system. All measurements are consistent with the expectations of the standard model

Search for the associated production of the Higgs boson with a top-quark pair

A search for the standard model Higgs boson produced in association with a top-quark pair t t ¯ H (tt¯H) is presented, using data samples corresponding to integrated luminosities of up to 5.1 fb &#8722;1 and 19.7 fb &#8722;1 collected in pp collisions at center-of-mass energies of 7 TeV and 8 TeV respectively. The search is based on the following signatures of the Higgs boson decay: H &#8594; hadrons, H &#8594; photons, and H &#8594; leptons. The results are characterized by an observed t t ¯ H tt¯H signal strength relative to the standard model cross section, &#956; = &#963;/&#963; SM ,under the assumption that the Higgs boson decays as expected in the standard model. The best fit value is &#956; = 2.8 ± 1.0 for a Higgs boson mass of 125.6 GeV