Mechanical activation time of 6B2O3–13Al powder mixture vs. structure and phase composition of SHS products

The paper discusses the time of mechanical activation of the 6B2O3–13Al powder mixture affecting the selfpropagating high-temperature synthesis (SHS), exothermic reaction temperature, structure, and phase composition of synthesis products. It is found that the time increase of the mechanical activation up to 180 min leads to a reduction in the average size of aluminum and boron trioxide particles down to 4.8 and 3.5 μm, respectively. Aluminum particles with boron trioxide inclusions are observed on the particle surface and inside their structure. Changes in the particle size and structure in the initial mixture components modify the SHS reaction front from chaotic to by layers. The structure of SHS products consists of the alumina layer (63–68 wt%) with aluminum dodecaboride (AlB12) particles (32–37 wt%) distributed under this layer. After 10 and 60 min of mechanical activation, acicular and elongated AlB12 particles appear in products synthesized from the 6B2O3–13Al powder mixture. Based on the data obtained, the SHS with subsequent mechanical activation is proposed for the fabrication of the Al2O3/AlB12 nanocomposite from the 6B2O3–13Al powder mixture. It is shown that after washing grinded SHS products with hydrochloric acid solution, the synthesized powder contains 100 wt% AlB1

A theoretical and experimental investigation on the SHS synthesis of (HfTiCN)-TiB2 high-entropy composite

In this work, a fundamental possibility of obtaining a high-entropy ceramic (HfTiCN)-TiB2 composite material by the coupled self-propagating high-temperature synthesis is shown. To search for a stable fixed composition of the HfTiCN compound, the USPEX code was used with the CASTEP interface at 0K. According to the XRD analysis, the obtained SHS product is represented by HfTiCN phase (60 wt%) and TiB2 phase (40 wt%). Based on the results of XRD, elemental analysis, and the heat pattern of combustion of the Hf-Ti-C-N-B powder mixture, a probable mechanism for the formation of the (HfTiCN)-TiB2 composite material during the coupled self-propagating high-temperature synthesis was proposed

Digital binary phase-shift keyed signal detector

We have developed the effective algorithm for detecting digital binary phase-shift keyed signals. This algorithm requires a small number of arithmetic operations over the signal period. It can be relatively easy implemented based on the modern programmable logic devices. It also provides high interference immunity by identifying signal presence when signal-to-noise ratio is much less that its working value in the receiving path. The introduced detector has intrinsic frequency selectivity and allows us to form the estimate of the noise level to realize the adaptive determination of decision threshold. In order to get confirmation of the detector operability and performance, we suggest the expressions for false alarm and missing probabilities. In addition, we have examine, both theoretically and experimentally, the influence of the detector parameters on its characteristics

Phase composition, structure and properties of the spark plasma sintered ceramics obtained from the Al12Mg17-B-Si powder mixtures

In this work, composite materials were obtained by spark plasma sintering of an Al12Mg17-B-Si powder mixture. The structure, phase composition, and mechanical properties of the obtained composites were studied. It was found that various compounds based on B12 icosahedrons, such as AlB12, B4Si, and B6Si, are formed during spark plasma sintering. Based on the SEM images and results of XRD analysis of the obtained specimens, a probable scheme for the formation of the phase composition of composite materials during spark plasma sintering was proposed. An increase in the Al12Mg17-B powder content in the initial mixture from 30 to 70 wt% leads to an increase in hardness from 16.55 to 21.24 GPa and a decrease in the friction coefficient and wear rate from 0.56 to 0.32 and 13.60 to 5.60 10−5 mm−3/(N/m), respectively

Efficiency of Finding Muon Track Trigger Primitives in CMS Cathode Strip Chambers

In the CMS Experiment, muon detection in the forward direction is accomplished by cathode strip chambers~(CSC). These detectors identify muons, provide a fast muon trigger, and give a precise measurement of the muon trajectory. There are 468 six-plane CSCs in the system. The efficiency of finding muon trigger primitives (muon track segments) was studied using~36 CMS CSCs and cosmic ray muons during the Magnet Test and Cosmic Challenge~(MTCC) exercise conducted by the~CMS experiment in~2006. In contrast to earlier studies that used muon beams to illuminate a very small chamber area ($< \! 0.01$~m$^2$), results presented in this paper were obtained by many installed CSCs operating {\em in situ} over an area of $\approx \! 23$~m$^2$ as a part of the~CMS experiment. The efficiency of finding 2-dimensional trigger primitives within 6-layer chambers was found to be~$99.93 \pm 0.03\%$. These segments, found by the CSC electronics within $800$~ns after the passing of a muon through the chambers, are the input information for the Level-1 muon trigger and, also, are a necessary condition for chambers to be read out by the Data Acquisition System

Measuring the free fall of antihydrogen

After the first production of cold antihydrogen by the ATHENA and ATRAP experiments ten years ago, new second-generation experiments are aimed at measuring the fundamental properties of this anti-atom. The goal of AEGIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) is to test the weak equivalence principle by studying the gravitational interaction between matter and antimatter with a pulsed, cold antihydrogen beam. The experiment is currently being assembled at CERN's Antiproton Decelerator. In AEGIS, antihydrogen will be produced by charge exchange of cold antiprotons with positronium excited to a high Rydberg state (n > 20). An antihydrogen beam will be produced by controlled acceleration in an electric-field gradient (Stark acceleration). The deflection of the horizontal beam due to its free fall in the gravitational field of the earth will be measured with a moire deflectometer. Initially, the gravitational acceleration will be determined to a precision of 1%, requiring the detection of about 105 antihydrogen atoms. In this paper, after a general description, the present status of the experiment will be reviewed

Two-particle correlations in azimuthal angle and pseudorapidity in inelastic p + p interactions at the CERN Super Proton Synchrotron

Results on two-particle ΔηΔϕ correlations in inelastic p + p interactions at 20, 31, 40, 80, and 158 GeV/c are presented. The measurements were performed using the large acceptance NA61/SHINE hadron spectrometer at the CERN Super Proton Synchrotron. The data show structures which can be attributed mainly to effects of resonance decays, momentum conservation, and quantum statistics. The results are compared with the Epos and UrQMD models.ISSN:1434-6044ISSN:1434-605

Exploring the WEP with a pulsed cold beam of antihydrogen

The AEGIS experiment, currently being set up at the Antiproton Decelerator at CERN, has the objective of studying the free fall of antimatter in the Earth's gravitational field by means of a pulsed cold atomic beam of antihydrogen atoms. Both duration of free fall and vertical displacement of the horizontally emitted atoms will be measured, allowing a first test of the WEP with antimatter