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Diamond/copper composites possess excellent thermal physical properties, and its near-net-shape preparation can be successfully realized by means of melt in- filtration. The relevant process and the influencing factors of porous diamond preforms infiltrated by copper were studied. Research results showed that, it is advantageous for the infiltration process in condition that the copper blocks were placed at both the top and the bottom of porous preforms. Composite density could reach 99.3% which was near to full density, meanwhile the thermal conductivity could reach 628 W m-1 K-1, when the melt infiltration was carried out at 1230°C with the pressure of 20 MPa for 30 min. The density was not obviously increased by further improving the infiltration temperature and extending the heat holding time, however the thermal conductivity dropped, which was associated with the variation of interfacial thermal resistance due to the change of interface structure. There was an incubation period in the infiltration process, which brought that the composite density was lower and even that the infiltration cannot be completed, when infiltration temperature was below 1130°C or pressure was less than 20 MPa. [ABSTRACT FROM AUTHOR]

Abstract: An improved wax-based binder was developed for the powder injection molding of Ti–6Al–4V. A critical powder loading of 72vol% and a pseudo-plastic flow behavior were obtained by the feedstock based on the binder. The injection molding, debinding and sintering processes were studied. An ideal control of carbon and oxygen contents was achieved by thermal debinding in vacuum atmosphere (10−3 Pa). The mechanical properties of as-sintered specimens were almost equivalent to those of the same alloy made by conventional press–sintering process. Good shape retention and ±0.02mm dimension deviation were achieved. [Copyright &y& Elsevier]

The supernova remnant HESS J1731-347 is a young supernova remnant (SNR) that displays a nonthermal X-ray and TeV shell structure. A molecular cloud at a distance of ∼3.2 kpc is spatially coincident with the western part of the SNR, and it was likely hit by the SNR. The X-ray emission from this part of the shell is much lower than from the rest of the SNR. Moreover, a compact GeV emission region coincident with the cloud has been detected with a soft spectrum. These observations seem to imply a shock-cloud collision scenario at this area, where the stalled shock can no longer accelerate super-TeV electrons or maintain strong magnetic turbulence downstream, while the GeV cosmic rays (CRs) are released through this stalled shock. To test this hypothesis, we have performed a detailed Fermi-LAT reanalysis of the HESS J1731-347 region with over nine years of data. Two distinct GeV components are found, one displaying a soft spectrum is from the compact GeV emission region, the other one displaying a hard spectrum is from the rest of the SNR (excluding the cloud region). A hadronic model involving a shock-cloud collision scenario is built to explain the γ-ray emission from this area. It consists of three CR sources: run-away super-TeV CRs that have escaped from the fast shock, leaked GeV CRs from the stalled shock, and the local CR sea. The X-ray and γ-ray emission of the SNR excluding the shock-cloud interaction region is explained in a one-zone leptonic model. Our shock-cloud collision model explains the GeV–TeV observations from the clouds around HESS J1731-347, i.e., a cloud in contact with the SNR and a distant cloud in spatial coincidence to the TeV source HESS J1729-345. We find however that the leaked GeV CRs from the shock-cloud collision do not necessarily dominate the GeV emission from the clouds, due to a comparable contribution from the local CR sea. [ABSTRACT FROM AUTHOR]