Photoluminescence of ZnS:Cu in a Polymethyl Methacrylate Matrix

The method of agents arising directly in the (poly)methyl methacrylate medium is used to synthesize ZnS:Cu quantum dots fixed in an optically transparent polymer matrix. The optical transmittance of the polymer composites in the visible spectral region reaches 92% (at the thickness 5 mm). The photoluminescence of the (poly)methyl methacrylate/ZnS:Cu composite is defined by defects in the crystal structure of ZnS and by the system of energy levels in the band gap of ZnS. The photoluminescence signal depends on the Cu-ion concentration, the reabsorption of radiation in ZnS and (poly)methyl methacrylate, and other factors.     

亚马逊首款智能手机Fire Phone发布

美国亚马逊公司发布其首款智能手机——Fire Phone.     

Mechanochemical synthesis of fine-particle γ-LiAlO<Subscript>2</Subscript>

Using thermogravimetry, in situ X-ray diffraction, room-temperature X-ray diffraction, specific surface area measurements, and particle size analysis, we have studied how preliminary mechanical activation of a mixture of aluminum hydroxide and lithium carbonate in an AGO-2 planetary mill and subsequent heat treatment of the mixture influence the synthesis of fine-particle nanostructured gamma-lithium monoaluminate. We have proposed a scheme of the structural changes accompanying the synthesis of gamma-lithium monoaluminate.     

Nanocrystallization of the amorphous Co-B-Si alloys formed by melt spinning and mechanical alloying

X-ray diffraction, differential scanning calorimetry, and transmission electron microscopy were used to investigate the thermal stability and peculiarities of nanocrystallization upon heating of amorphous Co_65.5S₁₈B₁₀ M _6.5 (M = Cr, Fe) alloys obtained by melt-spinning (MS) and mechanical alloying (MA) of mixtures of elemental components. It is shown that, irrespective of the method of manufacture, the amorphous iron-containing alloys, in general, have a lower thermal stability than the chromium-containg alloys. The thermal stability of MA alloys is lower than that of the MS alloys of the same chemical composition. The processes of nanocrystallization during heating of MS and MA amorphous alloys differ. The first crystallize, when heating, through the formation of intermediate phases, and the second, with the formation of stable crystalline phases directly from the amorphous matrix. After the crystallization, the alloys have a nanocrystalline structure with a crystallite size of about 20 nm and the same phase composition of crystallization products for the alloys of the same nominal composition obtained by MA and MS: ɛ-Co, Co₂B, and β-Co₂Si for Co_65.5Si₁₈B₁₀Cr_6.5 and α-Co, Co₂B, β-Co₂Si, and (Fe,Co)₃Si for Co_65.5Si₁₈B₁₀Fe_6.5. The results are discussed in terms of the excess free volume of the amorphous phase and of the value of its specific surface area.     

Formation of chromium carbides in copper matrix during mechanical alloying in carbon-containing media

Structural and phase transformations that occur during mechanical alloying (MA) and subsequent annealing of nanocrystalline Cu-Cr-C alloys obtained from copper and chromium powders and graphite or xylene as the source of carbon have been studied. It is shown that, when using graphite, a supersaturated Cu(Cr) solid solution and an X-ray amorphous Cr-C phase are formed during MA. Heat treatment leads to their decomposition and the appearance of Cr₃C₂ in the nanocrystalline copper matrix. When xylene is used as the source of carbon, no strongly supersaturated Cu(Cr) solid solution and no X-ray amorphous Cr-C phase are formed, but the same volume fraction of chromium carbide, i.e., 20–24 vol %, appears. When graphite is used, the carbide is formed after shorter times of MA.     

ELECTRICALLY FUSED FORSTERITE-OLIVINE,I-II*

North Carolina olivine was melted in the electric arc-resistance furnace, with simultaneous reduction of the iron (fayalite) components, to form a product consisting essentially of crystalline forsterite. The forsterite obtained from olivine by reduction was contaminated by clinoenstatite or a siliceous glass unless MgO or CaO was added to the charge. Silica, present in excess of orthosilicate proportions, was not eliminated by carbon reduction. Simultaneous reduction or vaporization of MgO prevented increase in the MgO to SiO₂ ratio by carbon reaction. Addition of theoretical amounts of MgO to the melt to produce forsterite completely eliminated the clinoenstatite and siliceous glass and resulted in an abrupt increase in high-temperature load-bearing strength. The presence of lime was detrimental to high-temperature load-bearing strength.     

严格按照中央要求继续推进节能减排工作——对吴江市印染行业近几年节能减排工作的调查

吴江市印染行业是耗能、排污大户,在当前创建资源节约型、环境友好型社会的热潮中首当其冲。吴江市丝绸协会曾于2003年6月对该行业的节能减排工作做过调研,近几年在这方面有哪些建树?根据中央对节能减排的更高要求,下一步棋应该怎么走?这是摆在大家面前的重要课题。为此,协会近期又作了调研。