Influence of porogen type and copper powder morphology on property of sintering copper porous materials

Copper porous materials have been manufactured by the method of powder metallurgy.Electrolytic copper powders and atomized copper powders are used as matrix material.Methylcellulose and paraffin are used as porogen.The influence of porogen type and copper powder morphology on the property of copper porous materials is investigated as well.The results show that copper porous materials with paraffin as porogen have lower porosity and permeability compared with materials using methylcellulose as porogen,due to the different pore-forming mechanisms.The pore forming mechanism of methylcellulose is thermal decomposition,while the pore forming mechanism of paraffin is melting–evaporation.The morphology of copper powders affects the contact state between adjacent powders,which further influence the sintering shrinkage.The porous materials using arborescent copper powders as matrix have lower porosity,smaller pore size and lower permeability,compared with materials with atomized copper powders as matrix.

Syntheses and Structures of Three Hybrid Materials Using Vanadium Polyoxoanions and Macrocyclic Copper Complex as Building Blocks

The reactions of the four-coordinated macrocyclic copper complex [CuL]（ClO4）2（L = 1,4,8,11-tetraazacyclotetradecane） with NH4VO3 under different conditions gave three inorganic-organic hybrid materials of [CuL][VO3]2·2.33H2O（1）, [CuL]3[V（10）O（28）]·8H2O（2） and [Cu L]3[V6O（18）]·8H2O（3）. Single-crystal X-ray diffraction analyses reveal that three diverse vanadium polyoxoanions, [V6O（18）]6- ring, [V（10）O（28）]6- cluster, and [V（12）O（35）]^10- ring, were isolated from the same reactant NH4VO3 under different conditions. The [CuL]^2＋ bridges the [V10O28]6- clusters to form a two-dimensional sheet in 2, and link the [V6O（18）]^6- rings in 1 and [V（12）O（35）]^10- rings in 3 into three-dimensional frameworks, respectively.

Researches for higher electrical conductivity copper-based materials

Copper and copper-based materials are widely used in power electronics,auto-mobiles,mechanical manufacturing and high-tech manufacturing fields such as aerospace,telecommunications and integrated circuits owing to their compre-hensive advantages in mechanical,electrical conductivity and processing prop-erties.With the rapid development of technology,many emerging technical fields have introduced more challenging requirements for the electrical conductivity of copper.This article reviews the research status of high-conductivity copper-based materials and introduces three methods to improve electrical conductivity,including purification,alloying and addition of nanocarbon materials.We sum-marise the advantages,disadvantages and future development trends of methods for improving copper conductivity.The key to producing high-conductivity copper-based materials is development of low-cost,continuous and stable processes.

Precipitation of flaky moolooite and its thermal decomposition

Moolooite particles with flaky morphology were synthesized by mixing dilute solutions of copper nitrate and sodium oxalate in the presence of citric acid. Solution p H value, citric acid concentration, and stirring were found to have large effect on the shape of the precipitated particles. Under the stirring, the radial area of flaky moolooite particles was enlarged and extended to become a thinner and larger flake. This is ascribed to growth promotion caused by the selective absorption of citric ligands onto a particular crystalline surface of the moolooite particles. Flaky shape of the moolooite particles tended to become spherical and disappeared completely when decomposed under an Ar atmosphere, leading to the formation of large porous aggregated particles composed of many tiny nanosized copper crystals.

Electroless plating of copper layer on surfaces of urea-formaldehyde microcapsule particles containing paraffin for low infrared emissivity

A copper coating was deposited by electroless plating on the surfaces of urea-formaldehyde microcap- sules containing paraffin （UFP） particles. This composite microcapsule structure had low infrared OR） emissivity and maintained a constant temperature, and could be used in IR stealth applications. The eiectroless copper layer formation and its micro-appearance, and the effect of the copper layer on the IR emissivity and thermal properties of the composite microcapsules were investigated. The IR emissivity of the composite microcapsules at wavelengths of 1-14 μm gradually decreased with increasing copper mass on the surface. After formation of an integrated copper layer, the rate of IR emissivity decrease was lower. This is because the copper coating improves the surface conductivity of the UFP; a high conductivity results in high reflectivity, which leads to a decrease in IR emissivity. The lowest IR emissivity achieved was 0.68. The phase-change enthalpy of the composite microcapsules decreased with increasing amount of copper coated on the surface because of the high density of copper. When the mass increase of the UFP after electroless copper plating was about 300%, the composite microcapsules had low IR emissivity （about 0.8） and a high phase-change enthalpy （80J/g）.