• Korean Journal of Materials Research
• /
• v.28 no.10
• /
• pp.601-609
• /
• 2018

To study the effects of graphite shape and the composite fabricating method on the mechanical properties of graphite/copper (Gr/Cu) composites, a copper composite using graphite flakes or graphite granules as reinforcing phases is fabricated using mechanical mixing or electroless plating method. The mechanical properties of the Gr/Cu composites are evaluated by compression tests, and the compressive strength and elongation of the Gr/Cu composites using graphite granules as a reinforcing phase are compared with those of Cu composites with graphite flakes as a reinforcing phase. The compressive yield strength or maximum strength of the Gr/Cu composites with graphite granules as a reinforcing phase is higher than that of the composites using graphite flakes as a reinforcing phase regardless of the alignment of graphite. The strength of the composite produced by the electroless plating method is higher than that of the composite material produced by the conventional mechanical mixing method regardless of the shape of the graphite. Using graphite granules as a reinforcing phase instead of graphite flakes improves the strength and elongation of the Gr/Cu composites in all directions, and reduces the difference in strength or elongation according to the direction.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.3 no.1
• /
• pp.75-84
• /
• 1993

Copper coating on graphite powders was carried out by cementation process from copper sulfate solution. Effects of operation variables such as copper ion concentration, stirring speed, reaction time and temperature were investigated to obtain optimum conditions for continuous and uniform copper coating on graphite powders. The activation energy of the copper coating process was found to be 3. 59kcal/mole.

• Journal of Powder Materials
• /
• v.16 no.6
• /
• pp.389-395
• /
• 2009

A Si-CuO-graphite composite was prepared by a mechanical alloying (MA) method. The Si-CuO composite has a mixture structure, where CuO is homogeneously dispersed in Si. Also, $Cu_2O$ and $Cu_3Si$ phases were formed during MA and heat treatment. Graphite with the Si-CuO composite was mixed in the same mill for 30 minutes with weight ratio of Si-CuO composite and graphite as 1:1. The Si-CuO composite was homogeneously covered with graphite. SiC phase was not formed. Electrochemical tests of the composite have been investigated, and the first charge and discharge capacities of the material were about 870mAh/g and 660mAh/g, respectively. Those values are about 76% of the first cycle efficiency. The cycle life of the composite showed that the initial discharge capacity of 660 mAh/g could be maintained up to 92% after 20 cycles.

• Journal of Korea Foundry Society
• /
• v.12 no.3
• /
• pp.238-247
• /
• 1992

A carbon fiber(CF) reinforced Cu-10%Sn alloy matrix composite was successfully fabricated by squeeze casting method employing preheated graphite mold and proper process controlling factors. The matrix solidification microstructure of the Cu-10%Sn/CF composite reveals ${\alpha}-dendrite$ and ${\alpha}+{\delta}$ eutectoid. To compare the squeeze cast Cu-10%Sn/CF compostie with PM route fabricated Cu-graphite composites for electric contact material, mechanical wear and electrical arc wear tests were performed. Mechanical wear rate of the Cu-10%Sn/CF is much lower than that of the Cu-graphite composite. Weight loss with a variation of contact number in electrical arc wear tests shows a similar trend between the squeeze cast Cu-10%Sn/CF and PM Cu-graphite composites.

• Korean Journal of Materials Research
• /
• v.3 no.2
• /
• pp.103-110
• /
• 1993

Abstract It has been attempted to make the copper-graphite composites by deposition of copper on the surface of graphite through the hydrogen reduction of copper chlorides. Both KISH and natural graphites of less than 325 mesh were used as substrates and the hydrogen reduction also was conducted in the range of 350-50$0^{\circ}C$. The distribution of copper on the surface of graphite was found to increase with the decrease of reduction temperature. In addition. the partial pressure of hydrogen played an important role in the overall rate of reduction which was substantially dominated by the chemical reaction on the surface of each particle. It was concluded that the reduction temperature should be maintained as low as possible to accomplish the well distribution of copper in the composites.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.33 no.6
• /
• pp.500-504
• /
• 2020

Heating films were prepared with composites of poly (methyl methacrylate) and conductive graphite. The as-prepared composite was deposited on a PET film and then fabricated using a bar coater to produce a film with uniform thickness. Copper electrodes were attached to both ends of the as-prepared film, and the heating characteristics of the film were analyzed while applying a DC voltage. The electrical conductivity and heating temperature of the heating films depended on the size, structure, content, and the dispersion characteristics of the graphite in the composite. The thermal energy was adjusted by controlling the electrical energy, based on the Joule heating theory. The electrical resistance of the film was altered in proportion to Ohm's law, and the heating temperature was changed according to the structure of the film (interelectrode spacing or electrode length) and the conductive graphite content. When the content of conductive graphite in the film increases, the electrical resistance decreases, and the heating temperature increases; however, there is no significant change above a certain content (50%).

• Journal of Powder Materials
• /
• v.27 no.1
• /
• pp.25-30
• /
• 2020

Recently, the amount of heat generated in devices has been increasing due to the miniaturization and high performance of electronic devices. Cu-graphite composites are emerging as a heat sink material, but its capability is limited due to the weak interface bonding between the two materials. To overcome these problems, Cu nanoparticles were deposited on a graphite flake surface by electroless plating to increase the interfacial bonds between Cu and graphite, and then composite materials were consolidated by spark plasma sintering. The Cu content was varied from 20 wt.% to 60 wt.% to investigate the effect of the graphite fraction and microstructure on thermal conductivity of the Cu-graphite composites. The highest thermal conductivity of 692 W m^-1K^-1 was achieved for the composite with 40 wt.% Cu. The measured coefficients of thermal expansion of the composites ranged from 5.36 × 10^-6 to 3.06 × 10^-6K^-1. We anticipate that the Cu-graphite composites have remarkable potential for heat dissipation applications in energy storage and electronics owing to their high thermal conductivity and low thermal expansion coefficient.

• Journal of Powder Materials
• /
• v.9 no.6
• /
• pp.441-448
• /
• 2002

Dispersions of non-soluble ceramic particles in a metallic matrix can enhance the strength and heat resistance of materials. With the advent of mechanical alloying it became possible to put the theoretical concept into practice by incorporating very fine particles in a flirty uniform distribution into often oxidation- and corrosion- resistant metal matrices. e.g. superalloys. The present paper will give an overview about the mechanical alloying technique as a dry, high energy ball milling process for producing composite metal powders with a fine controlled microstructure. The common way is milling of a mixture of metallic and nonmetallic powders (e.g. oxides. carbides, nitrides, borides) in a high energy ball mill. The heavy mechanical deformation during milling causes also fracture of the ceramic particles to be distributed homogeneously by further milling. The mechanisms of the process are described. To obtain a homogeneous distribution of nano-sized dispersoids in a more ductile matrix (e.g. aluminium-or copper based alloys) a reaction milling is suitable. Dispersoid can be formed in a solid state reaction by introducing materials that react with the matrix either during milling or during a subsequent heat treatment. The pre-conditions for obtaining high quality materials, which require a homogeneous distribution of small dis-persoids, are: milling behaviour of the ductile phase (Al, Cu) will be improved by the additives (e.g. graphite), homogeneous introduction of the additives into the granules is possible and the additive reacts with the matrix or an alloying element to form hard particles that are inert with respect to the matrix also at elevated temperatures. The mechanism of the in-situ formation of dispersoids is described using copper-based alloys as an example. A comparison between the in-situ formation of dispersoids (TiC) in the copper matrix and the milling of Cu-TiC mixtures is given with respect to the microstructure and properties, obtained.

• Journal of Powder Materials
• /
• v.4 no.1
• /
• pp.42-47
• /
• 1997

It was investigated whether mechanical alloying (MA) processing could be more effective to the formation of metallic composite powder in Cu-C system. Elemental powder mixtures of Cu-70vo1.%C were mechanically alloyed with an attritor in an argon atmosphere and microstructural evolution was examined by X-ray diffraction analysis, scanning electron microscopy and transmission electron microscopy. It has been found that even with the high volume fraction of immiscible graphite in Cu-C system, the refinement with a few ten nanometer size as well as the highly uniform distribution of copper phases have been achieved by the MA processing.

• Composites Research
• /
• v.31 no.2
• /
• pp.51-56
• /
• 2018

A new study was carried out to utilize a pencil drawing paper sensor (PDPS), which drew a line using a pencil on the paper, as a sensor. The sensing effect on 3 different papers based on the properties of PDPS was compared. The specimens were prepared by drawing 4B pencils on plain (A4), Hwasun, and Han papers. The silver paste was used to give good electrical contacts of the copper wires and the pencil drawn line. The chemical structures of 3 papers for PDPS by FT-IR spectrum analysis were similar and the comparative compact states of each paper were observed by optical microscope. From statistical evaluation of tensile strength using 3 papers, plain paper was chosen to be best for the PDPD. The optimum drawing number of PDPD was determined by changing the thickness of the paper with the drawing number. Electrical resistance (ER) with graphite on 3 different papers were compared. The changes in compression was observed through cyclic compressive test of composite materials, it was possible to predict the degree of strain sensing under compressive test. It leads to expectation of properties.