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As a thermal interface material, thermal grease (TG) has been extensively applied to facilitate heat dissipation in electronic devices. Despite the superior thermal conductivity of diamond, researches on diamond-containing TGs remain rare. In this study, four kinds of TGs in which diamond served as essential filler were prepared and hot disk technique was applied to measure their thermal conductivity k(TG). After two unoverlapped particle sizes were selected, the volumetric filler content, terminal group, and viscosity of a polydimethylsiloxane (PDMS) matrix were modified in sequence. Based on the preferred recipe of a single-filler TG, two double-filler TG series were prepared by retaining the large diamonds and replacing the small ones by [Al.sub.2][O.sub.3] or ZnO, respectively. Depending on the content, it was found that diamond was not always the best choice for small filler. The highest k(TG), which was 23 times greater than the original k(PDMS), appeared in a ZnO-containing double-filler grease (=3.52 W/mK). The prediction for the maximum attainable thermal conductivity was preliminarily supported. [DOI: 10.1115/1.4003002] Keywords: hybrid (A), polymer-matrix composites (PMCs) (A), thermal properties (B), electron microscopy (D)

Chemical-vapor-deposited single-crystal diamonds for use in high voltage and high-temperature applications are described. These models provide an explanation for its different conduction, which is due to incomplete ionization of boron dopant, but the limited voltage handling capacity of the CVD is due to residual defects in the intrinsic voltage blocking layer in the structure.

The use of synthetic diamond for intracavity thermal management in compact solid-state lasers is examined. Findings reveal that the synthetic diamond samples possess significantly lower birefringence as compared to natural single-crystal diamond.

A continuously tunable semiconductor disk laser with intracavity second-harmonic generation (SHG) is evaluated using a wedged and antireflection-coated diamond heatspreader. Findings reveal output powers of more than 600 mW tunable over 10 nm around 530 nm.

An analysis of a fluid model is used to simply describe the phenomenon of microwave plasma discharge for the chemical vapor deposition of diamond with extremely reduced computational cost. The model gives a full description of the electron temperature, as well as the number density of the substance.

A molecular dynamics simulation is performed to study the effect of an applied force on heat transfer at the interface of model diamond {111} nanosurfaces. For the same interfacial force, different anharmonic models for the nanosurfaces' potential energy function give the same heat transfer rate constant.

Diamond nucleation was studied in relation to nanoscaled thermodynamics aiming at a clear insight into heterogeneous nucleation of CVD diamond. The nanothermodynamic analyses are expected to be a general approach to elucidate nucleation of diamond and related materials in low-temperatures and low-pressure gas phase.

The interaction of oxygen with a diamond (110)-oriented surface is investigated y using multiple internal reflection infrared spectroscopy (MIRIS) and temperature-programmed desorption (TPD). The observation implies that the low-temperature adsorption sites were etched away, thus favoring the additional adsorption of oxygen sites that are stable at high temperature.

The various effects of the gigaelectron volt Au-ion irradiation/postannealing processes on the electron field emission (EFE) and other characteristics of the ultrananocrsytalline diamond films are analyzed. These proceses are shown to lead to a significant enhancement in the EFE properties of the films.

The ultrahigh vacuum atomic force microscope (AFM) technique is employed for the characterization of the nterfacial friction for a single-asperity diamond contact on a diamondlike carbon (DLC) substrate over a nominal substrate temperature range. The dependence of the friction on the temperature of the system is also analyzed.

The hydrogen bonding, phase composition, the surface microstructure, and composition of diamond films consisting of 30-50 nm crystallites, deposited onto silicon substrates were explored to examine the impact of high temperature annealing up to 1200 degree [Celsius on the film. The results suggested that formation of SiC phase preferentially consumes [sp.sup.2]/sp hybridized carbon matrix, produced by thermal desorption of hydrogen atoms at diamond grain boundary and at the diamond film-silicon substrate interface.

The effect of temperature on the stability of the secondary electron emission (SEE) yield from continuous diamond films is examined. The studies have shown that the longevity of diamond films in practical applications of SEE can be enhanced by moderate heating.

Several studies are conducted to analyze the thermionic emission energy distributions (TEEDs) that take place from the various nanocrystalline diamond (NCD) films. The NCD films are shown to exhibit emission peaks, which make them feasible for numerous direct thermal-electrical energy conversion applications.

The characterization of the zero bias thermally stimulated currents (ZBTSC) observed in single crystal high pressure high temperature (HPHT) and polycrystalline chemical vapor deposited (pCVD) diamond films is reported. An explaination of the ZBTSC peaks in terms of defect discharge in the nonequilibrium potential distribution created by a nonuniform traps filling at the metal-diamond junctions is also presented.

An improved method is provided for determining the temperature in laser heated diamond anvil cells. Temperature determination is reduced to a one-parameter fit to the blackbody curve rather than the two parameters, which has led to increasing precision and accuracy.

Wavelength-matched vibrational excitations of ethylene ([C.sub.2][H.sub.4]) molecules using a tunable carbon dioxide (C[O.sub.2]) laser are used for enhancing the chemical vapor deposition (CVD) of diamond in open air using a precursor gas mixture of [C.sub.2][H.sub.4], acetylene ([C.sub.2][H.sub.2]), and oxygen ([O.sub.2]). The C[H.sub.2]-wag vibration mode of the [C.sub.2][H.sub.4] molecules is selected for achieving the resonant excitation in the CVD process and also the quality of the diamond crystals is enhanced.

Byline: Luming Shen, Zhen Chen The ability to predict the properties of material specimens with different sizes under various loading rates and temperatures is essential to evaluating the integrity and durability of NEMS/MEMS devices under extreme loading conditions. To better understand the rate, thermal and crystal orientation effects on size-dependent material responses, Molecular Dynamics (MD) simulations are performed with the use of Single Crystal Diamond (SCD) of various sizes under uniaxial tensile loading. In the MD simulations, the responses of SCD blocks of different sizes under and tensions at different loading rates and temperatures are studied. By combining the available experimental and simulation data, a hyper-surface is formulated to predict the combined size, rate and thermal effects on the strength of pristine diamond.

The bias enhanced nucleatin (BEN) technique is applied in a microwave plasma chemical vapor deposition setup to induce heteroepitaxial nucleatin and growth of twin-free diamond nucleation on the new multilayer stack Ir/YSZ/Si(111). The newly designed heteroepitaxial diamond films with (111) orientation provide interesting growth substrates for phosphorous doped diamond or the formation of heterojunction devices by deposition of wurtzite-type wide band gap semiconductor materials.

Theoretical analysis is performed on nanodiamonds (NDs) generated by pulsed-laser ablation to examine its growth dynamics. The results have shown that radius and density of plasma plume has determined the cooling velocity and the growth time have correlated with the cooling velocity.

The effect of high temperature annealing of hydrogenated diamond films with average grain size on surface degradation of graphitization is examined. UHV annealing of fully hydrogenated films have resulted in thermal hydrogen desorption and diamond phase degradation, which is associated with size effect where high energy surface atoms reduce the thermodynamic stability of nanocrystals.

The properties of nitrogen-doped nanodiamond films are analyzed as a function of deposition temperature ([T.sub.D]). The studies have shown that the high conductivity at high [T.sub.D] is because of the amount and crystallinity of [sp.sup.2] carbon, rather than the nitrogen concentration.

The resonant-ultrasound spectroscopy is used to measure diamond's monocrystal elastic-stiffness coefficients, [C.sub.11], [C.sub.12], and [C.sub.44], between 322 and 10 K. The measurement has stressed that diamond has followed the Grunseisen-Debye low-temperature bulk-modulus relationship up to 300 K.

The theoretical total energy and phonon calculations for diamond under strong compression up to 3 TPa are analyzed to obtain a simple optical phonon model. The comparison of thermophysical data at ambient pressure provides additional information on weak intrinsic anharmonic contributions and develop the frame for the complete modeling up to 3 TPa in pressure and temperatures up to the melting curve.

The effect of annealing in an ultrahigh vacuum on the chemical structure of diamondlike carbon (DLC) film is studied. The results obtained provide insight into the H-C bonds which produced large free spaces in the DLC structure and inhibited conductive routes and lead to high electrical resistivity.

The activation energy of the main trap involved in chemical vapor deposited (CVD) diamond is determined by both thermally stimulated conductivity (TSC) and initial rise thermally stimulated luminescence (TSL) measurements. Thermally stimulated conductivity phenomenon is not affected by thermal quenching and has determined the trap parameters than TSL measurements.

Characteristic parameters of Schottky diodes formed from a chemical-vapor-deposited diamond/[n.sup.+]-Si junction are obtained from the I-V characteristics over a wide temperature range. The temperature dependence of the parameters can be ascribed to surface states, series resistance and inhomogeneities in the material.

The thermal conductivity of nitrogenated ultrananocrystalline diamond (UNCD) films on silicon is examined. The results have helped in understanding the nature of thermal conduction in partially disordered nanostructured materials and can be used for estimating the thermal resistance of doped UNCD films.

A high-resolution transmission electron microscopy was used to observe the diamond particles with size of about 100 nm, embedded in a fullerenelike carbon matrix film fabricated at low substrate temperature of 300 degree Celsius. The formation of diamond particle is attributed to the hydrogen bonding assisted by thermally activated processes and the high local stresses.

A detailed study of the physics underlying the working principles of a compact solid-state neutron detector capable of simultaneously detecting thermal and fast neutrons is presented. The design of the detector is fabricated from chemical vapor deposition (CVD) single-crystal diamond films using a p-type/intrinsic/metal configuration.

The electrical conduction behavior of undoped ultrananocrystalline diamond (UNCD) and its dependence on deposition temperature and chemical structure are described. The studies have shown that the conduction is directly correlated with the [sp.sup.2] bond carbon density and the role of the hydrocarbon bonds in the conduction path is formed by the network of the [sp.sup.2] bonded carbon.

The incorporation of hydrogen and its bonding configuration in diamond films composed of diamond grains of varying size is analyzed. The hydrogen retention of the diamond films has increased with the decreasing grain size, which has indicated that hydrogen is bonded and trapped in grain boundaries as well as on the internal grain surfaces.

The dependence of interfacial conductance on twist angle is examined for (001) symmetric twist grain boundaries (GBs) in diamond. The Kapitza lengths are found to be longer in diamond than in Si, showing that the diamond GBs are worst conductors of heat.

The thermal conductivity of naturally abundant, isotopically enriched, fast neutron irradiated singe crystals of diamond, and chemical vapor deposited diamond films of different types is examined over a large temperature range. The results have shown that the N-drift term in Callaway's theory has contributed to the thermal conductivity of all forms of diamond.

A direct transformation of the g-BC1.6 phase to a diamond-like BC1.6 is observed in a diamond-anvil cell (DAC) at high temperature, 2230 plusmn 140 K, and high pressure, 45 GPa. This observation of the phase transition in the B-C system confirms theoretical prediction that incorporation of the B atoms into diamond structure should lead to negligible distortion of the cubic cell of diamondlike materials.

Axial and radial temperature gradients in the laser-heated diamond-anvil cell are examined using finite element simulations. The result demonstrates that reduction of axial temperature variations in optically thin laser-heated samples requires the use of thick, low thermal conductivity insulation media.

The mechanism of formation of diamond as well as the transformation of diamond to graphite and onionlike carbon upon heating is reported. The random nucleation of diamond from amorphous sp(super 3) bonded carbon produced as the result of extraction of Si from SiC shows that presence of hydrogen is not required for diamond synthesis.

The data on the fracture-strength for ultrananocrystalline diamond (UNCD) thin films throws valuable light on the strength performance of synthetic polycrystalline diamonds. Details of the Weibull statistical analysis that take into account the impact of the stressed area on measured stresses at fracture are discussed.