With the development of micro/nano-technologies, microstructural scales or geometrical dimensions of metal conductors in the micro/nano-devices are becoming shrunk from macroscopic scale to micron scale, submicron scale and even nanometer scale, leading to the fact that the electrical resistivity of metal conductors at room temperature tends to exhibit evident size effects. Recent studies on the electrical resistivity of metal conductors at different length scales were reviewed in this paper, focusing on the effects of the geometrical scales of microscalematerials and of the scale of microstructures and defects in the materials as well as the relevant theoretical models. Finally the developing tendency of the investigations on the electrical resistivity of metal conductors and the service reliability of the microscale metals in the future are also addressed.

The effect of cooling rate during punching process on the microstructure and mechanical property of the 22MnB steel was investigated by three different processing conditions i.e. the processes with and without argon protection as well as a simulated industrial process. The results show that the cooling rates of all the hot punched parts with the three different processing conditions are higher than the critical cooling rate of 22MnB5 steel, thus the hot punched steels with a microstructure of lath martensite exhibit tensile stresses higher than 1500 MPa. When the temperature of hot punch tools is higher, an oxide scale appeared on the punched workpiece surface, thereby, the cooling rate and the mechanical property of the steel become lower, and the martensitic plate becomes thicker. The hot punched part with tensile strength about 1600 MPa and strength multiplied ductility c.a. 20, 000 MPa% was available by heating with argon protection while reducing the initial temperature of punch tools to ambient temperature. This is because the cooling rate of the punched part was high and thereby the martensite plates of the steel became fine for the process with protective gas.

The 1.3 mm thick plate of ODS high temperature alloy MGH956 was TIG welded with fillers containing different B₄C (0, 0.25 and 0.5 mass %), then the effect of B₄C content on the microstructure and mechanical properties of the weld joints was investigated. The results show that the microstructure of the weld metal with B₄C exhibits mainly equiaxed grains, which are fine and uniform, without significant agglomeration of oxide dispersoids, while the strengthening particulates of the alloy distribute in both grains and grain boundaries. The microstructure of weld joint was finer as the filler with B₄C content in a range from 0.25 to 0.5 mass%. However nearly almost the strengthening particulates of the alloy concentrate in the grain boundaries but disappear in the grains for the weld joints by filler with 0.5% B₄C. The tensile strength of the weld joints firstly increases and then decreases when the B₄C content of the fillers ranged from 0% to 0.5 mass%, but their toughness decreases with the induce of B₄C. The tensile strength of the weld joint with filler material containing 0.25% B₄C is the highest i.e. 630 MPa, reaching 87.5% of the parent material. The fractured surface exhibited characteristics of brittle fracture.

Glycine(Gly)was intercalated into Mg₃Al layered double hydroxides(Gly-Mg₃Al LDHs)by coprecipitation method. The delaminating of Gly-Mg₃Al LDHs in aqueous solution of pH=3~4 was realized by making use of the isoelectric point of Gly. Then Mg₃Al LDHs/montmorillonite layered composite was gained through inserting LDHs sheets into montmorillonite. The composite was characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), electrophoresis apparatus and N₂-adsorption/desorption measurements. The results show that the formed Gly-Mg₃Al LDHs possesses well-defined crystallographic structure. When the raw material ratio is 0.5 (n_Gly:n_NO3^-=1:2), the obtained Gly-Mg₃Al LDHs exhibits the best performance of delaminating, while the zeta potential of the subsequence colloidal particles is between 35mV and 40mV. Additionally, the translucent colloidal solution may be kept stably for 72h.The interlayer space of the layered composite is 1.44 nm, which is the total thickness of LDHs sheet and montmorillonite sheet. The results prove that LDHs sheets and montmorillonite sheets are layer by layer staggered.

Nanocomposites of poly(trimethylene-terephthalate)/poly(acrylonitrile-styrene-acrylate)/organic montmorillonite (PTT/ASA/OMMT) were prepared by means of melt-blending intercalation. The effect of OMMT contents on the phase morphology, crystallization behavior, rheological- and mechanical-properties were investigated. The results show that the size of dispersed phases decreases with increasing OMMT content. The crystallization peak shifts to high temperature and melting peak moves to low temperature owing to the heterogeneous nucleation of OMMT. The exfoliated OMMT is located in the PTT matrix and at interface of PTT/ASA phases The rheological measurements show that the elastic modulus and complex viscosity increase with increasing OMMT content. The interfacial modulus and interfacial layer thickness predicted by Palierne and Gramspacher-Meissner models are enhanced by introduction of OMMT. The tensile strength and notched impact strength of blends increase with increasing OMMT content.

The mesoporous material MCM-41 was modified by DOPO in order to improve its effectiveness as a synergist agent for fire retardant composite. Ammonium polyphosphate (APP)-pentaerythritol (PER)-melamine (MEL) as flame retardants and modified MCM-41 as synergist agent were used to fabricate intumescent flame retardant (IFR)-polypropylene (PP). The synergist effect of modified MCM-41 and IFR on flame retardancy, mechanical property and thermal property of composite PP were investigated. It was found that 1% (mass fraction) modified MCM-41 could obviously improve the flame retardancy of the composite PP with a high LOI value 32.6, which is around 91.76 % higher than that of pure PP. Results of TGA, DMA and SEM showed that MCM-41 could catalyze esterification reaction between IFR, increase the char residue and form much denser char-layer to improve the retardant performance of the materials.

Sisal fiber cellulose microcrystallines (SFCM) was coated with a fully renewable flame-retardant coatings consisted of cationic chitosan (CH) and anionic phytic acid (PA) via layer-by-layer (LbL) assembly. The structure and properties of the formed microcrystallite composite were characterized by Zeta potential, TGA, FESEM, VFT, and MCC methods. Zeta potential and FESEM results show that the surface charge of the coated cellulose microcrystallites reversed due to the adsorption of polyelectrolyte during multilayer deposition process. TG analysis show that the initial decomposition temperature of the composites decreased from 299℃ to 257℃ and the residues increased from 5.41% up to 37.34% with the increase of CH/PA film layers. Examination of SFCM(CH/PA)₅ residues by FESEM revealed that the distinct fiber structure have been preserved and insignificant fiber shrinkage was observed.Vertical combustion testing (VFT)results show that for SFCM(CH/PA)_{5 ,} in comparison with the plain SFCM, the afterflame time is drops from 150 s down to 39 s; the pkHRR and total heat release (HR)exhibit great reduction of 70.6% and 79.2% respectively. These results demonstrate that the CH/PA coating has obviously improved the flame retardant performance of SFCM.

A hypoeutectic Zn-4.45 mass%Al alloy was molten and then slowly solidified in an electrical furnace. The microstructure and the relevant crystallographic feature on longitudinal section of the solidified alloy ingot were characterized by means of SEM with EBSD technique. The results show that feather-like structure consisted of some elongated eutectic colonies is developed in the upper part of the specimen and a specific crystallographic orientation relationship (OR) () exists between β and αin the eutectic colonies. Moreover, the primary β dendrites are segregated in the lower part of the specimen with a flat morphology: six primary arms grow quickly along but slowly along <0001>. In addition, some αprecipitates are present in the interior of primary β dendrites, and there exists certain OR between β and α as that mentioned above. However, no specific OR is found between the primary β dendrites and their attached pseudo-primary αphase as well as between the adjacent eutectic β and α.

Molecular dynamics simulation was applied to investigate the binding energy of NBCA on HA crystallographic planes (001), (100) and (110), and then the mechanical properties and radial distribution function of the HA(110)/NBCA mixed system were calculated and analyzed. The results show that HA (110) has the highest binding energy with NBCA because of its higher planar atom density than that of HA (001) and (100). The mechanical properties of HA(110)/NBCA mixed system is weaker than one-component HA system. However, the NBCA contains 40 monomers, its mechanical properties completely meet the requirements for the artificial bone scaffold. By calculating the radial distribution function of HA(110)/NBCA, the essence of its interface interaction were elucidated. There is a strong interaction between HA crystallographic plane (110) and NBCA, it mainly derives from the hydrogen bonds between O atoms which connect with C atoms of NBCA and H atoms in HA crystal, and a strong adsorption effect can be demonstrated between HA and NBCA.

The ambient-temperature stable nanosized ZrO₂ particles with different crystallographic structures were prepared by codeposition method. Their crystallographic structures, grain size, specific surface area and size distribution were characterized by powder X-ray diffraction (XRD), laser raman spectroscopy, N₂ physical adsorption, transmission electron microscopy (TEM) and dynamic light scattering (DLS) respectively. Therewith the effect of preparation temperature and modifier doping on the crystallographic structures of particles was investigated. The results show that the nanosized ZrO₂ powders without Y₂O₃ doping calcined at 850℃ are monoclinic ZrO₂ with an average grain size 51.3 nm and a specific surface area 35.17 m²/g; the powders doped with 4.5% Y₂O₃ (molar fraction) and calcined at 600℃ are tetragonal ZrO₂ with a specific surface area 39.01 m²/g and an average grain size 19.2 nm; the powders doped with 8.5% Y₂O₃ (molar fraction) and calcined at 600℃ are cubic ZrO₂ with a specific surface area 46.53 m²/g and an average grain size 12.7 nm.

High strain rate triaxial-forging (HSRTF) was successfully conducted on three Mg–Zn–Zr alloys by using a pneumatic power hammer. The microstructure evolution and mechanical properties of the forged alloys were investigated. The results show that HSRTF significantly refined the grains due to dynamic recrystallization (DRX). A novel microstructure was obtained, which was mixed by honeycombe-like coarse DRX grains and island-like ultrafine DRX grains. The two features of the mixed microstructure were caused by different DRX mechanisms, i.e., rotation DRX at the initial grain boundaries and twin-induced DRX in the interior of the initial grains. The mechanical properties were dramatically improved, resulting from the severe grain refinement and weakening of the basal texture due to HSRTF.For ZK21 and ZK60 alloys, after HSRTF with an accumulative strain ∑Δε=2.64, excellent tensile properties were achieved with an ultimate tensile strength, yield strength and elongation of 341.6 MPa, 270.7 MPa, 25.1% and 330.2 MPa, 232.3 MPa, 24.8%, respectively.

The Cu₂ZnSnS₄ (CZTS) nanocrystallites were synthesized by hot injection method with starting materials of copper (II) acetylacetonate [Cu (AcAc) ₂], zinc acetate [Zn(CH₃COO)₂2H₂O], tin(II) chloride dehydrate [SnCl₂2H₂O], elemental sulfur (S) and dodecanethiol. Then CZTS thin films were prepared by spin coating method. The crystallographic structure, morphology, chemical composition and optical properties of CZTS nanocrystallites and their thin films were characterized by X-ray diffraction (XRD), Raman spectrum (RS), transmission electron microscopy (TEM), scanning electron microscope (SEM) with energy dispersive X-Ray spectroscopy (EDS) and UV-Vis transmittance spectroscopy. The influence of injection temperature on the crystallographic structure, morphology, grain size and chemical composition of CZTS nanocrystallites, and the influence of annealing time on the crystallographic, morphology, chemical composition and optical properties of CZTS thin films were investigated respectively. The results show that the CZTS nanocrystallites synthesized at 180 ℃ were consisted of single phase kesterite with an average grain size 18 nm, while the CZTS thin film after annealing at 500℃ for 2h exhibits an absorption coefficient of 10⁴ cm^-1 for the visible light and an optical band gap of 1.45 eV.