Surface organic modification of Fe_3O_4 nanoparticles by silane-coupling agents

Fe3O4 nanoparticles were prepared by chemistry co-precipitation and the mean crystal size was 17.9 nm measured by XRD. After it had been treated by silane-coupling agents KH570, magnetic micro-spheres dispersed in organic medium glycol were gained and the mean size of Fe3O4 nanopowders was 33.7 nm. So it can be concluded that magnetic micro-sphere is made of a few Fe3O4 crystals. Many factors of modification were researched, such as the time of ball milling, the content of Fe3O4 and the content of KH570. The modification of Fe3O4 is relative to the time of ball milling, but the dominant function is affected by the content of Fe3O4 and KH570. When the content of Fe3O4 is known, there is a suitable content of KH570. Different content of Fe3O4 will make the different suitable content of KH570, but the range of latter is less than former, which is relative to the distribution of KH570 on Fe3O4 surface or in the solution.

Development and road performance of clear asphalt with high transparency and adhesion

Clear asphalt(CA)currently used in light-colored asphalt mixtures(LCAM)exhibits poor transparency and adhesion.Therefore,a highly transparent CA(HCA)modified using a silane coupling agent(KH550)was prepared.Furthermore,LCAM was prepared by mixing CA and limestone aggregates.The properties of the HCA and ordinary CA(OCA)were characterized using conventional asphalt tests,optical tests,pull-off tests,ultraviolet aging tests,dynamic shear rheometry,Fourier-transform infrared spectroscopy,differential scanning calorimetry,and scanning electron microscopy.Whereas Marshall,moisture resistance,wheel tracking,trabecular bending,and British pendulum tests were employed for the LCAM.The transmittance and spectral reflectance of the HCA were 123.30 and 3.74 times greater than those of the OCA,respectively.The complex modulus and viscosity-aging index of the HCA were 48%and 53%less than those of the OCA,respectively.After modification with KH550,the Marshall stability ratio,tensile strength ratio,and flexural strain of the HCA-prepared LCAM increased by 12.92%,25.06%,and 23.90%,respectively.However,the rutting resistance of the HCA-prepared LCAM was 14.3%less than that of the OCA-prepared LCAM.The comprehensive performances of the HCA and HCA-prepared LCAM were 49.2%and 10.3%greater than those of the OCA and OCA-prepared LCAM,respectively,indicating a high application value in the future.

Wear Behavior of PTFE–Hydroxyapatite Composite Fabricated by Hot-Press Sintering Process

In the present work, a new biocompatible composite was fabricated by hot-press sinter-bonding of polytet- rafluoroethylene （PTFE）-hydroxyapatite composite. Furthermore, the wear properties of this composite were studied by computer-controlled pin-on-disk type tribometer in reporting volume loss per distance. The investigation was performed in three different fractions of hydroxyapatite （10, 20 and 30 wt%）. In order to improve the bonding between hydroxyapatite and PTFE, and thus to increase the wear properties of the composite, the effect of adding silane-coupling agent was investigated. Furthermore, to simulate the environment of human body, some of the wear tests were carried out in the ringer＇s solution. It was found that the wear resistance is improved at high load. Moreover, an optimum fraction of hydroxyapatite （20 wt%） was found in which the best wear resistance is achieved, especially at dry sliding condition. At last, the roles of the factors such as wear load, ringer＇s solution, and silane-coupling agent are described with respect to their influences on the Lancaster wear coefficient.