A. Al-Hajry

X-RAY AND NEUTRON DIFFRACTION STUDIES OF THE AMORPHOUS ZrPd ALLOYS

X-ray and neutron diffraction measurements have been made on amorphous ZrPd samples prepared by three different techniques, fast quenching (FQ) from the melt, mechanical alloying (MA) and mechanical milling (MM). An important feature of our samples is the small differences between the weighting factors for the partial structure factors (PSFs) and the pair density functions for both X-ray and neutron radiations. This was exploited to investigate the effect of the preparation method on the final structure of these samples. The results showed that the structure factors S(Q) and the reduced radial distribution functions G(r) of these samples prepared by different methods are similar and independent of the way used for producing them.

Fast amorphization reaction in ZrNi system prepared by mechanical alloying

The amorphous phase of ZrNi system was obtained by mechanical alloying (MA) of elemental crystalline powders in an inert atmosphere. The time required to achieve the amorphous state was 5 h. In contrast with all previous reports on this system, this amorphization time is considerably shorter. X-ray diffraction and differential scanning calorimetry (DSC) measurements were used to assess the amorphous state. Moreover, the comparison of the ZrNi alloy produced by MA with another prepared by fast quenching (FQ) confirmed that the final structure of the MA sample is fully amorphous. The reduced radial distribution function G(r) obtained by a Fourier transform of the structure factor S(Q) showed that a single amorphous phase formed at the end of the amorphization reaction. Further MA results in the recrystallization of the ZrNi alloy. Recrystallization takes place at a milling time even shorter than any reported milling time to obtain an amorphous phase in this system.

Complex nanostructures of ZnO: growth and properties

Variety of complex ZnO nanostructures such as flower-shaped structures, hierarchical and star-shaped nanostructures have been grown by the novel cyclic feeding chemical vapour deposition (CFCVD) process on various substrates at low-temperatures of 475°C to 550°C. Metal organic source, diethyl zinc (DEZn) and oxygen gas was used as source materials for zinc and oxygen, respectively for the growth of ZnO nanostructures synthesised by CFCVD process. The selected area electron diffraction (SAED) pattern of the flower-shaped structures confirmed that the grown products are single-crystalline ZnO. In addition to the ZnO nanostructures grown CFCVD process, comb-like ZnO structures were also synthesised, in a high density, via simple thermal evaporation process by using metallic zinc powder and oxygen as source materials for zinc and oxygen, respectively. The X-ray diffraction pattern of the synthesised comb-like structures exhibited that these structures are possessing single-crystallinity and wurtzite hexagonal phase of ZnO.

Differential Scanning Calorimetry Study of Ordinary Portland Cements Mixed with fly Ash and Slag

The study of the thermal behavior (DSC) of hydration products in ordinary Portland cement (OPC), as a function of water cement ratios (W/C) (0.2, 0.25, … 0.4), and the partial substitution of (35 % fly ash), (35 % slag) and (35 % fly ash + 35 % slag) to the OPC system by weight separately was carried out. It was found that the additive materials (pozzlans) increase its durability when added to the OPC. The most important effects in the cement paste microstructure are the changes in pore structure produced by the reduction in the grain size caused by the pozzlanic reactions. The study revealed that the changes in all the thermal parameters depend on the variation of W/C ratios.The systematic changes in the activation energy through all systems occur at (0.3) W/C in the phase (C‐H) and (0.35) W/C in the phase (C‐S‐H). This means that at these ratios of W/C the two phases (C‐H) and (C‐S‐H) further accelerated the process of cement hydration reactions, and at the same time the addition to OPC system may provi...