Iraqi Journal of Physics

In this work, some mechanical properties of the polymer
coating were improved by preparing a hybrid system containing
Graphene (GR) of different weight percentages (0.25, 0.5, 1, and
2wt%) with 5wt% carbon fibres (CF) and added to a polymer coating
by using casting method. The properties were improved as GR was
added with further improvement on adding 5wt% of CF. The impact
strength of acrylic polymer with GR increases with increasing weight
ratio of GR; maximum value was obtained when the polymer coating
was incorporated with 1wt% GR and 5wt% CF. The impact strength
of acrylic polymer with GR and GR/CF composites incorporated
with GR at 1wt% and CF at 5wt%. Hardness increase with increasing
weight ratio of Gr and a significant improvement was observed at
1wt% GR and 5wt% CF content. The tensile strength increases more
significantly than the acrylic polymer with GR and GR/CF
composites incorporated with GR at 1wt% and CF at 5wt%. Pull-off
strength for the polymer coating with GR and CF was greater than
for the acrylic polymer coating.

Crystalline silicon (c-Si) has low optical absorption due to its
high surface reflection of incident light. Nanotexturing of c-Si which
produces black silicon (b-Si) offers a promising solution. In this
work, effect of H2O2 concentrations towards surface morphological
and optical properties of b-Si fabricated by two-step silver-assisted
wet chemical etching (Ag-based two-step MACE) for potential
photovoltaic (PV) applications is presented. The method involves a
30 s deposition of silver nanoparticles (Ag NPs) in an aqueous
solution of AgNO3:HF (5:6) and an optimized etching in HF:H2O2:DI
H2O solution under 0.62 M, 1.85 M, 2.47 M, and 3.7 M
concentrations of H2O2 at 5 M HF. On the b-Si, nanowires with 250-
950 nm heights and an average diameter of 150-280 nm are obtained.
Low concentrations of H2O2 result in denser nanowires with an
average length of 900-950 nm and diameters of about 150-190 nm.
The b-Si exhibit outstanding broadband antireflection due to the
refractive index grading effect represented as WAR within the 300-
1100 nm wavelength region. B-Si obtained after etching in a solution
with 0.62 M concentration of H2O2, demonstrate WAR of 7.5%.
WAR of 7.5% results in an absorption of up to 95.5 % at a
wavelength of 600 nm. The enhanced broadband light absorption
yields maximum potential short-circuit current density (Jsc(max)) of up
to 38.2 mA/cm2, or 45.2% enhancement compared to the planar c-Si
reference.

In this research, the effect of reinforcing epoxy resin
composites with a filler derived from chopped agriculture waste from
oil palm (OP). Epoxy/OP composites were formed by dispersing (1,
3, 5, and 10 wt%) OP filler using a high-speed mechanical stirrer
utilizing a hand lay-up method. The effect of adding zinc oxide
(ZnO) nanoparticles, with an average size of 10-30 nm, with different
wt% (1,2,3, and 5wt%) to the epoxy/oil palm composite, on the
behavior of an epoxy/oil palm composite was studied with different
ratios (1,2,3, and 5wt%) and an average size of 10-30 nm. Fourier
Transform Infrared (FTIR) spectrometry and mechanical properties
(tensile, impact, hardness, and wear rate) were used to examine the
composites. The FTIR results show a strong interaction between ZnO
and oil palm fiber and epoxy resin. Tensile strength was reduced
from 22.78 MPa to 19.03 MPa for the epoxy/OP composite as the
wt% of OP was increased but increased to 29.224MPa for epoxy /oil
palm / 5% ZnO samples. Young modulus increased from 1.9 MPa to
4.3 MPa while elongation decreased (9.6 to 6.8 %) with the increase
of wt% OP and ZnO. The impact and hardness increased for all
composites between (6.94 - 10.8 KJ/m2) and between (80.8- 84.55
KJ/m2) respectively. Also, wear resistance of the epoxy/OP and
epoxy/OP/ZnO samples increased with the increase of wt% OP and
ZnO. This studied in order to provide a new step in the utilization of
green nanoparticle fillers for sustainable and renewable structural
products for biodegradability.

In this study lattice parameters, band structure, and optical
characteristics of pure and V-doped ZnO are examined by employing
(USP) and (GGA) with the assistance of First-principles calculation
(FPC) derived from (DFT). The measurements are performed in the
supercell geometry that were optimized. GGA+U, the geometrical
structures of all models, are utilized to compute the amount of energy
after optimizing all parameters in the models. The volume of the
doped system grows as the content of the dopant V is increased. Pure
and V-doped ZnO are investigated for band structure and energy
bandgaps using the Monkhorst–Pack scheme's k-point sampling
techniques in the Brillouin zone (G-A-H-K-G-M-L-H). In the
presence of high V content, the bandgap energy decreases from 3.331
to 2.043 eV as seen by the band diagram. PDOS diagram was utilized
to get the insight of the electronic structure of the atoms and the
amount to which all energy bands contribute to a particular orbit of
the atoms. As the V content grew, so did the PDOS for all of the
states. The manipulation of bandgaps was carried out in a way that
narrowing the bandgaps occurs, resulting in a redshift of the
absorption spectrum in the IR region. At lower photon energies, the
imaginary and real parts dielectric functions have increased. The
effectiveness of V atoms on transmissivity especially in the low
energy region of the V-doped ZnO perovskite has been verified
compared to the other theoretical results.

Beryllium Zinc Oxide (BexZn1-xO) ternary nano thin films were
deposited using the pulsed laser deposition (PLD) technique under a
vacuum condition of 10-3 torr at room temperature on glass substrates
with different films thicknesses, (300, 600 and 900 nm). UV-Vis
spectra study found the optical band gap for Be0.2Zn0.8O to be (3.42,
3.51 and 3.65 eV) for the (300, 600 and 900nm) film thicknesses,
respectively which is larger than the value of zinc oxide ZnO
(3.36eV) and smaller than that of beryllium oxide BeO (10.6eV).
While the X-ray diffraction (XRD) pattern analysis of ZnO, BeO and
Be 0.2 Zn 0.8 O powder and nano-thin films indicated a hexagonal
polycrystalline wurtzite structure. The crystal structure showed a
preferential orientation line at (101). Besides the nano thin film
Be0.5Zn0.5O has all orientations of ZnO and BeO. Moreover, the
calculated average crystallite size for nano thin film was 16.48 nm.
The surface morphology of the nano thin films investigated by
atomic force microscope (AFM) showed a decrease in the average
grain sizes (94.8, 79.2 and 59.4 nm) with the increase of films
thickness due to quantum confinement effect.

Rainfall in Nigeria is highly dynamic and variable on a
temporal and spatial scale. This has taken a more pronounced
dimension due to climate change. In this study, Standard
Precipitation Index (SPI) and Mann-Kendall test statistical tools were
employed to analyze rainfall trends and patterns in Gombe
metropolis between 1990 and 2020 and the ARIMA model was used
for making the forecast for ten (10) years. Daily rainfall data of 31
years obtained from Nigerian Meteorological Agency, (NIMET) was
used for the study. The daily rainfall data was subjected to several
analyses. Standard precipitation index showed that alternation of wet
and dry period conditions had been witnessed in the study area. The
result obtained showed that there is an upward trend in the annual
rainfall amount received in Gombe over the last 31 years at a rate of
3.98 mm/year. The results for the forecast shows that the annual
rainfall to be received in Gombe continues in a range above the mean
which serves as an indication that the decade will experience more
wet years than dry years. The study concludes that the pattern of
rainfall in Gombe is a cyclic pattern. The current trend may affect
soil moisture, flooding and subsequently lead to ecological change.
The study recommends that inhabitants of the study areas should plan
their cropping season based on climatic information of their area.