Organometal trihalide perovskite solar cells (PSCs) have sparked a frantic excitement in the scientific community because they can achieve high power conversion efficiencies (PCEs) even when fabricated by low-cost solution-processing technologies. However, the poor stability of PSCs has seriously hindered their commercialization. Among various kinds of PSCs, carbon-based PSCs without hole transport materials (C-PSCs) seem to be the most promising for addressing the stability issue because carbon materials are stable, inert to ion migration, and inherently water-resistant. Concurrent with the steady rise in PCE of C-PSCs, great progresses have also been attained on the device stability and scaling-up fabrication of C-PSCs, which have well signified the possible commercialization of PSCs in the near future. In this review, we will summarize these progresses with a view of exposing the promising prospect. We start by collating recent stability testing results of C-PSCs with reference to those of HTM-PSCs. Then, we update the research status on large-scale C-PSCs and their associated scalable fabrication technologies. Finally, we identify main issues to be addressed alongside future research directions.

MoS2(1−x)Te2x thin films were fabricated by high-temperature co-sputtering deposition and post-deposition tellurization annealing using novel Te precursor (i-C3H7)2Te for the first time. As a result, high crystal quality MoS2(1−x)Te2x (6.5 nm) were successfully fabricated with the Te concentration x ranging from 0.48 to 0.61 and band gap value from 0.80 to 0.87 eV. From the obtained band gap values of MoS2(1−x)Te2x , the bowing parameter b was determined to be 1.06 eV. When exploited in device use, if the required band gap value is known, the required composition can be calculated with the bowing parameter. We have also shown the compatibility of co-sputtering to alloy fabrication since the composition ratio can be easily controlled just by adjusting the radio frequency (RF) sputter power on different targets. The fabrication method can be applied to different transition metal dichalcogenide materials as well.

The Cu–S compounds have been reported as promising thermoelectric materials with abundant element composition, low price, and low toxicity. In this work, Sn x Cu1.8−x S samples with different Sn contents (x = 0.005, 0.01, 0.03, and 0.05) were fabricated by mechanical alloying combined with spark plasma sintering. The phase structure and microstructure of all the bulk samples were checked by X-ray diffraction (XRD) and field emission scanning electron microscopy respectively. The thermoelectric transport properties, such as electrical conductivity, Seebeck coefficient, carrier concentration, carrier mobility, and thermal conductivity, were measured. The effect of second phase introduced by Sn addition on the thermoelectric properties of Cu–S system was investigated. The thermoelectric properties of samples were improved by the precipitations of two different second phases (Cu2SnS3 and Cu4SnS4). The second phase species depend on the Sn contents. Finally, the Sn0.01Cu1.79S bulk sample obtained the highest ZT value of 0.81 at 773 K, which is 1.6-fold higher than that of the pristine Cu1.8S sample due to the significantly reduced thermal conductivity by second phase and nanopores scattering.

Mesoporous silicon sponge (MSS) is considered as a promising anode material for lithium ion batteries because of its preformed meso/macro porous structures that can accommodate large volume expansion during the lithiation process and its superior electrochemical performance. Temperature dependent hyperpolarized (HP) 129Xe NMR was applied to characterize the structure and porosity of MSS materials with varying pores and particle sizes. Our results reveal irregular pore structures with the presence of micropores inside the larger meso/macropore channels and each MSS material has its own characteristic pore environment with a varying degree of nonuniformity and connectivity of pores. This study demonstrates that HP 129Xe NMR is a potentially useful tool for providing a fingerprint of the structure and connectivity of the pores for each material, complementary to other characterization techniques.

Sheets made of 316 stainless steel (100 × 100 × 1 mm3) were irradiated by laser at 1, 5, 10, and 15 passes under natural and forced cooling. Results showed that the deflection angle increased with the number of radiation passes. The bending angle after 15 passes of exposure under forced cooling was 5° higher than under natural cooling. The grain size under natural cooling increased from approximately 23–35 μm. By contrast, under forced cooling, the grain size decreased from approximately 37–27 μm. The sample hardness declined under natural cooling from approximately 212–200 HV. By contrast, sample hardness increased from approximately 216–233 HV under forced cooling. Polarization results show that the breakdown potential versus the number of lasing passes increased from −0.14 to −0.08 V under natural cooling and −0.16 to −0.06 V under forced cooling.

The present study addressed the weldability of Hastelloy C-276 and Type 321 austenitic stainless steel (ASS) dissimilar combination used for manufacturing of high-temperature equipments in nuclear power plants. Investigation of the microstructural evolutions across the different welding passes and their subsequent effect on the mechanical properties and corrosion resistance would be helpful in better understanding and pave way for the frequent application of such dissimilar joints in the industrial applications. The problem of segregation associated with the multi-pass gas tungsten arc welding process was also investigated systematically. The fusion zone microstructures exhibited a transition from columnar to an equiaxed dendritic structure with varying passes. The topologically closed packed (TCP) phases (such as P and μ) were observed in the fusion zone as well as at the weld interface of Hastelloy C-276. Polarization test was performed to evaluate the corrosion resistance and results indicated that the Cr and Mo depleted zones formed around the TCP phases might be responsible for decreased Epit value for fusion zone. The novelty of this work is to explore the possibilities of substitution of an expensive Hastelloy C-276 with a cost-effective Ti-stabilized Type 321 ASS.

In this work, examination of joint properties of ferritic and dual-phase stainless steel dissimilar welds was carried out by using E2209 duplex and E309LMo austenitic electrodes. The results of E2209 weld showed dual-phase microstructure of ferrite and austenite in the form of grain boundary austenite, Widmanstatten and intragranular austenite, whereas E309LMo weld showed acicular ferrite in the cores of subgrain of austenite. Electron backscatter diffraction was used to study the evolution of the microstructure and micro-texture. The significant variations in the feature of weldments illustrated the presence of a very strong texture. Ferritoscope measurement revealed higher ferrite content in the E2209 weld. Tensile strength, hardness, and absorbed energy of weld metal were dominated by E2209 weld. The modified Strauss test indicated intergranular corrosion attack in the AISI 430 ferritic side heat affected zone. Higher pitting resistance showed by E2209 weld than E309LMo weld. While higher galvanic corrosion observed in the E309LMo weld and AISI 430 ferritic base metal couple.

The solidification microstructure, types of eutectic borocarbides, heat treatment properties and wear resistance of steel with x wt% B–0.4 wt% C–6.0 wt% Cr–4.0 wt% Mo–1.0 wt% Al–1.0 wt% Si–1.0 wt% V–0.5 wt% Mn (x = 1.0, 2.0, 3.0) have been investigated in this present study. The results indicate that the as-cast Fe–B–C alloy steel consists of pearlite, ferrite, and borocarbides M2(B,C) (M = Fe, Cr, Mo, V, Mn). After quenching or quenching and tempering treatment, ferrite and pearlite transform into martensite. With the increase of boron content, the macrohardness of alloys increases obviously while wear loss decreases. Borocarbides with chromium addition have good toughness and no cracks are observed on worn surfaces. The wear mechanism changes from micro-cutting accompanied with the spalling of borocarbides to single micro-cutting with the boron content rising.

For Sn–Pb eutectic solder alloy, uniaxial tensile tests were conducted to dog-bone type specimens annealed at different temperatures (60–180 °C) and durations (2–48 h). Low strain rates ranging from 10−4 s−1 to 10−3 s−1 were applied to study the competition between creep and plasticity and also the rate dependent effect of annealing condition. It is found that the influence of annealing temperature on material properties is more than that of annealing duration. Higher temperature up to 180 °C generally leads to higher yield and ultimate stresses and ultimate strain of annealed specimens. The optimal annealing condition is suggested to be 180 °C for 6 h for stable and efficient improvements in both strength and ductility. By proposing a concise unified creep and plasticity constitutive model, the sensitivity to strain rate and annealing condition is quantified with consideration of both creep and hardening properties. Parameter calibration theoretically confirms the observed optimal annealing condition in experiments.

Shape memory alloys (SMAs) are unique class of smart materials with excellent physical, mechanical and biomedical properties, which have wide applications in several fields such as aerospace, robotics, biomedical, and dental etc. These alloys are well known for exhibiting shape memory effect (SME) and pseudoelasticity (PE), it is a well-established fact that they are required to be processed into functioning parts. The conventional machining affects the internal properties of shape memory alloys and hence, it is reported that nonconventional machining techniques are more suitable. Wire electro discharge machining (WEDM) is one of the nonconventional machining processes for machining complicated shapes without hampering the internal properties of such type of materials. In the present experimental investigation, wire electro discharge machining of Ti50Ni40Co10 shape memory alloy (SMA) has been carried out and machining performances such as surface roughness (SR), and material removal rate (MRR) have been evaluated. Experimental results exposed that pulse on time, pulse off time and servo voltages are most influential process parameters on the responses. The machined surface has been characterised with respect to microstructure, microhardness, and phases formed.

To determine the spray forming process parameters of 7075/Al–Si bimetallic gradient composite plate with two gas atomizers, a calculation model of the plate has been established by using the finite element software ANSYS. The effects of different motion trajectory, advance speed, swing cycle and spray center distance on shape, and silicon distribution of deposited plate have been simulated by the APDL programming language. The results show that a smooth and uniform surface is obtained when motion trajectory is in a regular jaggies mode. The deposited plate varies from platform to stepped shape with a center distance increasing from 20 mm to 50 mm; meanwhile, the width of the transition zone decreases gradually. As the period increases to 8 s, the silicon distribution of each layer presents a jagged fluctuation. Both the thickness of the deposited plate and the width of the transition zone decrease as the advance speed increases, except the silicon distribution. Finally, the modeling and simulation of the co-spray formed 7075/Al–Si bimetallic gradient composite plate are validated by experimental investigations and the simulation results are in good agreement with the actual results.

The impact toughness and related microstructure of the dissimilar 9Cr/NiCrMoV welded joint fabricated by narrow-gap submerged arc welding were systematically investigated in the paper. Results indicated that the fracture appearance transition temperature (50% FATT) for weld metal was −11 °C, while low and scattered absorbed energies determined by different crack growth paths for the heat affected zone of 9Cr were gained which could not satisfy the requirement of service. However, a dramatically enhanced impact toughness was obtained by optimizing the post-weld heat treatment (PWHT) process. Microstructure characterization revealed that the microstructure evolution from martensitic laths in the previous PWHT metals to a softer ferrite matrix with the supersaturated carbon precipitating from the matrix led to higher toughness in the optimized PWHT materials. In addition, the observation of the fracture morphology found that the fractography varied from brittle fracture to a fracture mode with both brittle and ductile fracture feature with the change of crack growth paths in 9Cr-HAZ.

By reflowing Cu/Sn/Ni ultrafine interconnects under a temperature gradient, a new transient liquid phase (TLP) bonding process was proposed for three-dimensional packaging applications. The evolution of the dominant (Cu,Ni)6Sn5 intermetallic compounds depends strongly on the temperature gradient. The essential cause of such dependence is attributed to the different amounts of Cu and Ni atomic fluxes being introduced into the liquid solder. Under the coupling effect of thermomigration and Cu–Ni cross-interaction, the total atomic flux of Cu and Ni is promoted. As a result, the growth of dense (Cu,Ni)6Sn5 is significantly accelerated and the formation of Cu3Sn is eliminated. The new TLP bonding process consumes only a limited amount of the Ni substrate, but much more from the Cu substrate. The mechanism for the new TLP bonding process is discussed and experimentally verified in this study.

With an aim to develop novel Cu–Zn alloys with high mechanical properties, in this study, Ni and Si elements were added to Cu–10Zn and Cu–20Zn alloys, and four kinds of Cu–Zn alloys were synthesized through gravity casting. The effect of the addition of Ni and Si on the microstructure and mechanical properties has been systematically investigated. Results revealed that the addition of Ni and Si not only refined the microstructure but also played significant roles to improve the mechanical properties of Cu–Zn alloys; δ-Ni2Si precipitates were formed in the Cu–20Zn–1.5Ni–0.34Si alloy, which obeyed a crystal orientation relationship of (001)Cu‖(001)δ and [110]Cu‖[100]δ. As compared with the Cu–20Zn alloy, the tensile strength of the studied Cu–20Zn–1.5Ni–0.34Si alloy was increased from 373.2 MPa to 776.4 MPa, and the yield strength increased from 242.1 MPa to 718.4 MPa. Operative strengthening mechanisms in the Cu–20Zn–1.5Ni–0.34Si alloy with different thermal-mechanical treatment states will be discussed in detail with the aim to draw a new strategy to develop high strength brass alloys.

The present investigation aims to explore the evolution of microstructure and mechanical properties in Zn–Cu–Ti alloys during severe hot-rolling deformation. Twin deformation and dynamic recrystallisation are two important deformation modes of Zn–Cu–Ti alloys during hot rolling at 300 °C. Twin deformation and dynamic recrystallisation (DRX) appear one after the other. They not only consume the deformation stored energy but also inhibit initiation and growth of cracks. The elongation rate of Zn–Cu–Ti alloys has a rising trend with the increase in hot-rolling deformation. It is mainly due to grain refinement caused by increasing the ratio of DRX and twin deformation. The tensile strength of Zn–Cu–Ti alloys is found to decrease with the increase in hot-rolling deformation. This is because the solid-solution strengthening effect of copper is weakened by more deformation-induced precipitation of ε phase (CuZn5). The solid-solution strengthening effect of copper plays an important role in the strengthening effect of Zn–Cu–Ti alloys.

This work investigates the relative contributions to strengthening from twinning, solid-solution, precipitation, and irradiation hardening mechanisms in sputtered Cu–W thin films irradiated to different doses. A nanograin solid solution strengthening mechanism with a linear compositional dependence is observed for the as-grown alloys and for the alloy samples irradiated to 0.5 dpa. Solid solution strengthening is the major strengthening mechanism for Cu99.5W0.5 at all irradiation doses. Irradiation induces precipitation in samples with W concentrations greater than or equal to 1% at doses above ≈0.5 dpa. The growth of 1–4 nm precipitates enhances the hardness of these alloys, and the degree of strengthening is determined by the interparticle spacing. While the alloys exhibit steady-state properties after a relatively low dose (≈1 dpa), the different time scales associated with detwinning and damage accumulation in pure Cu lead transients at higher doses (>5 dpa).

A systematic analysis of the correlation between the valence electrons and the transformation temperatures of Ti–Ni-based shape memory alloys has been carried out by Zarinjad and Liu. They have shown that the valence electron theory can be successfully applied to estimate these temperatures, although the mechanisms of the temperature shift during alloying remains not completely understood. Other important shape memory alloy systems with technological importance are the Cu–Al based, which deserve a thorough analysis concerning the composition influence on the transformation temperatures and the valence electron theory. In this paper, the valence electron concentration, valence electron density (VED), enthalpy of reaction, and crystallographic compatibility were analyzed to understand the mechanisms, which control the transformation temperatures of Cu–Al-based alloys. It was observed that the larger the VED, the more energy is used in the transformation. The same tendency is present when the crystallographic compatibility is smaller. These results show that the valence electron theory based on the VED plays an important role in the prediction of the temperature transformation and the energies involved in the reaction.

The purpose of this work is, based on CAFE method, to study the microstructure evolution and optimize the quality of the large-scale titanium slab ingot during EBCHM. The nucleation parameters of the microstructure simulation of titanium ingot are determined based on one of the actual experimental results. For the determined parameters, our theoretical results are agreement with other experimental results. The effects of pouring temperature and pulling speed on the microstructure are presented based on CAFE method. The quantitative analyses of the simulated results show that with the pulling speed increasing, the number of grains decreases, whereas the mean grain radius increases under identical thermal condition; with the pouring temperature increasing, the mean grain radius increases under the given pulling speed. Our results are very important to obtain the optimal structure of the ingots by controlling pulling speed and pouring temperature.

The ground state properties of the α′ and α″ martensitic phases and energetic pathways of the β → α′/α″ martensitic transformations in Ti–(0–30 at.%)V alloys were investigated by first-principles method in combination with virtual crystal approximation. The results show that lattice parameters with c/a of the α′ phase and lattice parameters with b/a, c/a of the α″ phase are significantly sensitive to composition, and the atomic shuffle y of the α″ phase decreases from that of the α′ phase toward that of the β phase with increasing V content in Ti–V alloys. The compositional α′/α″ phase boundary is about 10 at.% V, from the viewpoints of energetics and mechanical stability of these phases. The principal lattice strains of the β → α′ transformation are insensitive to the V content, while those of the β → α″ transformation change significantly with increasing V content. The volume variation for β → α′ increases, whereas that for β → α″ decreases with increasing V content in Ti–V alloys. The energetic pathway results show that the relative stability of the α′ and α″ phases decrease with increasing V content and temperature and that there is no energy barriers during the β → α′/α″ martensitic transformations at temperatures from 0 to 400 K.

Mg–3.0Y–2.5Nd–1.0Gd–xZn–0.5Zr (x = 0, 0.2, 0.5, and 1.0) (wt%) alloys were produced by metallic and sand mold casting to study the microstructure and mechanical properties of the alloys. The as-cast Zn-free alloys consist of α-Mg and eutectics, whereas the Zn-containing alloys contain additional long-period stacking ordered (LPSO) structures. With a higher solidification, the cooling rate brought by metallic mold casting, grains, and eutectics are refined, which enhances the elongation of the alloys, accompanied by a decrease of area fraction of the LPSO structure. Some residual eutectics in the Mg–3.0Y–2.5Nd–1.0Gd–1.0Zn–0.5Zr alloys act as obstacles to grain boundary migration during solution treatment, which make the average grain size 15–20 μm smaller than that of the other alloys and hence improve the elongation of the alloys. The Zn addition brings notable enhancements to mechanical properties of the alloys due to solid solution strengthening of Zn. Especially, the peak-aged Mg–3.0Y–2.5Nd–1.0Gd–0.5Zn–0.5Zr alloys perform with the highest overall tensile properties.