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Yield pseudoplastic paste is prepared for self-supported stereolithography (SLA) 3D printing with critical shear stress of 290.7 Pa and viscosity of 28810 mPa·s under strain rate of 30 s−1. Simulation analysis of paste coating is carried out based on established constitutive equation. Furthermore, corresponding stress field is analyzed under different layer thicknesses (25–100 μm) and blade speeds (1.5–4.5 mm/s). Then, flexural strength, porosity, surface roughness and microstructure of components, printed with different layer thicknesses and sintered at different temperatures, are systematically investigated. Finally, complex-shaped cores are fabricated with flexural strength of 38.56±1.45 MPa, porosity of 21.57±0.8% and surface roughness of R a < 3 μm. The optimized parameters include layer thickness of 25–50 μm, blade speed of 3.5 mm/s, and sintering temperature of 1300 oC. Moreover, step-like undulating fracture morphology of the core is observed along printing layer, which shows that the coating process has an important influence on the mechanical properties of ceramic parts. [ABSTRACT FROM AUTHOR]

Pure hydroxyapatite (HA) as bone graft substitute has excellent osteogenic activity, but it has lower fracture toughness and its biological activity is harmed by the addition of toughening phases, which limits its clinical application. To alleviate the contradiction, columnar β-Si 3 N 4 as the toughening phase and La3+/Y3+ sintering aid as active ions are used in this study to prepare β-Si 3 N 4 /HA composite biomaterials. According to the results, hardness and toughness of 10 wt% β-Si 3 N 4 /HA composite prepared by cold press sintering at 1300 °C were 6.44 GPa and 1.69 MPa m1/2, respectively, being 110% and 140% higher than those of pure HA. Moreover, 10 wt% β-Si 3 N 4 /HA composite exhibited better protein adsorption capacity and obviously stimulated adhesion, proliferation, and osteogenic differentiation of osteoblast. In addition, it was found that sintering aid not only facilitated the improvement of mechanical properties, but also promoted the formation of 100–200 nm nanostripe structure, which was beneficial to cell adhesion. Determination of La3+concentration combined with biological experiments also proved that its concentration range from 4×10−8 M to 6 × 10−8M was beneficial to cell proliferation and osteogenic differentiation. In summary, β-Si 3 N 4 and sintering aids were shown to improve mechanical properties of HA at maintaining the biological activity of the latter. [ABSTRACT FROM AUTHOR]

For multi-ceramic materials based on the stereolithography (SL) principle, a 3D printing strategy was developed, and then an Al 2 O 3 -Si 3 N 4 functionally graded material (FGM) ceramic part was fabricated using this strategy. Six groups of mixtures, with a Si 3 N 4 content gradient of 20 vol% and a certain bimodal particle size distribution, were prepared using UV-curable pastes. A modified formula was proposed to evaluate the relationship between the actual minimum voidage of mixtures and the viscosities of their corresponding pastes. The viscosity of each paste was controlled using the prediction formula and optimization of dispersants. To design theprinting layer thickness, a mathematical relationship was established between Si 3 N 4 content and curing depth of paste. The Al 2 O 3 -Si 3 N 4 green body without deformation was printed using optimized parameters such as a layer thickness of 40 μm and a paste viscosity of ∼13,000 mPa·s. Finally, using debinding and sintering, denseparts having a complicated shape were obtained. [ABSTRACT FROM AUTHOR]

Al 2 O 3 particles with different size (d 50 ~ 1 μm, 200 nm) and ZrO 2 (d 50 ~ 200 nm) were prepared to ZTA UV curable pastes with various bimodal PSDs. A modified Krieger-Dougherty formula was proposed to evaluate the relationship between the PSD and the viscosity. The 30 vol%-fine and 70 vol%-large mixed group owns the minimum porosity about 40.13%, contributing to the lowest viscosity. As ZrO 2 increasing to 20 vol%, the viscosities of pastes display an upward trend, but the curing depths (C d) display a downward trend. This phenomenon is due to the decrease of inter-particle spacing in ZTA paste and the enhancement of light scattering. Finally, ZTA paste containing 15 vol% ZrO 2 with bimodal PSDs was prepared with a viscosity < 30000 mPa s. The highest flexural strength, fracture toughness, hardness and relative density of fabricated ZTA ceramic can reach 575 ± 87 MPa, 7.4 ± 1.02 MPam1/2, 19.20 ± 0.89 GPa and up to 99.4%. Image 1 • UV curable ZTA paste is prepared for SL 3D-printing process. • A modified K-D formula is proposed for the bimodal PSDs paste. • Particles with bimodal PSDs contribute to the lower porosity. • Lower porosity of ceramic particles reduces the paste viscosity. • ZTA component is fabricated by a SL process and sintering. [ABSTRACT FROM AUTHOR]

The aim of this work is to develop a high solid loading suspension of Al 2 O 3 dispersed in an UV curable acrylic based resin, suitable for SLA-3D printing micro-components with complex shapes. Silane coupling agents KH550, KH560 and the stearic acid (SA) were investigated as the surfactants for Al 2 O 3 particles, and the low viscosity acrylic monomers ACMO, HDDA and NPG2PODA were used as the reactive diluents for Di-TMPTA-based premixed resins. The modified Al 2 O 3 powders exhibit the different wettability with premixed resins to cause the different rheology behaviors among the formulated suspensions. The KH560-modified Al 2 O 3 powders show the better wettability performance with NPG2PODA/Di-TMPTA-based solvents and their corresponding 75 wt% Al 2 O 3 suspensions (44.2 vol% solid loading) with a viscosity ˂ 25,000 mPa·s at 30 s −1 shear rate are successfully prepared. The further analyses approve that hydrophobic structures of KH560 molecules have been introduced on the surfaces of Al 2 O 3 powders. This consequence results in the lowest sediment rate and contact angle between the KH560-modified Al 2 O 3 powders and NPG2PODA/Di-TMPTA-based resins, which contributes to their better wettability performance. The optimum parameter of NPG2PODA concentration of prepared suspension is range from 50% to 70% in the premixed resin. Finally, Al 2 O 3 ceramic micro-component with 99.5% density was fabricated via an SLA process and subsequent sintering. Both the Al 2 O 3 suspensions and sintered micro-components exhibit good homogeneous microstructures, indicating an optimistic dispersal uniformity of KH560-modified Al 2 O 3 particles in the premixed resins. [ABSTRACT FROM AUTHOR]

Zirconia (ZrO 2 ) ceramic bars with three different printing sizes were fabricated by a stereolithographic (SLA) 3D-printing process and subsequent sintering. An anisotropic character of the ceramics surface quality was observed. The surface roughness of the horizontal surface was below 0.41 µm, whereas it reached 1.07 µm along the fabrication direction on the vertical surface. The warpage and flatness were utilized to measure the dimensional accuracy of the 3D printed ZrO 2 . Furthermore, it was evaluated that the warpage and flatness were below 40 µm and 27 µm, respectively, even if the printed size of ceramic bar reached 3 mm × 4 mm × 80 mm. In addition, the flexural strength, the fracture toughness, the hardness and the density of ZrO 2 ceramics can reach to 1154 ± 182 MPa, 6.37 ± 0.25 MPa m 1/2 , 13.90 ± 0.62 GPa and up to 99.3%, respectively. Moreover, the effects of scanning paths and printing size on properties of the sintered ZrO 2 samples were analyzed. The anisotropic character of surface quality was related to the various scanning paths. The warpage and flatness of 3D printed ZrO 2 bars were apparently affected by the various printed sizes. Also, the effects of special microstructure on the mechanical properties of sintered ZrO 2 samples were investigated. [ABSTRACT FROM AUTHOR]

Sintered Si 3 N 4 ceramics were prepared from an ɑ -Si 3 N 4 / β -Si 3 N 4 whiskers composite powder in-situ synthesized via carbothermal reduction at 1400–1550 °C in a nitrogen atmosphere from SiO 2 , C, Ni, and NaCl mixture. Reaction temperatures and holding time for the composite powder, and mechanical properties of sintered Si 3 N 4 were investigated. In the synthesized composite powder, the in-situ β -Si 3 N 4 whiskers displayed an aspect ratio of 20–40 and a diameter of 60–150 nm, which was mainly dependent on the synthesis temperature and holding time. The flexural strength, fracture toughness and hardness of the sintered Si 3 N 4 material reached 794±136 MPa, 8.60±1.33 MPa m 1/2 and 19.00±0.87 GPa, respectively. The in-situ synthesized β -Si 3 N 4 whiskers played a role in toughening and strengthening by whiskers pulling out and crack deflection. [ABSTRACT FROM AUTHOR]

[Display omitted] • Customized graphene oxide /hydroxyapatite ceramic scaffolds with precise porous structures were fabricated by digital light processing 3D printing. • Composite ceramics with 0.4 wt% GO exhibited the highest mechanical properties. • Graphene oxide can weaken the scattering effect of ceramic particles on ultraviolet light to maintain the pore shape unchanged. • The composite ceramic scaffold had significantly enhanced osteogenic induction on bone marrow mesenchymal stem cells. In the field of bone tissue engineering, porous hydroxyapatite (HA) bone repair scaffolds with controlled architecture and porosity are challenging to manufacture and lack sufficient osteoinductive activity, which limit its wider clinical application. This study fabricated porous graphene oxide (GO)/HA composite ceramic scaffolds using digital light processing (DLP) technology. The properties of the composite ceramic slurry and the process parameters of curing, degreasing, and sintering were initially examined to ensure molding accuracy. The research showed that a small amount of GO (0.1–0.4 wt%) could better maintain the pore structure and improve the mechanical properties of composite ceramics. Porous scaffolds with pore sizes of 300–400 μm were prepared for co-culture with rat bone marrow mesenchymal stem cells to detect biocompatibility. The results showed that all scaffolds have no cytotoxicity. Compared with HA, the GO/HA ceramic scaffold significantly promoted the cell adhesion, proliferation, and expression of osteogenesis-related genes; GO (0.1–0.2 wt%) /HA scaffolds exhibited superior alkaline phosphatase activity and more effective bone mineralization, showing enhanced osteoinductivity. The porous GO/HA composite scaffold fabricated by DLP presented a strong potential for repairing bone defects. [ABSTRACT FROM AUTHOR]

In this work, tailored Mn–Zn ferrite ceramics are prepared by stereolithography (SLA) 3D printing technology, and its performances are measured utilizing the printing accuracy, magnetic properties, density, and microstructures. The major obstacle forming difficultly by single curing of self-made ferrite pastes with increasing solid content in the printing process is removed by using six scanning numbers. In addition, the prediction formulas of the linewidth and curing depth are established. The printing process parameters, namely scanning space, scanning speed, and laser power, are optimized at 2 μm, 2500 mm/s, and 240 mW, respectively. The size of convex platform bigger than 1 mm × 1.2 mm possessing circular and square holes with a diameter and a side length of 0.2 mm can be printed using the printing process parameters above. Specifically, the sintering temperature and holding time below 1200 °C and 90 min, respectively, are optimized conducive limits. The sintered parts show a density of 4.04 g/cm3 and a saturation magnetization of 58.6 emu/g, along with a small value of coercivity and remanence. The SLA-3D printing, debinding, and sintering technologies can print the complex shapes Mn–Zn ferrite ceramics using the proposed process. [ABSTRACT FROM AUTHOR]

To prevent the agglomeration of silicon carbide whiskers (SiC w) in photosensitive ceramic paste, a butanone-ethanol azeotropic solvent is employed to facilitate the dispersion of alumina particles, SiC whiskers and UV resins. Moreover, SiC w /Al 2 O 3 ceramic pastes, with 5–15 vol % SiC w , are prepared by using ball milling, stirring and distillation processes. The mixture of butanone-ethanol solvent and resins can be effectively separated at 70 °C without weakening the polymerization of UV resin. Moreover, an empirical equation is established to evaluate the relationship between SiC w content, aspect ratio and viscosity of resulting ceramic paste. The 15 vol % SiC w /Al 2 O 3 composite ceramic, with SiC w aspect ratio of 50, renders higher resistance to liquid flow and results in a high viscosity of 30,000 mPa s at the shear rate of 30 s−1. Furthermore, a modified equation is established to predicate the curing depth of ceramic pastes with different amounts of SiC w , where 15 vol % SiC w /Al 2 O 3 composite results in higher light scattering properties, leading to lowest C d of ∼0.061 mm. Finally, the complex-shaped SiC w /Al 2 O 3 ceramic component, prepared by SL 3D printing technology, debinding and sintering processes, exhibited a superior fracture toughness of 7.1 ± 1.20 MPa m1/2 and a higher hardness of 17.6 ± 0.78 GPa. • A novel technology was proposed for preparing a 50 vol% SiC w /Al 2 O 3 photosensitive paste. • The dispersing process can effectively prevent the agglomeration of SiC whiskers. • 5-15 vol% SiC w contents influence on the pastes corresponding properties were evaluated. • Complex SiC w /Al 2 O 3 part with 7.1 ± 1.20 MPa m1/2 was 3D printed and sintered. [ABSTRACT FROM AUTHOR]

Optically driving liquid crystal display (ODLCD) uses polarized light field to control the orientation of the liquid crystal, and the display content can be maintained without external electric field, with extremely low power consumption. However, it has a long rewriting time, which is difficult to achieve industrialization. In order to improve the rewriting performance, the influence of the rotational viscosity of the mixed system of azo-dyes (SD1, MR) and nematic liquid crystal (5CB) on the rewriting speed is investigated. The experimental results show that the electro-optical properties of SD1-5CB and MR-5CB have great changes after irradiation by polarized light, among which the SD1-5CB is the best to improve the performance. With the increase of SD1 concentration, the rotational viscosity of SD1-5CB decreases significantly due to the change of cis-trans isomerization of azo-dye, and the optimal doping concentration is 0.5 wt%. In this case, the rewriting time is shortened from 45 s to 11 s, which has the potential to broaden the application of ODLCD. [ABSTRACT FROM AUTHOR]

In this paper, the UV curable ZrO 2 -Al 2 O 3 composite ceramic pastes based on SLA-3D printing technology were synthetized firstly, and the corresponding ceramic green bodies were 3D printed, and finally the ZrO 2 -Al 2 O 3 composite ceramic parts were manufactured by a subsequent debinding and sintering process. Our work focuses on the investigation of the microstructure, hardness and fracture toughness of the printed ZrO 2 -Al 2 O 3 composite ceramics sintered at different maximum sintering temperature and holding time. In case of the sintering temperature of 1500 °C and holding time of 60 min, the actual density, hardness and fracture toughness of the ceramics can reach 3.75 g/cm3, 14.1 GPa and 4.05 MPa⋅m1/2, respectively. If the sintering temperature is higher than 1500 °C, the abnormal grain growth can occur, resulting in some more reductions in the mechanical properties of ceramics; while when the sintering temperature is lower than 1500 °C, the lower driving force makes the grains not fully developed, resulting in a low density of ceramics and worse mechanical properties. With the increase of holding time, the sintering driving force is promoted, making for the grain growth. However, when holding time is more than 60 min, the actual density of ceramics almost remains unchanged, and the mechanical properties of ceramics are not able to be improved further. [ABSTRACT FROM AUTHOR]

Stereolithography (SLA) is a commonly used ceramic 3D printing technology which is capable of accurate and industrial production. Based on this technology, ZrO 2 ceramics were prepared using different laser power in the presented work. The forming capability of laser on the printed sample at three-dimensional directions was investigated by combining the Gauss beam and Beer-Lambert model. Besides, the dimension variety and shrinkage after printing, debinding, and sintering were studied, and the scaling factors were further determined. The dimension shrinkage of the stratified surface outnumbers that of the laser scanned surface. Therefore, the printing direction has a significant influence on the dimensional accuracy. The weight, density, and porosity of the designed ceramics using different laser power were analyzed as well. It was found that the weight of parts after the debinding process can be reduced by 97.6% of the total deduction of the weight, while the density of parts in sintering process was increased by 86.9% of the total increase of the density. It should be highlighted that the ZrO 2 ceramic gears and integrated bearing with the relative density of 97%, hardness of 13.1 GPa, fracture toughness of 5.62 MPa·m1/2, and flexural strength of 1044 MPa, were obtained using the optimum laser power of 360 mW. [ABSTRACT FROM AUTHOR]

Based on the traditional structure of in plane switching liquid crystal display, a cylindrical liquid crystal micro-lens array driven by interdigital electrodes is proposed, and its performance is studied. Firstly, the director distribution and relative phase difference distribution of liquid crystal molecules were calculated, which shows that this structure can be used to fabricate cylindrical liquid crystal micro-lens. Then, by comparing lenses of difference sizes, it is found that narrow electrodes should be selected for lens production, and the centre of the electrode gap should be selected as the central axis of a single liquid crystal micro-lens. Finally, a certain electrode structure is selected to explore its focal length, focusing quality and zoom time. The results show that the focal length of the liquid crystal micro-lens decreases gradually with the increase of the driving voltage. When the driving voltage is between 3 Vrms and 5.5 Vrms, the liquid crystal micro-lens has good focusing quality, and its corresponding focal length changes from 1.63 mm to 20.28 mm. Based on this structure, when the liquid crystal lens is driven by the above two voltages alternately, the time required for liquid crystal molecules to reach stability is 2.35 s and 3.87 s respectively. [ABSTRACT FROM AUTHOR]

The image sticking of the liquid crystal display (LCD) is related to the residual direct current voltage (RDCV) on the liquid crystal cell. The saturated residual DC voltage (SRDCV) can be obtained by analyzing the change of the capacitance of the liquid crystal cell under the application of DC bias (DCB), thus the LCD image sticking can be evaluated. Based on this, we evaluated the image sticking of the hybrid aligned nematic (HAN) liquid crystal display (HAN-LCD) with four different alignment layer materials (KPI-300B, PIA-2710, RV-961G, SE-4811(0526)) combinations of infused liquid crystal materials with negative dielectric anisotropy, from which the effect of the alignment layer material on image sticking was analyzed. The experiment found that the SRDCV measured by the HAN cell with vertical PI model SE-4811(0526) and parallel PI model PIA-2710 is the minimum under positive and negative DCB. The results show that the alignment layer material can greatly affect the image sticking problem of HAN-LCD, and provide useful guidance for improving its display quality. [ABSTRACT FROM AUTHOR]

In this paper, a highly sensitive and transparent flexible temperature sensor fabricated from the polyethylene terephthalate flexible substrate and the nematic liquid crystal (1M0921900-000) is proposed, which simultaneously has low power consumption. Using the relaxation time (τ = RC) as an intrinsic variable to characterise temperature, a better linear fitting with temperature can be obtained at low voltage, high precision and more stable temperature monitoring can be achieved. The maximum sensitivity is −4.05%/°C at 0.1 V and 200 Hz. The transmittance of the sensor can reach 62.36–81.13% in the visible light range. Compared with the rigid liquid crystal temperature sensor, the rise time and the decay time of the sensor are reduced by 97.104% and 90.313%, respectively. In addition, it also has good stability, recovery, and durability, which shows potential applicability to electronic skin, prostheses, robots, and biomedical by accurately monitoring the change of external temperature. [ABSTRACT FROM AUTHOR]

The voltage-controlled twist (VCT) effect shows that a grating surface, with its particular anchoring properties, has the potential to become a new surface anchoring for liquid crystal devices. In order to describe these properties an equivalent anchoring energy is introduced. The alignment of a nematic liquid crystal (NLC) on such a grating originates from two mechanisms, so each produces a term in the equivalent anchoring energy. One is the interaction potential between NLC molecules and the molecules on the substrate surface, from which we derive the expression of the corresponding term. The other is the increased elastic strain energy, for which we adopt the result of Berreman. The equivalent anchoring energy obtained is a function of pitch λ and amplitude δ of the grating surface. Both the corresponding strength parameter and the easy direction are functions of λ and δ. The hybrid aligned nematic cell proposed by. Bryan-Brown et al. is studied by the use of our formula, and the distribution of the director, the saturation state and the saturation voltage are calculated in detail. The results are consistent with experimental data, especially the values of λ and δ. The VCT effect can therefore be explained. [ABSTRACT FROM AUTHOR]

In order to explore the stability of a liquid crystal (LC) system doped with γ-Fe2O3 nanoparticles, the physical properties (clearing point, dielectric properties), electro-optical properties and residual direct-current voltage (RDCV) of the doped LC system were measured and evaluated at different times. First, the temperature was controlled by precision hot stage, and the clearing point temperature of doped LC was observed and measured by a polarized optical microscope. Using a precision LCR meter, we measured the capacitance-voltage curves of the doped LC system at the temperature of 27 °C. The dielectric constant of doped LC was calculated by the dualcell capacitance method. Then, the electro-optical properties of the doped LC system were measured. Finally, the RDCV of the doped LC system was measured and calculated. After five months, the parameters of the doped LC system were re-measured and analyzed under the same conditions to evaluate its stability. The experimental results show that, within five months, the clearing point change rate of doped LC is in the range of 0.24%–1.37%, the change of dielectric anisotropy is in the range of 0.035–0.2, the curves of electro-optical properties are basically fitted, and the change rate of saturated RDCV is about 11.2%, which basically indicate that the LC system doped with γ-Fe2O3 nanoparticles has good stability. [ABSTRACT FROM AUTHOR]

The orientation of Nematic liquid crystal (NLC) and order degree of LC molecules are easily affected by ambient temperature, so it is of great significance to explore the low-temperature properties of NLC materials to improve the low-temperature performance of LC devices. The dielectric and elastic constant of the NLC material 1M10500-000 under the high and low-temperature conditions were obtained by the dual-cell capacitance method, linear fitting method and numerical fitting, and were compared. The dynamic response of the NLC at different temperatures was tested, and the rotational viscosity was calculated. The experimental results show that the dielectric constant is still proportional to the order parameter at low temperature. The elastic constants k11 and k33 and the square of order parameter no longer conform to the proportional relationship at low temperature, and the lower the temperature, the greater the deviation of elastic constants from the proportional relationship. As the temperature decreases, the ratio of k33/k11 changes from 2.62 to 2.71, and the rotational viscosity coefficient changes from 5.66 mPa.s to 177.64 mPa.s. Finally, the transient hysteresis phenomenon at low temperature was proposed and explained by the residual direct current voltage. [ABSTRACT FROM AUTHOR]

The thermistor was fabricated by filling the nematic liquid crystal (NLC) material IM95100-000 into a liquid crystal device with an interdigital electrode structure. In the temperature range of 25 °C–120 °C, the temperature response of the thermistor under different voltages was measured with a step length of 5 °C to study its performance. The experimental results show that the resistance value of the thermistor decreases exponentially with increasing temperature in the range of 25 °C–120 °C. The temperature resistance characteristics at different voltages can satisfy the Steinhart-Hart formula well and the nonlinear fitting coefficient can reach 0.999; under the voltage of 1 V, the total resistance percentage changes by 93.1%, the material constant B25-120 value can reach 3299.07 K, and the temperature coefficient of resistance (TCR) can reach 0.98%/K. As a temperature sensor, it is twice as sensitive as that without the interpolated electrode structure, and the sensitivity can be further improved as the temperature decreases. Through the stability and recovery measurements, it is found that the resistance has no obvious deviation, which verifies the possibility of long-term application of this thermistor. [ABSTRACT FROM AUTHOR]

Temperature monitoring plays an increasingly important role in research and industrial applications. Based on the influence of liquid crystal material thermal sensitivity on the capacitance of liquid crystal cell, the sensing performance of the capacitive-type liquid crystal temperature sensor were studied. By testing the capacitance under the voltage from 0 V to 20 V at different temperatures, the capacitance–voltage curve is drawn, and then the relationship between the capacitance change rate and the temperature at different voltages was obtained, so as to analyse its sensitivity. The results show that the capacitance of the liquid crystal material (RDP-09 T-100) is linearly related to the temperature in the temperature range of 20–110°C, even when the applied voltage is 0.1 V, which proves its feasibility as a temperature measuring medium for the temperature sensor and shows that the sensor has the advantage of low power consumption. When the applied voltage is 15 V, the sensitivity of the capacitive-type liquid crystal temperature sensor can reach 0.94 pF/°C and its response time is 0.115 s/(pF.°C). This research further expands the application scope of liquid crystal and has certain guiding significance for the development of new temperature sensor. [ABSTRACT FROM AUTHOR]

Ceramic stereolithography Three-Dimensional (SL-3D) printing has a unique advantage in forming ceramic parts with complex shapes. However, because of the effects of the slicing layer thickness, laser spot diameter, and curing inhomogeneity, its manufacturing dimensional accuracy still lags far behind traditional processing methods. In this study, a manufacturing process based on additive and subtractive technologies was used to prepare ceramic groove parts. The manufacturing process of ceramic groove parts is composed of SL-3D printing, debinding, micro-milling, and sintering processes. In order to improve the dimensional accuracy of ceramic groove parts, a model based on shrinkage compensation and micro-milling was proposed. The dimensional change pattern in the curing phase was modelled and a shrinkage compensation method was established to control the dimensional accuracy of the finished parts. A method to characterize the micro-chipping on machined edges of the workpiece was investigated by applying a micro-milling cutter to process the 3D-printed part pre-sintered at 1150 °C. The effectiveness of the proposed dimensional accuracy control method was verified by the case study of a ZrO 2 ceramic part. [ABSTRACT FROM AUTHOR]

In order to accurately determine the pre-tilt angle, we proposed a systematic method by combining optical and electrical measurement. First, the pre-tilt angles of the parallel and vertical aligned nematic liquid crystal (LC) cell with a large thickness (>10 μm) were measured by the crystal rotation method. Then, the material parameters of E7, including the dielectric constant and the splay and bend elastic constant, were obtained by using the dual-cell capacitance model and comparing the capacitance-voltage (C-U) curves of the thick cells. Finally, the pre-tilt angles of two thin LC cells to be tested were determined by theoretical and experimental fitting of their normalised C-U curve, which are 1.80°±0.04° and 3.50°±0.02°, respectively. Our method not only has relatively high accuracy, but also is not limited by the thickness and mode of LC cell. [ABSTRACT FROM AUTHOR]

Rotational viscosity coefficient is an important material parameter affecting the dynamic response of liquid crystals. We evaluated the dynamic response of two series of mixed liquid crystals SCL17V33L00 and SCL17V28L00 with negative dielectric anisotropy on the basis of the accurate measurement of rotational viscosity. At the temperature of 25°C, 30°C and 35°C, the parallel and vertical dielectric constants of them were calculated from the dual-cell capacitance model and liquid crystal cell capacitance model. Then, the bend and splay elastic constants of them were determined by analysing the Fréedericksz transition threshold voltage in the vertically aligned nematic cell and comparing the liquid crystal layer capacitance–voltage curve through the finite-differential iteration method with experimental curve. At last, the rotational viscosity coefficients γ1 of them were obtained by performing dynamic response simulation using Visual Fortran software. As the temperature increases, the rotational viscosity coefficient of them decreases. Although the rotational viscosity coefficient of the second mixed liquid crystal was relatively large under the same temperature, the viscoelastic ratio coefficient was small, and the figure-of-merit was large, thereby resulting in a relatively fast dynamic response. [ABSTRACT FROM AUTHOR]

The dynamic response property of liquid crystal (LC) devices mainly depends on the selection of LC materials and driving method of the devices. In this work, we explored the modulation of the dynamic response property of LC mixtures through the microscopic mechanism and macroscopic method of γ-Fe2O3 nanoparticle doping and driving mode adjustment, respectively. LC mixtures doped with different concentrations of γ-Fe2O3 nanoparticles retained the dielectric and elastic properties of the LC state and good temperature stability. In addition, doped LC mixtures had lower threshold voltage, higher birefringence, and faster rise and decay times than pure LC materials. Besides, the application of voltage overdriving and undershooting methods could reduce the rise and decay times of LC mixtures by 74.8% and 21.7%, respectively. Moreover, the combined methods of γ-Fe2O3 nanoparticle doping and voltage overdriving and undershooting decreased the total response time of LC mixtures by 71.5%, and the response speed of doped LC mixtures increased by 3-fold relative to that of the pure LC materials. [ABSTRACT FROM AUTHOR]

The energy density distribution directly affects the molten-pool temperature gradient, cooling and solidification rate of additive manufacturing (AM), which in turn affects the mechanical properties and microstructure of samples. In this paper, the control of the Gaussian laser beam energy density distribution characteristics is realized by controlling the defocus amount. The influence of the energy density distribution characteristics on the macro/micro structure and mechanical properties of the sample is explored. Microstructure observation and electron backscatter diffraction (EBSD) test were observed. The porosity, microhardness, tensile property, and friction of the samples were tested. These results indicated that when the beam energy density distribution was relatively uniform, the sample structure was most closely arranged equiaxed crystals. The grain size and texture strength of the samples gradually decreased, and the minimum grain size was 30.1 µm. With the energy density distribution becoming uniform, the microhardness and tensile strength first raised and fell, and the porosity and wear rate first fell and raised. The highest tensile strength was 1328 Mpa, and the smallest porosity was 0.31%. In addition, the mapping relationship between the defocus amount and the energy density distribution was deduced theoretically. Finally, combining the fine-grain strengthening and geometry necessary dislocation (GND) density, the mechanism of the effect of texture on the performance was revealed. The present work demonstrates the effectiveness of adjusting the defocus amount to control the beam energy density distribution, which in turn can effectively improve the properties of AMed metals. [Display omitted] • Validity of defocus amount to improve laser energy distribution was proved. • The improved Gaussian beam had low temperature gradient characteristics. • The improved beam effectively improved the microstructure of AM GH3625. • The improved beam availably improved the mechanical properties of AM GH3625. [ABSTRACT FROM AUTHOR]

The dielectric and elastic properties of liquid crystals (LCs) generally depend on the molecule structure, such as polar group and carbon chain length. For further investigation of the influence of molecular structure on the dielectric and elastic properties of fluorine-containing tricyclic isothiocyanate LC, the experimental temperature was controlled at 25°C by precision hot stage, and a precision LCR meter was used to measure the capacitance of six LC cells under the voltage from 0.1 to 20 V at 1 kHz. An LC cell capacitance model and a dual-cell model were adopted to obtain the dielectric anisotropy, and the capacitance–voltage curves of six LC materials were plotted. The threshold voltage of Fréedericksz transition was analysed, and a finite difference iterative method was used to attain specific values of three elastic constants. The influence of molecular structure on the dielectric and elastic constants was finally analysed. Experimental results showed that the introduction of meta-difluoro group would increase the dielectric anisotropy and reduce the threshold voltage of LC. As the length of the alkyl carbon chain increased, the dielectric anisotropy would have an odd–even alternation effect, which would lead to changes in the elastic constants of LC. [ABSTRACT FROM AUTHOR]

In this study, the twist elastic constant (k22) of liquid crystals (LCs) was accurately measured using capacitance method. The constant can be obtained on the basis of accurate measurement of other LC parameters, such as parallel and vertical dielectric constants (ε// and ε⊥), splay and bend elastic constants (k11 and k33), and rotational viscosity coefficient (γ1). First, by using dual-cell capacitance method and an LC cell capacitance model to measure ε// and ε⊥, k11 and k33 can be obtained from the threshold voltage determined from the voltage-capacitance curve of the parallel-aligned nematic LC layer and the comparison between the experimental and theoretical results based on the Frank elastic theory, respectively. In addition, γ1 can be obtained from the measurement of the dynamic response in the parallel-aligned nematic cell. Finally, k22 can be accurately determined using the threshold voltage of the twisted nematic LC cell. By adopting the above method, the measured k22 for LC E7 was 6.7 × 10−12 N. The proposed method is more rigorous and yields a more accurate measurement result than the other methods reported in the literature. [ABSTRACT FROM AUTHOR]

According to performance demands of tool materials for high speed machining difficult to cut materials, gradient cermet composite tool materials were designed and fabricated based on hot pressing sintering after dry pressing. The gradient cermet composite tool materials were composed of surface layer, subsurface layer and substrate and exhibited gradient microstructure and mechanical properties. The surface layer had a high hardness, subsurface layer had a high bonding strength and substrate had a high flexural strength. Three gradient composite cutting inserts were fabricated with the gradient structure on different tool faces. To evaluate the cutting performance of gradient cermet composite cutting inserts, effects of cutting speeds on the tool life and surface roughness were investigated during continuously dry turning 17-4 PH stainless steel. The developed gradient cermet composite cutting inserts showed longer tool life and better machining quality than conventional Ti(C,N) cermet inserts under the same cutting conditions. Cutting speeds played a significant effect on both tool life and failure mode of cutting inserts. The favorable cutting performance of gradient cermet composite cutting inserts was attributed to high surface hardness, good wear resistance of surface layer and reasonable gradient structure. [ABSTRACT FROM AUTHOR]

Image sticking in thin film transistor-liquid crystal displays (TFT-LCD) is related to the dielectric property of liquid crystal (LC) material. Low threshold value TFT LC materials have a weak stability and the free ions in them will be increased because of their own decomposition. In this study, the property of TFT LC material MAT-09-1284 doped with γ -Fe2O3 nanoparticles was investigated. The capacitances of parallel-aligned nematic LC cells and vertically aligned nematic LC cells with different doping concentrations were measured at different temperatures and frequencies. The dielectric constants perpendicular and parallel to long axis of the LC molecules ε⊥ and ε//, as well as the dielectric anisotropy Δε, were obtained. The dynamic responses and the direct current threshold voltages in parallel-aligned nematic LC cells for different doping concentrations were also measured. Although the dielectric anisotropy Δε decreased gradually with increasing temperature and frequency at the certain frequency and temperature in LC state for each concentration, the doping concentration of γ -Fe2O3 nanoparticles less than or equal to 0.145 wt % should be selected for maintaining dynamic response and decreasing free ions. This study has some guiding significance for improving the image sticking in TFT-LCD. [ABSTRACT FROM AUTHOR]

• For the first time, we have produced flexible 1D and 2D PDLC gratings using liquid crystals and polymers. • The transmittance and rise and decay time of flexible PDLC gratings don't change with the radius of curvature. • Flexible 1D and 2D PDLC gratings have the advantage of fast response and low driving voltage. Liquid crystal (LC) materials have dielectric and optical anisotropy and are candidates for the preparation of electrically controlled tunable diffraction gratings. Flexible LC gratings have the advantages of high flexibility, light weight, small size, and attachability. At present, the electronically controllable flexible LC grating needs to be further studied. In this paper, polymer-dispersed liquid crystal (PDLC) is poured into the flexible cell made of ITO-PET, and 1D and 2D flexible PDLC gratings are prepared by the method of polymer-induced phase separation. It can realize the modulation of the grating diffraction order through an external electric field under different curvature radii, and it also has the characteristics of the low driving voltage, low saturation voltage, and fast response. The driving voltage and saturation voltage of the 1D flexible PDLC grating are 0.8 V and 12 V, the cell thickness is 5.2 μm, and the rise and decay times are 3.225 ms and 98.29 ms, respectively, the first-order diffraction efficiency at the center is 9.1%. For the 2D flexible PDLC grating, the driving voltage and saturation voltage are 2.5 V and 16.5 V, the cell thickness is 5.2 μm, the rise and decay times are 3.362 ms and 75.46 ms, respectively, the first-order diffraction efficiency at the center is 7.58%. [ABSTRACT FROM AUTHOR]

The production of graded cubic boron nitride (cBN) tool materials starting with cBN-TiC-Al-Co mixture and having a three-layer symmetrical graded structure were obtained by high temperature high pressure method. In the first part, the design model which proposed a component gradient of cBN varied from 4 vol% to 10 vol% accompanied with Al and Co varied from 2 vol% to 5 vol% between the surface and interior was presented. Afterwards, the rationality of the graded structures were verified by the thermal residual stress analysis in the composites. In the second part, the relationships between the mechanical properties and the thickness ratio, sintering temperature, holding time as well as the component gradient were investigated. The significant gradients of the elements of Al and Co were detected in the graded cBN composites. When the temperature converted from 1350 °C to 1550 °C, the liquid phase sintering and reaction process were confirmed, leading to the formation of AlN, AlB 2 and Co 2 B. The excellent samples with a thickness ratio of 0.3 and a cBN gradient of 6 vol% acquired a homogeneous microstructure with no obvious defects under a pressure of 5.8 GPa at 1500 °Cfor 10 min. The optimum mechanical properties were achieved a flexural strength of 710 MPa and a hardness of 36.5 GPa, which was higher than that of the monolithic material with a cBN content of 80 vol%. The crack deflection and bridging played the main role in the toughening mechanism, reflecting a significant contribution of the residual stress to the mechanical properties. • The graded structure was introduced to the cBN cutting tool material to improve the strength and toughness, acquiring a flexural strength of 710 MPa and a hardness of 36.5 GPa. • The residual stress induced by the graded structure was the main toughening and strengthening mechanism, characterized by crack bridging and deflection. [ABSTRACT FROM AUTHOR]

Improving image sticking in liquid crystal display (LCD) has attracted tremendous interest because of its potential to enhance the quality of the display image. Here, we proposed a method to evaluate the residual direct current (DC) voltage by varying liquid crystal (LC) cell capacitance under the combined action of alternating current (AC) and DC signals. This method was then used to study the improvement of image sticking by doping γ-Fe2O3 nanoparticles into LC materials and adjusting the friction torque difference of the upper and lower substrates. Detailed analysis and comparison of residual characteristics for LC materials with different doping concentrations revealed that the LC material, added with 0.02 wt% γ-Fe2O3 nanoparticles, can absorb the majority of free ions stably, thereby reducing the residual DC voltage and extending the time to reach the saturated state. The physical properties of the LC materials were enhanced by the addition of a small amount of nanoparticles and the response time of doping 0.02 wt% γ-Fe2O3 nanoparticles was about 10% faster than that of pure LC. Furthermore, the lower absolute value of the friction torque difference between the upper and lower substrates contributed to the reduction of the residual DC voltage induced by ion adsorption in the LC cell under the same conditions. To promote the image quality of different display frames in the switching process, we added small amounts of the nanoparticles to the LC materials and controlled friction technology accurately to ensure the same torque. Both approaches were proven to be highly feasible. [ABSTRACT FROM AUTHOR]